Open Collections

UBC Theses and Dissertations

UBC Theses Logo

UBC Theses and Dissertations

The effect of varying air supply upon supernatant quality in autoheated thermophilic aerobic digesters… Boulanger, Mary Louise 1994

Your browser doesn't seem to have a PDF viewer, please download the PDF to view this item.

Item Metadata

Download

Media
831-ubc_1995-0186.pdf [ 13.64MB ]
Metadata
JSON: 831-1.0050409.json
JSON-LD: 831-1.0050409-ld.json
RDF/XML (Pretty): 831-1.0050409-rdf.xml
RDF/JSON: 831-1.0050409-rdf.json
Turtle: 831-1.0050409-turtle.txt
N-Triples: 831-1.0050409-rdf-ntriples.txt
Original Record: 831-1.0050409-source.json
Full Text
831-1.0050409-fulltext.txt
Citation
831-1.0050409.ris

Full Text

THE EFFECT OF VARYING AIR SUPPLY UPON SUPERNATANT QUALITY IN AUTOHEATED THERMOPHILIC AEROBIC DIGESTERS TREATING WASTE SLUDGE FROM A BIOLOGICAL PHOSPHORUS REMOVAL PROCESS by MARY LOUISE BOULANGER B.A.Sc, The University of British Columbia, 1987  A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTS FOR THE DEGREE OF MASTERS OF APPLIED SCIENCE in THE FACULTY OF GRADUATE STUDIES (Department of Civil Engineering)  We accept this thesis as conforming to the required standard  THE UNIVERSITY OF BRITISH COLUMBIA April 1995 © Mary Louise Boulanger, 1994  In  presenting  degree freely  this  thesis  in  partial  fulfilment  at t h e U n i v e r s i t y  of  British  Columbia,  available  copying  of  department publication  f o r reference  this or of  thesis by  this  for  his  or  thesis  a n d study. scholarly her  of I  I further  purposes  gain  shall  permission.  Department  of -  Cw'V/j  T h e U n i v e r s i t y o f British Vancouver, Canada  /\U/ . >  Date  DE-6  (2/88)  ^rt&UsyiJ?<7  Columbia  agree  s~js?  requirements that  agree  may be  representatives.  f o r financial  the  It  is  that  t h e Library permission  granted  by  understood  not be  for  allowed  an  advanced  shall for  make  extensive  the head that  without  it  of  my  copying  or  my  written  ABSTRACT  Return flowsfromsludge stabilization processes can have a significant impact on overall plant design. This is especially true for biological phosphorus removal (Bio-P) processes, because high phosphorus levels in return supernatant can defeat the purpose of the process. Previous research determined that excess stored phosphorus in Bio-P waste sludge is released to solution under both mesophilic aerobic and anaerobic digestion conditions. This research investigated thermophilic aerobic digestion (commonly referred to as ATAD) of Bio-P waste sludge, to determine the extent of phosphorus release. Because dissolved oxygen conditions affect the release and uptake of phosphorus in Bio-P treatment, the effect of different aeration levels on phosphorus release and general supernatant quality was also studied. Phosphorus (P) release in ATADs was of special interest because field results indicated that these types of digesters were capable of generating high concentrations of the volatile fatty acids (VFA's) required to drive the phosphorus storage mechanism in Bio-P plants. Two 72 liter pilot scale ATADs were used, operating in series with a 6 day total retention time. The sludge feed was an average combination, in terms of VS, of 44 percent primary sludge and 56 percent Bio-P waste activated secondary sludge. The digesters were operated in batch mode on a 24 hour cycle. The temperature in ATAD 1 varied between 35 and 56 °C, and the temperature in ATAD 2 varied between 55 and 64 °C. Average influent volatile solids concentrations varied between 16600 and 18400 mg/L. Three aeration conditions were defined by on-line monitoring of oxidation reduction potential (ORP) and dissolved oxygen concentration (DO). The condition with the lowest airflow rate was labelled "oxygen deprived", and was characterized by ORP generally less than -300 mV and DO concentrations generally less than 1 mg/L in both digesters . The condition with a medium airflow rate was labelled "oxygen satisfied", because ORP was above +100 mV and DO was greater than 1 mg/L by the end of the 24 hour cycle in ATAD 1, and conditions were always aerobic in ATAD 2. The condition with the highest airflow rate was labelled "oxygen excess", because ORP was generally higher than +100 mV and DO was generally greater than 1 mg/L in both digesters. Phosphorus and nitrogen balances were done for each aeration condition, and solids balances ii  were done for the oxygen deprived and the oxygen excess conditions. Other parameters measured were total and soluble COD, volatile fatty acids, pH, and alkalinity. Results indicated that total VS reduction was the same for both the oxygen deprived and the oxygen excess conditions. A comparison of influent and effluent total COD concentration confirmed that overall sludge stabilization in ATADs was not affected by airflow rate within the range studied. Total VS reduction in thefirstdigester in the series was similar to that predicted by the EPA Design Curve for aerobic digesters. Although total VS and COD reduction was not affected by airflow rate, the proportion of soluble COD increased with decreasing airflow and the concentration of acetic acid was greater in the oxygen deprived experiment than with the higher airflow rates. Dissolved nitrogen also increased with decreasing airflow. Supernatant quality thus generally declined with decreasing airflow. The least amount of phosphorus released occurred under the oxygen satisfied condition, which was characterized by alternate low ORP and high ORP conditions in ATAD 1. The greatest amount of phosphorus release occurred under the oxygen deprived condition. In all cases, the concentration of phosphorus in the supernatant would be of concern if that supernatant was returned to the influent of a Bio-P treatment process.  iii  TABLE OF CONTENTS  Abstract  ii  Table of Contents  iv  List of Tables  vi  List of Figures  viii  Acknowledgements  xi  Chapter One  Introduction  1  Chapter Two  Background Effect of Supernatant Recycling on Sewage Treatment Plant Design Biological Phosphorus Removal Handling Bio-P Waste Activated Sludge  4 4 8 13  Chapter Three  Autothermal Thennophitic Aerobic Digestion Technology Development Operating Conditions ATAD Supernatant Quality  19 19 29 43  Chapter Four  Experiment Design Objectives Apparatus Experimental Methods Sampling and Sample Preservation Laboratory Analysis and Discussion of Method Error  51 51 51 65 68 72  Chapter Five  Results and Discussion Operating Conditions Three Aeration States Supernatant Quality Full Scale Implications of Experimental Results  88 88 106 130 152  Chapter Six  Conclusions and Recommendations Conclusions Recommendations  157 157 158  Bibliography  160  Appendix 1  Data  169  Appendix 2  Balance Calculations and Balance Errors iv  212  Appendix 3  Temperature IncreasefromMechanical Mixing in Water Filled Pilot Scale ATADs  223  Appendix 4  Aeration Testing  230  Appendix 5  Calculation of Phosphorus Release Due to Sample Acidification  Appendix 6  Recycle Calculations  Appendix 7  ORP and DO Trace Patterns  236  245  v  253  LIST OF TABLES  TABLE  TITLE OF TABLE  NO.  PAGE NO.  1  Mesophilic Aerobic Digester Supernatant Characteristics  5  2  Mesophilic Anaerobic Digester Supernatant Characteristics  6  3  Full Scale ATAD Average Operating Temperatures and Mixing Energy Input ,  32  4  Full Scale ATAD Solids Design Values  35  5  ATAD pH Reported in Research Literature  41  6  Full Scale ATAD Alkalinity and pH  42  7  Nitrates Measured in U-Shaped Bioreactor  46  8  Volatile Fatty Acids Measured in Salmon Arm ATADs  9  Supernatant Solids Check  10  Maximum Expected Errors in Dissolved PfromSample Acidification  11  Standard Recovery  78  12  Pilot Scale ATAD Temperatures  89  13  Actual Average Daily Maximum Temperature Compared to Predicted  48 76 76  Maximum Temperature  93  14  Volume Balance Summary  95  15  Solids Retention Times  96  16  Average Influent Mixed Sludge Solids Concentrations  17  Solids Loadings  99  18  Non-Volatile Solids Balances  100  19  Percent Volatile Solids Reduction  100  20  Temperature-Detention Time Products  102  21  Average ATAD Sludge Solids Concentrations  103  22  Measured Specific Oxygen Uptake Rate  106  vi  98  23  Average Oxygen Supplied/VS load  24  ATAD Discharge Gas and Air Supply Quality - Percent by Volume  25  ATAD Discharge Gas and Air Supply Quality - Moles of Three Constituent Gases  108 110 110  26  Oxygen Transfer Efficiency  111  27  Alkalinity  127  28  ATAD pH  129  29  Total Chemical Oxygen Demand and Percent COD Reduction  30  Soluble Chemical Oxygen Demand  31  Average COD Concentration due to VFA  137  32  Average Influent Nitrogen Concentrations in Influent Thickened Sludge  139  33  Nitrogen Mass Balance  140  34  ATAD Average Nitrogen Concentrations  142  35  Influent Mixed Sludge Phosphorus Concentrations  147  36  Total Phosphorus Mass Balance  148  37  ATAD Average Phosphorus Concentrations  148  38  Total Suspended P as Percent of Volatile Suspended Solids  39  Estimated Effect of ATAD Supernatant Recycle On Influent Flow Concentrations and Loads  130 132  149 154  vii  LIST OF FIGURES FIGURE NO.  Title of Figure  PAGE NO.  1  Mechanism of Poly-P Storage and Release (Toerien et al., 1990)  11  2  The Phostrip Process (Matsch and Drnevich, 1978)  14  3  Reaction Rate Constant as a Function of Temperature (Kambdu and Andrews, 1969)  4  21  Scanning Electron Micrograph of Thermophilic Organisms and Feed Yeast Cells (Mason et al., 1987a)  22  5  Heat Balance for an Autoheated Thermophilic Aerobic Digester  23  6  Types of ATAD Aeration Systems  25  7  Gemmingen Temperature Curves (EPA, 1990)  30  8  Eichbactel Daily Tenmerature Curve (Schwinning et al., 1993)  31  9  The Effect of Biodegradeable Organic Loading Rate on Organic Removal Rate (Jewell and Kabrick, 1980)  10  34  Respiration Rate of Mixed Liquor in a Single Stage ATAD System (EPA, 1990)  36  11  ATAD Oxygen Uptake Rate Over One Feed Cycle (Bomio, 1989)  37  12  Relationship of Oxidation-Reduction Potential to Aeration State (Kelly, 1990)  13  40  Changes in pH, Dissolved Oxygen, Solids and Dissolved Organic Carbon Concentrations with Time (Hamer, 1987)  42  14  Anoxic/Aerobic Sludge Digestion (Peddie and Mavinic, 1988)  45  15  Changes in Volatile Fatty Acid Concentrations in an ATAD with Time Compared to ORP Trace Patterns (Chu et al., 1994)  49  16  Primary Sludge Thickening System Schematic  53  17  Secondary Sludge TMckening System Schematic  55  18  Gravity Belt Thickener  57 viii  19  Pilot Scale ATAD System Schematic  58  20  Pilot Scale ATAD System  60  21  Target ORP and DO Trace Patterns  67  22  Average Precision for Solids Measurements  73  23  Average Precision for Nutrient Measurements  77  24  Average Precision for Phosphate Measurements  79  25  Average Precision for NOx Measurements  81  26  Average Precision for Ammonia Measurements  82  27  Average Precision for Ammonia in Discharge Gas Measurements  28  Average Precision for C0 , N , and 0 Discharge Gas Measurements  87  29  Pilot Scale Temperature Trace Patterns  90  30  Mechanical Heating Test Results  92  31  Influent Mixed Sludge Solids Concentrations  97  32  Aerobic Digester Percent VS Reduction Design Curve (EPA, 1990)  101  33  ATAD VS Concentration  34  Variation of Airflow with VS Load - OS Experiment  109  35  ORP and DO Trace Patterns: ATAD 1, OE1 Experiment  113  36  ORP and DO Trace Patterns: ATAD 1, OE2 Experiment  114  37  ORP and DO Trace Patterns: ATAD 2, OE1 Experiment  115  38  ORP and DO Trace Patterns: ATAD 2, OE2 Experiment  116  39  ORP and DO Trace Patterns: ATAD 1, OD Experiment  119  40  ORP and DO Trace Patterns: ATAD 2, OD Experiment  120  41  Correlation Between Initial VFA Concentrations and Duration of Low  122  2  2  2  84  104  ORP Values: ATAD 2, OD Experiment 42  ORP and DO Trace Patterns: ATAD 1, OS experiment  123  43  ORP and DO Trace Patterns: ATAD 2, OS experiment  124  44  Correlation Between Duration of Low ORP Values and Primary Sludge VS Load: ATAD 1, OS Experiment ix  125  45  Total Chemical Oxygen Demand  131  46  Soluble Chemical Oxygen Demand  133  47  OD Experiment ATAD Volatile Fatty Acid Concentration  48  Influent Sludge Nitrogen Concentration  138  49  ATAD NOx Concentrations  143  50  Influent Phosphorus Concentrations  146  x  135  ACKNOWLEDGMENTS  I would like to thank the following people and organizations for their help: B . C . Science C o u n c i l , the N a t u r a l Sciences a n d Engineering Research C o u n c i l , and  R e i d Crowther and Partners L t d . for their financial support. My thesis advisor, D o n Mavinic, for his moral support and technical input. My thesis reviewers, B i l l O l d h a m , and Les Nemeth for their technical input and presentation suggestions. Susan H a r p e r , Paula Naylor and Jufong Z h u , for all their help in the lab.  K i m Fries, for the thesis topic. Angus C h u , for his many helpful and creative ideas and for constructing and mamtaining the pilot scale A T A D system. F r e d K o c h , for designing the pilot scale A T A D reactors and for rnamtaining the pilot scale Bio-P plant. G u y K i r s c h and R o n Dolling for trouble shooting. Claudio Guarneschelli, for designing and building the aerators. B r i a n W i n g , for cooking supper and being there after long hard days. T o m a n d Annie Boulanger, for being my parents.  xi  1.0 I N T R O D U C T I O N  Sewage treatment plants produce two main commodities: clarified effluent and sludge (or biosolids). Biosolids produced by clarification and biological treatment are slurries containing less than 1 percent organic and inorganic solids mixed with liquid. Often, to reduce the volume and weight of biosolids beforefinalstabilization and disposal, they arefiirtherprocessed to minimize hquid content. Thickening processes decrease sludge Uquid content to about 94 to 96 percent. After thickening, sludge is often digested to reduce the biodegradable organic fraction and biologically stabilize the sludge beforefinaldewatering and disposal. Dewatering processes can decrease sludge Uquid content to 70 percent. When a sludge is thickened or dewatered, the liquid portion whichis removedfromthe sludge is recycled back to the plant for further treatment. This procedure is necessary because the liquid fraction of the sludge (supernatant) contains dissolved organic and inorganic contaminants in concentrations often higher than that of the raw sewage (Lawler, 1984). Recycle flows are generally small compared to the flow of raw sewage, but since contaminant concentrations are relatively high, sludge supernatant usually makes a significant impact on sewage treatment plant design. Dissolved contarninant concentrations in sludge supernatant are determined by the type of wastewater treatment process which generates the sludge, and the kind of digestion process used to stabilize the sludge beforefinaldisposal. One type of wastewater treatment process, biological phosphorus removal (Bio-P), produces liquid effluent low in phosphorus by concentrating phosphorus in the solidsfractionof the biological sludge. Phosphorus is then removedfromthe Uquid treatment system by wasting the Bio-P sludge to the sludge handling system. Therefore, for a Bio-P plant to achieve its objective it is very important during sludge tluckening, digestion and dewatering to retain the phosphorus in the soUdfraction.Otherwise, phosphorus release to the supernatant with subsequent recycling to the plant inlet would defeat the purpose of the Bio-P process. Previous work has shown that storage of raw Bio-P sludge, and mesophiUc anaerobic or aerobic digestion of Bio-P sludge can cause stored phosphorus to release (Anderson, 1993a, Knezevic, 1993). When this work commenced, digestion of Bio-P sludge in an autothermal l  thermophilic aerobic digester (ATAD) had not been studied in detail. The potential combination of a Bio-P sewage treatment system with an ATAD process is attractive for several reasons: 1. ATADs produce pasteurized biosolids free from pathogens. If such biosolids retained high concentrations of phosphorus, they would be more valuable as fertilizer and soil amendment. 2. ATADs are more cost effective than anaerobic digesters for small to medium sized communities, such as the interior towns and cities of British Columbia (Reid Crowther, 1987). Many of these towns and cities are required to remove phosphorus and nitrogen from their sewage discharges to protect receiving water quality. Therefore, the combination of Bio-P and ATAD technology might be an attractive option for wastewater treatment and biosolids handling for these communities. 3. Previous work indicated that ATADs are capable of producing high concentrations of VFAs in the digested sludge supernatant (Kelly, 1990). A recycle stream from ATADs could potentially produce the VFA rich influent that a Bio-P plant requires for optimal operation. Presently various types of fermenters are used to produce VFAs for Bio-P plants. If ATADs could be designed to produce VFAs as well as to digest Bio-P sludge, fermenters would not be required, resulting in capital cost savings. However, it is vital to determine if a VFA rich recycle stream from an ATAD would also contain significant amounts of phosphorus or other contaminants which would defeat the Bio-P process. Because of the interesting possibilities associated with the combination of Bio-P and ATAD technology, the purpose of this work was to detemrine how such a full scale system could be designed. Questions which needed to be answered included: • whether phosphorus stored in the solids fraction of the Bio-P sludge would release during ATAD digestion, requiring a side stream phosphorus removal process for supernatant recycle; • whether the level of air supply would have any effect on supernatant quality and solids destruction in an ATAD digester; • if air supply level did have a measurable effect on supernatant quality and solids destruction, what implications would this have for design. 2  This thesis is divided into six chapters, including this introduction. Chapter 2 deals with the effecjt of sludge supernatant recycling upon wastewater treatment plant design, the mechanism of biological phosphorous removal, and the effect of various processes for handling Bio-P sludge upon supernatant recycle quality. Chapter 3 discusses the theory of autothermal thermopliilic aerobic digestion, the development of ATAD technology, and ATAD full scale operating conditions. For each operating parameter, some background theory examples of full scale measurements are provided for later comparison with experiment results. Chapter 4 describes the design of this experiment, including the apparatus used, experiment conditions and laboratory techniques. Sludgefroma biological phosphorus removal pilot plant was digested in pilot scale aerobic mermophilic digesters. Since dissolved oxygen concentration is a controlling factor in Bio-P plant operation, ATAD experiments were done at three air supply levels to determine the effect upon digester performance and supernatant quality. Chapter 5 discusses the results in four subsections. Thefirstsubsection compares pilot scale ATAD operating conditions to full scale operating conditions and discusses the applicability of pilot scale results to full scale. The second looks at three different air supply experiments and characterizes them using measured parameters; the third subsection describes supernatant quality obtainedfromthe pilot scale ATAD's, and the fourth discusses the impact ATAD supernatant would have upon the influent loading to a wastewater treatment plant. Chapter 6 contains the conclusions and recommendations of this study.  3  2.0 BACKGROUND  2.1 Effect of Supernatant Recycling on Sewage Treatment Plant Design  Sludge handling can increase the loads on a sewage treatment plant. Sludge is often thickened or dewatered before stabilization, producing supernatant which is typically pumped back to the treatment plant. As afinalsludge handling step, many plants dewater stabilized sludge before disposal, producing yet another recycle stream The volume of these recycle streams is typically small; however, the concentration of contaminants is often high and can thus affect the overall plant loading. 2.1.1 Supernatant Recycle Volumes Popel and Jardin (1993) state that recycle streams consisting of underflows, overflows, supernatant,filtrates,and centrates, from sludge tMckening, stabilization and dewatering are generally on the order of one tofivepercent of the influent plant flow. Grulois et al. (1993) calculated recycle flows of between six to ten percent of the influent flow for a plant computer model with various combinations of thickening and anearobic digestion. Lawler and Singer (1984) estimated the supernatant recycle flow from anearobic digesters at one percent of plant influent flow. Aran and Lohani (1988) estimated, by computer model, that recycle flows from gravity tMckening, anaerobic digestion, and vacuumfiltrationwould rangefrom1.3 to 2.7 percent. Recent measurements at Toronto's Main treatment plant estimated the recycle flows from all sources as two percent of plant influentflow(Newbigging et al., 1994). Based on the above references, calculations done in this work to illustrate the effect of supernatant recycle from digestion alone, assumed a recycle flow of one percent of the plant influent flow. 2.1.2 Typical Supernatant Recycle Characteristics Some of the characteristics of a recycle stream depend upon the type of digestion process used to stabilization sludge, two common types of sludge stabilization are mesophilic aerobic and mesophilic anaerobic digestion.  2.1.2.1 Mesophilic Aerobic Digestion Mesophilic aerobic digestion consists of aerating sludge in an unheated open tank. Temperatures in a mesophilic aerobic digester are mainly dependent upon ambient air temperature and typically range from 9 to 30 °C. Ahlberg and Boyko (1972) summarized the results of a study of several full scale aerobic digesters, which were treating mixed primary and secondary sludge containing two to three percent total solids (TS). The characteristics of the supernatant from those digesters is summarized in Table 1.  TABLE 1 Mesophilic Aerobic Digester Supernatant Characteristics Parameter^)  Range of Plant Averages (mg/L) 228 - 8140 46- 11500 10 - 400 19 - 241 2.5 - 64  Chemical Oxygen Demand Suspended Solids Total Kjeldahl Nitrogen Total Phosphorus Total Dissolved Phosphorus ( )pH range 5.9-7.7 a  Ahlberg and Boyko (1972) observed that for proper operation, nitrate levels in aerobic digesters should be at least 10 mg/L, and that up to 100 mg/L were measured in the second stage digesters. They also measured dissolved oxygen (DO) concentrations over 1 mg/L and oxidation reduction potential (ORP) values greater than 400 mV in properly operating digesters. Jenkins and Mavinic (1989) found ammonia concentrations in pilot scale aerobic digesters from 3 to 70 mg/L. Bishop and Farmer (1978) found that sludge solids in aerobic digesters contained about two percent phosphorus, and that about tMrty percent of the total phosphorus in the system was contained in the supernatant.  2.1.2.2 Mesophilic Anaerobic Digestion Anaerobic digestion takes place in closed, heated tanks in the absence of oxygen. The temperature range for mesophilic anaerobic digestion is generally from 30 to 38 °C (EPA, 1979). 5  •  Acid forming bacteria produce VFA, but the concentration is maintained at approximately 250 mg/L because high acid concentrations and subsequent pH depression is harmful to methanogenic bacteria, which are an important part of the process. Alkalinity ranges between 2000 to 4000 mg/L as CaC03 due to ammonia buildup; the anaerobic environment does not support nitrifying bacteria. Table 2 shows characteristics of high-rate/two stage mesophilic anaerobic digester supernatant as listed in the EPA Sludge Treatment and Disposal Process Design Manual (1979).  TABLE 2 ihilic Anaerobic Digester Supernatant Characteristics Range of Plant Averages Parameter() (mg/L) 1230 - 4565 COD 250-322 VFA I475.4545 TS 143-2205 SS 814- 2930 TVS a  vss  TKN NH -N Total P0 -P 3  4  118-1660 306-1144 253 - 853 63 - 143  ( )pH range 7.0-7.8 a  Knezevic (1993), operating a pilot scale anaerobic digestion plant, found an increase in soluble COD after digestion of from 400 to 500 mg/L.  2.1.3 Impact of Supernatant Recycle on Secondary Treatment The impact of plant recycle flows on secondary treatment is primarily due to suspended solids and organic loading measured either as biochemical oxygen demand (BOD5), or chemical oxygen demand (COD). A simple mass balance can be done using the above figures and medium strength raw sewage values of 220 mg/L SS and 500 mg/L COD, with a 1 percent recycle flow from the digester.. This calculation yields a load increase due to supernatant recyclefrommesophilic  aerobic digestion offrom0 to 52 percent for SS andfrom0 to 16 percent for COD. For anaerobic digestion, the impact would be an increase in SS load offrom1 to 35 percent, and an increase in COD loadfrom2 to 9 percent. In fact, plant loading increases may be greater than the above values because the increased COD loading causes an increase in production of biological sludge, which in turn increases the recycle load. Various researchers have evaluated the impact of recycle flows on secondary treatment. Arun and Lohani (1988) found that the SS loadingfromthe recycle stream ranged between 36 to 55 percent of the influent stream load, and that the BOD loadingfromthe recycle stream ranged between 9 to 13 percent of the influent stream load. Grulois et al. (1988) found impacts of between 5 to 30 percent for BOD loading, and 2 to 17 percent for SS loading. Newbigging et al. (1994) found that over 38 percent of the total influent TSS load and 14 percent of the BOD load on the Toronto Main plant was due to recycle flowsfromanaerobic digestion, heat treatment and sludge dewatering. Quahtative effects on plant operation resultingfromincreased biological solids production include: 1. Increase of the waste activated sludge flow, 2. Increase in the secondary sludge/primary sludge ratio resulting in poorer dewatering characteristics, 3. Possible anaerobic conditions in the final clarifiers, which can lead to sludge bulking and increase in the sludge volume index (Grulois et al. 1993). 2.1.4 Impact of Recycle Flows on Tertiary Treatment Tertiary treatment, in the context of this work, will refer to biological nutrient removal, specifically m^rification/denitrification and biological phosphorus removal (Bio-P). Applying the same simple mass balance calculation as was done for secondary treatment and using values from Tables 1 and 2, a TKN load increase can be calculated for aerobic digestion offrom1 to 20 percent. For anaerobic digestion, the impact would be a load increase in TKN offrom29 to 54 percent, and, for NH ,from32 to 107 percent. 3  Wedi and Konig (1993) stated that up to 55 percent of the nitrogen in anaerobic digesters is hydrolyzed to ammonia, and the resulting recycle flows can increase the influent nitrogen load by 15 to 20 percent. Grulois et al. (1993) found an increase in the influent nitrogen TKN loading of 15 to 25 percent from anaerobic digestion recycles. Newbigging et al. (1994) found that 31 percent of the influent TKN load was due to recycle streams from anaerobic digestion, heat treatment and sludge dewatering. Other than an increase in nitrogen load upon nitrifying wastewater treatment plants, the main effect of nitrogen in recycle streams on biological liquid treatment processes is an increase in the oxygen demand in nitrifying activated sludge systems, and a possible corresponding low dissolved oxygen level in the aeration basins (which can encourage the growth of filamentous organisms). The impact of recycle flows on Bio-P plants is more complex than a simple increase in the loading conditions. Some background in the theory of biological phosphorus removal and biological phosphorus sludge handling is required in order to discuss the effects of recycle flows on Bio-P plant design. 2.2 Biological Phosphorus Removal 2.2.1 Background Phosphorus in wastewater effluent can be a problem if the effluent is discharged to a body of water where phosphorus is the limiting nutrient. Algae blooms resultingfromthe increased phosphorus concentration can cause water quality deterioration, oxygen depletion in the receiving water and subsequent deterioration of the environment for fish and other oxygen breathing organisms. Therefore, many wastewater treatment plant licenses Umit the allowable concentration of phosphorus in the plant effluent to very low levels. Phosphorus occurs in water and wastewater in three forms: orthophosphate (PO4"), poly or condensed phosphates, and organic phosphates. All of these types can occur in solution, in particulate form, or in the bodies of organisms. Phosphorus can also be found in sediments in precipitated inorganic forms (APHA, 1989).  8  Phosphorus removal can be accomplished either chemically or biologically. Chemically, phosphorus is precipitated by addition of lime or alum and removed as a chemical sludge. The disadvantages of chemical phosphorus removal compared to biological phosphorus removal are the cost of supplying chemicals, the cost of chemical handling systems, the problems of handling chemical sludge, and the greater amounts of sludge produced. 2.2.2 Theory of Biological Phosphorus Removal The dry mass of a typical bacterium is about 90 percent organic, of which 0.95 percent is phosphorus (P) found in the nucleic acids, proteins, membranes, and energy metabolism system of the cell. Therefore, these forms of organic phosphorus account for about 0.86 percent of the dry weight of a typical bacterium (Metcalf and Eddy, 1991). Phosphorus is also stored in the cell as polyphosphate, represented by Me 2P 03 i (Jardin and PopeL n+  n  n+  1994),  which accounts for an  average of 2.2 percent of bacterial dry mass. The symbol Me represents one of several possible metal cations, including magnesium and potassium. The average total percent P in cell dry mass is therefore about 3 percent, and rangesfrom2 to 5  percent (Metcalf and Eddy, 1991). In sewage treatment plants not specifically designed for bio-  P removal, there is usually about 1.5 to 3 percent P in the total dry mass of bacteria, depending on dissolved oxygen concentrations, mixing conditions and sludge age. In plants specifically designed for Bio-P removal, conditions encourage the growth of organisms (such as Acinetobacter, Pseudomonas, Klebsiella, and Flavobacterium) which can store large amounts of excess phosphorus in the form of poly-P. Jardin and Popel (1994) found that 50 to 70 percent of total P in biological sludgefroma Bio-P pilot plant could be attributed to poly-P. In biomassfroma Bio-P plant, the total percent P in volatile suspended solids (VSS) can be from 4  to  18 percent  (Toerien et al.,  1990).  If the phosphorus in plant influent is low, then the percent P in Bio-P sludge may be lower than 4 percent. At the UBC wastewater treatment pilot plant, percent P in VSS ranges between 2.8 to 4.4 percent, based upon the percent P measured in mixed liquor total suspended solids (TSS) and the volatile solids/total solids (VS/TS) ratio in thickened secondary sludge. 9  The growth of Bio-P organisms is encouraged when Bio-P bacteria encounter readily biodegradable substrate under anaerobic conditions, followed by aerobic conditions. The Bio-P bacteria can successfully compete against other strains in the anaerobic zone if there is a source of readily bio-degradable carbon. Under such conditions, the bacteria release stored phosphorus and multiply. In the aerobic zone, the increased Bio-P bacteria population stores the released phosphorus as well as phosphorus that was contained in the plant influent, effecting net phosphorus removal. A general model explains the mechanism of poly-P storage (Toerien et al., 1990). As shown in Figure 1, under anaerobic conditions, the Bio-P bacteria stores carbon from acetic acid (or another readily biodegradable substrate) in the form of poly-fi-hydroxybutyrate (PHB) granules inside the cell. As acetic acid is transported into the cell, a hydrogen ion is removedfromthe cell. The lack of a tenninal electron acceptor such as molecular oxygen or nitrate, under anaerobic conditions, increases the NADPH/NAD ratio, which inhibits the TCA cycle, increasing acetyl CoA levels and stimulating PHB synthesis. The ATP/ADP ratio decreases because of the inhibited TCA cycle. Therefore, the enzyme which manufactures ATP utilizes the bond energy and the phosphoryl group stored in the polyphosphate to make more ATP, and releases phosphate into the cell. Excess phosphate is expelledfromthe cell to restore the proton motive force which was decreased by transporting acetic acid into the cell. Sulphate, magnesium and potassium ions are also released under anaerobic conditions. Sulphate is involved in the ATP reactions, and magnesium and potassium are contained in the poly-P chains (Toerien et al., 1990). Popel and Jardin (1993) stated that magnesium and potassium were released in the ratios of about 0.30 AK7AP and 0.26 AMg/AP, respectively. Under aerobic conditions, the Bio-P bacteria is subject to fierce competitionfromother bacteria for suitable substrates. The stored PHB enables the bacteria to survive in such an environment. As the NADPH/NAD ratio decreases, the TCA cycle is again operational, allowing the stored substrate to be oxidized. The resulting energy is used to store phosphorus. Sulphate, magnesium and potassium are also taken up with the phosphorus (Toerien et al., 1990).  10  .  Ac"+H  +  Anaerobic Metabolism  Aerobic Metabolism  FIGURE 1 - Mechanism of Poly-P Storage and Release (Toerien et al., 1990)  ll  2.2.3 Factors Affecting Phosphorus Release Factors which can affect phosphorus release and bacterial growth in the anaerobic zone of the biological phosphorus treatment plant are discussed below: 2.2.3.1 Concentration of Easily Biodegradable Substrates A sufficient concentration of readily biodegradable substrates is required to enhance phosphorus release, as explained in Section 2.2.2. Under even aerobic or anoxic conditions P release can be induced if enough acetate is added; even high concentrations of nitrates will have a negligible effect on P-release, if the influent COD is high enough (Toerien et al., 1990). Rabinowitz (1985) showed that acetate and propionate are the most effective fatty acids in inducing P-release. Fuhs and Chen showed that the addition of CO2 also caused rapid release of phosphate under anaerobic conditions (Toerien et al., 1990). 2.2.3.2 Nitrate Concentration. The presence of nitrates prevents the anaerobic condition necessary for phosphorus release under low VFA conditions. Also, the presence of nitrates will allow denitrifying bacteria (which use nitrate as a final electron acceptor) to consume some of the substrates which Bio-P bacteria need for PHB storage. Rabinowitz (1985) stated that denitrifiers consume 3.6 mg COD/ mg NO3-N reduced. If a plant is nitrifying as well as removing phosphorus, the rmximum influent TKN/COD ratio that can be tolerated is 0.1 mg N/mg COD. If this ratio is greater than 0.14 mg N/mg COD and complete mtrffication/denitrification is occurring in the plant, excess Bio-P removal is not likely because there will insufficient carbon sources rernaining in the anaerobic zone for Bio-P bacteria PHB storage (Toerien et al., 1990). 2.2.3.3 Dissolved Oxygen Concentration. Randall et al. (1970) found that anaerobic P-release began at zero DO concentration, and followed first order kinetics. Randall also noted that phosphorus release began before there was any significant change in ORP levels. Schon et al. (1993) observed that phosphorus release 12  occurred at DO concentrations as high as 0.5 mg/L, but did not release at the maximum rate until there was no more measurable DO. As noted in Section 2.2.3.1, high concentrations of VFAs can effect phosphorus release even under aerobic conditions (Toerien et al., 1990) After complete anaerobic release, Schon et al. (1993) found that phosphorus uptake began at the maximum rate at 0.1 mg/L DO. Wells (1969) observed high P uptake rates at 0.2 mg/L DO. 2.2.3.4 Effect of Supernatant Recycle The above discussion indicates that the Bio-P process is very sensitive to the characteristics of the influent stream. Important parameters (over and above SS and COD which affect secondary treatment), are influent phosphorus concentration, volatile fatty acid concentration, and nitrate concentration. Therefore, control of the recycle stream is important when designing a successful Bio-P process. 2.3 Handling Bio-P Waste Activated Sludge Phosphorus removalfromthe Uquid train of the sewage treatment plant is accompUshed by wasting activated sludge containing stored poly-Pfromthe aerobic zone. This phosphorus rich sludge requires subsequent careful handUng to minimize phosphorus release during storage, thickening, digestion, and dewatering. If phosphorus does release during sludge handling, the supernatant return to the Uquid treatment train may contain a significant portion of the phosphorus that was stored in the Bio-P sludge and the effective phosphorus removal efficiency of the plant witt be greatly decreased. 2.3.1 Before Digestion . Bio-P sludge wiU begin to release phosphorus once it becomes anaerobic. Co-thickening of primary sludge and Bio-P sludge can cause phosphorus release due to a combination of anaerobic conditions and relatively high concentrations of volatile organic acids (Popel and Jardin, 1993). Therefore, separate thickening of sludges in Bio-P plants is recommended (Florentze et al., 1987, Barnard, 1978). DAF units are used at many Bio-P instaUations in Canada, mcluding Kelowna 13  and Westbank. At these plants, DAF thickened Bio-P sludge is composted, and the runoff is reapplied to the compost piles, thus solving the problem of supernatant return to the Bio-P plant. The Phostrip process (Figure 2) is another way of dealing with the phosphorus release problem (Matsch and Drnevich, 1978). Phosphorus is deliberately anaerobically stripped from a portion of the recycled sludge by retention in a stripper tank for several hours. Phosphorus is precipitated from the resulting high-P supernatant using lime, and the chemical sludge is removed from the process in the primary clarifier. The Phostrip process is therefore a combined biological/chemical phosphorus removal process.  WASTEWATER  EFFLUENT PRIMARY  AERATION  SECONDARY! CLARIFIER  CLARIFIER  DIRECT  RECYCLE  WASTE SLUDGE STRIPPER LIME  SUPERNATANT  WASTE ' SLUDGE m  STRIPPER  STRIPPER FEED  FIGURE 2 - The Phostrip Process (Matsch and Drnevich, 1978) 2.3.2 During Digestion In many sewage treatment plants, sludge is digested before final disposal. If sludge from the digester is dewatered, it becomes extremely important to determine how much phosphorus is released to the liquid phase under the digester conditions because the supernatant is usually returned to the plant forfarthertreatment. Randall et al. (1989) reported that their Bio-P plant could not achieve effluent total phosphorus (TP) concentrations below 2 mg/L, partly due to the recycle flow from dewatering after anaerobic digestion. 14  2.3.2.1 Anaerobic Digestion Under mesophilic anaerobic digester conditions, biologically stored phosphorus is released, as shown by Mavinic and Anderson (1990), and Anderson and Mavinic (1993a). Jardin and Popel (1994) estimated that at 35 °C, 90 percent of poly-P is hydrolyzed within 1.5 days. However, Wedi and Koenig (1993) and Popel and Jardin (1993) found that in Germany, phosphorus feedback in supernatant recycledfromanaerobic digesters was low. These researchers speculated that low phosphorus feedback may be due to chemical precipitation reactions occurring in the anaerobic digester. In pilot scale studies, Popel and Jardin (1994) found that struvite (MgM^PO^^O) was precipitated in an anaerobic digester due to simultaneous release of magnesium when poly-P from Bio-P sludge is hydrolyzed. Struvite formation was also observed in the anaerobic digesters at the York River treatment plant (Randall, 1990). Phosphorus feedback in this system was only 30 percent. In the presence of calcium hardness, hydroxyapatite and other calcium phosphate precipitates can also form in anaerobic digesters. To completelyfixthe soluble phosphate 2.5 mg Ca is required per mg P (Popel and Jardin, 1993). Knezevic (1993) used lime to lyse waste activated sludge before anaerobic digestion, and noted a decrease in soluble phosphorus in the digester supernatant, probably due to precipitation of a calcium-phosphorus complex. Other types of phosphorusfixationinclude absorption, and biologicalfixationby Methanosarcinaceae . After 20 days of digestion, adsorbed phosphate can reach up to 10  percent, based on the total phosphorus content of digested sludge. How much phosphorus can be fixed biologically is not yet known (Popel and Jardin, 1993). Despite all these possible forms offixationand the German experience, phosphorus feedback from anaerobic sludge digestion can still be high. Neodbala (1993) observed a 75 to 85 percent release of PfromBio-P sludge in pilot scale anaerobic digesters, even though the magnesium concentration in the digestion process was 45 mg/L. Plants in the Netherlands and Japan experience phosphorus feedback of up to 100 percent (Popel and Jardin, 1993). Clearly, all the  15  factors affecting phosphorus precipitation reactions in anaerobic digesters are not yet well understood. 2.3.2.2 Aerobic Digestion Under mesophilic aerobic digester conditions of endogenous respiration, lowpH and small amounts of soluble substrate, stored phosphorus is released into solution (Anderson and Mavinic, 1993a). The Bio-P organisms at that point have no stored PHB, and with little soluble substrate, the bacteria must utilize their protoplasm as a food source. Stored Poly-P is expelled since it is not useful as substrate (Anderson and Mavinic, 1993a). Release of stored phosphorus is slower under aerobic conditions than under anaerobic conditions, essentially a linear relationship with aeration time (Randall et al., 1980). Jenkins and Mavinic (1989) showed that low pH conditions in the digestion process resulted in higher phosphorus concentrations in the supernatant. Lysing of dead microorganisms also releases stored P (Toerien et al., 1990). Anderson and Mavinic (1993) and Jenkins and Mavinic (1989) found that when lime was added to aerobic digesters to counter the pH drop produced by nitrification, there was less phosphorus in the soluble fraction of the sludge. The phenomenon was possibly due to formation and precipitation of calcium-phosphate complexes. 2.3.2.3 Anoxic/Aerobic Digestion Wells (1969) showed that if activated sludge was sequentially aerated during the day and left unaerated during the night, phosphorus release occurred during the night followed by phosphorus uptake the next day when the sludge was aerated. However, the amount of daily P uptake decreased progressively until, on the fourth day, P uptake was 30 percent of the initial value. Mavinic and Anderson (1990) compared mesophilic anoxic/aerobic digestion to pH controlled aerobic digestion. Although chemical precipitation of phosphorus was probably occurring in the pH controlled digester, they found that soluble P in the anoxic/aerobic digester was only slightly higher than in the pH controlled aerobic digester.  16  Peddie and Mavinic (1988) demonstrated that sludge digested at 15 °C in an anoxic/aerobic mode would have less phosphorus in the supernatant than a digester operating in fully aerobic mode, under otherwise identical operating conditions. Peddie and Mavinic speculated that phosphorus removal might be due to precipitation caused by alkalinity release during denitrification in the anoxic cycle. Jenkins and Mavinic (1989) showed that anoxic/aerobic digestion of sludge at 20 °C, with a 20 day SRT, resulted in half the phosphorus release occurring in an aerobic digester operating under the same conditions. These researchers speculated that this result may have been due to higher pH in the anoxic/aerobic digester which might have affected precipitation reactions. Struvite, for example, is least soluble at pH 10.7 (Popel and Jardin, 1993). 2.3.2.4 Autothermal Thermophilic Aerobic Digestion (ATAD) There is one known instance of a full scale ATAD facility treating sludgefroma Bio-P plant, and this is in Salmon Arm, B.C. Kelly (1990a) lists one TP determination for sludge in Salmon Arm's ATAD No. 2 as 848 mg/L, but there are no recorded soluble phosphorus measurements in that report. Jardin and Popel (1994) conducted pilot scale experiments (concurrent with those presented in this work) in which Bio-P sludge was digested in 1.5 m ATAD digesters. Their 3  research showed that Poly-P stored in Bio-P sludge would be released to solution by hydrolysis, but that much of it would be precipitated either as struvite or aluminium phosphate. Their estimated P-release kinetics predicted that at 60 °C, 90 percent of stored poly-P would be hydrolyzed vvithin 7 hours. ATAD is an attractive option for sludge digestion for small and medium-sized wastewater treatment plants (Wolf, 1982, Vik and Kirk, 1993). In British Columbia, this is the size of facility which typically is concerned with biological phosphorus removal. Reports of high volatile fatty acid (VFA) measurements in operating ATAD facilities in Banff (Schuster, 1991) and Salmon Arm (Kelly, 1990) generated interest in ATAD's as a source of VFA's for the biological phosphorus removal process. However, the effect of ATAD on Bio-P sludge in terms of supernatant quality and possible phosphorus recycle was not known at that time. The purpose of 17  this research was to investigate further the effects of ATAD digestion upon the probable concentrations of soluble phosphorus in recycle streams from ATAD digesters to a Bio-P plant, and particularly to determine the effect on ATAD supernatant quality of varying aeration levels.  18  3.0 AUTOTHERMAL THERMOPHILIC AEROBIC DIGESTION  3.1 Technology Development  ATAD technology originated in Germany in 1968 when H. Fuchs noticed a marked temperature increase while aerating livestock wastes. Since then, approximately 50 ATAD facilities have been installed, mostly in Germany but also in Austria, Switzerland, Great Britain, Norway and Canada (Schwinning et al. 1993, Burnett, 1994). ATAD digesters operate at elevated temperatures, which mean faster rates of biological reactions, faster sludge stabilization, shorter retention times, smaller tanks, and lower capital costs, and a pasteurized product. The heat required to raise sludge temperatures is generated by a combination of applied mixing/aeration energy and biochemical energy release. The success of the process, therefore, hinged upon the development of a system which could conserve heat. 3.1.1 Theory 3.1.1.1 Heat of Reaction When bacteria degrade organic molecules into their simpler constituents of carbon dioxide and water, energy which was stored in the bonds between the atoms is released. Some of this energy is used to fuel the inner workings of the bacteria and some is used to create more bacteria, but most of the energy is released as heat. Popel and Ohnmacht (1972) found that the total heat produced per gram of organic matter oxidized varied with both sludge type and the type of organism involved. Primary sludge contained 3.033 - 3.411 kcal/g organic solids. Activated sludge ranged between 3.136 kcal/g organic solids for a high rate sludge, to 3.765 for an extended aeration sludge. Organisms when cultured upon glucose carbon released varying amounts of heat; Escherichia Coli could produce 12.63 kcal/g of glucose carbon oxidized, Bacillus Subtilis produced 11.63 kcal/g and yeast could only produce 9.69 kcal/g carbon oxidized. Jewell and Kabrick (1980) stated that the oxidization of most organic matter will release 3.5 kcal/g COD in the substrate. Since 1 kcal of heat will raise the temperature of 1 liter of water by 19  1 °C, the resulting approximate temperature change df sludge resulting from COD oxidation would be: (2.1)  A°C = 3.5(A g COD)  Loll (1984) later corrected this figure to 3.5 - 4.0, including heatfrommechanical aeration. Therefore, if the concentration of COD in a waste is high enough and if heat is not lost to the surrounding environment, the temperature of the waste will rise as it is degraded by bacteria. One example of this phenomenon is found in solid waste composting facilities, where temperatures in compost piles been recorded above 70 °C (Haug, 1993). 3.1.1.2 Change of Reaction Rates with Temperature As the temperature of a waste undergoing biochemical oxidation rises, the rates of reaction will increase. This phenomenon has been studied since the early part of this century, and the behavior of reaction rate constants up to about 40 °C is well understood as: (2.2) Reported values of G rangefrom1.00 to 1.08. This rektionship results in roughly a doubling of the reaction rate with an increase of 10 °C in temperature (Metcalf and Eddy, 1991). The equation above applies to the behavior of mesophilic bacteria which are active in the range of 20 to 45 °C. Above 45 °C, meimophilic bacteria dorninate and the rate of reaction rate change with temperature does not follow Equation 2.2. Kambdu and Andrews (1969) proposed the relationship illustrated in Figure 3 for the change in the reaction rate with temperature. The equations shown in Figure 3 apply to the mesophilic portion of the curve, below 45 °C. 3.1.1.3 Thermophilic Organisms TJiemophilic organisms can be roughly divided into three groups: the thermotolerant group, with optimum growth conditions between 40-50 °C, the moderately thermophilic group, which prefers the 50-65 °C range, and the extremely thermophilic group, which can survive at over 65 °C. At the higher temperatures organism diversity decreases. Sonnleitner and Feichter  20  0.50  ref  g- 0 . 4 0 -o  c 0.30 o </> c o  o  0.20  o  DC  o = o o  0.10  a> 40  _ 0 _ Temperature, C  50  70  80  FIGURE 3 - Reaction Rate Constant as a Function of Temperature (Kambdu and Andrews, 1969) (1983a) found that 100 to 1000 times fewer organisms could grow at 70 °C than at 50-55°C. For this reason, Loll (1984) suggests that an aerobic mennophilic degradation system should not be operated above 65 °C. Organisms which can degrade sewage sludge at temperatures above 45 °C, under aerobic conditions, are predorninantly Bacilli (Sonnleitner and Feichter, 1983a). Most of those have been identified as B. Stearothermophilus, but other strains have been identified as B. mermodettitrificans, B. caldotenax, and B. caldovelox (Sonnleitner, 1983). A few mycelia forming organisms, Aspergillus, Mucor and Penicillium can also be found (Sonnleitner and Feichter, 1983a). Figure 4 shows a scanning electron micrograph oftiiermophilicorganisms and feed yeast organisms from Mason et al. (1987a). A dominant characteristic of mermophilic organisms is their fast reaction rates. Proteolysis, denitrification, and hydrolysis of starch by thermophiles proceed at rates 7-14 times that of cultures of mesophilic bacteria, and thermophiles have higher death rates and autolytic rates  21  FIGURE 4 - Scaiining Electron Micrograph of Themoplvilic Organisms and Feed Yeast Cells (Mason et aL, 1987a) than mesophiles. (Kambdu and Andrews, 1969). Generation times are much less than 1 hour if there is enough substrate (Feichtner and Sonnleitner, 1988). The rapid growth rate enables thermophiles to live in a single pass system, even at hydrauhc retention times (HRT) as low as 0.53 days according to Fuggle and Spensley (1985), or 0.42 days according to Sonnleitner and Feichtner (1983a). Another characteristic of an aerobic hemophilic population is its resistance to adverse conditions. The bacilli are spore formers, and thus can survive temperatures below 40 °C (Feichtner and Sonnleitner, 1988); the facultative thermophiles can grow in mesophilic temperatures but at a slower rate (Fuggle and Spensley, 1985). An aerobic hemophilic process is able to recover by itselffromhighly concentrated intermittent loading of heavy metals, and can carry toxic loads 10-100 times greater than an anaerobic process before it shows a drop in  22  efficiency or ceases activity altogether (Loll et al., 1986). Thermophilic aerobic populations can also easily survive anaerobic conditions (Sonnleitner and Feichtner, 1985). 3.1.2 Heat Production and Loss Using a mathematical model, Kambdu and Andrews (1969) demonstrated that bioheating (or autoheating) of organic wastes was theoretically possible. The model showed that by supplying sufficient substrate to a microbial population and minimizing heat loss to the surrounding environment, thermophilic temperatures could be reached. Figure 5 summarizes the heat inputs for and lossesfroma typical autoheated thermopliilic aerobic system.  MIXING HEAT INPUT GAS INPUT (AIR)  SENSIBLE AND LATENT WATER VAPOUR HEAT LOSS WITH DISCHARGE GAS HEAT LOSS TO SURROUNDINGS  FEED _ SLUDGE HEAT LOSS IN DIGESTED SLUDGE  BIOLOGICAL HEAT PRODUCTION  FIGURE 5 - Heat Balance for an Autoheated Thermophilic Aerobic Digester Heat inputs are: 1. Biological heat generated by aerobic organisms, 23  2. Energy required to mix the sludge and create good mass transfer conditions, 3. Influent sludge mass. As explained in Section 2.3.1.1, biological heat generated depends on the type of solids to be oxidized, the type of organisms present, and the concentration of biological solids available for oxidation. Temperature affects the rate at which the reactions progress, and therefore the rate at which more heat is generated. Time in the reactor affects how much of the organic solids are oxidized, and also the rate of oxidation as the availability of the food to the microorganisms decreases with time. Some energy input is required to mix the biomass and substrate and ensure good mass transfer conditions for substrates and gases. Modern ATADs use two types of mechanical mixing/aeration systems - aspirating aerators and venturi aeration. Examples of each are shown in Figure 6. Wolinksi (1985), using a venturi aeration system with compressed air, found that 17.6 percent of the heat input camefromthe influent sludge flow, 55.1 percent camefrombiological heat production, and 27.3 percent camefrommechanical heat input. Booth and Tramonti (1983), using a similar system but supplying pure oxygen rather than air, found that 24 percent of heat input camefromthe pump, and the restfromthe heat of reaction. Heat lossesfromthe system are from: 1. Wasting digested sludge, 2. Radiation to the surroundings, 3. Gas discharge, including water vapour. Wolinski's measurements showed that with his system, 56.9 percent of the heat loss was from wasting of effluent sludge, 41.8 percent was radiated to the suiroundings, and 1.3 percent was lost with the effluent gas. Booth and Tramonti found that 60.6 percent was lost with wasting of effluent sludge, and 38.3 percent lost to the siirroundings, with negligible lossfromthe pure oxygen gas flow. Jewell and Kabrick (1980) using aspirating type aerators, estimated that 60 percent of heat lostfromthe Binghamton system was in the wasting of digested sludge and 40 percent was lost through radiation and gas discharge.  24  Aspirating Aerators (Breitenbucher, 1984)  Venturi Aeration System (Wolinski 1985)  GAS METER  FOAM DRAIN TO WORKS SLUDGE-WELL  f  T  '  DRAIN FOR DIGESTED SLUDGE  FIGURE 6 - Types of ATAD Aeration Systems  25  3.1.3 Minimizing Heat Losses Most of the early ATAD research attempted to both maximize oxygen transfer efficiency to decrease off gas heat losses, and to minimize heat losses by radiation. Researchers were working prirmrily in Germany, the United States, and Great Britain. 3.1.3.1 Germany Experiments using aerobic thermophilic digestion to stabilize sludges began in West Germany in 1968 in the research stations of Fuchs Wassertechnik (Breitenbucher, 1984). The Unwalzebelufter (Deeny et al., 1985), a recirculation type aerator using air and developed by Fuchs, was used to digest animal manure in tanks of20-45 m capacity. In the early 1970's, the tests were expanded to include wastewater (Popel and Ohnmacht, 1972). This work led to the cornmissioning of a full-scale Fuchs aeration ATAD plant in Vilsbiburg in 1977. The next municipal sludge plant was built at Gemmingen in 1980 as a federal research project. Basic research was continued there for the next two years (Breitenbucher, 1984). By 1982, there were 10 ATAD plants operating in West Germany (Wolf, 1982). Further experimental work in Germany has investigated: 1. Treating thin sludge using ATAD (Vismara,1985). 2. Salmonella kill using the Thieme proprietary aeration system (Strauch et al., 1984) 3. Dual digestion (Loll, 1984) 4. The effect of heavy metals on the mermophilic process (Loll et al., 1986). As of 1990, there were 35 full scale plants operating in Germany. 3.1.3.2 United States Interest in auto-heating of sludge in the USA began with the paper by Kambdu and Andrews (1969). In 1971, sludge autoheating was demonstrated at the Hamilton Ohio plant. A sludge digester, treating 4 percent combined primary and secondary municipal sludge, was converted from anaerobic to aerobic operation with diffused aeration and unexpectedly achieved operating 26  temperatures of 38 °C. Tests were discontinued due to excessive odours from the uncovered tanks at the higher temperatures (Smith et al., 1975). In 1972, Union Carbide started pilot plant work using pure oxygen for aeration at the Tonawanda research facility in New York. Researchers felt that pure oxygen was necessary because of the low aeration efficiency of the aerators they were familiar with. The experiments were done in a 200 L covered insulated reactor (Matsch and Drnevich, 1977). Other studies were done with pure oxygen in open tanks. Cohen and Puntenney did batch tests in 1973 in Denver, Colorado with open 6.4 m tanks acMeving operating temperatures of 44.5 °C (Smith et al. 3  1975). At Speedway, Indiana, Smith et al. (1975) and Matsch and Drnevich (1977) applied the Tonawanda results to convert one of the aerobic sludge trains to pure oxygen. Temperature rises of 13.3 and 15.6 °C above ambient were recorded. Other work in the USA was attempting to determine some of the kinetic constants of tiiennophilic systems. Surucu et al.(1976) did bench scale tests using a defined culture medium and thermophilic organisms in a heated reactor, at various solids retention times (SRT). ATAD using air aeration began in the USA in 1977, the same year the Vilsbiburg plant opened in Germany. Jewell and Kabrick (1980) were working in Binghamton, NY. with Delaval selfaspirating aerators, whose design was based on the Unwalzebelufter. Thickened 5 percent primary and secondary sludge was treated in a 33.4 m reactor. Dual digestion, consisting of an aerated thermophilic first stage, followed by mesophilic anaerobic digestion, also was being investigated, and in 1980 the Hagerstown full scale dual digestion plant opened. There are, at present, no full scale operating ATAD-only sludge treatment facilities in the US., but a new installation in Grand Chute, Wisconsonis expected to be commissioned in 1994, (Schwinning et al., 1993) and a facility is presently being designed for College Station, Texas (Burnett, 1994). A venturi-aerated system is also being marketed in the US under the trade name AuthoTherm Digestion.  27  3.1.3.3 Great Britain Interest in ATAD in Great Britain developed in the early 1970's. By 1975, a 9 m pilot plant 3  at the Ponthir sewage works in Wales was successfully operating using pure oxygen. The plant was subsequently converted to a new type of venturi compressed air system developed by the British. In 1979, the air operated pilot plant achieved 61 °C operating temperature (Morgan and Gunsen, 1987). In 1981, the entire Ponthir plant was converted to autothermal thermophilic sludge digestion with continuous sludge feed. Operating temperatures were dependent on environment ambient temperatures, since the tanks used were the old open digestion tanks and were not well insulated (Morgan et al., 1983). Experiments at the Palmersford plant in Wessex in 1980 began using pure oxygen in an above ground insulated 60 m digester (Booth and Tramonti, 1983). Subsequent tests with air aeration 3  achieved operating temperatures up to 67 °C (Morgan et al., 1986). Because of excessive foaming, operating volume was reduced to 24-30 m (Wolinski, 1985). Based on the Palmersford results, the Ponthir ATADs were converted to above ground insulated tanks with automatic foam control and were commissioned in 1986 (Morgan et. aL 1986) . Other ATAD plants in the UK include Haltwhistle and South Harrogate (Reid Crowther, 1987) . 3.1.3.4 Canada and Elsewhere In the early eighties, interest in ATAD began to spread to the rest of the world. In Switzerland, interest was rminly in dual digestion systems. Sonnleitner (1983) and Sonnleitner and Feichter (1983a, 1983b, 1983c, and 1985) studied the microbiology of the tjiennophilic organisms developed in the aerobic pre-stage pilot plant at Altenhehn. Mason et al. (1987a) studied how thermophilic microorganisms digested mesophilic organisms, in this case yeast cells. In Norwayfrom1983-84, Langeland and Paulsrud (1984) studied the fate of salmonella in a three stage, full scale, pure oxygen pilot plant. Similar studies were taking place in South Africa, where Trim and McGlashen (1984) operated an 8 m pure oxygen plant for 3 years. There are 3  also ATAD plants in operation in France and Italy (EPA, 1990). 28  In Canada, ATAD systems were being designed as of 1987. Full scale Fuchs units were installed at Ladysmith, B.C. and Banff, Alberta. Venturi-style aeration plants were built at Gibsons and at Whister, B.C. and an existing system in Salmon Arm, B.C. was upgraded to ATAD, using a locally designed and built aspirating aeration system commercially marketed as Turborator Technology. 3.2 Operating Conditions  This research attempted to detennine, at pilot scale, the characteristics of Bio-P sludge digested in a full scale ATAD system. Therefore, the intent was to operate the pilot scale reactors under conditions as close as possible to full-scale operating conditions. This Section discusses full-scale operating conditions. In Chapter 5, the experimental results are compared to the operating conditions in full scale ATADs described in this section, in order to evaluate the apphcability of the pilot scale results to full scale. 3.2.1 Temperature 3.2.1.1 Design Guidelines ATAD installations operate in the hemophilic range, normally at average temperatures greater than 45 °C. The EPA ATAD design manual (EPA, 1990) states that, when operating two reactors in series, the target design temperature should be from 35 to 50 °C in the first reactor, and 50 to 65 °C in the second reactor. Above 65 °C, the bacterial population diversity is limited and reaction rates are slower, as discussed previously. 3.2.1.2 Feeding Temperature Patterns When sludge at ambient temperature is fed to an ATAD, the average tank temperature drops abruptly and thenriseswith time. Deeny et al. (1991) reports that during batch feeding of two tanks in series, the temperature in the first vessel (ATAD 1) can be expected to drop 5 to 10 °C per day, with a recovery rate of about 1 °C per hour. In the second vessel (ATAD 2), he predicts a temperature drop between 4 to 6 °C, with a higher recovery rate than for ATAD 1. 29  Figure 7,fromthe EPA ATAD Design Manual (EPA, 1990), shows temperature curves for the full scale Gemmingen plant in Germany. During the period shown, this plant treated waste activated sludge containing 30,000 mg/L (3 percent) volatile solids. The 24 m ATADs were fed 7-10 m of sludge once per day (Breitenbucher, 1984). Reactor 1 operated between about 47 and 63 °C, with about a 12 to 16 °C temperature drop after feeding each day. Temperature in Reactor 2 varied only a few °C per day. 40  I ^ I N  r  30 co co >  20  O — .—  10 70  1  60 _^  o  O UJ oc  <  cc LU CL LU  50  '  '•  V  '/  /  '-a—•  /  : / •/  :/  \ / '/  •  •/  '/  \/  /  /  40 30  AIR  20  0 9 8 7 6  '-^^  • — « —  — X  _ — o —  — o  —C,  D  — D  •-="*—  •  •  — — « —  \WSL  10  Q.  — o-  ,  r / !• •An I U H 1  ~~— • — •  r  —o  )RII  / REACTC  -n—*  y  y  ..EFFLUENT Lo o~~  —o •  o  LUENT  o  1  „  .  — O  —  •  J  1 ~  •*»  1 TEFFLIJENT * INFLUENT — o r-o_+_o—  — o  — o —  i—o  —o  —n 12  D  -: — a  — —  o — —  o  15  TIME (d)  FIGURE 7 - Gemmingen Temperature Curves (EPA, 1990)  In Figure 8, temperature curves for the Eichbactal plant takenfromSchwinning et al. (1993), show a less drastic temperature change upon feeding (about 43 °C to about 38 °C in Reactor 1, and only a couple of degrees drop in Reactor 2);  30  7D -6  00  AA * A A A  5D  0 3  4D  3  3a 20  1D  17  13 11 HOLT-  13  21 13  23  CS/16/930  *  Reactor  1  A.  Reactor  2  FIGURE 8 - Eichbactal Daily Temperature Curve (Schwinning et al, 1993)  3.2.1.3 Mixing Energy Levels High rnixing energy levels are required in an ATAD to keep the digesting solids in suspension, and to ensure good oxygen and substrate transfer to the microorganisms. The EPA ATAD manual (EPA, 1990) recommends 85-105 W/m . Kelly (1990) recommends 250 W/m , based 3  3  upon minimum mixing energy requirements quoted in ASCE and A WWA Water Treatment manuals. Some of the temperature rise observed in an ATAD is the result of kinetic energy transmitted by mixing. A measure of this energy is the mixing system power draw. Not all of this energy is transmitted to the liquid, since motors are not 100 percent efficient. Usually about 85 percent is transmitted (Reid Crowther, 1987). 31  3.2.1.4 Full Scale Values Average operating temperatures and rnixing energies for full scale plants are shown in Table 3. TABLE 3  Full Scale ATAD Average Operating Temperatures and Mixing Energy Input Location Temperature of Temperature of Mixing Energy ATAD 1 ATAD 2 (W/m) (°C) (°C) 3  Canada Banff© Ladysmith() Salmon Arm() Whistler^) a  a  Germany EllwangenC) Fassberg() Gemmingen() IsenbuttaK) Nettetal-Viersen() Rheinhausen() Vilsbihurg() 0  c  c  c  c  d  c  26-33 32-56 39-66  44-51 40-63 40-66  114-157 135-200 200 80-250  35-43 40-45 30-50 40-55 38 42 60  48-50 50-70 50-60 45-60 58 60 69  83 117 109  ( ) Kelly et al. (1993), Temperature measured once daily. Measured applied power. (b) Schwinning et aL 1993 (c) Deeny et al. (1985) ( ) Deeny et al. (1985) Arithmetic mean of measurements taken during 14 weeks. () Kelly (1991) Design applied power ® Schuster (1994). For periodfromOct./93 to Nov./94. When operating three digesters in series, temperature in ATAD 3 rangesfrom53 to 56 °C. a  d e  3.2.2 Solids 3.2.2.1 Solids Feed Concentration Design Guidelines To maintain thermophilic temperatures in an ATAD, the digester feed must contain a high concentration of solids. A high feed solids concentration has the following effects: 1. The amount of food available is niaximized, which sustains the high metabolic rate of the thermophilic organisms and produces more heat. Bornio et al. (1989) found that 68 percent of  32  thermophilic activity is due to growth on particulate matter and only 32 percent is due to growth on soluble substrates. 2. The volume of water added to the reactor is minimized. Water has a high heat capacity and, if present in excess, slows temperature rise. The EPA ATAD Design Manual recommends that for a Fuchs style system, feed sludge concentration should be 4 to 6 percent TSS , and 2.5 percent biodegradable VS (EPA, 1990). Breitenbucher (1984) states that for a rriixture of primary and secondary waste activated sludge, more than 3.5 percent TS and 2.5 percent VS is required to maintain high temperatures.  3.2.2.2 Solids Loading Rate Design Guidelines Kabrick and Jewell (1982) did experiments at the Binghamton-Johnson City (NY.) plant using loading ratesfrom2.6 to 13.5 kg VS/(m d). Loll (1984) recommended that full scale plants be 3  loaded at a rate of 4 to 5 kg dry weight organic matter/(m d).  3.2.2.3 Solids Retention Time Design Guidelines The EPA ATAD Design Manual recommends that minimum SRT befrom5 to 6 days in a two-stage system, or 2.5 to 3 days per reactor. Typical system design residence times are 6 to 10 days. Residence times longer than 10 days can decrease process efficiency as temperatures drop due to lack of volatile solids to fuel the aerobic reactions which generate heat (Burnett, 1994).  3.2.2.4 Volatile Solids Destruction Various VS reduction values have been reported for full scale ATAD installations. Jakob et al.(1988) stated that with a minimum HRT of 6 days, 25 to 35 percent reduction of organic material could he achieved. Jewell and Kabrick (1980) showed that in both batch tests and a full scale continuous feed operation, about 33 percent VS reduction could be achieved using a 6 day SRT. Their experiments also showed that as the VS loading rate decreased, the rate of VS removal decreased (Figure 9). Deeny et al. (1991) stated that 60 percent of VSS destruction occurs in the first reactor. 33  FIGURE 9 - The Effect of Biodegradable Organic Loading Rate on Organic Removal Rate (Jewell and Kabrick, 1980) VS reduction has also been reported to vary with the level of oxygen supply. Wohnski (1985) found that percent VS reduction increased with the kg O2 supplied per kg TS fed. Mason et al. (1987a) found that in lab scale reactors with pH control a larger TSS reduction was achieved under oxygen limited conditions (<10 percent saturation) than under oxygen excess conditions (>30 percent saturation). 3,2.2.5 Full Scale Values Table 4 suinmarizes full scale measured values for influent solids concentration, solids loading, SRT, and VSS reduction.  34  TABLE 4 Full Scale ATAD Solids Design Values SRT vss Feed Sludge Solids Loading Reduction TS . VS (%) (%) (kg VS/m3-d) (d) (%)  Location  Canada  Banff() Gibsons() Ladysmith() Salmon Arm() d  a  a  a  2.6 4.1 5.4 4.6  2.2  2.8 17 5-10 20  7.1 4.8 20 6.1  31 38 38 34  12.1  3.3  5.0 2.3 8.3  6.0  48 38 25-40  4.5  43-66  3.4  41  Germany  Backnang() Fassberg() GeinmingenO) IsenbuttalCb) Kirchburg() NettetalViersenO) Romersburg() VilsbiburgO) c  e  5  c  3  4.4 5.0 4.0  3.7 3.0 3.1  5.5  3.6  3.5  2.8  7.0 1L7 2.8  c  ( ) Kelly et al. (1993) VS reductions reported are average values (°) Deeny et al. (1985) All values in TSS and VSS. Solids destruction Deeny et al. (1991) (°) Deeny etal. (.1991) ( ) Schuster (1994) For period from Oct./93 to Nov./94. (e) Schwinning et al., 1993 a  d  3.2.3 Aeration Conditions 3.2.3.1 Oxygen Requirement There are two ways to determine the metabolic oxygen requirements of mermophilic aerobic bacteria. The maximum short term oxygen demand is measured by the standard oxygen uptake rate (SOUR). The average oxygen demand is the stoichiometric amount of oxygen required to oxidize a given amount of VSS. The SOUR in an ATAD was found by Popel et al. (EPA, 1990) to vary over a 24 hour feeding cycle, as shown in Figure 10. The average SOUR was 287 g 0 /(dkg VSS), with a minimum of 2  35  just under 400 g 0 /(dkg VSS) occurring shortly after feeding, and a minimum of about 100 g 2  0 /(dkg VSS) occurring just before feeding. 2  500  c >n CO  400  r  < a  o  t  300  cn  >  o  200  <  z o  100  <  cc a w  LU d  0 05 JUN  09-JUN  07-JUN  11-JUN  13-JUN  15-JUN16-JUN  18-JUN  20-JUN  FIGURE 10 - Respiration Rate of Mixed Liquor in a Single Stage ATAD System (EPA, 1990) Bomio (1989) found an initial lag period after feeding, as shown by his results in Figure 11 which also shows a maximum OUR 12 hours after feeding. This researcher used an average SRT of 18 hours. The amount of 0 required to oxidize the carbon contained in the substrate can be estimated in 2  several ways. One such estimate is 1.42 kg 0 /kg VS destroyed, (EPA, 1990) based upon the 2  equation C H N0 + 50 => 5C0 + 2H 0 + NH + energy. 5  7  2  2  2  2  3  (3.1)  This relationship assumes that all of the VS destroyed is contained in microorganisms, which is not the case in a mixed primary and secondary sludge. It also assumes that m^rification is inhibited at thermophiUc temperatures. If nitrification is included, the equation becomes C H N0 + 70 => 5C0 + 3H 0 +N0"+IT + energy, +  5  7  2  2  2  2  3  (3.2)  which requires 1.98 kg 0 /kg VS destroyed (Matsch and Dmevich, 1977). Booth and Tramonti 2  (1983) found that 2.33 kg 0 /kg VS destroyed was required, and Trim and McGlashan (1984) 2  36  found that 3.3-3.5 kg C^/kg VS was required (both pure oxygen systems). Loll (1984) suggested that only 0.7-0.8 kg C^/kg VS was required, based upon German experience.  ©  0  4  8 Time  ' 12  16  20  | h ]  Time course of the oxygen uptake rate (OUR) during cultivation of aerobic thermophiles in sewage sludge at 6 5 ° C , 0.5 w m airflow, 1500 m i n " ' and p H 7. Phase 1, inactivation of non-therrriophilic microorganisms; phase 2, lag phase of the thermophiles; phase 3. exponential growth of the thermophiles; phase 4, oxygen-limited phase; phase 5, carbon-limited phase with a decrease in the activity of thermophilic biomass and'panial sporulation of thermophilic populations  FIGURE 11 - ATAD Oxygen Uptake Rate Over One Feed Cycle (Bomio, 1989)  3.2.3.2 Air Supply Efficient aeration is a very important parameter in successful ATAD operation. The system must transfer enough oxygen to the bulk hquid to satisfy the metabolic requirements of mermophilic bacteria without removing too much heat from the system, in the form of water saturated gas. Oxygen transfer efficiency (OTE) in ATADs has often proven to be higher than that measured with the standard ASCE aeration test. Jewell and Kabrick (1980) found that, when they measured oxygen transfer efficiency at 60 °C in water using the DeLaval aerator, it was only 2 to 3 percent. However, during operation at design temperatures with sludge, OTE always exceeded 37  12 percent and was sometimes as high as 23 percent. Jewell and Kabrick concluded that the ASCE standard tests would not necessarily reflect OTE in an ATAD system Wolinski (1985) measured transfer efficiencies as high as 100 percent, but his system was insulated by a deep biological foam layer which also exhibited an oxygen uptake. Booth and Tramonti (1983) reported efficiencies as high as 87 percent with a venturi aeration system Due to the difficulty in measuring OTE, design is usually based upon empirical values such as air flows with a given type of aeration system The EPA manual has quoted air flows required for sufficient aeration of an ATAD system of 4 (m air)/(hm of active reactor volume), assuming a feed VSS of 2.5 to 5 percent and a Fuchs aspirating aerator. Kelly (1990) suggests that air flow requirements for ATAD reactors are in the 0.5 to 2.5 volume of air/volume of sludge per hour (V/(Vh)) range, and quotes Wolinski as using 0.25 to 0.5 V/(Vh). The following ranges of airflow rates were measured in three Canadian installations: 0.46 to 0.94 V/(Vh) in Ladysmith; 0.8 to 1.0 V/(Vh) in Gibsons, and 0.5 to 1.2 V/(Vh) in Salmon Arm 3.2.3.3 Dissolved Oxygen Concentration Measurement of DO in ATAD systems poses the following problems: 1. Temperature. Many DO probes developed for use in biological systems do not have adequate temperature compensation above 45 °C. 2. High mixing energy. Probes mounted in ATAD's must be of rugged construction. 3. Low DO concentrations. Many probes have difficulty obtaining good accuracy at concentrations below 1 mg/L. Loll (1984) reported that the oxygen meters he used did not have adequate temperature compensation and the electrodes quickly wore out. Booth and Tramonti (1983) reported that a modified "phOx" (tradename) probe correctly recorded DO concentration in a water bath, but readings oscillated when the probe was installed in the ATAD sludge piping. Morgan et al. (1983) did not attempt to install a meter in their ATADs, but did do spot checks with an EIL oxygen meter calibrated at 50 °C. They were able to measure low dissolved oxygen concentrations, in the range of 0 to 7 percent saturation, using this method. 38  A few researchers reported success with Orbisphere probes developed in Switzerland. Jewell and Kabrick (1980) stated that the meter was only used for spot checks, and was developed especially for high temperature, high organic content applications. Morgan et al. (1983) also used the meter only for spot checks. Trim and McGlashan (1983) placed the probes in the recycle pipe to get good flow past the meter, with excellent results. The probe signal was used to control the flow of pure oxygen to the reactors. Routine maintenance helped to eliminate the only remaining problem; fats fouling the electrolyte. Varying levels of dissolved oxygen have been measured in full scale ATAD systems. The EPA manual quotes values from German experience of 0.7 to 3 mg/L and other measurements of 0 to 0.2 mg/L. Loll (1984) reports values of only 0 to 0.5 mg/L, and states that these are relatively inaccurate. Morgan et al. (1983) report values of 0.2 to 0.3 mg/L. Many of these values are below the EPA recommended minimum for aerobic sludge digestion of 2 mg/L, which Smith et al.(1975) also endorsed as a minimum value for good operation of a pure oxygen system Apparently most full scale ATAD systems operate under conditions of high oxygen tension, where the high amounts of oxygen suppUed are balanced by a very high oxygen uptake rate. 3.2.3.4 Oxidation Reduction Potential Oxidation reduction potential (ORP) is a measurement of the activity of oxidation-reduction reactions in an acqueous environment. ORP in a sewage sludge solution is affected by many parameters, including pH, DO concentration, NOx concentration and PO4 concentration (Peddle et al., 1988). ORP can also indicate the aerobic state of a solution. Koch et al. (1988) showed that for a Bio-P pilot plant, 50 to 100 mV could be interpreted as aerobic, -75 to -225 mV interpreted as anoxic, and -300 to -450 mV interpreted as anaerobic. This relationship is illustrated in Figure 12 from Kelly (1990). ORP values have been monitored in three Canadian ATAD facilities. At Ladysmith, ORP varied from -350 mV to 100 mV. At Gibsons, ORP ranged from -50 mV to -300 mV. These installations had ORP measured once per day just before feeding. At Salmon Arm, which had continuous ORP monitoring, levels varied from 0 to -300 mV. The pattern is reported to have 39  EARTHY  H U M U S  HUMUS  AMMONICAL  SWEETISH  S H A R P - P U N G E N T  FREE  MEASURABLE FREE  o <  o UJ  > £  NOT  PUNGENT (IRRITATING)  MEASURABLE  OXYGEN  PREFERRED  CONVENTIONAL  ?  OXYGEN  ACID  (NAUSEATING)  AEROBIC.  RANGE  CHGEST10N  OF  •200  .  OPERATION • FOR * THERMOPHILIC [AEROBIC  DIGESTION  100 UJ  S o . a. z 2 -100 o r> £ -200  OBLIGATE  AEROBIC  ANAEROBIC  DIGESTION  DIGESTION  z -300 i— <  FACILITATE  x -400 o  AND  Q  DIGESTION  (FERMENTATION"  AEROBIC  RESPIRATION)  -500. J. L_ TO  REDUCTION  NO  •  TO  H 0 2  REDUCTION  X  N  2  +  H 0 2  S O  REDUCTION  +  TO ORGANIC  H  2  S  +  H 0 2  REDUCTION  (FERMENTATION ACID.  CO2.  PRODUCTION) ,  FIGURE  REDUCTION  TO- C H  4  +  H 0 2  .  12 - Rektionship of Oxidatioii-Reduction Potential to Aeration State (Kelly, 1990)  been relatively constant with time except for drops during sludge feeding. It was also noted that the second ATAD in a series was always less negative (Kelly et al., 1993).  3.2.4 Alkalinity and pH 3.2.4.1 Alkalinity Alkalinity^is defined as the ability of a wastewater to neutralize acids, or the sum of all the titratable bases in a wastewater. These can include carbonate, bicarbonate, hydroxide, borate, phosphate, silicate and other bases (APHA, 1989). Alkalinity is an important factor in nitrification and denitrification reactions, which will be discussed in more detail in Section 3.7. 40  Alkalinity in ATAD reactors is high and is thought to be due to the high concentrations of ammonia present in an ATAD sludge. Other sources of allcahnity in ATADs are phosphoric acid, carbonic acid, and acetic acid. AUtalmity concentrations as great as 2000 mg/L were measured in the B.C. ATAD installations (Kelly, 1990). 3.2.4.2 pH pH is defined as the negative log of the activity of the hydrogen ion in solution. Many physical and biochemical processes in wastewater treatment are pH dependent and bacteria have optimum pH levels for growth. pH measurements are temperature dependent due to the response of pH probe components to temperature and the effect of temperature on chemical equilibrium. Low pH inhibits bacterial activity and most bacteria cannot live below pH 4. In aerobic digestion, respiration produces carbon dioxide which becomes carbonic acid in solution. If the sludge has low aUcafoiity, it will be poorly buffered and the action of respiration can cause the system pH to drop to the point where the biological system is inactivated. pH also has a great effect upon various physical and biochemical processes associated with nitrogen, which will be discussed in detail in Section 3.3. ATAD pH is higher than that of the sludge feed. Values reported by various researchers are summarized in Table 5. TABLE 5  ATAD pH Reported in Research Literature ATAD 1 ATAD 2 Feed Source Sludge Sludge Sludge PH PH PH Breitenbucher (1984) >7.2 >8.2 EPA (1990) 6.5 >7.2 >8.0 Jewell and Kabrick (1980) 7.0-7.8 Loll (1984) 7-9 Morgan et al. (1983) 5.2-5.7 7.4-7.7 Kabrick and Jewell (1982) 5.4-6.0 6.4-7.1  41  pH changes with time in an ATAD reactor, as shown in Figure 13 from Hamer (1987). This result agrees with the statement by Matsch and Drnevich (1977), that at temperatures above 45 °C, pH increases with detention time.  FIGURE 13 - Changes in pH, Dissolved Oxygen, Solids, and Dissolved Organic Carbon Concentrations with Time (Hamer, 1987)  Table 6 shows full scale operating aUiahnity and pH values for three Canadian ATAD installations (Kelly, 1990). TABLE 6 Location  Full Scale ATAD Alkalinity and pH Influent ATAD 1 Alkalinity pH AlltahTiity pH (mg/L) (mg/L) 4.8-6.8 5.7-7.9 7.2-8.6 4.6-5.7 8.0-645 4.6-7.3 139-1060 4.8-5.9 980-1730 6.8-9.1 360-1040 5.0-6.5 720-1820 6.8-8.6  ATAD 2 Alkalinity pH (mg/L) 6.6-8.3 274-3160 N/A 600-1389 7.7-9.1 785-1980 7.0-8.6  Banff© Ladysmith() Gibsons() Salmon Arm() ()Kelly, 1990 ©Schuster, 1994 When operating three digesters in series, pH in ATAD 3 ranges from 7.0 to 8.5. a  a  a  a  42  3.3 ATAD Supernatant Quality  3.3.1 Nitrogen Nitrogen occurs in wastewaters in the forms of organic nitrogen, ammonia, nitrite and nitrate, and nitrogen gas. Organic nitrogen is defined as nitrogen bound organically in the tri-negative oxidation state, and is found in proteins and peptides, nucleic acids, urea, and some synthetic compounds. (APHA, 1989) About 12.4 percent of the weight of an average bacteria is organic nitrogen, but the amount varies with the age of the cell. 3.3.1.1 Background Ammonia is produced by deaminization of organic nitrogen containing compounds. Two ammonia producing reactions are as follows (Metcalf and Eddy, 1991): COHNS + 0 + nutrients => C0 + NH + C N N0 + other end products 2  2  3  5  7  C H N0 + 50 => 5C0 + 2 H 0 + NH + energy 5  7  2  2  2  2  (3.3)  2  (3.4)  3  In the above reactions, 3.57 g of alkalinity is theoretically produced per g of organic nitrogen rnineralized to ammonia (Bishop and Farmer, 1978). Ammonia is present in solution as either ammonia or the ammonium ion, the two forms being in equilibrium and the dominant form being dependent upon pH as illustrated in Equation 3.5. NH + H 0 <=> NH+ OFT 3  2  (3.5)  4  At pH greater than 7, more ammonia is in solution, and at lower pH more ammonium ion is in solution. At high pH, in the range of 10.5 to 11.5, significant amounts of ammonia can be air strippedfromsolution. Temperature also affects the equiUbrium balance. At higher temperatures, less ammonium ion is present at a given pH than at lower temperatures. Nitrate + nitrite (NOx) are produced by the nitrifying bacteria, Nitrosomonas and Nitrobacter. They are autotrophs, requiring C0 as a carbon source. The overall reaction can be described as 2  (Metcalf and Eddy, 1991): NH + 1.830 + 1.98HC0 => 0.021C H NO + 0.098NO" + 1.041HO + 1.88HC0 +  3  2  3  5  7  2  3  2  2  (3.6)  43  3  This reaction theoretically consumes about 4.3 mg 0 and 8.64 mg HCO3" per mg of NH 2  3  oxidized to NO3 (Metcalf and Eddy, 1991). Bishop and Farmer (1978) found an alkalinity consumption range of 6 to 7.4 g as CaCCtyg ammonia nitrogen oxidized. The optimal pH range for nitrification is between pH 7.2 to 8.4. At pH 7.0, nitrification rates are only about 47 percent of the rmximum rate, and at pH 6.0 the nitrification rate is only 14 percent of the rmximum rate (Bishop and Farmer, 1978). Metcalf and Eddy (1991) state that a minimum DO concentration of 1 mg/L is also required hut Peddie et al. (1988) found that nitrification could take place at DO concentrations less than 1 mg/L. High concentrations of ammonia can inhibit nitrification, but experiments done by Elefsiniotis (1989) showed that a pilot scale activated sludge system can successfully nitrify an influent ammonia concentration of up to 260 mg/L. Nitrifiers reproduce relatively slowly as compared to aerobic heterotrophs, so a nitrifying system requires a longer sludge age than one which is only oxidizing biodegradable carbon. NOx can be reduced to nitrogen gas by denitrifying bacteria in the absence of oxygen and in the presence of readily biodegradable carbon. Bacillus is one of the bacteria which can use NOx as a final oxygen acceptor when the absence of oxygen triggers the denitrification enzyme system (Metcalf and Eddy, 1991). Denitrification can be modeled as: N0 " + I.O8CH3OH + H+ => 0.065C H NO + 0.047N + 0.76CO + 2.44 H 0 3  5  7  2  2  2  2  (Metcalf and Eddy, 1991) (3.7) The optimum pH range for denitrification is between about 6.5 to 7.5 (EPA, 1975). For the above reaction, 3.57 g of alkalinity is theoretically generated for every gram of nitrate nitrogen reduced, but experimental values are more on the order of 3.0 (Bishop and Farmer, 1978). Bishop and Farmer also noticed that denitrification could occur when DO dropped below 1 mg/L. Peddie and Mavinic (1988) showed that, when sludge digestion was done on an anoxic/aerobic cycle, the point at which nitrates were consumed by the denitrifiers was marked by a change in the slope of the oxidation/reduction potential curve (point E, Figure 14). Peddie and Mavinic also noted that, upon beginning re-aeration, ammonia was initially quickly oxidized to NO3. Once ammonia levels fell to about 1 mg/L the oxidation rate decreased while  44  organic N was gradually converted to NH then to NO3; also, at the point of the oxidation rate 3  change, there is a slight disturbance in the slope of the ORP curve (point B, Figure 14). 10  -r  :  —  1  :  9 -'  -3  •"f  1—  :  0  r  100 — - O R P avg dORP/dt  r  1  1  200 Elapsed Time (min) DO  1  1  300  * TKN.  1 400  N03  a  -  NH3  FIGURE 14 - Anoxic/Aerobic Sludge Digestion (Peddle and Mavinic, 1988)  3.3.1.2 Concentrations of Nitrogen Forms in ATADs Ammonia concentrations in ATAD digesters are high, because the organic nitrogen content of the biomass is deaminized as shown in Equations 3.3 and 3.4. Mason et aL (1987b) repeatedly observed an increase in ammonia concentration after hemophilic aerobic digestion of a yeast cell solution. Cairington et aL (1991) reported that, with a total kjeldahl nitrogen (TKN) of 1700 mg/L and NH3 of280 mg/L (16.5 percent of TKN) in the influent raw sludge, the resulting TKN in the ATAD digester was 1800 mg/L and NH3 concentration was 680 mg/L (37.8 percent of TKN) with 3.8 percent TS concentration in the digester. Murray et aL (1990) measured 1330 mg/L TKN and 298 mg/L NH (22.4 percent of TKN) in the Haltwhistle ATAD at 2.53 percent 3  VS.  45  Total TKN in the digester may be lower than the feed sludge TKN since high temperatures and high alkalinity in the ATAD environment may cause some of the ammonia released to solution to be stripped in the off-gas. Various sources state that nitrification is inhibited at high temperatures, explaining why the ammonia concentration increases during thermophuic aerobic digestion rather than decreasing, as during mesophilic aerobic digestion. Several sources have stated that nitrification is inhibited at temperatures greater than 40 °C (EPA., 1975, EPA, 1990, Matsch and Drnevich, 1977). Surucu et al.(1976) found zero nitrate concentrations in their systems even when a 2 mg/L DO was maintained. Tyagi et al. (1990) however, did record nitrate (as listed in Table 7) in their U-shaped bioreactor, which reached final temperatures of 53 and 60 °C. TABLE 7 Nitrates Measured in U-Shaped Bioreactor Aeration Time Influent Concentrations Effluent Concentrations (mg/L) (mg/L) (days) VS NFL( NO^ VS NFL, NO^ 3 19430 106 7.7 13200 279 28 22400 61 28 20000 267 40 2  Tyagi et al. (1990) concluded that, although nitrification was almost totally inhibited at those temperatures, some nitrification did still occur. 3.3.2 Phosphorus Phosphorus measurements in full scale ATAD systems have not been extensively documented. Besides the total phosphorus measurement recorded at the Salmon Arm plant of 848 mg/L, Carrington et al. (1991) measured total phosphorus at 610 mg/L in the raw sludge influent and 590 mg/L in the Harrowgate South TAD.  46  3.3.3 Volatile Fatty Acids Volatile fatty acids (VFA) are short chain carbon compounds formed in nature primarily by fermentative processes, which break down organic molecules and produce simpler organic end products. Fermentative bacteria use the organic molecules as final electron acceptors. Not much ATP is produced by this metabolic pathway as compared to aerobic metabolism. Most of the energy generated by fermentation stays in the chemical bonds of the end products; so fermentative bacteria do not compete well in highly aerobic environments. Therefore, fermentation is not likely to occur under aerobic conditions, since many fermentative bacteria are facultative and will preferentially use aerobic respiration if DO is present. Some fermentative bacteria are obligate anaerobes and cannot function at all in the presence of DO (Tortora et al., 1989). Fermentation can take place in the themophilic temperature range of 49 to 57 °C (Metcalf and Eddy, 1991). Volatile fatty acids have been measured in the ATAD environment. Casey (1987), reported a significant production of VFAs in ATADs under low DO conditions. Mason et al. (1987a) reported VFA production under aerobic and oxygen limited conditions (<10 percent saturation), but no VFA production under oxygen excess conditions (>30 percent saturation). These researchers measured acetate concentrations of between 1400-2600 mg/L. Proprionate, (200-709 mg/L) isobutyrate, (100-300 mg/L) butyrate, (100-200 mg/L) isovalerate (50-200 mg/L) and valerate (20-100 mg/L) were also present. Sonnleitner (1983), identified Clostridium thermoaceticum as one type of mermophilic bacteria which can produce 2 moles of acetate per mole of glucose consumed, when growth conditions are favourable (pH of 7 and an ORP less than -360 mV). Hamer (1987) measured the VFA concentration changes with time over a 72 hour period with low DO concentrations. During Hamer's experiments, acetic acid concentrations reached a peak of 6000 mg/L then fell to zero with time. Proprionic acid followed a pattern similar to that for acetic acid, although delayed and peaking at about 1000 mg/L. Both Hamer (1987) and Mason (1987a) speculated that the formation of VFAs occurred as a result of fermentation by facultative anaerobes under oxygen limited conditions. 47  VFA concentrations in the Salmon Arm digesters were measured over a period of time. The results, as a range of values, are summarized in Table 8 (Kelly, 1990). TABLE 8 VFA Concentrations Measured in Salmon Arm ATADs Concentration Range Volatile Fatty Acids (mg/L) 53-790 Acetic Proprionic <10-755 Iso-Butyric <10-345 Butyric <10-160 2 Methyl Butyric <10-160 3 Methyl Butyric <10-280 Valeric <10-210 Hexanoic <10-65  At the Banff wastewater treatment plant, VFA concentration measurements were as high as 2500 mg/L in the first ATAD in series and 1500 mg/L in the second ATAD. This soluble organic material, when returned to the head of the plant after sludge dewatering, increased the load on the Uquid treatment system Increasing the size of the aerator motors (and thus increasing air flow) dropped the VFA concentrations in the ATADs to below 200 mg/L (Reid Crowther, 1994). Recent work by Chu et al. (1994), confirmed that ATAD VFA production was directly linked to digester air supply and also to ORP trace patterns. Figure 15fromChu et al (1994) shows how acetate concentration increased then fell to near zero during a period of low ORP values at an airflow rate of 0.28 V/(Vh). The low acetate concentration corresponded with a sudden increase in ORP values.  3.3.4 Chemical Oxygen Demand Chemical oxygen demand (COD) is defined as the oxygen consumed by organic compounds which can he oxidized by potassium dichromate in an acidic medium using a silver sulphate catalyst at elevated temperatures. COD is reported in mg/L as oxygen. Not aU COD can be 48  .  150-j 100 50 -  0 -  >  J, CL CC  -5030  -100  -  o  a E  O  -150-200-250-300  -  10.0  15.0 Time (h)  B.  0 * 0.0  5.0  10.0  15.0  20.0  25.0  Time ( h )  Acetate  Propionate  —Isobutyrate  FIGURE 15 - Changes in Volatile Fatty Acid Concentrations in an ATAD with Time Compared to ORP Trace Patterns (Chu et al., 1994)  oxidized biologically. The only interference to the test which may be relevant to this research is thatfromnitrite, which can produce 2.2 mg COD per mg nitrite. Ammonia does not interfere with the COD test unless chloride levels are high, which is not usually the case with domestic sewage. Volatile fatty acids contribute to COD as follows (Eastman and Ferguson 1981): 49  Acetic acid  1.066 g COD/g acid  Proprionic acid  1.512 g COD/g acid  Butyric acid  1.816 g COD/g acid  Valeric acid  2.037 g COD/g acid  Organic nitrogen accounts for 9.58 g COD/g organic N and cells account for 1.42 g COD/g VSS (Eastman and Ferguson, 1981). Significant COD reductions can be achieved in ATAD digesters. Kelly (1990) reported COD reductions generally in excess of that predicted by the Koers-Mavinic curve (EPA, 1979). When designing the Whistler, B.C. ATAD installation Kelly (1991) designed for 25 to 30 percent COD reduction in the first ATAD tank, and subsequent smaller reductions in the next two tanks, resulting in an overall 40 to 50 percent COD reduction. Murray et al. (1990) reported 50 percent average COD reduction at Haltwhistle. Trim and McGlashan (1984) reported 20 to 35 percent COD reduction at Johannesburg. Morgan and Gunsen (1987) reported 2 to 2.6 kg COD removed/kg VS oxidized at Ponthir.  50  4.0 EXPERIMENT DESIGN 4.1 Objectives  The main objectives of this research were: 1. To determine to what extent nitrogen and phosphorus in Bio-P sludge would release to solution in a pilot scale ATAD system operating at different air supply levels. 2. To predict the effect on full-scale wastewater treatment plant loading of supernatant recycle from ATAD sludge. The pilot scale experimental apparatus was designed to match as closely as possible a full scale sludge treatment system. Solids, nitrogen and phosphorous balances defined the main sludge and supernatant characteristics of interest. Other parameters were also monitored, to define the operating conditions within which the balances were made. Three different operating conditions were chosen based upon aeration state. Aeration was the parameter varied because of the profound effect of dissolved oxygen concentration upon the operation of biological nutrient removal facilities and upon the handling of Bio-P sludge. The characteristics of each operating condition will be described later in this section, but for the purposes of the following discussion, they are designated as follows: 1. Oxygen excess. (OE) Thefirstand last experiments (OE1 and OE2) were done under this condition, with higher air rates being applied during OE2. 2.  Oxygen deprived.  3.  Oxygen satisfied.  (OD) The second experiment was run under this condition. (OS) The third experiment was run under this condition.  4.2 Apparatus  The apparatus was designed to be a pilot scale model of a typical sludge treatment facility for a biological phosphorus removal (Bio-P) plant. Both primary and secondary sludge were digested together in a roughly 50/50 volume ratio. Primary sludge was gravity thickened and secondary sludge was thickened by a bench scale gravity belt thickener. The two pilot scale ATAD reactors were operated in series, as is usual practice in full scale plants. 51  4.2.1 Primary Sludge Collection and TJiickening The source of primary sludge was the raw sewage storage tanks of the University of British Columbia (UBC) pilot plant. The Environmental Engineering Department at UBC operates a pilot scale wastewater treatment plant which treats domestic sewagefromthe student residences. Raw sewage is pumpedfromthe municipal sewer system to continually mixed storage tanks which are periodically dosed with sodium bicarbonate. During these experiments, raw sewage was pumpedfromthe storage tanks to the primary tMckening process, shown in Figure 16. The primary thickening system consisted of: •  R a w Sewage P u m p :  •  P r i m a r y Clarifier:  • • • •  •  controller.  overflow weir  Moyno SP34401, 0.56 kW 1/60/110 DC motor with variable speed  540 L, equipped with a rotating bottom rake and supernatant  P r i m a r y Sludge P u m p : Moyno SP33101, 0.56 kW, 1/60/110V DC motor with variable speed controller. G r a v i t y Thickener: 200 L, operating volume 125 L, equipped with a rotating bottom rake and supernatant overflow weir Exhaust Blower: Dayton Model 2C782 Thickened P r i m a r y Sludge Pump: Moyno SP33101, 0.56 kW, 1/60/110V DC motor with variable speed controller. P r i m a r y Sludge Dosing T a n k :  70 L Plexiglass cylinder graduated in 1 liter increments.  To collect and thicken enough primary sludge for these experiments, raw sewage was pumped continuously at a rate of about 5.9 L/minfromthe storage tanks to the primary clarifier. Primary sludge was removed periodicallyfromthe clarifier by the primary sludge pump operating on a timer set for 6 minutes on and 10 minutes off. The sludge was fed to the gravity thickening tank at a rate of 1.5 L/rnin. The gravity thickener rake was set to rotate at approximately 0.5 r/min (revolutions per minute) during this operation. The tank head space was contmually vented by a fan, which discharged to piping leading outside of the pilot plant trailer. Primary sludge was allowed to collect and thicken for 24 hours. For thickened primary sludge removal the rake rotation rate was increased to approximately 2 r/min, and thickened sludge was pumpedfromthe bottom of the tank at about 1.7 to 2.6 L/min. by the thickened primary sludge pump to the primary sludge dosing tank. This tank was used to measure the volume of primary sludge fed to the ATAD digesters. Usually, all the primary sludge collected in 24 hours was 52  1  needed to feed the digesters, so the average solids residence time (SRT) in the gravity thickener is estimated at 24 hours. 4.2.2 Secondary Sludge Collection and Thickening Secondary sludge was also provided by the UBC pilot plant. This facility is a University of Capetown (UCT) Bio-P process, which is fed by the raw sewage storage tanks described above. Phosphorus rich waste activated sludge (WAS) was wastedfromthe process daily and processed by the secondary sludge thickening mechanisms shown in Figure 17. Secondary sludge was thickened separately to prevent premature release of phosphorous. Popel and Jardin (1993) quoted other work which showed PO4 concentrations in supernatantfrommixed sludge thickeners rangingfrom60-100 mg/L, a significant release. The secondary sludge thickening process equipment consisted of: • • • .  Wasting Tank: 300 L. Settled WAS Pump: ITT Jabsco Model 36680-2 Electric Bilge Pump, 12V DC motor Belt Thickener Feed Tank: 200 L, with rotating sludge rake/mixer. Thickened Secondary Sludge Pump: Moyno SP33101, 0.56 kW, 1/60/110V DC motor with variable speed controller. • Gravity Belt Thickener: 0.029 kW variable speed motor, 0-2.5 r/min. • Secondary Sludge Dosing Tank: 40 L Plexiglas graduated in 1 L increments. Activated sludge was wastedfromboth aerobic zones of the UCT process and allowed to settle in the wasting tank for approximately 1 hour. Settled sludge was pumped to the belt thickener feed tank. This feed sludge was kept mixed while it was being pumped to the gravity belt thickener at a rate of about 1 L/s. The thickener consisted of a 300 mm wide cotton belt 1200 mm long, reinforced with plastic mesh, running over two rollers driven by a variable speed DC motor. Sludge was fed onto the upper belt surface; Uquid dripped through the moving belt and was coUected in a tray between the upper and lower belt surfaces. The tray connected to the plant drain. The returning belt surface was washed with water jets and partiaUy dried by compressed air jets to keep the belt from plugging during operation. Thickened secondary sludge was scraped off the belt by a plastic scraper which fed a dosing tank similar to that used for primary sludge. 54  ><  Q UJ , Z O OQ O Z> < UJ —1 O CO CO I- <  >-  9  Ct.  <  Q UJ o LU _J O < CO CO O f-  I I I I II I I I I I ca  or  fi  LU  cu  o  XI  o  CO LU m  fi  CD  - t J  w  <  cn  CO  o  cm  cl  •pH  n  O  a  o X! E-H  cu GO XI 1—1 CO  ti Pi O 5*: z  o z F= CO  <  55  o  CU CO  To reduce the number of variables in the experiment, no polymers were used to help thicken the secondary sludge. The amount of time between wastingfromthe aerobic zone and feeding to the ATAD digesters was minimized to prevent the secondary sludgefrombecoming anaerobic and releasing large amounts of stored phosphorus. Mechanical thickening took approximately one hour; much less than the 10 hour n^ximum for minimizing P-release quoted by Popel and Jardin (1993). Figure 18 shows photographs of the secondary sludge gravity belt thickener.  4.2.3 Autothermal Themophilic Aerobic Digesters 4.2.3.1 Digester Description This process consisted of two ATADs operating in series as shown in Figure 19. Each consisted of an inner stainless steel tank, an outer insulated fiberglass tank and tank lid, a mixer/aerator, an air supply system and a foam cutter. To waste digested sludge and transfer sludge between tanks there was also a small, 21 L transfer tank and a Masterflex Model 07585-50 hose-pump. The inner ANSI 304 stainless steel tank was 610 mm deep and 518 mm in diameter, for a total volume of 128.6 L. The inner tank fitted inside an outer fiberglass tank 737 mm deep and 610 mm in diameter, leaving an air space between the stainless steel tank and the fiberglass jacket. The jacket had fittings for piping, since it was originally intended as part of a heatmg/cooling water bath system for temperature control if necessary. Temperature control of that type was not needed for these experiments, and the air space became extra insulation. The fiberglass jacket was insulated with 10 mm thick closed cell foam The fiberglass lid was also insulated with the same closed cell foam and bolted to the flanges of the other two tanks. The lid seal was a neoprene gasket. There were several openings in the lid: a gasket sealed inspection hatch with quick release levers; a larger hatch, also gasket sealed and removable but bolted on, upon which the foam cutter was mounted; three tapped pipe fittings for mounting probes; one tapped pipe fitting for the gas vent; and the hole for the aerator shaft. The aerator shaft passed through a hole in a round aluminium hatch. The hole was sealed by an O-ring 56  F I G U R E 18 - Gravity Belt Thickener  57  cd cu XJ o  CO  htxH^i  Oi  cu -4->  P4 PH  o  w CO Q  % cu i-H  cd o co •P  o  i—i  •rH  PH  33a m s AuvaNOoas Q3N3)HOII-LL  3oams Q3N3»OIHi  58  mounted in the hatch; grease on the shaft completed the seal and allowed the shaft to rotate easily. This hatch was gasket sealed to the lid and could be removed with quick release levers. The mixer/aerators were modified versions of the Turborator axial flow aerator, manufactured by Turborator Technologies Ltd. Rotation of an impeller submersed in the fluid to be aerated creates a vacuum in the centre of the impeller and sucks air down the shaft. The air is forced out of the impeller and sheared by the rotating impeller blades into very small air bubbles. The aerators were belt driven with a 1 to 1.5 sheave ratio by variable speed 0.75 kW DC motors, controlled by Leeson and Bronco DC variable speed controllers. Rotatingfittingswere screwed onto the top of the aerator shafts to allow connection of air hoses. Compressed air wasfirstregulated to 10 to 15 kPa, then passed through Cole-Parmer flow meters before entering the shaft of the aerator. Setting the reading on theflowmeters controlled the volume of air entering the aerator. To control foam formation, each ATAD was equipped with a foam cutter. This consisted of a 250 mm diameter axial fan mounted horizontally inside the tank below the vent hole so as to blow air downwards into the tank. The blade was driven by a variable speed DC motor, 0 to 1800 r/min. Piping between the various systems and tanks was generally of 25 mm diameter PVC or of flexible hose; valves were PVC. The exceptions were those pipes andfittingsexposed to high temperature sludge, which were of polypropylene. Figure 20 shows a photograph of the pilot scale ATAD digester system. 4.2.3.2 Digester Operation The ATADs were fed once per day and operated on a batch basis as recommended by the EPA (1990). Digested sludge was first pumpedfromATAD 2 to the transfer tank, the volume of sludge was recorded, and then wasted to drain. The level of the sludge outlet pipe inside each ATAD was set so as to ensure a constant volume of sludge remaining in the digester after each sludge withdrawal. This method helped to maintain a constant sludge age in the digesters and avoided variance in digester operating volume resultingfromevaporation. 59  F I G U R E 20 - Pilot Scale A T A D System 60  Partially digested sludge was next pumped from ATAD 1 into the transfer tank, the volume was recorded, and the sludge was pumped into ATAD 2. Sludge volumes remahiing in the transfer tank and pipes were measured and recorded to minimize errors in mass balance calculations. Finally, well mixed thickened primary sludge was pumped into ATAD 1, followed by thickened secondary sludge. The two sludges were fed separately to avoid premature phosphorus release in the secondary sludge when exposed to the anaerobic primary sludge. The entire feeding procedure took approximately 0.5 hours. During sludge withdrawal, the rotational speed of the aerator/mixers was turned down to 30 percent of the rmximum setting on the speed controllers; this helped avoid vortexing, which would change the Uquid level in the vicinity of the sludge outlet pipes and have a great effect on volumes withdrawn. Rotational speed was turned up again as new sludge was pumped into each tank. As noted above, no external heating was required in this system: mixing energy and energy generated biologically provided sufficient heat to maintain the desired temperature, as experienced in full scale systems. 4.2.4 On-line Monitoring Each tank contained four probes: one temperature probe, one dissolved oxygen (DO) probe, and two oxidation-reduction potential (ORP) probes. The output from these probes was recorded by a data logging program ruiming on a personal computer. For the OE1 and OD experiments, the program was Bioguide, a product of BioChem Technologies, running on an IBM compatible 486DX33 computer. For the OS and OE2 experiments the program was Labtech Notebook, running on an D3M compatible AT 286 equipped with a 12 bit resolution PC Labcard 812 Data Acquisition card. In both cases, probe values were recorded by the programs once per minute. During the OS and OE2 experiments, the program sampled the dissolved oxygen probe measurements every 10 seconds and recorded the average value once per minute.  61  4.2.4.1 Temperature Monitoring  Each A T A D was equipped with a temperature probe. The probes were constructed at U B C using a temperature sensitive semiconductor (LM35CAZ). These probes have a range of-40 °C to 110 °C, and an accuracy of ± 1 °C. Probe output was periodically checked with the readings from an alcohol thermometer lowered into the tank. Readings were generally within 2 °C and accuracy was probably better than that, since it was difficult to read the probe inside the tank and the thermometer reading changed rapidly once the thermometer was removed from the tank.  4.2.4.2 Oxidation Reduction Potential Monitoring Each A T A D was equipped with two Oxidation Reduction Potential (ORP) probes. ORP la and 2b were Broadley-James Model F-900 ORP Fermprobes, with gelled KCl/supersaturated KC1 crystals in the salt bridge, reference type Ag-AgCl half-cell, double junction sealing and a platinum sensing tip. Each probe can produce a mV signal in the range of-5000 to 5000 mV, with a temperature range of-5 to 135 °C. After the OE1 experiment (due to the large (lifference between the two probes), one of the probes was considered faulty and replaced with a new Broadley James F-900. Tank two had the same probes for all four experiments. ORP 2a was a Broadley James F-900, and ORP 2b was a Sensorex Model S653. Accuracy of these probes is demonstrated by the agreement of their readings. The two probes in A T A D 2 generally agreed within 10 mV, while the probes in A T A D 1 were usually within 30 mV of each other.  4.2.4.3 Dissolved Oxygen Probes As stated in Chapter 3, measurement of dissolved oxygen in A T A D tanks is difficult. Experience gained during these experiments confirmed the results of previous researchers. YSI Model 54 D O meters, with Model 5739 probes, calibrated well in a water bath but when placed in the experimental reactors began to oscillate within one day, possibly due to excessive deterioration of the probe anode. These probes were accurate as long as they were not kept in the A T A D environment for very long, so were used to check the probes that werefinallychosen.  62  Spot checks were done before and after feeding during the OS experiment, and before feeding during the OE2 experiment. When conducting these experiments, the Oxyguard dissolved oxygen probe was used for inline monitoring. This probe did not require a meter, and produced a mV signal directly in proportion to the concentration of dissolved oxygen in the probe environment. The membrane was thick and housed in a rugged casing with no protrusions, and thus worked well in the high energy rnixing environment of the pilot scale ATADs.  4.2.4.3.1 DO Probe Cahbration The probes were calibrated by mimersing them in an aerated, heated water bath. For the first cahbration before the OE1 experiment, a YSI DO probe was also placed in the water bath along with the Oxyguard DO probe. Saturated oxygen values were calculated using the equation given in Standard Methods 4500. The equation was extrapolated beyond the recommended 40 °C limit, due to lack of better data. Voltage readings from the Oxyguard DO probe were recorded along with the YSI DO probe readings and the temperature of the water bath. After the OE1 experiment the cahbration was repeated, this time checking with Winkler tests to confirm that the water in the bath was indeed saturated with oxygen. The Winkler tests were not repeated in subsequent calibrations because the initial check confirmed that the cahbration apparatus was capable of producing oxygen saturated water. The probes were calibrated in the water bath between the temperatures of 20 and 70 °C, before and after each experiment. The voltage output at 0 mg/L DO was also recorded. A cahbration curve which calculated mV/(mg/L DO) was generated based upon variations with temperature. The curves were different between the beginning and end of each experiment; therefore, the cahbration which most closely matched the spot checks was used to generate mg/L values to match the mV output. Using this cahbration method, the agreement between the YSI DO probes and the Oxyguard DO probes was usually within 0.5 mg/L. The probe manufacturers claimed that probe response was linear up until 45 °C and the assumption made during these  63  experiments, (confirmed by the spot checks), was that probe response would be linear above 45 °C as well.  4.2.5.3.2 Probe Response to Carbon Dioxide For the OE1 experiment, there was a DO probe only in ATAD 1. For the OD, OS and OE2 experiments, there was a DO probe in each ATAD. During the OD experiment, it was noted that the DO probes did not read 0 mV when the system was expected to be truly anaerobic; instead, they read between 3.0 and 4.9 mV, and 1.4 to 2 mV respectively for Probe 1 and Probe 2. Since these readings equated to 0.6 to 1.0 mg/L DO and 0.3 to 0.4 mg/L DO respectively, and the probes responded to the presence offreeoxygen as expected, the discrepancy was noted, but regarded as not significant. During the acclimatization period for the OS experiment, a further discrepancy was noticed after the DO probes had been cleaned and the electrolyte changed. The probes were reading 12 mV, the equivalent of over 2 mg/L DO, when a YSI DO probe measured 0 mg/L DO. Various checks were done, mcluding checking that the probes read 0 mg/L at high temperatures in deoxygenated water. Discussion with the manufacturer revealed that the probes had a history of responding to the presence of C 0 in the measurement medium, as well as to dissolved oxygen. 2  Further testing showed that, over time, the probes would gradually desensitize to the presence of C 0 in the ATAD reactors. This characteristic partially accounted for the minimal deviation 2  observed during the OD experiment (where the Oxyguard DO probes had been operating with the same electrolyte for several days before a spot check exposed the deviationfromactual values). Another difference was that the pH of the newly prepared electrolyte was lower than that used during the OD experiment; higher pH also desensitized the probes to the presence of C 0 . After 2  a series of experiments with different electrolytes, the electrolyte was changed to a 100 mg/L KI solution. The probes still responded to the presence of C 0 but with decreased sensitivity, and 2  the small error thus introduced was considered acceptable because changes in DO were of more interest during the experiments than absolute values.  64  4.2.4.3.3 Data Loss Urjjfortunately, during the OS and OE2 experiments a mistake in the data logging programming caused the probe in A T A D 1 to record on both the channel for A T A D 1 and the channel for A T A D 2. Therefore, the only DO values recorded for A T A D 2 during those experiments are the readings from the YSI D O probe spot-checks, which indicate the general trend in A T A D 2 during the OS and OE2 experiments. Since the correct information was available for viewing during the experiments (it was just not recorded), and there is the backup data of the YSI D O probe spot checks (plus the ORP curves), the data loss did not seriously effect the conclusions of this research.  4.2.4.3.4 Accuracy For D O concentrations greater than 1 mg/L DO, the Oxyguard D O probes were accurate to within 0.5 mg/L D O as measured during the OS and OE2 experiments by comparison with YSI D O probe readings. Due to the interference by carbon dioxide, D O levels could not be accurately measured below 1 mg/L. Accuracy as stated by the manufacturer is ± 2 percent of the reading within 5 to 40 °C.  4.3 Experimental Methods  4.3.1 General In biological nutrient removal plants and in handling of Bio-P sludge, phosphorus storage and release is profoundly affected by sludge dissolved oxygen concentration. It seemed possible that, if there were any thermophilic Bio-P bacteria, their phosphorus storage mechanism may also be affected by the D O concentration in their environment. Therefore, nutrient balances were done around the system described above for three different aeration states.  4.3.2 Aeration States Three different aeration states were induced in the A T A D s during the experiments.  The three  states were defined by a combination of ORP and D O trace patterns from the m-situ probes in 65  each tank. Air flow per mg VSS fed to the reactors per day and discharge gas composition also helped to define the aeration state of each experiment. 4.3.2.1 ORP and DO Target Traces The target ORP/DO patterns for each experiment are shown in Figure 21. During the OE1 and OE2 experiments, the goal was to keep ORP and DO always positive and, if possible, keep ORP greater than 100 mV and DO greater than 2 mg/L. During the OD experiment, the object was to keep DO always at 0 mg/L, and to keep ORP below 100 mV at all times in ATAD but to allow ORP in ATAD 2 to begin to rise at the at the end of the feeding cycle. Preliminary experiments had shown that, unless an ORP rise occurred, there would be a buildup of organic acids in the system with a resulting pH drop below the usual ATAD levels. During the OS experiment, the ORP and DO in ATAD 1 were kept low (less than -200 mV and 0 mg/L respectively) for about half of the feeding cycle and allowed to rise for the other half, and were kept high in ATAD 2. This condition would try to just satisfy the high oxygen demand in ATAD 1, while keeping ATAD 2 in oxygen excess conditions. 4.3.2.2 Air Flow and Discharge Gas Composition Air flow was measured using Cole Parmer flow meters. Air flows were kept constant for the OE1, OE2 and OD experiments, but were adjusted during the OS experiment, since the solids loading to the reactors was obviously changing and the intent was to maintain a constant air flow/(VSS fed/day) during each experiment. Discharge gas was sampled to compare levels of oxygen and carbon dioxide between the four experiments, to help confirm the difference in aeration states. 4.3.3 Experiment Execution Before each experiment, the air flow levels were set until the target DO and ORP traces were obtained, then the ATADs were run at that aeration level for one solids retention time (SRT) to acclimatize the reactors to that condition. The ATADs were then operated under those 66  Ci/Sui)  (T/Sui)  oa cs  NO  o  NO  _  ^  (T/SUI)  oa <N  T f  NO  O  oa  rj-  (S  O  2  <u  .* u  TJ V  ON  ON  en  •J3  P< <u Q  CS CO  a  J3 ^—^  5  O  5 o o  o o  o  o o  o o I  o o I  fl WD  O  o  5  5 o o  o o I  o o  o  o I  I  o  o I  o  o  o o  I  I  O O O O O o o o o o o  (T/Sui)  (T/Sui)  oa  t  Z  oa  • *  NO  o o  (q/Sui) NO  O  -*  oa <N  O  0  -a  -a  09 KI  C us  u H W  ••a  fi S3  I  o  s  « a  5  E  1  o  O  1 o o o o (S  o  o  o o o o o o o cn T f  —i I  am  I  a H  cmo  drao  am  9  o  NO  I  I  o o  o o  o  o  o o o o o o o I  I  I  dHO  I  o o  o o  o  o  o o o o o o o I  am  67  I  I  I  conditions for a further period of two SRTs during which samples were taken and analyzed. The results discussed in Chapter 5 are based upon the two SRTs of stable operation. Stable operation was generally indicated by similar DO and ORP traces for the entire period. The one exception was the OD experiment, which required an extra 3 days to stabilize and was followed by a power outage, which stopped the experiment after only 1.5 SRTs of stable operation. However, analysis of the OD experiment results showed no substantial difference between the 1.5 SRT period and a 2 SRT period including some of the "unstable" days, so the entire 2 SRT period was used for comparison in Chapter 5. The experiments took place during the foUowing periods: 1. OE1 : January 11 to January 22, 1993 2. OD : February 23 to March 6, 1993 3. OS : April 5 to April 16, 1993 4. OE2 : May 4 to May 15, 1993 4.4 Sampling and Sample Preservation 4.4.1 Sludge Samples 4.4.1.1 Sample Collection Samples of sludgefromeach ATAD were collected once per day during the feeding procedure. Samples were takenfromthe outlet pipe of the transfer pump after at least 10 L of sludge had been pumped. Thickened primary sludge samples were collectedfroma connection on the pipe feeding ATAD 1 after at least 6 L of sludge had been pumped. The connection was rinsed with a representative sample of the thickened primary sludge before collecting the sample. Thickened secondary sludge samples were collectedfroma connection on the secondary sludge dosing tank after the contents had been well mixed and the connection rinsed with a representative sample of the thickened secondary sludge. All sludge sample volumes were 500 mL.  68  4.4.1.2 Sample Preservation Sludge samples were stored at 4 °C for about 2 hours, then further prepared in the foUowing order: Primary, Secondary, ATAD 1 and ATAD 2. Each sample wasfirstblended with a Braun Multipractic Hand Blender until fairly homogenous, then separated into three portions. Using a graduated pipette with a 6 mm wide mouth, 10 mL was withdrawnfroma portion while it was being mixed with a magnetic stirring rod. The 10 mL aliquot was placed in a 250 mLflaskand the volume made up with distilled water. A 60 mL sample of the well-mixed 1/25 diluted sludge was thenfrozenat -10 °C until further analysis was possible. Three 1/25 dilutions were made up for each sample.  4.4.2 Supernatant Samples 4.4.2.1 Sample Collection Immediately after collection, approximately 100 mL of each type of sludge (Primary, Secondary, ATAD 1 and ATAD 2) was centrifuged at 12500 r/min for 20 minutes in a Sorvall Superspeed Model SS-1 centrifuge. The supernatant was collected and preserved, then filtered through 0.45 micron cellulose acetate filters. Primary and secondary supernatant were first filtered through Whatman 934AH glassfiberfilters.These sludges dewatered readily, and the filtrate was stored at 4 °C within 2 hours of initial sample collection. The ATAD samples took much longer tofilterand it was often 5 hours before enoughfiltratewas collected for analysis. Unfiltered ATAD supernatant was kept at 4 °C during the longfilteringprocess. Filtering ATAD supernatant through Whatman 934AH filters (approximately 1 micron) did not noticeably remove sample turbidity. Difficulty infilteringATAD sludge was also experienced by Trim and McGlashan (1984). Examination of digested sludge at room temperature under the microscope revealed to these researchers two solid phases. The larger solids were generally inert material from the feed sludge while the small solids were mostly dispersed bacteria. They observed no flocculation of biomass.  69  4.4.2.2 Sample Preservation During the OE1 experiment, supernatant was preserved after filtering by freezing at -10 °C, as recommended by Standard Methods (APHA 1989). This method produced some precipitate in the bottom of the test tubes containing ATAD 1 and ATAD 2 supernatant. Also, samples had up to 7 hours to degrade under anaerobic conditions before being preserved, and it was felt that the delay may have compromised the representative nature of the sample. Sometimes samples were thawed for analysis, then had to be stored overnight at -4 °C due to the daily capacity of the automatic analysis rmchine. Alternate methods of preservation were tested that did not require freezing and would not allow samples to change during handling. Before the OD experiment, a test was done to compare preservation methods. The same supernatant samples were (hvided into portions, one of which was analyzed immediately, and the others were preserved in various ways and analyzed a week later. Samples intended for phosphate and nitrate+nitrite analysis were frozen or preserved by addition of a solution of phenyl mercuric acetate (PMA), made up of 0.1 g phenyl mercurate, 20 mL acetone, made upto100 mL with distilled water. Samples intended for ammonia analysis were frozen, preserved with PMA, or preserved by acidification to below pH 2 with sulfuric acid. Preservation with PMA worked better than freezing for phosphate detenninations, but even with the PMA preservation method there was a -10 percent change between the initial phosphate determination and the final phosphate detennination, although no growth was observed in the sample tubes. The only other simple alternative was acidification. This method was not preferred because it tends to oxidize up to 85 percent of organic phosphorus to phosphate (Couillard et al., 1989), and it was hoped that a distinction could be made between those two forms of phosphorus in the results. Therefore, PMA was adopted as the preservation method for phosphate/NOx samples. Acidification worked best for the ammonia samples. During the OD experiment, supernatants were divided into two portions after centrifuging and one portion was preserved with PMA while the other was acidified. Unfortunately, during the OD experiment, bacterial growth was observed in some of the P0/NOx tubes, and subsequent PMA doses had to be 4  increased to try to prevent sample degradation. Tests done with pour plates never did discover 70  the correct dosage, since all plates showed growth. After the OD experiment the PMA preservation method was abandoned, it was felt that doses required to ensure sterilization were possibly so high that treated samples would pose a hazard to the analysis machine. During the OS and OE2 experiments, the PO4/NOX samples were acidified directly after centrjj^ging. A distinct colour change was noted after acidification. The estimated error resulting from this preservation method is discussed in Section 4.5.2.2. 4.4.3 Discharge Gas Samples Discharge gas samples were collected through an opening in the vent pipe. If foam cutters were running, they were turned off one hour before gas sampling to allow at least three air changes in the head space above the sludge in the digester. A piece of inflexible tubing was inserted into the opening, which was then sealed with a rubber bung. Various apparatus were connected to the inflexible tubing to do sampling for nitrogen/oxygen/carbon dioxide/methane composition, and for ammonia gas. 4.4.3.1 Nitrogen/Oxygen/Carbon Dioxide/Methane To obtain gas samples, flexible tubing was attached to the inflexible tubing installed in the digester. The flexible tubing was connected to a glass gas sampling vial, which was connected with more flexible tubing to a hand pump. The vial was first evacuated with the hand pump, then the inlet valve opened to flood the vial with digester gas. This procedure was repeated, then digester gas was pumped through the vial with 30 compressions of the hand pump, and the valves on the gas sampling vial were closed. Two samples from each ATAD gas space were collected in this manner each time discharge gas was sampled. 4.4.3.2 Arjamonia To obtain gas samples for ammonia measurements, flexible tubing with a 3 way valve was attached to the rigid tubing entering the digester. On one outlet of the valve were two 60 mL syringes in parallel. These syringes were used to flush the tubing with 360 mL of digester gas, 71  before tubing on the other outlet of the valve was connected to the inlet of a glass rmcro-impinger containing 20 mL of 1 molar sulfuric acid. One liter of discharge gas was bubbled through the suMiric acid. The sample was then stored in glass COD tubes at 4 °C until analysis within 7 days of sarnpling. This sampling method was based upon Arnmonia in Air Method # 0050 (Worker's Compensation Board, 1989). 4.5 Laboratory Analysis and Discussion of Method Error  4.5.1 Solids 4.5.1.2 Analysis Method Total solids and total volatile solids were measured, rather than the more usual suspended solids fractions because of the difficulty in filtering the ATAD samples. One experiment (discussed in detail in Section 4.5.2.2) was done using digested primary sludge Only, fottowing the completion of the OE1, OD, OS, and OE1 experiments (to obtain an approximate figure for suspended solids retraining in the supernatant). Total solids and volatile solids analysis was done daily and in triplicate for each of the Primary, Secondary, ATAD 1 and ATAD 2 sludge samples collected. Each sample was blended until it appeared to be relatively homogenous, then separated into three fractions. Using a graduated cylinder, 25 mL of each fraction was measured into a ceramic dish which had been previously fired, cooled in a dessiccator and weighed. The contents of the dishes were dried overnight at 104 °C for at least 12 hours before being cooled in a dessiccator for a further 5 hours. The cooled dishes were then weighed, and fired at 550 °C for at least 20 minutes, before being cooled for at least 1 hour in a dessiccator and weighed again. 4.5.1.2 Method Error To determine method error, the coefficient of variation (precision) was calculated for the three solids measurements taken per sample. Next, the average precision for solids content measurements for each type of sludge was calculated and plotted in Figure 22.  72  Primary Sludge Solids Coefficient of Variation  Secondary Sludge Solids Coefficient of Variation  TS  • TS  VS • NVS  NVS  ATAD 2 Solids Coefficient of Variation  ATAD 1 Solids Coefficient of Variation  • TS M  • TS  m vs  vs  • NVS  I 8  8  111 II  0 0  O  • NVS  8  F I G U R E 22 - Average Precision for Solids Measurements  Because o f its non-homogenous texture even after blending, primary sludge showed the highest variation between measurements. The homogenous nature o f the other solids detenninations is demonstrated by their lower variations. The non volatile solids ( N V S ) measurements used for mass balance calculations had an average precision o f less than 2 percent. Volatile solids measurement precision was mostly less than 2 percent for Secondary, A T A D 1 and 73  ATAD 2 solids measurements, with the exception of a shghtly higher variation of 2.1 percent for Secondary sludge in the OD experiment. Primary sludge volatile solids measurement precision was usually less than 3 percent, with the exception of a 3.2 percent precision for the OE1 experiment. 4.5.2. Total Phosphorus and Total Kjeldahl Nitrogen 4.5.2.1 Analysis Method Total phosphorus (TP) and total Kjeldahl nitrogen (TKN) were measured daily and in triplicate for each of the Primary, Secondary, ATAD 1 and ATAD 2 sludge samples collected. Total dissolved phosphorus (TDP) and total dissolved Kjeldahl nitrogen (TDKN) were also measured daily for the same samples. TKN and TP samples were diluted and stored at -10 °C as described in Section 4.4.1.2. TDKN and TDP samples were stored at -10 °C after filtration during the OE1 experiment, and were acidified to pH 1 to 2 and stored at -10 °C during the other experiments. Before digestion, samples were allowed to thaw slowly at room temperature so as to avoid volatilization of ammonia which might result from thawing the samples in a microwave. An aliquotfromeach sample bottle was withdrawn while agitating the bottle and placed in a 75 mL micro-Kjeldahl flask. Boiling chips and 10 mL of digestion solution (200 mL concentrated H S0 + 134 g K 2 S O 4 made up to 1 liter with distilled water) were also placed in the micro2  4  Kjeldahlflask.The sample was digested for 7 hours, 3.5 hours at 140 °C and 3.5 hours at 360  0  C. Sample digestion took place vrithin 4 days of sample collection. The digestion method was takenfromthe Technicon Block Digester Model BD-40 manual, and is standard procedure in the UBC Environmental Engmeering Lab. The digested samples were made up to 75 mL with distilled water and well mixed. After settling, 10 mL was withdrawn and analyzed on the Lachat Quikchem AE Automated Analyzer using Quikchem Method No. 10-107-06-2-D for TKN and Method No. 10-115-01-1-1 for TP. The normal range for these tests is 0.5 to 20 mg/L N for TKN and 0.2 to 20 mg/L P for TP, but since the Lachat is equipped with optical dilution, the limits were able to be lowered to 0.05 mg/L for both TKN and TP. 74  4.5.2.2 Method Error Dissolved TP samples were preserved by freezing during the OE1 experiment and acidified before filtering and frozen during the OD, OS and OE2 experiments. Couillard et al. (1989) stated that 50 to 80 percent of polyphosphates are hydrolyzed when samples are acidified for preservation. Therefore, a small amount of error might have been introduced into the results i f the suspended solids remaining in the sample after centrifuging and before filtration contained polyphosphates. Another source of error mvolving acid preservation before filtering might be the effect of acid conditions upon Bio-P bacteria which release stored phosphorus when cultured at pH 5.5 (Levin and Shapiro, 1965). However, samples were preserved to between pH 1 to 2 during this experiment, and it was hoped that if any mermophilic Bio-P organisms were present, they would be inactivated before they were able to release phosphate into solution. Of course, the cells may also have lysed under those conditions, releasing polyphosphate which would be partially hydrolyzed by the acid. To estimate the error resulting from hydrolyzation of particulate polyphosphate in centrifuged sample supernatant, a sample of primary sludge digested for 6 days at a low air flow in the same apparatus used in this experiment was analyzed for solids. Total and volatile solids of the "error check" sample were determined in triplicate, (shown in Table 9) and were found to be comparable to the average total solids in A T A D 2 during the experiments. The error check sample was then centrifuged for 20 minutes at 3620 r/min, which was approximately one-third the speed at which sludge samples were centrifuged during the experiments. Since the apparent turbidity of the error check sample supernatant was higher than turbidity observed in centrifuged samples during the experiments, it was felt that the suspended solids in the error check sample are likely representative of the worst case during the actual experiments, and any other solids differences due to the lack of secondary sludge in the error check sample are likely negligible for the purposes of the error check. Total and volatile solids were determined for the supernatant in triplicate. A portion of the supernatant was then filtered through 0.45 micron filters as was done during the experiments, and total and volatile solids were determined for the filtrate. The results are shown in Table 9.  75  TABLE 9 Solids Type  Supernatant Solids Check Supernatant Solids Sludge Solids Total Solids  Total (TS) Volatile (VS) Non Volatile VS/TS  (mg/L) 18656 16686 1967 0.89  Suspended Solids (mg/L) 17644 16033 1611 0.91  Total Solids Dissolved Solids (mg/L) (mg/L) 2410 1012 1921 656 488 356 0.65 0.80  Suspended Solids (mg/L) 1398 1265 132 0.91  Appendix 5 details the calculation of maximum error resulting from phosphorus release from supernatant suspended solids during sample acidification in the OD, OS and OE2 experiments. These expected errors as a percentage difference from measured values are surnmarized below in Table 10.  TABLE 10 Maximum Expected Errors in Dissolved P from Sample Acidification ATAD 2 ATAD 1 Experiment (%) (%) OD -3.3 -1.9 -8.6 -7.7 OS -6.4 -7.2 OE2  Figure 23 illustrates the average precision calculated for TKN, TDKN, TP and TDP for each type of sludge during each experiment. For the TKN results, the basis of the nitrogen balances, Primary sludge precision was better than 5 percent, Secondary sludge precision usually better than 6 percent except for OE1, and the precision for both ATAD sludges was better than 4 percent. For the TP results, the basis of the phosphorus balances, primary sludge measurement precision was usually better than 6 percent except for OE1, secondary sludge measurement precision was better than 5 percent, and ATAD 1 and ATAD 2 sludge measurement precision was better than 5  76  percent. For TDP, the precision was generally better than the expected error from hydrolyzation of suspended solids rermming in the supernatant, as listed in Table 10.  Primary Sludge Nutrients Coefficient of Variation  Secondary Sludge Nutrients Coefficient of Variation  10  • TKN  • TKN  •  •  TDKN  TDKN  • TP  • TP  • TDP  • TDP ITI  ATAD 1 Sludge Nutrients Coefficient of Variation  y  iss  ATAD 2 Sludge Nutrients Coefficient of Variation  10  10  8  m TKN  8  • TKN  •  6  •  4  • TP  2  Hi TDP  TDKN  • TP • TDP  m  H  o  0  m  8  p o  TDKN  CN  O  8  FIGURE 23: Average Precision for Nutrient Measurements  Supernatant samples from A T A D 1 and A T A D 2 were highly coloured, but measurement variations due to colour interference were always less than 0.2 mg/L, which is negligible compared to the measured TDP concentrations. 77  Standards were analyzed in conjunction with samples and samples were spiked with standards to determine method recovery. The range of measured recoveries are listed in Table 11. TABLE 11  Supernatant Type  Standard Recovery TDKN TP  TKN Avg.  Std. Dev.  Avg.  Std. Dev.  Avg.  Std. Dev.  TDP Avg.  Std. Dev.  98.7 4.7 101.1 4.8 Standards 4.9(a) 0.4 100.7 2.4 95.3 97.7 2.2 98.3 Primary 9.4(a) 100.4 10.4(a) 98.8 94.6 Secondary N/A(b) 103.7 N/A(°) 5.4(a) 5.6(a) 97.8 100.6 3.1 101.9 101.6 2.5 ATAD 1 6.6(a) 16.7(a) 6.1(a) 98.1 100.7 100.8 101.4 ATAD 2 6.l( ) (a) Outside the range of corresponding measurement precision discussed earlier. (b) Onfy one measurement made, therefore standard deviation cannot be computed. a  Standard recovery was generally within 95 percent, and average spiked sample recoveries were mostly within a few percentage points of 100 percent recovery. However, the range of spiked sample recoveries generally exceeded the error expected eitherfrommeasurement accuracy orfromacidification. Since the gross errors were both positive and negative, they may have been partially due to additional titration steps, which would have added some measurement error. Another source of inaccuracy would be the effect of a small number of determinations; each range in Table 11 represents only 4 or 5 measurements, with the exeption of DP which represents only 2 measurements. Also, each spiking was done only once, while the unspiked samples were determined in triplicate; therefore, the effect of variable solids in the TKN and TP samples was likely magnified in the spiked samples. The conclusion here is that more spiked sample detenninations would have reduced the possible error in the spiked sample measurements. However, the average results indicate that there were no major interferences in the determination methods.  78  4.5.3 Phosphate 4.5.3.1 Analysis Method A s explained in Section 4.4.2, a simple method of properly preserving phosphate without oxidizing organic phosphorus was not developed during these experiments. After filtration, samples were diluted with distilled water to within the range o f analysis standards. Dilution was performed twice so as to assess error introduced by dilution technique, and so as to provide duplicate samples for analysis. "Preserved" samples were frozen during the O E 1 experiment. During the other experiments preservative was added to the samples, then they were stored at 4 °C for no more than 7 days before analysis. Supernatant samples were analyzed for phosphate during all four runs, using Quickchem Method N o . 10-115-01-1-Z, which has a range o f 0.05 to 50 mg/L P.  4.5.3.2 Method Error Because o f the preservation problems, none o f the phosphate numbers can be regarded as accurate, but they are good indicators of the accuracy of the total dissolved phosphorous test during the O S and O E 2 experiments. Figure 24 illustrates the precision in the phosphate analysis technique for each experiment.  Phosphate Coefficient of Variation 12 10  P = Primary Sludge  8  S = Secondary Sludge  6 4  A l = A T A D 1 Effluent Sludge  2  A 2 = A T A D 2 Effluent Sludge  0  F I G U R E 24 - Average Precision for Phosphate Measurements 79  The 0E1 results clearly show thatfreezingwas the least effective method of preservation used during these experiments. It is interesting, though, that Standard Methods for the Examination of Water and Wastewater (APHA, 1989) recommendsfreezingas a preservation technique for phosphate. During the OS experiment, the automatic pipette used for dilutions rmlfunctioned, resulting in worse precision than that for the OD and OE2 experiments. Otherwise acid preservation produced as good a precision as the PMA preservation technique. 4.5.4 Nitrate + Nitrite 4.5.4.1 Analysis Method Nitrate + Nitrite (NOx) was deteirnined in conjunction with phosphate using the same samples and the Quikchem Method No. 10-107-04-1-Z on the Lachat. Additional undiluted NOx samples were also provided for analysis to allow for low levels in the diluted samples. The range of this test was 0.05 to 25.0 mg/L as N. 4.5.4.2 Method Error As discussed in Section 4.4.2, neitherfreezingnor PMA were good methods of preserving NOx samples. Therefore the NOx concentrations measured for the OE1 and the OD experiments after sample preservation and storage are probably lower than the amounts in the original samples. Figure 25 illustrates the precision of the NOx measurements made during the experiments. Freezing was used during the OE1 experiment and it has by far the worst precision. The precision for ATAD 1 and ATAD 2 is better for the ATAD measurements during OE2 than for the others because: 1. NOx measurements were significantly above the lower hmit of the analysis method 2. Values recorded during the OD and OS experiments were very close to the lower limit, making small differences look larger.  80  NOx Coefficient of Variation 12 i  P = Primary Sludge S = Secondary Sludge A l = A T A D 1 Effluent Sludge A 2 = A T A D 2 Effluent Sludge  OEl  OD  OS  OE2  F I G U R E 25 - Average Precision for N O x Measurements  4.5.5 Ammonia 4.5.5.1 Analysis Method Ammonia samples were frozen during the O E l experiment,  rawing the  other experiments,  preservative was added to the samples before storage at 4 °C for no more than 7 days before analysis. Ammonia samples were usually diluted 1/25 before storage. Before analysis on the Lachat, using Quikchem Method N o . 10-107-06- 1-Z, sample p H was adjusted to between 3 and 5 by addition o f sodium hydroxide. The detection limit for this test is 0.05 to 25.0 mg/L N .  4.5.5.2 Method Error Samples were not p H adjusted before analysis during the O E l experiment, which accounts for the poor measurement precision for that experiments shown in Figure 26.  Precision during the  OS experiment was worse than the O D and O E l experiments because o f the problems with the automatic pipette used for diluting, as mentioned earlier.  81  Ammonia Coefficient of Variation 14 12  •  i  10  S = Secondary Sludge  8 6  A l = A T A D 1 Effluent Sludge  4 • A2  2 0  P = Primary Sludge  8  in  O  A2 = A T A D 2 Effluent Sludge  8  F I G U R E 26 - Average Precision for Ammonia Measurements  4.5.6 Chemical Oxygen Demand 4.5.6.1 Analysis Method During the O E l experiment, chemical oxygen demand ( C O D ) samples were frozen, then analyzed after the experiment was complete. Only total C O D samples were analyzed, using frozen 1/25 dilutions. During the O D experiment, total C O D samples were analyzed on the same day as the sample was taken, and soluble C O D samples were frozen and analyzed after the experiment was complete. During the O S and O E 2 experiments, total and soluble C O D samples were analyzed on the same day as samples were collected. C O D analysis was done using Standard Methods 5220D, based upon 16 m m diameter bylOO mm long tubes, but using only 2.0 m L o f sample and scaling the reactants accordingly. Standards were 250 mg/L, 500 mg/L, 800 mg/L and 1000 mg/L. A l l C O D samples were analyzed in duplicate.  4.5.6.2 Method Error Some o f the samples regularly fell below the lowest standard at 250 mg/L, notably the primary and secondary supernatant samples. Since good straight line calibration curves were always 82  obtained, (r =0.999 and an average standard error on the COD determination of 10 mg/L) 2  quoting the COD results as calculated rather than as "less than 250 mg/L" was felt to be valid. However, it should be noted all reported values which are less than 250 mg/L COD are probably not as accurate as those samples which fell within the standards range. 4.5.7 Volatile Fatty Acids. 4.5.7.1 Analysis Method Volatile fatty acid (VFA) samples were takenfromthe supernatant after centrifuging, before preservatives were added for nutrient testing. Aliquot volumes of 2 mL were pipetted into glass vials, to which 1 drop of 10 percent phosphoric acid was added as a preservative. The vials were capped, stored at 4 °C for no more than 7 days, then analyzed using a Hewlett Packard 5880A Series gas chromatograph with 5880A Series GC terminal. 4.5.7.2 Method Error Based upon technician experience with the Hewlett Packard gas chromatograph, the test is accurate to within 5 percent in a range of 1 to 1000 ppm. 4.5.8 Discharge Gas Ammonia Content 4.5.8.1 Analysis Method Samples were pH adjusted with sodium hydroxide to within pH 3 to 5, and analyzed on the Lachat using Quikchem Method No. 10-107-06- 1-Z within 7 days of sanmling. Samples were analyzed in duplicate. 4.5.8.2 Method Error Some loss of ammonia may have resulted when pH was inadvertently raised to over 6 on some samples while attempting to adjust pH as required for the analysis method, but this loss was probably only minor.  83  Figure 27 illustrates the precision between measurements during the OS and OE2 experiments. Precision was not very good for the ATAD 1 measurements during the OS experiment, but were generally below 10 percent for the other measurements.  Al = ATAD 1 Effluent Sludge A2 = ATAD 2 Effluent Sludge  FIGURE 27 - Average Precision for Ammonia in Discharge Gas Measurements  4.5.9 pH 4.5.9.1 Analysis Method pH was measured daily for both ATAD 1 and ATAD 2 sludge using glass pH probes. Readings were taken in the transfer tank at digester temperature as effluent sludge was withdrawn from each digester. The meter, a Cole-Parmer Series 5986 Chemcadet pH/mV meter (accuracy from manufacturer of ± 0.01 pH) , was calibrated daily at 20 °C using the built-in automatic cahbration. A Fisher 13-620-289 probe was used during the OE1 and OD experiments and a Fisher 13-620-287 probe was used during the OS and OE1 experiments. These probes are able to function within a range of-5 to 110 °C. The temperature reading on the meter was adjusted to the digester temperature before pH was measured and recorded. pH for primary and secondary sludge was recorded during ajjkaiMty tests, on samples that had been diluted 1/25 with distilled water. 84  4.5.9.2 Method Error pH probes were checked twice against pH probes and meters in the laboratory, and the probe was changed after the OD experiment, when discrepancies were noticed between pH readings in the laboratory on diluted ATAD samples and pH values measured during sampling. pH values obtained in the laboratory were often higher even though dilution water pH was not high. The difference may have been due to carbon dioxide dissolved in the ATAD sludge when first sampled; this C0 may have escaped to atmosphere during subsequent mixing and contact with 2  air containing low levels of C0 . 2  4.5.10 Oxygen Uptake Rate 4.5.10.1 Analysis Method Oxygen Uptake Rate (OUR) was measured in situ in ATAD 1 during the OEl experiment, and in ATAD 1 and ATAD 2 after the OE2 experiment. Mixing was turned down to the 30 percent value on the controller, the air feed to the aerator was shut off, and valuesfromthe oxygen meters were recorded either on the data logger or on a continuous strip chart recorder. Oxygen uptake rates were not measured during the OD and OS experiments. It was concluded from preliminary aeration testing that aerationfrommixing at 30 percent was negligible compared to the measured oxygen uptake rate. 4.5.10.2 Method Error Slow probe response time would be the major source of error in this experiment, since the expected oxygen uptake rates are high. Probe response time, as reported by the manufacturer, is 10 seconds for 90 percent of a 100 percent step change; however, the manufacturer's specification may not apply since probe electrolytes were varied. Actual response time was not measured. OUR measured during the OEl experiment was based upon only 2 or 3 curve points. These OUR detenninations and are therefore rough indicators only.  85  4.5.11 Ajjkalinity 4.5.11.1 Analysis Method Alkalinity was measured according to Standard Methods 2320B with the exception that the sample was diluted 1/25 with distilled water before the titration was done, and the final result multiplied by 25 to get the reported alkahmty. Dilution was necessary because of almost mimediate clogging of the pH meter during trials with full strength sludge. Titrant normahty was 0.02 N. An endpoint of pH 4.5 was chosen which corresponds to a complex system. 4.5.11.2 Method Error The distilled water used has a low buffering capacity, and it was felt that aUcahnity would not have been altered substantially at the measured levels by dilution. Any effect would have been to shghtly lower measured ajjkahnity from actual ah\alMty and the effect would have been greater on the primary and secondary sludge samples. 4.5.12 Discharge Gas Oxygen, Carbon Dioxide and Nitrogen Content 4.5.12.1 Analysis Method Witlun 8 hours of sarnpling, a 1 mL sample of discharge gas was withdrawn from each sample vial through a rubber stopper and injected into a Fisher Hamilton Gas Model 29 gas partitioner with a Spectra Physics SP4290 integrator. Injections were done at least in duplicate. An injection of laboratory air was also analyzed for comparison purposes. 4.5.12.2 Method Error Figure 28 illustrates the average precision obtained for discharge gas constituent determinations. In general, precision was better for the gases which were a higher fraction of the total discharge gas volume. The precision of most measurements was 4 percent or better, with the exception of the OD oxygen determination, which had a poor precision of 13.1 percent.  86  A T A D 2 Discharge Gas Measurement Precision  A T A D 1 Discharge Gas Measurement Precision 14  14  12  12  10 8 6 4  •  C02  •  02  •  N2  10 8 6 4  2  2  0  0 OD  OS  OE2  OD  F I G U R E 28 - Average Precision for CO2, N and 0 2  87  2  OS  E  •  C02  •  02  111 N2  OE2  Discharge Gas Measurements  5.0 RESULTS AND DISCUSSION The results of these experiments are discussed in four sections. Section 5.1 reviews the experiment operating conditions of temperature, SRT, solids loading and solids destruction. The findings are compared with full scale ATAD operating conditions which were described in Section 3.2. Section 5.2 describes the three different aeration states studied and their effects upon the state variables of DO, ORP, pH and alkalinity. Section 5.3 discusses ATAD supernatant quality in terms of nitrogen, phosphorus and dissolved organic matter, and compares these results to previous research and to mesophilic aerobic and anaerobic digester supernatant quality. Finally, Section 5.4 discusses the results in terms of implications for full scale operation of ATADs, and the potential effect of ATAD supernatant recycle upon Bio-P wastewater treatment plant operation. 5.1 Operating Conditions 5.1.1 Temperature The target temperatures for these experiments were the EPA guidelines of 35 to 50 °C in ATAD 1 and 50 to 65 °C in ATAD 2. Table 12 shows the average, maximum and minimum temperatures achieved during the four experiments. Target temperatures were attained in ATAD 2, which rangedfrom54.0 to 64.2 °C over all four experiments, well within the 50 to 65 °C target range hoped for. In ATAD 1, temperatures for the OS and OE2 experiments were all above the minimum expected value of 35 °C, and only slightly below that value at 34.6 °C and 34.8 °C for the OEl and OD experiment. The maximum temperatures in ATAD 1 all exceeded the expected maximum value of 50 °C. The temperature ranges for all four experiments were quite similar, as shown by the average and standard deviations listed at the bottom of Table 12. Therefore, it is reasonable to state that temperature was relatively consistent between the four experiments, and closely corresponds to that found in full scale installations.  88  TABLE 12  Pilot Scale ATAD Temperatures ATAD 2 Temperature (°C) ATAD 1 Temperature (°C) Minimum Average Maximum Minimum Average Maximum 34.6 47.0 55.1 54.0 57.3 63.2 0E1 OD 34.8 46.2 53.4 56.4 59.6 62.1 OS 35.9 46.3 55.4 54.8 59.7 62.8 OE2 36.7 48.5 55.9 55.4 60.7 64.2 35.5 47.0 55.0 55.2 59.3 63.1 Mean SDO*) 0.98 1.06 1.08 1.01 1.44 0.88 ()Standard Deviation Experiment  a  5.1.2 Heat Sources and Sinks Four parameters had the most effect on tank temperature: influent sludge, mechanical mixing energy, biochemical energy and aeration air. The effects of these will be discussed quahtatively. 5.1.2.1 Jjifluent Sludge The addition of influent sludge resulted in a temperature drop after feeding. Figure 29 depicts the temperature patterns achieved during all four experiments. Temperature patterns were generally the same from day to day, except for a few anomalies which are noted. The anomalies generally corresponded to power outages and equipment problems. In ATAD 2, the temperature drop after feeding was 3 to 4 °C, only shghtly lower than the 4 to 6 °C predicted by Deeny et al. (1991). The temperature drop in ATAD 1 after feeding was between about 14 and 18 °C.  The magnitude of temperature drop and subsequent recovery in  ATAD 1 is greater than the 5 to 10 °C reported by Deeny et al. (1991) but the recovery rate of about 1 °C/h is approximately the same. The curve slopes are roughly similar to those measured in Gemmingen, (Figure 7), but are steeper than those recorded at Ellwangen (Figure 8). The higher temperature curve slopes during these experiments may be due to the difference between the mechanical energy input for this pilot system and full scale systems.  89  Foam cutter turned  1/11/93 0:00  OEl Temperature Profile  1/13/93 0:00  1/17/93 0:00  1/15/93 0:00  1/21/93 0:00  1/19/93 0:00  1/25/93 0:00  1/23/93 0:00  Date (mon/d/y) Time (h) OD  Fouled probe  Temperature Profile  2/23/93 0:00  2/25/93 0:00  2/27/93 0:00  3/1/93 0:00  Power off, aerator stopped z l  3/5/93 0:00  3/3/93 0:00  3/7/93 0:00  3/9/93 0:00  Date (mon/d/y) Time (h) Data not recorded due to power failure  OS Temperature Profile  I" a a H  4/5/93 0:00  4/7/93 0:00  4/11/93 0:00  4/9/93 0:00  4/15/93 0:00  4/13/93 0:00  4/17/93 0:00  Date (mon/d/y) Time (h)  Data not recorded due to power failure 70  a a  •  <  a  OE2  Temperature Profile •  o  50 30 5/3/93 0:00  Lower r/min, same airflow  <  1  !~  V\ V\V\  5/5/93 0:00  5/7/93 0:00  i  c^*H  1  H v\  5/9/93 0:00  - ^ 1 v  1  *  \  5/11/93 0:00  v  \  1 v  \  S< v  5/13/93 0:00  1  1  \  y  •  \  5/15/93 0:00  5/17/93 0:00  Date (mon/d/y) Time (h) ATAD 1  O  ATAD 1 Spot checks  ATAD 2  Figure 29 - Pilot Scale Temperature Trace Patterns 90  •  ATAD 2 Spot checks  5.1.2.2 Mechanical Energy Power was measured at the motor controller. Several measurements were taken and the , average calculated for the OS and OE2 experiments. Power density in ATAD 1 was about 3540 W/m for the OS experiment and 3830 W/m for the OE2 experiment. Power density in ATAD 2 3  3  was about 5080 W/m for the OS experiment and 4660 W/m for the OE2 experiment. 3  3  Therefore, the measured power draw in the installed units was about 15 times the highest recommended value of250 W/m (Kelly, 1990) in ATAD 1 and about 20 times that value in 3  ATAD 2. Power densities during the OE1 and OD experiments were similar in magnitude. Low power motors were initially installed in the pilot scale digesters, but they rapidly overheated and had to be replaced with higher power motors. Size scale-down proved to be a definite problem in terms of power density and is the one major difference between the pilot plant operation and a full scale operation. The shear gradients in the pilot scale ATAD reactors were about 1900/s in ATAD 1 and 2200/s in ATAD 2. Norris and Ribbons, (1971) state that a shear gradient on the order of 10,000 to 100,000/s is required to break DNA, and that similar rmgnitudes of shear gradient are needed to cause polymer degradation and cell rupture. Therefore, the shear gradient during these experiments was probably not high enough to impair the biological functions of the thennophihc bacteria. This conclusion is supported by the oxygen uptake rate, VSS destruction and COD reduction results which are discussed in following sections. To determine the effect of the high mixing energies upon reactor heating rates, experiments were performed to determine temperaturerisefrom mechanical energy input. The pilot scale ATADs were filled with water, the aerators were started, and the water temperature and input air temperature were continuously recorded until the water temperature stabilized. At that point, the heat inputs (mechanical heating energy and input air stream) balanced the heat outputs (heat radiation and output saturated air stream). Detailed results of the experiments are in Appendix 3 and are summarized in Figure 30. Temperature rise from mechanical energy input alone was significant.  91  6001  oc  Airflow vs. Power Demand and the Difference Between Water and Ambient Temperature  o  500  --  o  •  400  I ° 300 §I 1  I  50 45 40 35 & 60  25 H 20 LA 15 10 -5 0 25000  o  y  200  A  100 0 5000  10000  15000  20000  a  Airflow (mLVmin) O 1190 r/min Watts  O 920 r/min Watts  • 1190 r/min Delta T  A. 920r/min Delta T  FIGURE 30 - Mechanical Heating Test Results 5.1.2.3 Airflow Figure 30 shows that airflow rate significantly affected the observed increase in water temperature during the mechanical heating experiments. Inlet air was heated and saturated during passage through the hot water in the tank, and heat removal with saturated discharge gas resulted in lower system equilibrium temperatures at higher airflow. Ambient air temperature had only a slight effect (0.5 C variation in equuibrium temperature) on the results of the mechanical heating experiment. However, during the sludge experiments, ambient air temperature correlated positively with maximum daily temperature for those experiments with high airflow. For the OE2 experiment, with the highest airflow rate, the correlation was greater than 0.9 for ATAD 1 and greater than 0.8 for ATAD 2. For the OE2 experiment, with a lower airflow rate, the correlation was lower at 0.55 for ATAD 1 and 0.5 for 92  ATAD 2. The correlation between ambient temperature and maxmium temperature reached was less than 0.5 for the OS and OD experiments, which had low airflow. This result is not surprising; ambient air temperature is expected to have a greater effect on ATAD temperature when applying higher air flow rates to the hquid mass. 5.1.2.4 Biochemical Energy Table 13 compares the average daily maximum temperature achieved in the pilot scale ATAD reactors with a predicted value based upon the results of the mechanical mixing experiments. Appendix 3 details how the maximum theoretical temperaturerisewas calculated, using input power and airflow as variables. An interpolation based on equilibrium temperaturerisesshown in Figure 13 was used since not enough mformation was available to calculate a heat balance. The calculation was done for the OS and OE2 experiments, during which power input was measured. TABLE 13  Actual Average Daily Maxmium Temperature Compared to Predicted Maxmium Temperature ATAD 2 Temperatures ATAD 1 Temperatures Experiment 95 % 95 % Average confidence Average confidence Daily Predicted range for Daily Predicted range for Maximum Maximum prediction Maxmium Maximum prediction (C) (C) (C) (C) (C) (C) OS OE2  51.0 53.4  41 44  34-49 34-53  60.3 61.1  50 50  44-56 44-57  The average daily maximum temperature was significantly higher than the predicted maximum temperature possible with mechanical heating alone. To evaluate this result, the differences between the water experiments and sludge experiments should be examined. First, the water experiments were batch experiments, and the sludge experiments operated under semi-continuous feed (once every 24 hours). Therefore, during the sludge experiments there was a daily net heat loss due to output of hot sludge and input of cold sludge. All other heat outputs and inputs being 93  equal, the extra net heat loss during the sludge experiments should have resulted in actual maximum temperatures lower than those predicted by the water experiments. Instead, actual maximum temperatures were higher than predicted. Second, liquid volume during the sludge experiments was approximately 25 percent less than during the water experiments. All other heat inputs and outputs being equal, this should have resulted in a corresponding 33 percent increase in maximum fluid temperature. However, heat outputs were not equal. During the sludge experiments, heat was lost with sludge as described above, and more heat was lost with the discharge gas due to hotter output gas containing more water vapour. Therefore, the smaller Uquid volume in the tanks should have resulted in actual maximum temperatures somewhat higher than those predicted by the water experiments, but no more than 33 percent higher. AH of the above actual average rmximum temperatures are within 33 percent of the predicted average daily maximum temperatures. Third, in the sludge experiments, maximum temperatures increased sUghtly during the sludge experiment with higher airflow, which is opposite to the trend exhibited by the water only experiments. Due to the above differences, no conclusion can be drawn as to whether or not a significant amount of biochemical heating (as compared to mechanical heating) was occurring during the sludge experiments. The only definite indication that some biochemical heating did occur is the increase in temperature with higher airflow, which may be due to an increase in aerobic respiration.  5.1.3 HydrauUc Retention Time To calculate the hydrauUc retention time in the ATADs, a volume balance was first required to vaUdate the volume measurements taken during the experiments. This volume balance was also needed for the soUds and nutrient balances, which are discussed in subsequent sections.  94  5.1.3.1 Volume Balance Appendix 2 contains the calculations used for detenrjjxiing volumes for the hquid balances, and for deteimming error in volume measurement. The results indicate that error between system feed sludge volumes and ATAD 1 discharge volumes should be ± 0.7 L, between ATAD 2 feed volumes and ATAD 2 discharge volumes, ± 0.5 L, and between the system feed volumes and ATAD 2 discharge volumes, ± 0.7 L. The results of the volume balances for each run are simimarized in Table 14, which shows that all balances are well within the expected measurement error. Therefore the errors in the volume balance are probably due to measurement error. TABLE 14 Volume Balance Summary Volumes (L) OE1 OD OS Experiment Primary Sludge 16.4 12.0 12.0 Secondary Sludge 8.3 13.0 13.0 System Feed 24.7 25.0 25.0 Sampling and Piping Loss 1.1 1.2 1.1 ATAD 2 Feed 23.6 23.7 24.0 Discharge Gas Vapour 0.5 <0.1 <0.1 Total ATAD 1 Discharge 25.2 24.9 25.2 Volume Balance ATAD 1 +0.5 -0.1 +0.2 23.7 24.0 23.6 ATAD 2 Feed ATAD 2 Discharge 23.4 23.8 24.3 Discharge Gas Vapour 0.2 <0.1 <0.1 Total ATAD 2 Discharge 23.6 23.8 24.3 Volume Balance ATAD 2 0.0 +0.1 +0.3 Volume Balance 0.0 +0.5 +0.4 System  OE2 12.0 13.0 25.0 1.0 23.8 0.4 25.2 +0.2 23.8 23.8 0.2 24.0 +0.2 +0.4  5.1.3.2 Solids Retention Time Solids retention time was calculated for each experiment, based upon the volumes recorded in Table 14. Table 15 shows that the design SRT of 6 days for each experiment was maintained between ± 0.1 d.  TABLE 15 Solids Retention Times Experiment  OEl OD OS OE2  ATAD 1 Operating Influent Volume Volume (L) (L) 73.5 24.7 73.5 25.0 73.0 25.0 74.0 25.0  ATAD 2 Operating Influent SRT Volume Volume (L) (L) (d) 72.5 23.6 3.1 72.5 23.7 3.1 72.0 24.0 3.0 73.0 23.8 3.1  SRT () 3.0 2.9 2.9 3.0 d  System SRT (d) 6.1 6.0 5.9 6.1  5.1.4 Influent Solids Concentration Table 16 lists the influent primary and secondary sludge solids concentrations and volumes, the resultant influent mixed sludge concentrations, and the ratio of primary to secondary sludge by weight. Table 16 shows that the average VS in the influent mixed sludge was 1.7 percent. This number is lower than the 2.5 percent recommended by the EPA ATAD manual. The overall average TS and VS of the influent mixed sludge for each experiment varied within 8 percent and 5 percent of the mean respectively; therefore, the influent mixed sludge VS load was roughly constant between the four experiments. Figure 31 shows that during the OEl, OE2 and OD experiments, there was very little variation in the daily solids concentration of the influent mixed sludge. During the OS experiment, there was a wide variation in the daily solids concentration of the influent mixed sludge, due to a high variation in the solids concentration of the primary sludge. There were two reasons for the variation. Firstly, about 5 days before the OS experiment began, a high concentration of solids, mostly non-volatile, passed through the pilot plant. This may have been because of heavy rain combined with construction work upstream. Secondly, on April 6, the mixer on one of the raw sewage feed tanks was found to have stopped, and may have been stopped for several days. The amount of solids entering the pilot plant consequently declined until the mixer was restarted on April 14; after mixer startup, the amount of solids entering the pilot plant measurably increased, as the solids that had settled to the bottom of the raw sewage feed tank was fed into the system. 96  OE1 Influent Mixed Sludge o a  _  vi op  .3 J  ,  "o  30000 20000 10000  00  1/5/93  1/7/93  1/9/93  1/11/93 1/13/93 1/15/93 1/17/93 1/19/93 1/21/93 1/23/93 Date (mon/d/y)  OD Influent Mixed Sludge 30000 CJ e£ 20000 « op  3 M, 10000 "o oo  0 2/22/93  2/24/93  2/26/93  2/28/93.  3/2/93  3/6/93  3/4/93  Date (mon/d/y)  OS Influent Mixed Sludge  8  o U  o  30000  a  20000  , ^^**-»»^, Xl"^"'"^''"^"'^"' '"' '--^-"-v-"" ""'"' <>  10000 0 3/28/93  4/1/93  4/5/93  <>  j0r  V  4/13/93  4/9/93  4/17/93  Date (mon/d/y)  OE2 Influent Mixed Sludge  30000  .5/3/93  5/5/93  5/7/93  5/9/93  5/11/93  5/13/93  5/15/93  Date (mon/d/y) Total Solids  o V o l a t i l e Solids  — ° — Non-Volatile Solids  Figure 31 - Influent Mixed Sludge Solids Concentrations 97  TABLE 16  Average Influent Mixed Sludge Solids Concentrations Influent Mixed Sludge Secondary Sludge Primary Sludge Exp. Vol. TS VS VS Vol. TS VS VS TS VS VS PS/SS frac- TS(> fracfraction tion tion (L) (%) (%) (%) (L) (%) (%) (%) (%) (%) (%) (g/g) OEl 16.4 1.86 1.67 89.8 8.3 2.29 1.85 80.8 2.01 1.73 86.1 62/38 12.0 2.13 1.89 88.7 13.0 2.29 1.79 78.2 2.21 1.84 83.3 46/54 OD 12.0 1.80 1.35 75.0 13.0 2.97 1.94 65.3 2.41 1.66 68.9 36/64 OS OE2 12.0 1.90 1.61 84.7 13.0 2.59 1.85 71.4 2.26 1.74 77.0 40/60 2.54 1.86 73.9 2.22 1.74 78.8 1.92 1.63 84.6 Mean 0.32 0.06 7.0 0.17 0.07 7.6 0.14 0.22 6.7 SD(> 7.4 4.2 12.6 3.3 7.2 13.5 CVvT) ()Standard Deviation (^Coefficient of Variance ()Ratio of Primary Sludge to Secondary Sludge C  a  a  c  Table 16 also shows a higher variability in total solids for secondary sludge than for primary sludge. This was possibly due to the changing quality of the waste secondary sludge. Pilot plant SRT varied according to operational problems, which changed the settling/dewatering characteristics of the secondary sludge and also the volatilefraction.If the plant was not wasting enough secondary sludge to supply the digesters, a supplementary sludge sourcefromanother pilot plant operating as a Bio-P Trickling Filter Solids Contact (TF/SC) process was used as required. The TF/SC secondary sludge had different settling/dewatering characteristics and a different volatilefractionthan the UCT plant. During the OEl experiment, a problem in the pilot plant reduced the planned amount of secondary sludge feed so that the weight ratio of primary sludge to secondary sludge (PS/SS) was 62/38. The other experiments had PS/SS weight ratios varyingfrom36/64 to 46/54. Mass balances for the Annacis Island plant showed a PS/SS ratio of 49/51 at average annual flows, and similar calculations for the Lulu Island plant showed a 59/41 ratio (ABR Consultants Ltd., 1992) The Banff sewage treatment plant was designed using a 50/50 PS/SS ratio. (Reid Crowther, 1994)  98  5.1.5 Solids Loading Table 17 shows the organic loading for each of the ATAD tanks and for the system. Based upon system loading, these experiments were loaded at about 0.5 to 0.75 of the usual loading rates for Fuchs type systems and even lower fractions for some of the other types of systems, such as Gibsons and Salmon Arm  TABLE 17 Solids Loading ATAD 2 ATAD 1 Experiment (kg VS/m -d) (kg VS/m -d) 4.6 5.8 OE1 OD 6.3 4.9 5.7 4.7 OS OE2 5.9 4.6 4.7 5.9 Mean 0.3 0.1 SD(> 5.1 2.1 CV©, % ©Standard Deviation ©Coefficient of Variance 3  3  a  System (kg VS/m -d) 3.4 3.2 2.9 3.0 3.1 0.2 7.1 3  Although solids loading was not as high as originally planned (due to lower influent mixed sludge solids concentrations), this probably did not affect results as it would have in a full scale plant. In a full scale plant, this low loading would have resulted in lower temperatures in the reactors and lower stabilization rates. In these pilot scale approximations, the solids loading rate did not noticeably affect average reactor temperature because of the large effect that mechanical heating had upon the experimental system 5.1.6  Solids Balance  A solids balance around the system (detailed balance and error estimate calculations in Appendix 2) was completed for each experiment. Results are summarized in Table 18. The expected measurement error calculated from the values discussed in Chapter 4, is shown beside each solids balance.  99  TABLE 18  Non-Volatile Solids Balances OE2 Experiment OS Experiment OD Experiment OEl Experiment Actual Expected Actual Expected Actual Expected Actual Expected Balance Error Error Error Error Error Error Error Error For: (%) (%) (%) (%) (%) (%) (%) (%) ATAD 1 -7.0 -4.9 +17.8 -3.9 ±3.6 ±4.0 ±3.5 ±4.9 ATAD 2 -0.3 ±2.4 +3.0 ±3.6 +21.8 ±3.2 -4.2 ±3.5 System -6.7 ±4.5 -2.2 ±3.8 +42.3 ±5.0 -7.7 ±4.3 Table 18 shows that the solids balance was generally within a few percentage points of the expected measurement error, except for the OS experiment. The OS experiment did not balance because during that experiment, the influent mixed sludge non-volatile solids concentration was not as consistent as it was for the other experiments, which can be seen in Figure 31. The problem was compounded by increased variation in the non-volatile solids measurements for primary sludge (Figure 22) due to thicker sludge which was more difficult to sample accurately. Volatile solids reduction calculations can therefore be determined for the OEl, OE2 and OD experiments but not for me OS experiment. 5.1.7 Volatile Solids Reduction Table 19 summarizes the volatile solids reduction calculated for the OEl, OE2 and OD experiments.  TABLE 19  Percent Volatile Solids Reduction Experiment OEl OD OE2  ATAD 1 ATAD 2 11.2 12.3 11.7  17.8 19.2 20.0  100  Total 27.0 28.9 30.1  The calculation for ATAD 1 and ATAD 2 was based upon grams of total VS oxidized, rather the difference in influent mixed sludge and digested sludge VS concentration. This method avoids errors from evaporation of water and from volatile solids metabolized into soluble forms but not completely oxidized. The calculation for system VS reduction required a comparison between influent mixed sludge and digested sludge VS concentration because of intermediate sampling losses. Therefore, the separate and total reductions do not balance due to the (iifferent calculation methods required. Detailed calculations are provided in Appendix 2. To evaluate these results, the temperature-sludge age products were calculated and compared to the EPA design curve shown in Figure 32 (EPA, 1979). Table 20 lists the temperature-sludge age products.  60  50  h  40  X  •  o  30  A  + •  20  H  10  b  o  •  -  PILOT FULL PILOT FULL PILOT PILOT PILOT FULL  PLANT SCALE SCALE SCALE PLANT PLANT PLANT SCALE  REF REF REF REF REF REF REF REF  (188) (194) (178) (185) (208) (211) (192) (196)  1 0  200  400  600  800  1000  1200  1400  1600  1800  2000  TEMPERATURE °C x SLUDGE AGE, days  FIGURE 32 - Aerobic Digester Percent VS Reduction Design Curve (EPA, 1990)  101  TABLE 20  Temperature-Detention Time Products Experiment ATAD 1 ATAD 1 System (Cdays) (Cdays) ( Cdays) OEl 141 178 319 OD 134 185 319 OE2 146 188 334 For a system time-temperature product of about 320 to 335, the EPA Design Curve predicts about 35 percent VS reduction. The values obtained during this experiment for the total system are somewhat less than that. The same curve predicts about a 20 percent VS reduction for a time-temperature product of about 140 C-d, which matches the results in ATAD 1. VS reduction in ATAD 2, at about 12 percent, was approximately half the 26 percent predicted by the EPA design curve for a time-temperature product of 180 C-d. Therefore, reactions proceeded at about the same rate predicted by the EPA design curve in ATAD 1 but much slower in ATAD 2, resulting in an overall system performance shghtly lower than that predicted by the EPA design curve. The lower VS reduction rates in the second reactor could be due to lower loading rates, as discussed by Jewell and Kabrick (1980) and depicted in Figure 9. Table 20 shows that during this experiment, at least 60 percent of the total VS reduction took place in thefirstreactor, as is predicted by Deeny et al. (1991). An interesting observation is that VS reduction in all three tests was virtually the same, even though the OD experiment was run under oxygen deprived conditions, and the OEl and OE2 experiments were run under oxygen excess conditions at different levels. This result seems to imply that oxygen supply in a mermophilic system is not as important as the tune-temperature product and food supply, for detenmning VS reduction. Wolinski, (1985) as noted in Chapter 3, found that VS reduction increased with increasing air supply. However, it appearsfromthe solids retention times and temperatures quoted in the reference that those results may have comefromexperiments with widely differing timetemperature products. This seems possible because Table 1 in that paperfistsinformation with  102  retention times from 4.0 to 13.3 days, but with final temperatures after 24 hours of digestion with a range of only 55 to 67 C. It should also he noted that in a full scale system, the aeration state would likely affect reactor temperature. A lower air supply rate would tend to strip less heatfromthe reactor, but conversely less biochemical energy would be generated under anaerobic conditions than under aerobic conditions. The net effect in full scale is not known, although Messenger (1991) reported that as long as an ATAD is run under oxygen limited conditions, increasing the oxygen supply increases reactor temperature. As explained earlier, in these pilot scale experiments, temperature under all aeration states was the same due to the predominance of mechanical energy, as opposed to biochemical energy, in the pilot scale system. 5.1.8 ATAD Sludge Solids Concentration Table 21 summarizes the average TS and VS concentrations found in the ATAD reactors during the four experiments. TABLE 21  Average ATAD Sludge Solids Concentrations ATAD 2 ATAD 1 TS VS TS VS Experiment (mg/L) (mg/L) (mg/L) (mg/L) OE1 16800 14200 15400 12800 OD 18500 15000 16700 13100 OS 22800 14000 24100 13500 OE2 19100 14000 17200 12300 19300 14300 18350 12930 Mean SD© 2530 470 3900 510 CV©, (%) 13.1 3.3 21.3 3.9 ©Standard Deviation ©Coefficient of Variation Note that average VS concentrations in the ATADs were fairly consistent, with less than a 4 percent coefficient of variance. VS concentrations in the ATADs during experiments were 103  consistent during the OE1, OD and OE2 experiments but varied during the OS experiment, as shown in Figure 33.  ATAD 1 VS Concentration a  •S !» 1 * § B g ° >  20000 18000 16000 14000. 12000 10000 1  1  5  6  7  8  10  11  12  Experiment Day No.  ATAD 2 VS Concentration a 20000 •3 ^ 18000 £ I £ 16000  ^ § a i4ooo g °  w  12000 10000  4  6  8  10  12  Experiment Day No. -O-  OE1  -A-  OD  OS  OE2  FIGURE 33 - ATAD VS Concentration 5.1.9 Summary of Op erating Conditions The pilot scale system was operating within the temperature range recommended by the EPA ATAD Design Manual (1990) and even a few C higher. A somewhat larger overall temperaturerisewas seen after feeding, probably due to higher mechanical energy input in the 104  pilot scale system than in full scale systems. It is not clear whether biochemical heating was a significant contributor to temperature rise in the pilot scale reactors, but there is some indication ' mat biochemical heating did occur. VS solids concentration in the influent mixed sludge averaged 70 percent of that recommended for full scale systems, and solids loading was 50 to 75 percent that of full scale systems. VS reduction was lower than observed in full scale systems, but this was possibly due to lower solids loading since the rate of reaction is reportedly driven by the food supply. The effect of lower solids loading on the experiment results is thought to be negligible, because of the high mechanical energy inputfromthe aerators. In terms of temperature range and average volatile solids loading, the four experiments were comparable. Steady state was reached for the OEl, OD, and OE2 experiments with regards to solids loading and solids reduction, but was not possible during the OS experiment due to the high variation in the influent mixed sludge loading. The ratio of primary sludge to secondary sludge varied between experiments, but is allowed for in subsequent discussions by comparing differences between influent to effluent parameters rather than directly comparing effluent parameters.  5.1.10 Apphcability of Pilot Scale Results to Full Scale Results The foregoing shows that when applying the following results to full scale, two points should be kept in mind. First, concentrations of all parameters discussed in this work are likely to be lower than those found in most full scale installations due to the lower solids concentrations in the mixed influent sludge for the pilot scale ATADs. Second, rnixing energies were much higher in this pilot scale system than in full scale systems. As previously discussed, the high rnixing energy did not affect the viability of the bacteria in the pilot scale system However, it did result in a very well mixed system, which is not always the case in full scale installations. This difference is common when comparing pilot scale results to full scale, and usually results in tank and equipment sizing somewhat larger (by a safety factor) than is suggested by pilot scale results. Other than the above, the following results should be applicable to full scale installations. 105  5.2 Three Aeration States  5.2.1 Oxygen Requirements Measurements of specific oxygen uptake rate (SOUR) were made over several days during the OE1 experiment and after the OE2 experiment, to determine if the high mbdng rates and resulting shear stresses had affected the viability of the bacteria. All of the experiments took longer than 10 seconds to fall to O mg/L DO; therefore, probe response time was probably not a source of error for the SOUR measurements. A summary is presented in Table 22. TABLE 22  Measured Specific Oxygen Uptake Rate Time after Average SOUR feeding (h) ( O,/gVS-d) ATAD 1 ATAD 2 OE1 OE2 OE2 0.50 40 1.00 144 1.25 169 1.50 142 • 3.00 1494 175 6.00 316 226 22.00 203 165 23.00 93 g  These results support the hypothesis that thermophihc bacteria activity was not impaired by the high mixing energies in the pilot scale ATADs. Further observations must take into consideration that the OE1 and OE2 oxygen uptake rate measurements were done using different electrolytes in the dissolved oxygen probes. Also, the OE1 experiments used a larger recording interval than the OE2 experiments; therefore, the OE1 SOUR values are less accurate than the OE2 SOUR values. As discussed in Chapter 3, reported values of SOUR for ATADs rangefrom100 to 400 g 0 /g VSS-d (EPA, 1990). Most of the results shown in Table 23 fall within this range, except 2  for the 3 hour result for OE2 in ATAD 1. Of course, Table 23 is based upon VS rather than VSS, 106  due to thefflteringdifficulties mentioned earlier. Measured SOUR values based upon VSS concentration would be shghtly higher - about 4 percent higher based upon the experiment described in Section 4. Required oxygen supply can also be calculated on the basis of oxygen required per kilogram of VS oxidized, assuming an oxygen requirement of 1.0 to 3.5 kg 02/kg VS oxidized (as noted in Chapter 3) and the measured values of 0.23 to 0.25 kg VS reduction in ATAD 1 and 0.10 to 0.14 kg VS reduction in ATAD 2. These numbers result in oxygen requirements in ATAD 1 of about 222 to 845 g 0 /kg VS-d, and in ATAD 2 of about 111 to 546 g 0 /kg VS-d. These calculated 2  2  oxygen requirements match the SOUR measured in ATAD 1 after the OE2 experiment and are somewhat higher than those obtained in ATAD 2 for the same experiment. Therefore, it seems possible that the SOUR range defined in the EPA ATAD Design Manual (1990) is too low and that actual SOUR in ATAD reactors can be higher than those reported to date. The OUR values obtained during the OE1 experiment are significantly lower than the value recorded during the OE2 experiment after three hours of feeding. One reason for the lower initial values during the OE1 experiment might be a lag period after feeding, similar to the one noted by Bomio (1989) and shown in Figure 11. The OE2 experiment had a 22 hour OUR value which is over 3 times the 23 hour OUR measured for OE1. This seems to indicate that the experiment with the higher airflow, OE1, was able to better stabilize the sludge than did OE2. 5.2.2 Oxygen Supply The aeration equipment was tested to determine if it could meet the expected oxygen demand, and the detailed results of the aeration tests are contained in Appendix 4. The aerators are capable of transferring enough oxygen to meet the lower measured SOUR values by mixing alone. Efficiency greatly increases as air flow decreases for a given rotational speed, probably due to the smaller air bubble size which results when lower air flows are sheared at the same rate as higher air flows. However, even with the high efficiencies measured at the lower air flows, the aerators should not have been able to satisfy the high demands reported in Section 5.2.1 for the OE2 107  experiment. Results discussed in the following sections indicate that oxygen demand was satisfied during the OE2 experiment; therefore, oxygen transfer efficiency in sludge for ATAD's must he higher than that measured in pure water. This observation matches that of Jewell and Kabrick (1980) discussed in Chapter 3. An attempt was made to estimate oxygen transfer efficiency in the sludge using 0  2  measurements in the discharge gas at the end of each feeding cycle. These estimates are discussed in Section 5.2.4.  5.2.3 Airflow Airflow during this experiment varied between 0.24 to 4.6 V/V-h for ATAD 1, and between 0.04 to 0.85 for ATAD 2. Airflow for ATAD 1 appear to generally fall within the range recommended by previous work, and airflow for ATAD 2 appear to be generally low. However, in the opinion of this author, an airflow must be quoted in relation to the concentration of the sludge feed to be oxidized, in order to have a good basis for comparison. Table 23 summarizes the average oxygen supphedWS load for each experiment. TABLE 23 Average Oxygen Supplied/VS load ATAD 1 ATAD 2 Experiment o / vsoo 0 / VS© (kg/kg) (kg/kg) 0.60 2.66 OE1 OD 0.13 0.06 OS 0.27 0.03 OE2 2.12 0.57 (a) kg 0 supplied per kg VS load 2  2  2  During some experiments, the VS concentration of the sludge fed to the ATADs varied from day to day. To keep the 0 /VS ratio constant, the airflow was varied to match the estimated 2  change in the feed sludge solids concentration. The best example of this is during the OS experiment. Figure 34 shows how airflow, VS loading, and airfiow/VS load achieved in the ATADs varied with time during that experiment. 108  ATAD 2 - OS Experiment Variation of Airflow with VS Load 1.5 1.3 1.1 0.9 0.7 0.5 0.3 0.1  450 400 350 -o 1 250 o 200 \ 150 100 50 { 0 0  T-0.1  T3  ca  0  -SP  1d 3  -0.3 -0.5 4  6  8  10  12  Experiment Day No.  -o-  Airflow  -O-  VSLoad  Airflow/VS Load  F I G U R E 34 - Variation o f Airflow with V S L o a d - O S Experiment  109  5.2.4 Discharge Gas Discharge gas constituents were detennined as another means of defining the aerobic state of each experiment. Normally, dry air contains (by volume) 78.1 percent N , 20.9 percent 0 , and 2  2  less than 0.1 percent C0 . (Ledbetter, 1972) 2  Table 24 lists the average percent by volume of N , 0 , and C0 in the air supply (assumed 2  2  2  same as laboratory air), ATAD 1 discharge gas, and ATAD 2 discharge gas. Generally, the percentage of C0 declined and the percentage of 0 increasedfromthe OD experiment to the 2  2  OE2 experiment. As described in Chapter 4, gas samples were collected at the end of the feed cycle. TABLE 24  ATAD Discharge Gas and Air Supply Quality - Percent by Volume Percent by Volume Experiment ATAD 1 ATAD 2 Air Supply CO, CO , 0,. N„. o o, ?, ?, 13.6 6.7 79.7 8.6 12.2 79.2 20.6 79.4 OD OS 7.3 14.2 78.5 6.0 15.6 78.5 20.6 79.3 OE2 1.2 18.8 80.0 2.4 18.2 79.5 19.6 80.4 ?  N  N  9  Since each experiment was done with a different air flow, the percent by volume measurements in Table 24 were converted to moles/d for a better comparison. These values are listed in Table 25. TABLE 25  ATAD Discharge Gas and Air Supply Quality - Moles of Three Constituent Gases Discharge Gas Air Supply ATAD 1 ATAD 2 ATAD 2 ATAD 1 Experiment (moles/d) (moles/d) (moles/d) (moles/d) CO, 0 N. 0 N C0 O, N O, N, 3.8 14.64 I. 08 4.17 2.51 1.24 14.69 0.45 0.64 4.16 OD 2.49 4.85 26.81 0.17 0.43 2.16 7.04 27.09 0.57 2.18 OS 3.36 52.57 223.71 1.35 10.27 44.87 54.81 224.83 II. 06 45.38 OE2 9  9  9  110  9  9  9  Oxygen balance calculations were within about 5 percent, and nitrogen balance calculations were witliin about 1 percent. Most of the experiments indicated that more nitrogen was supplied than was in the ATAD discharge gas stream The inaccuracies are probably due to a combination of method error, and the grab sampling method. Grab sampling did not reflect the changing offgas of a batch process. The OD experiment was the only one which indicated that nitrogen may have been evolved, but the difference cannot be considered significant since it is within measurement error. Oxygen transfer efficiency, as shown in Table 26, was estimated using the results shown in Table 25. For the OE2 experiment, ATAD 1 airflow rate was comparable to those used in measuring efficiency documented in Appendix 4. The clean water technique predicted about 20 percent transfer efficiency at the OE2 experiment airflow, and that there would be not enough oxygen transferred to satisfy the oxygen uptake rate measured in the OE2 experiment (discussed previously in Section 5.2.2). The following discussions will show that there was indeed enough oxygen transferred to satisfy the metabolic requirements of the bacteria, even though Table 26 shows that transfer efficiency determined using off-gas measurements was much lower than predicted with the clean water technique. The efficiency measurements in Table 26 are therefore suspect.  TABLE 26 Oxygen Transfer Efficiency Oxygen Transfer Experiment Efficiency (%) ATAD 1 ATAD 2 67 41 OD OS 31 24 OE2 .4 7  5.2.5 ORP and DO Trace Patterns Continuous monitoring of ORP and DO resulted in traces very sirmlar to the target patterns ill  described in Chapter 3. In the following sections numbered points on the ORP and DO traces are referenced in order to describe important features.  5.2.5.1 OE1 and OE2 Experiments For the oxygen excess experiments OE1 and OE2, sample ORP and DO trace patterns are provided as Figures 35 to 38. The patterns for the two experiments are similar, except that there is a much greater discrepancy between the readingsfromORP la and lb during the OE1 experiment than during the OE2 experiment. As explained in Chapter 3, one of the ORP probes in ATAD 1 was replaced after the OE1 experiment, and the very high ORP measured during that experiment is probably suspect. The characteristics of the ORP and DO trace patterns during these two experiments were:  5.2.5.1.1 ATAD 1 1. Initial ORP and DO drop upon feeding primary sludge. 2. Secondary ORP and DO drop upon feeding secondary sludge. The air supply in OE1 was higher than in OE2, so a more pronounced DO drop can be seen on the OE2 graphs. No ORP drop at this point can be seen on the OE1 graph. 3. Fast drop in both ORP and DO during an in-situ OUR test. Not seen during OE2 because in situ OUR tests were not done during the experiment. 4. Rapidrisein both ORP and DO. In both cases the ORP did not fall below -100 mV unless an in-situ OUR test was done or unless there was a feeding mistake, such as feeding with low mixing resulting in an erroneous probe response. An example of this problem can be seen at the end of the OE2 trace pattern. There was no extended period at low DO and ORP, as can be seen in the other two experiments. 5. Leveling off to a maximum ORP and DO level. At this point, either OUR and oxygen supply were in equihbrium, or the solution was saturated with oxygen. For both experiments, this point was reached within about 9 hours of feeding. The calculated beta factors, Cs(wastewater)/Cs(tap water) of 4.5/5.8 = 0.78, at the begirming of the 112  q/8ni)  nopBflU9ono3 USSAXQ  paAjossirj  00:ZI E6/0Z/I  00=6 £6/0Z/I  00=9 £6/0271  o  00:£ E670Z/I  00=0 E6/0Z/1  § H  I  00"-IZ £6/61/1 ^ rt p  00^81 £6/61/1  OO^T £6/61/1  00^1 £6/61/1  00 6 £6/61/1 :  o  o o  CN  o m  o o  o  (Am) l e p n ^ o j  o  o o  uoponpa^-uopBprxo  113  o  o o  CS  q/3ui) uopBi}n30uo3 uagAxo paAjossiQ rtosoor-vou-irfcots^o  OO^l £6/11/5  00^6 £6/11/5  00^9 £6/11/5  O  P  00:£ £6/11/5  —'  00=0 £6/11/5  00:iZ£6/0T/S  00^81 £6/01/5  00:51  £6/01/5  00^1  £6/01/5  00 6 £6/01/5 :  o <-/>  o o (Am)  o iBpuajOd  o uoponpa^-nopBpixo  114  o o  1 2 Q  00 3I £6/03/1 :  • <  i  L  00=6 £6/03/1 <  00=9 £6/02/1  I 00:£ £6/03/1  w TH  w  o  —'  00=0 £6/03/1  |  f R  00'-I3 £6/61/1  a  TO  R  Q  o 00:81 £6/61/1  TJ R  & o  00^1 £6/61/1  00^31 £6/61/1  00^6 £6/61/1 o  O CN  O  o  o  00  o  o  (Am) nnjnajod uoponpa^-nopBpxxo  115  o  CN  O •  cd CN  q/8ni)  uopBrmaoncQ  nsSAxQ PSAIOSSIQ  o  00:ZI £6/11/5  00:6 £6/11/5  00=9 £6/11/5  O Q  00=£ £6/11/5  00=0 £6/TT/5 g  cs • >  f I 00=IZ £6/01/5 2 rt Q  00=81 £6/01/5  00:51 £6/01/5  it 00:n £6/01/5  o  o CS  3  o o  © 00  o  o  SO  (Am) nnjirajod uoponpa^-nopBpixo  116  © cs  00=6 £6/01/5  ca cs  feeding cycle and 4.3/5.1 = 0.84 at the end of the feeding cycle, are well within accepted values of 0.7 to 0.98 in wastewater. (Metcalf and Eddy, 1991) During the level period in the OE1 experiment, the temperature variedfromabout 46 °C to about 53 °C. In clean water, DO saturation values in this temperature range would vary from 5.8 to 5.2 mg/L (APHA, 1989). However, a gradual 0.6 mg/L drop was not in evidence during the stable DO period of OE1. Similar conditions existed during the OE2 experiment and, similarly, no DO drop was seen either. Therefore, it is possible that the initial leveling off might be due to SOUR decreasing to the level of oxygen supply and the subsequent pattern might be a combination of decreasing 0 solubihty 2  and decreasing SOUR. 6. In-situ OUR test can be seen near the end of the feeding cycle during OE1. 7. Feeding Note that during the entire cycle, ORP stayed above -150 mV (except for in-situ OUR tests) and was mostly above -50 mV, which keeps this reactor in the aerobic range as described by Koch et al.(1988). DO levels were mostly above 1 mg/L. 5.2.5.1.2 ATAD 2 Continuous DO measurements are not available for the OE1 and OE2 experiments as explained in Chapter 4. Spot checks of DO measurements are shown for OE2, which indicate that at the end of a feed cycle, the system was definitely aerobic. Although data is not available, the author recalls that there was a drop in DO upon feeding, which rose quickly with a pattern similar to that for ATAD 1. 1. Initial slight drop in ORP upon feeding. 2. immediate rise to a plateau, followed by a slow drop in ORP over the feeding cycle. 3. Feeding. Note that during the entire feeding cycle, ORP was above 100 mV, keeping this reactor in the aerobic range as defined by Koch et al. (1988).  117  5.2.5.2 Oxygen Deprived Experiment Figures 39 and 40 show characteristic patterns for the OD experiment.  5.2.5.2.1 ATAD 1 1. Upon feeding, there was an initial rise in DO, which was possibly due to the influent secondary sludge (which was probably still somewhat aerobic). There was a corresponding average rise in ORP, which may have been due to both the DO input and the lowering of the reactor VFA concentration resultingfrommixing with a low VFA feed. There is no clear explanation why the ORP traces moved in opposite directions for a short period of time after feeding. It may have been due to a slight difference in probe placement in the reactor coupled with lower mixing levels during feeding, but the phenomenon was not seen during any other experiment. 2. A sudden rise in DO approximately 1.5 hours after feeding. This might happen if an air bubble caught on the DO probe membrane, but the pattern is seen on several days and occurs in about the same place; therefore, this explanation does not seem sufficient. The overall ORP pattern is a slow drop, then a slow rise over a 5 hour period. This pattern may correspond to the lag period of the organisms after the shock of feeding. 3. Another sudden rise in DO, which corresponds to an inflection point in the ORP measurement. This occurs about 5 hours after feeding. The results of these experiments could offer no satisfactory explanation for the phenomenon. 4. A plateau is reached by the ORP measurement, which slowly decreases over the feed cycle. Note that ORP remains below -200 mV during the entire feed cycle. 5. A small change in the measurement of ORP lb was probably due to something caught on the probe, which was carried away after a short time. 6. A similar anomaly near the end of the feed cycle was probably also due to probe fouling; this occurred often enough that the probes had to be checked for debris on a regular basis. Debris could affect either one or both probes depending on the size of  q/3ra) uopuxiuaonco uagAxQ paAjossiQ  119  l/8ra) uoncxinaouco TOSAXQ p3A|ossirj 00 S1 £6/W£ :  oo=zi £6/W£  00=6 £6/tV£  00 9 £6/W£ :  00=£ £6/fr/£  00=0 £6/W£  00=13 £6/£/£  00=81 £6/£/£  00=51 £6/£/£  00=21 £6/£/£  00=6 £6/£/£ o o >n © r - i ^ - i  o  u~>  o  o  i n i  o  o .—t •  o  «"i t  o  o o» i  o  o u-i <s i  (Am) pniusjod noponpa^-uopnppio  120  o © c i •  m i  the sludge accumulation. DO measurement decreases slowly over the remainder of the cycle, but never reaches zero due to the C0 sensitivity problem explained in 2  Chapter 4. As in Schon et al (1993) , a very low DO concentration was assumed to indicate that the organisms were consuming DO faster than the DO probe could measure it. 7. Feeding. Note that ORP was always below -200 mV, and usually below -300 mV, keeping this reactor in the anaerobic activity zone as described by Koch et al. (1988). 5.2.5.2.2 ATAD 2 1. Initial drop in ORP and DO as the oxygen deprived feedfromATAD 1 is fed to ATAD 2. 2. Long period of ORP measurements below -300 mV and DO measurements of essentially zero. This period may correspond to a period of high OUR due to the presence of easily digestible VFAs in the feedfromATAD 1. The length of the period variedfromday to day, and was non-existent when the feedfromATAD 1 had low VFA concentration and an ORP reading greater than -300 mV. A correlation was indicated between the initial VFA concentrations and the length of time the ORP curve stayed low, as noted in Figure 41. However, with only three data points, no definitive conclusions can be drawn. There was no correlation between VSS load, airflow/VSS load, or airflow. 3. A sudden increase in ORP while DO remained at about zero. The OUR must have been high enough to keep measurable DO at zero, but the ratio of oxidants/reducing agents was increasing. Peddie et al. (1988) noted that such a feature was seen in fermenters upon depletion of substrate and a loss of oxygen tension. 4. DO remains at zero, but the ORP rise is halted and remains essentially level for a period of time (which variedfromday to day).  121  Time of Low ORP Values vs. Initial VFA Concentration  • 400  500  •  600  700  800  900  1000  Time of low ORP Values (min)  FIGURE 41 - Correlation Between initial V F A Concentration and Duration of Low ORP Values : A T A D 2, OD Experiment  5.  ORP continues to rise, concurrent with a small change in the D O measurement, which begins to rise shghtly.  6.  D O measurement begins to rise at an accelerated rate and the ORP measurement begins to level off shortly afterwards. At this point there must be a definite change in the O U R  7. and 8. Anomalies in the D O curve which cannot be satisfactorily explained but which often occurred at this point in the feed cycle. 9.  Feeding  Note that ORP ranged between -350 and +150 mV. This range covers all three aeration states; anaerobic, anoxic and aerobic, defined by Koch et al. (1988). The shape of the ORP curve is similar to the pattern noticed by Peddie et al. (1988) and further discussed by Wareham et al. (1993); the possibihty of a connection is discussed in Section 5.4.3.4.  5.2.5.3 Oxygen Satisfied Experiment Figures 42 and 43 show the ORP and D O pattern during the OS experiment.  122  1/Sva) uopBfln33u03 USSHXQ paAjossia o  o  t  ^  v  O  v  i  T  t  -  c  o  c  S  —  <  ©  0 0 ^ 1 £6/6/*  0 0 6 £6/8/fr :  © o C S  ©  o * - <  o  o >-H I  o ©  o C  I  S  o  C  I  o o O  T  o o I  f  (\m) n?pn3jo<i uoponpa^-uopcpTxo  123  I  © o I  O V  o  O I  oo  r-  q/gm) uopBijuaoncQ uaSAxo paAjossiQ NO u-i -<t m CN  1 —  —1  h  1  H  1—  1  00=31 £6/6/*  cn  ...,  .ft...  00=6 £6/6/*  ;  00=9 £6/6/*  00=£ £6/6/*  J4  00=0 £6/6/*  H  I  CN  1  00=13 £6/8/* a ca  |  Q  00=81 £6/8/*  00=SI £6/8/*  00=31 £6/8/* «  o 00=6 £6/8/* o <n  |  o o  o in  o </->  (Atu) n?pn3}0^ noponpa^-noptjpixo  124  o o  5.2.5.3.1 ATAD 1 1.  Initial drop in DO and ORP upon feeding with raw mixed sludge. A double drop, as seen in the OEl and OE2 experiments is not in evidence.  2.  Period of slow rise of DO readings for about three hours, time period varying from day to day. The slow DO rise may be due to the C 0 effect noticed at the beginning of 2  this run and explained in detail in Chapter 4. During this time, ORP dropped to about -250 mV then rose to about -100 mV.  As shown in Figure 44, some correlation was  found for the length of this steady ORP period compared to the amount of primary sludge VS fed to ATAD 1 per day. The more primary sludge was fed for a given airflow, the longer the low ORP period. No correlation was seen between the length of the low ORP period during the OS experiment and influent VFA concentration, airflow/initial VFA concentration or airflow/VS load. Therefore, airflow/primary sludge VS load was the most important parameter in terms of defining ATAD 1 aeration state during the OS experiment.  ATAD 1, OS Experiment Time of Low ORP Values vs. Primary Sludge VS Load 300  •  250 200  3  150 100 50 _ i  100  1  1  1  1  1-  200  300  400  500  600  Time of Low ORP Values (ran)  FIGURE 44 - Correlation Between Duration of Low ORP Values and Primary Sludge VS Load : ATAD 1, OS Experiment 125  Inflection point in both the DO and ORP curves. The DO level rises above 1 mg/L. The ORP curve begins to level off. 4. Dip in the DO curve. This feature occurred often. This is possibly the point of maximum OUR. 5.  ORP curve is steady at+100 mV. DO curve is steadily rising. The fact that the DO curve is rising and is well below saturation level supports the hypothesis that a steady ORP curve does not necessarily mean that the system has reached saturation.  6. This small anomaly at the end of the DO and ORP curves, just before feeding, was due to checking the DO level with an outside probe, which required opening the top hatch and flooding the head space in the reactor with air. 7. Feeding. Note that ORP stayed between -250 mV and +100 mV, which covers the anoxic/aerobic range as defined by Koch et al. (1988).  5.2:5.3.2 ATAD 2 Only spot checks for DO are available for this run in ATAD 2. 1. There is a drop in ORP when feeding with partially digested sludgefromATAD 1, which is at a lower oxygenation state. The drop is lower than is expectedfromjust mixing with the feed sludge, because the mixing rate was also turned down when feeding, resulting in a reduced aeration rate. The DO spot check shows that DO concentration is over 1 mg/L shortly after feeding is complete. The author recalls that DO concentration would drop to zero during feeding then rapidly climb to the higher level once aeration recommenced. 2. ORP rapidly rises to about 140 mV, and stays there. There is a gradual rise in DO concentration as shown by the spot check. 3. Feeding. 126  Except for the lower ORP drop during feeding, this pattern is shnilar to that seen during the OE1 and OE2 experiments in A T A D 2, and is mostly in the aerobic ORP range as defined by Koch et al. (1988).  5.2.6 Alkahnity Table 27 summarizes the results of the alkalinity concentration measurements taken during the experiments. Results are average concentrations in mg/L as CaC03- Also shown is the change in alkalinity concentration that would be expected from the increase in ammonia concentration (as discussed in Section 5.3). For the OE1 experiment, the change in T D K N was used instead of the change in ammonia concentration because of the problems measuring ammonia concentration during that experiment.  TABLE 27 Alkalinity Alkalinity (mg/L as CaCO^)  Experiment  OE1 OD OS OE2  Primary Sludge  Secondary Sludge  ATAD 1 Actual  ATAD 1 Expected  ATAD 2 Actual  ATAD 2 Expected  550 370 570 440  400 420 460 530  1170 1650 1450 1300  1040 1780 1010 910  1670 1790 2130 1960  1700 2560 1670 1240  The wide variation in primary sludge afcahnity is probably due to the pilot plant practice of adding bicarbonate in batchs to the raw sewage storage tanks. The variation in the secondary sludge alkalinity may have been due to varying amounts of denitrification during the thickening process. This hypothesis is supported by the difference between the NOx levels measured in the thickened secondary sludge (see Section 5.3), and the NOx levels of 5 to 11 mg/L in the pilot plant effluent. Alkalinity was produced in both A T A D 1 and A T A D 2, and was usually higher in A T A D 2. The difference was expected, since ah\alinity concentration is related to the concentration of 127  ammonia in the reactors, and a longer digestion time results in greater hydrolyzation of organic nitrogen to ammonia. The results are comparable to the higher alkalinity of 2000 mg/L measured at the Salmon Arm plant (Kelly, 1990). The highest alkalinity concentration in ATAD 1 occurred during the OD experiment, but it was less than expectedfromthe change in ammonia concentration. Alkalinity concentration changes in ATAD 1 for the OEl, OS and OE2 experiments were greater than expected from increases in ammonia concentration. In ATAD 1, alkalinity concentration generally decreased with increasing airflow. The highest alkalinity concentration in ATAD 2 occurred during the OS experiment. The amount of alkalinity produced was far higher than would be generated by ammonification alone. The alkalinity concentrations in ATAD 2 are higher than expected for the OE2 experiment, with values about what would be expected for the OEl experiment, and.lower than expected for the OD experiment. Other factors besides ammonia concentration which would have affected alkalinity would have been phosphate release and subsequent formation of phosphoric acid, nitrMcation/demtrification, and the presence of acetic acid. To explain the differences between expected and measured alkalinity listed in Table 27, additional research would be required, includingfrequentsampling throughout the feed cycle for all factors affecting alkalinity. 5.2.7 pH Primary sludge pH ranged between 5.6 and 7.0 and secondary sludge pH rangedfrom6.0 to 7.2. Table 28 lists the range of pH values measured in the ATADs during the experiment. The pH measured in ATAD 1 is slightly higher than expected pH values quoted by the EPA (1990), whereas the measured pH in ATAD 2 is slightly lower than the expected pH values; however, the measured pH is in the general range reported by many researchers and noted in Chapter 3.  128  TABLE 28 ATAD pH Experiment ATAD 1 ATAD 2 PH PH . 7.7-8.3 7.8-8.4 0E1 6.5-7.2 7.1-7.8 OD 7.4-7.6 7.7-7.9 OS 7.8-8.0 7.7-8.0 OE2  Table 28 shows clearly that pH values increased from the oxygen deprived to the oxygen excess condition. The lower pH may have been due to the buildup of volatile fatty acids in the system at lower air inputs. Higher pH positively correlates with higher ammonia in the discharge gas; this is expected, since more ammonia is in solution at higher pH and thus is more easily stripped from the hquid. However, the effect of higher pH on ammonia concentrations in the discharge gas is probably negligible compared to the difference in airflow, since the pH change was only one unit and for all the experiments pH values were well below the optimum pH for effective ammonia stripping.  5.2.8 General Summary of me Three Aeration States IVrnumum and average measured oxygen uptake rates were within the range predicted by the EPA ATAD manual (1990), but maximum measured rates exceeded the rnaximum predicted by a factor of 3. The aeration system used during the experiments seemed to be able to meet the maximum oxygen demand, even though the measured oxygen transfer rates in water were lower than required at the maximum measured OUR in sludge. Therefore, transfer rates in ATAD sludge must be higher than those measured in clean water. The three different aeration states were primarily distinguished by the different trace patterns generated by ORP values and DO concentrations in ATAD 1. Target trace patterns were closely approximated. Air supply as kg 0 /kg VS was fairly constant during each experiment and was 2  lowest for the oxygen deprived experiment and highest for the oxygen excess experiment. Airflow measured during these experiments was generally on the low end of the range of field  129  measurements reported in Chapter 3. pH values increased as air supply rates increased. Alkalinity in ATAD 1 decreased with decreasing air supply rates and was largely due to ammonification of organic nitrogen. Alkalinity in ATAD 2 did not follow an overall pattern except that it was always higher than ATAD 1.  5.3 Supernatant Quality  This subsection discusses supernatant quality in terms of chemical oxygen demand, volatile fatty acid production, and nitrogen and phosphorus concentrations.  5.3.1 Chemical Oxygen Demand 5.3.1.1 Total Chemical Oxygen Demand Figure 45 illustrates the total chemical oxygen demand (TCOD) measured in the influent mixed sludge, ATAD 1 and ATAD 2. In the OEl, OE2 and OD experiments, the reduction in COD through each reactor is obvious, and a direct comparison between average influent COD concentrations and average effluent COD concentrations can be made to calculate approximate COD reduction. Results are listed in Table 29. For the OS experiment, the TCOD pattern in Figure 45 reflects the problem with the solids balance, and approximate COD reduction could not ;be determined. T A B L E 29  otal Chemical Oxygen Demand and Percent COD Reduction COD ATAD 2 COD Overall Experiment Influent ATAD 1 COD Reduction COD Reduction COD COD Reduction (mg/L) (mg/L) (mg/L) (%) (%) (%) 17610 11.4 37.8 . 28330 19880 29.8 OEl 29270 21630 26.1 17940 17.0 38.7 OD 20540 N/A 29160 21190 N/A N/A OS 29470 21090 28.4 18300 13.2 37.9 OE2  130  OEl Experiment Total Chemical Oxygen Demand Q O U  cs 0  1  45000 35000 25000  -a—  1500095000 1/11/93  1/13/93  1/15/93  1/19/93  1/17/93  1/21/93  1/23/93  Date (mon/d/y)  OD Experiment Total Chemical Oxygen Demand Q O U  CN  45000  o  35000  25000'•! 15000'? 5000 2/22/93  mm mm  •  .  '••  s  t 2/24/93  e  o  2/26/93  2/28/93  •  •  8  <>  o  3/2/93  3/6/93  3/4/93  Date (mon/d/y)  OS Experiment Total Chemical Oxygen Demand cs  Q 0  O U  1  45000i 35000  T1  :  15000  X  5000 3/31/93  M !  1  25000i  •  .-\  i  i  !  !  4/3/93  4/6/93  W  J  *  ?  9  4/9/93  4/12/93  6 4/15/93  O  4/18/93  Date (mon/d/y)  OE2 Experiment Total Chemical Oxygen Demand ~  45000  ^ °  35000  O  25000  * M ^  i  II  15000 9 5000 5/3/93  1r  •  6  $  i  •  •  •  •  $  8  o  9 i  j  5/5/93  5/7/93  5/9/93  5/11/93  Date (mon/d/y) Influent COD  * ATAD 1  ° ATAD2  FIGURE 45 - Total Chemical Oxygen Demand 131  5/13/93  5/15/93  TCOD reductions obtained during this experiment are within the range found for the Salmon Arm plant, (Kelly, 1990) where the time-temperature product varied from 270 to 400 °Cdays. The time-temperature product for these experiments ranged from 320 to 335 °Cdays, as was discussed in Section 5.1.7. Results are much lower than values published by Morgan and Gunsen (1987) (with the exception of their low loading situation) and Murray et al. (1990), but higher than values published by Trim and McGlashan (1984). It is interesting to note that there is no significant (hfference between the overall percent TCOD reduction found in the oxygen deprived experiment and the oxygen excess experiments. This result is not conclusive since a complete carbon balance was not done, but it appears that digester air supply rate will not affect sludge stabilization. However, there was a significantly higher degradation of TCOD in ATAD 2 during the OD experiment. This fmding is further discussed in Section 5.3.2 which discusses volatile fatty acid concentrations. 5.3.1.2 Soluble COD Figure 46 shows the change in soluble COD (SCOD) concentration after ATAD digestion. SCOD was always higher in ATAD 1 than in the influent mixed sludge, and always higher in ATAD 2 than in ATAD 1. The less oxygen supplied to the system, the higher the SCOD in the ATADs. Table 30 summarizes the results for the OD, OS and OE2 experiments. SCOD was not measured during the OE1 experiment. TABLE 30  Experiment OD OS OE2  Soluble Chemical Oxygen Demand ATAD 2 ATAD 1 influent SCOD SCOD/ SCOD SCOD/ SCOD SCOD/ TCOD TCOD TCOD (mg/L) (mg/L) (mg/L) (%) (%) (%) 160 0.5 1595 7.4 1640 9.1 100 0.3 475 2.3 715 3.5 135 0.5 380 1.8 625 3.4  132  OD Experiment Soluble Chemical Oxygen Demand  O  .1  3500 3000 A 2500 2000 A ° 1500 1000 500 0 f! 2/22/93  >  (5  •  *  ,  2/24/93  2/26/93  o •  0  •  •  o  3/2/93  2/28/93  •  3/6/93  3/4/93  Date (mon/d/y)  OS Experiment Soluble Chemical Oxygen Demand  cs O  o*  :  cj  o  i  • 3/31/93  4/3/93  9'  O  o  , — •  4/6/93  C•>  CJ  _M—,  «  V  4/9/93  4/12/93  4/15/93  4/18/93  5/13/93  5/15/93  Date (mon/d/y)  OE2 Experiment Soluble Chemical Oxygen Demand  O  Q £ 6p  A  s  <)  5/5/93  5/7/93  t  I  I  5/3/93  c  %  o  n  % •  5/9/93  i  5/11/93  Date (mon/d/y) Influent COD  * ATAD 1  °  ATAD2  FIGURE 46 -Soluble Chemical Oxygen Demand 133  Table 30 also shows how the percent soluble COD decreases with increasing air supply. Since the OD and OEl experiment results indicate that total COD reduction is the same regardless of airflow rate, solubilization of solid COD must occur faster under oxygen deprived conditions than under oxygen excess conditions. This hypothesis concurs with the results found by Kelly (1990) and Mason et al. (1987a) that VSS destruction was greater under oxygen limited conditions than under oxygen excess conditions. Some of the measured COD may be due to nitrite in the OS and OE2 experiments. However, since nitrite only accounts for 2.2 mg COD/mg nitrite, then even if all of the NOx measured were nitrite (unlikely due to the faster rate of conversion of nitrite to nitrate than for nitrite production), then about 6 percent of soluble COD would be due to nitrite in ATAD 1 and 3 percent in ATAD 2 during the OE2 experiment. Nitrite nitrogen COD levels would be negligible during the OD and OS experiments. A more significant contribution to soluble COD concentrations was made by volatile fatty acids (VFA), as discussed in the following section.  5.3.2 Volatile Fatty Acids 5.3.2.1 Influent VFA Concentrations A wide range of VFA types could be found in the thickened primary sludge in all four experiments, with acetic and proprionic acid predominating. Average concentrations for acetic acid rangedfrom36 to 66 mg/L and for proprionic acidfrom23 to 68 mg/L. Isobutyric, butyric, A-valeric and isovaleric acid were present in much smaller amounts - the highest average concentration being 3 mg/L for butyric acid. The thickened secondary sludge contained hardly any volatile fatty acids; this was expected since every effort was made to prevent fermentation of the secondary sludge. The highest average acetic acid concentration was 2.9 mg/L, for the OE2 experiment.  5.3.2.2 ATAD 1 VFA Concentrations A great difference was seen between the VFA concentrations measured during the OEl, OE2 134  and OS experiments and the V F A concentrations obtained for the P D experiment. The OE1, OE2 and OS experiments measured low V F A concentrations, usually only acetic acid, with the highest average of 5.2 mg/L occurring in A T A D 1 during the OE1 experiment. Very high V F A concentrations, especially acetic acid, were measured during the OD experiment, as shown in Figure 47.  OD Experiment Volatile Fatty Acids ATAD 1 1200 1000 800 8 1E 600 400 200 0  |  g vo  Date (mon/d/y) Acetic  Propionic  I  Iso-Butyric  A-Valeric  L~ZI Butyric  ffl  Iso-Valeric  •  Valeric  OD Experiment Volatile Fatty Acids ATAD 2 450 400 350 a 300 250 200 150 100 50 0  g  g in  cn  g  m  g  C5 ?1  ?5  ?1  g  g oo  Date (mm/dd/yy) Acetic  Proprionic  I  Iso-Butyric  II A-Valeric  M Iso-Valeric  FIGURE 47 - OD Experiment A T A D Volatile Fatty Acid Concentration  135  All VFA samples were collected at the end of the feed cycle, and during the OE1, OE2 and OS experiments, ORP values were high at the end of the feed cycle. Low VFA concentrations under such high ORP conditions match the results of Chu et al. (1994). During the OD experiment, ORP values were low at the end of the feed cycle and the resulting high VFA concentrations again confirm the fmdings of Chu et al. (1994).  5.3.2.3 ATAD 2 VFA Concentrations The OE1, OE2 and OS experiments exhibited similar VFA results, with either low or zero acetic acid concentrations. Zero acetic acid concentration was expected, since during these experiments the sludge fed to ATAD 2 had low acetic acid concentrations and conditions in the digester were aerobic with high ORP values and DO concentrations greater than 1 mg/L. Attempts to correlate the final VFA concentration to airflow rates, airflow rate/VS concentration in the reactor, VS concentration in the reactor, airflow rate /g VS applied, and g VS applied were not successful. There is at present no published satisfactory explanation for the recurring phenomenon of residual acetic acid in ATAD 2 at the end of a feed cycle. The occurrence of proprionic acid during the OE2 experiment is an anomaly and was probably due to sample contamination. The ATAD 2 samples collected during the OD experiment contained high VFA concentrations as shown in Figure 47, but VFA concentrations were, overall, lower than in ATAD 1. This was expected, since VFA was likely degraded during the period of high ORP values and high DO concentration near the end of the feeding cycle. The VFA degradation from ATAD 1 to ATAD 2 during the OD experiment may account for the comparably high COD reduction between ATAD 1 and ATAD 2 shown in Table 29. However, the VFA degradation does not correlate with the soluble COD results in Table 30, which showed an increase from ATAD 1 to ATAD 2 during the OD experiment. This result is discussed in the next subsection.  136  5.3.2.4 VFA Contribution to COD Using the conversion factors given in Chapter 3, the average amount of soluble COD attributed to the presence of volatile fatty acids were calculated, and are shown in Table 32.  TABLE 31 Average COD Concentration due to VFA Experiment Influent ATAD 1 ATAD 2 (mg/L) (mg/L) (mg/L) 416 1078 89 OD OS 38 3.3 3.1 OE2 76 3.9 4.0  Table 32 shows that only about half of the influent soluble COD concentration is due to VFA. During the OD experiment, VFA accounted for 68 percent of the soluble COD concentration in ATAD 1 and 25 percent of the soluble COD concentration in ATAD 2. During the OS and OE2 experiments, VFA accounted for less than 1 percent of the soluble COD concentration measured in both ATADs. This suggests that the soluble COD content of supernatantfromoxygen satisfied ATADs may not be easily biodegradable.  5.3.3 Nitrogen 5.3.3.1 Influent Nitrogen Figure 48 shows that the variation in the influent mixed sludge nitrogen concentrations was minimal. Table 32 shows the average influent nitrogen loading, including values for thickened primary and secondary sludge as well as for the influent mixed sludge. Most of the TKN was in particulate organic form, (97.7 to 99.0 percent) which was expected from a primary or secondary sludge. The combined TKN levels are lower for the OEl experiment than for the others, because less secondary sludge was used in the mix during that experiment and secondary sludge contained higher concentrations of TKN than primary sludge.  137  OE1 Experiment Influent Nitrogen I o 2000 <8 w 1500 u  500 0* 1/11/93  •  - O  1J  Q-  LJ  L  J  •  -U  ^  LJr-  '—i  •  LJ  rn LJ  -X-  1/15/93  1/13/93  1/17/93  1/19/93  1/21/93  1/23/93  3/4/93  3/6/93  ><  x —— x — — x  •  4/13/93  4/15/93  4/17/93  5/13/93  5/15/93  Date (mon/d/y)  O D Experiment Influent Nitrogen | ^ 2000 «g ^ 1500 § j 1000°" 500  g ~  o  2/22/93  2/24/93  2/26/93  2/28/93  3/2/93  Date (mon/d/y)  O S Experiment Influent Nitrogen § _ 2000 \ 1500 g JX 1000 1 2 500  1  •  —  — -0- —"^  I  X  £  X —  4/5/93  _  x  4/7/93  •••d—— •  X  X —  4/9/93  d  — x — —x  4/11/93 Date (mon/d/y)  OE2 Experiment Influent Nitrogen  5/3/93  5/5/93  5/7/93  5/9/93  5/11/93  Date (mon/d/y) •  TKN  o  TDKN  o  NOx  x  NH3  F I G U R E 48 - Influent Sludge Nitrogen Concentration 138  TABLE 32 Average ISfitrogen Concentrations in Influent Thickened Sludge NOx NH TDKN TKN Experiment Sludge Type (mg/D (g/d) (mg/L) (g/d) (mg/L) (g/d) (mg/L) (g/d) OEl 0.3 0.00 29 0.46 29 0.47 565 9.25 Primary 0.6 0.00 3 0.03 5 0.04 Secondary 1520 12.65 0.4 0.01 20 0.49 21 0.51 885 21.89 Mixed 3  OD  Primary Secondary Mixed  600 1715 1180  7.17 22.27 29.44  34 17 25  0.41 0.22 0.63  31 15 23  0.37 0.19 0.56  0.2 0.3 0.2  0.00 0.00 0.01  OS  Primary Secondary Mixed  435 1570 1025  5.20 20.39 25.59  25 3 13  0.30 0.04 0.34  21 I II  0.25 0.02 0.26  0.2 0,2 0.2  0.00 0.00 0.01  OE2  Primary Secondary Mixed  600 1580 1110  7.20 20.52 27.72  21 2 11  0.25 0.03 0.28  17 1 9  0.21 0.01 0.22  0.2 0.2 0.2  0.00 0.00 0.01  Most of the influent TDKN was in the form of ammonia (79.1 to 95.2 percent). The nitrate levels in the thickened primary sludge were low as expected. The thickened secondary sludge probably had higher nitrate levels whenfirstwasted from the extended aeration plant, (averaging about 8 mg/L NOx according to pilot plant records), but since sludge thickening took an average of 2 hours, the thickened secondary sludge was likely denitrified to the influent levels shown in Table 32.  5.3.3.2 Nitrogen Balance Table 33 shows the results of the nitrogen balance for all four experiments. Nitrogen balance calculations were based on total nitrogen g/d including TKN, NOx, and ammonia in the off-gas. Expected measurement error is based upon TKN variation. Detailed calculations can be found in Appendix 2. Ammonia in the discharge gas was measured during the OS and OE2 experiments, at the end of each feeding cycle. It was expected that the ammonia discharge gas concentrations would be  T A B L E 33  Nitrogen Mass Balance Total Nitrogen (g/d) Nitrogen Source OE1 OD OS 5.20 9.25 7.17 Thickened Primary Sludge Thickened Secondary Sludge 12.65 22.27 20.39 Total influent Sludge 21.90 29.45 25.60 Sampling and Pipe Loss 0.92 1.25 1.09 ATAD 1 Sludge In 19.85 25.52 23.59 Discharge Gas N/M N/M 0.00 Total ATAD 1 Out 20.77 26.77 24.68 -3.6  OE2 7.20 20.52 27.73 1.06 23.96 0.13 25.15  ±8.2  -9.3 ±7.7  24.61  23.59 25.47 0.00 25.47  23.96 23.37 0.13 23.50  +5.8  -3.6  +8.0  -1.9  Expected Error (%)  +6.3  ±4.5  ±6.1  . ±6.1  System Mass Balance (%)  -0.1  -12.2 ±7.2  +3.8  -11.0 ±7.7  Expected Error (%)  ±11.6  -9.1 ±8.1  ATAD 2 In ATAD 2 Out Discharge Gas Total ATAD 2 Out  19.85 21.01  25.52 24.61  N/M  N/M  21.01  ATAD 2 Mass Balance (%)  ATAD 1 Mass Balance (%)  Expected Error (%) N/M = Not Measured  -5.2  +10.9  ±9.2  the highest at this time, due to the combination of high ammonia concentration, high pH, and high temperature. As can be seen in Table 33, the amount of nitrogen lost as ammonia in the discharge gas was negligible during the oxygen satisfied experiment, and only mmimal during the oxygen excess experiment. Ammonia concentration in the discharge gas was not measured directly during the OD experiment, but on several occasions a large amount of discharge gas was pumped through an indicator solution used for ammonia reflux testing and no colour change was observed. Therefore, it seems likely that ammonia lost with the discharge gas during the OD experiment was also negligible. Ammonia in the discharge gas was not tested for during the OE1 experiment, but was probably comparable to the levels measured during the OE2 experiment. All nitrogen balance calculations for the mdividual reactors were within ± 10 percent, and all nitrogen balance calculations for the system were within ± 15 percent. Most of the balances were witnin expected measurement error or within a few percentage points of expected measurement 140  error. For those balances which were outside the expected measurement error, the expected measurement error is highUghted. For the ATAD 1 OD balance, the ATAD 1 OE2 balance, and the ATAD 2 OS balance, the difference between expected and actual error was always less than 2 percent, so are not regarded as significant. Both the OD and OE2 experiments had a negative nitrogen balance for the system and negative balances for both of the individual reactors, indicating a loss of nitrogen in the system The most likely cause would be denitrification, which would have resulted in nitrogen gas leaving the system with the discharge gas. As already noted in Section 5.2.4, the differences between discharge gas nitrogen content and the air supply nitrogen content was not significant, which is why nitrogen in the discharge gas was not included in the nitrogen balance. However, slightly elevated N content in the discharge gasfromATAD 1 during the OD experiment indicated that 2  denitrification may have been occurring. The ATAD 1 environment could have supported mtrification/denitrification. During the OD experiment, DO concentration was generally below 1 mg/L, which would allow denitrification; also, Figure 14fromPeddie and Mavinic (1988) shows that nitrification can also take place at DO concentrations less than 1 mg/L. During the OE2 experiment, there was a period near the beginning of the feed cycle of about half an hour under 1 mg/L DO (Figure 36) followed by positive DO conditions. However, N levels in the discharge gas during that experiment do not 2  confirm denitrification, possibly because the discharge gas sample was collected at the end of the feed cycle and was not representative. The OS experiment nitrogen balance was good, even though the solids balance was not (discussed in Section 5.2).  This was because the nitrogen input to the system was dominated by  the secondary sludge solids concentration which varied very little. With the alternating negative/positive ORP environment which existed in ATAD 1 during that experiment, mtrification/denitrification would have been expected but, again, nitrogen levels in the discharge gas do not support that hypothesis. Overall, denitrification could have been occurring but there is insufficient evidence to support that explanation of the negative balances for the OD and OE2 experiments. 141  5.3.3.3 ATAD 1 and ATAD 2 Nitrogen Concentrations Table 34 summarizes the average nitrogen concentrations in each tank.  Experiment OEl OD OS OE2  TABLE 34 ATAD Average Nitrogen Concentrations TDKN/TKN Digester TKN TDKN NH mg/L percent mg/L mg/L 3  NOx mg/L  312 497  288 486  35 53  9.15 9.05  ATAD 1 1075 ATAD 2 1035  480 723  520 740  46 69  0.15 0.30  ATAD 1 980 ATAD 2 1045  324 511  293 479  29 45  0.95 0.65  995 970  300 454  262 435  25 44  10.40 9.70  ATAD 1 ATAD 2  ATAD 1 ATAD 2  835 890  As can be seenfromTables 32 and 34, the concentration of dissolved nitrogen increased dramatically between the influent mixed sludge and ATAD 1, and between ATAD 1 and ATAD 2. The OD experiment showed the highest level of nitrogen solubilization, approaching 70 percent. The OEl experiment showed the next highest level of nitrogen solubilization; the OE2 and OS experiments showed about the same level of nitrogen solubilization. Carrington et al. (1991) measured about 38 percent nitrogen solubilization and Murray et al. (1991) measured 22 percent solubilization.  5.3.3.4 Nitrate and Nitrite (NOx) As shown in Figure 49, during the OEl and OE2 experiments, NOx concentration was significantly higher in the ATAD reactors than in the influent mixed sludge. Also, there was on average less NOx in ATAD 2 than in ATAD 1 even though ATAD 2 was more aerobic than ATAD 1. This may have been due either to higher substrate availability for nitrifiers in ATAD 1 than in ATAD 2, or to higher average temperatures in ATAD 2 (since nitrifiers are reportedly 142  O E l Experiment Nitrates + Nitrites  8  2  16.00 c> 12.00' 8.00 4.00  0 — o —  D—  ,Y  O  \ '<V...  O-—  1/11/93  ;  —6—  r"  o-  1/15/93  1/13/93  <>.,..  o  )  6 -••V o —6—  o  1/17/93  o' n  6 — r i  1/21/93  1/23/93  3/4/93  3/6/93  4/15/93  4/17/93  1/19/93  Date (mon/d/y)  OD Experiment Nitrates + Nitrites 16.00 12.00 8.00 4.00 S 0.00E 2/22/93  2  2/24/93  2/26/93  2/28/93  3/2/93  Date (mon/d/y)  OS Experiment Nitrates + Nitrites  8 z  2  I  16.00 12.00 8.00 4.00 0.00 4/5/93  4/7/93  4/9/93  4/11/93  4/13/93  Date (mon/d/y)  OE2 Experiment Nitrates + Nitrites 16.00  *! f  A.  1200  4.00  0  0.00 5/3/93  o  \ c \ O j 5/5/93  "  T 0  O  > ...,.\ <>"' o 1 ! I  5/7/93  '^:r. n  5/9/93  !  •-  '  o  ,  -"••<>-  k  5/11/93  5/13/93  Date (mon/d/y) ATAD 1  Influent  F I G U R E 49 - A T A D N O x Concentrations 143  ATAD 2  °  c  5/15/93  inhibited at high temperatures). ATAD 1 always had a short period each day when the temperature was below 40 °C. NOx concentrations were higher during the OE2 experiment than during the OE1 experiment, which was not expected since the OE1 experiment's airflow rates were higher. This might be explained by the in-situ oxygen uptake rate measurements which were done during the OE1 experiment, causing nitrates to be consumed as the dissolved oxygen level fell, and resulting in the pattern seen in Figure 49. Another possibe explanation for the OE1 experiment's lower measured NOx concentrations might be the relatively high coefficient of variation resulting from sample freezing. In Figure 49, OE2 also shows a fairly large variation in measured NOx concentration, but this time it is not due to in-situ OUR tests or to poor precision, but rather to power losses, operator error in forgetting to increase the speed of the aerator/mixer rotation after making some measurements, or in forgetting to turn the air supply on after aerator cleaning. The conclusion here is that the concentration of NOx in the reactors was sensitive to any small changes in the feecling and testing routine which caused DO concentration to drop for even a short amount of time, thus allowing denitrification to take place. Another conclusion is that denitrification is not inhibited by high temperatures. During the OD experiment, the NOx concentration in ATAD 1 was about the same as for the influent mixed sludge, and in ATAD 2 was slightly higher. The level area on the ORP trace for ATAD 2 during this experiment (as shown in Figure 14) might correspond to the nitrate knee identified by Peddie et al. (1988). Theoretically, the initial increase of ORP values with low DO concentration would correspond to nitrification, the period of ORP constant values with low DO concentration would represent a time where demtrifiers could reduce the NOx being generated, and fmally the increase of ORP values with a conesponding increase of DO concentration would signal where aerobic respiration became dominant in the system Detailed measurements of nitrogen forms during this mode of operation would be necessary to confirm this theory. A very small amount of nitrification was observed during the OS experiment, possibly due to mtrification proceeding at inhibited rates (due to high temperature) during the aerobic periods 144  preceding daily feeding. From the above discussion, and the inference of nitrification/demtrification occurring during the OD experiment as well, it is clear that even if nitrifiers are inhibited, they can survive at thermophuic temperatures, and that denitrifiers are active at thermophilic temperatures.  5.3.4 Phosphorus 5.3.4.1 Influent Phosphorus In this research, most of the variation of influent mixed sludge total phosphorus concentration shown in Figure 50 is due to variations in thickened secondary sludge solids concentration, caused by changes in waste sludge supply and dewatering characteristics. The amount of sludge which could be wastedfromthe Bio-P pilot plant was a function of plant performance. For example, low temperature affected the wasting rate during the OEl experiment, which was why there was less waste secondary sludge available than during the other experiments (8 L as opposed to 13 L), and a correspondingly lower influent P concentration. After the OEl experiment, provision was made to use another pilot plant (incorporating a trickling filter) as a backup supply of Bio-P waste secondary sludge. This sludge was characterized by very good settling characteristics, and a somewhat higher percent P content than waste secondary sludgefromthe UCT process. For the firstfivedays of the OD experiment, the proportion of waste secondary sludge feed to the ATADs was 30 percentfromthe trickling filter process and 70 percentfromthe UCT process. For the remainder of the OD experiment all secondary sludge wasfromthe UCT process and there is a corresponding slight drop (<10 percent) in total influent P concentration. rXuing the OS experiment, all the waste secondary sludge wasfromthe UCT process. During the OE2 experiment, waste secondary sludge was initiallyfromboth processes, but the amount of secondary sludge availablefromthe tricklingfilterprocess droppedfrom50 percent down to 15 percentfromDay 1 to Day 7. There was a corresponding drop in phosphorus levels from Day 1 to Day 4. Another slight drop in total influent P concentration can be seen after day 7, when tricklingfiltersludge use was discontinued. 145  OE1 Experiment Influent Phosphorus Concentrations  8 ^ 800 g  200 y 0<^ 1/11/93  Ou  •  a  Q  D  1/13/93  •  o  1/15/93  •  1/17/93  •  •  1/19/93  M  u  u  1/23/93  1/21/93  Date (mon/d/y)  O D Experiment Influent Phosphorus Concentrations  a  8 0 0  a 3 s g> 400T 6 0 0  g--  5  I  •  —  •  p -  200  -• 6— 2/22/93  2/24/93  /\  — 6 —  <v  -<^>--.  —o  2/26/93  •  i  2/28/93  3/2/93  o  ..A  3/6/93  3/4/93  Date (mon/d/y)  O S Experiment Influent Phosphorus Concentrations  8  8 0 0  « o.  3 &  I OH  1a> s  600 a— 400 200 0  i —  4/5/93  r—1  LJ—  — o — —6— 4/7/93  — n  6— — o —  6—— o  o— — 6 — —o 4/9/93  n LJ  V  4/11/93  4/13/93  —6—  — o —  4/15/93  4/17/93  5/13/93  5/15/93  Date (mon/d/y)  OE2 Experiment Influent Phosphorus Concentrations  5/5/93  5/7/93  5/9/93  5/11/93  Date (mon/d/y) Total Dissolved P  Total P  F I G U R E 50 - Influent Phosphorus Concentrations 146  Table 35 summarizes the average P characteristics for the mixed influent sludge. As noted above, the total phosphorus (TP) values are about 70 percent lower for the OEl experiment than for the other experiments because of the smaller volume of waste secondary sludge (64 percent less) in the influent mixed sludge. The variation in total dissolved phosphorus measurements between the four experiments is probably due to different sample preservation techniques as discussed in Chapter 4. In all four experiments, most of the influent phosphorus (> 97 percent) was in particulate form. T A B L E 35  Influent Mixed Sludge Phosphorus Concentrations Total Total Total Experiment Total P Dissolved Suspended Suspended P P P /Total P (mg/L) (mg/L) 0.97 310 300 OEl 9.1 OD 440 14.2 425 0.97 OS 435 4.9 430 0.99 OE2 475 7.1 465 0.99  Phosphate (PO4) was also measured during these experiments but the values are not reported because problems with preservation (discussed in Chapter 4) rendered these results questionable.  5.3.4.2 Phosphorus Mass Balance Table 36 lists the TP mass balance and estimated measurement errors for each experiment. Detailed calculations are in Appendix 2. All of the phosphorus mass balances are within expected measurement error except for the balance around ATAD 2 during the OEl experiment, and since it is within 2 percent of the estimated measurement error, the difference is not regarded as significant.  147  TABLE 36 OEl Experiment  Total Phosphorus Mass Balance OD Experiment OS Experiment  OE2 Experiment  Actual Expected Actual Expected Actual Expected Actual Expected Error Error Error Error Error Error Error Error (%) (%) (%) (%) (%) (%) (%) (%) -4.5 -5.4 ATAD 1 -4.5 -6.9 ±8.0 ±12.2 ±12.3 ±8.9 ATAD 2 +10.6 -1.0 ±7.3 +5.8 ±8.8 -1.6 ±7.5 ±8.9 System +5.1 -7.8 ±8.0 +0.8 ±13.1 -6.9 ±8.7 ±12.2 Balance For:  5.3.4.3 ATAD Phosphorus Concentrations Table 37 summarizes the average total phosphorus concentration (TP), total dissolved phosphorus concentration (TDP), and the fraction of total dissolved phosphorus in ATAD 1 and ATAD 2. TABLE 37 ATAD Average Phosphorus Concentrations ATAD 2 ATAD 1 TDP TDP TP TDP TDP TP Experiment /TP /TP (mg/L) (mg/L) (%) ( g/L) (mg/L) (%) 56 295 152 52 330 185 OEl OD 410 269 66 405 311 77 410 183 45 430 197 46 OS 450 215 48 440 225 51 OE2 m  Dissolved phosphorus fractions in the ATADs were much higher than in the influent mixed sludge. The dissolved phosphorus fractions shown in Table 38 (46 to 77 percent) roughly correspond with the 50 to 70 percent range that Popel and Jardin (1994) identified as the amount of TP in Bio-P sludge which is contained in poly-P storage. This suggests that most of the stored poly-P phosphorus was released during ATAD stabilization. In ATAD 1, the lowest soluble P fraction was measured during the OS experiment, and the highest soluble P fraction was measured during the OD experiment. The soluble P fraction 148  measured during the OE experiments were slightly higher than those measured during the OS experiment. The difference between the two OE experiments is not considered significant because it was within the estimated measurement error for TDP. The soluble P fraction was always higher for ATAD 2 than for ATAD 1, but the highest conversion of suspended P to soluble P occurred during the OD experiment. The least measured conversion of suspended P to soluble P from ATAD 1 to ATAD 2 was during the OS experiment. The above results imply that more phosphorus will be released in an oxygen deprived condition than in an oxygen excess condition, and that phosphorus release will be minimized in an oxygen satisfied condition. Table 38 estimates the average percent P in the total volatile suspended solids for secondary sludge, influent mixed sludge, ATAD 1 and ATAD 2. For both secondary sludge and influent mixed sludge, dissolved solids were assumed to be negligible and VSS approximately equal to VS. This assumption would have resulted in, at most, a 3 percent error in the values quoted in Table 39 if dissolved solids in the influent mixed sludge were on the order of 300 mg/L as for a medium strength sewage (Metcalf and Eddy, 1991). The percent P in the secondary sludge matches that obtained by Anderson and Mavinic (1993) in their experiments with Bio-P sludge from the same pilot plant. The total suspended percent P in the influent mixed sludge for the OD, OS and OE2 experiments were very similar, within a small range of 2.4 to 2.7 percent; therefore, these experiments will be used to compare percent P in VSS in the ATAD's under differing aeration conditions. TABLE 38  Total Suspended P as Percent of Volatile Suspended Solids Suspended P/VSS (%) Secondary Influent ATAD 1 ATAD 2 Experiment Sludge Mixed Sludge OE1 3.8 1.8 1.0-1.1 1.1-1.2 OD 4.1 2.4 0.9-1.0 0.7-0.8 OS 3.9 2.6 1.6-1.8 1.7-1.9 OE2 4.3 2.7 1.7-1.9 1.8-2.0 149  Percent P in VSS in the ATADs is given as a range, based upon estimated high and low VSS concentrations and including the estimated errorfrompossible additional release of soluble phosphorus due to sample preservation. Detailed calculations are in Appendix 5. Percent P in VSS in the ATADs was generally 2 percent or lower, indicating that the biological population was very similar to that found in a conventional activated sludge and was only storing a very small amount of polyphosphate. Also, there was again a definite difference between oxygen excess or satisfied conditions and oxygen deprived conditions. The percent P in VSS for the OD experiment indicated that there was no polyphosphate storage in the microbial species in those tanks. Percent P in VSS was very close to the 0.86 percent quoted by Metcalf and Eddy (1991) as being required for cell structure and metabolism. This result closely parallels that of Jardin and Popel (1994), who found that the poly-P content of their digested sludge samples tended to be zero. In contrast, the percent P in VSS for the OE2 experiment and the OS experiment approached 2.0. The reason for the difference in dissolved and suspended phosphorus forms at varying aeration states is not clear. Jardin and Popel (1994) found that part of the phosphorus released in ATADs was precipitated with magnesium and with ammonia, as struvite. The amount of total struvite P fixation was generally 20-30 percent. Struvite formation in sludge pipes is sometimes controlled in full scale plants by adding CO2 to the sludge, thus lowering sludge pH and increasing alkalinity. The OD experiment with the highest dissolved phosphorus measurements also had the highest CO2 concentration in the ATAD off-gas, the lowest sludge pH and the highest sludge alkalinity. Conditions were the opposite for the OEl experiments; therefore, struvite formation may have been more likely which would have resulted in the lower dissolved phosphorus concentrations which were measured. Another explanation for the differences in dissolved phosphorus measured during the oxygen excess, oxygen satisfied, and oxygen deprived experiments might be the action of viable Bio-P bacteria. Anderson (1989) reported that anywherefrom13 to 50 percent of accumulated Bio-P would be released back to solution by viable Bio-P bacteria when they encountered mesophilic aerobic conditions; this is followed by subsequent slow release associated with endogenous 150  conditions. This description seems to fit the conditions in the ATADs, because there was an initial release seen in ATAD 1, and a subsequent small increase in soluble P in ATAD 2. The high overall release seen in the OD experiment may have been due to the Bio-P bacteria reacting to the low DO and high VFA environment before they were inactivated by higher temperature. However, there was not a significant (lifference in percent P in VSS between the OD and OS experiments; therefore, the lower release in the OS experiment was more likely due to higher pH and higher ammonia concentration encouraging precipitation of struvite than to the presence of thermophihc Bio-P organisms. The main conclusion to draw from this section is that most of the phosphorus stored in the BioP sludge will release in an ATAD environment, and that more will release under OD conditions than under OS or OE conditions.  5.3.5 Summary of Supernatant Quahty The same amount of total COD reduction occurred under the OD experiment conditions as under the OE experiment conditions. There was more soluble COD present under the OD experiment conditions, with progressively less soluble COD in the ATADs as the airflow/VS load increased. Concentrations of VFA's were high as long as conditions remained oxygen deprived, but extended high ORP values and DO concentrations resulted in low VFA concentrations. A high percentage of TKN was metabolized to NH in the ATAD reactors. More 3  ammonification was observed under the OD experiment conditions than under the OE experiment conditions. Nitrification did occur in the ATADs, especially at the higher air flows. There is some indication that denitrification may also have occurred. Most of the phosphorus stored in the Bio-P sludge released to solution in the ATADs. More P released under the OD experiment conditions than under the OE experiment conditions, and the smallest release occurred under alternating anoxic/aerobic conditions.  151  5.4 Full Scale Implications of Experimental Results As discussed in Section 2.0, the quality of supernatant returnedfroma sludge digester to the head of a wastewater treatment plant significantly increases various loads on the plant and affects the plant design life. This sectionfirstcompares the supernatant quality deterrnined for the pilot scale ATADs used in this experiment with that of different types of digesters. Next, the potential impact of recycling ATAD supernatant is discussed, followed by the implications of these results for full scale ATAD operation. Calculations are in Appendix 6. 5.4.1 Comparison with Other Types of Digesters. 5.4.1.1 Solids ATAD digested sludge produced during this research project exhibited very poor gravity settling characteristics; therefore, mechanical dewatering would be required in full scale operation. After laboratory centrifuging of 1.9 percent TS ATAD digested sludge, supernatant contained suspended solids on the order of 1400 mg/L (Section 4.5.2.2), or about 7.5 percent of the digested sludge solids. In full scale operation, mechanical dewatering of digested sludge produces filtrate containing anywherefrom5 to 20 percent of the digested solids, depending on the type of dewatering process (EPA, 1989). In a full scale ATAD system with 3 percent TS feed and 40 percent VS destruction, the solids feed to the dewatering process would be about 2 percent, and the filtratefromthe dewatering process could contain anywherefrom1000 to 4000 mg/L SS. This range is comparable to those quoted in Chapter 2 for supernatantfromanaerobic and aerobic mesophilic digesters. The following supernatant parameter estimates assume a supernatant solids content offrom1000 to 4000 mg/L.  5.4.1.2 COD and VFA The TCOD in ATAD supernatant could vary between 1900 and 5900 mg/L, depending on airflow rate and solids content. These values are similar to those reported for mesophilic aerobic digesters, and on the high end of those reported for mesophilic anaerobic digesters.  152  Based upon the results of this research, VFA's in the supernatant could vary between 0 to 1000 mg/L. The maximum concentration value of 1000 mg/L is higher than the VFA concentration measured in supernatant from both aerobic and anaerobic mesopbilic digesters.  5.4.1.3 Nitrogen In an ATAD digestion process producing digested sludge containing 1.5 percent VS, supernatant could contain ammonia concentrations between 580 to 870 mg/L, and TKN concentrations between 610 to 940 mg/L, depending on airflow rate and supernatant solids content.' This range is well above that for mesophilic aerobic digesters and is close to that expected for mesophilic anaerobic digesters. Under oxygen excess conditions, the NOx measured in the pilot scale ATADs was close to the 10 mg/L recommended for well operating aerobic digesters. Under oxygen deprived conditions, the NOx in ATAD supernatant would be negligible.  5.4.1.4 Phosphorus A very high dissolved phosphorus concentration was measured in ATAD sludge supernatant during this research, because the digesters were fed with Bio-P secondary sludge. Assuming mixed sludge consisting of 50 percent Bio-P thickened secondary sludge of 3 to 4 percent TP/VS, dissolved phosphorus in ATAD supernatant could rangefrom290 to 370 mg/L and total phosphorus could rangefromabout 300 to 390 mg/L TP. These ranges are higher than concentrations reported for anaerobic and aerobic digesters treating conventional waste secondary sludge. This result is not surprising, firstly because of the higher phosphorus content of Bio-P sludge, and secondly because these experiments have shown that stored Bio-P phosphorus is released under ATAD conditions.  5.4.2 Effect of ATAD Supernatant on Bio-P Plant Influent. As discussed in Chapter 2, digester supernatant returnflowrate can be estimated as about 1 percent of plant influentflowrate. Using the average influent concentrations for a medium 153  strength wastewater as given by Metcalf and Eddy (1991), the impact of return flowsfroman ATAD faculty treating Bio-P sludge (as described previously) can be estimated. Table 40 shows a range of recycled contaminant concentrations, which vary with airflow rates and with solids concentrations. T A B L E 39  Estimated Effect of ATAD Supernatant Recycle On Influent Flow Concentrations and Loads Altered Influent Load Change Influent Recycle High Low High High Low Parameter Low (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (%) (%) 5 18 1000 4000 230 255 220 SS COD 500 1910 5860 515 555 4 12 20 610 940 26 29 30 47 TKN NH 8 575 14 16 72 108 865 NOx 0 0 10 0.0 0.1 0 TP 4 300 395 7 8 75 99 TDP 3 285 370 6 7 95 124 3  The estimates listed in Table 39 are rough, since they do not incorporate an iterative method which allows for plant adjustment to the higher strength influent. Nevertheless, the general trends can be easily seen. Most design parameters are significantly affected by the quality of supernatant return, with the exception of nitrates, which rise just above measurable concentrations. Any biological wastewater treatment plant would be affected by the potential increase in SS and COD loading shown in Table 39, but the major impact of supernatantfroman ATAD treating Bio-P sludge isfromVFA, nitrogen and phosphorus loading. The total phosphorus load on the plant might be increased by almost as much as 100 percent, indicating that most, if not all, of the phosphorus removed by the Bio-P process can be returned with ATAD supernatant if steps are not taken to mitigate the problem The total nitrogen loading is increased by up to 47 percent which affects: 1. Nitrification/denitrification processes 2. The amount of aeration required in the aeration basin if a plant does nitrify 154  3. The success of a Bio-P operation because of the lowered BOD/TKN ratio. The estimated increase in COD load of up to 12 percent would not balance the increase in TKN, therefore denitrification may occur in the anaerobic zone at the expense of phosphorus release by Bio-P bacteria. However, the increase in VFA's in the plant influent would be beneficial to both phosphorus removal and denitrification. The total effect of the change in plant influent quality is therefore difficult to quantify, due to the various and combined effects of ATAD supernatant constituents on a Bio-P plant. The high nutrient returns in ATAD supernatant may be beneficial if the wastewater requhing treated was nutrient deficient, as is the case with some industrial waste streams. ATAD would be especially effective in recycling ammonia, since ammonia releasefrommost biological sludges (baixing inorganic precipitation) is likely to be high. Phosphorus recycling would not be as likely in such a situation, since dissolved phosphorus concentrationsfroman ATAD treating non Bio-P sludge would probably be similar to that expectedfrommesophilic anaerobic and aerobic digesters. Dissolved phosphorus concentrations were 30 mg/L during early trials with the experimental equipment using thickened primary sludge only. Therefore, an ATAD system might be only minimally useful for supplementing influent P concentrations in a nutrient deficient wastewater.  5.4.3 hnphcations for Full Scale Operation of ATAD The results of this research project indicate that the same VS and TCOD reduction can be achieved using lower airflow/VS load as compared with higher airflow/VS load, if the digester is well mixed. Thisfindingmight translate to a modification in design philosophy for ATAD digesters: it indicates that money is better spent on mixing rather than on oxygen transfer. However, lower airflowsbring other operational problems, namely dramatic changes in supernatant quahty and generation of foul odours. For example, the presence of butyric acid in the ATADs during the OD experiment caused the off-gas to be very odourous. Such a condition might be very difficult to promote given the increasingly stringent odour control requirements demanded by the public for wastewater treatment plants. 155  On the other hand, at higher airflow, ATAD discharge gas and digested sludge were less odourous and supernatant quality was better, especially for the OS experiment which had alternating periods of oxygen deprivation and oxygen excess and appeared to release less phosphorus to solution. Operation of ATADs using an air on/off cycle, or perhaps varying the amount of aerators running at one time may be a compromise solution to opposing requirements of optimizing supernatant quality versus minimi zing power draw.  156  6.0 CONCLUSIONS AND RECOMMENDATIONS  Based upon the results of four experiments, using a 2 stage pilot scale Autothermal Thermophilic Aerobic Digestion (ATAD) system fed with a combination of thickened primary and waste Bio-P secondary sludge at four different air supply rates, the following conclusions are presented. 6.1 Conclusions 1. When a phosphorus rich thickened waste activated sludgefroma biological nutrient removal sewage treatment plant was digested with thickened primary sludge in an ATAD, most of the stored phosphorus was released to solution. Less stored phosphorus was released when conditions alternated between anoxic/aerobic in ATAD 1 during the feeding cycle. Phosphorus released was 46 percent, as opposed to 79 percent released during the oxygen deprived experiment. 2. ATAD supernatant was highest in nitrogenfroma digester operating in the oxygen deprived condition. Lower dissolved nitrogen conditions resultedfromthe oxygen satisfied and oxygen excess conditions. The ATAD units operated under oxygen excess conditions produced nitrates. 3. The ATAD units operated under oxygen deprived conditions reduced the same amount of total volatile solids as the ATAD units operated under oxygen excess conditions. VS reduction closely matched that predicted by the Koers-Mavinic curve for thefirstATAD in series, but was significantly lower for the second ATAD, possibly because of low solids loading. 4. The ATAD units operated in oxygen deprived conditions exhibited the same COD reduction as ATADs operated in oxygen excess conditions. 5. The ATAD units operated in oxygen deprived conditions produced higher concentrations of dissolved volatile solids, dissolved COD and VFA in the supernatant than the ATAD units operated in oxygen satisfied or oxygen excess conditions, even though total VS reduction was the same (Conclusion 3). This suggests that solubilization rates were accelerated in 157  the ATAD units operating under oxygen deprived conditions, but that the rate of oxidation of dissolved substrate under oxygen deprived conditions was the same as under oxygen excess conditions. 6. Continuous Oxidation-Reduction Potential and Dissolved Oxygen monitoring proved to be a good indicator of the aeration state of an ATAD digester.  6.2 Recommendations  6.2.1 Applications The conclusions of this research project suggest that high aeration rates are not necessary to obtain a stabilized sludge from an ATAD reactor. In fact, better sludge solubilization occurs under oxygen deprived conditions. However, the quality of ATAD supernatant decreases when the digester is operated under oxygen deprived conditions, improved supernatant quality was realized under oxygen satisfied conditions, which were well defined by the shape of the combined ORP and DO traces. Unfortunately, a solids mass balance was not obtained for that condition so the effect of oxygen satisfied conditions on sludge stabilization is not yet clearly understood. However, since the oxygen satisfied condition is a combination of the oxygen excess and oxygen deprived conditions, it seems likely that the oxygen satisfied condition will prove to be as efficient as the other two conditions in terms of sludge stabilization. If sludge stabilization under oxygen satisfied conditions is the same as under aerobic and oxygen deprived conditions, then this mode of operation should produce the best quality supernatant with the least amount of air input. The air input for the oxygen satisfied condition is not very much greater than for the oxygen deprived condition. However, continuous ORP monitoring at least, and probably continuous DO momtoring as well, would be required to maintain this condition. Also necessary would be tight control on digester loacling, and such control may not be practical in a full scale application. ATADs have been proposed as a VFA source for enhancement of biological phosphorus removal. Operation under oxygen deprived conditions would produce high VFA concentrations, but if Bio-P sludge was stabilized using ATAD, the phosphorus loading to the plant would also . 1 5 8  increase. Operation under oxygen satisfied conditions would help lower nutrient concentrations in the supernatant, but the chemical treatment of the supernatant would probably still be required before recycling it to the head end of the plant. The use of ATAD in industrial wastewater treatment plants (for example, pulp mills), might reduce the cost of nutrient due to nutrient recycle. A cost-benefit analysis would be required to determine if such an application would be economical, since many pulp mills simply incinerate waste sludge. 6.2.2 Further Research Required 1. A solids mass balance should be done around a pilot scale ATAD operating under oxygen satisfied conditions to confirm that those conditions are just as efficient as oxygen excess conditions for VS and COD reduction. 2. Further work on the use of on-line oxygen monitoring in ATADs in conjunction with ORP monitoring should be carried out. This would include a more comprehensive review of existing probe models, and testing under laboratory conditions with high C0 atmosphere 2  conditions and elevated temperatures. Probe linearity under elevated temperature conditions should also be checked. Also required would be the installation of DO and ORP probes in several full scale operating ATADs of different design, to determine the normal aerobic state of full scale ATADs. 3. Sampling for all forms of nitrogen, including those in the off-gas, should be undertaken atfrequentintervals throughout an ATAD feed cycle. This procedure might help to determine the causes of the sudden slope changes observed in the ORP curve under oxygen satisfied conditions. 4. Sampling for all compounds which could affect pH and alkalinity should be undertaken atfrequentintervals throughout an ATAD feed cycle, in order to better explain the observed pH and alkalinity patterns in ATADs under varying airflow rates.  159  BIBLIOGRAPHY ABR Consultants Ltd. Predesign Report for Annacis Island and Lulu Island Wastewater Treatment Plants. Greater Vancouver Regional District, March, 1992. APHA Standard Methods for the Examination of Water and Wastewater. 17th ed. Washington DC. : American Public Health Organization, 1989. ASCE. A Standard for the Measurement of Oxygen Transfer in Clean Water. New York, July, 1984. Alhberg, N. and Boyko, B. "Evaluation and Design of Aerobic Digesters." Journal of the Water Pollution Control Federation 44, (April 1972): 634-643. Anderson, B. "Improvements in the Aerobic Digestion of Waste Activated Sludge Through Chemical Control of Mixed Liquor pH: Pilot-Scale investigations." Ph.D. Thesis, University of British Columbia, 1989. Anderson, B. and Mavinic, D. "Behavior and Control of Nutrients in the Enhanced Aerobic Digestion Process: Pilot-Scale Studies." Environmental Technology 14, (1993a) : 301318. Anderson, B. and Mavinic, D. "Behaviour of Volatile and Nonvolatile Suspended Solids in the Pilot-scale Aerobic Digestion of Waste-activated Sludges." Canadian Journal of Civil Engineering 20, No. 1, (1993b): 22-36. Arun, V. and Lohani, A. "Estimating Supernatant RecyclefromSludge Treatment." Journal of Environmental Engmeering 114, No. 2, (April 1988): 447-453. Baker, D.; Loehr, R.; and Anthonisen, A. "Oxygen Transfer at High Solids Concentrations." Journal of the Environmental Engineering Division. Proceedings of the American Society of Civil Engineers 101, No. EE5, (October 1975):759-774. Barnard,! "The Bardenpho Process." In Advances in Water and Wastewater Treatment: Biological Nutrient Removal pp. 79-113. Edited by M. Wanielista and W. Eckenfelder. Michigan: Ann Arbor Science, 1978. Bidlingmaier, W. "The Treatment of Sewage Sludge under Aerobic-Thermophile Conditions." In Inactivation of Microorganisms in Sewage Sludge by Stabilization Processes, pp. 206222. Edited by D. Strach; A. Havellar; and P. L'Herarite. London: Commission of European Communities, Elsevier Applied Science, 1984. Bishop P. and Farmer M. "Fate of Nutrients rJuring Aerobic Digestion." Journal Environmental Engineering Division. Proc. ASCE. 104, (1978): 967-979.  160  Bomio, M.; Sonnleitner, B.; and Fiechter, A. "Growth and Biocatalytic Activities of Aerobic Thermophilic Populations in Sewage Sludge." Applied Microbiology and Biotechnology 32, No. 3, (December 1989): 356-362. Booth, M.G. and Tramontini, E. "Thermophilic Sludge Digestion Using Oxygen and Air." In Sewage Sludge Stabilization and Disinfection, pp. 293- 311. Chichester, England: Ellis Harwood Ltd., 1983. Breitenbucher, K "Engineering and Practical Experiences of Autoheated Aerobic-Thermophilic Digestion." In Inactivation of Microorganisms in Sewage Sludge by Stabilization Processes, pp. 192-205. Edited by D. Strach; A.H. .Havellar; and P. L'Hermite. London: Commission of European Conmiunities, Elsevier Apphed Science, 1984. Bruce, A.M. "Other Investigations of Thermophilic Aerobic Digestion in the UK - Fundamental Aspects of Aerobic Thermophilic Biodegradation." In Treatment of Sewage: Thermophilic Aerobic Digestion and Processing Requirements for Land Filling, pp. 39-43. Edited by A. Bruce, F. Colin and P. Newman. London: Elsevier Apphed Science, 1987. Bruce, A. and Oliver, B. "Heating and Cooling of Sewage Sludges - Some Recent Developments." Journal of the Water Pollution Control Federation 58. (April 1986): 104115. Burnett, C. "Technology and Process Options for Autothermal Thermophilic Aerobic Digestion." In Proceedings of the Water Environment Federation 67th Annual Conference, pp. 655666. Chicago, Illinois: 1994. Casey, T. "Summary and Conclusions Following Bruce". In Treatment of Sewage: Thermophilic Aerobic Digestion and Processing Requirements for Land Filling, pp. 48-50. Editied by A. Bruce, F. Colin and P. Newman. London: Elsevier Apphed Science, 1987. Carrington, E.; Pike, E. Auty, D.; and Morris, R, "Destruction of Faecal Bacteria, Enteroviruses and Ova of Parasites in Wastewater Sludge by Aerobic Thermophilic and Anearobic Mesophilic Digestion." Water Science and Technology 24, No. 2, (1991): 377-380. Chu, A; Mavinic, D.; Kelly, H.; Ramey, W. "Volatile Fatty Acid Production in Thermophilic Aerobic Digestion of Sludge." Water Research 28, No. 7 (1994): 1513-1522. Couillard, D.; S. Gariepy; and F.T. Tran. "Slaughterhouse Effluent Treatment by Thermophilic Aerobic Process." Water Resources 23, No. 5, (1989): 573-579. Deeny, K; Heidman, J.; and Smith, J. "Autothermal Thermophilic Aerobic Digestion in the Federal Republic of Germany." In Proceedings of the 40th Purdue Industrial Waste Conference, pp. 959-968. Indiana: 1985. Deeny, K; Hahn, H.; Leonhard, D.; and Heidman, J. "Autoheated Thermophilic Aerobic Digestion." Water Environment and Technology, October, 1991, pp. 65-72.  161  Eastman, J. and Ferguson, J. "Solubilization of Particulate Organic Carbon E>uring the Acid Phase of Anaerobic Digestion." Journal of the Water Pollution Control Federation 53, (March, 1981): 352-366. EPA. Environmental Regulations and Technology. Autothermal Thermophilic Aerobic Digestion of Municipal Wastewater Sludge. Washington, DC: Environmental Protection Agency, [1990]. EPA. Process Design Manual Sludge Treatment and Disposal. Cincinnati, Ohio: EPA, 1979. EPA. Process Design Manual for Nitrogen Control. Washington, D.C.: EPA Office of Technology Transfer, 1975. Elefsiniotis, P.; Manoharan, R.; and Mavinic, D. "The Effects of Sludge Recycle Ratio on Nitrification-Denitrification Performance in Biological Treatment of Leachate." Environmental Technology Letters 10, (1989): 1041-1050. Feichter, A. and Sonnleitner, B. "Thermophilic Aerobic Stabilization." In Sewage Sludge Treatment and Use. New Developments. Technological Aspects and Environmental Effects, pp. 291-301. Edited by A. Dirkwager and P. L'Hermite. London: Commission of European Communities, Elsevier Applied Science, 1988. Florentz, M.; Hascoet, M.C.; and Bourdon, F. "Biological Phosphorous Removal at an Experimental Full-scale Plant in France." Canadian Journal of Civil Engineering 14 (1987): 278-283. Fuggle, Kand Spensley, R. "New Developments in Sludge Digestion and Pasteurization." Journal of Water Pollution Control 84 (1985): 33-43. Grulois, P.; Bousseau, A.; Blin, E.; and Fayoux, C. "Evaluation of the Impact of Return Flows on the Operation of a Wastewater Treatment Plant." Water Science and Technology 28, No. 1 (1993): 273-281. Hamer, G. "Fundamental Aspects of Aerobic Thermophilic Biodegredation." In Treatment of Sewage: Thermophilic Aerobic Digestion and Processing Requirements for Land Filling. pp. 2-19. Edited by A. Bruce, F. Colin and P. Newman. London: Elsevier Applied Science, 1987. Hamer, G; Bryers, J. "Aerobic Thermophilic Sludge Treatment, Some Biotechnological Concepts." Conservation and Recycling 8, Nos. 1/2 (1985): 267-284. Hamer, G and Zwiefelhofer, HP. "Aerobic Thermophilic Hygienization - A Supplement to Anearobic Mesophilic Waste Sludge Digestion." I. Chem. E. Syinposium Series No. 96, (January, 1985) : 163-180. Haug, R. The Practical Handbook of Compost Engineering. Michigan: Lewis Publishers, 1993.  162  Jakob, J.; Roos, H.; and Siekmann, K "Aerobic Thermophilic Methods for Disinfecting and Stabilizing Sewage Sludge." In Sewage Sludge Treatment and Use. New Developments. Technological Aspects and Environmental Effects, pp. 378-389. Edited by A. Dirkwager and P. L'Hermite. London: Commission of European Communities, Elsevier Apphed Science, 1989. Jardin, N., and PopeL H. "Behaviour of Excess Sludge From Enhanced Biological Phosphorus Removal Inuring Sludge Treatment" In Proceedings of the Water Environment Federation 67th Annual Conference, pp. 453-464. Chicago, Illinois: 1994. Jenkins, C. and Mavinic, D. "Anoxic-Aerobic Digestion of Waste Activated Sludge: Part U Supernatant Characteristics, ORP Monitoring Results and Overall Rating System" Environmental Technology Letters 10, No. 4 (April 1989): 371-384. JewelL W. and Kabrick, R. "Autoheated Aerobic Thennophilic Digestion with Aeration." Journal of the Water Pollution Control Federation 52, No. 3 (March 1980): 512-523. Kabrick, R, and JewelL W. "Fate of Pathogens in Thermophihc Aerobic Sludge Digestion." Water Research 16 (1982): 1051-1060. Kambhu, K and Andrews, John F. "Aerobic Thermophihc Process for the biological Treatment of Wastes - Simulation Studies." Journal of the Water Pollution Control Federation 41 (May 1969): R127-R141. Kelly, FL; Melcer, FL; and Mavinic, D. "Autothermal Thennophihc Aerobic Digestion of Municipal Sludges, a One Year Full Scale Demonstration Project." Water Environment Research Journal 65, No. 7 (Nov. 1993): 849-861. Kelly, Harlan G. "Demonstration of an Improved Digestion Process for Municipal Sludges." Vancouver, British Columbia: Dayton & Knight Ltd. Consulting Engineers, 1990. Kelly, H., Mavinic, D., Koch, F., Wetter, R., Melcer, H. "Liquid Composting of Municipal Sludge for Agricultural Use in Small Coinmunities: Canadian Application." In Proceedings IAWPRC, Sludge Management Conference. Los Angeles, California: 1990. Kelly, Harlan G. "Autothermal Thermophihc Aerobic Digestion: A Two Year Appraisal of Canadian Facilities." In Proceedings of ASCE Environmental Engineering Specialty Conference, pp. 296-301. Reno, Nevada: 1991. Knezevic, Z. "Enhanced Anaerobic Digestion of Combined Wastewater Sludges through Solubilization of Waste Activated Sludge." M. A. Sc. Thesis, University of British Columbia, 1993. Koch, F.; Oldham, W.; Wang, H "ORP as a Tool for Monitoring and Control in Bio-Nutrient Removal Systems." In Proceedings of the 1988 Joint CSCE-ASCE National Conference on Environmental Engineering, pp. 162-170. Vancouver, B.C.: 1988. 163  Koers, D. and Mavinic, D. "Aerobic Digestion of Waste Activated Sludge at Low Temperatures." Water Pollution Control Federation 49 (March 1977): 460-468. Langeland, G. and Paulsrud, B. "Aerobic Thermophilic Stabilization." In Inactivation of Microorganisms in Sewage Sludge by Stabilization Processes, pp. 38-47. Edited by D. Strach; A. Havellar; and P. L'Hermite. London: Commission of European Communities, Elsevier Applied Science, 1984. Lawler, D. and Singer, P. "Return flows from sludge treatment." Journal of the Water Pollution Control Federation 56 (February, 1984): 118-126. Ledbetter, J. Air Pollution Part A - Analysis. New York: Marcel Dekker Inc., 1972. Levin, G. and Shapiro, J. "Metabolic Uptake of Phosphorus by Wastewater Organisms." Journal of the Water Pollution Control Federation 37, No. 6 (1965): 800-821. Loll, U. "State of the Art with Regard to the Aerobic- TJiemophihc Stabilization of Sewage Sludge." In Treatment of Sewage: Thermophilic Aerobic Digestion and Processing Requirements for Landfilling. pp. 20-28. Edited by A. Bruce, F. Cohn and P. Newman. London: Elsevier Applied Science, 1987. LolL U. "Combined Aerobic, Thermophihc and Anearobic Digestion of Sewage Sludge." Abwasser-Abfah-Aquatechnik. (1984): 20-27. LolL U; Pawletta, G; and Reinert, D. "The influence of Heavy Metals on Aerobic-mermophilic Sewage Sludge Stabilization." In Recycling international II. pp. 980-989. Edited by K TJaome-Khozmiensky. Berlin: EF-Verlag, Fur Energie und Umwelttechnik GmbH, 1986. Matsch, L. and Drnevich, R. "Autothermal Aerobic Digestion." Journal of the Water Pollution Control Federation 49 (February 1977): 296-310. Matsch, L.C. and Drnevich, R.F. "Phostrip: A Biological-Chemical System for Removing Phosphorus." In Advances in Water and Wastewater Treatment: Biological Nutrient Removal pp 115-142. Edited by M. Wanielista and W. Eckenfelder. Michigan: Ann Arbor Science, 1978. Mason, C; Hamer, G; neischmann T.; and Lang, C. "Aerobic Thermophilic Biodegradation of Microbial Cells." Applied Microbiology and Biotechnology 25 (1987a): 568-576. Mason, C; Hamer, G; Heischmann, T.; and Lang, C. "Bioparticulate Solubilization and Biodegradation in Semi-Continuous Aerobic Theromophilic Digestion" Water. Air and Soil Pollution 34, (1987b): 399-407. Mavinic, D.S. and B.C. Anderson. "Comparison of Aerobic and Anaerobic Process in the Digestion of Mixed SludgesfromBiological Phosphorous Removal Treatment Plants." University of British Columbia: Strategic Grant No. 0032768, 1990.  164  Messenger, J. "The Stoichiometry and Kinetics of Biological Heat Generation in the Aerobic Stage of Dual Digestion." Ph. D. Thesis, University of Cape Town, 1991. Metcalf & Eddy, Inc. Wastewater Engineering: Treatment/Disposal/Reuse. USA: McGraw-Hill, 1991 Morgan, S. and Gunson, H. "The Development of an Aerobic Thermophihc Sludge Digestion System in the U.K" In Treatment of Sewage: Thermophihc Aerobic Digestion and Processing Requirements for Land Filling, pp. 29-37. Edited by A. Bruce, F. Colin and P.J. Newman. London: Elsevier Apphed Science, 1987. Morgan, S.F.; Gunson, H.G.; Littelwood, M.H.; and Winstanley, R. "Aerobic Thermophihc Digestion of Sludge Using Air." In Sewage Sludge Stabilization and Disinfection, pp. 278-292. Chichester, England: Ellis Horwood Ltd., 1983. Morgan, S.; Winstanley, R.; Littelwood, M.; and Gunson, H. "The Design of an Aerobic Thermophihc Sludge Digestion System" Institute Chemical Engineering Symposium Series 96 (1986): 393-402. Murray, K; Tong, A.; and Bruce, A. "Thermophihc Aerobic Digestion - A Reliable and Effective Process for Sludge Treatment at Small Works." Water Science and Technology. 22, No. 3/4 (1990): 225-232. Neodbala, D. University of British Columbia. Interview, December 21, 1993. Newbigging, M.; Nolasco, D.; DeAngelis, B.; Dobson, B. "Impact of Solids Handling Recycle Streams on the Liquid Train of the Metropolitan Toronto Main Treatment Plant." In Proceedings of the Water Environment Federation 67th Annual Conference, pp. 441-452. Chicago, Illinois: 1994. Norris, J.R. and Ribbons, D.W. Methods in Microbiology. London: Academic Press, 1971. Peddie, C C ; Koch, F.A.; Jenkins, C.J.; and Mavinic, D.S. "ORP as a Tool for Monitoring and Control of SBR Systems for Aerobic Sludge Digestion." In Proceedings of the Joint CSCE-ASCE National Conference on Environmental Engineering, pp. 171-178. Vancouver, BC: 1988. Peddie, C C and Mavinic, D.S. "Prelirninary Results of a Pilot Scale Evaluation of Aerobic/Anoxic Sludge Digestion." In Proceedings of the 1988 CSCE Annual Conference, pp. 461-479. Calgary, Alberta: 1988. Popel F. and Ohnmacht, C. "Thermophihc Bacterial Oxidation of Highly Concentrated Substrates." Water Research 6. (1972): 807-815. Popel H and Jardin, N. "Influence of Enhanced Biological Phosphorus Removal on Sludge Treatment." Water Science Technology 28, No.l (1993): 263-271.  165  Rabinowitz, B. "The Role of Specific Substrates in Excess Biological Phosphorus Removal." PhD. Thesis, University of British Columbia, 1985. Randall, C; Marshall, D.; and King, P. "Phosphate Release in Activated Sludge Process." Journal of the Sanitary Engineering Division. Proceedings of the American Society of Civil Engineers 96, No. SA2 (April, 1970):395-408. Randall, C. "Biological Nutrient Removal Applications" Biological Nutrient Removal Seminar. Calgary: Reid Crowther and Partners, 1990. Randall, C; Waltrip, D.; and Wable, M. "Upgrading a Municipal Activated Sludge Plant for High-Rate Biological Nutrient Removal." In IAWPRC/EWPCA Specialized Conference on Upgrading of Wastewater Treatment Plants. Munich: 1989. Reid Crowther and Partners Ltd. "Autoheated Thermophilic Aerobic Digestion of Wastewater Sludges". Calgary, Alberta: Reid Crowther and Partners Ltd., 1987 Reid Crowther and Partners Ltd. "Banff Wastewater Treatment Plant Audit", Calgary, Alberta: Reid Crotwher and Partners Ltd., 1994. Schuster, M. Manager, Banff Wastewater Treatment Plant. Interview, September 15, 1991. Schuster, M. Manager, Banff Wastewater Treatment Plant. Interview, December 12, 1994. Schon, G.; Geywitz, S; and Mertens, F. "Influence of Dissolved Oxygen and OxidationReduction Potential on Phosphate Release and Uptake by Activated Sludge from Sewage plants with Enhanced Biological Phosphorus Removal." Water Research 27,(1993): 349-354. Schwinning, H.; Fuchs, L.; and Deeny, K "ATAD - An Effective PFRP Alternative." In Proceedings of the Water Environment Federation 66th Annual Conference and Exposition. Vol. 4, Sludge Management, pp. 37-48. Anaheim, California: 1993. Smith, J.; Young, K; and Dean, R. "Biological Oxidation and Disinfection of Sludge." Water Research 9, (1975): 17-24. Sonnleitner, B. "Biotechnology of Ihermophihc Bacteria - Growth, Products and Application." In Advances in Biochemical Engmeering/Biotechnology pp 68-138. Ed. by A. Fiechter. New York: Springer-Verlag, 1983. Sonnleitner, B. and Feichter, A. "Bacterial Diversity in Thermophilic Aerobic Sewage Sludge. 1. Active biomass and its Fluctuations." European Journal of Applied Microbiology and Biotechnology 18, (1983a): 47-51. Sonnleitner, B. and Feichter, A. "Bacterial Diversity in Ihermophihc Aerobic Sewage Sludge II. Types of Organisms and their Capacities." European Journal of Applied Microbiology and Biotechnology 18, (1983b): 174-180. 166  Sonnleitner, B. and Feichter, A. "Thermophilic Microflora in Aerated Sewage Sludge". In Processing and Use of Sewage Sludge. Proceedings of the Third International Symposium pp. 235-236. Edited by P. L'Hermite, and H Ott. Brighton: 1983c. Sonnleitner, B. and Feichter, A. "Microbial Flora Studies m Thermophilic Aerobic Sludge Treatment." Conservation and Recycling 8, No. 1/2 (1985): 303-313. Strauch, D; HammeL H.; and Philipp, W. "Investigations on the Hygienic Effect of Single Stage and Two-Stage Aerobic-Thermophihc Stabilization of Liquid Raw Sludge". In Inactivation of Microorganisms in Sewage Sludge by Stabilization Processes, pp. 48-63. Edited by D. Strauch; A. Havellar; and P. L'Hermite. London: Commission of European Cornmunities, Elsevier Apphed Science, 1984. Stevens, G.M. "Biological Phosphorus and Nitrogen Removal: The Kelowna Experience". Calgary: Reid Crowther and Partners, 1990. Surucu, G.; Chain, E.: and Engelbrecht, R. "Aerobic Thermophilic Treatment of High Strength Wastewaters." Journal of the Water Pollution Control Federation 48, No. 4 (April 1976): 669-679. Toerien, D.F.; Gerber, A; Lotter, L.H. and Cloete, T.E. "Enhanced Biological Phosphorous Removal in the Activated Sludge Systems." In Advances in Microbial Ecology. Vol TJ. pp 173-229. Edited by K.C. Marshall. New York : Plenum Press, 1990. Tortora, G.J.; Funke, B.R.; and Case, CL. Microbiology, an Introduction, 3rd. ed. Benjamin Cummings: Redwood City, 1992. Trim, B. and McGlashan, J. "Sludge Stabilization and Disinfection by Means of Autothermal Aerobic Digestion with Oxygen." Water Science Technology 17, (1984): 563-573. Tyagi, R.; Tran, F.; and Agebavi, T. "Mesophilic and Thermophihc Aerobic Digestion of Municipal Sludge in an Airlift U-shape Bioreactor." Biological Waste 31 (1990): 251256. Vik, T. and Kirk, J. "Evaluation of the Cost Effectiveness of the Auto Thermal Aerobic Digestion Process for a Medium Sized Wastewater Treatment Facility." Proceedings of the Water Environment Federation 66th Annual Conference and Exposition. Sludge Management, Vol. 4. pp. 65-78. Anaheim, California: 1993. Vismara, R. "A Model for Autothermic Aerobic Digestion, Effects of Scale depending on Aeration Efficiency and Sludge Concentration." Water Resources 19, No. 4 (1985): 441447. Wareham, D.; HalL K; Mavinic, D. "Real-Time control of Aerobic-Anoxic Sludge Digestion Using ORP." Journal of Environmental Engineering 119, No. 1 (January/February 1993): 120-136.  167  Wedi, D. and Konig, E. "Elimination of Nitrogen and Phosphorus From Sludge Liquor." Water Science Technology 28, No. 1 (1993): 283-287. Wells, W. "IMfferences in Phosphate Uptake Rates Exhibited by Activated Sludges." Journal of the Water Pollution Control Federation 41, No. 5, Part 1 (1969): 765-771. Workers Compensation Board of B.C. Laboratory Services. Laboratory Analytical Methods. British Columbia: WCB, 1989. WPCF Journal Literature Review. "Thermophilic Aerobic Digestion" Journal Water Pollution Control Federation 58, No. 6 (June 1986): 502-503. WPCF Disinfection Cornmittee. Sludge Disinfection, a Review of the Literature. Washington D.C. 1984. Wolf, P. "Aerobic Ihennophihc Stabilization of Sludge versus Anearobic Digestion and Other Kinds of Sludge Treatment at Middle-Sized Plants with Respect to Power Conservation and Economy." Water Science Technology 14 (1982): 727-738. Wolinski, W.K "Aerobic Thermophilic Sludge Stabilization Using Air." Journal of Water Pollution Control 84, (January 1985): 433-455. Zwielhofer, Hans P. "Aerobic-Thermophjhc/Anaerobic-Mesophihc Two-stage Sewage Sludge Treatment: Practical Experiences in Switzerland." Conservation and Recycling 8, No. 1/2 (1985): 285-301.  168  APPENDIX 1  DATA  169  5  o  o  o  o  o  o  o  o  o  o  o  o  o  O  O  O  O  O  O  O  O  O  O  O  O  O  i n i n i n « n i n > n i n i n i n i n m i n m  a a a a o\ o\ afta o\ a a o\ V O V O V O V O V O V O V O V O V O V O V O V O V O  O H  o o o r- cs m p-' r»" vo" vd T t ' ro'  o > no o o o N  ri  ro  T t  T t  T3  i n > n m > n i n i n m m . i n i n i n i n i n  b bbbbbbbbbbb b in  5  rt-' CS  O  O  CN CN  CN CS  o o t i  00 CN  CO CN CN  O T t  CN  o r-' CN  CO  m  m  b  CO CN  ro' CN  CN  o o o o o cs co CO CO co ro  CO CO  b b  b b  ©  ©  ©  CN  b b  vq CO  o  T t  CO CN  cs cs  in r-CN ©  CO  (N  CN  o co o m o in in n ro T t o > CO CO to cs CO co ro ro ro co CO CO  b b  O >  CO  O in  ro' cs  1  IOQ  ©  b  ©  b  ©  ©  © CO  b  O o >n o  m  CN  CN CS  T t  CS  T t  CN  O  O  in  T t  © in CS  cs  in  CN  in  CN  o o o o in o © in © in r- in in in in T t T t T t CS CS cs CS CN cs  o © o o o o o o o o o m ft od od oo' oo' od oo' od oo' oo' oo' r-'  CO  o  ©" ©  in m in in in in in UO m m > n< n o o o o o o o o o o o o o  ll  IE  b  ©  cs  b b b  © ro  O © © © © m © © © © © in in i n r~- r~- r--' r-' r-' t--' r-' r-^ r--' o'  rororororororococococoroco ftftftftftftftftftftftftft H  H  H  H  RT  RT  H  170  H  H  N  N  N  N  H CQ  5/5  5 < <  in S  o\  Vi h  in a  © oo  in oo  o oo  © i n i n i n o © i n © © i f i H o o o o a a t ^ w a  H . N  u  o oo  0 a  © oo  m io  u~> io  © i n © f t n f t  n n ( N N N ( N t N ( N t N n N  in  ©  (N  (N H  in  m  m  in  in  ir>  in  ©  ©  ©'  ©'  ©'. ©  H  O w i V i p O O O ' O O >-H fN cri iri mi T J - ' VO' iri vo'  4 >  CO  in  m  in  io  in  in  <n  ©'  o  ©  o"  ©  o  m ©'  C/3  •n cn O «n m © cn © in op •n © © cn •*' Tf' cn •*' •*' CN cn cn CN «*' rn cn CN CN CN CN CN CN CN cN CN CN CN CN © o cn m ©' o  II.  II t/i  i—i rn cn CN CN © i — i i—i © i — i m cn m cn m m m cn m m cn o © ©' © ©' ©' © © ©' ©' ©'  t/5  •n in m in © •n 00 •n © cn cn m m cn m rn ©' o o © ©' © o o o  00 in vo vo cn cn cn cn © ©' •©" ©'  o > <L)  •n •n in in in in •n •n >n •n in •n in o o o o © © © © © © © © ©  60 5/3  •n CN in CN  IQ §  . 12.^a .  © in •n CN  © o © © in in CN CN  in cN in CN  •n CN CN CN  m CN •*' CN  © m © © © CN •n © , in in CN CN CN CN  .© © © © © © 00 © © © © © © rn cn cn cn cn rn CN m" rn m' cn rn rn  CO  is  •n © CN in in Tf' CN CN  2"  © o o © © © © © © © © © © CN CN CN CN CN CN CN CN CN CN CN CN CN c  Os CN  n  m  m  Os Oscn  m  m  in  vo  m  m  m  m  c  n  c  n  m  m  O s O s O s O s O s O s O s O s O s O s oo  ;  H  N  M  S J C i ^ Q ^ J J J J p i ^ n CN CN CN CN CN CN CN  171  ^ rn  io  «  c n > n  <<  3  CN cn  in m  m  o  m  i—i  r-- r-  I f IS w  6 0  00  00  00  T t  T t  T t  o m CO SO VO rm  o  00  00  <o  o  o  co'  CN  «/->  IT)  in  in  in  o  o  o  o  o .o  m  o  in m  in m  in in in in CN 0 0 0 0 rT t CO CO i n  T t  T t  — iI  in  o  T t  oT f  m m o m m CN CN* CN CN CN CN 00  O T t  in m  o  00  vo  T t  m to  00  I  in  m  m  in  m  o  o  o  o  o  o  co T f  o o o CO CO CO cs © ©  b  i-H  00  CO cs  o o m o CO CO CS ro  b b b b b b b  in in in o CO CO CO CO T t ©' Ov  in CO cs o o CN CO CO CO ro © ©  b b b b b  H  r-1  4)  in  o 0 0 i n CO 0 0 © o CO r o m i n CN T t T t T t co' T t T t T t T f CN CN CN CN CN CN CN CN CN CN CN CN 00  3 o >  in  in o  m o  in o  in o  o © in CN  in m in t CN rin T t m cs CS CS  b  b  CS i - H CO co ©  b  o T t CO ro ©  b  m o  m o  m o  in .©  m o  m o  m  in rm CS  in cs  in  o in  m r-  in r-  cs  o o ro' cs  vd  O  in o  o © ro' T t T t T t in CN CS CN CS CN  o o CO co  o o CO ro  o co  o co  o ro  O  ro  O o © CO CO ro  © CO  o o CN cs  o cs  o cs  o cs  o cs  o cs  o cs  © CN  &  w u  o cs  O o CN cs  CO  c o c o c o c o c o r o r o r o r o r o r o r o Ov Os Os O v O v O v O v O v O v O v Os Os i n vo r~ oo os © CN r o T t m vo  I to  ts  T t  T t  T t  T t  T f  "~'  T t  T t  111  T t  T t  T f  T t  T t  .a  < <  3 <<  5  o  o  >/-i ro  VO ro  o  © vo ro  so ro  vo ro  SO ro  vo ro  if  o  o  CO Os  O  o  o  CN  Os  Os  ro  5  1>  o  o o  CN  3  o  SO  o o  00  00  Ov ro SO  CN VO  VO  CN  •*'  VO  SO  5!  o  Os  >2  Os  CN  to  ro •*'  CO  m TT O  in  CN  vi O  " H CN  oo I-I CN  £ CN  $  Os N  CN <>» N <N  o o o O T t i n s o i - t M s o n s O o o cN CN co co' r o ro' ro' ro' co co' CN CN  (/I  c o c o c o r o r o r o r o r o r o c o c o c o  §  O s O s O s O s O s O s O s O v O s O s O s O s m vo r - oo Os o C N co i t m so  ^  •<? ^ t  ^  ^t  ^  173  ^?  ^  UO OS  00  IO i-H  uo  I t rO  O  o  60 cu  cu  u-i ON  UO Tf  uo  u-i  uo  1 -H Ul  00  i-H  Tf  0\  Tf  uo OS  Ocs Os  UO Tf Os  u-i  Ul  00  i-H  Ul Tf  U"l © o wi U~i T f  i-H U0 Tf  UO Tt Os  Ul Tf Os  o  ON  U~l Tf Os  u-i o  o  o  o  o  o  u-i  r~  i-H  UO Tf Os  i-H  UO Tf  rH Tf  I-H  Tf  I-H  rTt  I-H  Tf  SO  ON  i-H  rTf  Tf  Tt  o  IT)  u-i  UO  O  Tf  Tf  uo'  SO  f-'  u-> 00 O oo' r-' f - '  H cu  5  I CQ  .a <*> ca -—-  3  .a  ffi  w  u-> b b  u-> uo b b  UO  Ul  Ul  UO  UO  UO  UO  UO  b  b  b  b  b  b  b  b  o  o  o  o  Ul  00  00  ©  Tf  Tf  cs  cs  co' co' T f cs cs CS  Tf  cs  so'  © UO co' CO cs cs  o  CN  CO CN  © co'  t-~  o  00  00  cs b  cs b  rcs b  rcs b  Os  CN  CO CO  O  o  b  b  b  b  U0  UO  o  r-- o cs CO b b  cs  CN  CN  cs b  CO  b  rcs b  cs b  cs ©  cs b  UO  Ul  o  o  cs b  r-- o cs CO b b  o b  cs b  uo o  uo O  Ul  u-i o  u-> u-i uo o O O  uo  O o cs  o o o Ul so T t cs CS  o  o  b  o  o  o  CO  CO  CO  CO  CO  CO  o cs  o cs  o cs  o cs  o cs  o cs  Ul  CO  CO  b  CO  CO  o  CO  b  cu cu  CQ  o  uo o  UO  U0  o  o  o Ul © cs uo' T f CN cs  u-> cs  Ul  Tf  Tt  o o co CO  O  o  o  O  CO  CO  CO  CO  o cs  o  o cs  o  o  CN  CN  CZ3  I«N  05  CS  ll  u-i CS  «3  cu  iff cn O o  s 60  Tf  o o u-i o  UO  cs Tf  Tf  Tf  U0  CN  CS  r~  Tf  cs  CS  o cs  CN  cs  CN  c o c o c o c o c o c o c o c o c o c o r o r o ONOSOSONONOSONONONONOSOS  ifi  •a a. cu  II co  rcs b  O >  I!  Tt UO  ir> so U~>  UO  oo os o Ul  Tl  IT) Ul  174  CN  CO  Tt  UO  U">  UO  UO  UO  ' UO  _4> Ct> CQ  5  cu  rJ  o  VO cn  8  vo cn  m cn  o SO  >n  o  Os i—i  cn o  Os  00 60  *o  SO  VO  CN  Os CN so  o VO  3  o  VO  o  Os  Os  Os  r-1 CO  Os cn  vo CN O  o  cn Pi  00 VO  00 SO  CN VO  cn  CN VO  cn  in  cn  ll  1 vo  TT  CN  iff UI <U O  I-  g 60  o  VO so cn cn  cn  cn  d  o  cn  o  %  in <n  ^3  <n  vo ^  ^  in  . ^  m  CN  <n  m  3  in  VO I-I  O s O O i - H O ' — I ^ O V O O S T J - O O O V Tt  Tf' i n  in  in  in  in  T}-'  Tf  rf  Tf  c n c n m c n c n c n c n c n c n c n c n c n O v O s O s O s O s O s O s O s O s O s O s O s r t m vo r~- oo ov o CN cn in in  in  in  in  in  in  in  in  in  in  m  m  ^  CN  ii  55 II  II  3 3  175  APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Excess Experiment No. 1 Bio-P Sludge Primary Sludge Date Vol. TS VS Vol. TS (L/d) (mg/L) (mg/L) (L/d) (mg/L) 12.0 24327 1/6/93 12.5 20842 18963 11.0 22493 1/11/93 13.0 16251 14947 9.0 22599 1/12/93 15.0 18177 16678 8.0 23997 1/13/93 15.0 17376 15800 8.0 23544 1/14/93 17.0 18001 16497 8.0 22906 1/15/93 17.0 17931 16518 8.0 22975 1/16/93 17.0 20436 18698 8.0 21571 1/17/93 17.5 20739 18918 8.0 21939 1/18/93 17.0 17884 16218 16221 14749 8.0 23033 1/19/93 17.0 8.0 23276 1/20/93 17.0 20100 18250 8.0 23810 1/21/93 17.0 19914 16812 8.0 22436 1/22/93 17.0 20214 16089 7.5 24177 1/23/93 17.5 21702 17292 8.3 22882 Average 16.4 18604 16681 Jan 11-Jan 22/93  VS (mg/L) 19079 18144 18506 19510 19016 18546 18323 17270 17904 18807 18937 19194 17557 18989 18476  ATAD 1 Sludge ATAD 2 Sludge VS Vol. TS VS Vol. TS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 12107 1/6/93 22.5 18048 14786 26.5 15087 1/11/93 23.7 16652 13841 24.6 16072 12928 12643 1/12/93 24.7 17122 14264 22.2 15479 12738 1/13/93 22.2 16517 13891 22.2 15453 1/14/93 24.4 16736 14041 21.9 15462 12587 1/15/93 25.2 16400 13977 22.4 15232 12550 12676 1/16/93 24.7 16194 13885 24.2 15258 1/17/93 25.4 16747 14224 27.1 14904 12499 12900 1/18/93 25.2 17369 14837 20.5 15398 12865 1/19/93 25.7 16725 14250 23.7 15286 13094 1/20/93 25.2 16909 14494 23.6 15578 12932 1/21/93 24.7 17072 14680 23.7 15334 12829 1/22/93 25.0 17440 14534 24.5 15173 13898 1/23/93 25.0 18122 14813 23.5 16449 12770 Average 24.7 16824 14243 23.4 15386 Jan 11-Jan 22/93  Date  176  Mixed Influent Sludge VS Vol. TS (L/d) (mg/L) (mg/L) 24.5 22549 19020 24.0 19101 16403 24.0 19824 17354 23.0 19665 17078 25.0 19763 17293 25.0 19503 17150 25.0 21225 18558 25.5 20976 18380 25.0 19157 16736 25.0 18381 16030 25.0 21094 18451 25.0 21139 17557 25.0 20901 16540 25.0 22422 17783 24.7 20061 17294  APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Deprived Experiment Bio-P Sludge Primary Sludge Date VS Vol. TS Vol. TS (L/d) (mg/L) (mg/L) (L/d) (mg/L) 13.0 22272 2/22/93 12.0 21907 19390 13.0 21441 2/23/93 12.0 23426 20814 13.0 21504 2/24/93 12.0 24655 22085 13.0 22257 2/25/93 12.0 20457 18371 13.0 22846 2/26/93 12.0 18058 16196 13.0 22789 2/27/93 12.0 18961 17075 12.8 22763 2/28/93 12.0 19979 18025 13.0 24263 3/1/93 12.0 17408 15627 13.0 24277 3/2/93 12.0 20096 18026 13.0 24112 3/3/93 12.0 22763 20535 13.0 23574 3/4/93 12.0 22604 20007 13.0 23020 3/5/93 12.0 23341 20286 13.0 22033 3/6/93 12.0 23380 20210 Average 12.0 21261 18938 13.0 22907 Feb. 23-Mlar 6/93  VS (mg/L) 17268 16530 16576 17305 17720 17731 17978 18899 19350 19043 18646 18215 17260 17938  ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 13515 2/22/93 25.5 19534 15451 23.7 17514 12615 2/23/93 25.5 18327 14576 24.4 16523 13098 2/24/93 24.7 18798 15224 24! 1 16933 12638 2/25/93 25.7 19071 15567 23.6 16343 13142 2/26/93 25.2 18758 14984 24.4 17110 13311 2/27/93 25.2 18287 14839 24.1 16849 13081 2/28/93 25.5 18347 14780 24.4 16741 13050 3/1/93 22.5 18744 15192 23.1 16664 13123 3/2/93 24.5 17788 14438 23.6 16546 12979 3/3/93 25.2 18163 14770 22.9 16356 12777 3/4/93 24.5 18219 14848 23.6 16184 13336 3/5/93 24.7 18690 15208 23.1 16835 13534 3/6/93 25.3 18505 14909 24.1 17043 13057 Average 24.9 18475 14945 23.8 16677 Feb. 23-Mfar 6/93  Date  177  Mixed Influent Sludge Vol. TS VS (L/d) (mg/L) (mg/L) 25.0 22070 18264 25.0 22366 18563 25.0 22986 19195 25.0 21365 17794 25.0 20519 16965 25.0 20926 17395 24.8 21390 17981 25.0 20954 17312 25.0 22250 18697 25.0 23440 19739 25.0 23092 19285 25.0 23153 19191 25.0 22663 18662 25.0 22092 18398  APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Satisfied Experiment Date Primary Sludge Bio-P Sludge Vol. TS VS Vol. TS (L/d) (mg/L) (mg/L) (L/d) (mg/L) 13.0 29993 3/31/93 12.0 62853 30124 13.0 29522 4/5/93 12.0 29534 18641 13.0 29503 4/6/93 12.0 24022 16110 13.0 29944 4/7/93 12.0 16012 11978 13.0 29489 4/8/93 12.0 18281 13053 13.0 29534 4/9/93 12.0 15167 11258 13.0 30408 4/10/93 12.0 13826 11024 13.0 30730 4/11/93 12.0 13614 10407 13.0 29041 4/12/93 12.0 10367 8869 13.0 30162 4/13/93 12.0 11159 9337 13.0 30167 4/14/93 12.0 12711 10764 12.0 21970 17349 13.0 29707 4/15/93 13.0 28515 4/16/93 12.0 29020 22911 Average 12.0 17973 13475 13.0 29727 April 5 - 16 192 Date  VS (mg/L) 19283 19071 18850 19389 19140 19297 19933 20123 19071 19914 19926 19882 18680 19440  ATAD 1 Sludge ATAD 2 Sludge TS VS Vol. TS VS Vol. (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 15207 3/31/93 25.5 33788 16947 24.0 25690 16290 4/5/93 25.2 30805 17029 24.9 31262 16029 4/6/93 25.4 28639 16027 24.4 30769 15422 4/7/93 25.0 26736 15588 25.1 28927 14925 4/8/93 26.0 24318 14527 22.9 28033 14148 4/9/93 26.0 23124 14229 24.6 25820 13287 4/10/93 26.5 21632 13659 24.4 23309 12873 4/11/93 23.3 20606 13133 24.9 22426 12433 23.1 21454 4/12/93 24.0 20546 13115 12148 4/13/93 24.8 19440 12702 24.1 20319 11662 4/14/93 25.0 19253 12649 24.4 19435 11706 4/15/93 25.0 18569 12489 24.4 18668 11032 4/16/93 25.2 20036 13135 24.6 18423 13496 Average 25.1 22809 14024 24.3 24070 April 5 - 16 193  178  Mixed Influent Sludge VS Vol. TS (L/d) (mg/L) (mg/L) 25.0 45766 24487 25.0 29489 18840 25.0 26841 17515 25.0 23227 15811 25.0 24086 16202 25.0 22611 15420 25.0 22422 15638 25.0 22487 15441 25.0 20052 14156 25.0 21015 14819 25.0 21762 15509 25.0 25969 18649 25.0 28726 20689 25.0 24057 16558  APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Excess Experiment No. 2 Primary Sludge Bio-P Sludge Date VS Vol. TS Vol. TS (L/d) (mg/L) (mg/L) (L/d) (mg/L) 13.0 29102 5/3/93 12.0 17620 14986 13.0 29682 5/4/93 12.0 18891 15938 13.0 29255 5/5/93 12.0 17429 14669 5/6/93 12.0 20293 17046 13.0 26848 13.0 26934 5/7/93 12.0 16057 13456 13.0 26406 5/8/93 12.0 19135 16245 13.0 25308 5/9/93 12.0 19319 16433 13.0 25735 5/10/93 12.0 17296 14791 13.0 25327 5/11/93 12.0 19803 16910 13.0 24920 12.0 19174 16451 5/12/93 13.0 23800 5/13/93 12.0 20969 18024 13.0 23417 5/14/93 12.0 19126 16428 13.0 23401 5/15/93 12.0 20340 17285 13.0 25920 Averages 12.0 18986 16140 May 4-15/93 Date  VS (mg/L) 20757 21490 21138 18941 18997 18734 18062 18452 18093 17809 17031 16701 16618 18505  ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS TS VS Vol. (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 12436 5/3/93 24.7 19235 14061 24.4 17568 12089 5/4/93 25.5 19519 14115 22.2 17410 5/5/93 24.2 19445 14503 24.1 17262 12505 12467 5/6/93 26.2 19915 14572 24.2 17481 12379 5/7/93 24.7 19369 14351 26.1 17197 12455 5/8/93 24.5 19084 13850 23.6 17429 12337 5/9/93 24.7 19386 14291 23.9 17053 12759 5/10/93 24.2 19020 14087 24.9 17345 12446 5/11/93 24.9 18813 13714 23.1 17265 12241 5/12/93 25.2 18729 13901 23.6 16964 12224 5/13/93 24.4 19028 13813 24.1 16913 12323 5/14/93 24.4 18722 13700 23.1 17313 11751 5/15/93 24.9 17567 13079 23.1 16370 12331 Averages 24.8 19050 13998 23.8 17167 May 4-15/93  179  Mixed Mluent Sludge TS VS Vol. (L/d) (mg/L) (mg/L) 25.0 23567 17969 25.0 24477 18805 25.0 23559 18018 25.0 23680 18015 25.0 21691 16321 25.0 22893 17521 25.0 22412 17263 25.0 21667 16681 25.0 22661 17514 25.0 22150 17148 25.0 22435 17503 25.0 21349 16563 25.0 21920 16929 25.0 22575 17357  APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 1 Thickened Primary Sludge Date NOx TKN DTKN NIB (mg/L) (mg/L) (mg/L) ( mg/L) 12/30/92 33.0 0.18 1/6/93 700 30.0 25.0 0.23 1/11/93 497 34.0 0.10 28.8 1/12/93 598 37.4 49.5 0.21 1/13/93 543 0.20 29.6 21.3 1/14/93 532 26.3 0.49 1/15/93 510 28.2 31.5 33.2 0.48 1/16/93 591 0.18 632 28.9 38.2 1/17/93 0.18 33.0 23.6 1/18/93 561 21.1 0.48 1/19/93 503 29.9 26.3 17.6 0.41 1/20/93 611 22.6 26.5 0.18 1/21/93 593 22.1 23.8 0.16 1/22/93 592 22.6 21.4 0.16 1/23/93 643 Averages 563 29.0 28.3 0.28 Jan 11-Jan 22/93 Date  Mixed Influent Sludge NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) ( mg/L) 14.4 1/11/93 888 17.9 0.31 19.5 22.4 1/12/93 949 0.21 25.6 33.2 1/13/93 890 0.32 21.4 14.9 1/14/93 813 0.36 20.2 18.2 1/15/93 814 0.63 22.7 23.2 1/16/93 912 0.49 26.6 1/17/93 883 21.1 0.20 26.2 18.5 1/18/93 824 0.34 21.9 15.1 1/19/93 906 0.69 12.5 1/20/93 919 19.1 0.43 20.6 1/21/93 913 17.8 0.29 17.3 . 0.21 1/22/93 915 16.4 16.9 15.7 1/23/93 940 0.22 Averages 886 20.8 19.7 0.37 Jan 11-Jan 22/93 180  Thickened Bio-P Sludge NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) (mg/L) 7.5 1.56 0.28 1575 3.8 0.40 1352 3.8 1.9 3.1 0.39 1535 3.9 0.52 1543 3.7 2.6 4.2 1.3 0.69 1412 0.92 1464 3.5 1.1 0.53 1598 4.0 2.1 1.3 0.24 1436 3.9 11.7 7.6 0.66 1386 1.13 4.8 2.4 1766 0.48 1577 3.9 1.5 0.54 1596 7.8 8.1 3.6 0.31 1605 4.5 2.5 0.35 1637 3.7 1522 5.0 3.1 0.57  APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 1 ATAD 1 Sludge Date TKN Dl KN NH3 (mg/L) (mg/L) (mg/L) 1/6/93 1125 26.0 326.8 288.5 1/11/93 973 336.6 285.0 1/12/93 922 1/13/93 894 348.9 406.0 1/14/93 859 343.9 329.0 313.7 272.7 1/15/93 833 761 294.4 326.9 1/16/93 317.3 233.1 1/17/93 815 315.9 241.2 1/18/93 772 297.4 231.6 1/19/93 783 280.1 256.3 1/20/93 788 1/21/93 816 281.8 308.7 282.6 273.4 1/22/93 789 1/23/93 786 273.2 256.5 Averages 834 311.6 287.7 Jan 11-Jan 22/93  ATAD 2 TKN NOx (mg/L) (mg/L) 913 2.36 951 14.32 963 12.04 13.73 934 14.66 954 4.87 941 936 2.89 868 6.36 10.68 883 11.40 838 5.92 837 5.82 793 7.10 794 15.40 808 891 9.15  181  Sludge NOx DTKN NH3 (mg/L) (mg/L) (mg/L) 2.89 509.3 457.6 13.97 564.6 579.9 14.52 590.6 667.6 13.40 520.5 480.4 11.75 531.2 558.1 11.27 499.5 418.4 7.27 484.1 371.6 5.17 437.6 531.0 5.87 447.6 366.9 7.48 486.0 483.2 7.16 450.6 460.2 6.00 442.5 460.5 4.69 429.8 398.6 4.98 497.0 486.3 9.05  APPENDIX 1: Data. Nitrogen Measurements Oxygen De srived Experiment Thickened Primary Sludge Date NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) (mg/L) 31 0.09 2/22/93 594 35.4 30.7 29.57 0.09 2/23/93 611 33.8 29.2 0^08 2/24/93 657 45.2 33.3 0.10 2/25/93 624 0.10 2/26/93 575 34.9 37.6 53.5 35.6 0.15 2/27/93 626 2/28/93 574 31.4 31.1 0.17 0.38 3/1/93 538 35.2 31.7 21.0 21.3 0.20 3/2/93 630 30.5 28.1 0.11 3/3/93 653 31.4 32.1 0.17 3/4/93 558 29.2 28.1 0.19 3/5/93 563 34.9 32.3 0.13 3/6/93 562 Averages 598 34.3 30.8 0.16 Feb 23-Mar 6/93 Mixed Influent Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 1175 20.4 17.1 0.22 20.0 18.6 2/23/93 1160 0.24 22.4 19.0 2/24/93 1108 0.32 2/25/93 1258 26.5 19.3 0.15 23.1 22.6 2/26/93 1261 0.20 33.0 23.1 0.21 2/27/93 1225 26.6 26.3 0.20 2/28/93 1177 19.4 0.34 3/1/93 1153 . 22.5 36.7 32.1 0.19 3/2/93 1290 25.0 24.2 0.25 3/3/93 1240 22.4 22.6 3/4/93 1160 0.23 3/5/93 1087 26.5 25.9 0.32 3/6/93 1009 19.3 17.4 0.18 Averages 1177 25.3 22.5 0.24 Feb 23Mar 6/93  Date  182  Thickened Bio-P Sludge NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) (mg/L) 6.6 4.7 0.33 1714 0.38 10.1 8.5 1669 9.7 0.53 1528 12.0 0.20 1846 ' 9.2 6.4 8.9 0.29 1898 12.3 0.27 1781 14.1 11.6 21.9 0.23 1747 22.1 8.1 0.29 1723 10.8 0.19 1901 51.4 42.2 0.38 1784 20.0 20.7 14.1 14.0 0.29 1718 24.2 24.0 0.44 1573 0.22 ; 1423 4.8 3.7 1716 17.1 15.0 0.31  APPENDIX 1: Data. Nitrogen Measurements Oxygen De )rived Experiment ATAD 1 Sludge Date TKN DTKN (mg/L) (mg/L) 2/22/93 1017 533.6 606.9 2/23/93 998 2/24/93 1023 619.1 2/25/93 1100 422.3 2/26/93 1100 407.3 2/27/93 1131 444.6 2/28/93 1089 442.7 3/1/93 1059 513.9 3/2/93 1132 459.6 3/3/93 1119 451.6 3/4/93 1045 508.7 3/5/93 1083 493.7 3/6/93 1037 391.5 Averages 1076 480.2 Feb 23-Mar 6/93  NH3 (mg/L) 594.1 644.9 669.8 478.1 431.8 471.0 473.3 528.3 506.6 511.8 580.1 532.3 412.8 520.1  NOx ( mg/L) 0.09 0.44 -0.02 0.11 0.11 -0.71 0.08 0.36 0.20 0.20 0.12 0.22 0.66 0.15  ATAD 2 TKN (mg/L) 969 962 978 1024 1051 1084 1113 1066 1063 1048 1000 984 1029 1034  Note: Negative values for NOx result from subtraction of high colour interference results  183  Sludge DTKN (mg/L) 578.1 644.8 597.9 626.1 1072.1 685.7 710.3 997.5 749.9 861.9 598.5 540.8 591.0 723.0  NH3 NOx (mg/L) (mg/L) 644.0 -0.08 680.8 -0.06 652.1 0.93 666.0 0.09 973.9 0.11 696.8 0.32 756.9 0.12 959.2 0.19 782.8 0.22 869.1 0.20 668.6 0.19 569.5 0.07 601.0 1.11 739.7 0.29  APPENDIX 1: Data. Nitrogen Measurements Oxygen Satisfied Experiment Thickened Primary Sludge Date TKN DTKN NII3 (mg/L) (mg/L) (mg/L) 24.4 26 3/31/93 881 23.7 19.57 4/5/93 629 24.8 18.7 4/6/93 548 26.5 20.8 4/7/93 371 31.8 27.4 4/8/93 426 20.2 4/9/93 360 25.2 331 24.7 20.5 4/10/93 21.6 18.8 4/11/93 334 21.9 18.1 4/12/93 258 21.9 18.7 4/13/93 315 22.5 18.3 4/14/93 323 21.4 4/15/93 583 25.7 26.3 4/16/93 725 28.6 434 24.9 20.7 Averages Apr. 5-16/93 Date  NOx (mg/L) 0.11 0.17 0.32 0.37 0.12 0.21 0.15 0.11 0.12 0.20 0.20 0.10 0.12 0.18  Mixed influent Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L)  3/31/93 4/5/93 4/6/93 4/7/93 4/8/93 4/9/93 4/10/93 4/11/93 4/12/93 4/13/93 4/14/93 4/15/93 4/16/93 Averages Apr. 5-16/93  1141 1127 957 1087 924 979 960 936 964 933 1082 1179 1022  12.3 12.8 13.8 16.8 15.3 13.4 11.4 11.3 11.5 11.9 13.9 16.4 13.4  9.6 9.2 10.3 14.1 12.1 10.8 9.5 9.1 9.4 9.1 10.7 12.8 10.6  0.17 0.29 0.32 0.22 0.28 0.20 0.16 0.17 0.18 0.22 0.16 0.15 0.21  Thickened Bio-P Sludge NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) (mg/L) 1602 2.3 1.0 0.22 0.18 1616 1.8 0.5 0.4 0.26 1664 1.7 0.7 0.27 1499 2.2 0.31 1700 3.0 1.9 6.2 4.6 0.34 1447 3.0 1.9 0.25 1580 0.21 1541 2.1 0.9 0.22 1563 1.6 0.9 0.7 0.17 1566 2.0 0.24 1498 2.0 0.6 3.0 0.8 0.22 1544 5.1 0.4 0.19 1601 1568 2.8 1.2 0.24  APPENDIX 1: Data. Nitrogen Measurements Oxygen Satisfied Experiment Date ATAD 1 Sludge TKN DTKN (mg/L) (mg/L) 3/31/93 1080 323.1 4/5/93 1144 382.3 4/6/93 1098 362.3 4/7/93 1063 383.4 4/8/93 1029 324.9 4/9/93 996 310.9 4/10/93 945 302.3 4/11/93 913 299.6 4/12/93 916 327.8 4/13/93 954 295.9 4/14/93 879 297.4 4/15/93 901 305.1 4/16/93 940 294.4 Averages 982 323.8 Apr. 5-16/93  ATAD 2 TKN NH3 NOx (mg/L) (mg/L) (mg/L) 1068 359.5 0.33 1146 331.2 0.54 1218 288.8 1.24 1189 304.6 0.38 1163 302.6 2.13 1196 296.2 1.62 1093 280.0 1.33 944 300.5 0.59 996 317.5 0.12 901 289.1 1.12 861 260.5 1.46 937 258.3 0.49 916 287.7 0.23 1047 293.1 0.94  185  Sludge DTKN (mg/L) 490.5 501.6 547.9 561.2 614.6 551.3 504.8 488.8 480.6 526.3 447.0 436.9 468.4 510.8  NH3 NOx (mg/L) (mg/L) 579.1 0.17 429.6 0.45 497.7 0.36 508.9 0.20 557.5 0.35 499.4 0.81 487.3 0.92 487.2 0.93 471.5 0.75 502.3 0.65 427.1 0.72 419.6 1.03 456.1 0.93 478.7 0.67  APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 2 Thickened Primary Sludge Date TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 18 0.18 5/3/93 491 22.1 16.73 0.28 5/4/93 560 20.4 5/5/93 534 24.1 19.1 0.20 14.7 0.14 5/6/93 620 18.2 19.1 16.5 0.21 5/7/93 485 17.5 15.6 0.33 5/8/93 581 21.4 18.2 0.18 5/9/93 631 15.8 0.22 5/10/93 562 17.9 17.2 0.15 5/11/93 643 19.4 20.7 16.8 0.10 5/12/93 608 22.4 19.2 0.13 5/13/93 668 5/14/93 640 21.7 17.2 0.09 5/15/93 667 24.5 19.3 0.17 Averages 600 20.6 17.2 0.18 May 4-15/93 Mixed Influent Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 5/3/93 1187 11.7 8.9 0.20 5/4/93 1253 11.4 8.7 0.30 12.6 9.4 5/5/93 1208 0.18 9.9 7.4 5/6/93 1209 0.15 8.7 5/7/93 1059 11.1 0.29 9.5 7.8 5/8/93 1109 0.30 9.0 5/9/93 1178 11.2 0.17 9.8 8.0 5/10/93 1060 0.22 10.3 8.7 5/11/93 1109 0.27 10.7 8.3 5/12/93 1053 0.13 11.7 9.4 5/13/93 1018 0.26 8.7 5/14/93 1000 11.4 0.11 12.5 9.6 5/15/93 1040 0.18 1108 11.0 8.6 0.21 Averages May 4-15/93  Date  186  Thickened Bio-P Sludge NOx TKN DTKN NH3 (mg/L) (mg/L) (mg/L) (mg/L) 0.5 0.21 1832 2.2 1.4 0.33 1894 3.1 0.5 0.16 1831 2.1 0.7 0.16 1755 2.1 1590 3.6 1.5 0.37 1598 2.1 0.6 0.27 1.8 0.4 0.17 1685 0.8 0.21 1521 2.3 0.9 0.38 1542 1.9 0.16 1466 1.5 0.4 1341 1.8 0.4 0.39 0.12 1334 1.9 0.9 1386 1.5 0.6 0.19 1579 2.2 0.8 0.24  APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 2 Date ATAD 1 Sludge TKN DTKN NH3 (mg/L) (mg/L) (mg/L) 5/3/93 929 290.4 266.1 5/4/93 991 282.6 250.8 5/5/93 1058 293.6 259.3 5/6/93 1029 473.1 249.0 5/7/93 1091 264.8 248.5 5/8/93 1017 260.6 241.1 5/9/93 1006 266.1 242.5 5/10/93 1001 260.4 239.6 293.1 273.5 5/11/93 988 5/12/93 988 300.6 279.1 5/13/93 942 307.3 299.3 308.1 285.7 5/14/93 921 5/15/93 934 291.0 273.4 Averages 997 300.1 261.8 May 4-15/93  NOx (mg/L) 6.74 13.22 5.27 3.21 8.18 12.96 15.81 16.21 13.44 10.06 9.40 8.24 8.75 10.40  187  ATAD 2 TKN (mg/L) 929 905 933 981 983 1011 1007 1001 1008 983 958 932 941 970  Sludge DTKN (mg/L) 470.4 443.6 471.0 284.1 475.1 486.9 487.9 490.1 465.8 476.4 450.0 460.1 453.4 453.7  NH3 NOx (mg/L) (mg/L) 420.0 7.05 410.3 6.58 412.5 9.48 415.2 8.10 458.1 5.13 449.4 6.83 442.5 8.67 458.0 12.44 442.6 12.96 447.6 13.21 455.2 12.19 425.0 11.20 403.9 9.64 435.0 9.70  APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 1 Thickened Primary Sludge Date TP TDP P04 (mg/L) (mg/L) (mgT.) 12/30/92 6.0 5.8 1/6/93 107 1/11/93 99 5.7 4.0 1/12/93 109 5.3 3.4 1/13/93 110 10.4 8.8 1/14/93 98 5.1 5.3 1/15/93 99 6.2 4.3 1/16/93 115 5.9 4.3 - 1/17/93 109 5.5 2.1 1/18/93 113 14.3 9.7 1/19/93 88 7.1 5.2 1/20/93 111 5.3 3.9 1/21/93 118 9.2 8.4 5.4 3.1 1/22/93 114 1/23/93 120 4.8 3.5 Averages 107 7.1 5.2 Jan 11-Jan 22/93  Thickened Bio-P Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 15.0 12.7 600 7.5 7.2 648 11.4 9.1 697 15.3 10.8 9.3 729 12.2 666 19.0 18.2 9.0 702 11.1 732 14.0 10.1 6.1 649 14.3 659 18.1 14.2 771 10.3 9.2 703 11.4 9.6 766 13.5 12.4 754 6.5 4.4 806 12.3 9.3 706 13.1 10.2  Date  Mixed Influent Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 1/11/93 350 8.3 6.3 1/12/93 329 9.0 6.2 1/13/93 325 11.0 8.9 1/14/93 280 9.5 9.4 7.8 5.8 1/15/93 292 1/16/93 312 8.5 6.1 1/17/93 278 8.2 3.4 1/18/93 288 15.5 11.1 8.1 6.5 1/19/93 306 1/20/93 300 7.3 5.7 1/21/93 325 10.6 9.7 5.7 3.5 1/22/93 318 1/23/93 325 7.0 5.2 Averages 309 9.1 6.9 Jan 11-Jan 22/93 188  APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 1 ATAD 1 Sludge Date TP TDP P04 (mg/L) (mg/L) (mg/L) 1/6/93 400 140.5 143.3 183.6 163.1 1/11/93 374 175.3 128.1 1/12/93 345 175.9 133.5 1/13/93 346 190.9 172.7 1/14/93 299 162.0 102.5 1/15/93 291 145.0 85.9 1/16/93 260 80.4 1/17/93 293 131.8 152.6 108.8 1/18/93 264 1/19/93 271 133.1 118.4 122.6 110.2 1/20/93 253 128.3 . 79.0 1/21/93 276 123.6 98.1 1/22/93 277 1/23/93 289 124.5 105.8 Averages 296 152.1 115.1 Jan 11-Jan 22/93  ATAD 2 Sludge TP TDP (mg/L) (mg/L) 338 131.3 203.3 381 226.3 344 211.3 352 199.5 371 204.8 351 186.9 333 304 186.8 323 168.8 323 157.5 309 166.5 282 166.9 282 146.3 294 136.9 330 185.4  189  P04 (mg/L) 129.4 166.8 120.0 115.1 180.5 147.6 80.5 95.2 109.2 140.1 130.2 102.0 103.9 115.0 124.3  APPENDIX 1: Data. Phosphorus Measurements Oxygen Deprived Experiment Thickened Primary Sludge Date TP TDP P04 (mg/L) (mg/L) (mg/L) 2/22/93 114 10.9 5.7 2/23/93 109 15.9 2/24/93 115 17.0 5.6 12.2 5.9 2/25/93 106 2/26/93 97 8.5 6.5 6.7 2/27/93 104 17.6 9.7 2/28/93 98 6.5 3/1/93 91 11.8 6.5 1 0 1 9.9 3/2/93 3/3/93 105 10.2 7.6 3/4/93 113 15.2 7.9 3/5/93 106 11.9 7.2 3/6/93 114 16.2 11.8 Averages 105 13.3 7.3 Feb 23-Mar 6/93  Thickened Bio-P Sludge TP TDP P04 (mg/L) (mg/L) ( mg/L) 841 12.9 8.0 810 10.5 10.5 9.0 761 11.0 794 18.8 824 11.9 10.6 733 14.3 10.7 727 20.3 13.4 729 16.6 14.3 671 16.6 727 19.8 13.9 14.7 9.7 779 21.2 11.8 721 6.2 699 7.2 748 15.2 10.8  Mixed Influent Sludge TP TDP P04 (mg/L) (mg/L) ( mg/L) 2/22/93 491 11.9 2/23/93 473 13.1 6.9 13.6 7.3 2/24/93 451 15.6 8.6 2/25/93 463 8.6 2/26/93 474 ' 10.3 15.9 8.7 2/27/93 430 10.1 2/28/93 421 15.2 10.6 3/1/93 422 14.3 3/2/93 397 3/3/93 428 15.2 10.9 8.8 3/4/93 459 14.9 3/5/93 425 16.7 9.5 3/6/93 418 11.5 8.9 Averages 438 14.2 9.0 Feb 23-Mar 6/93 Date  190  APPENDIX 1: Data. Phosphorus Measurements Oxygen De )rived Experiment Date  ATAD 1 Sludge TP TDP (mg/L) (mg/L) 2/22/93 398 269.6 2/23/93 406 300.2 2/24/93 411 345.0 2/25/93 406 259.1 252.4 2/26/93 417 2/27/93 417 242.3 244.5 2/28/93 418 395 267.6 3/1/93 3/2/93 414 246.7 3/3/93 394 241.3 286.3 3/4/93 406 295.9 3/5/93 444 396 248.8 3/6/93 410 269.2 Averages  P04 (mg/L) 212.3 234.0 202.9 185.7 187.4 197.8 189.3 208.6 207.8 234.9 205.3 208.4 204.7 205.6  ATAD 2 Sludge TP TDP (mg/L) (mg/L) 259.5 381 261.6 399 401 263.6 416 250.3 416 468.9 406 294.0 414 307.7 406 455.6 305.6 404 409 352.4 417 270.9 379 235.5 390 261.2 405 310.6  Feb 23-Mar 6/93  191  P04 (mg/L) 196.5 181.7 209.8 187.8 169.9 185.4 177.7 182.9 202.3 193.0 209.1 182.2 179.7 188.5  A P P E N D I X 1: Data. Phosphorus Measurements Oxygen Satisfied Experiment Thickened Primary Sludge P04 TP TDP (mg/L) (mg/L) (mg/L) 3.5 4.5 3/31/93 209 3.8 4/5/93 128 3.5 106 4.5 4.1 4/6/93 4/7/93 68 4.4 4.3 78 6.8 6.9 4/8/93 4.2 4/9/93 56 4.2 5.7 58 5.8 4/10/93 68 5.5 5.6 4/11/93 4.2 4/12/93 44 4.2 58 4.7 4.5 4/13/93 4.2 4/14/93 64 4.6 4.8 4/15/93 109 4.5 4.7 4.7 4/16/93 125 80 4.8 4.8 Averages  Date  Thickened Bio-P Sludge TDP P04 TP (mg/L) (mg/L) (mg/L) 9.4 792 9.8 4.0 778 .4.2 801 3.2 3.3 746 1.9 2.4 5.1 807 5.1 766 6.9 6.7 9.0 8.9 735 6.8 777 6.7 5.5 5.6 748 799 7.0 7.3 3.7 3.8 769 4.7 672 4.2 3.1 3.9 704 759 5.0 5.2  Apr. 5-16/93 Mixed influent Sludge TDP P04 TP (mg/L) (mg/L) (mg/L) 3.8 4.0 4/5/93 465 3.7 4/6/93 466 3.8 4/7/93 420 3.1 3.3 6.0 4/8/93 457 5.9 5.6 5.5 4/9/93 425 410 7.4 7.4 4/10/93 436 6.1 6.2 4/11/93 410 4.9 4/12/93 4.9 5.9 5.9 4/13/93 442 4.0 4/14/93 430 4.1 4.7 . 4/15/93 401 4.4 3.9 4.3 4/16/93 426 5.0 432 4.9 Averages  Date  Apr. 5-16/93  192  APPENDIX 1: Data. Phosphorus Measurements Oxygen Satisfied Experiment ATAD 1 Sludge Date TP TDP (mg/L) (mg/L) 3/31/93 463 165.9 167.6 4/5/93 471 4/6/93 451 156.4 4/7/93 431 177.8 4/8/93 423 . 172.9 182.1 4/9/93 413 4/10/93 418 186.4 195.2 4/11/93 413 4/12/93 401 205.7 195.2 4/13/93 414 4/14/93 404 205.1 4/15/93 331 189.2 4/16/93 370 166.1 Averages 411 183.3 Apr. 5-16/93  P04 (mg/L) 170.4 182.1 164.0 189.4 176.2 188.8 190.7 200.6 209.7 202.0 190.8 185.7 170.9 187.6  ATAD 2 Sludge TP TDP (mg/L) (mg/L) 188.3 439 469 174.2 469 178.3 465 176.8 197.3 458 468 193.9 426 191.8 434 199.3 427 204.4 415 229.7 403 207.0 364 200.6 357 '. 208.3 430 196.8  193  P04 (mg/L) 196.3 176.2 193.0 214.0 203.8 196.9 197.4 203.2 208.0 237.4 200.2 202.5 209.1 203.5  APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 2 Thickened Primary Sludge  Date  Thickened Bio-P Sludg e  TP  TDP  P04  TP  TDP  P04  (mg/L)  (mg/L)  ( mg/L)  (mg/L)  (mg/L)  (mg/L)  5/3/93  103  5.1  5.2  1081  13.0  14.3  5/4/93  107  3.6  3.7  1125  19.3  19.9  5/5/93  104  6.3  6.1  1041  14.9  17.2  5/6/93  118  2.8  3.4  848  13.7  15.2  5/7/93  87  3.1  3.4  794  4.8  5.8  5/8/93  114  3.0  3.1  796  8.6  8.7  5/9/93  130  6.2  6.5  817  7.2  7.1  5/10/93  104  3.3  3.3  776  9.1  9.9  5/11/93  124  4.3  4.4  720  9.4  9.4  5/12/93  113  4.4  4.0  701  6.3  6.8  5/13/93  129  4.8  5.2  676  8.4  8.3  5/14/93  117  4.7  4.7  662  6.9  7.4  5/15/93  128  5.4  5.0  702  7.1  7.2  115  4.3  4.4  805  9.6  10.3  Averages May 4-15/93  Mixed Influent Sludge  Date  TP  TDP  P04  (mg/L)  (mg/L)  ( mg/L)  5/3/93  611  9.2  9.9  5/4/93  636  11.8  12.1  5/5/93  590  10.8  11.8  5/6/93  497  8.5  9.5  5/7/93  454  4.0  4.6  5/8/93  468  5.9  6.0  5/9/93  487  6.7  6.8  5/10/93  453  6.3  6.7  5/11/93  434  6.9  7.0  5/12/93  419  5.4  5.4  5/13/93  414  6.7  6.8  5/14/93  400  5.9  6.1  5/15/93  426  6.3  6.2  473  7.1  7.4  Averages  '  May 4-15/93  194  APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 2 ATAD 1 Sludge Date TP TDP P04 (mg/L) (mg/L) (mg/L) 5/3/93 393 187.5 196.3 230.7 5/4/93 466 229.1 259.7 253.4 5/5/93 501 221.6 255.6 5/6/93 497 232.7 235.2 5/7/93 501 226.7 230.0 5/8/93 478 214.1 5/9/93 452 220.1 5/10/93 439 201.8 215.9 221.8 226.2 5/11/93 429 5/12/93 439 198.2 214.2 204.3 199.1 5/13/93 406 189.8 194.6 5/14/93 401 180.9 192.7 5/15/93 400 Averages 451 215.1 222.2 May 4-15/93  ATAD 2 Sludge TP TDP (mg/L) (mg/L) 372 194.3 384 195.9 216.6 407 446 251.8 457 224.6 234.8 453 241.3 472 240.6 461 474 225.6 221.4 460 218.4 444 217.9 431 416 208.5 442 224.8  195  P04 (mg/L) 198.9 197.5 213.7 229.6 238.7 231.0 233.5 242.0 227.7 228.1 224.5 222.6 219.2 .225.7  APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Excess Experiment No. 1 Primary Sludge Bio-P Sludge Date Alkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 1/11/93 1/12/93 1/13/93 1/14/93 1/15/93 1/16/93 1/17/93 1/18/93 1/19/93 1/20/93 1/21/93 375 1/22/93 485 420 1/23/93 605 Average 485 375 Jan 11-Jan 22/93 Date  ATAD 1 Sludge Alkalinity (mg/L as CaC03)  1/11/93 1/12/93 1/13/93 1/14/93 1/15/93 1/16/93 1/17/93 1/18/93 1/19/93 1/20/93 1/21/93 1/22/93 1173 1/23/93 1173 Average 1173 Jan 11-Jan 22/93  Note: Influent sludges are thickened  ATAD 2 Sludge Alkalinity (mg/L as CaC03)  pH  pH  8.1 8.0  8.4 8.1  8.2 8.0 8.0 8.1 7.9 8.3 7.7  8.2 8.2 8.2 8.3 7.9 8.3 7.8  1650 1685 1650  196  APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Deprived Experiment Primary Sludge Bio-P Sludge Date Alkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 2/22/93 510 470 2/23/93 474 420 2/24/93 2/25/93 385 2/26/93 355 2/27/93 306 406 2/28/93 3/1/93 408 3/2/93 332 • 3/3/93 520 3/4/93 321 3/5/93 316 3/6/93 313 Average 350 409 Feb. 23-Mtar 6/93 ATAD 1 Sludge Alkalinity (mg/L as CaC03) 2/22/93 2030 2/23/93 1965 2/24/93 2/25/93 2/26/93 1515 2/27/93 1505 2/28/93 3/1/93 1474 3/2/93 3/3/93 3/4/93 1556 3/5/93 3/6/93 1480 1582 Average Feb. 23-Mtar 6/93  Note: Influent sludges are thickened  ATAD 2 Sludge Alkalinity (mg/L as CaC03) 1921  Date  pH  6.5 6.9 6.9 7.2 7.1 7.1 7.1 7.2 6.8 6.9 7.0 7.0 7.1  1550 1553 1763  1920 1920 1929 1772  197  pH 7.3 7.4 7.1 7.7 7.8 7.6 7.7 7.7 7.5 7.5 7.4 7.3 7.7  APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Satisfied Experiment Primary Sludge Bio-P Sludge Date Ajjkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 3/31/93 1199 662 4/5/93 435 4/6/93 585 4/7/93 435 306 4/8/93 4/9/93 449 412 4/10/93 408 375 4/11/93 4/12/93 510 4/13/93 439 4/14/93 495 495 4/15/93 4/16/93 Average 468 422 April 5 - 16 /93 ATAD 1 Sludge Alkalinity (mg/L as CaC03) 3/31/93 1786 4/5/93 4/6/93 1700 4/7/93 1444 4/8/93 4/9/93 4/10/93 1300 4/11/93 1290 4/12/93 4/13/93 1339 4/14/93 4/15/93 1310 4/16/93 Average 1397 April 5 - 16 /93  Note: Influent sludges are thickened  ATAD 2 Sludge Alkalinity (mg/L as CaC03) 2300  Date  pH  7.3 7.5 7.6 7.6 7.5 7.5 7.5 7.5 7.4 7.4 7.4 7.4 7.4  2401 2320 2045 1945 1984 1915 2102  198  pH  7.6 7.8 7.7 7.9 7.8 7.8 .7.7 7.9 7.9 7.8 7.8 7.8 7.8  APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Excess Experiment No. 2 Primary Sludge Bio-P Sludge Date Alkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 5/3/93 638 5/4/93 455 5/5/93 525 5/6/93 354 5/7/93 520 525 5/8/93 505 5/9/93 475 5/10/93 5/11/93 470 546 5/12/93 364 419 5/13/93 5/14/93 5/15/93 Average 439 526 May 4-15/93 Date  ATAD 1 Sludge Alkalinity (mg/L as CaC03)  5/3/93 5/4/93 5/5/93 5/6/93 5/7/93 5/8/93 5/9/93 5/10/93 5/11/93 5/12/93 5/13/93 5/14/93 5/15/93 Average May 4-15/93  1235 1290 1250 1275 1332 1445  Note: Influent sludges are thickened  ATAD 2 Sludge Alkalinity (mg/L as CaC03)  PH 8.0 7.8 7.8, 7.8 7.7 7.8 7.7 7.8 7.8 8.0 7.7 7.9 8.0  1903 1904 1940 1975 2065 1990  1304  1963  199  pH  8.0 8.0 7.9 7.9 7.8 7.9 7.9 7.9 7.9 8.0 7.9 8.0 8.0  APPENDIX 1: Data. COD Measurements Oxygen Excess Experiment No. 1 Primary Sludge Bio-P Sludge Date Total COD Total COD (mg/L) (mg/L) 22657 1/11/93 1/12/93 1/13/93 1/14/93 1/15/93 32153 31751 1/16/93 28803 1/17/93 29964 1/18/93 30858 1/19/93 22371 1/20/93 25113 1/21/93 25690 29149 27907 1/22/93 27996 29460 1/23/93 28131 27869 Averages Jan 11-Jan 22/93 Note: Influent Sludges are Thickened Date  ATAD 1 Total COD (mg/L) 16454 20343  1/11/93 1/12/93 1/13/93 19288 1/14/93 1/15/93 20157 1/16/93 18385 22044 1/17/93 1/18/93 1/19/93 20705 1/20/93 17512 1/21/93 20744 1/22/93 1/23/93 Averages 19515 Jan 11-Jan 22/93  ATAD 2 Total COD (mg/L) 17102 17218 15833 18007 21731 16689 18385 14254 16992 17357  Mixed Influent Sludge Total COD (mg/L)  32024 29600 25087 25505 28752 29021 28332  APPENDIX 1: Data. COD Measurements Oxygen Deprived Experiment Primary Sludjge Bio-P Sludge Mixed Influent Sludge Date Soluble Soluble Total Total Soluble Total COD COD COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 31886 272 27450 85 29579 175 2/23/93 26388 66 34787 136 2/24/93 43885 212 2/25/93 26140 27154 2/26/93 25040 29124 151 27734 63 2/27/93 30629 246 2/28/93 24807 205 26058 72 3/1/93 23452 349 3/2/93 157 274 29338 49 32249 3/3/93 35402 3/4/93 28523 149 26942 55 3/5/93 30235 251 3/6/93 31441 267 27269 61 29272 160 Averages Feb 23-Mar 6/93 Note: Influent sludges are thickened Date  ATAD 1 Total COD (mg/L) 2/22/93 24354 2/23/93 2/24/93 22626 2/25/93 2/26/93 21732 2/27/93 20226 2/28/93 19887 3/1/93 3/2/93 3/3/93 21373 3/4/93 3/5/93 23916 3/6/93 Averages 21627 Feb 23-Mar 6/93  Soluble COD (mg/L) 3061  ATAD 2 Total COD (mg/L) 19018  Soluble COD (mg/L) 2030  2039  17138  1892  1177  17563 18752  1348  1258  17897  1956  1796  18109  1744  1712  18189  1256  1596  17941  1639  APPENDIX 1: Data. COD Measurements Oxygen Satisfied Experiment Mixed Influent Sludge Bio-P Sludge Primary Slud?e Date Soluble Total Soluble Soluble Total Total COD COD COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 44161 231 55 421 34449 3/31/93 54682 115 39 31956 198 33570 4/5/93 30208 4/6/93 32453 30 26496 80 16797 148 4/7/93 4/8/93 38 26438 81 126 32173 4/9/93 20345 4/10/93 4/11/93 31 24911 75 123 34051 4/12/93 15008 4/13/93 18043 135 33761 31 26216 81 4/14/93 4/15/93 32479 71 38935 168 273 4/16/93 45929 24388 167 33081 40 29159 100 Averages Note: mfluent sludges are thickened Apr. 5-16/93 ATAD 1 Total COD (mg/L) 3/31/93 29232 4/5/93 25629 4/6/93 4/7/93 21985 4/8/93 4/9/93 20807 4/10/93 4/11/93 19449 4/12/93 4/13/93 4/14/93 20114 4/15/93 4/16/93 19156 21190 Averages Apr. 5-16/93  Soluble COD (mg/L) 759 763  ATAD 2 Total COD (mg/L) 23920 24670  Soluble COD (mg/L) 1154 969  679  24919  1041  400  22143  707  359  19543  600  281  17821  470  381 477  14160 20543  501 714  Date  202  APPENDIX 1: Data. COD Measurements Oxygen Excess Experiment No. 2 Mixed Influent Sludge Primary Sludj»e Bio-P Sludge Date Total Soluble Soluble Soluble Total Total COD COD COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 42 29147 130 226 35214 5/3/93 22574 5/4/93 5/5/93 21980 274 34890 48 28693 157 5/6/93 56 28686 114 175 32310 5/7/93 21178 5/8/93 28680 115 28 206 29278 5/9/93 28044 27873 146 30318 66 25225 232 5/10/93 5/11/93 29655 152 28893 . 45 30480 268 5/12/93 5/13/93 5/14/93 44 33247 142 38868 248 28059 5/15/93 27629 234 30625 48 29472 137 Averages May 4-15/93 Note: Influent sludges are thickened Date  ATAD 1 Total COD (mg/L) 5/3/93 20190 5/4/93 19984 5/5/93 5/6/93 5/7/93 22222 5/8/93 5/9/93 21253 21801 5/10/93 5/11/93 5/12/93 21754 5/13/93 5/14/93 5/15/93 19541 Averages 21093 May 4-15/93  Soluble COD (mg/L) 408  ATAD 2 Total COD (mg/L) 18944  Soluble COD (mg/L) 549  388  18465  544  376  18568  647  342 364  18387 18809  605 712  369  17311  567 r  452 382  18267 18301  203  662 623  APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 1 Primary Sludge Date Acetate (mg/L) 1/11/93 1/12/93 1/13/93 1/14/93 1/15/93 1/16/93 1/17/93 1/18/93 1/19/93 54.99 1/20/93 50.77 1/21/93 40.32 1/22/93 38.39 1/23/93 39.49  Date  1/11/93 1/12/93 1/13/93 1/14/93 1/15/93 1/16/93 1/17/93 1/18/93 1/19/93 1/20/93 1/21/93 1/22/93 1/23/93  Bio-P Sludge Butyrate Acetate  ProIsoprionate Butyrate (mg/L) (mg/L) (mg/L)  42.17 43.10 29.89 26.56 29.66  1.15 1.10 0.69  0.83 0.85  ATAD 1 ATAD 2 Acetate Acetate (mg/L) (mg/L)  10.86 9.98 2.70 2.55 0.00  9.00 11.94 0.11 0.00 0.00  204  (mg/L)  1.75 1.62 1.61 0.00 0.00  APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Deprived Experiment Thickened Primary Sludge Date  Bio-P Sludge Acetate  Butyrate A- . IsoIsoAcetate Proprionate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 71.90 74.65 1.19 2.19 3.57 2/23/93 0.00 0.88 2/24/93 51.92 51.67 2/25/93 2.23 0.55 1.93 2/26/93 58.34 62.32 2/27/93 2/28/93 3/1/93 2.65 2.06 5.45 1.24 1.85 3/2/93 79.57 80.10 3/3/93 2.44 3/4/93 69.81 70.51 1.61 4.63 3/5/93  ATAD 1 AButyrate Iso- Valerate Acetate ProprioIsonate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 85.33 173.29 32.65 2/22/93 1228.14 169.61 148.40 26.46 2/23/93 23.45 135.51 7.10 116.61 2/24/93 500.97 2/25/93 2/26/93 9.56 2/27/93 2/28/93 3/1/93 77.97 0.51 44.97 3/2/93 650.36 13.59 81.42 3/3/93 32.20 4.60 55.65 63.04 3/4/93 390.71 3/5/93  Date  205  APPENDIX l:Data. Volatile Fatty Acids Measurements Oxygen Deprived Experiment ATAD 2 Date AIsoIsoButyrate Acetate ProprioValerate Valerate Butyrate nate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 33.00 92.38 85.25 97.92 2/22/93 419.19 2/23/93 58.53 54.87 65.95 2/24/93 274.40 2/25/93 2/26/93 2/27/93 2/28/93 3/1/93 1.00 3/2/93 0.68 3/3/93 3/4/93 4.17 3/5/93  206  APPENDIX l:Data. Volatile Fatty Acids Measurements Oxygen Satisfied Experiment Primary Sludge Date  Bio-P Sludge Acetate  AButyrate IsoAcetate ProprioIsonate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 4/5/93 4/6/93 4/7/93 4/8/93 4/9/93 4/10/93 4/11/93 4/12/93 4/13/93 4/14/93 4/15/93 4/16/93  Date  4/5/93 4/6/93 4/7/93 4/8/93 4/9/93 4/10/93 4/11/93 4/12/93 4/13/93 4/14/93 4/15/93 4/16/93  30.29  19.45  0.74  1.28  2.46  29.26 34.04  17.68 16.58  0.70 1.03  1.47 1.06  1.15 0.00  36.71  23.97  1.19  1.58  0.00  34.08  21.94  1.32  1.56  0.96  51.77 .  40.65  2.40  3.99  ATAD 2 ATAD 1 Acetate Acetate ProprioIso(mg/L) nate Butyrate (mg/L) (mg/L) (mg/L) 1.42  0.54  7.87 0.48  2.04  1.15  0.30  1.37 3.16 3.18  3.01 2.71  0.49  0.22  3.01 5.61  207  1.74  0.00  APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 2 Primary Sludge Date A- ' . IsoAcetate ProIsoButyrate Valerate Valerate prionate Butyrate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 5/4/93 49.99 44.88 1.11 2.25 5/5/93 49.97 1.12 2.79 5/6/93 48.11 . 5/7/93 1.13 34.94 1.02 1.77 5/8/93 40.44 1.38 5/9/93 52.96 49.55 5/10/93 5.06 1.78 2.03 5/11/93 71.06 77.38 2.12 5/12/93 2.22 5.26 1.82 2.21 5/13/93 70.78 75.63 5/14/93 5/15/93  Bio-P Sludge Acetate ProIsoButyrate Aprionate Butyrate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 5/4/93 3.57 0.31 5/5/93 5/6/93 2.96 0.31 5/7/93 0.86 5/8/93 4.67 1.16 0.32 5/9/93 2.12 5/10/93 5/11/93 2!30 5/12/93 5/13/93 1.66 5/14/93 5/15/93  Date  208  APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 2 ATAD 1 ATAD 2 Date ProAcetate Acetate prionate (mg/L) (mg/L) (mg/L) 5/4/93 3.57 2.09 5/5/93 3.07 0.40 5/6/93 2.60 5/7/93 2.22 5/8/93 1.55 5/9/93 2.55 3.99 5/10/93 5.31 5/11/93 9.02 5/12/93 5.18 5/13/93 2.91 5/14/93 5/15/93  209  APPENDIX 1: Discharge Gas Measurements Oxygen Deprived Experiment ATAD 1 ATAD 2 Date N2 C02 C02 02 (%) (%) (%) (%) 2/23/93 10.50 10.70 78.80 2/24/93 2/25/93 6.69 7.37 80.83 2/26/93 11.80 2/27/93 2/28/93 3/1/93 10.09 3/2/93 16.82 4.51 78.67 3/3/93 3/4/93 8.93 3/5/93 15.23 4.19 80.58 3/6/93 Note: (%)- percent by volume  02 (%)  N2 (%)  13.97  79.35  11.50  78.41  11.25  79.82  Oxygen Satisfied Experiment ATAD 2 ATAD 1 Date NH3 C02 C02 02 N2 (g/d) (%) (%) (%) (%) 4/5/93 7.69 13.31 78.73 4/6/93 7.95 4/7/93 4/8/93 0.001 6.00 15.13 78.39 4/9/93 6.48 4/10/93 0.002 4.41 4/11/93 6.75 14.94 78.32 4/12/93 4/13/93 0.001 4/14/93 7.23 14.42 78.36 5.06 4/15/93 6.61 13.30 78.61 0.003 4/16/93 8.09 Note: (%)= percent by volume  210  02 (%)  N2 (%)  NH3 (g/d)  13.51  78.80  0.001  15.24  78.76  0.001  17.73  77.86  0.001  0.002 16.72 14.73  78.21 78.66  0.002  APPENDIX 1: Discharge Gas Measurements Oxygen Excess Experiment No. 2 ATAD 2 ATAD 1 Date NH3 C02 C02 02 N2 (g/d) (%) (%) (%) (%) 5/4/93 0.00 20.18 79.82 0.031 3.41 5/5/93 19.14 79.95 0.024 1.38 5/6/93 0.90 5/7/93 0.256 2.11 5/8/93 1.14 18.74 80.12 5/9/96 5/10/93 2.66 18.14 79.97 0.195 5/11/93 1.89 5/12/93 17.87 80.02 2.31 5/13/93 2.11 5/14/93 0.156 5/15/93 Note: (%)= percent by volume  211  02 (%) 18.63  N2 (%) 77.95  NH3 (g/d) 0.094  18.64  79.98  0.118  17.83  80.06  0.090  17.65  79.69  0.149  18.03  79.66 0.186  APPENDIX 2  BALANCE CALCULATIONS and BALANCE ERRORS  212  A P P E N D I X 2: B A L A N C E S A N D B A L A N C E E R R O R S Sample Calculations for M a y 4/93 Appendix 2a: Liquid Balance Variables P = 12-liter  Volume of thickened primary sludge feed  S := 13 liter  Volume o f thickened secondary sludge feed  A 1 S = 0.5-liter  Volume o f A T A D 1 sludge removed by sampling  A I T := 25.25-liter  Volume o f A T A D 1 sludge measured in transfer tank  A 1 T R := 0.25-liter  Volume o f A T A D 1 sludge remaining in transfer tank after pumping  A 1 P := 0.27-liter  Volume o f A T A D 1 sludge remaining in pipes after pumping  A 2 S := 0.5 liter  Volume o f A T A D 2 sludge removed by sampling  A 2 T = 22 liter  Volume o f A T A D 2 sludge measured in transfer tank  T A : = ( 1 4 + 273)-K  Ambient air temperature at feeding time  T A 1 := (52 4 - 2 7 3 ) K  A T A D 1 temperature just before feeding  T A 2 := (59.8 + 2 7 3 ) K  A T A D 2 temperature just before feeding  kg <L := 999.22m L .:= 987.04-  Density of water at ambient temp, at feeding time Density of water at A T A D 1 sludge temp, just before feeding  kg m  3  kg  Density of water at A T A D 2 sludge temp, just before feeding  f, := 983.30 — Y  2  m  <fr := 998.2  3  kg  Density of water at 20 deg. C  20  m H := 0.735  Relative Humidity (%)  liter A F 1 :=.4.613min  Average airflow into A T A D 1  liter A F 2 := 0.931min  Average airflow into A T A D 2  A T A := (15.8 +- 2 7 3 ) K  Average ambient temperature over past 24 hours  A T A 1 := (48.5 +• 2 7 3 ) K  Average temperature in A T A D 1 over past 24 hours  A T A 2 := (60.7 + 2 7 3 ) K  Average temperature in A T A D 2 over past 24 hours  P P A T A := 2442.4-Pa  Partial pressure of water vapour at average ambient temp.  P P A T A 1 := 11587.5-Pa  Partial pressure of water vapour at average A T A D 1 temp.  P P A T A 2 := 20706.8-Pa  Partial pressure o f water vapour at average A T A D 2 temp.  mole := 6.022-10  23  joule R := 8.3144— K-mole 213  1. Calculation o f sludge volumes in and out o f reactors at operating temperatures. Influent = P + S Influent =25 -liter A T A D 1 Out = A 1 S + A I T A T A D 1 Out = 25.75 -liter ATAD2In = A I T - A1TR - A1P A T A D 2 I n =24.73-liter A T A D 2 0 u t := A 2 T + A 2 S A T A D 2 0 u t =22.5-liter 2. Adjustment o f sludge volumes to 20 deg. C base  <> lo  V A 2 I n := A T A D 2 I n -  V I n = Influent  +20  +20  V I n =25.03-liter V A 2 I n = 24.45 -liter V A 2 0 u t := A T A D 2 0 u t  V A l O u t := A T A D 1 Out +20  V A l O u t =25.46-liter  +20  V A 2 0 u t =22.16-liter The mean was calculated for volumes in and volumes out for both A T A D tanks over 12 days o f stable operation. Next, the volume o f water lost in the saturated off-gas was calculated as follows: 3. Calculation o f volume lost with saturated off-gas P P A T A H AF1 / „ kg Glln=— -(0.018mole/ R ATA &  kg  G l l n = 0.089  G10ut:=  day  PPATA1AF1 I kg (0.018mole/ R ATAl M  O  G l O u t =0.518  G A 1 :=  Mass o f water in aeration air  6  .kg  Mass o f water in air out from A T A D 1  day  GlOut - Glln 20  G A 1 =0.43  liter  Mass o f water lost in off-gas from A T A D 1  day 214  T o determine volume balances, the difference between mean volume in and mean volume out o f each tank (including the mean mass o f water lost in the off gas, was calculated over a 12 day period (2 SRT's) o f relatively stable operation. M e a n V A l I n = 25-liter M e a n V A l O u t := 24.9liter MeanVAl Out-MeanVAlIn AlBe =— 100 MeanVAlIn n  A l B e =-0.4  Percent error in liquid balance around A T A D 1  The same procedure was followed for A T A D 2, and for the entire system the difference between all mean inputs and outputs was used to calculate balance error.  215  Appendix 2b: Solids Balance For each day, the concentration o f non-volatile solids in all streams was calculated as the difference between the concentration o f total solids and the concentration o f volatile solids The daily mass o f non-volatile solids was determined by multiplying the concentration o f each stream by the measured stream volume adjusted to 20 degrees C . Next, the mean o f 12 consecutive days o f non-volatile solids mass determinations was determined for each stream. (Example values from the Oxygen Excess Experiment N o . 2) A l I n N V S := 131  A 2 I n N V S := 120--^day  day  A 2 0 u t N V S := 1 1 5 day  A l O u t N V S := 1 2 5 day  AlOutNVS - AUnNVS  ;=  100  AlInNVS BA1  B  A  2  =  Percent error in solids balance around ATAD 1  =-4.6  A20utNVS - A 2 h N V S  )  0  0  A2InNVS B A 2 =-4.2  BSystem :=  Percent error in solids balance around ATAD 2  A20utNVS - A l I n N V S + ( A l O u t N V S - A2InNVS) -• 100 AlInNVS BSystem =-8.397 Percent error in solids balance around entire system  216  Volatile solids destruction was determined by calculating the percentage difference between the mean mass o f volatile solids entering a tank and the mean mass of volatile solids exiting a tank. Example values from Oxygen Excess Experiment N o . 2.  A l l n V S := 434 — day  A 2 I n V S = 333  A l O u t V S := 348 — day  A20utVS = 2 9 4 day  VSDAl :- ' A  O U l V S  - " A  n V S  AllnVS  day  100  V S D A l =-198  Percent volatile solids destruction in ATAD 1  _ _ A20utVS - A2InVS , V S D A 2 := 100 A2InVS T  r  n  n  V S D A 2 =-11 7  Percent volatile solids destruction in ATAD 2  Measurement errors for the solids balance were determined by combining the calculated error in the liquid balance with the precision calculated for the solids concentration measurements. Precision was defined as the average covariance for the three daily solids determinations, and is documented on barcharts shown in Chapter 4. Solids precisions: Oxygen Excess Experiment N o . 2, percent P P := 1.3  P A 1 := 0.8  PS := 1.9  P A 2 := 1.1  Volume balance errors: Oxygen Excess Experiment N o . 2, percent V A 1 := 0.8  V A 2 := 1.3  VSystem := 2.0  217  For influent sludge solids concentration, the error was taken as the greater o f the primary and secondary precisions. EMassIn  PS EMassIn = 1.9  The total solids mass error around A T A D 1 was calculated as the sum o f the influent solids concentration precision, the A T A D 1 solids concentration precision, and the liquid balance percent error around A T A D 1. E M a s s A l := EMassIn + P A 1 + V A 1 E M a s s A l =3.5 The total solids mass error around A T A D 2 was calculated as the sum o f the A T A D 1 solids concentration precision, the A T A D 2 solids concentration precision, and the liquid balance percent error around A T A D 2. E M a s s A 2 := P A 1 + P A 2 + V A 2 EMassA2=3.2  The total solids mass error around the system was calculated as the sum o f the influent solids concentration precision, the A T A D 2 solids concentration precision, and the liquid balance percent error around the system. EMassSystem = EMassIn + P A 2 -t- VSystem EMassSystem = 5.0  218  Appendix 2c: Nitrogen Balance The daily mass o f nitrogen was determined by multiplying the concentration o f each stream by the measured stream volume adjusted to 20 deg. C . Total Nitrogen was determined by adding the mass o f T K N to N O x . Next, the mean o f 12 consecutive days o f total nitrogen determinations was determined for each stream. T o this mean was added the mean o f ammonia in the off-gas mass measurements. Example values from the Oxygen Excess Experiment N o . 2 are listed.  A l I n T N := 27.73 — day  A 2 I n T N := 23.96day  A l O u t T N := 2 5 . 1 4 — day  A 2 0 u t T N = 23.50—^day  „ , AlOutTN - AlInTN , B A 1 := 100 AlInTN A  n  n  B A 1 =-9.3  Percent error in nitrogen balance around A T A D 1  „ A20utTN - A2InTN , B A 2 := 100 A2InTN n  n  n  Percent error in nitrogen balance  B A 2 =-1.9  BSystem :=  around A T A D 2  A 2 0 u t T N - A l I n T N + ( A l O u t T N - A2InTN) -100 AlInTN Percent error in nitrogen balance around entire system  BSystem =-11.0  219  Measurement errors for the nitrogen balance were determined by combining the calculated error in the liquid balance with the precision calculated for the T K N concentration measurements. Precision was defined as the average covariance for the daily T K N determinations, and is documented on barcharts shown in Chapter 4. T K N precisions: Oxygen Excess Experiment N o . 2, percent P P := 4.8  P A 1 - 2.5  PS =4.9  P A 2 := 2,3  Volume balance errors: Oxygen Excess Experiment N o . 2, percent V A 1 = 0.8  V A 2 := 1.3  VSystem := 2.0  For influent mixed sludge nitrogen concentration, the error was taken as the greater o f the primary and secondary precisions. EMassIn = PS EMassIn =4.9 The total nitrogen mass error around A T A D 1 was calculated as the sum o f the influent mixed sludge nitrogen concentration precision, the A T A D 1 nitrogen concentration precision, and the liquid balance percent error around A T A D 1. E M a s s A l := EMassIn t- P A 1 + V A 1 EMassAl=8.2 The total nitrogen mass error around A T A D 2 was calculated as the sum o f the A T A D 1 nitrogen concentration precision, the A T A D 2 nitrogen concentration precision, and the liquid balance percent error around A T A D 2. E M a s s A 2 := P A 1 + P A 2 + V A 2 EMassA2=6.1 The total nitrogen mass error around the system was calculated as the sum o f the influent mixed sludge nitrogen concentration precision, the A T A D 2 nitrogen concentration precision, and the liquid balance percent error around the system. EMassSystem = EMassIn + P A 2 -t- VSystem EMassSystem =9.2  220  Appendix 2d: Phosphorus Balance The daily mass o f phosphorus was determined by multiplying the concentration of each stream by the measured stream volume adjusted to 20 degrees C. Next, the mean o f 12 consecutive days o f total phosphorus determinations was determined for each stream. Example values from the Oxygen Excess Experiment N o . 2 are listed.  A l I n T P := 11.83-  JL  A 2 I n T P := 10.72-  day A l O u t T P := 11.20-  B A 1 :=  J L  J L  day  A 2 0 u t T P := 10.55day  day  AlOutTP - AlInTP -100 AlInTP BA1  Percent error in phosphorus balance around A T A D 1  =-5.3  „ .„ A 2 0 u t T P - A2InTP B A 2 := 100 A2InTP Percent error in phosphorus balance around A T A D 2  B A 2 =-1.6  BSystem =  A20utTP - A l I n T P + ( A l O u t T P - A2InTP) ^— 100 AlInTP BSystem =-6.8  Percent error in phosphorus balance around entire system  221  Measurement errors for the phosphorus balance were determined by combining the calculated error in the liquid balance with the precision calculated for the T P concentration measurements. Precision was defined as the average covariance for the daily T P determinations, and is documented on barcharts shown in Chapter 4 . T P precisions: Oxygen Excess Experiment N o . 2, percent P A 1 : 3.9 PA2=3.6 Volume balance errors: Oxygen Excess Experiment N o . 2, percent V A 1 := 0.8  V A 2 := 1.3  VSystem := 2.0  For influent mixed sludge phosphorus concentration, the error was taken as the greater o f the primary and secondary precisions. EMassIn = P S EMassIn = 4 . 9 The total phosphorus mass error around A T A D 1 was calculated as the sum o f the influent mixed sludge phosphorus concentration precision, the A T A D 1 phosphorus concentration precision, and the liquid balance percent error around A T A D 1. E M a s s A l = EMassIn +- P A 1 +• V A 1 E M a s s A l =9.6 The total phosphorus mass error around A T A D 2 was calculated as the sum o f the A T A D 1 phosphorus concentration precision, the A T A D 2 phosphorus concentration precision, and the liquid balance percent error around A T A D 2. E M a s s A 2 := P A 1 + P A 2 + V A 2 EMassA2=8.8  The total phosphorus mass error around the system was calculated as the sum o f the influent mixed sludge phosphorus concentration precision, the A T A D 2 nitrogen concentration precision, and the liquid balance percent error around the system. EMassSystem = EMassIn + P A 2 + VSystem EMassSystem = 10.5  222  APPENDIX 3  TEMPERATURE INCREASE from  MECHANICAL MIXING in W A T E R FILLED PILOT S C A L E A T A D S  223  A P P E N D I X 3: Sample Calculations for prediction o f system temperature increase due to mechanical mixing. Predicted difference between ambient air temperature and liquid temperature in the pilot scale A T A D reactors (Delta T) was calculated for power inputs o f 273 and 532 Watt respectively, using the slopes and intercepts calculated by linear regression, and the measured average airflows for each experiment. B o t h a predicted Delta T and the 95% confidence range are shown in the "Predictions o f Temperature Rise During Experiments d Mechanical Heat." In "Maximum Average Temperature Predicted by Interpolation", predicted reactor temperatures are compared with actual average daily maximum temperatures. A sample calculation follows, based on data for the O E 2 experiment, A T A D 1. W: =- i ^ _  C : = K - 273 K  1000 51 : = - 0 . 0 0 0 5 7 7 C - ^ ^  mL : = - ^ L 1000  Unit conversions  Slope o f airflow/Delta T curve: low energy mech heat experiments  mL 52 : = - 0 . 0 0 0 7 5 2 - 0 ^ ^  Slope o f airflow/Delta T curve: high energy mech heat experiments  mL 11 :=29.992-C  Intercept of airflow/Delta T curve: low energy mech heat experiments  12 : = 50.476-C  Intercept o f airflow/Delta T curve: high energy mech heat experiments  A =4613  Average airflow during O E l experiment, A T A D 1 min  P I :=273-W  Power input during low energy mech. heat experiments  P2:=532 W  Power input during high energy mech. heat experiments  P=280W  Power input for O E 2 experiment, A T A D 1  T:=16C  Average ambient temperature during O E 2 experiment  Calculation o f predicted difference between A T A D 1 operating temperature and ambient air temperature DTP1  ( S l - A ) i II  D T P 1 =27.3 - C  Predicted Delta T above ambient for 273 watts input  D T P 2 : = ( S 2 A ) + I2 DTP2=47«C  Predicted Delta T above ambient for 532 watts input  224  Calculation o f Delta T above ambient for operating input power DT:=  DTP2-DTP1  - ( P - P O + DTPl  P2-P1 DT=28-C Calculation o f predicted maximum operating temperature for given operating input power and airflow Tmax:=T + DT Tmax = 44 *C  .  225  ,  1  s0  1 o OH  (N  CO VO  in  CN  VO ON  «o  <—1  rH  rH  ON VO  m  CN  m  r- o  ON  o  m i > c o o N r ~ - O N O ' H r o > m T t - H - « n r - r - c o T f i i i i f i i o t N N M N  03 (L>  «  cn O N N o icn —i OrON  la  O 60  0 > n © « n « n © « n O ON ON 00 CO' vo' O N CO' K  T3  H  S  " 60  <*> C/5 <U  IH  <n O  H  O  ©  O  © «n  cn  O  CN  H  C N C N - — I — I C N C N C N C N  I °  « n « n > n o © i n © > n r~-  r ~ vo r n m  od ro m  60  l-l rS  4  >  «  ,  °  ,  °  0  4  >  C  I  >  0  >H><;Z;;Z;>H;>,>H>H  03 C/5  CJ 60  0>  >  IH  O  1  O  O N ON  rS  O  o O  O  J  O 60  o  O 00 >n <n  ©  CN  W-)  ON  *T3  VO  o «n •n O 00 ro ON ON T m cn T  VO  o m o o «n co r-' oo' ON vd CO CN i—i cn  Tf  CN i—I 00 oo cn m CN cn «n  cn cn CN  ON  o oo' 1—1  N 00 C00 CN cn o  cn  O N O N O N O N ^ S S S r H r H r H r H ^ O V O V O V  _  O  P4  £  rHcNcn'^r>nvot~~oo  226  CN TT ca  \p  rH  o Tf Tf  in  CN  ON ON  cu PN  O  o o  \P CSS  5*  O  coi  1*1  •CS  Tf  CN  rH  M  1  ca Sales  ro m  o  CN  m  CN Tf  Tf  Tf Tf  o rH o o  5  00  in oOoN rON ©  ©  ON rH -H  o o ©  rin rH  o o o  IH CD  Ov © • CN  ON  c^ •K*  R ca cj  (3  r-  wo  CN  ON ON ON  o ro o 00 ON  Tf 1  ON  0)  ON  00  00  ca  O  Tf  CN 00  CD  CN  ON ON  1-H  I  o o  CO  CN  vq  VH  R  VO  ON  00  in o  f  r-  r- ro  ON CO  P  m •  O  rH  m  o* © cj •»-» cj  ©  Ov in  VO  00  ©  •  vo wo  <D  OH  H rH  o  Tf Tf  .a  00  vd  i  oo  CO f ~ o VO  m ON  Tf  CM  00  c»  CO vo in  p  rH  rH  r~- in **!  00  CN © 1 CN  VO  f  •  t- roH o 00 o r- o  o t> W 2 ro o o .CJ  W  CN m r-' vd1 CO  CO  Tf  in  O  Tf  O  vd  cj  in  VO CO CN m  vo  ro ro CN o mo mo  cj  CN  tCN -~ o  CN -H  ©  H  oo ON m ro in rH  in  CN  ON  ON  © d  CD >H  IH  CD  I cu  ca  rt CD  to  p  w  5 rt  P  2  CN  d  CN  &  S  cG „  00  ca  &O rt  vo  oo o  CD  cd  ON  CN  Tf  ca  ca  CJ  T3  ca  _Q  <2_&  CJ  227  CO rH  l-S  CD VH  ca P  CD  5* P  S rt  O  co  g T3  i-j  * i  a §l CO rO  Ql  3  60  O  60  t-- cn I  H  1  t  •a'  CN CN  in m io in  OV  OH  "3 f  1  r- CN o oo o v d vd <  O  ^  M  TS  8*  CD  TS  H  O  Tf  CN © m  m  TJ-  00  CN  CN  Os  © r-'  U  a 0  f  r-' r-' v d m cn cn cn  60 v d  TJ 4>  TS  c/3  ca  •n in m vo in v d v d in  TS T f  Tf  rj-  ^  fi s  CQ 0)  rd  60  TS CN 60 v d  O  rr'  -  •n in in in  13 0  TJ"  TP  m  f- TJ- rj- 0 0 Ov O © OV rf in m rf  CN  CN  i—i  r- t-  00  I—1  60  TS  r-' cn cn cn cn  rO  1 c/f  O  so 60 v d I  in CN oo CN CN CN CN  r»'  o  rH  M  TJ  T3  fi  •c  TS  r- oo r- cn  60 v d T J CN  ov CN  Os VO  CN  •n  ov CN  T3  CN  fi  60  TS  i-H  CN  o 60 Os CN TS  CN CN  00  o in cn  2  CN CN  CN CN  I—J  Os OV CN  O ©  in  cn  Os CN  vo  m  ^ ™  ^  Os  0  0  CN  4> <->  TS  <u T3 fi  CN —I  _  WQ  IZ3  o o o o  CN  CN  W  0L 228  WQ w a pq  o Q Q  Q  o 1) 60  60 ""  ,  60 CD  O  Tt-  rH  CO liO  m  2 *'  CO  60 O  rH rH  VO  VO  vo in  rm  Tf Tf  Tf Tf  o 60 i n  o m  t T3  •a .  O  *-l  ON  Tf  Tf  60 co  •a  co in  ra"  Tf  co  rS  ^ CD  n§ «>  2 " 2P-a  60  1-1  rS  ^3  60  Tf Tf  53  0)  r8  0  O  rj rH Tf  6  U <L> -O  U 60  CO  IS -9  VO  §  60  CO  VO  CO  rH Tf  CD  T3  CQ  CD  f  vo f 60 CO CO  £-  CD  60  Tf  -3  60  O  at o  rH  60 CN  00  O  rH  nd  M  r2  T3  *T3 CD  t>  CD  CD  rH 00 60 CO CN  ts  ON 00 60 CN CN CD  »  T3  ^ u  r2  r- in CO CO  JH  60  60  IS3 I5  O  O VO 00 CN CN  DH  O  00  co  ro  VO  CO  CN CD  CN  o o  cN  co W  Q 229  0  APPENDIX 4  AERATION TESTING  230  Appendix 4 : Aeration Testing  Purpose To measure oxygen transfer rate and oxygen transfer efficiency of the pilot scale ATAD Turborator aerators.  Method  The test method used was generally as outlined in A Standard for the Measurement of Oxygen Transfer in Clean Water. ASCE 1984. Clean tap water was used, and the total dissolved solids concentration probably did not exceed the maximum recommended 1500 mg/L even with multiple testing. Water temperature was measured before and after each test and the results averaged to determine the Standard Oxygen Transfer Rate (SOTR). Cobalt chloride was used as the catalyst. Sodium sulphite was added in approximately 200 percent excess. Water depth was 400 mm.  Some modifications were necessary due to the small size of the pilot scale ATAD tanks. Only two dissolved oxygen probes were used instead of the recommended four, and it was not possible to mount them 600 mmfromthe tank walls since the tanks were only 500 mm in diameter. D.O. measurements were taken every 10 seconds, and in some cases this resulted in less than the 21 determination points recommended by the Standard. Air flow was measured using an in line rotometer flow meter complete with control valve. Aerator revolutions per minute were measured using a reflected light tachometer. The aerators were run at two speed settings: 70 percent and 100 percent of maximum  231  Results The detailed test results are summarized in Table A4-1 and Figures A4-1 and A4-2. A corrected version of the program available in the Standard was used to analyze the results.  Conclusions 1. The oxygen transfer rate with no air input to the aerators at rotational speed settings higher than 70 percent is significantly greater than zero, probably due to mixing turbulence and subsequent entrainment at the hquid surface.  2. At a given rotational speed, SOTR decreases with an increase in air flow.  3. At a given air flow, SOTR increases with an increase in rotational speed.  4. Oxygen transfer efficiency decreases with an increase in airflow at a given rotational speed.  5. Oxygen transfer efficiency increases with an increase in rotational speed at a given airflow.  232  TABLE A4-1 : Detailed Aeration Test Results  ATAD 1 70 % speed setting kLa20 Airflow  (mL/min) (l/s) 3728 0.0060 0.0058 7660 0.0093 0.0093 15382 0.0164 0.0129 23314 0.0180 0.0181  ATAD 1 100 % speed setting kLa20 Airflow  (mL/min) (l/s) 3728 0.0088 0.0090 7660 0.0131 0.0131 15382 0.0203 0.0201 23314 0.0250 0.0254  919 r/min C*20 SOTR  (mg/L) 9.01 9.00 9.03 8.99 9.04 9.23 9.15 9.11  (mg/L) 193 187 302 301 533 428 593 593  1190 r/min C*20 SOTR  (mg/L) 9.11 9.06 9.05 8.98 9.19 9.19 9.07 8.96  (mg/L) 287 292 425 422 670 664 818 821  233  Transfer Efficiency  (mg/L) 190  Oxygen flow (mg02 /min) 1042  302  2141  19.4  480  4298  15.3  593  6517  12.5  Average SOTR  Transfer Efficiency  (mgT.) 290  Oxygen flow (mg02 /rnin) 1042  424  2141  27.2  667  4298  21.3  819  6517  17.3  Average SOTR  (%) 25.1  (%) 38.2  Table A4-1: Detailed Aeration Results (cont.) ATAD 2 70 % speed setting kLa20 Airflow  (mL/min) (1/s) 0* 0.0009 0.0009 3728 0.0073 0.0070 7660 0.0111 0.0105 15382 0.0156 0.0146 23314 0.0197 0.0193  ATAD 2 100 % speed setting kLa20 Airflow  (mL/min) (1/s) 0* 0:0029 0.0034 3728 0.0120 0.0115 7660 0.0165 0.0163 15382 0.0200 0.0197 23314 0.0229 0.0220  965 r/min C*20 SOTR  (mg/L) 8.99 8.90 9.07 9.08 9.08 9.10 9.14 9.25 9.25 9.18  (mg/L) 29 28 238 229 364 345 513 487 657 939  1234 r/min C*20 SOTR  (mg/L) 9.27 9.31 9.06 9.05 9.02 8.99 9.08 9.08 9.14 9.18  (mg/L) 97 114 390 371 535 527 654 644 754 726  Transfer Efficiency  (mg/L) 28  Oxygen flow (mg02 /min) N/A  233  1042  30.7  355  2141  22.7  500  4298  16.0  648  6517  13.7  Average SOTR  Transfer Efficiency  (mg/L) 105  Oxygen flow (mg02 /min) N/A  382  1042  50.3  531  2141  34.0  649  4298  20.7  740  6517  15.6  Average SOTR  (%) N/A  (%) N/A  Measurements for 0 airflow were done with aerator impellors switched and are shown for interest only.  234  Figure A 4 - 1 A i r f l o w vs. S O T R 900 i  1  o  1 5000  ]  0  - n  :  r—  1 10000  1 15000  1 20000  1 25000  Airflow (mL/min)  •—  —•—  ATAD 1 920 r/min  ATAD 1 1190 r/min  1  =i  ATAD 2 965 r/min  —o  ATAD 2 1235 r/min  Figure A 4 - 2 Airflow vs. Oxygen Transfer Efficiency 60.0  1  0.0 4 0  1  1  5000  10000  1  15000  20000  1 25000  Airflow (mL/min)  •—  ATAD 1 920 r/min  —•—  ATAD 1 1190 r/min  235  °  ATAD 2 965 r/min  —-°  ATAD 2 1235 r/min  APPENDIX 5 CALCULATION OF PHOSPHORUS RELEASE DUE TO SAMPLE ACIDIFICATION  236  A P P E N D I X 5 - C A L C U L A T I O N OF PHOSPHORUS R E L E A S E D U E TO SAMPLE ACIDIFICATION Sample Calculation Based upon O E 2 Experiment values, A T A D 2 VSIn := 17357-^8  Influent M i x e d Sludge Volatile Solids  TPIn = 473-5^-  Influent M i x e d Sludge Total Phosphorus  liter  liter TPperVSIn := ™5.-100 VSIn  TPperVSIn =2 73  Phosphorus contained in Influent M i x e d Sludge Solids, percent  Estimated M a x i m u m P released from solids remaining in centrifuged supernatant, assuming worst case phosphorus content o f digested sludge solids as same as mixed influent sludge solids, ie: TSP/TP=1. TSPperTP := 1  VS := 1265-^*L  Estimated maximum V S in supernatant samples  Phyd :=0.8  Fraction o f polyphosphates hydrolyzed by acidification  liter  Preleased : =  T P  P 100  e r V S m  . VS-TSPperTP-Phyd  Preleased =28  liter  A T A D 2 Sludge Characteristics ATAD2TP :=442-^i-  Total phosphorus in A T A D 1 Sludge  ATAD2TDP :=225-™^-  Dissolved phosphorus in A T A D 1 Sludge  liter  liter  ATAD2TSP : = ATAD2TP - ATAD2TDP ATAD2TSP =217  t  mg  Suspended phosphorus in A T A D 1 Sludge  liter  237  A T A D 2 Sludge Characteristics (adjusted for maximum P release), Iteration 1 TDP : = ATAD2TDP - Preleased TDP = 197-- ^liter m  TSP :=ATAD2TP-TDP TSP =245--^liter TSPperTP :=  TSP — ATAD2TP  TSPperTP =0.55 First Iteration o f estimate o f P released Preleased : = JfPiEX^. VS-TSPperTP-Phyd 100 Preleased = 15 • - i liter m  A T A D 2 Sludge characteristics (adjusted for maximum P release), Iteration 2 TDP : = ATAD2TDP - Preleased TDP =210-- ^ liter m  TSP = ATAD2TP - TDP TSP =232--*^liter TSPperTP :=  TSP ATAD2TP  TSPperTP =0.53 Second Iteration o f estimate o f P released Preleased : =  T P  P 100  e r V S I n  . VS-TSPperTP-Phyd  Preleased = 14*-™^liter  238  A T A D 1 Sludge characteristics (adjusted for maximum P release), Iteration 3  TDP : = ATAD2TDP-Preleased . TDP =211liter TSP . = ATAD2TP - TDP TSP =231*^liter TSPperTP : = TSP ATAD2TP TSPperTP =0.52 Third Iteration o f estimate of P released  Preleased := P T P  e r V S m  100  . S-TSPperTP-Phyd V  me Preleased = 14 •—— liter Calculation o f maximum expected error in dissolved P measurements due to hydrolyzing o f suspended phosphorus in supernatant samples. EDP:=  /ATAD2TDP-TDP^ I ATAD2TDP  EDP =6.4  100  Calculation o f maximum expected range in suspended P in Volatile Suspended Solids  ATAD2VS := 12331 mg liter ATAD2VSS := 11846-^  liter  M i n ;  /ATAD2TSP \ \ ATAD2VS /  1 0 0  Estimate from Appendix 6 calculations  Min =1.76  Max :=[ 1-100 \ATAD2VSS/  Max = 1.95  Predated := ATAD2TSP \ \ATAD2VSS/  Predicted = 1.83  T S ?  239  A p p e n d i x 5 : Calculation of Phosphorus Release due to Sample Acidification  Supernatant Solids Content Tare Sample Vol. (ml) (g) 40.0135 26.0 Total 39.6745 29.5 Total 43.2336 31.5 Total 39.9209 28.5 Sup 79.7985 47.5 Sup 81.2319 46.0 Sup 50.0 77.6096 Diss 81.5278 50.0 Diss  Dry  Fired  (g) 40.4840 40.2532 43.8086 39.9883 79.9148 81.3430 77.6638 81.5748  (g) 40.0777 39.7056 43.3085 39.9349 79.8219 81.2540 77.6294 81.5436  VS TS NVS (mg/L) (mg/L) (mg/L) 18096 2469 15627 19617 1054 18563 18254 2378 15876 491 1874 2365 2448 493 1956 480 1935 2415 688 1084 396 624 940 316  Total Sample Averages Total Dissolved Suspended 1012 17644 18656 TS 16689 656 16033 VS 356 . 1611 1967 NVS 0.65 0.91 0.89 VS/TS Supernatant Sample Averages Total Dissolved Suspended 1012 1398 2410 TS 656 1265 1921 VS 356 132 488 NVS 0.91 0.80 0.65 VS/TS  Probable E r r o r i n Suspended P due to A c i d Hydrolyzation of Solid P  Calculation of probable error in dissolved phosphorous measurements due to hydrolyzation of organic polyphosphates in solids to P04 Assume suspended VS = 1265 mg/L. This is a worst case, since this sludge was centrifuged at speed 1/3 of that used during experiments. On the other hand, this was thickened primary digested sludge only, but it is felt that the results are still representative.  240  From experiment results, most of the phosphorus in the influent sludge was in the particulate form, over 97 %. Therefore, the worst case assumption is that the phosphorous content of the solids in the digester supernatant is equivalent the phosphorous content of the influent solids. (TSP/TP =1) Assuming 80% of polyphosphates hydrolyzed Maximum additional P releasedfromsolids = (%TP/VS)/100*1265 mg/L*(TSP/TP)*0.8 TVS = Total Volatile Solids TP = Total Phosphorus TDP = Total Dissolved Phosphorus TSP = Total Suspended Phosphorus  Influent Mixed Sludge TVS Experiment  OEl OE2 OD OS  (mg/L) 17294 17357 18398 16558  TP  TP/TVS  (mg/L) 309 473 438 432  (%) 1.79 2.73 2.38 2.61  Measured values of P in ATADs Exp. ATAD 1 TP TDP TSP (mg/L) (mg/L) (mg/L) 296 152 144 OEl 236 451 215 OE2 269 141 410 OD 183 228 411 OS  241  Maximum Additional P released from solids (mg/L) 28 24 26  ATAD 2 TSP/TP TP TDP TSP TSP/TP (mg/L) (mg/L) (mg/L) 0.44 185 145 0.49 330 217 0.49 442 225 0.52 94 0.23 0.34 405 311 233 0.54 0.55 430 197  Values of P in ATADs adjusted for estimated P releasefromsuspended solids Iteration 1 ATAD 2 ATAD 1 Exp. TSP/TP TP TDP TSP TSP/TP TDP TP TSP (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 0.55 442 197.42 244.58 264 0.58 187 451 OE2 0.29 405 286.91 118.09 0.40 245 165 410 OD 0.60 430 170.6 259.4 0.62 157 254 411 OS ATAD 2 Iteration 2 TP P from Exp. SS (mg/L) (mg/L) 442 15 OE2 405 7 OD 430 16 OS  TDP  TSP  TSP/TP  (mg/L) 210 304 181  (mg/L) 232 101 249  0.53 0.25 0.58  TDP  TSP  TSP/TP  (mg/L) 211 305 182  (mg/L) 231 100 248  0.52 0.25 0.58  TP  TDP  TSP  TSP/TP  (mg/L) 442 405 430  (mg/L) 211 305 182  (mg/L) 231 100 248  0.52 0.25 0.58  ATAD 2 Iteration 3 P from TP Exp. SS (mg/L) (mg/L) 14 442 OE2 405 6 OD 430 15 OS ATAD 2 Iteration 4 Pfrom Exp. SS (mg/L) OE2 14 6 OD 15 OS  242  ATAD 1 Iteration 2 P from Exp. SS (mg/L) OE2 16 10 OD 16 OS  ATAD 1 Iteration 3 P from Exp. SS (mg/L) 15 OE2 OD 9 16 OS  ATAD 1 Iteration 4 Pfrom Exp. SS (mg/L) 15 OE2 9 OD 16 OS  TP  TDP  TSP  TSP/TP  (mg/L) 451 410 4.11  (mg/L) 199 259 167  (mg/L) 252 151 244  0.56 0.37 0.59  TP  TDP  TSP  TSP/TP  (mg/L) 451 410 411  (mgT.) 200 260 167  (mg/L) 251 150 244  0.56 0.37 0.59  TP  TDP  TSP  TSP/TP  (mg/L) 451 410 411  (mg/L) 200 260 167  (mg/L) 251 150 244  0.56 0.37 0.59  Estimated TSP in VS for Thickened Secondary Sludge Exp. OE1 OE2 OD OS  VS (mg/L) 18476 18505 17938 19440  TP (mgT.) 706 805 748 759  TDP (mg/L) 13.1 9.6 15.2 5.0  243  TSP TSP/VS (mg/L) 693 3.75 4.30 795 4.09 733 3.88 754  Therefore, the maximum error expected due to acidification of the centrifuged supernatant would be Exp.  OE2 OD OS  Exp.  OEl OE2 OD OS  Exp.  OEl OE2 OD OS  Error  ATAD 1 ATAD 2 (mg/L) (mg/L) 15 14 9 6 15 16  Expected Error in TDP from acidification (%) ATAD 1 ATAD 2 ATAD 1 ATAD 2 (mg/L) (mg/L) 225 7.15 6.42 215 311 3.27 1.91 269 8.55 7.74 183 197  Measured TDP  TSP /VS (%) Measured VS Estimated VSS ATAD 1 ATAD 2 ATAD 1 ATAD 2 ATAD ATAD 2 (mg/L) (mg/L) 1 (mg/L) (mg/L) 1.01 1.14 12770 13683 12268 14243 11846 1.69 1.76 13998 12331 13448 0.94 0.72 13057 14358 12544 14945 12966 1.63 1.73 14024 13496 13473  % TSP/calc VSS % calc TSP/VSS ATAD 1 ATAD 2 ATAD 1 ATAD 2 (%) (%) (%) (%) 1.05 1.18 1.75 1.83 1.87 1.95 0.98 0.75 1.04 0.80 1.80 1.91 1.69 1.81  244  APPENDIX 6  RECYCLE CALCULATIONS  245  APPENDIX 6 - RECYCLE CALCULATIONS Example Calculation based upon Nitrogen Values. Calculation for C O D and Phosphorus are similar. "High" Condition " L o w " Condition OEl ATAD 2  OD A T A D 2  Volatile Solids VSh:= 12331-^liter  VS1 :=T3057- ^liter m  Total Kjeldahl Nitrogen TKNh : = 970-™^ liter  TKN1 := 1034-™^liter  Dissolved Kjeldahl Nitrogen TDKNh : = 454-mg liter  TDKN1 :=723-^liter  Estimated Suspended Volatile Solids FDVS :=0.0393  Fraction Dissolved Volatile Solids VSSH :=VSh(l - FDVS)  VSSL :=VS1(1 - FDVS)  VSSH = 11846 •- ^liter  VSSL = 12544  m  liter  Suspended T K N TSKNh :=TKNh - TDKNh  TSKN1: = TKN1 - TDKN1  TSKNh =516--^liter  TSKN1 = 311-^1liter  T K N per mg Suspended Solids TSKNh TKNperVSSh : = VSSH  TKNperVSSl  TKNperVSSh =0.044  TKNperVSSl =0.025  TSKN1 VSSL  Dissolved T K N per mg Suspended Solids DTKNperVSSh  TDKNh VSSH  DTKNperVSSh =0.038  DTKNperVSSl :=  TDKN1 VSSL  DTKNperVSSl =0:058  246  Estimate of Nitrogen Range in Typical ATAD Supernatant Recycle Estimated volatile suspended solids in supernatant return RSI :=750--™^-  5 percent of digester influent solids returned to plant  RSh := 3000 i^L  20 percent of digester influent solids returned to plant  liter  liter  Estimated VSS in ATAD 2 supernatant, flail scale VSSful := 15000-™^liter  Based on 5 percent suspended solids return to plant: TKNh : = RSlTKNperVSSh  TKN1 : = RSlTKNperVSSl  TKNh=33-^iliter  TKNl = 1 9 - ^ i liter  Based on 20 percent suspended solids return to plant: TKNh :=RSh- TKNperVSSh  TKN1 : = RSh-TKNperVSSl  TKNh = 1 3 1 - - ^ ' liter  TKN1=74--^liter  Dissolved TKN DTKNh := VSSful-DTKNperVSSh DTKNh=575-^iliter  DTKN1 := VSSfulDTKNperVSSl DTKN1 = 8 6 5 - i ^ . liter  "  247  APPENDIX 6 - RECYCLE CALCULATIONS Example of T y p i c a l F i e l d Solids Concentrations  30000 25000 40 15000 20000  ATAD TS In ATAD VS In ATAD VS Destruction ATAD VS Out ATAD TS Out  mg/L mg/L % mg/L mg/L  Estimated Filtrate Solids Range  Total Solids 5 percent of digester influent solids in return flow 20 percent of digester influent solids in return flow Volatile Solids 5 percent of digester influent solids in return flow 20 percent of digester influent solids in return flow  1000 mg/L 4000 mg/L 750 mg/L 3000 mg/L  Results of Supernatant Solids Measurements  Volatile Solids Fractions ATAD Sludge Sample Supernatant Total Dissolved in Supernatant  16689 mg/L 1921 mg/L 656 mg/L  Fraction Suspended VS in Supernatant Fraction Dissolved VS in Supernatant  0.0758 0.0393  Estimate of Average Suspended Volatile Solids i n A T A D Sludge during experiments  Experiment  Estimated VSS (mg/L) (mg/L)  OEl OD OS OE2  12770 13057 13496 12331  VS  12268 12544 12966 11846 248  APPENDIX 6 - RECYCLE CALCULATIONS Estimate  of COB7VSS during  experiments:  TCOD = Total COD SCOD = Soluble COD Experiment  PCOD = Particulate COD  TCOD  SCOD  (mg/L)  (mg/L)  17941 20543 18301  1639 714 623  OD OS OE2  ATAD 2  SCOD/ PCOD/ VSS VSS (mg/mg) (mg/mg) 1.30 1.53 1.49  0.13 0.06 0.05  Estimate of C O D range i n typical A T A D Supernatant Recycle  5 percent solids return with supernatant ATAD Low Air ATAD High Air  PCOD 975 1119  SCOD 1960 789  TCOD 2935 1908  20 percent solids return with supernatant  ATAD Low Air ATAD High Air  PCOD 3899 4477  SCOD 1960 789  Supernatant COD Recycle Range  TCOD 5859 5266 1908  249  to  5859  APPENDIX 6 - R E C Y C L E C A L C U L A T I O N S  Estimate of Nitrogen/VSS during experiments: ATAD 2 T K N = Total Kjeldahl Nitrogen  T P K N = Total Particulate  T D K N = Total Dissolved Kjeldahl Nitrogen Experiment  TKN  TDKN  Kjeldahl Nitrogen  TDKN/  TPKN/  VSS  VSS  (mg/L)  (mg/L)  (mg/mg)  (mg/mg)  OE1  891  497  0.03  0.04  OD  1034  723  0.02  0.06  OS  1047  511  0.04  0.04  OE2  970  454  0.04  0.04  Estimate of Nitrogen range in typical ATAD Supernatant Recycle 5 percent solids return with supernatant PTKN  DTKN  TKN  A T A D Low Air  19  865  883  A T A D High Air  33  575  608  PTKN  DTKN  TKN  A T A D Low Air  74  865  939  A T A D High Air  131  575  706  20 percent solids return with supernatant  Supernatant T K N Recycle Range  608  to  939  Supernatant T D K N Recycle Range  575  to  865  250  APPENDIX 6 - RECYCLE CALCULATIONS  Estimate of Phosphorus/VSS during experiments: ATAD 2  TP = Total Phosphorus TDP = Total Dissolved Phosphorus TP  TDP  (mg/L) 330 405 430 442  (mg/L) 185 311 197 225  Experiment  OEl OD OS OE2  TPP = Total Particulate Phosphorus TPP/ TDP/ VSS VSS (mg/mg) (mg/mg) 0.01 0.02 0.02 0.01 0.02 0.02 0.02 0.02  Estimate of Phosphorus range in typical ATAD Supernatant Recycle  5 percent solids return with supernatant TPP TDP 372 6 ATAD Low Air 285 14 ATAD High Air  TP 378 299  20 percent solids return with supernatant  ATAD Low Air ATAD High Air  TPP 22 55  TDP 372 285  Supernatant TP Recycle Range Supernatant TDP Recycle Range  TP 394 340 299 285  251  to to  394 372  APPENDIX 6 - RECYCLE CALCULATIONS Influent Sewage Flow Recycle Flow  100 L 1 L  ATAD Digestion Recycle Effect on Plant Influent New plant influent Parameter Influent Recycle Range High High Low Cone. Low (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 1000 4000 228 257 220 SS 553 514 1908 5859 500 COD 29 26 608 939 20 TKN 16 14 575 865 8 TDKN 0 0 0 10 0 NOx 8 7 299 394 4 TP 7 6 285 372 3 TDP  Mesophilic Anaerobic Digestion Recycle Effect on Plant Influent New plant influent Parameter Influent Recycle Range High Low Cone. Low High (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 219 295 7772 220 143 SS 540 507 4565 500 1230 COD 30 24 441 1080 20 TKN 8 253 853 10 16 NH3 6 190 5 99 4 TP 4 4 63 143 3 TDP  Load Change Low High (%) (%) 5 18 4 12 30 47 108 72 75 95  99 124  Load Change Low High (%) (%) 1 35 2 9 22 54 32 107 21  48  Mesophilic Aerobic Sludge Digestion Recycle Effect on Plant Influent New plant influent Load Change Parameter Influent Recycle Range High Low High Low High Cone. Low (mg/L) (mg/L) (mg/L) (%) (mg/L) (mgT.) (%) 218 332 0 52 11500 46 220 SS 0 16 576 8140 497 228 500 COD 24 1 20 20 400 10 20 TKN 6 5 60 4 241 19 4 TP 4 1 21 3 64 3 3 TDP  252  APPENDIX 7  ORP and DO TRACE PATTERNS  253  1/8ra) nopBjraaouo3 naSAxQ, paAjossia o 00 0 E6/SZ/I :  00:0 E6/W/1  00:0 E6/EZ/I  00-0  Willi  00 0 E6/IZ/I :  00^0 E6/0Z/I  00 0 £6/61/1 :  00^0 £6/81/1  f  o a  00:0 £6/Z.I/l  cct  Q 00 0 E6/9I/I :  00 0 E6/SI/I :  00 0 E6/W/I :  00-0 E6/EI/1  00=0 E6/ZI/I  o o  o o  o o  o o  repnajod noponpa^ nopupixo  254  o. o C S  o o C O  00^0 £6/11/1  (WO E6/SZ/I  00=0  £6/vZ/l  00-0 £6/£Z/l  00-0 £6/33/1  00=0  £6/lZ/\  00-0 £6/03/1  00=0 £6/61/1  00=0 £6/81/1 i |  s s  00"0E6/Z.I/I •  00=0 £6/91/1  r  00^0 £6/51/1  (WO £ 6 / H / I  00-0 £ 6 / £ l / T  00 0 £6/31/1 :  i  co o o  i i i  00:0 £6/11/1 o o  o o  O  o  (\va) iBnn3)0<j uoponps^ uopEpixQ  255  O  o  o o CO  £  q/8ra) uopBiju33uo3 uaSAxo paAiossifj 00^0 £6/6/£  00-0 £6/8/£  00 0 £61 U£ :  00=0 £6/9/£  00=0 £6/5/£ O  P  00=0 £6lvl£  00-0 £6/£/£  00=0 £6/Z/£  00 0 £6/t/£ :  f1 Q  to  00=0 £6/2ZIZ  00-0 £6ILZ/Z  00=0 £6/9Z/Z  (WO £6/SZ/Z  00-0 £6/n/Z  00 0 £6/£Z/Z :  o ©  o o  CS  o o  o o ro  TT  (Ata) pjpnajod noponpa^ nopBpixo  256  o o  o o  VO  00^0 £6I6I£  00=0 £6/8/£  00-0 £6/L/£  00-0 £6/9/£  00-0 £6/9/£  00-0 £6/v/£  00-0 £6/£/£  00-0 £6/Z/£  00-0 £6/l/£  OO'O £6/2Z/Z  00 0 £6/LZ/Z :  00-0 £6/93/3  00 0 £6/53/3 :  00-0 £6/vZ/Z  00-0 £6/£Z/Z © o  O  o  o o  o o  O O  m  <N  O O  O O  (\m) nnjuajoj noponpa^ uoqBpreo  257  <n  o o  NO  <N  O  oo  vo  00^0 £6/81/^  00=0 £6/Ll/v  00-0 £6/9l/v  00-0 £6/SI/fr  00:0 £6/vl/v  00 0 £6/£l/P :  8  I  00 0 £6/Z\/v H :  I  00:0£6/ll/fr  S 0 Q  00^0 £6/0I/t>  00=0 £6/6/P  00^0 £6/8/t>  00 0 £6/L/v :  00-0 £6/9/P  00 0 £6/9/v :  © o CN  O ©  o o  o o  C S  o ©  cn  (\xa) repnajod noponps^ uopepixQ.  258  © o  q/Sm) noijBJjn3ono3 uaSAxo paAjossiQ 00  VO  1  1  1  00-0 £6/81/^  / /  / t \>  00-0 Z6/LI/V o  o  j t  00-0  \ 'i f ?  £6/9Vv  o  o  00-0 Z6/91/V o  o  \ i  00-0  £6/vl/v  00-0  £6/£l/v  o  o  o  o  s  !  00 0 £6/Zl/v  p  :  o  c  o  00:0£6/II/fr  <  I i 1J 1 »  S  Q  I \\ l r f t I7 (  [  00-0 £6/0I/t>  1> °  00=0 £6/6/*  '( , 1  i i~ £  •  °  [t 1\  00-0 £6/8/t> oo 00-0£6/L/v oo  —  00^0 £6/9/f  ,_r_^_-,_ . s  o  o 00=0 £6/S/fr  o Ifl  o O (Ain)  o  o  o  o VS  o O  iBijn3jO(j noponpa^ a o p c p i x Q  259  V>  .  1/8ui) noijBJ}U3oao3  usgAxo paAjossia 00^0 £6/81/5 000 E6/Z.I/S :  00=0 £6/91/5  J2 o  00=0 £6/91/9  CD o  & o  00"-0 £6M/5  O  Q  00=0 £6/£\/9 CO  §  00-0 £611119 J3  u  !  00=0 £6/11/5 H  o CQ  o  I  8*  00=0 £6/01/5 S  o  OtTO £6/6/5  a> Xl o  cd  O  P  Q  00=0 £6/8/5  CJ  t to  00=0 £6/L/9 000 £6/9/5 :  00^0 £6/5/5 OtTO £6/tV5  00=0 £6/£/5 o  o o  o  o in  o o  —  o u-i  (Ain) repaajoj uoponpatf uopcpixQ  260  o o  cs  o cs  o o  1/8ra) uoijBimaouoQ uagAxQ, paAiossifj ts o  vo  TJ-  — —n —n - i — i — ' 1  —1  1  r  1  r - —1  1  -i  1  00=0 £6/81/5  (WO £6/Z,I/S  1 ....  00=0 £6/91/5  _  j  '* 1  00=0 £6/51/5  h {  r1 /  00:0 £6/W/5  I \,  1  \  v\ t/ i.  O  00-0 £6/£l/5  (  i { y ^  O  *i (] \  00-0 £6/31/5  I  O  V  S  It -if-  00=0 £6/11/5 P O  f  J  f  t{  tWO £6/01/5  )  VS i F •f-r-  r  O J  • • " ti  00=0 £6/6/5 •  t  /  i1  00:0 £6/8/5  \\  o 00-0 £6/Z./5  U  00:0 £6/9/5  o  o•  00=0 £6/5/5  o•  D  00^0 £6/t>/5  o• o m  O  o o  o >n  o  o wi  o o  (A ) iBpnajoj noponpa^ uopupreo ra  261  I ^—' <D  o  vt i  © o  i  00=0 £6/£/S  « Q  

Cite

Citation Scheme:

        

Citations by CSL (citeproc-js)

Usage Statistics

Share

Embed

Customize your widget with the following options, then copy and paste the code below into the HTML of your page to embed this item in your website.
                        
                            <div id="ubcOpenCollectionsWidgetDisplay">
                            <script id="ubcOpenCollectionsWidget"
                            src="{[{embed.src}]}"
                            data-item="{[{embed.item}]}"
                            data-collection="{[{embed.collection}]}"
                            data-metadata="{[{embed.showMetadata}]}"
                            data-width="{[{embed.width}]}"
                            async >
                            </script>
                            </div>
                        
                    
IIIF logo Our image viewer uses the IIIF 2.0 standard. To load this item in other compatible viewers, use this url:
http://iiif.library.ubc.ca/presentation/dsp.831.1-0050409/manifest

Comment

Related Items