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

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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 p resen t ing th is thesis in partial fu l f i lment o f the r e q u i r e m e n t s fo r an advanced d e g r e e at t h e Univers i ty o f Brit ish C o l u m b i a , I agree tha t t h e Library shall m a k e i t f reely available f o r re ference and study. I fu r ther agree that permiss ion f o r ex tens ive c o p y i n g of this thesis f o r scholar ly pu rposes may be g r a n t e d by t h e head o f m y d e p a r t m e n t o r by his o r her representat ives. It is u n d e r s t o o d that c o p y i n g o r p u b l i c a t i o n o f th is thesis f o r f inancial gain shall n o t b e a l l o w e d w i t h o u t m y w r i t t e n permiss ion . D e p a r t m e n t o f - C w ' V / j ^rt&UsyiJ?<7 s~js? The Univers i ty o f Brit ish C o l u m b i a Vancouver , Canada Date /\U/>. DE-6 (2/88) ABSTRACT Return flows from sludge 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 AT AD) 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 the first digester 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 4 Effect of Supernatant Recycling on Sewage Treatment Plant Design 4 Biological Phosphorus Removal 8 Handling Bio-P Waste Activated Sludge 13 Chapter Three Autothermal Thennophitic Aerobic Digestion 19 Technology Development 19 Operating Conditions 29 ATAD Supernatant Quality 43 Chapter Four Experiment Design 51 Objectives 51 Apparatus 51 Experimental Methods 65 Sampling and Sample Preservation 68 Laboratory Analysis and Discussion of Method Error 72 Chapter Five Results and Discussion 88 Operating Conditions 88 Three Aeration States 106 Supernatant Quality 130 Full Scale Implications of Experimental Results 152 Chapter Six Conclusions and Recommendations 157 Conclusions 157 Recommendations 158 Bibliography 160 Appendix 1 Data 169 Appendix 2 Balance Calculations and Balance Errors 212 i v Appendix 3 Temperature Increase from Mechanical Mixing in Water Filled Pilot Scale ATADs 223 Appendix 4 Aeration Testing 230 Appendix 5 Calculation of Phosphorus Release Due to Sample Acidification 236 Appendix 6 Recycle Calculations 245 Appendix 7 ORP and DO Trace Patterns 253 v LIST OF TABLES TABLE TITLE OF TABLE PAGE NO. 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 48 9 Supernatant Solids Check 76 10 Maximum Expected Errors in Dissolved P from Sample Acidification 76 11 Standard Recovery 78 12 Pilot Scale ATAD Temperatures 89 13 Actual Average Daily Maximum Temperature Compared to Predicted Maximum Temperature 93 14 Volume Balance Summary 95 15 Solids Retention Times 96 16 Average Influent Mixed Sludge Solids Concentrations 98 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 23 Average Oxygen Supplied/VS load 108 24 ATAD Discharge Gas and Air Supply Quality - Percent by Volume 110 25 ATAD Discharge Gas and Air Supply Quality - Moles of Three Constituent Gases 110 26 Oxygen Transfer Efficiency 111 27 Alkalinity 127 28 ATAD pH 129 29 Total Chemical Oxygen Demand and Percent COD Reduction 130 30 Soluble Chemical Oxygen Demand 132 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 149 39 Estimated Effect of ATAD Supernatant Recycle On Influent Flow Concentrations and Loads 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) 21 4 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) 34 10 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) 40 13 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 84 28 Average Precision for C02, N2, and 0 2 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 104 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 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 125 VS Load: ATAD 1, OS Experiment ix 45 Total Chemical Oxygen Demand 131 46 Soluble Chemical Oxygen Demand 133 47 OD Experiment ATAD Volatile Fatty Acid Concentration 135 48 Influent Sludge Nitrogen Concentration 138 49 ATAD NOx Concentrations 143 50 Influent Phosphorus Concentrations 146 x A C K N O W L E D G M E N T S I would like to thank the following people and organizations for their help: B . C . Science Council , the Natural Sciences and Engineering Research Council , and Reid Crowther and Partners L t d . for their financial support. My thesis advisor, Don Mavinic , for his moral support and technical input. My thesis reviewers, Bi l l Oldham, and Les Nemeth for their technical input and presentation suggestions. Susan Harper, 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. Fred 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. Br ian W i n g , for cooking supper and being there after long hard days. T o m and 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 before final stabilization and disposal, they are fiirther processed 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 before final dewatering and disposal. Dewatering processes can decrease sludge Uquid content to 70 percent. When a sludge is thickened or dewatered, the liquid portion whichis removed from the 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 before final disposal. One type of wastewater treatment process, biological phosphorus removal (Bio-P), produces liquid effluent low in phosphorus by concentrating phosphorus in the solids fraction of the biological sludge. Phosphorus is then removed from the 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 soUd fraction. 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. Sludge from a 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. The first subsection 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 obtained from the 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 a final sludge 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 to five percent 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 vacuum filtration would range from 1.3 to 2.7 percent. Recent measurements at Toronto's Main treatment plant estimated the recycle flows from all sources as two percent of plant influent flow (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) Chemical Oxygen Demand 228 - 8140 Suspended Solids 46- 11500 Total Kjeldahl Nitrogen 10 - 400 Total Phosphorus 19 - 241 Total Dissolved Phosphorus 2.5 - 64 (a)pH range 5.9-7.7 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 Parameter(a) Range of Plant Averages (mg/L) COD 1230 - 4565 VFA 250-322 TS I475.4545 SS 143-2205 TVS 814- 2930 vss 118-1660 TKN 306-1144 NH3-N 253 - 853 Total P04-P 63 - 143 (a)pH range 7.0-7.8 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 recycle from mesophilic aerobic digestion of from 0 to 52 percent for SS and from 0 to 16 percent for COD. For anaerobic digestion, the impact would be an increase in SS load of from 1 to 35 percent, and an increase in COD load from 2 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 loading from the recycle stream ranged between 36 to 55 percent of the influent stream load, and that the BOD loading from the 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 flows from anaerobic digestion, heat treatment and sludge dewatering. Quahtative effects on plant operation resulting from increased 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 of from 1 to 20 percent. For anaerobic digestion, the impact would be a load increase in TKN of from 29 to 54 percent, and, for NH3, from 32 to 107 percent. 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 resulting from the 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 Men+2Pn03n+i (Jardin and PopeL 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 ranges from 2 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 sludge from a Bio-P pilot plant could be attributed to poly-P. In biomass from a 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 removed from the 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 expelled from the 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 competition from other 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) l l 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 removal from the Uquid train of the sewage treatment plant is accompUshed by wasting activated sludge containing stored poly-P from the 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 PRIMARY CLARIFIER WASTE S L U D G E L I M E A E R A T I O N DIRECT R E C Y C L E S T R I P P E R SUPERNATANT SECONDARY! CLARIFIER E F F L U E N T STRIPPER S T R I P P E R F E E D m WASTE ' S L U D G E 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 for farther treatment. 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 recycled from anaerobic 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 completely fix the 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 phosphorus fixation include absorption, and biological fixation by 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 of fixation and the German experience, phosphorus feedback from anaerobic sludge digestion can still be high. Neodbala (1993) observed a 75 to 85 percent release of P from Bio-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 sludge from a 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 m3 ATAD digesters. Their 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: Loll (1984) later corrected this figure to 3.5 - 4.0, including heat from mechanical 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: Reported values of G range from 1.00 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 A°C = 3.5(A g COD) (2.1) (2.2) 20 0 . 5 0 g- 0 . 4 0 -o c 0 . 3 0 o </> c o o 0 . 2 0 o DC o = 0.10 o o a> ref 4 0 5 0 _ 0 _ T e m p e r a t u r e , C 70 8 0 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 of tiiermophilic organisms 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 itself from highly 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 losses from a typical autoheated thermopliilic aerobic system. GAS INPUT (AIR) FEED _ SLUDGE MIXING HEAT INPUT BIOLOGICAL HEAT PRODUCTION SENSIBLE AND LATENT WATER VAPOUR HEAT LOSS WITH DISCHARGE GAS HEAT LOSS TO SURROUNDINGS HEAT LOSS IN DIGESTED SLUDGE 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 came from the influent sludge flow, 55.1 percent came from biological heat production, and 27.3 percent came from mechanical heat input. Booth and Tramonti (1983), using a similar system but supplying pure oxygen rather than air, found that 24 percent of heat input came from the pump, and the rest from the heat of reaction. Heat losses from the 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 loss from the pure oxygen gas flow. Jewell and Kabrick (1980) using aspirating type aerators, estimated that 60 percent of heat lost from the 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 DRAIN FOR ' DIGESTED SLUDGE T 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 m3 tanks acMeving operating temperatures of 44.5 °C (Smith et al. 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 self-aspirating 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 m3 pilot plant 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 m3 digester (Booth and Tramonti, 1983). Subsequent tests with air aeration 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 Norway from 1983-84, 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 m3 pure oxygen plant for 3 years. There are 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 Lady smith, 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 then rises with 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, from the 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. co co > o O UJ oc < cc LU CL LU r Q. 40 30 20 10 70 60 50 40 30 20 10 0 9 8 7 6 ^ I N I r L U E N T y . . E F F L U E N T — o — o -O — . — o —o • L o o~~ ' - a — • 1 / REACTC )RII , : / • / / _^ y ' '• / - n — * V r / ! • • A n I : / • \ / '/ \/ '/ U H 1 '/ •/ / / AIR \WSL ~~— • — • '-^^ • - = " * — • — « — — X • • — — « — -: 1 1 ~ o „ — O — . • J • * » 1 TEFFLI * INFLUENT r-o_+_o— JENT — o — o _ — o — D — o — D —C, i — o — o — —n —o D — — o — — a — o 12 15 TIME (d) FIGURE 7 - Gemmingen Temperature Curves (EPA, 1990) In Figure 8, temperature curves for the Eichbactal plant taken from Schwinning 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 0 0 5D -6 A A * A A A 0 3 4D 3 3a 20 1D 13 11 1 3 HOLT- CS/16/930 * R e a c t o r 1 A. R e a c t o r 2 17 2 1 1 3 2 3 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/m3. Kelly (1990) recommends 250 W/m3, based upon minimum mixing energy requirements quoted in ASCE and A WW A 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 (°C) (°C) (W/m3) Canada Banff© 26-33 44-51 114-157 Ladysmith(a) 32-56 40-63 135-200 Salmon Arm(a) 39-66 40-66 200 Whistler^ ) 80-250 Germany EllwangenC0) 35-43 48-50 83 Fassberg(c) 40-45 50-70 117 Gemmingen(c) 30-50 50-60 109 IsenbuttaKc) 40-55 45-60 Nettetal-Viersen(c) 38 58 Rheinhausen(d) 42 60 Vilsbihurg(c) 60 69 (a) Kelly et al. (1993), Temperature measured once daily. Measured applied power. (b) Schwinning et aL 1993 (c) Deeny et al. (1985) (d) Deeny et al. (1985) Arithmetic mean of measurements taken during 14 weeks. (e) Kelly (1991) Design applied power ® Schuster (1994). For period from Oct./93 to Nov./94. When operating three digesters in series, temperature in ATAD 3 ranges from 53 to 56 °C. 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 rates from 2.6 to 13.5 kg VS/(m3d). Loll (1984) recommended that full scale plants be 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 be from 5 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. 3 4 TABLE 4 Full Scale ATAD Solids Design Values Location Feed Sludge Solids SRT vss Loading Reduction TS . VS (%) (%) (kg VS/m3-d) (d) (%) Canada Banff(d) 2.6 2.2 2.8 7.1 31 Gibsons(a) 4.1 17 4.8 38 Ladysmith(a) 5.4 5-10 20 38 Salmon Arm(a) 4.6 20 6.1 34 Germany Backnang(c) 12.1 3.3 48 Fassberg(e) 4.4 3.7 38 GeinmingenO5) 5.0 3.0 5.0 6.0 25-40 IsenbuttalCb) 4.0 3.1 2.3 Kirchburg(c) 8.3 4.5 43-66 Nettetal-ViersenO3) 5.5 3.6 7.0 Romersburg(c) 1L7 3.4 41 VilsbiburgO) 3.5 2.8 2.8 (a) 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) (d) Schuster (1994) For period from Oct./93 to Nov./94. (e) Schwinning et al., 1993 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 02/(dkg VSS), with a minimum of 35 just under 400 g 02/(dkg VSS) occurring shortly after feeding, and a minimum of about 100 g 02/(dkg VSS) occurring just before feeding. CO cn > < a o cn > o < z o < cc a w LU d 500 400 300 200 100 0 -05 r t JUN 07-JUN 09-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 2 required to oxidize the carbon contained in the substrate can be estimated in several ways. One such estimate is 1.42 kg 02/kg VS destroyed, (EPA, 1990) based upon the equation C5H7N02 + 502 => 5C02 + 2H20 + NH3 + energy. (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 C5H7N02+ 702 => 5C02 + 3H20 +N03"+IT+ + energy, (3.2) which requires 1.98 kg 02/kg VS destroyed (Matsch and Dmevich, 1977). Booth and Tramonti (1983) found that 2.33 kg 02/kg VS destroyed was required, and Trim and McGlashan (1984) 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 ' 12 16 20 T i m e | h ] Time course of the oxygen uptake rate (OUR) during cultivation of aerobic thermophiles in sewage sludge at 65°C, 0.5 w m airflow, 1500 m i n " ' and pH 7. Phase 1, inactivation of non-therrriophilic microorganisms; phase 2, lag phase of the thermophiles; phase 3. exponential growth of the thermo-philes; 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 E A R T H Y H U M U S H U M U S A M M O N I C A L S W E E T I S H A C I D P U N G E N T S H A R P - P U N G E N T ( N A U S E A T I N G ) ( I R R I T A T I N G ) o < ? o UJ > £ M E A S U R A B L E F R E E O X Y G E N C O N V E N T I O N A L A E R O B I C . CHGEST10N •200 100 UJ S o . a. z 2 -100 o r> £ -200 z -300 i— < Q x -400 o -500. O F O P E R A T I O N • F O R * T H E R M O P H I L I C [ A E R O B I C D I G E S T I O N A E R O B I C D I G E S T I O N F R E E O X Y G E N N O T M E A S U R A B L E P R E F E R R E D R A N G E . F A C I L I T A T E D I G E S T I O N ( F E R M E N T A T I O N " A N D A E R O B I C R E S P I R A T I O N ) J . L_ R E D U C T I O N N O X R E D U C T I O N T O H 2 0 • T O N 2 + H 2 0 S O + R E D U C T I O N T O H 2 S + H 2 0 O R G A N I C R E D U C T I O N ( F E R M E N T A T I O N A C I D . P R O D U C T I O N ) O B L I G A T E A N A E R O B I C D I G E S T I O N C O 2 . R E D U C T I O N FIGURE , T O - C H 4 + H 2 0 . 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 Source Feed ATAD 1 ATAD 2 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 Full Scale ATAD Alkalinity and pH Location Influent Alkalinity pH (mg/L) ATAD 1 AlltahTiity pH (mg/L) ATAD 2 Alkalinity pH (mg/L) Banff© Ladysmith(a) Gibsons(a) Salmon Arm(a) 4.8-6.8 7.2-8.6 4.6-5.7 139-1060 4.8-5.9 360-1040 5.0-6.5 5.7-7.9 8.0-645 4.6-7.3 980-1730 6.8-9.1 720-1820 6.8-8.6 6.6-8.3 274-3160 N/A 600-1389 7.7-9.1 785-1980 7.0-8.6 (a)Kelly, 1990 ©Schuster, 1994 When operating three digesters in series, pH in ATAD 3 ranges from 7.0 to 8.5. 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 2 + nutrients => C02 + NH3 + C5N7N02+ other end products (3.3) C5H7N02 + 502 => 5C02 + 2 H20 + NH3 + energy (3.4) 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. NH3 + H20 <=> NH4+ OFT (3.5) 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 stripped from solution. 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 C02 as a carbon source. The overall reaction can be described as (Metcalf and Eddy, 1991): NH3++ 1.8302 + 1.98HC03 => 0.021C5H7NO2 + 0.098NO3" + 1.041H2O + 1.88H2C03 (3.6) 43 This reaction theoretically consumes about 4.3 mg 0 2 and 8.64 mg HCO3" per mg of NH3 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: N03" + I.O8CH3OH + H+ => 0.065C5H7NO2 + 0.047N2 + 0.76CO2 + 2.44 H20 (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 NH3 then to NO3; also, at the point of the oxidation rate change, there is a slight disturbance in the slope of the ORP curve (point B, Figure 14). 1 0 - r : — : 1 9 -' -3 • " f 1 — : r r 1 1 1 1 1 0 100 200 300 400 — - O R P avg Elapsed Time (min) a N03 dORP/dt D O * T K N . - 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 NH3 (22.4 percent of TKN) in the Haltwhistle ATAD at 2.53 percent 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 (days) Influent Concentrations Effluent Concentrations (mg/L) (mg/L) VS NFL( NO^  VS NFL, NO^  3 2 19430 106 7.7 13200 279 28 22400 61 28 20000 267 40 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 Volatile Fatty Acids Concentration Range (mg/L) Acetic 53-790 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 15 from Chu 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 , - 5 0 -CL CC -100 -O - 1 5 0 -- 2 0 0 -- 2 5 0 --300 -30 o a E 10.0 15.0 Time (h ) B . 0 * 0.0 5.0 10.0 15.0 Time ( h ) 20.0 25.0 A c e t a t e P rop iona te — I s o b u t y r a t e 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 that from nitrite, 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) The first and last experiments (OE1 and OE2) were done under this condition, with higher air rates being applied during OE2. 2. Oxygen deprived. (OD) The second experiment was run under this condition. 3. Oxygen satisfied. (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 sewage from the student residences. Raw sewage is pumped from the municipal sewer system to continually mixed storage tanks which are periodically dosed with sodium bicarbonate. During these experiments, raw sewage was pumped from the storage tanks to the primary tMckening process, shown in Figure 16. The primary thickening system consisted of: • R a w Sewage Pump: Moyno SP34401, 0.56 kW 1/60/110 DC motor with variable speed controller. • Primary Clarifier: 540 L, equipped with a rotating bottom rake and supernatant overflow weir • Primary Sludge Pump: Moyno SP33101, 0.56 kW, 1/60/110V DC motor with variable speed controller. • Gravity Thickener: 200 L, operating volume 125 L, equipped with a rotating bottom rake and supernatant overflow weir • Exhaust Blower: Dayton Model 2C782 • Thickened Primary Sludge Pump: Moyno SP33101, 0.56 kW, 1/60/110V DC motor with variable speed controller. • Primary Sludge Dosing Tank: 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/min from the storage tanks to the primary clarifier. Primary sludge was removed periodically from the 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 pumped from the 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 wasted from the 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 supernatant from mixed sludge thickeners ranging from 60-100 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 wasted from both 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 >-Ct. < Q UJ o LU _J O < CO CO O f->-< Q UJ , -Z O O Q 9 O Z> < UJ —1 O CO CO I- < I I I I I I I I I I I or LU o LU m < cn o ca fi cu X I o CO fi CD - t J w CO cm cl • p H n a O 5*: z o z F= CO < o X ! E-H cu GO XI 1—1 CO ti Pi O o CU CO 55 To reduce the number of variables in the experiment, no polymers were used to help thicken the secondary sludge. The amount of time between wasting from the aerobic zone and feeding to the ATAD digesters was minimized to prevent the secondary sludge from becoming 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 h t x H ^ i 33a m s AuvaNOoas Q3N3)HOII-LL 3 o a m s Q3N3»OIHi Oi P4 PH o cd cu XJ o CO cu -4-> w CO Q % cu i - H cd o co • P o i—i •rH PH 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. Rotating fittings were screwed onto the top of the aerator shafts to allow connection of air hoses. Compressed air was first regulated to 10 to 15 kPa, then passed through Cole-Parmer flow meters before entering the shaft of the aerator. Setting the reading on the flow meters 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 and fittings exposed 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 pumped from ATAD 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 resulting from evaporation. 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 UBC 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 were finally chosen. 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 in-line 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 of free oxygen 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 2 in the measurement medium, as well as to dissolved oxygen. Further testing showed that, over time, the probes would gradually desensitize to the presence of C 0 2 in the ATAD reactors. This characteristic partially accounted for the minimal deviation 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 deviation from actual 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 C0 2 . After 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 2 but with decreased sensitivity, and 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 DO 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 DO concentrations greater than 1 mg/L DO, the Oxyguard D O probes were accurate to within 0.5 mg/L DO as measured during the OS and OE2 experiments by comparison with YSI DO probe readings. Due to the interference by carbon dioxide, DO 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 DO 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 ATADs during the experiments. The three states were defined by a combination of ORP and DO 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 1 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) oa NO c s o _ ^ 2 <u .* u P< <u Q a 5 O 5 ON J3 ^—^ o o o o o o o o o o o o o I I I I am (T/Sui) oa NO T f <N O T J V en •J3 CS CO fl WD O 5 o o o o o o o o o o o o o I I I I drao (T/SUI) oa NO r j - ( S O o 5 ON NO a H O O O O O o o o o o o o o cmo (T/Sui) oa 9 t Z 0 -a fi S3 o 1 I o o o o o o o o o o o o o ( S —i c n T f I I I I am (T/Sui) oa NO • * O -a C us ••a « a 5 O E o o o o o o o o o o o o o I I I I dHO (q/Sui) oa NO -* <N O 09 K I u H W s o 1 o o o o o o o o o o o o o I I I I am 67 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 sludge from each ATAD were collected once per day during the feeding procedure. Samples were taken from the outlet pipe of the transfer pump after at least 10 L of sludge had been pumped. Thickened primary sludge samples were collected from a 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 collected from a 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 was first blended 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 withdrawn from a portion while it was being mixed with a magnetic stirring rod. The 10 mL aliquot was placed in a 250 mL flask and the volume made up with distilled water. A 60 mL sample of the well-mixed 1/25 diluted sludge was then frozen at -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 glass fiber filters. 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 to filter and it was often 5 hours before enough filtrate was collected for analysis. Unfiltered ATAD supernatant was kept at 4 °C during the long filtering process. Filtering ATAD supernatant through Whatman 934AH filters (approximately 1 micron) did not noticeably remove sample turbidity. Difficulty in filtering ATAD 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 up to 100 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 P04/NOx tubes, and subsequent PMA doses had to be 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 ATAD 1 Solids Coefficient of Variation • TS • NVS • TS M vs • NVS Secondary Sludge Solids Coefficient of Variation ATAD 2 Solids Coefficient of Variation I 111 II 8 8 0 0 O 8 TS VS NVS • TS m vs • NVS 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 aliquot from each 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 H2S04 + 134 g K2SO4 made up to 1 liter with distilled water) were also placed in the micro-Kjeldahl flask. 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 taken from the 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 if 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 ATAD 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 Supernatant Solids Check Solids Type Sludge Solids Supernatant Solids Total Solids Suspended Total Solids Dissolved Suspended Solids Solids Solids (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) Total (TS) 18656 17644 2410 1012 1398 Volatile (VS) 16686 16033 1921 656 1265 Non Volatile 1967 1611 488 356 132 VS/TS 0.89 0.91 0.80 0.65 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 Experiment ATAD 1 ATAD 2 (%) (%) OD -3.3 -1.9 OS -8.6 -7.7 OE2 -7.2 -6.4 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 10 • TKN • TDKN • TP • TDP ATAD 1 Sludge Nutrients Coefficient of Variation 10 8 m H o m m TKN • TDKN • TP • TDP Secondary Sludge Nutrients Coefficient of Variation ITI y iss • TKN • TDKN • TP • TDP ATAD 2 Sludge Nutrients Coefficient of Variation 10 8 6 4 2 0 • TKN • TDKN • TP Hi TDP 8 p o O CN 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 Standard Recovery Supernatant TKN TP TDKN TDP Type Avg. Std. Avg. Std. Avg. Std. Avg. Std. Dev. Dev. Dev. Dev. Standards 101.1 4.8 98.7 4.7 Primary 98.3 4.9(a) 97.7 2.2 100.7 2.4 95.3 0.4 Secondary 94.6 10.4(a) 98.8 9.4(a) 100.4 N/A(b) 103.7 N/A(°) ATAD 1 101.6 2.5 101.9 5.6(a) 100.6 3.1 97.8 5.4(a) ATAD 2 101.4 6.l(a) 100.7 6.1(a) 100.8 16.7(a) 98.1 6.6(a) (a) Outside the range of corresponding measurement precision discussed earlier. (b) Onfy one measurement made, therefore standard deviation cannot be computed. 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 either from measurement accuracy or from acidification. 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. 7 8 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 of 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 OE1 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 No . 10-115-01-1-Z, which has a range of 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 OS and O E 2 experiments. Figure 24 illustrates the precision in the phosphate analysis technique for each experiment. Phosphate Coefficient of Variation 12 1 0 P = Primary Sludge 8 6 S = Secondary Sludge 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 that freezing was 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) recommends freezing as 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, neither freezing nor 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 P = Primary Sludge S = Secondary Sludge A l = A T A D 1 Effluent Sludge A 2 = A T A D 2 Effluent Sludge 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 No . 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. NOx Coefficient of Variation 12 i OEl OD OS O E 2 81 14 12 10 8 6 4 2 0 Ammonia Coefficient of Variation 8 in O 8 • i • A2 P = Primary Sludge S = Secondary Sludge A l = A T A D 1 Effluent Sludge A2 = A T A D 2 Effluent Sludge 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 (COD) 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 OS and OE2 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 mm diameter bylOO mm long tubes, but using only 2.0 m L of 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 of 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, (r2 =0.999 and an average standard error on the COD determination of 10 mg/L) 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 taken from the 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 2 may have escaped to atmosphere during subsequent mixing and contact with air containing low levels of C02. 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 values from the 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 aeration from mixing 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 ATAD 1 Discharge Gas Measurement Precision 14 12 10 8 6 4 2 0 OD OS • C02 • 02 • N2 OE2 ATAD 2 Discharge Gas Measurement Precision 14 12 10 8 6 4 2 0 E OD OS OE2 • C02 • 02 111 N2 F I G U R E 28 - Average Precision for CO2, N 2 and 0 2 Discharge Gas Measurements 87 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 ranged from 54.0 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 Experiment ATAD 1 Temperature (°C) ATAD 2 Temperature (°C) Minimum Average Maximum Minimum Average Maximum 0E1 34.6 47.0 55.1 54.0 57.3 63.2 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 Mean 35.5 47.0 55.0 55.2 59.3 63.1 SDO*) 0.98 1.06 1.08 1.01 1.44 0.88 (a)Standard Deviation 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 OEl Temperature Profile 1/11/93 0:00 1/13/93 0:00 1/15/93 0:00 1/17/93 0:00 1/19/93 0:00 1/21/93 0:00 1/23/93 0:00 1/25/93 0:00 Date (mon/d/y) Time (h) OD Fouled Temperature Profile probe Power off, aerator stopped z l 2/23/93 0:00 2/25/93 0:00 2/27/93 0:00 3/1/93 0:00 3/3/93 0:00 3/5/93 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 4/9/93 0:00 4/11/93 0:00 4/13/93 0:00 4/15/93 0:00 4/17/93 0:00 Date (mon/d/y) Time (h) Data not recorded due to power failure a a 70 50 30 5/3/93 0:00 5/5/93 0:00 OE2 Temperature Profile Lower r/min, same airflow • < a o • < 1 ! ~ c^*H i 1 - ^ 1 * 1 1 S< 1 1 • V\ V\V\ H v\  v \  v \  v \  v \  y \ 5/7/93 0:00 5/9/93 0:00 5/11/93 0:00 5/13/93 0:00 5/15/93 0:00 Date (mon/d/y) Time (h) 5/17/93 0:00 A T A D 1 O A T A D 1 A T A D 2 • A T A D 2 Spot checks Spot checks Figure 29 - Pilot Scale Temperature Trace Patterns 90 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/m3 for the OS experiment and 3830 W/m3 for the OE2 experiment. Power density in ATAD 2 was about 5080 W/m3 for the OS experiment and 4660 W/m3 for the OE2 experiment. Therefore, the measured power draw in the installed units was about 15 times the highest recommended value of250 W/m3 (Kelly, 1990) in ATAD 1 and about 20 times that value in 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 temperature rise from 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 Airflow vs. Power Demand and the Difference Between Water and Ambient Temperature I ° § I I 6001 500 400 300 200 100 0 5000 10000 15000 Airflow (mLVmin) 20000 oc o - -• o 1 y o A LA - -50 45 40 35 & 6 0 H 25 20 15 a 10 5 0 25000 O 1190 r/min O 920 r/min Watts • 1190 r/min A. 920r/min Delta Watts Delta T 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 temperature rise was calculated, using input power and airflow as variables. An interpolation based on equilibrium temperature rises shown 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 Experiment ATAD 1 Temperatures ATAD 2 Temperatures 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 51.0 41 34-49 60.3 50 44-56 OE2 53.4 44 34-53 61.1 50 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) Experiment OE1 OD OS OE2 Primary Sludge 16.4 12.0 12.0 12.0 Secondary Sludge 8.3 13.0 13.0 13.0 System Feed 24.7 25.0 25.0 25.0 Sampling and Piping Loss 1.1 1.2 1.1 1.0 ATAD 2 Feed 23.6 23.7 24.0 23.8 Discharge Gas Vapour 0.5 <0.1 <0.1 0.4 Total ATAD 1 Discharge 25.2 24.9 25.2 25.2 Volume Balance -ATAD 1 +0.5 -0.1 +0.2 +0.2 ATAD 2 Feed 23.6 23.7 24.0 23.8 ATAD 2 Discharge 23.4 23.8 24.3 23.8 Discharge Gas Vapour 0.2 <0.1 <0.1 0.2 Total ATAD 2 Discharge 23.6 23.8 24.3 24.0 Volume Balance -ATAD 2 0.0 +0.1 +0.3 +0.2 Volume Balance -System +0.4 0.0 +0.5 +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 ATAD 1 ATAD 2 Operating Influent SRT Operating Influent SRT System Volume Volume Volume Volume SRT (L) (L) (d) (L) (L) (d) (d) OEl 73.5 24.7 3.0 72.5 23.6 3.1 6.1 OD 73.5 25.0 2.9 72.5 23.7 3.1 6.0 OS 73.0 25.0 2.9 72.0 24.0 3.0 5.9 OE2 74.0 25.0 3.0 73.0 23.8 3.1 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 00 30000 20000 10000 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 CJ e£ « op 3 M, "o oo 30000 20000 10000 0 2/22/93 2/24/93 2/26/93 2/28/93. 3/2/93 3/4/93 Date (mon/d/y) 3/6/93 8 o U a o 30000 20000 10000 0 OS Influent Mixed Sludge ^^ *,*-»»^ ,Xl"^ "'"^ ''"^ "'^ "'<>'"'<>'--^ -"-v-""j0r""'"V' 3/28/93 4/1/93 4/5/93 4/9/93 Date (mon/d/y) 4/13/93 4/17/93 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 oV 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 Exp. Primary Sludge Vol. TS VS VS frac-tion (L) (%) (%) (%) Secondary Sludge Vol. TS VS VS frac-tion (L) (%) (%) (%) Influent Mixed Sludge TS VS VS PS/SS frac- TS(C> tion (%) (%) (%) (g/g) OEl OD OS OE2 16.4 1.86 1.67 89.8 12.0 2.13 1.89 88.7 12.0 1.80 1.35 75.0 12.0 1.90 1.61 84.7 8.3 2.29 1.85 80.8 13.0 2.29 1.79 78.2 13.0 2.97 1.94 65.3 13.0 2.59 1.85 71.4 2.01 1.73 86.1 62/38 2.21 1.84 83.3 46/54 2.41 1.66 68.9 36/64 2.26 1.74 77.0 40/60 Mean SD(a> CVvT) 1.92 1.63 84.6 0.14 0.22 6.7 7.2 13.5 2.54 1.86 73.9 0.32 0.06 7.0 12.6 3.3 2.22 1.74 78.8 0.17 0.07 7.6 7.4 4.2 (a)Standard Deviation (^ Coefficient of Variance (c)Ratio of Primary Sludge to Secondary Sludge 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 volatile fraction. If the plant was not wasting enough secondary sludge to supply the digesters, a supplementary sludge source from another 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 volatile fraction than 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 varying from 36/64 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 Experiment ATAD 1 ATAD 2 System (kg VS/m3-d) (kg VS/m3-d) (kg VS/m3-d) OE1 5.8 4.6 3.4 OD 6.3 4.9 3.2 OS 5.7 4.7 2.9 OE2 5.9 4.6 3.0 Mean 5.9 4.7 3.1 SD(a> 0.3 0.1 0.2 CV©, % 5.1 2.1 7.1 ©Standard Deviation ©Coefficient of Variance 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 OEl Experiment OD Experiment OS Experiment OE2 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 -4.9 ±4.0 +17.8 ±3.5 -3.9 ±3.6 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 ATAD 1 ATAD 2 Total OEl 17.8 11.2 27.0 OD 19.2 12.3 28.9 OE2 20.0 11.7 30.1 100 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 30 20 H 10 b X - PILOT PLANT REF (188) • - F U L L SCALE REF (194) o - PILOT SCALE REF (178) A - F U L L SCALE REF (185) + - PILOT PLANT REF (208) • - PILOT PLANT REF (211) o - PILOT PLANT REF (192) • - F U L L SCALE REF (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 (Cdays) ATAD 1 (Cdays) System ( 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 the first reactor, 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 appears from the solids retention times and temperatures quoted in the reference that those results may have come from experiments with widely differing time-temperature products. This seems possible because Table 1 in that paper fists information 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 heat from the 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 1 ATAD 2 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 Mean 19300 14300 18350 12930 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. a 20000 •S 18000 !» 1* 160001 > § B 14000. g 12000 ° 10000 1 ATAD 1 VS Concentration 5 6 7 8 Experiment Day No. 10 11 12 a 20000 •3 ^ 18000 £ I £ 16000 ^ § a i4ooo g w 12000 ° 10000 ATAD 2 VS Concentration 4 6 8 Experiment Day No. -O- OE1 -A- OD OS 10 12 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 temperature rise was 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 input from the 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 feeding (h) Average SOUR (gO,/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 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 range from 100 to 400 g 02/g VSS-d (EPA, 1990). Most of the results shown in Table 23 fall within this range, except for the 3 hour result for OE2 in ATAD 1. Of course, Table 23 is based upon VS rather than VSS, 106 due to the ffltering difficulties 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 02/kg VS-d, and in ATAD 2 of about 111 to 546 g 02/kg VS-d. These calculated 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 Experiment ATAD 1 o2/ vsoo (kg/kg) ATAD 2 02/ VS© (kg/kg) OE1 2.66 0.60 OD 0.13 0.06 OS 0.27 0.03 OE2 2.12 0.57 (a) kg 0 2 supplied per kg VS load During some experiments, the VS concentration of the sludge fed to the ATADs varied from day to day. To keep the 02/VS ratio constant, the airflow was varied to match the estimated 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 450 400 350 -o 1 250 o 200 \ 150 100 50 { 0 0 4 6 8 Experiment Day No. 10 1.5 1.3 1.1 0.9 0.7 0.5 0.3 0.1 T - 0 . 1 -0.3 -0.5 12 T3 ca 0 1 3 -SP d -o- Airflow -O- VSLoad Airflow/VS Load F I G U R E 34 - Variation o f Airf low with V S Load - OS 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 N2, 20.9 percent 02, and less than 0.1 percent C02. (Ledbetter, 1972) Table 24 lists the average percent by volume of N2, 02, and C02 in the air supply (assumed same as laboratory air), ATAD 1 discharge gas, and ATAD 2 discharge gas. Generally, the percentage of C02 declined and the percentage of 0 2 increased from the OD experiment to the 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 Experiment Percent by Volume ATAD 1 ATAD 2 Air Supply CO?, o9 N ? , CO, o, N ? , 0,. N„. OD 13.6 6.7 79.7 8.6 12.2 79.2 20.6 79.4 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 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 Dischar ge Gas Air Supply Experiment ATAD 1 (moles/d) ATAD 2 (moles/d) ATAD 1 (moles/d) ATAD 2 (moles/d) C09 O, N 9 CO, 09 N9. O, N, 09 N9 OD OS OE2 2.51 1.24 14.69 2.49 4.85 26.81 3.36 52.57 223.71 0.45 0.64 4.16 0.17 0.43 2.16 1.35 10.27 44.87 3.8 14.64 7.04 27.09 54.81 224.83 I. 08 4.17 0.57 2.18 II. 06 45.38 110 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 off-gas 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 Experiment Oxygen Transfer Efficiency (%) ATAD 1 ATAD 2 OD 67 41 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 i l l 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 readings from ORP 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. Rapid rise in 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 1 1 2 q/8ni) nopBflU9ono3 USSAXQ paAjossirj 00:ZI E6/0Z/I 00=6 £6/0Z/I 00=9 £6/0271 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 o o o o o o CS o (Am) l e p n ^ o j u o p o n p a ^ - u o p B p r x o 113 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 00:£ £6/11/5 00=0 £6/11/5 — ' 1 00:iZ£6/0T/S 2 Q 00^ 81 £6/01/5 00:51 £6/01/5 00^1 £6/01/5 00:6 £6/01/5 O P o </-> o o o o o o (Am) i B p u a j O d u o p o n p a ^ - n o p B p i x o 114 I w T H w o R R o T J R & o < • i L < 00:3I £6/03/1 00=6 £6/03/1 00=9 £6/02/1 00:£ £6/03/1 — ' 00=0 £6/03/1 | f a 00'-I3 £6/61/1 TO Q 00:81 £6/61/1 00^1 £6/61/1 00^ 31 £6/61/1 00^ 6 £6/61/1 O • cd CN o O CN O o o 00 o o o CN (Am) nnjnajod uoponpa -^nopBpxxo 115 q/8ni) u o p B r m a o n c Q nsSAxQ PSAIOSSIQ o cs •> it 00:ZI £6/11/5 00:6 £6/11/5 00=9 £6/11/5 00=£ £6/11/5 O Q 00=0 £6/TT/5 g f I 00=IZ £6/01/5 2 rt Q 00=81 £6/01/5 3 ca cs 00:51 £6/01/5 00:n £6/01/5 00=6 £6/01/5 o o CS o o © 00 o SO o © cs (Am) nnjirajod uoponpa^-nopBpixo 116 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 varied from about 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 2 solubihty 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 resulting from mixing 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 o o o o o o o o o >n © u~> i n o «"i o u- i © r - i ^ - i i .—t o » <s c i m • t i i • i (Am) pniusjod noponpa^-uopnppio 120 the sludge accumulation. DO measurement decreases slowly over the remainder of the cycle, but never reaches zero due to the C02 sensitivity problem explained in 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 feed from ATAD 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 feed from ATAD 1. The length of the period varied from day to day, and was non-existent when the feed from ATAD 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 varied from day 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 5. ORP continues to rise, concurrent with a small change in the D O measurement, which begins to rise shghtly. 6. DO 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 7. and 8. Anomalies in the DO 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 DO pattern during the OS experiment. Values : A T A D 2, OD Experiment the O U R 122 1/Sva) uopBfln33u03 USSHXQ paAjossia o o t ^ v O v i T t - c o c S — < © 00^1 £6/6/* 00 : 6 £6/8/fr © o o o o o o o © o © © o o o o o C S * - < >-H C S C O T f I O V O I I I I I I (\m) n?pn3jo<i uoponpa -^uopcpTxo 123 q/gm) uopBijuaoncQ uaSAxo paAjossiQ oo r - NO u-i -<t m CN 1 — — 1 h 1 H 1— cn 1 . . . , .ft... ; CN | « o 00=31 £6/6/* 00=6 £6/6/* 00=9 £6/6/* 00=£ £6/6/* J4 00=0 £6/6/* | H I 1 00=13 £6/8/* a ca Q 00=81 £6/8/* 00=SI £6/8/* 00=31 £6/8/* 00=6 £6/8/* o <n o o o </-> o i n o o (Atu) n?pn3}0^  noponpa^-noptjpixo 124 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 2 effect noticed at the beginning of 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 • _ i 1 1 1 1 1-100 200 300 400 500 600 Time of Low ORP Values (ran) FIGURE 44 - Correlation Between Duration of Low ORP Values and Primary Sludge VS Load : ATAD 1, OS Experiment 300 250 200 3 150 100 50 125 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 sludge from ATAD 1, which is at a lower oxygenation state. The drop is lower than is expected from just 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 Experiment Alkalinity (mg/L as CaCO^) Primary Secondary A T A D 1 A T A D 1 A T A D 2 A T A D 2 Sludge Sludge Actual Expected Actual Expected OE1 550 400 1170 1040 1670 1700 OD 370 420 1650 1780 1790 2560 OS 570 460 1450 1010 2130 1670 OE2 440 530 1300 910 1960 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 expected from the 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, including frequent sampling 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 ranged from 6.0 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 0E1 . 7.7-8.3 7.8-8.4 OD 6.5-7.2 7.1-7.8 OS 7.4-7.6 7.7-7.9 OE2 7.7-8.0 7.8-8.0 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 02/kg VS was fairly constant during each experiment and was 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 Experiment Influent ATAD 1 COD ATAD 2 COD Overall COD COD Reduction COD Reduction COD Reduction (mg/L) (mg/L) (%) (mg/L) (%) (%) OEl 28330 19880 29.8 17610 11.4 37.8 . OD 29270 21630 26.1 17940 17.0 38.7 OS 29160 21190 N/A 20540 N/A N/A OE2 29470 21090 28.4 18300 13.2 37.9 130 Q O U cs 0 1 45000 35000 25000 150009-5000 OEl Experiment Total Chemical Oxygen Demand -a— 1/11/93 1/13/93 1/15/93 1/17/93 Date (mon/d/y) 1/19/93 1/21/93 1/23/93 Q O U CN o 45000 35000 25000' 15000' 5000 OD Experiment Total Chemical Oxygen Demand mm mm •! '•• . • • • ? t s o e 8 <> o 2/22/93 2/24/93 2/26/93 2/28/93 Date (mon/d/y) 3/2/93 3/4/93 3/6/93 Q O U cs 0 1 45000i 35000 25000i 15000 5000 3/31/93 OS Experiment Total Chemical Oxygen Demand T : • 1 1 M ! X .-\ W J i i * ? 9 6 ! ! O 4/3/93 4/6/93 4/9/93 Date (mon/d/y) 4/12/93 4/15/93 4/18/93 OE2 Experiment Total Chemical Oxygen Demand ~ 45000 ^ ° 35000 O * 25000 M 15000 ^ 5000 i II • 1 r • • • • 9 6 $ $ 8 o 9 i j i 5/3/93 5/5/93 5/7/93 5/9/93 5/11/93 Date (mon/d/y) 5/13/93 5/15/93 Influent COD * ATAD 1 ° ATAD2 FIGURE 45 - Total Chemical Oxygen Demand 131 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 Soluble Chemical Oxygen Demand influent ATAD 1 ATAD 2 Experiment SCOD SCOD/ SCOD SCOD/ SCOD SCOD/ TCOD TCOD TCOD (mg/L) (%) (mg/L) (%) (mg/L) (%) OD 160 0.5 1595 7.4 1640 9.1 OS 100 0.3 475 2.3 715 3.5 OE2 135 0.5 380 1.8 625 3.4 132 OD Experiment Soluble Chemical Oxygen Demand O .1 3500 3000 2500 2000 1500 1000 500 0 A A > ° ( 5 o 0 • o f! * , • • • • 2/22/93 2/24/93 2/26/93 2/28/93 Date (mon/d/y) 3/2/93 3/4/93 3/6/93 OS Experiment Soluble Chemical Oxygen Demand cs O o * cj : i o o O 9 ' C •> CJ • , — • « V _M—, 3/31/93 4/3/93 4/6/93 4/9/93 4/12/93 Date (mon/d/y) 4/15/93 4/18/93 OE2 Experiment Soluble Chemical Oxygen Demand O Q £ 6p A t s < ) c o n I I % % • i 5/3/93 5/5/93 5/7/93 5/9/93 5/11/93 Date (mon/d/y) 5/13/93 5/15/93 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 ranged from 36 to 66 mg/L and for proprionic acid from 23 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 PD 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. | 8 1 E 1200 1000 800 600 400 200 0 OD Experiment Volatile Fatty Acids ATAD 1 g vo Date (mon/d/y) Acetic Propionic I Iso-Butyric L~ZI Butyric A-Valeric ffl Iso-Valeric • Valeric OD Experiment Volatile Fatty Acids ATAD 2 a 450 400 350 300 250 200 150 100 50 0 g Acetic cn m g g g g in oo C5 ?1 ?5 ?1 g Date (mm/dd/yy) 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 (mg/L) ATAD 1 (mg/L) ATAD 2 (mg/L) OD 89 1078 416 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 supernatant from oxygen 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 I o 2000 <8 w 1500 500 0* 1/11/93 OE1 Experiment Influent Nitrogen ^ '—i rn u • 1 J - O Q- LJ L J • - U L Jr- • LJ LJ - X -1/13/93 1/15/93 1/17/93 1/19/93 Date (mon/d/y) 1/21/93 1/23/93 | ^ 2000 «g ^ 1500 § j 1000°" g ~ o 500 O D Experiment Influent Nitrogen 2/22/93 2/24/93 2/26/93 2/28/93 3/2/93 Date (mon/d/y) 3/4/93 3/6/93 § _ 2000 1 \ 1500 g JX 1000 2 I1 500 4/5/93 4/7/93 OS Experiment Influent Nitrogen • — — -0- —"^ • • • d — — • d X X — £ _ x X X — — x — — x > < x — — x — — x • 4/9/93 4/11/93 4/13/93 Date (mon/d/y) 4/15/93 4/17/93 OE2 Experiment Influent Nitrogen 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) • TKN o TDKN o NOx x NH3 FIGURE 48 - Influent Sludge Nitrogen Concentration 138 TABLE 32 Average IS fitrogen Concentrations in Influent Thickened Sludge Experiment Sludge Type TKN (mg/D (g/d) TDKN (mg/L) (g/d) NH3 (mg/L) (g/d) NOx (mg/L) (g/d) OEl Primary Secondary Mixed 565 9.25 1520 12.65 885 21.89 29 0.47 5 0.04 21 0.51 29 0.46 3 0.03 20 0.49 0.3 0.00 0.6 0.00 0.4 0.01 OD Primary Secondary Mixed 600 7.17 1715 22.27 1180 29.44 34 0.41 17 0.22 25 0.63 31 0.37 15 0.19 23 0.56 0.2 0.00 0.3 0.00 0.2 0.01 OS Primary Secondary Mixed 435 5.20 1570 20.39 1025 25.59 25 0.30 3 0.04 13 0.34 21 0.25 I 0.02 II 0.26 0.2 0.00 0,2 0.00 0.2 0.01 OE2 Primary Secondary Mixed 600 7.20 1580 20.52 1110 27.72 21 0.25 2 0.03 11 0.28 17 0.21 1 0.01 9 0.22 0.2 0.00 0.2 0.00 0.2 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 when first wasted 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 TABLE 33 Nitrogen Mass Balance Nitrogen Source Total Nitrogen (g/d) OE1 OD OS OE2 Thickened Primary Sludge 9.25 7.17 5.20 7.20 Thickened Secondary Sludge 12.65 22.27 20.39 20.52 Total influent Sludge 21.90 29.45 25.60 27.73 Sampling and Pipe Loss 0.92 1.25 1.09 1.06 ATAD 1 Sludge In 19.85 25.52 23.59 23.96 Discharge Gas N/M N/M 0.00 0.13 Total ATAD 1 Out 20.77 26.77 24.68 25.15 ATAD 1 Mass Balance (%) -5.2 -9.1 -3.6 -9.3 Expected Error (%) ±11.6 ±8.1 ±8.2 ±7.7 ATAD 2 In 19.85 25.52 23.59 23.96 ATAD 2 Out 21.01 24.61 25.47 23.37 Discharge Gas N/M N/M 0.00 0.13 Total ATAD 2 Out 21.01 24.61 25.47 23.50 ATAD 2 Mass Balance (%) +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 +3.8 -11.0 Expected Error (%) +10.9 ±7.2 ±9.2 ±7.7 N/M = Not Measured 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 2 content in the discharge gas from ATAD 1 during the OD experiment indicated that 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 14 from Peddie 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 2 levels in the discharge gas during that experiment do not 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. TABLE 34 ATAD Average Nitrogen Concentrations Experiment Digester TKN mg/L TDKN mg/L NH3 mg/L TDKN/TKN percent NOx mg/L OEl ATAD 1 ATAD 2 835 890 312 497 288 486 35 53 9.15 9.05 OD ATAD 1 ATAD 2 1075 1035 480 723 520 740 46 69 0.15 0.30 OS ATAD 1 ATAD 2 980 1045 324 511 293 479 29 45 0.95 0.65 OE2 ATAD 1 ATAD 2 995 970 300 454 262 435 25 44 10.40 9.70 As can be seen from Tables 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 8 2 16.00 12.00' 8.00 4.00 O E l Experiment Nitrates + Nitrites c> 0 , Y — o — O \ o <>.,.. '<V... r" o 6 -••V o o ' n 6 D — O-— ; — 6 — o- — 6 — — r i 1/11/93 1/13/93 1/15/93 ) 1/17/93 Date (mon/d/y) 1/19/93 1/21/93 1/23/93 OD Experiment Nitrates + Nitrites 2 S 16.00 12.00 8.00 4.00 0.00E 2/22/93 2/24/93 2/26/93 2/28/93 Date (mon/d/y) 3/2/93 3/4/93 3/6/93 8 z 2 I 16.00 12.00 8.00 4.00 0.00 OS Experiment Nitrates + Nitrites 4/5/93 4/7/93 4/9/93 4/11/93 4/13/93 Date (mon/d/y) 4/15/93 4/17/93 OE2 Experiment Nitrates + Nitrites 16.00 *! 1 2 0 0 f 4.00 0.00 5/3/93 A. ..,.\ <>"' > '^:r. ! •- ' n o , \ c -"••<>- k ° c 0 o \ " T o 1 O 0 ! j O I 5/5/93 5/7/93 5/9/93 5/11/93 Date (mon/d/y) Influent ATAD 1 5/13/93 5/15/93 ATAD 2 F I G U R E 49 - A T A D N O x Concentrations 143 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 wasted from the 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 sludge from the UCT process. For the first five days of the OD experiment, the proportion of waste secondary sludge feed to the ATADs was 30 percent from the trickling filter process and 70 percent from the UCT process. For the remainder of the OD experiment all secondary sludge was from the 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 was from the UCT process. During the OE2 experiment, waste secondary sludge was initially from both processes, but the amount of secondary sludge available from the trickling filter process dropped from 50 percent down to 15 percent from Day 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 trickling filter sludge use was discontinued. 145 OE1 Experiment Influent Phosphorus Concentrations 8 ^ 800 g Ou y • a D Q • o • • • M u u 200 0<^  1/11/93 1/13/93 1/15/93 1/17/93 1/19/93 Date (mon/d/y) 1/21/93 1/23/93 O D Experiment Influent Phosphorus Concentrations a 8 0 0 a 3 6 0 0 s g> 400 g-- 5 200 I T • — • • p - i - • 6— / \ — 6 — — o -<^>--. <v o ..A 2/22/93 2/24/93 2/26/93 2/28/93 3/2/93 3/4/93 Date (mon/d/y) 3/6/93 O S Experiment Influent Phosphorus Concentrations 8 8 0 0 « o. 600 3 1a> 400 & s 200 I 0 OH a — r—1 — n n LJ— V LJ i — — o — — 6 — o — — 6 — — o 6— — o 6— — o — — 6 — — o — 4/5/93 4/7/93 4/9/93 4/11/93 4/13/93 4/15/93 4/17/93 Date (mon/d/y) OE2 Experiment Influent Phosphorus Concentrations 5/5/93 5/7/93 5/9/93 Date (mon/d/y) 5/11/93 5/13/93 Total P Total Dissolved P 5/15/93 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. TABLE 35 Influent Mixed Sludge Phosphorus Concentrations Experiment Total Total Total Total P Dissolved Suspended Suspended P P P /Total P (mg/L) (mg/L) OEl 310 9.1 300 0.97 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 Total Phosphorus Mass Balance OEl Experiment OD Experiment OS Experiment OE2 Experiment Balance Actual Expected Actual Expected Actual Expected Actual Expected For: Error Error Error Error Error Error Error Error (%) (%) (%) (%) (%) (%) (%) (%) ATAD 1 -4.5 ±12.3 -6.9 ±8.9 -4.5 ±12.2 -5.4 ±8.0 ATAD 2 +10.6 ±8.9 -1.0 ±7.3 +5.8 ±8.8 -1.6 ±7.5 System +5.1 ±12.2 -7.8 ±8.0 +0.8 ±13.1 -6.9 ±8.7 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 1 ATAD 2 Experiment TP TDP TDP TP TDP TDP /TP /TP (mg/L) (mg/L) (%) (mg/L) (mg/L) (%) OEl 295 152 52 330 185 56 OD 410 269 66 405 311 77 OS 410 183 45 430 197 46 OE2 450 215 48 440 225 51 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 (%) Experiment Secondary Influent ATAD 1 ATAD 2 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 error from possible 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 anywhere from 13 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 Bio-P 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 NH3 in the ATAD reactors. More 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 returned from a sludge digester to the head of a wastewater treatment plant significantly increases various loads on the plant and affects the plant design life. This section first compares 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 anywhere from 5 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 filtrate from the dewatering process could contain anywhere from 1000 to 4000 mg/L SS. This range is comparable to those quoted in Chapter 2 for supernatant from anaerobic and aerobic mesophilic digesters. The following supernatant parameter estimates assume a supernatant solids content of from 1000 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 range from 290 to 370 mg/L and total phosphorus could range from about 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 return flow rate can be estimated as about 1 percent of plant influent flow rate. Using the average influent concentrations for a medium 153 strength wastewater as given by Metcalf and Eddy (1991), the impact of return flows from an 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. TABLE 39 Estimated Effect of ATAD Supernatant Recycle On Influent Flow Concentrations and Loads Influent Recycle Altered Influent Load Change Parameter Low High Low High Low High (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (%) (%) SS 220 1000 4000 230 255 5 18 COD 500 1910 5860 515 555 4 12 TKN 20 610 940 26 29 30 47 NH3 8 575 865 14 16 72 108 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 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 supernatant from an ATAD treating Bio-P sludge is from VFA, 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 release from most biological sludges (baixing inorganic precipitation) is likely to be high. Phosphorus recycling would not be as likely in such a situation, since dissolved phosphorus concentrations from an ATAD treating non Bio-P sludge would probably be similar to that expected from mesophilic 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. This finding might 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 air flows bring 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 sludge from a 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 nitrogen from a digester operating in the oxygen deprived condition. Lower dissolved nitrogen conditions resulted from the 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 the first ATAD 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 2 atmosphere conditions and elevated temperatures. Probe linearity under elevated temperature conditions should also be checked. 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"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 A P P E N D I X 1 D A T A 169 l l 1 IE o I-OQ 5 H O T 3 O > CO 5 t i CO 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\ a ft a 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 o o r- cs m p-' r»" vo" vd T t ' ro' o >n o o o o N r i T t ro T t i n > n m > n i n i n m m . i n i n i n i n i n b b b b b b b b b b b b b in O O 00 CO O o CO m m vq CO o rt-' CS CN CN CN CS CN CN CN T t CN r-' CN b CN CO CN ro' CN CO cs T t cs CO CN o CO o CO cs o co o CO o CO o co o ro CN in CN r--(N CN cs H b b © b b © © b b © b b b o CO co CO o to m cs o CO in co in ro ro ro ro T t co o CO >n CO © CO b b © b © " © © b © b © © b 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 O in O >n o o m CN O © O in in CN o © o in o © o in in r-o in ro' cs T t CS CN CS T t CN in CS T t cs in CN in CS in CS in cs T t CS T t CN T t cs o © o o o o o o o o o m ft od od oo' oo' od oo' od oo' oo' oo' r-' © O © © © © m © © © © © in ro in in r~- r~- r--' r-' r-' t--' r-' r-^  r--' o' rororororororococococoroco ftftftftftftftftftftftftft H H H H RT RT H H H N N N N CQ 5/5 5 < < 170 is IQ § . ^  12. u o > <L) 60 4 > CO C/3 5/3 CO 2" a. i n Vi i n © i n o o © m u~> S o \ h a o o o o o o o o o o i o i o © i n i n i n o © i n © © 0 © i n © i f i H o o o o a a t ^ w a a f t n f t H . 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II co _4> Ct> CQ 5 cu r J 174 l l 1 iff UI <U O I -g 60 d 8 % Pi C O 60 *o o 3 CN 3^ o VO cn o cn i n <n cn o S O cn cn o cn r-1 Os Os i—i o Os 00 S O CN V O V O Os CN so cn i n o o vo m cn cn >n o VO so cn cn vo CN O VO o Os Os cn o Os 00 VO CN VO 00 SO CN VO cn cn vo TT <n ^ i n vo . ^ ^ m CN <n m i n VO I-I 3 O s O O i - H O ' — I ^ O V O O S T J - O O O V T t Tf' i n i n i n i n i n T f T}-' r f T f 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 i n i n i n i n i n i n CN cn i n i n i n i n i n m m ^ CN i i 55 I I I I 3 3 175 APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Excess Experiment No. 1 Date Primary Sludge Bio-P Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 1/6/93 12.5 20842 18963 12.0 24327 19079 1/11/93 13.0 16251 14947 11.0 22493 18144 1/12/93 15.0 18177 16678 9.0 22599 18506 1/13/93 15.0 17376 15800 8.0 23997 19510 1/14/93 17.0 18001 16497 8.0 23544 19016 1/15/93 17.0 17931 16518 8.0 22906 18546 1/16/93 17.0 20436 18698 8.0 22975 18323 1/17/93 17.5 20739 18918 8.0 21571 17270 1/18/93 17.0 17884 16218 8.0 21939 17904 1/19/93 17.0 16221 14749 8.0 23033 18807 1/20/93 17.0 20100 18250 8.0 23276 18937 1/21/93 17.0 19914 16812 8.0 23810 19194 1/22/93 17.0 20214 16089 8.0 22436 17557 1/23/93 17.5 21702 17292 7.5 24177 18989 Average 16.4 18604 16681 8.3 22882 18476 Jan 11-Jan 22/93 Date ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 1/6/93 22.5 18048 14786 26.5 15087 12107 1/11/93 23.7 16652 13841 24.6 16072 12928 1/12/93 24.7 17122 14264 22.2 15479 12643 1/13/93 22.2 16517 13891 22.2 15453 12738 1/14/93 24.4 16736 14041 21.9 15462 12587 1/15/93 25.2 16400 13977 22.4 15232 12550 1/16/93 24.7 16194 13885 24.2 15258 12676 1/17/93 25.4 16747 14224 27.1 14904 12499 1/18/93 25.2 17369 14837 20.5 15398 12900 1/19/93 25.7 16725 14250 23.7 15286 12865 1/20/93 25.2 16909 14494 23.6 15578 13094 1/21/93 24.7 17072 14680 23.7 15334 12932 1/22/93 25.0 17440 14534 24.5 15173 12829 1/23/93 25.0 18122 14813 23.5 16449 13898 Average 24.7 16824 14243 23.4 15386 12770 Mixed Influent Sludge Vol. TS VS (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 Jan 11-Jan 22/93 176 APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Deprived Experiment Date Primary Sludge Bio-P Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 2/22/93 12.0 21907 19390 13.0 22272 17268 2/23/93 12.0 23426 20814 13.0 21441 16530 2/24/93 12.0 24655 22085 13.0 21504 16576 2/25/93 12.0 20457 18371 13.0 22257 17305 2/26/93 12.0 18058 16196 13.0 22846 17720 2/27/93 12.0 18961 17075 13.0 22789 17731 2/28/93 12.0 19979 18025 12.8 22763 17978 3/1/93 12.0 17408 15627 13.0 24263 18899 3/2/93 12.0 20096 18026 13.0 24277 19350 3/3/93 12.0 22763 20535 13.0 24112 19043 3/4/93 12.0 22604 20007 13.0 23574 18646 3/5/93 12.0 23341 20286 13.0 23020 18215 3/6/93 12.0 23380 20210 13.0 22033 17260 Average 12.0 21261 18938 13.0 22907 17938 Feb. 23-M lar 6/93 Date ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 2/22/93 25.5 19534 15451 23.7 17514 13515 2/23/93 25.5 18327 14576 24.4 16523 12615 2/24/93 24.7 18798 15224 24! 1 16933 13098 2/25/93 25.7 19071 15567 23.6 16343 12638 2/26/93 25.2 18758 14984 24.4 17110 13142 2/27/93 25.2 18287 14839 24.1 16849 13311 2/28/93 25.5 18347 14780 24.4 16741 13081 3/1/93 22.5 18744 15192 23.1 16664 13050 3/2/93 24.5 17788 14438 23.6 16546 13123 3/3/93 25.2 18163 14770 22.9 16356 12979 3/4/93 24.5 18219 14848 23.6 16184 12777 3/5/93 24.7 18690 15208 23.1 16835 13336 3/6/93 25.3 18505 14909 24.1 17043 13534 Average 24.9 18475 14945 23.8 16677 13057 Feb. 23-M far 6/93 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 177 APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Satisfied Experiment Date Primary Sludge Bio-P Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 3/31/93 12.0 62853 30124 13.0 29993 19283 4/5/93 12.0 29534 18641 13.0 29522 19071 4/6/93 12.0 24022 16110 13.0 29503 18850 4/7/93 12.0 16012 11978 13.0 29944 19389 4/8/93 12.0 18281 13053 13.0 29489 19140 4/9/93 12.0 15167 11258 13.0 29534 19297 4/10/93 12.0 13826 11024 13.0 30408 19933 4/11/93 12.0 13614 10407 13.0 30730 20123 4/12/93 12.0 10367 8869 13.0 29041 19071 4/13/93 12.0 11159 9337 13.0 30162 19914 4/14/93 12.0 12711 10764 13.0 30167 19926 4/15/93 12.0 21970 17349 13.0 29707 19882 4/16/93 12.0 29020 22911 13.0 28515 18680 Average 12.0 17973 13475 13.0 29727 19440 April 5 - 16 192 Date ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 3/31/93 25.5 33788 16947 24.0 25690 15207 4/5/93 25.2 30805 17029 24.9 31262 16290 4/6/93 25.4 28639 16027 24.4 30769 16029 4/7/93 25.0 26736 15588 25.1 28927 15422 4/8/93 26.0 24318 14527 22.9 28033 14925 4/9/93 26.0 23124 14229 24.6 25820 14148 4/10/93 26.5 21632 13659 24.4 23309 13287 4/11/93 23.3 20606 13133 24.9 22426 12873 4/12/93 24.0 20546 13115 23.1 21454 12433 4/13/93 24.8 19440 12702 24.1 20319 12148 4/14/93 25.0 19253 12649 24.4 19435 11662 4/15/93 25.0 18569 12489 24.4 18668 11706 4/16/93 25.2 20036 13135 24.6 18423 11032 Average 25.1 22809 14024 24.3 24070 13496 Mixed Influent Sludge Vol. TS VS (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 April 5 - 16 193 178 APPENDIX 1: Data. Volumes and Solids Measurements Oxygen Excess Experiment No. 2 Date Primary Sludge Bio-P Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 5/3/93 12.0 17620 14986 13.0 29102 20757 5/4/93 12.0 18891 15938 13.0 29682 21490 5/5/93 12.0 17429 14669 13.0 29255 21138 5/6/93 12.0 20293 17046 13.0 26848 18941 5/7/93 12.0 16057 13456 13.0 26934 18997 5/8/93 12.0 19135 16245 13.0 26406 18734 5/9/93 12.0 19319 16433 13.0 25308 18062 5/10/93 12.0 17296 14791 13.0 25735 18452 5/11/93 12.0 19803 16910 13.0 25327 18093 5/12/93 12.0 19174 16451 13.0 24920 17809 5/13/93 12.0 20969 18024 13.0 23800 17031 5/14/93 12.0 19126 16428 13.0 23417 16701 5/15/93 12.0 20340 17285 13.0 23401 16618 Averages 12.0 18986 16140 13.0 25920 18505 May 4-15/93 Date ATAD 1 Sludge ATAD 2 Sludge Vol. TS VS Vol. TS VS (L/d) (mg/L) (mg/L) (L/d) (mg/L) (mg/L) 5/3/93 24.7 19235 14061 24.4 17568 12436 5/4/93 25.5 19519 14115 22.2 17410 12089 5/5/93 24.2 19445 14503 24.1 17262 12505 5/6/93 26.2 19915 14572 24.2 17481 12467 5/7/93 24.7 19369 14351 26.1 17197 12379 5/8/93 24.5 19084 13850 23.6 17429 12455 5/9/93 24.7 19386 14291 23.9 17053 12337 5/10/93 24.2 19020 14087 24.9 17345 12759 5/11/93 24.9 18813 13714 23.1 17265 12446 5/12/93 25.2 18729 13901 23.6 16964 12241 5/13/93 24.4 19028 13813 24.1 16913 12224 5/14/93 24.4 18722 13700 23.1 17313 12323 5/15/93 24.9 17567 13079 23.1 16370 11751 Averages 24.8 19050 13998 23.8 17167 12331 Mixed Mluent Sludge Vol. TS VS (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 May 4-15/93 179 APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 1 Date Thickened Primary Sludge TKN DTKN NIB NOx (mg/L) (mg/L) (mg/L) ( mg/L) 12/30/92 1/6/93 700 33.0 0.18 1/11/93 497 30.0 25.0 0.23 1/12/93 598 28.8 34.0 0.10 1/13/93 543 37.4 49.5 0.21 1/14/93 532 29.6 21.3 0.20 1/15/93 510 28.2 26.3 0.49 1/16/93 591 31.5 33.2 0.48 1/17/93 632 28.9 38.2 0.18 1/18/93 561 33.0 23.6 0.18 1/19/93 503 29.9 21.1 0.48 1/20/93 611 26.3 17.6 0.41 1/21/93 593 22.6 26.5 0.18 1/22/93 592 22.1 23.8 0.16 1/23/93 643 22.6 21.4 0.16 Averages 563 29.0 28.3 0.28 Jan 11-Jan 22/93 Date Mixed Influent Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) ( mg/L) 1/11/93 888 17.9 14.4 0.31 1/12/93 949 19.5 22.4 0.21 1/13/93 890 25.6 33.2 0.32 1/14/93 813 21.4 14.9 0.36 1/15/93 814 20.2 18.2 0.63 1/16/93 912 22.7 23.2 0.49 1/17/93 883 21.1 26.6 0.20 1/18/93 824 26.2 18.5 0.34 1/19/93 906 21.9 15.1 0.69 1/20/93 919 19.1 12.5 0.43 1/21/93 913 17.8 20.6 0.29 1/22/93 915 16.4 17.3 . 0.21 1/23/93 940 16.9 15.7 0.22 Averages 886 20.8 19.7 0.37 Jan 11-Jan 22/93 Thickened Bio-P Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 7.5 1.56 1575 3.8 0.28 1352 3.8 1.9 0.40 1535 3.9 3.1 0.39 1543 3.7 2.6 0.52 1412 4.2 1.3 0.69 1464 3.5 1.1 0.92 1598 4.0 2.1 0.53 1436 3.9 1.3 0.24 1386 11.7 7.6 0.66 1766 4.8 2.4 1.13 1577 3.9 1.5 0.48 1596 7.8 8.1 0.54 1605 4.5 3.6 0.31 1637 3.7 2.5 0.35 1522 5.0 3.1 0.57 180 APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 1 Date ATAD 1 Sludge TKN Dl KN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 1/6/93 1125 26.0 2.36 1/11/93 973 326.8 288.5 14.32 1/12/93 922 336.6 285.0 12.04 1/13/93 894 348.9 406.0 13.73 1/14/93 859 343.9 329.0 14.66 1/15/93 833 313.7 272.7 4.87 1/16/93 761 294.4 326.9 2.89 1/17/93 815 317.3 233.1 6.36 1/18/93 772 315.9 241.2 10.68 1/19/93 783 297.4 231.6 11.40 1/20/93 788 280.1 256.3 5.92 1/21/93 816 281.8 308.7 5.82 1/22/93 789 282.6 273.4 7.10 1/23/93 786 273.2 256.5 15.40 Averages 834 311.6 287.7 9.15 Jan 11-Jan 22/93 ATAD 2 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 913 2.89 951 509.3 457.6 13.97 963 564.6 579.9 14.52 934 590.6 667.6 13.40 954 520.5 480.4 11.75 941 531.2 558.1 11.27 936 499.5 418.4 7.27 868 484.1 371.6 5.17 883 437.6 531.0 5.87 838 447.6 366.9 7.48 837 486.0 483.2 7.16 793 450.6 460.2 6.00 794 442.5 460.5 4.69 808 429.8 398.6 4.98 891 497.0 486.3 9.05 181 APPENDIX 1: Data. Nitrogen Measurements Oxygen De srived Experiment Date Thickened Primary Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 594 35.4 31 0.09 2/23/93 611 30.7 29.57 0.09 2/24/93 657 33.8 29.2 0^ 08 2/25/93 624 45.2 33.3 0.10 2/26/93 575 34.9 37.6 0.10 2/27/93 626 53.5 35.6 0.15 2/28/93 574 31.4 31.1 0.17 3/1/93 538 35.2 31.7 0.38 3/2/93 630 21.0 21.3 0.20 3/3/93 653 30.5 28.1 0.11 3/4/93 558 31.4 32.1 0.17 3/5/93 563 29.2 28.1 0.19 3/6/93 562 34.9 32.3 0.13 Averages 598 34.3 30.8 0.16 Feb 23-Mar 6/93 Date 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 2/23/93 1160 20.0 18.6 0.24 2/24/93 1108 22.4 19.0 0.32 2/25/93 1258 26.5 19.3 0.15 2/26/93 1261 23.1 22.6 0.20 2/27/93 1225 33.0 23.1 0.21 2/28/93 1177 26.6 26.3 0.20 3/1/93 1153 . 22.5 19.4 0.34 3/2/93 1290 36.7 32.1 0.19 3/3/93 1240 25.0 24.2 0.25 3/4/93 1160 22.4 22.6 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 23-Mar 6/93 Thickened Bio-P Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 1714 6.6 4.7 0.33 1669 10.1 8.5 0.38 1528 12.0 9.7 0.53 1846 ' 9.2 6.4 0.20 1898 12.3 8.9 0.29 1781 14.1 11.6 0.27 1747 22.1 21.9 0.23 1723 10.8 8.1 0.29 1901 51.4 42.2 0.19 1784 20.0 20.7 0.38 1718 14.1 14.0 0.29 1573 24.2 24.0 0.44 1423 4.8 3.7 0.22 ; 1716 17.1 15.0 0.31 182 APPENDIX 1: Data. Nitrogen Measurements Oxygen De )rived Experiment Date ATAD 1 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) ( mg/L) 2/22/93 1017 533.6 594.1 0.09 2/23/93 998 606.9 644.9 0.44 2/24/93 1023 619.1 669.8 -0.02 2/25/93 1100 422.3 478.1 0.11 2/26/93 1100 407.3 431.8 0.11 2/27/93 1131 444.6 471.0 -0.71 2/28/93 1089 442.7 473.3 0.08 3/1/93 1059 513.9 528.3 0.36 3/2/93 1132 459.6 506.6 0.20 3/3/93 1119 451.6 511.8 0.20 3/4/93 1045 508.7 580.1 0.12 3/5/93 1083 493.7 532.3 0.22 3/6/93 1037 391.5 412.8 0.66 Averages 1076 480.2 520.1 0.15 ATAD 2 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 969 578.1 644.0 -0.08 962 644.8 680.8 -0.06 978 597.9 652.1 0.93 1024 626.1 666.0 0.09 1051 1072.1 973.9 0.11 1084 685.7 696.8 0.32 1113 710.3 756.9 0.12 1066 997.5 959.2 0.19 1063 749.9 782.8 0.22 1048 861.9 869.1 0.20 1000 598.5 668.6 0.19 984 540.8 569.5 0.07 1029 591.0 601.0 1.11 1034 723.0 739.7 0.29 Feb 23-Mar 6/93 Note: Negative values for NOx result from subtraction of high colour interference results 183 APPENDIX 1: Data. Nitrogen Measurements Oxygen Satisfied Experiment Date Thickened Primary Sludge TKN DTKN NII3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 3/31/93 881 24.4 26 0.11 4/5/93 629 23.7 19.57 0.17 4/6/93 548 24.8 18.7 0.32 4/7/93 371 26.5 20.8 0.37 4/8/93 426 31.8 27.4 0.12 4/9/93 360 25.2 20.2 0.21 4/10/93 331 24.7 20.5 0.15 4/11/93 334 21.6 18.8 0.11 4/12/93 258 21.9 18.1 0.12 4/13/93 315 21.9 18.7 0.20 4/14/93 323 22.5 18.3 0.20 4/15/93 583 25.7 21.4 0.10 4/16/93 725 28.6 26.3 0.12 Averages 434 24.9 20.7 0.18 Apr. 5-16/93 Date Mixed influent Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 3/31/93 4/5/93 1141 12.3 9.6 0.17 4/6/93 1127 12.8 9.2 0.29 4/7/93 957 13.8 10.3 0.32 4/8/93 1087 16.8 14.1 0.22 4/9/93 924 15.3 12.1 0.28 4/10/93 979 13.4 10.8 0.20 4/11/93 960 11.4 9.5 0.16 4/12/93 936 11.3 9.1 0.17 4/13/93 964 11.5 9.4 0.18 4/14/93 933 11.9 9.1 0.22 4/15/93 1082 13.9 10.7 0.16 4/16/93 1179 16.4 12.8 0.15 Averages 1022 13.4 10.6 0.21 Apr. 5-16/93 Thickened Bio-P Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 1602 2.3 1.0 0.22 1616 1.8 0.5 0.18 1664 1.7 0.4 0.26 1499 2.2 0.7 0.27 1700 3.0 1.9 0.31 1447 6.2 4.6 0.34 1580 3.0 1.9 0.25 1541 2.1 0.9 0.21 1563 1.6 0.9 0.22 1566 2.0 0.7 0.17 1498 2.0 0.6 0.24 1544 3.0 0.8 0.22 1601 5.1 0.4 0.19 1568 2.8 1.2 0.24 APPENDIX 1: Data. Nitrogen Measurements Oxygen Satisfied Experiment Date ATAD 1 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 3/31/93 1080 323.1 359.5 0.33 4/5/93 1144 382.3 331.2 0.54 4/6/93 1098 362.3 288.8 1.24 4/7/93 1063 383.4 304.6 0.38 4/8/93 1029 324.9 302.6 2.13 4/9/93 996 310.9 296.2 1.62 4/10/93 945 302.3 280.0 1.33 4/11/93 913 299.6 300.5 0.59 4/12/93 916 327.8 317.5 0.12 4/13/93 954 295.9 289.1 1.12 4/14/93 879 297.4 260.5 1.46 4/15/93 901 305.1 258.3 0.49 4/16/93 940 294.4 287.7 0.23 Averages 982 323.8 293.1 0.94 Apr. 5-16/93 ATAD 2 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 1068 490.5 579.1 0.17 1146 501.6 429.6 0.45 1218 547.9 497.7 0.36 1189 561.2 508.9 0.20 1163 614.6 557.5 0.35 1196 551.3 499.4 0.81 1093 504.8 487.3 0.92 944 488.8 487.2 0.93 996 480.6 471.5 0.75 901 526.3 502.3 0.65 861 447.0 427.1 0.72 937 436.9 419.6 1.03 916 468.4 456.1 0.93 1047 510.8 478.7 0.67 185 APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 2 Date Thickened Primary Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 5/3/93 491 22.1 18 0.18 5/4/93 560 20.4 16.73 0.28 5/5/93 534 24.1 19.1 0.20 5/6/93 620 18.2 14.7 0.14 5/7/93 485 19.1 16.5 0.21 5/8/93 581 17.5 15.6 0.33 5/9/93 631 21.4 18.2 0.18 5/10/93 562 17.9 15.8 0.22 5/11/93 643 19.4 17.2 0.15 5/12/93 608 20.7 16.8 0.10 5/13/93 668 22.4 19.2 0.13 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 Date 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 5/5/93 1208 12.6 9.4 0.18 5/6/93 1209 9.9 7.4 0.15 5/7/93 1059 11.1 8.7 0.29 5/8/93 1109 9.5 7.8 0.30 5/9/93 1178 11.2 9.0 0.17 5/10/93 1060 9.8 8.0 0.22 5/11/93 1109 10.3 8.7 0.27 5/12/93 1053 10.7 8.3 0.13 5/13/93 1018 11.7 9.4 0.26 5/14/93 1000 11.4 8.7 0.11 5/15/93 1040 12.5 9.6 0.18 Averages 1108 11.0 8.6 0.21 May 4-15/93 Thickened Bio-P Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 1832 2.2 0.5 0.21 1894 3.1 1.4 0.33 1831 2.1 0.5 0.16 1755 2.1 0.7 0.16 1590 3.6 1.5 0.37 1598 2.1 0.6 0.27 1685 1.8 0.4 0.17 1521 2.3 0.8 0.21 1542 1.9 0.9 0.38 1466 1.5 0.4 0.16 1341 1.8 0.4 0.39 1334 1.9 0.9 0.12 1386 1.5 0.6 0.19 1579 2.2 0.8 0.24 186 APPENDIX 1: Data. Nitrogen Measurements Oxygen Excess Experiment No. 2 Date ATAD 1 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 5/3/93 929 290.4 266.1 6.74 5/4/93 991 282.6 250.8 13.22 5/5/93 1058 293.6 259.3 5.27 5/6/93 1029 473.1 249.0 3.21 5/7/93 1091 264.8 248.5 8.18 5/8/93 1017 260.6 241.1 12.96 5/9/93 1006 266.1 242.5 15.81 5/10/93 1001 260.4 239.6 16.21 5/11/93 988 293.1 273.5 13.44 5/12/93 988 300.6 279.1 10.06 5/13/93 942 307.3 299.3 9.40 5/14/93 921 308.1 285.7 8.24 5/15/93 934 291.0 273.4 8.75 Averages 997 300.1 261.8 10.40 May 4-15/93 ATAD 2 Sludge TKN DTKN NH3 NOx (mg/L) (mg/L) (mg/L) (mg/L) 929 470.4 420.0 7.05 905 443.6 410.3 6.58 933 471.0 412.5 9.48 981 284.1 415.2 8.10 983 475.1 458.1 5.13 1011 486.9 449.4 6.83 1007 487.9 442.5 8.67 1001 490.1 458.0 12.44 1008 465.8 442.6 12.96 983 476.4 447.6 13.21 958 450.0 455.2 12.19 932 460.1 425.0 11.20 941 453.4 403.9 9.64 970 453.7 435.0 9.70 187 APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 1 Date Thickened Primary Sludge TP TDP P04 (mg/L) (mg/L) (mgT.) 12/30/92 1/6/93 107 6.0 5.8 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 1/22/93 114 5.4 3.1 1/23/93 120 4.8 3.5 Averages 107 7.1 5.2 Jan 11-Jan 22/93 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 1/15/93 292 7.8 5.8 1/16/93 312 8.5 6.1 1/17/93 278 8.2 3.4 1/18/93 288 15.5 11.1 1/19/93 306 8.1 6.5 1/20/93 300 7.3 5.7 1/21/93 325 10.6 9.7 1/22/93 318 5.7 3.5 1/23/93 325 7.0 5.2 Averages 309 9.1 6.9 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 10.8 729 12.2 9.3 666 19.0 18.2 702 11.1 9.0 732 14.0 10.1 649 14.3 6.1 659 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 Jan 11-Jan 22/93 188 APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 1 Date ATAD 1 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 1/6/93 400 140.5 143.3 1/11/93 374 183.6 163.1 1/12/93 345 175.3 128.1 1/13/93 346 175.9 133.5 1/14/93 299 190.9 172.7 1/15/93 291 162.0 102.5 1/16/93 260 145.0 85.9 1/17/93 293 131.8 80.4 1/18/93 264 152.6 108.8 1/19/93 271 133.1 118.4 1/20/93 253 122.6 110.2 1/21/93 276 128.3 . 79.0 1/22/93 277 123.6 98.1 1/23/93 289 124.5 105.8 Averages 296 152.1 115.1 ATAD 2 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 338 131.3 129.4 381 203.3 166.8 344 226.3 120.0 352 211.3 115.1 371 199.5 180.5 351 204.8 147.6 333 186.9 80.5 304 186.8 95.2 323 168.8 109.2 323 157.5 140.1 309 166.5 130.2 282 166.9 102.0 282 146.3 103.9 294 136.9 115.0 330 185.4 124.3 Jan 11-Jan 22/93 189 APPENDIX 1: Data. Phosphorus Measurements Oxygen De prived Experiment Date Thickened Primary Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 2/22/93 114 10.9 2/23/93 109 15.9 5.7 2/24/93 115 17.0 5.6 2/25/93 106 12.2 5.9 2/26/93 97 8.5 6.5 2/27/93 104 17.6 6.7 2/28/93 98 9.7 6.5 3/1/93 91 11.8 6.5 3/2/93 101 9.9 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 Thickened Bio-P Sludge TP TDP P04 (mg/L) (mg/L) ( mg/L) 841 12.9 810 10.5 8.0 761 10.5 9.0 794 18.8 11.0 824 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 13.9 779 14.7 9.7 721 21.2 11.8 699 7.2 6.2 748 15.2 10.8 Feb 23-Mar 6/93 Date 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 2/24/93 451 13.6 7.3 2/25/93 463 15.6 8.6 2/26/93 474 ' 10.3 8.6 2/27/93 430 15.9 8.7 2/28/93 421 15.2 10.1 3/1/93 422 14.3 10.6 3/2/93 397 3/3/93 428 15.2 10.9 3/4/93 459 14.9 8.8 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 6/93 190 APPENDIX 1: Data. Phosphorus Measurements Oxygen De )rived Experiment Date ATAD 1 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 2/22/93 398 269.6 212.3 2/23/93 406 300.2 234.0 2/24/93 411 345.0 202.9 2/25/93 406 259.1 185.7 2/26/93 417 252.4 187.4 2/27/93 417 242.3 197.8 2/28/93 418 244.5 189.3 3/1/93 395 267.6 208.6 3/2/93 414 246.7 207.8 3/3/93 394 241.3 234.9 3/4/93 406 286.3 205.3 3/5/93 444 295.9 208.4 3/6/93 396 248.8 204.7 Averages 410 269.2 205.6 ATAD 2 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 381 259.5 196.5 399 261.6 181.7 401 263.6 209.8 416 250.3 187.8 416 468.9 169.9 406 294.0 185.4 414 307.7 177.7 406 455.6 182.9 404 305.6 202.3 409 352.4 193.0 417 270.9 209.1 379 235.5 182.2 390 261.2 179.7 405 310.6 188.5 Feb 23-Mar 6/93 191 APPENDIX 1: Data. Phosphorus Measurements Oxygen Satisfied Experiment Date Thickened Primary Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 3/31/93 209 3.5 4.5 4/5/93 128 3.5 3.8 4/6/93 106 4.5 4.1 4/7/93 68 4.4 4.3 4/8/93 78 6.8 6.9 4/9/93 56 4.2 4.2 4/10/93 58 5.8 5.7 4/11/93 68 5.5 5.6 4/12/93 44 4.2 4.2 4/13/93 58 4.7 4.5 4/14/93 64 4.6 4.2 4/15/93 109 4.5 4.8 4/16/93 125 4.7 4.7 Averages 80 4.8 4.8 Apr. 5-16/93 Date Mixed influent Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 4/5/93 465 3.8 4.0 4/6/93 466 3.8 3.7 4/7/93 420 3.1 3.3 4/8/93 457 5.9 6.0 4/9/93 425 5.6 5.5 4/10/93 410 7.4 7.4 4/11/93 436 6.1 6.2 4/12/93 410 4.9 4.9 4/13/93 442 5.9 5.9 4/14/93 430 4.1 4.0 4/15/93 401 4.4 4.7 . 4/16/93 426 3.9 4.3 Averages 432 4.9 5.0 Thickened Bio-P Sludge TP TDP P04 (mg/L) (mg/L) ( mg/L) 792 9.8 9.4 778 4.0 .4.2 801 3.2 3.3 746 1.9 2.4 807 5.1 5.1 766 6.9 6.7 735 9.0 8.9 777 6.7 6.8 748 5.5 5.6 799 7.0 7.3 769 3.7 3.8 672 4.2 4.7 704 3.1 3.9 759 5.0 5.2 Apr. 5-16/93 192 APPENDIX 1: Data. Phosphorus Measurements Oxygen Satisfied Experiment Date ATAD 1 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 3/31/93 463 165.9 170.4 4/5/93 471 167.6 182.1 4/6/93 451 156.4 164.0 4/7/93 431 177.8 189.4 4/8/93 423 . 172.9 176.2 4/9/93 413 182.1 188.8 4/10/93 418 186.4 190.7 4/11/93 413 195.2 200.6 4/12/93 401 205.7 209.7 4/13/93 414 195.2 202.0 4/14/93 404 205.1 190.8 4/15/93 331 189.2 185.7 4/16/93 370 166.1 170.9 Averages 411 183.3 187.6 ATAD 2 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 439 188.3 196.3 469 174.2 176.2 469 178.3 193.0 465 176.8 214.0 458 197.3 203.8 468 193.9 196.9 426 191.8 197.4 434 199.3 203.2 427 204.4 208.0 415 229.7 237.4 403 207.0 200.2 364 200.6 202.5 357 '. 208.3 209.1 430 196.8 203.5 Apr. 5-16/93 193 APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 2 Date Thickened Primary Sludge TP TDP P04 (mg/L) (mg/L) ( mg/L) 5/3/93 103 5.1 5.2 5/4/93 107 3.6 3.7 5/5/93 104 6.3 6.1 5/6/93 118 2.8 3.4 5/7/93 87 3.1 3.4 5/8/93 114 3.0 3.1 5/9/93 130 6.2 6.5 5/10/93 104 3.3 3.3 5/11/93 124 4.3 4.4 5/12/93 113 4.4 4.0 5/13/93 129 4.8 5.2 5/14/93 117 4.7 4.7 5/15/93 128 5.4 5.0 Averages 115 4.3 4.4 May 4-15/93 Date Mixed Influent Sludge 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 Averages 473 7.1 7.4 Thickened Bio-P Sludg e TP TDP P04 (mg/L) (mg/L) (mg/L) 1081 13.0 14.3 1125 19.3 19.9 1041 14.9 17.2 848 13.7 15.2 794 4.8 5.8 796 8.6 8.7 817 7.2 7.1 776 9.1 9.9 720 9.4 9.4 701 6.3 6.8 676 8.4 8.3 662 6.9 7.4 702 7.1 7.2 805 9.6 10.3 May 4-15/93 194 APPENDIX 1: Data. Phosphorus Measurements Oxygen Excess Experiment No. 2 Date ATAD 1 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 5/3/93 393 187.5 196.3 5/4/93 466 229.1 230.7 5/5/93 501 259.7 253.4 5/6/93 497 221.6 255.6 5/7/93 501 232.7 235.2 5/8/93 478 226.7 230.0 5/9/93 452 220.1 214.1 5/10/93 439 201.8 215.9 5/11/93 429 221.8 226.2 5/12/93 439 198.2 214.2 5/13/93 406 199.1 204.3 5/14/93 401 189.8 194.6 5/15/93 400 180.9 192.7 Averages 451 215.1 222.2 ATAD 2 Sludge TP TDP P04 (mg/L) (mg/L) (mg/L) 372 194.3 198.9 384 195.9 197.5 407 216.6 213.7 446 251.8 229.6 457 224.6 238.7 453 234.8 231.0 472 241.3 233.5 461 240.6 242.0 474 225.6 227.7 460 221.4 228.1 444 218.4 224.5 431 217.9 222.6 416 208.5 219.2 442 224.8 .225.7 May 4-15/93 195 APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Excess Experiment No. 1 Date Primary Sludge Bio-P Sludge 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 1/22/93 485 375 1/23/93 605 420 Average 485 375 Jan 11-Jan 22/93 Date ATAD 1 Sludge Alkalinity pH (mg/L as CaC03) 1/11/93 1/12/93 1/13/93 8.1 1/14/93 8.0 1/15/93 1/16/93 1/17/93 8.2 1/18/93 8.0 1/19/93 8.0 1/20/93 8.1 1/21/93 7.9 1/22/93 1173 8.3 1/23/93 1173 7.7 Average 1173 Note: Influent sludges are thickened ATAD 2 Sludge Alkalinity pH (mg/L as CaC03) 8.4 8.1 8.2 8.2 8.2 8.3 7.9 1650 8.3 1685 7.8 1650 Jan 11-Jan 22/93 196 APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Deprived Experiment Date Primary Sludge Bio-P Sludge Alkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 2/22/93 510 470 2/23/93 2/24/93 474 420 2/25/93 2/26/93 355 385 2/27/93 306 406 2/28/93 3/1/93 3/2/93 332 408 • 3/3/93 3/4/93 321 520 3/5/93 3/6/93 313 316 Average 350 409 Feb. 23-M tar 6/93 Date ATAD 1 Sludge Alkalinity pH (mg/L as CaC03) 2/22/93 2030 6.5 2/23/93 6.9 2/24/93 1965 6.9 2/25/93 7.2 2/26/93 1515 7.1 2/27/93 1505 7.1 2/28/93 7.1 3/1/93 7.2 3/2/93 1474 6.8 3/3/93 6.9 3/4/93 1556 7.0 3/5/93 7.0 3/6/93 1480 7.1 Average 1582 Feb. 23-M tar 6/93 Note: Influent sludges are thickened ATAD 2 Sludge Alkalinity pH (mg/L as CaC03) 1921 7.3 7.4 1550 7.1 7.7 1553 7.8 1763 7.6 7.7 7.7 1920 7.5 7.5 1920 7.4 7.3 1929 7.7 1772 197 APPENDIX 1: Data. Alkalinity and pH Measurements Oxygen Satisfied Experiment Date Primary Sludge Bio-P Sludge Ajjkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 3/31/93 1199 662 4/5/93 4/6/93 585 435 4/7/93 4/8/93 435 306 4/9/93 4/10/93 449 412 4/11/93 408 375 4/12/93 4/13/93 439 510 4/14/93 4/15/93 495 495 4/16/93 Average 468 422 April 5 - 16 /93 Date ATAD 1 Sludge Alkalinity pH (mg/L as CaC03) 3/31/93 1786 7.3 4/5/93 7.5 4/6/93 1700 7.6 4/7/93 7.6 4/8/93 1444 7.5 4/9/93 7.5 4/10/93 1300 7.5 4/11/93 1290 7.5 4/12/93 7.4 4/13/93 1339 7.4 4/14/93 7.4 4/15/93 1310 7.4 4/16/93 7.4 Average 1397 Note: Influent sludges are thickened ATAD 2 Sludge Alkalinity pH (mg/L as CaC03) 2300 7.6 7.8 2401 7.7 7.9 2320 7.8 7.8 2045 .7.7 1945 7.9 7.9 1984 7.8 7.8 1915 7.8 7.8 2102 April 5 - 16 /93 198 APPENDIX 1: Data. Alkalinity and pH Measurements May 4-15/93 Oxygen Excess Experiment No. 2 Date Primary Sludge Bio-P Sludge Alkalinity Alkalinity (mg/L as (mg/L as CaC03) CaC03) 5/3/93 5/4/93 455 638 5/5/93 5/6/93 354 525 5/7/93 5/8/93 520 525 5/9/93 475 505 5/10/93 5/11/93 470 546 5/12/93 5/13/93 364 419 5/14/93 5/15/93 Average 439 526 May 4-15/93 Date ATAD 1 Sludge Alkalinity PH (mg/L as CaC03) 5/3/93 8.0 5/4/93 1235 7.8 5/5/93 7.8, 5/6/93 1290 7.8 5/7/93 7.7 5/8/93 1250 7.8 5/9/93 1275 7.7 5/10/93 7.8 5/11/93 1332 7.8 5/12/93 8.0 5/13/93 1445 7.7 5/14/93 7.9 5/15/93 8.0 Average 1304 Note: Influent sludges are thickened ATAD 2 Sludge Alkalinity pH (mg/L as CaC03) 8.0 1903 8.0 7.9 1904 7.9 7.8 1940 7.9 1975 7.9 7.9 2065 7.9 8.0 1990 7.9 8.0 8.0 1963 199 APPENDIX 1: Data. COD Measurements Oxygen Excess Experiment No. 1 Date Primary Sludge Bio-P Sludge Mixed Influent Sludge Total COD Total COD Total COD (mg/L) (mg/L) (mg/L) 1/11/93 22657 1/12/93 1/13/93 1/14/93 1/15/93 1/16/93 32153 31751 32024 1/17/93 29964 28803 29600 1/18/93 1/19/93 22371 30858 25087 1/20/93 1/21/93 25690 25113 25505 1/22/93 29149 27907 28752 1/23/93 29460 27996 29021 Averages 28131 27869 28332 Jan 11-Jan 22/93 Note: Influent Sludges are Thickened Date ATAD 1 ATAD 2 Total COD Total COD (mg/L) (mg/L) 1/11/93 16454 17102 1/12/93 20343 17218 1/13/93 1/14/93 19288 15833 1/15/93 20157 18007 1/16/93 18385 21731 1/17/93 22044 16689 1/18/93 1/19/93 20705 18385 1/20/93 1/21/93 17512 14254 1/22/93 20744 16992 1/23/93 Averages 19515 17357 Jan 11-Jan 22/93 APPENDIX 1: Data. COD Measurements Oxygen Deprived Experiment Date Primary Sludj ge Bio-P Sludge Mixed Influent Sludge Total Soluble Total Soluble Total Soluble 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 2/24/93 43885 212 26388 66 34787 136 2/25/93 2/26/93 25040 27154 26140 2/27/93 30629 246 27734 63 29124 151 2/28/93 3/1/93 23452 349 26058 72 24807 205 3/2/93 3/3/93 35402 274 29338 49 32249 157 3/4/93 3/5/93 30235 251 26942 55 28523 149 3/6/93 Averages 31441 267 27269 61 29272 160 Feb 23-Mar 6/93 Note: Influent sludges are thickened Date ATAD 1 ATAD 2 Total Soluble Total Soluble COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 24354 3061 19018 2030 2/23/93 2/24/93 22626 2039 17138 1892 2/25/93 2/26/93 21732 17563 2/27/93 20226 1177 18752 1348 2/28/93 3/1/93 19887 1258 17897 1956 3/2/93 3/3/93 21373 1796 18109 1744 3/4/93 3/5/93 23916 1712 18189 1256 3/6/93 Averages 21627 1596 17941 1639 Feb 23-Mar 6/93 APPENDIX 1: Data. COD Measurements Oxygen Satisfied Experiment Date Primary Slud ?e Bio-P Sludge Mixed Influent Sludge Total Soluble Total Soluble Total Soluble COD COD COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 3/31/93 54682 421 34449 55 44161 231 4/5/93 30208 198 33570 39 31956 115 4/6/93 4/7/93 16797 148 32453 30 26496 80 4/8/93 4/9/93 20345 126 32173 38 26438 81 4/10/93 4/11/93 4/12/93 15008 123 34051 31 24911 75 4/13/93 4/14/93 18043 135 33761 31 26216 81 4/15/93 4/16/93 45929 273 32479 71 38935 168 Averages 24388 167 33081 40 29159 100 Apr. 5-16/93 Note: mfluent sludges are thickened Date ATAD 1 ATAD 2 Total Soluble Total Soluble COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) 3/31/93 29232 759 23920 1154 4/5/93 25629 763 24670 969 4/6/93 4/7/93 21985 679 24919 1041 4/8/93 4/9/93 20807 400 22143 707 4/10/93 4/11/93 4/12/93 19449 359 19543 600 4/13/93 4/14/93 20114 281 17821 470 4/15/93 4/16/93 19156 381 14160 501 Averages 21190 477 20543 714 Apr. 5-16/93 202 APPENDIX 1: Data. COD Measurements Oxygen Excess Experiment No. 2 Date Primary Sludj »e Bio-P Sludge Mixed Influent Sludge Total Soluble Total Soluble Total Soluble COD COD COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 5/3/93 22574 226 35214 42 29147 130 5/4/93 5/5/93 21980 274 34890 48 28693 157 5/6/93 5/7/93 21178 175 32310 56 28686 114 5/8/93 5/9/93 28044 206 29278 28 28680 115 5/10/93 25225 232 30318 66 27873 146 5/11/93 5/12/93 30480 268 28893 . 45 29655 152 5/13/93 5/14/93 5/15/93 38868 248 28059 44 33247 142 Averages 27629 234 30625 48 29472 137 May 4-15/93 Note: Influent sludges are thickened Date ATAD 1 ATAD 2 Total Soluble Total Soluble COD COD COD COD (mg/L) (mg/L) (mg/L) (mg/L) 5/3/93 20190 408 18944 549 5/4/93 5/5/93 19984 388 18465 544 5/6/93 5/7/93 22222 376 18568 647 5/8/93 5/9/93 21253 342 18387 605 5/10/93 21801 364 18809 712 5/11/93 5/12/93 21754 369 17311 567 5/13/93 5/14/93 r 5/15/93 19541 452 18267 662 Averages 21093 382 18301 623 May 4-15/93 203 APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 1 Date Primary Sludge Bio-P Sludge Acetate Pro- Iso- Butyrate Acetate prionate Butyrate (mg/L) (mg/L) (mg/L) (mg/L) (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 42.17 1.15 0.83 1.75 1/20/93 50.77 43.10 1.10 0.85 1.62 1/21/93 40.32 29.89 0.69 1.61 1/22/93 38.39 26.56 0.00 1/23/93 39.49 29.66 0.00 Date ATAD 1 ATAD 2 Acetate Acetate (mg/L) (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 10.86 9.00 1/20/93 9.98 11.94 1/21/93 2.70 0.11 1/22/93 2.55 0.00 1/23/93 0.00 0.00 204 APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Deprived Experiment Date Thickened Primary Sludge Bio-P Sludge Acetate Proprio- Iso- Butyrate A- . Iso- Acetate nate 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 2/24/93 51.92 51.67 0.88 0.00 2/25/93 2/26/93 58.34 62.32 0.55 1.93 2.23 2/27/93 2/28/93 3/1/93 3/2/93 79.57 80.10 2.06 5.45 1.24 1.85 2.65 3/3/93 3/4/93 69.81 70.51 1.61 4.63 2.44 3/5/93 Date ATAD 1 Acetate Proprio- Iso- Butyrate A- Iso- Valerate nate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 1228.14 169.61 148.40 26.46 85.33 173.29 32.65 2/23/93 2/24/93 500.97 7.10 116.61 23.45 135.51 2/25/93 2/26/93 9.56 2/27/93 2/28/93 3/1/93 3/2/93 650.36 13.59 81.42 0.51 44.97 77.97 3/3/93 3/4/93 390.71 4.60 55.65 63.04 32.20 3/5/93 205 APPENDIX l:Data. Volatile Fatty Acids Measurements Oxygen Deprived Experiment Date ATAD 2 Acetate Proprio- Iso- Butyrate A- Iso-nate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 2/22/93 419.19 85.25 97.92 33.00 92.38 2/23/93 2/24/93 274.40 65.95 54.87 58.53 2/25/93 2/26/93 2/27/93 2/28/93 3/1/93 3/2/93 0.68 1.00 3/3/93 3/4/93 4.17 3/5/93 206 APPENDIX l:Data. Volatile Fatty Acids Measurements Oxygen Satisfied Experiment Date Primary Sludge Bio-P Sludge Acetate Proprio- Iso- Butyrate A- Iso- Acetate nate Butyrate Valerate Valerate (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) 4/5/93 4/6/93 30.29 19.45 0.74 1.28 2.46 4/7/93 4/8/93 29.26 17.68 0.70 1.47 1.15 4/9/93 34.04 16.58 1.03 1.06 0.00 4/10/93 4/11/93 36.71 23.97 1.19 1.58 0.00 4/12/93 4/13/93 34.08 21.94 1.32 1.56 0.96 4/14/93 4/15/93 51.77 . 40.65 2.40 3.99 1.74 0.00 4/16/93 Date ATAD 1 ATAD 2 Acetate Proprio- Iso- Acetate (mg/L) nate Butyrate (mg/L) (mg/L) (mg/L) 4/5/93 4/6/93 1.42 0.54 0.49 1.15 4/7/93 4/8/93 7.87 0.30 1.37 4/9/93 0.48 3.16 4/10/93 4/11/93 3.01 3.18 4/12/93 4/13/93 2.71 0.22 3.01 4/14/93 4/15/93 2.04 5.61 4/16/93 207 APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 2 Date Primary Sludge Acetate Pro- Iso- Butyrate A- ' . Iso-prionate Butyrate Valerate Valerate (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 5/6/93 48.11 49.97 1.12 2.79 . 5/7/93 5/8/93 40.44 34.94 1.02 1.77 1.13 5/9/93 52.96 49.55 1.38 5/10/93 5/11/93 71.06 77.38 2.12 5.06 1.78 2.03 5/12/93 5/13/93 70.78 75.63 2.22 5.26 1.82 2.21 5/14/93 5/15/93 Date Bio-P Sludge Acetate Pro- Iso- Butyrate A-prionate 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 5/8/93 4.67 1.16 0.32 0.86 5/9/93 2.12 5/10/93 5/11/93 2!30 5/12/93 5/13/93 1.66 5/14/93 5/15/93 208 APPENDIX 1: Data. Volatile Fatty Acids Measurements Oxygen Excess Experiment No. 2 Date ATAD 1 ATAD 2 Acetate Acetate Pro-prionate (mg/L) (mg/L) (mg/L) 5/4/93 3.57 2.09 5/5/93 5/6/93 2.60 3.07 0.40 5/7/93 5/8/93 1.55 2.22 5/9/93 2.55 3.99 5/10/93 5/11/93 9.02 5.31 5/12/93 5/13/93 2.91 5.18 5/14/93 5/15/93 209 APPENDIX 1: Discharge Gas Measurements Oxygen Deprived Experiment Date ATAD 1 ATAD 2 C02 02 N2 C02 02 N2 (%) (%) (%) (%) (%) (%) 2/23/93 10.50 10.70 78.80 2/24/93 2/25/93 2/26/93 11.80 7.37 80.83 6.69 13.97 79.35 2/27/93 2/28/93 3/1/93 3/2/93 16.82 4.51 78.67 10.09 11.50 78.41 3/3/93 3/4/93 3/5/93 15.23 4.19 80.58 8.93 11.25 79.82 3/6/93 Note: (%)- percent by volume Oxygen Satisfied Experiment Date ATAD 1 ATAD 2 C02 02 N2 NH3 C02 02 N2 NH3 (%) (%) (%) (g/d) (%) (%) (%) (g/d) 4/5/93 4/6/93 7.95 13.31 78.73 7.69 13.51 78.80 0.001 4/7/93 4/8/93 4/9/93 6.48 15.13 78.39 0.001 6.00 15.24 78.76 0.001 4/10/93 4/11/93 6.75 14.94 78.32 0.002 4.41 17.73 77.86 0.001 4/12/93 4/13/93 4/14/93 7.23 14.42 78.36 0.001 0.002 4/15/93 5.06 16.72 78.21 4/16/93 8.09 13.30 78.61 0.003 6.61 14.73 78.66 0.002 Note: (%)= percent by volume 210 APPENDIX 1: Discharge Gas Measurements Oxygen Excess Experiment No. 2 Date ATAD 1 ATAD 2 C02 02 N2 NH3 C02 02 N2 NH3 (%) (%) (%) (g/d) (%) (%) (%) (g/d) 5/4/93 0.00 20.18 79.82 0.031 3.41 18.63 77.95 0.094 5/5/93 5/6/93 0.90 19.14 79.95 0.024 1.38 18.64 79.98 0.118 5/7/93 5/8/93 1.14 18.74 80.12 0.256 2.11 17.83 80.06 0.090 5/9/96 5/10/93 5/11/93 1.89 18.14 79.97 0.195 2.66 17.65 79.69 0.149 5/12/93 5/13/93 2.11 17.87 80.02 2.31 18.03 79.66 5/14/93 5/15/93 0.156 0.186 Note: (%)= percent by volume 211 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 S := 13 liter A1S = 0.5-liter A I T := 25.25-liter A 1 T R := 0.25-liter A 1 P := 0.27-liter A 2 S := 0.5 liter A 2 T = 22 liter Volume of thickened primary sludge feed Volume of thickened secondary sludge feed Volume of A T A D 1 sludge removed by sampling Volume of A T A D 1 sludge measured in transfer tank Volume of A T A D 1 sludge remaining in transfer tank after pumping Volume of A T A D 1 sludge remaining in pipes after pumping Volume of A T A D 2 sludge removed by sampling Volume of A T A D 2 sludge measured in transfer tank T A : = ( 1 4 + 273)-K T A 1 := (52 4 -273)K Ambient air temperature at feeding time 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 := 999.22-L .:= 987.04-m kg 3 m kg f, := 983.30 — Y 2 3 m <fr20 := 998.2 kg m H := 0.735 AF1 :=.4.613-A F 2 := 0.931-liter min liter Density of water at ambient temp, at feeding time Density of water at A T A D 1 sludge temp, just before feeding Density of water at A T A D 2 sludge temp, just before feeding Density of water at 20 deg. C Relative Humidity (%) Average airflow into A T A D 1 Average airflow into A T A D 2 min 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 P P A T A 1 := 11587.5-Pa P P A T A 2 := 20706.8-Pa Partial pressure of water vapour at average ambient temp. Partial pressure of water vapour at average A T A D 1 temp. Partial pressure of water vapour at average A T A D 2 temp. mole := 6.022-10 23 R := 8.3144— joule K-mole 213 1. Calculation of sludge volumes in and out of reactors at operating temperatures. Influent = P + S Influent =25 -liter A T A D 1 Out = A1S + A I T A T A D 1 Out = 25.75 -liter A T A D 2 I n = A I T - A 1 T R - A 1 P A T A D 2 I n =24.73-liter A T A D 2 0 u t := A 2 T + A2S A T A D 2 0 u t =22.5-liter 2. Adjustment of sludge volumes to 20 deg. C base <l>o V I n = Influent +20 V A l O u t := A T A D 1 Out V A 2 I n := ATAD2In-V I n =25.03-liter +20 V A l O u t =25.46-liter V A 2 0 u t := A T A D 2 0 u t +20 V A 2 I n = 24.45 -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 of stable operation. Next, the volume of water lost in the saturated off-gas was calculated as follows: 3. Calculation of volume lost with saturated off-gas P P A T A H AF1 / „ kg G l l n = — - ( 0 . 0 1 8 - & R A T A mole/ kg G l l n = 0.089 day P P A T A 1 A F 1 I M O kg G10ut := (0.018- 6 G A 1 := R A T A l G l O u t =0.518 G l O u t - G l l n mole/ . k g day 20 G A 1 =0.43 Mass of water in aeration air Mass of water in air out from A T A D 1 liter day Mass of water lost in off-gas from A T A D 1 214 To 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) of 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 M e a n V A l O u t - M e a n V A l I n n A l B e = — 100 M e a n V A l I 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 of non-volatile solids in all streams was calculated as the difference between the concentration of total solids and the concentration of volatile solids The daily mass of 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 of 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 1 0 0 A l I n N V S B A 1 =-4.6 B A 2 = A20utNVS - A2hNVS ) 0 0 A 2 I n N V S B A 2 =-4.2 Percent error in solids balance around A T A D 1 Percent error in solids balance around A T A D 2 A 2 0 u t N V S - A l I n N V S + ( A l O u t N V S - A2InNVS) BSystem := -• 100 A l I n N V S 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 of volatile solids entering a tank and the mean mass of volatile solids exiting a tank. Example values from Oxygen Excess Experiment No . 2. A l l n V S := 434 — A2InVS = 333 -day day A l O u t V S := 348 — A 2 0 u t V S = 2 9 4 -day day VSDAl :- A ' O U l V S - A " n V S 100 A l l n V S V S D A l =-198 Percent volatile solids destruction in A T A D 1 T r _ _ A 2 0 u t V S - A2InVS , n n V S D A 2 := 100 A2InVS V S D A 2 =-11 7 Percent volatile solids destruction in A T A D 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 No . 2, percent PP := 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 of 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 of 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 of 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. EMassA2 := P A 1 + P A 2 + V A 2 E M a s s A 2 = 3 . 2 The total solids mass error around the system was calculated as the sum of 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 of 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. To this mean was added the mean of 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 — A 2 I n T N := 23.96-day day A l O u t T N := 2 5 . 1 4 — A 2 0 u t T N = 23.50—^-day day „ A , A l O u t T N - A l I n T N , n n B A 1 := 100 A l I n T N B A 1 =-9.3 Percent error in nitrogen balance around A T A D 1 „ n A 2 0 u t T N - A 2 I n T N , n n B A 2 := 100 A 2 I n T N B A 2 =-1.9 Percent error in nitrogen balance 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) BSystem := - 1 0 0 A l I n T N BSystem =-11.0 Percent error in nitrogen balance around entire system 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 No . 2, percent PP := 4.8 PA1 - 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 of 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 of 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- PA1 + V A 1 E M a s s A l = 8 . 2 The total nitrogen mass error around A T A D 2 was calculated as the sum of 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. EMassA2 := P A 1 + P A 2 + V A 2 E M a s s A 2 = 6 . 1 The total nitrogen mass error around the system was calculated as the sum of 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 of 12 consecutive days of 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- J L day A2InTP := 10.72- J L day A l O u t T P := 11.20- J L day A 2 0 u t T P := 10.55-day B A 1 := A l O u t T P - A l I n T P A l I n T P -100 B A 1 =-5.3 Percent error in phosphorus balance around A T A D 1 „ . „ A 2 0 u t T P - A2InTP B A 2 := 100 A2InTP B A 2 =-1.6 Percent error in phosphorus balance around A T A D 2 A 2 0 u t T P - A l I n T P + ( A l O u t T P - A2InTP) BSystem = ^ — 100 A l I n T P 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 TP 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 P A 2 = 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 = PS EMassIn = 4 . 9 The total phosphorus mass error around A T A D 1 was calculated as the sum of 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 +- PA1 +• 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 of 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. EMassA2 := P A 1 + P A 2 + V A 2 E M a s s A 2 = 8 . 8 The total phosphorus mass error around the system was calculated as the sum of 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 A P P E N D I X 3 T E M P E R A T U R E I N C R E A S E from MECHANICAL MIXING in W A T E R F I L L E D P I L O T S C A L E A T A D S 223 A P P E N D I X 3: Sample Calculations for prediction of 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 of 273 and 532 Watt respectively, using the slopes and intercepts calculated by linear regression, and the measured average airflows for each experiment. Both a predicted Delta T and the 95% confidence range are shown in the "Predictions of 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 OE2 experiment, A T A D 1. W : = - i ^ _ C : = K - 273 K mL :=-^L Unit conversions 1000 1 0 0 0 51 : = - 0 . 0 0 0 5 7 7 C - ^ ^ Slope of airflow/Delta T curve: low energy mech heat experiments mL 52 : = - 0 . 0 0 0 7 5 2 - 0 ^ ^ Slope of 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 of 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 P 2 : = 5 3 2 W Power input during high energy mech. heat experiments P = 2 8 0 W Power input for OE2 experiment, A T A D 1 T : = 1 6 C Average ambient temperature during OE2 experiment Calculation of 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 D T P 2 = 4 7 « C Predicted Delta T above ambient for 532 watts input 224 Calculation of Delta T above ambient for operating input power DTP2-DTP1 DT:= - ( P - P O + DTPl P2-P1 DT=28-C Calculation of predicted maximum operating temperature for given operating input power and airflow Tmax:=T + DT Tmax = 44 *C . , 225 s-0 1 1 o OH 03 (L> cn O N V O C O <—1 O N i—i O N o (N V O rH rH V O cn r- O N O N r- o O N o «o in CN m CN m 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 « la O H 6 0 T 3 <*> C/5 < U I H o O S" 6 0 rS I ° O 6 0 l-l rS 0 > n © « n « n © « n O O N O N 00 CO' vo' O N CO' K O <n O O © O © «n H O ON ON O cn C N H C N C N - — I — I C N C N C N C N « n « n > n o © i n © > n r~- r~ vo rn m od ro m 03 C/5 4 > « , ° , ° 0 4 > C I > 0 > H > < ; Z ; ; Z ; > H ; > , > H > H 0 > > I H O 1 J C J 6 0 O 6 0 *T3 o O © o «n •n O C N 00 00 ro ON ON >n <n V O V O m cn T T W-) o m o o «n o ON co r-' oo' ON vd ON oo' C O C N i—i cn 1—1 T f C N i—I 00 cn m cn «n oo CN cn cn C N 00 C N cn C N 00 cn o _ O P4 £ 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 r H c N c n ' ^ r > n v o t ~ ~ o o 226 p M i CM <D 00 ca Sa-les ro m ON c a \ p c j c j 1 .CJ 1*1 •CS R c j •»-» c j I cu CN TT rH O o o T f o T f O i n i CN co ON vo O N O ro ro CN o m m vd T f o o in r H o t> W 2 ro o o VO T f r~- in CN r H CO vo f **! 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O 60 *-l r S ^ CD r j n § 60 «> r 8 2P " 2 -a 60 f 60 CD O 60 M nd *T3 CD t> CD 60 CD T3 60 O Tt-r H CO m liO ON co T f i n T f T f co co r H T f T f T f CO VO vo f-CO CO r H 00 CN r H ON 00 CN CN O O VO 00 CN CN CN o o CN 60 "", 2 *' t T3 60 •a ra" 6 0 O 60 1-1 r S 3^ 53 0) U 60 <L> -O IS -9 U 60 CD T3 £- 60 -3 O 60 r 2 T3 ^ ts u » r 2 JH 60 I I S3 5 DH CD CO r H O r H VO VO vo r-i n m T f T f T f T f o o i n m CO VO CO r H T f T f r H 00 CO CN r- i n CO CO O 00 VO CO co ro cN c o W Q 0 229 A P P E N D I X 4 A E R A T I O N T E S T I N G 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 mm from the 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. 2 3 2 TABLE A4-1 : Detailed Aeration Test Results ATAD 1 70 % speed setting 919 r/min Airflow kLa20 C*20 SOTR Average Oxygen Transfer SOTR flow Efficiency (mg02 (mL/min) (l/s) (mg/L) (mg/L) (mg/L) /min) (%) 3728 0.0060 9.01 193 190 1042 25.1 0.0058 9.00 187 7660 0.0093 9.03 302 302 2141 19.4 0.0093 8.99 301 15382 0.0164 9.04 533 480 4298 15.3 0.0129 9.23 428 23314 0.0180 9.15 593 593 6517 12.5 0.0181 9.11 593 ATAD 1 100 % speed setting 1190 r/min Airflow kLa20 C*20 SOTR Average Oxygen Transfer SOTR flow Efficiency (mg02 (mL/min) (l/s) (mg/L) (mg/L) (mgT.) /rnin) (%) 3728 0.0088 9.11 287 290 1042 38.2 0.0090 9.06 292 7660 0.0131 9.05 425 424 2141 27.2 0.0131 8.98 422 15382 0.0203 9.19 670 667 4298 21.3 0.0201 9.19 664 23314 0.0250 9.07 818 819 6517 17.3 0.0254 8.96 821 233 Table A4-1: Detailed Aeration Results (cont.) ATAD 2 70 % speed setting 965 r/min Airflow kLa20 C*20 SOTR Average Oxygen Transfer SOTR flow Efficiency (mg02 (mL/min) (1/s) (mg/L) (mg/L) (mg/L) /min) (%) 0* 0.0009 8.99 29 28 N/A N/A 0.0009 8.90 28 3728 0.0073 9.07 238 233 1042 30.7 0.0070 9.08 229 7660 0.0111 9.08 364 355 2141 22.7 0.0105 9.10 345 15382 0.0156 9.14 513 500 4298 16.0 0.0146 9.25 487 23314 0.0197 9.25 657 648 6517 13.7 0.0193 9.18 939 ATAD 2 100 % speed setting 1234 r/min Airflow kLa20 C*20 SOTR Average Oxygen Transfer SOTR flow Efficiency (mg02 (mL/min) (1/s) (mg/L) (mg/L) (mg/L) /min) (%) 0* 0:0029 9.27 97 105 N/A N/A 0.0034 9.31 114 3728 0.0120 9.06 390 382 1042 50.3 0.0115 9.05 371 7660 0.0165 9.02 535 531 2141 34.0 0.0163 8.99 527 15382 0.0200 9.08 654 649 4298 20.7 0.0197 9.08 644 23314 0.0229 9.14 754 740 6517 15.6 0.0220 9.18 726 Measurements for 0 airflow were done with aerator impellors switched and are shown for interest only. 234 Figure A4-1 Airf low vs. S O T R 900 i 1 - n r — o ] 1 : 1 1 1 1 0 5000 10000 15000 20000 25000 Airflow (mL/min) •— ATAD 1 —•— ATAD 1 1 =i ATAD 2 — o ATAD 2 920 r/min 1190 r/min 965 r/min 1235 r/min Figure A4-2 Airflow vs. Oxygen Transfer Efficiency 60.0 0.0 4 1 1 1 1 1 0 5000 10000 15000 20000 25000 Airflow (mL/min) •— ATAD 1 —•— ATAD 1 ° ATAD 2 — -° ATAD 2 920 r/min 1190 r/min 965 r/min 1235 r/min 235 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 P H O S P H O R U S R E L E A S E D U E T O S A M P L E A C I D I F I C A T I O N Sample Calculation Based upon OE2 Experiment values, A T A D 2 VSIn := 17357-^8 Influent Mixed Sludge Volatile Solids liter TPIn = 473-5^- Influent Mixed Sludge Total Phosphorus liter TPperVSIn := ™5.-100 VSIn TPperVSIn =2 73 Phosphorus contained in Influent Mixed Sludge Solids, percent Estimated Maximum P released from solids remaining in centrifuged supernatant, -assuming worst case phosphorus content of 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 liter Phyd :=0.8 Fraction of polyphosphates hydrolyzed by acidification Preleased : = T P P e r V S m . VS-TSPperTP-Phyd 100 Preleased =28 liter A T A D 2 Sludge Characteristics ATAD2TP :=442-^i- Total phosphorus in A T A D 1 Sludge liter ATAD2TDP :=225-™^- Dissolved phosphorus in A T A D 1 Sludge liter ATAD2TSP : = ATAD2TP - ATAD2TDP ATAD2TSP =217 liter t mg Suspended phosphorus in A T A D 1 Sludge 237 A T A D 2 Sludge Characteristics (adjusted for maximum P release), Iteration 1 TDP : = ATAD2TDP - Preleased TDP = 197--m^-liter TSP :=ATAD2TP-TDP TSP =245--^-liter TSP TSPperTP := — ATAD2TP TSPperTP =0.55 First Iteration o f estimate o f P released Preleased : = JfPiEX^. VS-TSPperTP-Phyd 100 Preleased = 15 • - m i -liter A T A D 2 Sludge characteristics (adjusted for maximum P release), Iteration 2 TDP : = ATAD2TDP - Preleased TDP =210--m^ liter TSP = ATAD2TP - TDP TSP =232--*^-TSPperTP := liter TSP ATAD2TP TSPperTP =0.53 Second Iteration of estimate o f P released Preleased : = T P P e r V S I n . VS-TSPperTP-Phyd 100 Preleased = 14*-™ -^liter 238 A T A D 1 Sludge characteristics (adjusted for maximum P release), Iteration 3 TDP : = ATAD2TDP-Preleased . TDP =211-liter TSP . = ATAD2TP - TDP TSP =231*^-liter TSPperTP : = TSP ATAD2TP TSPperTP =0.52 Third Iteration of estimate of P released Preleased := T P P e r V S m . VS-TSPperTP-Phyd 100 me Preleased = 14 •—— liter Calculation o f maximum expected error in dissolved P measurements due to hydrolyzing o f suspended phosphorus in supernatant samples. E D P : =/ATAD2TDP-TDP^ 1 0 0 I ATAD2TDP EDP =6.4 Calculation o f maximum expected range in suspended P in Volatile Suspended Solids ATAD2VS := 12331 mg liter ATAD2VSS := 11846-^ Estimate from Appendix 6 calculations liter M i n ; /ATAD2TSP \ 1 0 0 \ ATAD2VS / Min =1.76 Max :=[ T S ? 1-100 \ATAD2VSS/ Max = 1.95 Predated := ATAD2TSP \ \ATAD2VSS/ Predicted = 1.83 239 Appendix 5 : Calculation of Phosphorus Release due to Sample Acidification Supernatant Solids Content Sample Vol. Tare Dry Fired TS NVS VS (ml) (g) (g) (g) (mg/L) (mg/L) (mg/L) Total 26.0 40.0135 40.4840 40.0777 18096 2469 15627 Total 29.5 39.6745 40.2532 39.7056 19617 1054 18563 Total 31.5 43.2336 43.8086 43.3085 18254 2378 15876 Sup 28.5 39.9209 39.9883 39.9349 2365 491 1874 Sup 47.5 79.7985 79.9148 79.8219 2448 493 1956 Sup 46.0 81.2319 81.3430 81.2540 2415 480 1935 Diss 50.0 77.6096 77.6638 77.6294 1084 396 688 Diss 50.0 81.5278 81.5748 81.5436 940 316 624 Total Sample Averages Total Dissolved Suspended TS 18656 1012 17644 VS 16689 656 16033 NVS 1967 356 . 1611 VS/TS 0.89 0.65 0.91 Supernatant Sample Averages Total Dissolved Suspended TS 2410 1012 1398 VS 1921 656 1265 NVS 488 356 132 VS/TS 0.80 0.65 0.91 Probable E r r o r in 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 released from solids = (%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 Experiment TVS TP TP/TVS Maximum Additional P released from solids (mg/L) (mg/L) (%) (mg/L) OEl 17294 309 1.79 28 OE2 17357 473 2.73 24 OD 18398 438 2.38 26 OS 16558 432 2.61 Measured values of P in ATADs Exp. ATAD 1 ATAD 2 TP TDP TSP TSP/TP TP TDP TSP TSP/TP (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) OEl 296 152 144 0.49 330 185 145 0.44 OE2 451 215 236 0.52 442 225 217 0.49 OD 410 269 141 0.34 405 311 94 0.23 OS 411 183 228 0.55 430 197 233 0.54 241 Values of P in ATADs adjusted for estimated P release from suspended solids Iteration 1 Exp. ATAD 1 ATAD 2 TP TDP TSP TSP/TP TP TDP TSP TSP/TP (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) OE2 451 187 264 0.58 442 197.42 244.58 0.55 OD 410 245 165 0.40 405 286.91 118.09 0.29 OS 411 157 254 0.62 430 170.6 259.4 0.60 ATAD 2 Iteration 2 Exp. P from TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mg/L) (mg/L) OE2 15 442 210 232 0.53 OD 7 405 304 101 0.25 OS 16 430 181 249 0.58 ATAD 2 Iteration 3 Exp. P from TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mg/L) (mg/L) OE2 14 442 211 231 0.52 OD 6 405 305 100 0.25 OS 15 430 182 248 0.58 ATAD 2 Iteration 4 Exp. Pfrom TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mg/L) (mg/L) OE2 14 442 211 231 0.52 OD 6 405 305 100 0.25 OS 15 430 182 248 0.58 242 ATAD 1 Iteration 2 Exp. P from TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mg/L) (mg/L) OE2 16 451 199 252 0.56 OD 10 410 259 151 0.37 OS 16 4.11 167 244 0.59 ATAD 1 Iteration 3 Exp. P from TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mgT.) (mg/L) OE2 15 451 200 251 0.56 OD 9 410 260 150 0.37 OS 16 411 167 244 0.59 ATAD 1 Iteration 4 Exp. Pfrom TP TDP TSP TSP/TP SS (mg/L) (mg/L) (mg/L) (mg/L) OE2 15 451 200 251 0.56 OD 9 410 260 150 0.37 OS 16 411 167 244 0.59 Estimated TSP in VS for Thickened Secondary Sludge Exp. VS TP TDP TSP TSP/VS (mg/L) (mgT.) (mg/L) (mg/L) OE1 18476 706 13.1 693 3.75 OE2 18505 805 9.6 795 4.30 OD 17938 748 15.2 733 4.09 OS 19440 759 5.0 754 3.88 243 Therefore, the maximum error expected due to acidification of the centrifuged supernatant would be Exp. Error Measured TDP Expected Error in TDP from acidification (%) ATAD 1 ATAD 2 ATAD 1 ATAD 2 ATAD 1 ATAD 2 (mg/L) (mg/L) (mg/L) (mg/L) OE2 15 14 215 225 7.15 6.42 OD 9 6 269 311 3.27 1.91 OS 16 15 183 197 8.55 7.74 Exp. Measured VS Estimated VSS TSP /VS (%) ATAD 1 ATAD 2 ATAD 1 ATAD 2 ATAD ATAD (mg/L) (mg/L) (mg/L) (mg/L) 1 2 OEl 14243 12770 13683 12268 1.01 1.14 OE2 13998 12331 13448 11846 1.69 1.76 OD 14945 13057 14358 12544 0.94 0.72 OS 14024 13496 13473 12966 1.63 1.73 Exp. % calc TSP/VSS % TSP/calc VSS ATAD 1 ATAD 2 ATAD 1 ATAD 2 (%) (%) (%) (%) OEl 1.05 1.18 OE2 1.87 1.95 1.75 1.83 OD 1.04 0.80 0.98 0.75 OS 1.81 1.91 1.69 1.80 244 APPENDIX 6 RECYCLE CALCULATIONS 245 A P P E N D I X 6 - R E C Y C L E C A L C U L A T I O N S Example Calculation based upon Nitrogen Values. Calculation for C O D and Phosphorus are similar. "High" Condition "Low" Condition O E l A T A D 2 Volatile Solids VSh:= 12331-^-liter Total Kjeldahl Nitrogen O D A T A D 2 VS1 :=T3057-m^-liter 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) VSSH = 11846 •-m^-liter Suspended T K N VSSL :=VS1(1 - FDVS) VSSL = 12544 liter TSKNh :=TKNh - TDKNh TSKNh =516--^-liter T K N per mg Suspended Solids TSKNh TKNperVSSh : = VSSH TSKN1: = TKN1 - TDKN1 TSKN1 = 311-^1-liter TKNperVSSl TSKN1 VSSL TKNperVSSh =0.044 TKNperVSSl =0.025 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 liter RSh := 3000 i^L 20 percent of digester influent solids returned to plant 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-^i - TKNl = 19-^i-liter liter Based on 20 percent suspended solids return to plant: TKNh :=RSh- TKNperVSSh TKN1 : = RSh-TKNperVSSl TKNh = 1 3 1 - - ^ TKN1=74--^-' liter liter Dissolved TKN DTKNh := VSSful-DTKNperVSSh DTKN1 := VSSfulDTKNperVSSl DTKNh=575-^i- DTKN1 = 865- i^ . liter " liter 247 APPENDIX 6 - RECYCLE CALCULATIONS Example of Typical Field Solids Concentrations ATAD TS In ATAD VS In ATAD VS Destruction ATAD VS Out ATAD TS Out 30000 mg/L 25000 mg/L 40 % 15000 mg/L 20000 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 in A T A D Sludge during experiments Experiment VS Estimated VSS (mg/L) (mg/L) OEl 12770 12268 OD 13057 12544 OS 13496 12966 OE2 12331 11846 248 APPENDIX 6 - RECYCLE CALCULATIONS Estimate of COB7VSS during experiments: ATAD 2 TCOD = Total COD PCOD = Particulate COD SCOD = Soluble COD Experiment TCOD SCOD PCOD/ SCOD/ VSS VSS (mg/L) (mg/L) (mg/mg) (mg/mg) OD 17941 1639 1.30 0.13 OS 20543 714 1.53 0.06 OE2 18301 623 1.49 0.05 Estimate of C O D range in typical A T A D Supernatant Recycle 5 percent solids return with supernatant ATAD Low Air ATAD High Air PCOD SCOD TCOD 975 1960 2935 1119 789 1908 20 percent solids return with supernatant ATAD Low Air ATAD High Air PCOD SCOD TCOD 3899 1960 5859 4477 789 5266 Supernatant COD Recycle Range 1908 to 5859 249 APPENDIX 6 - R E C Y C L E CALCULATIONS Estimate of Nitrogen/VSS during experiments: ATAD 2 T K N = Total Kjeldahl Nitrogen TPKN = Total Particulate T D K N = Total Dissolved Kjeldahl Nitrogen Kjeldahl Nitrogen Experiment T K N T D K N 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 A T A D Low Air A T A D High Air P T K N D T K N T K N 19 865 883 33 575 608 20 percent solids return with supernatant A T A D Low Air A T A D High Air PTKN D T K N T K N 74 865 939 131 575 706 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 TPP = Total Particulate TDP = Total Dissolved Phosphorus Phosphorus Experiment TP TDP TDP/ TPP/ VSS VSS (mg/L) (mg/L) (mg/mg) (mg/mg) OEl 330 185 0.01 0.02 OD 405 311 0.01 0.02 OS 430 197 0.02 0.02 OE2 442 225 0.02 0.02 Estimate of Phosphorus range in typical ATAD Supernatant Recycle 5 percent solids return with supernatant ATAD Low Air ATAD High Air 20 percent solids return with supernatant TPP TDP TP 6 372 378 14 285 299 TPP TDP TP 22 372 394 55 285 340 ATAD Low Air ATAD High Air Supernatant TP Recycle Range 299 to 394 Supernatant TDP Recycle Range 285 to 372 251 APPENDIX 6 - RECYCLE CALCULATIONS Influent Sewage Flow 100 L Recycle Flow 1 L ATAD Digestion Recycle Effect on Plant Influent Parameter Influent Recycle Range New plant influent Load Change Cone. Low High Low High Low High (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (%) (%) SS 220 1000 4000 228 257 5 18 COD 500 1908 5859 514 553 4 12 TKN 20 608 939 26 29 30 47 TDKN 8 575 865 14 16 72 108 NOx 0 0 10 0 0 TP 4 299 394 7 8 75 99 TDP 3 285 372 6 7 95 124 Mesophilic Anaerobic Digestion Recycle Effect on Plant Influent Parameter Influent Recycle Range New plant influent Load Change Cone. Low High Low High Low High (mg/L) (mg/L) (mg/L) (mg/L) (mg/L) (%) (%) SS 220 143 7772 219 295 1 35 COD 500 1230 4565 507 540 2 9 TKN 20 441 1080 24 30 22 54 NH3 8 253 853 10 16 32 107 TP 4 99 190 5 6 TDP 3 63 143 4 4 21 48 Mesophilic Aerobic Sludge Digestion Recycle Effect on Plant Influent Parameter Influent Recycle Range New plant influent Load Change Cone. Low High Low High Low High (mg/L) (mgT.) (mg/L) (mg/L) (mg/L) (%) (%) SS 220 46 11500 218 332 0 52 COD 500 228 8140 497 576 0 16 TKN 20 10 400 20 24 1 20 TP 4 19 241 4 6 5 60 TDP 3 3 64 3 4 1 21 252 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 00:0 £6/Z.I/l 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 f o a cct Q 00^ 0 £6/11/1 o o o o o o o o o. o C S o o C O repnajod noponpa^ nopupixo 254 • r i i i i (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 00^0 £6/51/1 (WO £ 6 / H / I 00-0 £6/£l /T 00 :0 £6/31/1 00:0 £6/11/1 o o co o o o o O O o o o o CO (\va) iBnn3)0<j uoponps^ uopEpixQ 255 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/£ 00=0 £6lvl£ 00-0 £6/£/£ 00=0 £6/Z/£ 00 :0 £6/t/£ f 1 to Q 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 P o © o o CS o o ro o o TT o o o o VO (Ata) pjpnajod noponpa^ nopBpixo 256 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 <N O O O O O O m <n o o NO (\m) nnjuajoj noponpa^ uoqBpreo 257 <N O oo vo 8 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 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 C N O © o o o o C S o © cn © o (\xa) repnajod noponps^ uopepixQ. 258 q/Sm) noijBJjn3ono3 uaSAxo paAjossiQ 00 VO 1 1 1 / / / t \> j t o o \ 'i f ? o o o o \ i o o o o o c I i J 1 < 1 » I ( \\ > ° l r f t I 7 1 [ '( , ° i i~ £ • [ 1 1 t \ oo oo — oo ,_rs_^_-,_ . o o 00-0 £6/81/^ 00-0 Z6/LI/V 00-0 £6/9Vv 00-0 Z6/91/V 00-0 £6/vl/v 00-0 £6/£l/v s 00:0 £6/Zl/v p ! o 00:0£6/II/fr S Q 00-0 £6/0I/t> 00=0 £6/6/* 00-0 £6/8/t> 00-0£6/L/v . 00^ 0 £6/9/f 00=0 £6/S/fr o o o o o o o Ifl O VS O V> (Ain) iBijn3jO(j noponpa^ aopcpixQ 259 1/8ui) noijBJ}U3oao3 usgAxo paAjossia CO § u o CQ o 8* o 00^ 0 £6/81/5 00:0 E6/Z.I/S 00=0 £6/91/5 00=0 £6/91/9 00"-0 £6M/5 00=0 £6/£\/9 00-0 £611119 J3 00=0 £6/11/5 H ! 00=0 £6/01/5 S I Q OtTO £6/6/5 00=0 £6/8/5 00=0 £6/L/9 00:0 £6/9/5 00^ 0 £6/5/5 OtTO £6/tV5 00=0 £6/£/5 a> Xl o cd J2 o CD o & o O Q O P CJ t to o o o o o o o i n o o o o u - i o — cs o c s (Ain) repaajoj uoponpatf uopcpixQ 260 1/8ra) uoijBimaouoQ uagAxQ, paAiossifj vo TJ- ts o —1—n — 1 —n - i — i — ' 1 r 1 r - —1 1 -i 1 1 .... j _ '* 1 h { 1 r / 1 I \ \, v\ t / O i . ( i { y ^ O * ( i ] \ I V It O -if-J f O t { V S i F ) •f-r-r O t • J / i 1 • • " t i \\ o U o • o o • D o • O 00=0 £6/81/5 (WO £6/Z,I/S 00=0 £6/91/5 00=0 £6/51/5 00:0 £6/W/5 00-0 £6/£l /5 00-0 £6/31/5 S 00=0 £6/11/5 P f tWO £6/01/5 I ^—' <D « Q 00=0 £6/6/5 00:0 £6/8/5 00-0 £6/Z./5 00:0 £6/9/5 00=0 £6/5/5 00^ 0 £6/t>/5 00=0 £6/£/S o o o o o o o m o >n wi o vt © o i i (A r a) iBpnajoj noponpa^ uopupreo 261 

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