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Enhanced anaerobic digestion of combined wastewater sludges through solubilization of waste activated… Knezevic, Zorica 1993

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ENHANCED ANAEROBIC DIGESTION OF COMBINED WASTEWATER SLUDGESTHROUGH SOLUBILIZATION OF WASTE ACTIVATED SLUDGEbyZORICA KNEZEVICB.Sc. (Civil Engineering), The University of Belgrade, 1984A THESIS SUBMITTED IN PARTIAL FULFILLMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF APPLIED SCIENCEinTHE FACULTY OF GRADUATE STUDIES(Department of Civil Engineering)We accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAJanuary 1993© Zorica Knezevic, 1993In presenting this thesis in partial fulfilment of the requirements for an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature)Department of  Civil EngineeringThe University of British ColumbiaVancouver, CanadaDate  ,7,4/111),IP Y /3 103DE-6 (2/88)iiABSTRACTPilot-scale research on enhancement of anaerobic co-digestion of combinedprimary and secondary sludges was performed, using a low-level alkaline solubilizationprocess for the secondary sludge. Research was conducted in two phases: the first phaseinvestigated chemical dosages of calcium hydroxide and sodium hydroxide andmechanical mixing times for waste activated sludge (WAS) solubilization; the second,pilot-scale phase monitored the performance of anaerobic digestion, using mixtures ofsolubilized WAS and primary sludge as a feed.The first phase results showed that solubilization of WAS can be effectivelyperformed using both chemicals separately. However, for the same chemical dosage andanoxic mixing time, sodium hydroxide was more effective in WAS solubilization.Performance of three pilot-scale units, one control and two experimental (expCa(OH)2 and exp NaOH) units was monitored in the second phase. Each anaerobic unitwas 160 L in liquid volume and operated as a single-stage, high-rate system; operatingtemperature was 35°C. The ratio of WAS to primary sludge was 65/35 by volume; achemical dose of 15 meq/L and anoxic mixing time of 5 hours was applied for WASsolubilization. All parameters were kept constant through the whole study except solidsretention time (SRT); SRT was gradually decreased from 25 to 10 days, in 5 dayincrements, i.e. 4 runs.The second phase results indicated better digester performance of bothexperimental units, with exp NaOH outperforming lime. Volatile mass reduction wasillindependent of SRT and the best overall VSS reduction was observed in the exp NaOHunit. However, the improvement in overall VSS reduction was attributed to thesolubilization process itself, and not necessarily to better digester performance per se.The addition of sodium hydroxide to the WAS allowed for a decrease of SRT from 25to 10 days, without losing VSS reduction efficiency.Carbon removal (in terms of total and soluble COD removal) actually increasedwith a decrease in SRT and the highest carbon removal was achieved in the exp NaOHunit. Better carbon removal was also reflected in a higher methane content of the gas.The effect of solubilizing the WAS, prior to digestion, was also reflected in a higher unitgas production (L/kg VSS reduced) in both experimental units.Results obtained in the second phase proved that WAS pretreatment enhancedvolatile mass reduction, total and soluble COD removal, gas quality and unit gasproduction in the anaerobic digestion of mixed wastewater sludges. Also, there was nomajor effect on effluent quality in terms of nitrogen, phosphorus (except for lowersoluble phosphorus in the exp Ca(OH)2 unit), VFA and TOC concentrations. Based onthe results obtained in this study, it is strongly recommended that a full scale evaluationbe undertaken of combining pretreated WAS with primary sludge in a high-rate, single-stage anaerobic digester and implement a complete cost-benefit analysis of such.ivTABLE OF CONTENTSpageABSTRACT ^  iiTABLE OF CONTENTS ^  ivLIST OF TABLES  ixLIST OF FIGURES ^  xiiiACKNOWLEDGEMENTS ^  xv1. INTRODUCTION ^  11.1. PROJECT NEED ^  11.2. RESEARCH OBJECTIVES ^  41.3. THESIS ORGANIZATION  52. LITERATURE REVIEW^  72.1. ANAEROBIC DIGESTION ^  72.2. ADVANTAGES OF ANAEROBIC TREATMENT ^ 82.3. DISADVANTAGES OF ANAEROBIC TREATMENT^ 92.4. MICROBIOLOGY OF ANAEROBIC TREATMENT^ 102.5. METHANE PRODUCTION AND INHIBITION  15V2.6. ENVIRONMENTAL REQUIREMENTS ^  182.6.1. Temperature ^  182.6.2. Anaerobic Conditions  192.6.3. Biological Nutrients ^  202.6.4. pH and Alkalinity  202.6.5. Toxic Materials ^  242.7. KINETICS OF METHANE FORMATION AND BIOMASSGROWTH ^  282.8. GAS COMPOSITION AND USE ^  313. EXPERIMENTAL SET-UP AND ANALYTICAL TECHNIQUES ^ 333.1. SLUDGE SOURCE ^  333.2. LABORATORY SET - UP  333.3. DIGESTER OPERATION ( Phase II) ^  363.4. EXPERIMENTAL SEQUENCE ( Phase II)  373.5. ANALYTICAL AND SAMPLING TECHNIQUES ^ 383.5.1. Solids ^  393.5.1.1. Total Suspended and Total Volatile SuspendedSolids ^  393.5.1.2. Total Solids and Total Volatile Solids ^ 403.5.2. pH and Temperature ^  403.5.3. Chemical Oxygen Demand  41vi3.5.4. Total Organic Carbon ^  423.5.5. Ammonia Nitrogen  423.5.6. Total Kjeldahl Nitrogen ^  423.5.7. Orthophosphate Phosphorus  433.5.8. Total Phosphorus ^  433.5.9. Volatile Fatty Acids  433.5.10. Gas Composition ^  443.5.11. Dewaterability  443.5.12. Oxidation - Reduction Potential ^  443.5.13. Sample Preservation ^  453.6. SAMPLING FREQUENCY  464. PHASE I - RESULTS AND DISCUSSION ^  474.1. INTRODUCTION ^  474.2. RESULTS AND DISCUSSION ^  484.2.1. Solids ^  484.2.2. pH  494.2.3. Chemical Oxygen Demand ^  524.2.4. Total Organic Carbon  554.2.5. Phosphorus ^  584.2.6. Nitrogen  594.3. SUMMARY ^  66VII5. PHASE II RESULTS AND DISCUSSION ^  675.1. INTRODUCTION ^  675.2. SOLUBILIZATION OF WASTE ACTIVATED SLUDGE ^ 685.2.1. Solids ^  685.2.2. Chemical Oxygen Demand ^  715.2.3. Total Organic Carbon  725.2.4. Nitrogen ^  755.2.5. Phosphorus  765.3. DIGESTER PERFORMANCE^  795.3.1. pH and Temperature  795.3.2. Oxidation - Reduction Potential ^  825.3.3. Solids ^  835.3.4. Carbon Content and Removal ^  895.3.5. Gas production and composition  935.3.6. Nitrogen ^  985.3.7. Phosphorus  1005.3.8. Volatile Fatty Acids ^  1035.3.9. Sludge Dewaterability  1055.4. SUMMARY ^  1056. CONCLUSIONS AND RECOMMENDATIONS ^  1126.1. CONCLUSIONS ^  112viii6.2. RECOMMENDATIONS ^  116REFERENCES ^  118APPENDICES ^  123Appendix A: Phase I - WAS Solubilization ^  123Appendix B: Phase II - WAS Solubilization  130Appendix C: Phase II - Digester Performance: Solids, Gas Production andMethane Content ^  145Appendix D: Phase II - Digester Performance: Carbon, Nitrogen andPhosphorus ^  182Appendix E: Phase II - Digester Performance: Volatile Fatty Acids,Dewaterablity and Environmental Conditions ^ 209ixLIST OF TABLESpageTable 3.1.^Digester Experimental Sequence ( Phase II) ^ 38Table 3.2.^Sample Preservation and Storage Techniques  45Table 4.1.^Percent VSS Destruction in WAS for Sodium HydroxideAddition ^  49Table 4.2.^Percent Soluble COD in WAS ^  54Table 4.3.^Percent PO4 - P in Soluble TP  58Table 4.4.^Percent Soluble TP in WAS ^  59Table 4.5.^Percent NH4 - N in Soluble TKN  63Table 4.6.^Percent Soluble TKN ^  63Table 5.1.^Average Percent of VSS Destruction During Solubilization ^ 70Table 5.2.^Average wrcent of Soluble COD in WAS With and WithoutPretreatment ^  72Table 5.3.^Average Concentration of Soluble TKN (mg/L) in WAS With andWithout Pretreatment ^  75Table 5.4.^Average Concentration of NH4-N (mg/L) in WAS With andWithout Pretreatment ^  76Table 5.5.^Average Percent of PO4-P in Soluble TP With and WithoutPretreatment  77Table 5.6.^Average Number of Sodium Bicarbonate Additions per SRTSequence, to Maintain Desired pH Range ^ 81Table 5.7.^Average Values of Digester VSS Reduction (%) ^ 86Average Values of Overall VSS Reduction (%) ^ 87Average Effluent Concentrations of Inorganic Material (mg/L) ..^89Carbon Removal (kg/day): COD basis ^  90Average TOC Concentrations (mg/L)  92Average Volume of Gas Produced (L/day) Corrected to 20°C . . . 93Average Volume of Gas Produced per Mass of VSS Reduced inDigesters (L/kgVSSreduced) Corrected to 20°C ^ 95Table 5.8.Table 5.9.Table 5.10.Table 5.11.Table 5.12.Table 5.13.Table 5.14.Table 5.15.Table 5.16.Table 5.17.Table 5.18.Table 5.19.Table 5.20.Table 5.21.Table 5.22.Volume of Methane Produced per Mass of Total COD Removed(L/kg CODt) ^  95Average Composition of Digester Gas (%) ^ 97Average Percent of Effluent Soluble TKN in Total TKN ^ 98Average Effluent Concentrations of Soluble TKN (mg/L) ^ 99Average Percent of Effluent NH4+-N in Soluble TKN ^ 99Average Effluent Percent of PO4-P in Soluble TP ^ 100Average Effluent Concentrations of PO 4-P (mg/L) ^ 101Average Influent VFA Concentrations (mg/L) as Acetic Acid andAverage Percent of Acetic Acid in Influent^ 104Average Effluent VFA Concentrations (mg/L) as Acetic Acid andAverage Percent of Acetic Acid in Effluent ^ 104Table 5.23. Summary of Digester Performance and Effluent Quality ^ 108Al: Total Solids (mg/L) ^  123A2: Total Suspended Solids (mg/L) ^  123A3: Total Volatile Suspended Solids (mg/L)  124xiA4: Total Volatile Solids (mg/L) ^  124A5: Total Organic Carbon (mg/L)  125A6: pH ^  125A7: Soluble CODs (mg/L) ^  126A8: Total CODt (mg/L)  126A9: NH4 - N (mg/L) ^  127A10: PO4 - P (mg/L)  127All: Soluble TPs (mg/L) ^  128Al2: Total TPt (mg/L)  128A13: Soluble TKNs (mg/L) ^  129A 14: Total TKNt (mg/L)  129Bl: Total Solids and Total Volatile Solids (mg/L) ^  130B2: Total Suspended Solids and Total Vlatile Suspended Soldis (mg/L) ^ 133B3: Soluble CODs; Total CODt; Totla Organic Carbon (mg/L) ^ 136B4: NH4 - N; Soluble TKNs; Total TKNt (mg/L) ^  139B5: PO4 - P; Soluble TPs; Total TPt (mg/L)  142Cl: Solids: Total Solids (mg/L) ^  145C2: Solids: Total Volatile Solids  152C3: Solids: Total Suspended Solids (mg/L) ^  159C4: Solids: Total Volatile Suspended Solids (mg/L)  166C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35°C andCorrected to T=20°C ^  173xiiC6: Methane Content (%) and Average Production per Run (L/day) Corrected toT=20°C ^  180Dl: Carbon: Influent and Effluent Soluble COD (mg/L) ^ 182D2: Carbon: Influent and Effluent Total COD (mg/L)  185D3: Carbon: Total Organic Carbon (mg/L) ^  188D4: Nitrogen: NH4 - N (mg/L) ^  191D5: Nitrogen: Soluble TKN (mg/L)  194D6: Nitrogen: Total TKN (mg/L) ^  197D7: Phosphorus: PO4 - P (mg/L)  200D8: Phosphorus: Soluble TP (mg/L) ^  203D9: Phosphorus: Total TP (mg/L)  206El: Environmental Conditions: pH and Temperature (°C) ^ 209E2: Environmental Conditions: Oxidation-Reduction Potential (mV) ^ 216E3: Volatile Fatty Acids (mg/L) ^  217E4: Dewaterablity: Capillary Suction Time (sec) ^  220LIST OF FIGURESpageFigure 2.1. Categories of Metabolically Distinct Bacteria in the MethaneFormation ^  11Figure 2.2. Methanogens: a) Methanobacterium and b) Methanosaracina . . . . 12Figure 2.3. Scheme for the Reduction of CO2 to CH4 and Site of ATPSynthesis ^  14Figure 2.4. Tentative Scheme for the Formation of Methane and CarbonDioxide from Acetate ^  14Figure 2.5. General Effect of Salts or Other Materials on BiologicalReactions ^  25Figure 3.1. UBC Pilot Plant Configuration ^  34Figure 3.2. Phase II Experimental Set-up  35Figure 4.1. Phase I Experimental Set-up ^  47Figure 4.2. Phase I - Solubilization of WAS: Volatile Suspended Solids(mg/L) ^  50Figure 4.3. Phase I - Solubilization of WAS: Total Solids (mg/L) ^ 51Figure 4.4. Phase I - Solubilization of WAS: pH ^  53Figure 4.5. Phase I - Solubilization of WAS: Soluble COD (mg/L) ^ 56Figure 4.6. Phase I - Solubilization of WAS: Total Organic Carbon (mg/L)^57Figure 4.7. Phase I - Solubilization of WAS: Soluble TP (mg/L) ^ 60Figure 4.8. Phase I - Solubilization of WAS: PO 4 -P (mg/L)  61Figure 4.9. Phase I - Solubilization of WAS: NH 4-N (mg/L) ^ 64Figure 4.10. Phase I - Solubilization of WAS: Soluble TKN (mg/L) ^ 65Figure 5.1.Figure 5.2.Figure 5.3.Figure 5.4.Figure 5.5.Figure 5.6.Figure 5.7.Figure 5.8.Figure 5.9.Figure 5.10.Figure 5.11.Figure 5.12.Figure 5.13.Figure 5.14.Figure 5.15.Figure 5.16.Figure 5.17.xivPhase II - Solubilization of WAS: Total Solids (mg/L) ^ 69Phase II - Solubilization of WAS: Total Volatile Solids (mg/L) ^ 69Phase II - Solubilization of WAS: Volatile Suspended Solids (mg/L) 71Phase II - Solubilization of WAS: Soluble COD (mg/L) ^ 73Phase II - Solubilization of WAS: Total Organic Carbon (mg/L) ^ 73Phase II - Solubilization of WAS: Correlation Between TOC -soluble COD for Ca(OH) 2 Addition to WAS ^ 74Phase II - Solubilization of WAS: Correlation Between TOC -soluble COD for NaOH Addition to WAS ^ 74Phase II - Solubilization of WAS: Release of Phosphorus: SolubleTotal Phosphorus (mg/L) ^  77Phase II - Solubilization of WAS: Release of Phosphorus: PO 4-P(mg/L) ^  78Phase II - Performance of Digesters: Effluent pH Values ^ 81Phase II - Performance of Digesters: Effluent Temperatures (°C)^82Phase II - Performance of Digesters: Influent and EffluentConcentrations of Volatile Suspended Solids (mg/L) ^ 85Phase II - Performance of Digesters: Influent and EffluentConcentrations of Soluble COD (mg/L) ^  92Phase II - Performance of Digesters: Average Gas Production (Lof gas/kg VSS reduced) ^  96Phase II - Performance of Digesters: Methane Content (%) ^ 97Phase II - Performance of Digesters: Effluent Concentrations ofSoluble TP (mg/L) ^  102Phase II - Performance of Digesters: Sludge Dewaterability . . . 106XVACKNOWLEDGEMENTSI am sincerely grateful to my research supervisor Professor D.S. Mavinic for hisunderstanding, patience and guidance during the course of this research. It has been agreat pleasure to work with Dr. Mavinic.I am also thankful to my father, my brother and his lovely family for theirencouragement and support.I wish to thank Susan Harper, Paula Parkinson and Jufang Zou for their help,support, laughs and good times.I am grateful to my friend Angus Chu who has been an integral part of thisproject, from dealing with sludge to many hours of productive discussion.Last, but not least, I wish to thank all my friends here in Canada and elsewherein the world for their support.11. INTRODUCTION1.1. PROJECT NEEDSewage sludge is produced as a byproduct of primary and secondary wastewatertreatment. Materials removed during the treatment process are usually contained withina sludge which must be further treated before it can be discharged.The disposal of sludge has been and continues to be one of the most difficult andexpensive problems in the field of wastewater engineering. According to a recent reportby the Water Pollution Control Federation, one of the most critical areas of waterpollution control is the treatment and disposal of municipal sludges [Gloyna, 1982]. Thesame report states that sludge quantities have increased in recent past, but the options forsludge disposal have been severely restricted due to regulations enacted to protect theenvironment from undesirable residual materials.The importance of sludge disposal is further emphasized when economicconsiderations are taken into account. Cost of sludge management (including sludgehandling within a plant, transport to a disposal site and disposal of the residue) comprise35 percent of the capital costs and 55 percent of the annual operation and maintenancecosts of a wastewater treatment plant [Hasit and Vesilind, 1981 and Hasit et al, 1981].Most of the past studies of sludge treatment and disposal have been conventionallyoriented whereby waste activated sludge was stabilized aerobically and primary sludgeanaerobically. Recent studies [Mavinic and Anderson, 1990] investigated the possibility2of treating two types of sludges with one type of stabilization process. The most commonform of sludge stabilization is anaerobic digestion, as it generates the useful byproduct -methane. Anaerobic digestion is very successfully used for stabilization of primarysludge, but efficiency of the process decreases if waste activated sludge is included as aportion of digester influent, as reported by Mavinic and Anderson [1990]. The researchshowed a decrease in digester operational efficiency (with respect to volatile massreduction and gas production, both in terms of overall volume and volume produced perCOD destroyed) with the addition of waste activated sludge over the control digester,which received only primary sludge. It has been estimated that up to 65 percent (byvolume) of the waste sludge generated at a conventional treatment plant is wasteactivated sludge.Waste activated sludge (WAS) is not a good substrate for fermenting bacteria asvaluable substrate is contained within the bacterial cell membrane. This membrane mustbe ruptured for this material to become available for fermentation. For this reason,researchers have been examining different methods with which to accelerate theavailability of substrate from WAS. This can be accomplished by physical, chemical orphysicochemical treatment.Haugh et al [1978] conducted a laboratory study to evaluate the effect of thermalpretreatment on the digestibility and the methane production of WAS. They demonstratedthat thermal pretreatment improves methane production and increases biodegradability.Stuckey and McCarty [1978 and 1984] investigated the effects of thermochemicaland thermal pretreatment of WAS. They used hydrochloric acid, sodium hydroxide and3calcium hydroxide at various temperatures up to 250°C. They concluded thatthermochemical pretreatment has an inhibitory effect at temperatures over 200°C and thatthe addition of hydrochloric acid and sodium hydroxide has only a marginal effect onsolubilization.Rajan et al [1989] showed that low-level alkaline pretreatment of WAS cansolubilize over 45 percent of particulate COD. Applied chemicals were sodium hydroxideand calcium hydroxide, with sodium hydroxide being more effective.Ray et al [1990] examined effects of low-level alkaline pretreatment of WAS onanaerobic digestion. 20 meq/L of sodium hydroxide or calcium hydroxide were addedto WAS and after 24 hours of anoxic mixing, 1-L laboratory scale high-rate digesterswere fed. This study showed that both sodium hydroxide and calcium hydroxidepretreatment improved anaerobic digestion, with sodium hydroxide being better. Gasproduction, VS removal and COD removal were improved. In addition, it was estimatedthat solids retention time could be significantly decreased (from 20 days to 7.5 days) withequivalent digester performance.In summary, any new or modified process that improves WAS stabilization priorto anaerobic digestion may contribute to improved plant operations, as well as reduceoverall plant operating costs [Ray et al, 1990].41.2. RESEARCH OBJECTIVESIn 1990, a research program was proposed to the Greater Vancouver RegionalDistrict (GVRD) and Science Council of British Columbia; this proposal would examinethe benefits of the WAS solubilization process on anaerobic digestion. This processwould be demonstrated at pilot-scale, the results of which would be more readily usableto estimate and optimize full-scale operating characteristics when full secondary leveltreatment is implemented at both Annacis Island and Lulu Island Treatment Plants.Interest in this project was also shown by the Waste Management Branch,Ministry of Environment and the Ontario Ministry of Environment.The basic objectives of this research project were as follows:Phase I:1. to initially investigate the chemical solubilization process as it pertained to WAS2. to investigate the feasibility of improving the anaerobic digestion of WAS incombination with primary sludge, through low-level alkaline solubilization of WASPhase II:3. to examine the effects of decreasing solids retention time on effluent quality anddigester performancePhase III:4. to minimize the chemical dosage and anoxic mixing time needed for WASsolubilization5. to compare the results of this research with those from previous pilot-scale research5conducted at UBC.As a part of this Master's thesis, objectives listed under 1,2 and 3 were studiedand are reported here-in. Objectives 4 and 5 were also studied and the results will formpart of a Supplementary Report to the Science Council of B.C. in the Spring of 1993.1.3. THESIS ORGANIZATIONThis work is organized in the conventional manner with a series of chaptersfollowed by a number of appendices:Chapter 2 gives the operating theory and fundamental literature review ofanaerobic treatment.Chapter 3 provides a description of the experimental set-up and analyticaltechniques.Chapter 4 discusses and interprets the results which have been obtained from theexperiments in the first phase.Chapter 5 discusses the results which have been obtained in the second phase.Chapter 6 gives general conclusions and recommendations.All of the experimental results are presented in Appendices A through E. Theircontents is as follows:A:^phase I experimental results6B: phase II experimental results; WAS solubilizationC: phase II experimental results; Digester Performance: Solids, Gas Production andMethane ContentD: phase II experimental results; Digester Performance: Carbon, Nitrogen andPhosphorusE: phase II experimental results; Digester Performance: Volatile Fatty Acids,Dewaterability and Environmental Conditions72. LITERATURE REVIEW2.1. ANAEROBIC DIGESTIONAnaerobic digestion is a biological process in which organic matter is convertedto methane and carbon dioxide in the absence of molecular oxygen. It has beensuccessfully applied since 1900 to reduce sludge volume, eliminate pathogens, preventodour nuisances and generate methane as a by product [Naveau, 1984].Anaerobic treatment has been re-discovered in the last decade, mainly as a resultof the energy crisis. It gradually evolved from an airtight cesspool and a septic tank totemperature controlled completely mixed digester and finally to a high rate reactorcontaining a density of highly active biomass [Vochten et al, 1988].Anaerobic treatment is presently employed at most large municipal treatmentplants, and is responsible for the major portion of waste sludge stabilization that occursthere. However, in spite of the significance and large future potential of this process, ithas not generally enjoyed the favourable reputation it truly deserves. The primaryobstacle has been a lack of fundamental understanding of the process, required both toexplain and control the occasional upsets which may occur [McCarty, 1964].82.2. ADVANTAGES OF ANAEROBIC TREATMENTAnaerobic treatment of wastewaters has some distinct advantages over aerobictreatment. Of most importance today is that it produces methane gas, a useful source ofenergy. Aerobic processes, on the other hand, have significant energy requirements foraeration. Because oxygen is not necessary for anaerobic process and mixing costs aregenerally smaller, the energy requirement for operating the anaerobic process is generallynot large, unless heating is required [McCarty, 1985].Unlike aerobic oxidation, the anaerobic conversion of substrate to methane gasyields relatively little energy to the microorganisms; thus, their rate of growth is slowand only a small portion of the waste is converted to new cells, with the major portionof the degradable waste being converted to methane gas. Such conversion to methane gasrepresents waste stabilization, since this gas has a low solubility (K H = 1.5*10-3 mole/L-atm at 20°C) and escapes from the waste stream, where it can be collected and burnedto carbon dioxide and water for heat. Since only a small portion of the waste is convertedto new cells, the problem of disposal of excess sludge is greatly minimized [McCarty,1964].A high degree of waste stabilization is possible through anaerobic treatment. Asmuch as 80 to 90 percent of the degradable organic portion of a waste can be stabilizedby conversion to methane gas, even in highly loaded systems. This is in contrast toaerobic systems, where only a maximum of 50 percent of the waste is actually stabilized,even at conventional loadings [McCarty, 1964].9The requirements for nutrients, such as nitrogen and phosphorus, are reduced andthis is especially important in the treatment of industrial wastes which lack thesematerials [McCarty, 1964]. Also, it has been shown that well adapted sludge can bepreserved unfed for a period of one year or more, without any appreciable deterioration[Obayashi and Gorgan, 1985]. Finally, anaerobically digested sludge can be used as afertilizer [Cillie et al, 1969].2.3. DISADVANTAGES OF ANAEROBIC TREATMENTThe anaerobic treatment process does have some disadvantages which may limitthe use of this process.The major disadvantage is that relatively high temperatures are required for theoptimum operation; temperatures in the range from 30°C to 35°C are preferred [McCarty,1964]. Another disadvantage is the slow growth rate of anaerobic organisms, whichnecessitates long start-up times for the process [McCarty, 1985]. The slow growth ratealso limits the rate at which the process can adjust to changing waste loads, temperatures,or other environmental conditions [McCarty, 1964]. Anaerobic treatment systems are alsomore suceptible to toxic shock or inhibition, in comparison to aerobic systems.102.4. MICROBIOLOGY OF ANAEROBIC TREATMENTThe degradation of organic matter to produce methane relies on the complexinteraction of four different metabolic groups of bacteria:1. the hydrolytic bacteria, which consist of a mixture of fermentative bacteria, sometimescalled acid formers. This group hydrolyze the complex organics, such ascarbohydrates, proteins and lipids to simple compounds, such as short chain fattyacids, alcohols, carbon dioxide and ammonia2. the hydrogen producing acetogenic bacteria, which include both obligate andfacultative species that can ferment organic acids larger than acetic (e.g. butyrate,propionate) and neutral compounds larger than methanol (e.g. ethanol,propanol) toH2 and acetate3. the homoacetogenic bacteria, which can ferment a very wide spectrum of multi or onecarbon compounds to acetic acid4. the methanogenic bacteria, which ferment H 2/CO2 , one carbon compounds (e.g.methanol, carbon monoxide, methylamine) and acetate into methane [Zeikus, 1981].Figure 2.1 shows categories of metabolically distinct bacteria in the methanefermentation [Boone and Mah, 1987].Conversion of complex substrates to methane requires the synergistic action of allfour groups, but the syntropic association of the hydrogen producers of the second groupand hydrogen oxidizers in the fourth group is particulary unique [Gosh and Klass, 1975].In order for energy to be available to the organisms oxidizing propionic acid to acetic11acid and H2 , the partial pressure of H2 cannot exceed 10' atm. At this low pressure, theenergy available to the hydrogen-oxidizing bacteria is reduced considerably from whatit would be at partial pressures near 1 atm. This results in much lower bacterial yieldsper mole of hydrogen gas oxidized, as confirmed by the low overall growth yields forcomplete methane fermentation of propionate and other fatty acids, as well as bythermodynamic predictions [McCarty, 1985].COMPLEX ORGANIC CARBONORGANIC ACIDSNEUTRAL COMPOUNDS 2. hydrogenacetogeizie oacteliaProducilieH2/CO2^ 3.HomoacetogenicONE CARBON COMPOUNDS ---- OP- ACETIC ACIDbacteria* 4. Methanogenic bacteriaCH4 + CO2Figure 2.1. Categories of Metabolically Distinct Bacteria in the MethaneFormation [Boone and Mah, 1987]b)Methanogens: a) Methanobacterium[Tortora et al, 1989]Figure 2.2. and b) Methanosaracina12If hydrogen partial pressure increases above a minimal level, the fermentativebacteria will shift to production of acids other than acetate and conversion of other acidsto acetate by the acetogens will initially cease. Since the primary pathway for methaneproduction is by cleavage of acetate, a decreased rate of biogas production will result[Gunnerson and Stuckey, 1986].Under anaerobic conditions, only a fraction of potential energy is liberatedbecause oxidation is incomplete. In order to obtain an amount of energy equivalent tothat obtained under aerobic conditions, several times as much substrate must be brokendown under anaerobic conditions. Fermentation thus came to be regarded as theanaerobic decomposition of organic compounds to organic products, which could not befurther metabolised by the enzyme systems of the cells without the intervention of oxygen[Doelle, 1975].13Methanogenesis is the domain of the Archaebacteria; in other words, all knownmethanogenic bacteria belong to this kingdom of organisms [Gottschalk, 1986].Archaebacteria is an exceptionally interesting group of bacteria. They differ fromeubacteria (or true bacteria, which represent the majority of bacterial species) in anumber of ways. For example, their cell walls never contain peptidoglycan, they oftenlive in extreme environments, and they carry out unusual metabolic processes [Tortoraet al, 1989]. Figure 2.2 illustrates two methane-producing bacteria.It is apparent that complex organic compounds cannot be utilized by themethanogens. Substrates are Cl compounds and acetate as the only C2 compound. Twonutritional groups of organisms can be envisaged:1. obligate chemolithorophic methanogens that grow with CO2 + H2 according to theequation:CO2 + 4H2 --> CH4 + 2H20^au'. -136 k7^(2.1.)The carbon dioxide here functions as a hydrogen or electron acceptor. A sequence ofmethane formation from carbon dioxide is given in Figure 2.3 [Gottschalk, 1986].2. methylotrophic methanogens that grow with methyl-group-containing substrates (i.e.acetate). The fermentation equation for acetate is:CH3-COOH —> CH4 + CO2^nu). -37 kJ^(2.2.)This group of organisms produce methane directly from the methyl groups and notvia carbon dioxide. The methyl carbon of acetic acid together with its three hydrogenatoms are converted intact into methane gas. The carbonyl carbon is converted tocarbon dioxide. Formation of methane and carbon dioxide from acetate is shown in11 21120F4H2M1r-C110THA1P-H■••-► M F-11TIIMP4 11 2 011I :42oIll ^PIMP-013}TIIMP-11 -4-CoNI-S-C1 131:42011 2ATP^ ii ^0CW4 -S1 1P^ 1120CH3 — CO —X1C11 3 -00011111XICO I -4---)1/4-0- CoM-S-013— H 2 O^ 211ATPI co, II^ 1CoM -SH14Figure 2.4 [Gottschalk, 1986].Figure 2.3. Scheme for the Reduction of CO 2 to CH4 and Site of ATPSynthesis [Gottschalk, 1986]Figure 2.4. Tentative Scheme for the Formation of Methane and CarbonDioxide from Acetate [Gottschalk, 1986]152.5. METHANE PRODUCTION AND INHIBITIONMethane is the most reduced organic compound and it's formation is the terminalstep of the anaerobic food chain.Experiments with labelled acetate showed that 73 percent of the methane insewage digestion came from acetate [Smith and Mah, 1966] (Equation 2.2) andfermentation balance calculations show that, however the acetate is formed, this is closeto the expected proportion [Hobson, 1980].The methane content obtainable from a given feed material can be estimated bythe McCarty model (1974), if the average chemical composition of the feed is known:CnHaObNc + H2O —3. CH4 + CO2 + C5H702N + HCO3 (2.3.)where the C5H702N product is the average chemical composition of anaerobic cells asdetermined empirically. Bicarbonate ion is formed as needed to balance the positivecharge from ammonium ion production. Balancing Equation 2.3. gives:C„H„ObNe + (2n+c-b-9sd/20-ed/4)H20 = de/8 CH4 + (c+sd/20)HCO3+ sd/20 C5H702N + (c-sd/20)NH4 + + (n-c-sd/5-de/8)CO2^(2.4.)where: d = 4n + a - 2b - 3cs + e = 1s - represents the fraction of degradable substrate converted to cellse - represents the fraction of degradable substrate converted to CO 2 and CH4(i.e. energy)s = ae (1 + RebOe )/( 1 + bOe )^ (2.5.)16a, - maximum s value for 0, = 0b - endogenous decay coefficient [time]0, - sludge retention timeR, - the refractory portion of cells formed during decay ( = 0.2 )In this given equation, it is assumed that substrate is converted completely to the productshown. In addition, the equation neglects the effects of digester temperature, pressure andpH, all of which affect the HCO3 and NI14 + concentrations.Another method of estimating biogas production is by means of a materialbalance. This can be done by measuring the COD of all the streams (including biogas)which enter and exit the digester. Of the products in the gas phase, carbon dioxide haszero COD since it is fully oxidized. The COD of methane can be calculated from thestoichiometry of its oxidation reaction:CH4 + 202 --)• CO2 + H2O (2.6.)From this we can see that 1 mole of methane requires two moles of oxygen and thus hasa COD of 2 * 32 g = 64 g. Since 1 mole of gas occupies approximately 22.4 L atstandard conditions (ideal gas law), 1L of methane (at STP) is equivalent to 64/22.4 =2.86g of COD.For an anaerobic process with no oxygen present, COD is a conservativeparameter; this is, the sum of all COD inputs to a digester is equal to the sum of all itsCOD outputs. This means that the COD removed from the feed (i.e. influent COD -effluent COD) is equal to the COD of the biogas. Hence, removal of one gram of CODfrom the feed results in one gram of gaseous COD, or 1/2.86 = .35 L of methane at17STP [Gunnerson and Stuckey, 1986].Any reaction or condition which prevents methane from forming and beingstripped to the gas phase causes reduced COD removal by an anaerobic process. Onepotentially important competing reaction is sulfur reduction, to form sulfides. Reductionof oxidized sulfur species, most commonly sulfate, consumes COD that otherwise wouldbe contained in methane. The COD, or electron equivalents, are found instead in the twomost common sulfide species, HS - and H2S. Although H2S also can be lost to the gasphase, its higher solubility (KH = 1.15 mole/L-atm at 20°C as compared to methane KH =1.5 * 10' mole/L-atm at 20°C) and acid/base equilibrium with HS - (pKa = 7 at 28°C)keeps the large majority of sulfides in solution. Thus, the COD is not removed fromsolution, but merely changes form from organic material to sulfides [Rittmann andBaskin, 1985].Besides this, sulfate also inhibits methanogenesis. Three different mechanismshave been proposed to explain this fact [Zehnder et a1,1981]:1. sulfide formed during bacterial sulfate reduction is poisonous2. sulfide formed during sulfate reduction precipitates essential trace metals (Fe, Ni, Co,Mo) and limit their accessibility to bacteria3. the electrons from the oxidation of organic matter are almost exclusively used forsulfate reduction, since this process is thermodynamically more favourable thanmethane formationOther potentially competing reactions occur in the presence of electron acceptorssuch as metal oxides (FeOOH, Mn02 etc.) and nitrogen oxides (NO3 - , NO2). Electrons18are transferred to one of these inorganic acceptors and methanogenesis usually occursonly after all these alternative electron acceptors are depleted [Zehnder et al, 1981].2.6. ENVIRONMENTAL REQUIREMENTSThe methane bacteria, which are responsible for the majority of waste stabilizationin anaerobic treatment, grow quite slowly compared to aerobic organisms and so a longertime is required for them to adjust to changes in organic loading, temperature or otherenvironmental conditions. For this reason, it is usually desirable to design and maintainoptimal environmental conditions so that more efficient and rapid treatment might beobtained.Optimal conditions for anaerobic treatment include: optimum temperatures, trueanaerobic conditions, sufficient biological nutrients, optimum pH and absence of toxicmaterials [McCarty, 1964].2.6.1. TemperatureThe metabolic and growth rates of chemical and biochemical reactions tend toincrease with temperature, within the temperature tolerances of the microorganisms. Too19high a temperature, however, will cause the metabolic rate to decline due to degradationof enzymes which are critical to the life of the cell. Microorganisms exhibit optimumgrowth and metabolism rates within a well defined range of temperatures, which isspecific to each species [Gunnerson and Stuckey, 1986].Two optimum temperature levels for anaerobic treatment have been reported, onein the mesophyllic range from 30°C to 38°C, and the other in the thermophilic rangefrom 50°C to 60°C. Although treatment proceeds much more rapidly at thermophilictemperatures, the additional heat required to maintain such a temperatures may offset theadvantage obtained. Therefore, most treatment systems are designed to operate in themesophyllic range or lower [Kotze et al, 1969].2.6.2. Anaerobic ConditionsMethanogenic bacteria are extremely oxygen-sensitive. Maintenance of lowoxidation - reduction potential (from -500 mV to -300 mV) is essential to the successfuloperation of methane formation. Not only oxygen, but any highly oxidized material, suchas nitrites and nitrates, can exhibit inhibition of methanogenic bacteria [Pfeffer, 1979].Even small quantities of oxygen can be quite detrimental to the methane-formers andother anaerobic organisms involved. This requirement usually necessitates a closeddigestion tank, which also assists in methane gas collection [Wheatley, 1979].202.6.3. Biological NutrientsThe anaerobic process is dependant upon bacteria which require nitrogen,phosphorus and other materials such as: iron, nickel, cobalt, molybdenum, sodium,magnesium, manganese, aluminum and zinc in trace quantities for optimum growth[Thaner, 1981 and Zehnder et al, 1981].Municipal waste sludge normally contains a variety of these materials, and thususually provides an ideal environment for growth. However, industrial wastes arefrequently more specific in composition and biological nutrients must be added foroptimum operation [McInerney and Bryant, 1988].The amounts of nitrogen and phosphorus needed for anaerobic growth are, byconvention, expressed in proportion to the COD, with the amount of nitrogen normalizedto 7. The COD/N/P ratio is a function of the specific biomass loading or food and it canbe in the range 350/7/1 to 2500/7/1 [Malina and Pohland, 1992].2.6.4. pH and AlkalinityOne of the most important environmental requirements is that of a proper pH.Most organisms grow best under neutral pH conditions, since other pH values mayadversely affect metabolism by altering the chemical equilibrium of enzymatic reactions,or by actually destroying the enzymes. The methanogenic group of organisms is the most21pH sensitive. Low pH could cause the chain of biological reactions in digestion to cease[Gunnerson and Stuckey, 1986].When the pH drops below 6.6, significant inhibition of the methanogenic bacteriaoccurs. At a pH of about 6.2, the acid conditions exhibit acute toxicity to methanogenicbacteria. It is interesting to note that this pH does not stop acid production. Thefermentative bacteria will continue to produce acids until pH drops to 4.5 or 5.0 [Pffefer,1979]. The optimum range for pH is 7.0 to 7.2.Decreasing pH usually results from a high volatile acid concentration. Asignificant drop in pH, however, does not usually occur until the digester is seriouslyaffected. A high volatile acid concentration is the result of unbalanced treatment and nota cause, as is sometimes believed. Thus, a high volatile acid concentration in itself is notharmful, but indicates that some other factor is affecting the methane bacteria [McCarty,1964].The pH of liquor undergoing anaerobic treatment is related to several differentacid-base chemical equilibria. However, at the near neutral pH of interest for anaerobictreatment, the major chemical system controlling pH is the carbon dioxide - bicarbonatesystem, which is related to pH or hydrogen ion concentration through the followingequilibrium equation:[H+] K 1 [H2CO3] / [HCO3 -] (2.7.)The carbonic acid concentration [H 2CO3] is related to the percentage of carbondioxide in the digester gas, K 1 is the ionization constant for carbonic acid (K 1 =4.45*104at 25°C), and the bicarbonate ion concentration [HCO3] forms a part of the total22alkalinity of the system.The bicarbonate ion concentration or bicarbonate alkalinity is approximatelyequivalent to the total alkalinity for most wastes when the volatile acid concentration isvery low. When the volatile acids begin to increase in concentration, they are neutralizedby the bicarbonate alkalinity [McCarty, 1964]. Thus the presence of bicarbonate helpsto prevent adverse effects on methanogens, which would result from such a low pH.Alkalinity in a digester is normally composed of organic acid- ammonium salts,such as ammonium bicarbonate NH 4HCO3 and ammonium acetate CH3COONH4 ,whereby the ammonia comes from protein degradation [McCarty and Speece, 1963].Athigh alkalinity levels (4000 - 6000 mg/L as CaCO 3) and when proteins are high, thereis very little effect of an increase in volatile acid until the volatile acids are equal toabout 0.8 of the alkalinity. At this point, there is very little bicarbonate alkalinity left andthe alkalinity is represented by ammonium volatile acid salts:CH3COOH NH4HCO3 4-> CH3COONH4 + H2O^(2.8.)Thus, the alkalinity is represented by CH3COONH4 and NH4HCO3 and there is a verylittle pH or alkalinity shift until ammonium bicarbonate is exhausted; as such, the freeacids then depress the pH [WPCF Manual of Practice No. 16, 1968].The bicarbonate alkalinity can be approximated by the following formula:BA = TA - .85 * .833 * TVA^ (2.9.)where: BA - bicarbonate alkalinity [mg/L as CaCO 3]TA - total alkalinity [mg/L as CaCO3]TVA - total volatile acid concentration [mg/L as acetic acid]23The equation assumes that there is no significant amount of other materials such asphosphates, silicates, or other acid salts which will also produce some alkalinity.There are two main operational strategies for correcting an unbalanced, low pHcondition in a digester. The first approach is to stop the feed and allow the methanogenicpopulation time to reduce the volatile acid concentration and thus raise the pH. Stoppingthe feed also slows the activity of the fermentative bacteria and thus reduces the acidproduction. A second method involves addition of chemicals to raise the pH and providethe additional buffering capacity [Gunnerson and Stuckey, 1986].The most widely used material for controlling pH is lime. If lime is added, itincreases the bicarbonate alkalinity by combination with the carbon dioxide as follows:Ca(OH)2 + 2CO2 --a• Ca(HCO3)2 (2.10.)However, the calcium bicarbonate formed is not very soluble, and when the bicarbonatealkalinity reach some point between 500 and 1000 mg/L as CaCO 3 , further limeadditions results in the formation of the insoluble calcium carbonate as follows:Ca(OH)2 + CO2 -- CaCO3 + H2O (2.11.)Lime addition beyond this point does not increase the soluble bicarbonate alkalinity, andso has little direct effect on digester pH.One of the most effective chemicals for pH control is sodium bicarbonate.However, it is not as widely used as lime, since it is more expensive [McCarty, 1964].242.6.5. Toxic MaterialsThere are many materials, both inorganic and organic which may be toxic orinhibitory to the anaerobic waste treatment process. The term "toxic" is relative and theconcentration at which a material becomes toxic or inhibitory may vary from a fractionof a mg/L to several thousand mg/L. Figure 2.5 indicates the general effect which resultsfrom the addition of most substances to biological systems [McCarty, 1964]. At somevery low concentrations, stimulation of activity is usually achieved. As the concentrationis increased above the stimulatory concentration, the rate of biological activity beginsto decrease. A point is then reached where inhibition is apparent and the rate ofbiological activity is less than that achieved in the absence of the material. Finally, atsome high concentration, the biological activity approaches zero.Microorganisms usually have the ability to adapt to some extent to inhibitoryconcentrations of most materials [McCarty, 1964]. The toxicity of alkali and alkalineearth - metal salts such as those of sodium, potassium, calcium and magnesium wasfound to be predominantly determined by the cation portion of the salt rather than thevolatile acid anions. The toxic effect of cations, however, vary widely from organism toorganism, with certain species being able to tolerate much higher concentrations thanothers. The order of increasing toxicity of cations to the methane producing organisms,based on equivalent concentration is: a) calcium, b) magnesium, c) sodium, d) potassium,and e) ammonium. These cations are much more toxic if added on a slug - basis thanwhen added slowly over a period of time [McCarty and McKinney, 1961].25INCREASING^DECREASINGSTIMULATION I STIMULATION I^TOXICITYOPTIMUM CONCENTRATIONREACTION RATE^CROSSOVERWITHOUT SALT CONCENTRATION00SALT CONCENTRATIONFigure 2.5. General Effect of Salts or Other Materials on Biological Reactions[McCarty, 1964]If an inhibitory concentration of one cation is present in a waste, this inhibitioncan be significantly reduced if an antagonistic ion is present or is added to the waste[McCarty, 1964]. The inhibition caused by excessive concentrations of any one of thesodium, potassium, calcium or magnesium ions would be antagonised by the addition ofthe optimum concentration of at least one of the other four cations. Also, maximumantagonism of an inhibitory cation can be obtained by the addition of optimumconcentrations of several, rather than only one of the other cations [McCarty, 1964].Experiments indicate a different type of toxicity with ammonium than with theother cations, as methane organisms can apparently adapt quite well to the toxicity ofother cations; with time, ammonium becomes more toxic [McCarty and McKinney,1961].26Ammonia exerts a complex effect on methanogenic species, this effect beingmediated by both NH4 + and by the unionized NH 3 form. The specific inhibitory effectof ammonia on methanogenesis is related to the extracelluar N11 4+ concentration.Extracelluar ammonia was shown to affect methanogenesis by causing an ammonia/K+exchange. An early effect of ammonia entry is an alteration of the internal pH. Furtherentry of ammonia then results in destruction of the membrane potential [Saldnoja-Salonenand Colleran, 1986].Ammonia is usually formed in anaerobic treatment from the degradation of wastescontaining proteins or urea. Ammonium bicarbonate is normally beneficial, as it acts asa natural buffer, resisting a drop in pH from excessive volatile acid accumulation.However, the high ammonium bicarbonate production may create ammonium ion toxicity[McCarty and McKinney, 1961]. pH plays a significant role in the toxicity of ammonia,as indicated by the following equilibrium equation [Kugelman and Chin, 1971 and Speeceand Parkin, 1983]:NH4 + ** NH3 + H+^ (2.12.)ammonium free ammoniaionWhen hydrogen concentration is sufficiently high (pH of 7.2 or lower) theequilibrium is shifted to the left so that inhibition is related to the ammonium ionconcentration and toxicity is similar in nature to toxicity produced by other ions insolution. At high pH levels, the equilibrium shifts to the right and the ammonia gasconcentration may become inhibitory. Ammonia gas is inhibitory at much lower27concentration than the ammonium ion and can result in complete stoppage of all activity.The toxicity of free ammonia can be reduced by keeping the pH down around 7.0[McCarty and McKinney, 1961].Sulfides produced in anaerobic treatment may exist in soluble or insoluble form,depending upon the cations with which they become associated. Heavy metals sulfidesare insoluble and precipitate from solution, so they are not harmful to themicroorganisms. The remaining soluble sulfide forms a weak acid which ionizes insolution, the extent depending upon the pH. Also, because of limited solubility ofhydrogen sulfide, a certain portion of that formed will escape with the digester gasproduced. The only toxic form of sulfide is soluble sulfide in concentrations above 200mg/L. Toxic concentrations of sulfide may be reduced by gas scrubbing, use of iron saltsto precipitate sulfides, dilution of the waste, or separation of sulfate from the waste[McCarty et al, 1964].Low, but soluble concentrations of heavy metals such as: copper, zinc and nickelsalts are quite toxic. Hexavelant chromium can also be toxic to anaerobic treatment. Ironand aluminum are not toxic because of their low solubility [McCarty, 1964].Concentrations of toxic heavy metals, which can be tolerated, are related to theconcentration of sulfides available to combine with heavy metals to form very insolublesulfide salts; these are inert and do not adversely affect the microorganisms. When thesulfide concentration available for this precipitation is low, only small quantities of heavymetals can be tolerated.There are also many organic materials which may inhibit the digestion process.28These range from organic solvents to many common materials such as the alcohols andlong-chain fatty acids [McCarty et al, 1964].2.7. KINETICS OF METHANE FORMATION AND BIOMASS GROWTHIn the complex multistep process such as anaerobic treatment, the kinetics of theslowest step will govern the overall kinetics of waste stabilization. This slowest or ratelimiting step in anaerobic treatment generally is believed to be the methane formation.Acetic and propionic acids are the precursors of approximately 85 percent of the methaneformed from the complete treatment of a complex waste [Lawrence, 1971]. Thus, aknowledge of the kinetics of the methane fermentation of these acids is a key element inthe development of a rational approach to the analysis and design of anaerobic treatmentsystems [Lawrence and McCarty, 1969].The Monod rate equation applies to a single strain of bacteria growing on a single"rate-limiting" substrate and relates the rate of uptake of that substrate to itsconcentration in the growth medium. It assumes that all other substrates and nutrients arepresent in excess, and it further assumes that the products of the reaction do notaccumulate sufficiently to inhibit the fermentation. It describes a form of "saturationkinetics" in which the rate of reaction, initially proportional to the concentration ofsubstrate, gradually approaches a maximum value which cannot be exceeded no matter29how high a concentration of substrate is applied. By analogy with enzyme kinetics, thisis believed to occur when the bacteria's "rate-limiting enzyme system" is saturated andthe substrate is than said to be present "in excess" [McCarty and Mosey, 1991]. TheMonod rate equation is usually written as:dF/dt = kMS/(Ks + S)^ (2.13.)where: dF/dt - rate of waste utilization per unit volume of digester [mass/volume-time]S^- waste concentration in the reactor [mass/volume]k^- maximum rate of waste utilization per unit weight of microorganismstime']Ks^- half velocity coefficient equal to the waste concentration when dF/dt isequal to one-half of the maximum rate k [mass/volume]M^- microorganism concentration [mass/volume]Monod's original equation was derived from observations of youngpopulations of microorganisms, growing rapidly in the presence of an abundant foodsupply where this relationship generally holds true. Many anaerobic digesters use elderlypopulations of bacteria, growing slowly under semi-starvation conditions where asignificant proportion of the energy content of the substrate is used by themicroorganisms simply to stay alive. To allow for this, McCarty derived a similarequation from the concept that microorganisms are not immortal and can die of starvationor "old age"; this is usually written as [McCarty and Mosey, 1991 and Mosey ,1983]:dM/dt = a dF/dt - bM^ (2.14.)where: dM/dt - microorganism net growth rate per unit volume of digester [mass/volume-30time]dF/dt - rate of waste utilization per unit volume of digester [mass/volume-time]M^- microorganism concentration [mass/volume]a^- growth yield coefficientb^- microorganism decay coefficient [time']Combining equations 2.13. and 2.14. leads to the following expression:dM/dt^akS^b (2.15.)M^Ks+SThe quantity (dM/dt/M) is equal to the net growth per unit weight of microorganisms perunit time, and may be designated as net specific growth rate, tc. Equation 2.15 isapplicable to both the conventional anaerobic treatment process and the anaerobicactivated sludge or contact processes. Either process eventually can reach a steady statesituation in which the mass of microorganisms in the system will remain constant. Thisrequires that the rate at which microorganisms are wasted from the system must eHxalthe net microbial growth rate, dM/dt. Expressing time in days, the daily net specificgrowth rate, a Mtn TIM, is the reciprocal of the biological solids retention time, SRT:SRT = MT/(OM/OT)T^ (2.16.)where:^MT - total weight of active microbial solids in the system [mass](aminT)T - total quantity of active microbial solids withdrawn daily,including those solids wasted and those lost in the effluent[mass/time]Since the conventional process is mixed completely, the microorganism31concentration is the same in the digester and in the effluent. The quantity of solids wasteddaily, (ominT)T is equal to Q/V times the total mass of the microorganisms in thesystem, MT, where Q and V are the daily flow rate and the volume of the digester,respectively [Lawrence and McCarty, 1969].Process failure due to kinetic stress will occur when the SRT is reduced to a valueat which the microorganisms are wasted from the system at the rate greater than theirmaximum net specific growth rate. Under those conditions, waste treatment efficiencydrops to zero and the effluent waste concentration is equal to the influent wasteconcentration [Lawrence and McCarty,1969].2.8. GAS COMPOSITION AND USEThe volume and composition of the gas produced are characteristics of thesubstrate digested. Variations in substrate composition and concentration are reflected inthe gas production of a digester. No dogmatic rule can be laid down concerning a definiteratio of methane to carbon dioxide or the volume of gas which should be produced[Kotze et al, 1969].Analysis of gas composition suggests that the carbon dioxide content wouldincrease with increasing temperatures. The decrease in the amount of carbon dioxideremaining in the liquid phase produces more carbon dioxide in the gas phase. This fact32is complicated by the increased vapour pressure of water at higher temperatures[Pfeffer,1979]. The actual moisture content of the gas will be dependant upon thetemperature of the gas as it is collected. Generally, it leaves the digester system saturatedand the cooling of the gas that occurs in the pipeline causes condensation [Kotze et al,1969]. This changes the percentage of methane and carbon dioxide in dry gas from whatit was produced [Pfeffer, 1979].Gas from anaerobic digestion usually contains about 65 to 70 percent methane byvolume, 25 to 30 percent carbon dioxide, and small amounts of nitrogen gas, hydrogengas, hydrogen sulfide, water vapour and other gases [Metcalf and Eddy, 1991].Methane gas at standard temperature and pressure has a net heating value of 35800 kJ/m3 . Because digester gas is typically about 65 percent methane, the heating valueof digester gas is approximately 22 400 kJ/m 3 . By composition, natural gas, which is amixture of methane, propane and butane, has a heating value of approximately 37 300kJ/m3 . In large plants, digester gas may be used as fuel for boiler and internalcombustion engines, which are in turn used pumping wastewater, operating blowers andgenerating electricity [Metcalf and Eddy, 1991].333. EXPERIMENTAL SET-UP AND ANALYTICAL TECHNIQUES3.1. SLUDGE SOURCEBoth primary and waste activated sludge (WAS) were obtained from the UBCpilot-scale plant. This facility treats domestic wastewater from campus residences. It isdesigned as a nutrient removal plant, with special reference to phosphorus removal.The pilot plant was chosen as a source of sludge as it is close and represents aconvenient source of sludge. Sludge for this research was obtained on a daily basis andwas stored in a cold room at the temperature of 4°C until it was used.Figure 3.1 shows the configuration of the pilot plant treatment scheme. Primarysludge was obtained from the primary clarifier and waste activated sludge from thesecondary sludge thickener.3.2. LABORATORY SET - UPA schematic drawing of the pilot-scale anaerobic digesters used in Phase II of thisstudy is shown in Figure 3.2. Digesters were placed in a Conviron environmentalchamber, where temperature can be controlled and was set at 35°C.The digesters were 204 L capacity polyethylene tanks, filled with 160 L ofEff.NW"-IntlWentSewageFermenter^Anaerobic^Anoxic^Aerobic^ Secondary ClarifierExperimental SideFermenter Anaerobic Anoxic Aerobic Secondary ClarifierEff.Primary ClarifierPrimary Sludge for Research^ Ow-WAS for Research-.110^Control SideWaste Sludge ThickenerFigure 3.1. UBC Pilot Plant Configuration ( Figure not drawan to scale )C>C)exp Ca(OH)2Gas MeterEft.exp NaOHGas MeterEff.C734CDcontEft.WAS + NaOH^ WAS + Ca(OH)2PumpsI WASDrainOP"'Figure 3.2. Phase II Experimental Set-up ( Figure not drawn to scale )36completely mixed active liquid. The top of each digester was sealed with silicone. Themixer shaft was placed in a submerged plastic pipe to minimaze any loss of the gas. Thisloss of gas was assumed negligible. Gas outlets were connected to the gas-traps wherehydrogen sulfide was precipitated with ferric chloride before entering gas meters. Gasvolume was recorded by three Alexander Wright & Co gas meters.Waste activated sludge (WAS) was solubilized with sodium hydroxide or calciumhydroxide in plastic hoppers and then pumped together with primary sludge into thedigesters. The Solids Retention Time (SRT) in the digesters was controlled with overflowwasting. Pumping of sludge was done by two Teel Progressive Cavity pumps.3.3. DIGESTER OPERATION ( Phase II )As mentioned above, solubilization of WAS was performed in the plastic hoppers.WAS was well mixed and divided into three hoppers; for the control unit, WAS was leftin the hopper for a total time of 5 hours, without mixing. For the two experimental units,WAS was mixed at 60 rpm for 5 hours with chemical addition. After 5 hours, primarysludge was added and digesters were fed.All digesters were operated on a daily fill-and-draw basis. A fixed volume ofdigested sludge was removed from the digesters through overflow wasting, and an equalvolume of raw sludge was pumped through the bottom inlet valve at the same time that37the wasting was done. In this way, a reactor volume of 160 L was maintained and airentrainment was minimized. By operating on a daily fill-and-draw basis, strict controlwas maintained on the digester solids retention time. For this research, SRT is definedas:SRT = (volume of digester [L] )/(volume wasted per day [L/day])Before any wasting, the mixer speed in the digesters was increased from about20 -30 rpm to about 60 - 75 rpm for 10 - 15 minutes, so that effluent quality was thesame as the digester mixed-liquor. All pipe lines were rinsed with 2 L of each of thedigester's feed before the digester was fed. Gas volume was recorded just before feedingand wasting.3.4. EXPERIMENTAL SEQUENCE ( Phase II )Throughout the research program, all parameters were held constant except solidsretention time. Table 3.1 summarizes the experimental regime. It can be seen that for allfour runs, chemical dose, anoxic mixing time, temperature and ratio of primary sludgeto WAS were constant. The only variable was SRT.Each run was 2 SRT's long except the last one which ran for 3.5 SRT's. Ideally,each run should had been as long as possible, until full "steady-state" conditions werereached. It was felt that, for the longer runs 2 SRT's was adequate while 3.5 SRT's was38sufficient for the low 10 day SRT run. The literature in biotreatment work recognizesTable 3.1.^Digester Experimental Sequence ( Phase II )run # reactor SRT[days]temp.[°C]ch.dose[meq/L]mix.time[hours]1°/WAS sludge loading rate[kgC0Dt/nAlay]cont .567 ±.1741 expCa(OH)2 25 35 15 5 35/65 .565±.185expNaOH .560 ± .155cont .841 ± .1632 expCa(OH)2 20 35 15 5 35/65 .818±.162expNaOH .839 ± .164cont 1.019±.1143 expCa(OH)2 15 35 15 5 35/65 1.017 ± .146expNaOH 1.010±.115cont 1.324 ± .2554 expCa(OH)2 10 35 15 5 35/65 1.312 + .260expNaOH 1.311±.2481.5-2 SRT's as "adequate" for process performance evaluation and data collection, atquasi-steady-state conditions.3.5. ANALYTICAL AND SAMPLING TECHNIQUESDigester performances were assessed through the examination of the followingparameters: solids, nitrogen, phosphorus, chemical oxygen demand, total organic carbon,39volatile fatty acids, gas volume and composition, pH, temperature, oxidation-reductionpotential (ORP) and sludge dewaterability.For filtered mixed-liquor (filtered ML) sample analysis, a 250 mL aliquot ofmixed liquor was spun at 3500 rpm, for approximately 15 minutes in an InternationalEquipment Company Model CS centrifuge. Supernatant was filtered through WhatmanNo 4 filter and then preserved and stored.For mixed-liquor (ML) sample analysis, a 250 mL aliquot of mixed liquor wasblended for 60 seconds with a Braun Multipractic Handblender to homogenize thesample. Samples were than diluted 1/20, preserved and stored.The majority of the tests were carried out in accordance with Standard Methods,16th Edition [A.P.H.A., 1989]. Non-standard procedures are outlined below.3.5.1. Solids3.5.1.1. Total Suspended and Total Volatile Suspended SolidsSuspended solids were determined in the following manner: 25 mL aliquots ofwell stirred ML were poured into 50 mL centrifuge tubes and spun at 3500 rpm forapproximately 15 minutes. Supernatant was filtered through a pre-weighted Whatman No934-AH filter, sludge pellets transferred into the filter, centrifuge tubes rinsed withdistilled water and filtered. The filters were transferred into pre-weighted aluminum40dishes and then placed in a Fisher Isotemp forced draft oven operating at a constanttemperature of 104°C. Samples were left overnight to dry. The next day, samples weretransferred into a desiccator and after cooling, total suspended solids (TSS) weredetermined gravimetrically on a Mettler AC 100 electronic balance.Total volatile suspended solids (TVSS) were determined by igniting the residueat 550°C for one hour in a Lindberg muffle furnace. After cooling in the desiccator,TVSS were determined gravimetrically.3.5.1.2. Total Solids and Total Volatile Solids30 mL aliquots from a well mixed sludge sample were poured into pre-fired andpre-weighted ceramic evaporating dishes. Samples were left to dry at 104°C overnight.The next day, after cooling in the desiccator, total solids (TS) were determinedgravimetrically and the residue ignited at 550°C to determine total volatile solids (TVS).3.5.2. pH and TemperaturepH and temperature readings were taken once a day, after wasting. The pH andtemperature probes were immersed into the well mixed bucket of effluent and readingswere recorded after the values stabilized.41The pH and temperature probes were stored in a pH 7.01 standard buffer solutionwhen they were not in use. All pH and temperature measurements were performed usinga Cole - Parmer pH/mV/Temperature Bench Meter. pH values were determined usinga gel-filled silver chloride reference electrode, which was enclosed in a PVC casing.The pH meter had a temperature compensation adjustment feature, so that effectsof higher temperature on pH were accounted for.3.5.3. Chemical Oxygen DemandSamples for total chemical oxygen demand (COD) were blended, as described inthe Section 3.5., and samples for soluble COD were obtained by centrifugation andfiltration, as described in Section 3.5.. For the first phase of the study, samples for totalCOD were not blended. COD was determined by the open reflux method described inStandard Methods [A.P.H.A., 1989].For the second phase, COD was determined by the closed reflux, colorimetricmethod described in Standard Methods [A.P.H.A., 1989]. Samples were run induplicates. Samples were digested in a Hach COD Reactor. COD was determined byreading absorbency of standards and samples on Bausch & Lomb Spectronic 88spectrophotometer at wavelength of 600 nm.423.5.4. Total Organic CarbonTotal organic carbon (TOC) was determined only for filtered ML samples usingthe Shimadzu Total Organic Carbon Analyzer TOC-500. All samples were analyzed, intriplicate, at the very minimum.3.5.5. Ammonia NitrogenAmmonia nitrogen (NH4-N) was determined only for filered ML samples usingthe phenolate Quik Chem method No 10-107-06-1-Z. Analysis was performed on theLachat Instruments Quik Chem AE instrument.3.5.6. Total Kjeldahl NitrogenTotal Kjeldahl nitrogen (TKN) was determined for both filtered ML and MLsamples. Samples and standards were digested on a BD-40 block digester. Theconcentration of TKN in the samples and standards was then determined colorimetricallyusing a Tehnicon Auto Analyzer II. All block-digested samples were analyzed at least induplicate on the auto analyzer using Technicon Industrial Method No 325-74W.433.5.7. Orthophosphate PhosphorusOrthophosphate phosphorus (PO 4-P) was determined only on filtered ML samplesusing Quik Chem method No 10-115-01-1-Z on the Lachat Instruments Quik Chem AEinstrument.3.5.8. Total PhosphorusML and filtered ML samples for analysis of total phosphorus (TP) wereprepared in the same way as for TKN analysis. The concentration of TP was determinedfor samples and standards using the Tehnicon Auto Analyzer II. All block-digestedsamples were analyzed in duplicate by the method described in Technicon IndustrialMethod No 327-74W.3.5.9. Volatile Fatty AcidsVolatile fatty acids (VFA) were determined only for filtered ML samples usingthe method described in Supelco Bulletin 751. Analysis was done on HP 5880A SeriesGas Chromatograph.443.5.10. Gas CompositionComposition of the digester gas was determined by the gas chromatographicmethod described in Standard Methods [A.P.H.A., 1989]. Analysis was performed ona Fisher - Hamilton Gas Partitioner with a combination of molecular Sieve 13X andDEHS 30% on Chromosorb P column packing, using helium as the carrier gas.3.5.11. DewaterabilityDewaterability (CST value) was determined only on effluent ML samples.Analysis was performed on a Komline - Sanderson Capillary Suction Timer (CST)instrument. The instrument measures the elapsed time of filtrate flowing across a specialfilter paper under the influence of capillary suction. Accurately spaced electrical probesactivate and then stop a timer as the wave front of filtrate passes each probe.3.5.12. Oxidation - Reduction PotentialOxidation-reduction potential (ORP) was recorded in situ, by immersing the probedirectly into the reactor through a submersed tube which was sealed when ORPmeasurements were not taken. Unfortunately, this built-in PVC tube was too small onthe control unit, so it was not possible to take ORP readings for this unit.45ORP values were recorded on a Cole - Parimer pH/mv/Temperature Bench Meterinstrument. The Broadley James ORP probe was stored in saturated KC1 solution whennot in use. The reference electrode was Ag-AgCl.3.5.13. Sample PreservationIt was not possible to analyze all the samples immediately upon collection andpreparation, so samples were preserved and stored until analysis. Table 3.2 summarizesthe procedures used for preservation and storage of samples.Table 3.2.^Sample Preservation and Storage TechniquesparameterCODTOCNH4-NPO4-PTKNTPVFApreservativeconc. H2SO4 pH <2conc. H2SO4 pH <2conc. H2SO4 pH < 2conc. H2SO4 pH < 2conc. H2SO4 pH < 2storage4°C-15°C4°C4°C4°C4°C-15°C463.6. SAMPLING FREQUENCYTemperature, pH and gas production were monitored on a daily basis. Influentand effluent samples for TS/TVS and TSS/TVSS were taken each day and one of theTSS/TVSS was run in duplicate. Solids samples of non-treated WAS and WAS after thesolubilization process were taken only on days when samples for the other analyses weretaken.Influent, effluent, non-treated WAS and solubilized WAS samples for TOC, VFA,NH4-N, PO4-P, total and soluble COD, TKN and TP were taken twice a week for thefirst two runs and three times a week for the last two runs.Gas composition was determined once or twice a week and dewaterability andORP were determined from time to time (on average, once every two weeks).474. PHASE I - RESULTS AND DISCUSSION4.1. INTRODUCTIONThe objective of Phase I was to investigate solubilization of waste activatedsludge. Waste activated sludge (WAS) was supplied from the UBC pilot-plant and storedin a cold room at temperature of 4°C until it was used. It was decided to examine theeffects of the addition of 10, 15 and 20 meq/L of both sodium hydroxide and calciumhydroxide individually to WAS for the mixing times of 3, 5, 7 and 9 hours. Thisexperimental screening process was chosen after discussions with the interested partiesand the review of the existing, but sparse, literature in this area.Experiments were set at room temperature in three 5-L jars. One jar was used ascontrol unit and WAS was just mixed without any chemical addition. WAS in the othertwo jars was slowly mixed with the addition of sodium hydroxide and calcium hydroxideusing a mechanical mixer, without aeration (i.e. mechanical blending). Figure 4.1presents the experimental set-up for the first phase. WAS^ WAS + Ca(OH)2 WAS + NaOHFigure 4.1. Phase I Experimental Set-up (Figure not drawn to scale)48Samples of WAS were taken at the beginning, before any mixing and chemicaladdition and then after 3, 5, 7 and 9 hours. Parameters that were examined in order todetermine the effects of chemical addition and anoxic mixing time on solubilization ofWAS were: solids, pH, chemical oxygen demand, biochemical oxygen demand, nitrogen,phosphorus and total organic carbon.4.2. RESULTS AND DISCUSSION4.2.1. SolidsSolids that were determined were: total solids (TS)/ total volatile solids (TVS) andtotal suspended solids (SS)/total volatile suspended solids (VSS). From Figure 4.2 it canbe noted that VSS did not change with time for the control unit, or for the unit withcalcium hydroxide addition. For the unit with sodium hydroxide addition, a significantdestruction of VSS is noticeable for all three chemical dosages. The highest VSSdestruction occurred between 3 and 5 hours of anoxic mixing. Table 4.1 summarizespercent VSS destroyed during WAS solubilization for the unit with sodium hydroxideaddition.The same decreasing pattern of solids with time was observed for suspendedsolids (Appendix A), whereas total solids, for both experimental units, increased with49time. A higher level of TS was observed for the unit with calcium hydroxide additionTable 4.1.^Percent VSS Destruction in WAS for Sodium Hydroxide Additiontime (hours) 10 meq/L 15 meq/L 20 meq/L0 - 3 2.8 3.0 8.33 - 5 5.2 6.7 16.95 - 7 1.1 1.3 0.77 - 9 4.6 0.5than for sodium hydroxide addition (Figure 4.3). An increase of TS for bothexperimental units was due to the direct addition of chemicals into the solution. Totalvolatile solids did not change, with time, for any of the three units.4.2.2. pHAs was expected, the pH increased with chemical addition. Figure 4.4 shows pHchange over time for all three units and chemical dosages. For the control unit pH stayed........................................ AM- ...... . .. ....85008200-7900-7600--J15-) 7300-7000-cow 6700->6400-6100-5800-5500 ochemical dose 10 meq/L6Mixing Time (hours)chemical dose 1 5 meq/L8500---"--"-------1"--"--"--------....._._....._._..E 7000-a7300-^.........(3)6700-7600!1.-...*`- .7900-^-^............................8200-...... ............... ................................... ...............> 6400-6100-5800-5500^0 2^3^4^a^6^7^6^9Mixing Time (hours)^8500^8200-79007600-a7300-E 7000-u)u) 6700->6400-6100-5800-^5500^0 chemical dose 20 meq/L...................................4^5^6^7^6Mixing Time (hours)9cont^Ca(OH)2^NaOHFigure 4.2. Phase I - Solubilization of WAS: Volatile Suspended Solids (mg/L)50. -MN8 9111 ^10.8-10.6-10.4-15"-o 10.2-0)Dcrs10-9.8-9.6-9.4-9.2-9 0 4Mixing Time (hours)chemical dose 10 meq/L5111 ^10.8-10.6---c-e-o 10.2--6) co10-9.8 —9.9.4-9.2-...... ......... ....... .•^.......... ......... ^OEMS4^5^6^7^8^9Mixing Time (hours)chemical dose 15 meq/L11^10.8-10.6-^ (.7. 10.4--oc 10.2-E co 10-z9.8- ...........9.6k..--9.4-9.2-0 2^3^4^5Mixing Time (hours)111=. .................... MN.............8 9chemical dose 20 meq/Lcont^Ca(OH)2^NaOHFigure 4.3. Phase I - Solubilization of WAS: Total Solids (mg/L)52fairly constant during the whole experiment. The highest change in pH for the unit withcalcium hydroxide addition occurred during the first 3 hours of anoxic mixing. Thisapplied for all three chemical dosages. For the unit with sodium hydroxide addition, itcan be seen that the highest increase in pH was between 3 and 5 hours of anoxic mixing.The addition of sodium hydroxide increased the pH more than did the addition of calciumhydroxide.4.2.3. Chemical Oxygen DemandThe chemical oxygen demand (COD) was determined for both filtered ML andML samples. One total COD result (total COD reading for the addition of 10 meq/L ofsodium hydroxide to WAS and anoxic mixing time of 5 hours) was not consideredreliable, since the total COD was much higher than any other total COD reading. Sucha high total COD reading was attributed to the fact that ML samples were not blendedin this phase. In addition, three soluble COD results (for samples with addition of 20meq/1 of sodium hydroxide and anoxic mixing times of 5, 7 and 9 hours) were "lost" -samples were titrated beyond the end point. However, the general trend of thesolubilization process can still be followed.It can be observed from Figure 4.5 that the addition of 10 meq/L of calciumhydroxide was effective only for the longer mixing times (7 and 9 hours), whereas theeffectiveness of sodium hydroxide was significant after only 5 hours. As chemicala 94Mixing Time (hours)11 10.5-10-9.5-9-8.5-8-7.5-7-0............ •. •^.......................... .......... .. IMO............chemical dose 10 meq/L5311 ^10.5-10-9.5-9-8.5-8-7.5-7-Air 6.50 ................ .............^K94^5Mixing Time (hours)^ss9chemical dose 15 meq/L............^................ Am- .... ... ..... --...-- ... ...I^9- 8.5- ^8-^ ...r...-------7.5-7-6.5m^0 i^2^3^4^eMixing Time (hours)chemical dose 20 meq/L11  10.5-10-9.5-acont^Ca(OH)2^NaOHFigure 4.4. Phase I - Solubilization of WAS: pH54dosages increased, the effectiveness of both chemicals increased and is noticeable evenfor a mixing time of 3 hours.Table 4.2 gives the percent of soluble COD with respect to total COD.Calculations are done with average values for total COD. It can be noted that the percentof soluble COD increased with longer mixing times and for higher chemical dosages, anexpected result. It is also noticeable that the addition of sodium hydroxide was moreeffective in releasing organic material from WAS than was calcium hydroxide. Based onthe 15 meq/L NaOH results, the 9 hour mixing and 20 meq/L NaOH result was predictedto be about 25 percent of soluble COD in WAS.Table 4.2.^Percent Soluble COD in WAS10 meq/L 15 meq/L 20 meq/Ltime cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH0 3.2 3.2 3.2 2.9 2.9 2.9 2.9 2.9 2.93 3.5 3.1 3.8 3.0 4.6 3.9 3.2 3.85 3.4 3.7 9.4 3.3 5.4 12.5 3.3 6.97 2.9 3.9 10.6 3.5 5.3 17.6 3.3 7.59 3.3 4.5 12.1 2.9 6.8 19.5 3.0 8.9 (25)*• predictedThe results presented in Table 4.2 are comparable to the results reported by Rajan55et al [1989] for the addition of sodium hydroxide (i.e. for chemical dose of 10 meq/Land anoxic mixing of 5, 7 and 9 hours, Rajan et al reported percent solubilization to be10, 11 and 12, respectively). However, for the addition of calcium hydroxide, Rajan etal reported only the results obtained at a temperature of 38°C. This explains thesomewhat higher percent solubilization reported by these authors, compared to thesolubilization presented in Table 4.2 (i.e. for chemical dose of 20 meq/L and anoxicmixing of 5, 7 and 9 hours, Rajan et al reported percent solubilization to be 11, 12 and13 respectively).4.2.4. Total Organic CarbonTotal organic carbon (TOC) was determined only for filtered ML samples. It isobserved from Figure 4.6. that the addition of calcium hydroxide, in the amount of 10meq/L, did not improve WAS solubilization; whereas, the same amount of sodiumhydroxide significantly increased TOC in solution, between 3 and 5 hours of anoxicmixing. Again, as for COD, the release of organic material increased with higherchemical dosage and for longer mixing time, with sodium hydroxide being much moreeffective.From Figure 4.6 it can be seen that, for sodium hydroxide addition, there was asignificant increase in TOC concentration for lower chemical dosages, between 3 and 5hours of mixing..............................4*.chemical dose 10 meq/L2600^2400-2200-2000-1800-? 1600-1400-0 1200-5600 1000-800-.. . .... ... . ........^•-•-- ............ .111, ....................... 6^7^8^9600-400-■200 0^1^2^3^4^5Mixing Time (hours)chemical dose 15 meq/L2600^2400-2200-2000--;11- 1800-1600-^ pm. co 1400-0 1200-00 1000-800-600- ^ &"*"200 02^3^4^5^é^7^8^9Mixing Time (hours)2600 ^2400-2200-2000-1800-' 1600-E0E1400-00 1200-0 1000-800-600-200 0chemical dose 20 meq/L4^5^éMixing Time (hours)cont^Ca(OH)2^NaOHFigure 4.5. Phase I - Solubilization of WAS: Soluble COD (mg/L)...............................^.......^............ ................... ANIf...............  ^ lowr^^abb ^9811001000-900-800-- 700-cy)E 600-500-0 400-300-200-1000 4^5^6^7Mixing Time (hours)chemical dose 10 meq/L570 0^chemical dose 15 meq/L1100^1000-900-800-▪ 700-E 600-0 500-O° 400-300-200-100AIL P. ................... ........................................^...1^2^3^4^5^6^8^9Mixing Time (hours)chemical dose 20 meq/L^1100 ^1000-1900-800-700-6)E 600-500-0 400-i—300-200-100,71. ^0 ^••■■■••nror.............1 3^4Mixing Time (hours)cont^Ca(OH)2^NaOHFigure 4.6. Phase I - Solubilization of WAS: Total Organic Carbon (mg/L)584.2.5. PhosphorusThe fate of phosphorus was followed through determination of total phosphorus(TP) for ML and filtered ML samples and orthophosphorus (PO 4-P) for soluble samples.Soluble phosphorus was mostly in orthophosphorus form: up to 100 percent of solubleTP was in the form of PO4-P (see Table 4.3).From Table 4.4, it can be seen that the percent of soluble TP in WAS for the unitwith sodium hydroxide addition increased with longer anoxic mixing time, whereas thatpercent was stable for the control unit. The percent of soluble TP was calculated usingaverage values for total TP. For the calcium hydroxide addition, the concentration ofTable 4.3.^Percent PO4 - P in Soluble TP10 meq/L 15 meq/L 20 meq/Ltime cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH0 100 100 100 93 93 93 97 97 973 100 87 93 96 62 94 70 985 97 83 87 93 59 82 91 42 987 95 89 88 92 53 86 100 39 869 100 89 90 94 58 88 98 54 9259Table 4.4.^Percent Soluble TP in WAS10 meq/L 15 meq/L 20 meq/Ltime cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH cont Ca(OH)2 NaOH0 33 33 34 37 37 37 30 30 303 35 14 35 37 7 35 5 305 35 12 44 38 7 47 - 7 337 35 12 44 38 7 51 29 7 449 34 12 44 37 7 52 29 6 49soluble phosphorus (both soluble TP and PO 4-P) significantly decreased during the first3 hours of anoxic mixing, for all three chemical dosages, and then remained stable. Thisdecrease was attributed to precipitation of phosphorus as calcium phosphate.Figures 4.7 and 4.8 give soluble TP and PO 4-P for all three units and chemicaldosages.4.2.6. NitrogenNitrogen was monitored through the determination of total Kjeldahl nitrogen(TKN) for ML and filtered ML samples and ammonium-nitrogen (N114-N) for filteredML samples....................^...........120 ^110-100-90-80-  o,60-o_v" 50-- 40-30-20-10- 8^90^1^2 4Mixing Time (hours)0chemical dose 10 meq/L90-^ ........ ..........80- .............7.5) 70-1.E 60-N 50-o_I--^40-^-----......30 -20-10-0  0^1^2^3^4^5^6^i^6^eMixing Time (hours)chemical dose 15 meq/L120^110-100-90-80A. ifh 70-E 60-50-n_- 40-30-20-10-4^ 9Mixing Time (hours)chemical dose 20 meq/Lcont^Ca(OH)2^NaOHFigure 4.7. Phase I - Solubilization of WAS: Soluble TP (mg/L)60120^110-100-i^ s^....... .. ....................... .• -MO^ -OM0 0^chemical dose 10 meq/L611201101009080E 70a_ 60'•^50O 403020100 0 ...................-ow1 2^3^4^5Mixing Time (hours)6 7 8 9chemical dose 15 meq/L120110-100-90-• 80-O 70o 60-50-•;1-O 40-o_ 30-20-10-00.......................^................. ................^ Int^.....-OP^41.4^5 6^7^8^9Mixing Time (hours)chemical dose 20 meq/L120^110-100-90-.7g 80-E 70'7^o_ 60-• 50-O 40-• 30-20-10-0...........^................. .............................^..... .......4Mixing Time (hours)cont^Ca(OH)2^NaOHFigure 4.8. Phase I - Solubilization of WAS: PO 4-P (mg/L)62Table 4.5 summarizes the percent of NH 4-N in soluble TKN. It can be seen thatthe percent of NH4-N decreased with time for all three units, although the concentrationof NH4-N increased with time (see Figure 4.9).From Figure 4.10 it can be observed that the concentration of soluble TKNincreased with time. The conclusion that can be made, based on the information givenin Table 4.5 and Figures 4.9 and 4.10, is that the concentration of soluble nitrogencompounds (i.e. organic nitrogen) increased much more than the concentration of NH 4-N. These organic nitrogen compounds would be proteinaceous compounds released fromcells that were lysed during the solubilization of WAS. It is possible that free ammoniawas formed, due to elevated pH (ammonia concentrations were not determined duringthis study).Table 4.6 presents the percent of soluble TKN for all three units and chemicaldosages. Calculations were done with average values for total TKN. The highest percentof soluble TKN was for the unit with sodium hydroxide addition and it increased withtime and chemical dose.63Table 4.5.^Percent NH4 - N in Soluble TKN10 meq/L 15 meq/Ltime0^673^695^567^629^60Ca(OH)267^6768^5659^2860^2557^25ca(OH)270^70^7071^57^6076^5268^51^1661^14Ca(OH)286^90100^56^39100^51100^45^15cont NaOH cont NaOH cont NaOH20 meq/LTable 4.6.^Percent Soluble TKN10 meq/Lcont cont666time0^73^75^87^89^8Ca(OH)2779910NaOH79182122Ca(OH)2791135NaOH79103336ca(011)27121315NaOH817374677789cont15 meq/L 20 meq/L4542.5-40-.............37.5-^ ................^..................^ — ..•zr^ ........32.5-8^9Mixing Time (hours)35-^.......................z30^030^0 4^ 94542.5-440-Ez 37.5•crI 35-z32.5-chemical dose 10 meq/Lchemical dose 15 meq/LMixing Time (hours)chemical dose 20 meq/L644542.5-D, 40-Ez 37.5mik^I 35-Z32.5- 0^1^2^3^4^5^6^7^8^9Mixing Time (hours)^cont^Ca(OH)2 --•■•••• NaOH30Figure 4.9. Phase I - Solubilization of WAS: NH 4-N (mg/L)chemical dose 10 meq/L65300^250-Zi 200-o.)150-100-50 ^0 0^ .......^.....^.......1^2^3^4^5^6^7^8^9Mixing Time (hours)300^250-200-m150-100 -5011• chemical dose 15 meq/L0^1^2^3^4Mixing Time (hours)chemical dose 20 meq/L300250-200-150-I-co100-50-........ ••••-^ -......... .)10 .........4 8^9Mixing Time (hours)-44-- cont^Ca(OH)2^NaOHFigure 4.10. Phase I - Solubilization of WAS: Soluble TKN (mg/L)664.3. SUMMARYFrom the above results and discussion, it can be seen that WAS pretreatment withboth chemicals released significant amounts of carbon, nitrogen and phosphorus intosolution. Increased concentrations of soluble carbon, nitrogen and phosphorus speciesprovided evidence that the particulate forms were solubilized. Concentrations of solubleforms of carbon, nitrogen and phosphorus increased for higher chemical dosages andlonger anoxic mixing times. These results support the data base presented by Rajan etal [1989].Based on these results, it was decided to apply a "compromise" chemical dose of15 meq/L and a mechanical mixing time of 5 hours to the second phase of the research,involving pilot-scale anaerobic sludge digestion of primary sludge plus alkalinesolubilized waste activated sludge.675. PHASE II RESULTS AND DISCUSSION5.1. INTRODUCTIONThe experimental and analytical results are summarized in a series of figures andtables in order to facilitate the presentation of research results. Comparisons betweenthree digesters, one control and two experimental units (exp Ca(OH) 2 and exp NaOH)are drawn within each category of results presented, in order to evaluate the effects ofWAS pretreatment on anaerobic digestion of a mixture of primary sludge and solubilizedWAS.Parameters that were monitored to assess digester performance were: solids,carbon, nitrogen, phosphorus, volatile fatty acids, gas volume and composition, pH,temperature, oxidation-reduction potential and dewaterability.Statistical analysis of the results was done using a small-sample T-test, concerningthe difference between two means [ Miller et al, 1990 ]. This method assumes a normallydistributed population. Population sizes (minimum 30) allowed for the assumption thatthe populations are normally distributed (according to the Central Limit Theorem). Theassumption that the samples are taken from normal populations is not really as stringentas it may seem. Most statistical methods based on normal distribution are fairly robust,that is, they will give reasonably accurate answers even when the normality assumptionis only satisfied in an approximate sense [Miller et al, 1990]. In all calculations, the levelof significance was 0.05. Mean values, standard deviations and variances were calculated68using the statistical portion of Quattro Pro (release 3).5.2. SOLUBILIZATION OF WASTE ACTIVATED SLUDGESolubilization of WAS by the addition of 15 meq/L of calcium hydroxide andsodium hydroxide was monitored (prior to feeding the digesters) throughout all four runsof the second phase. These runs investigated the effect of changing the solids retentiontime (SRT) on digester performance (see Table 3.1).5.2.1. SolidsAs was expected, total solids increased somewhat for WAS treated with chemicals(Figure 5.1). The addition of 15 meq/L of sodium hydroxide and calcium hydroxideintroduced solids into the solution, which was reflected in an increase in total solids. Theopposite trend can be seen for total volatile solids, TVS (Figure 5.2). Total volatile solids(TVS) decreased for the addition of both chemicals during mechanical mixing. Thisdecrease of TVS was due, in part, to the stripping of ammonia from solution because ofthe elevated pH values and also to a loss of ammonia during firing of samples. pH valuesfor pretreated WAS were in the range of 9.0 to 10.0.20^4'0^So^So^100Total Running Time (days)160120111098765469— WAS — Ca(OH)2 NaOHFigure 5.1. Phase II - Solubilization of WAS: Total Solids (mg/L)run # 1 run^#2 run # 3 run # 4t. ,51\V \20^40^60^80^100^120^140^160Total Running Time (days)— WAS — Ca(OH)2 NaOHFigure 5.2. Phase II - Solubilization of WAS: Total Volatile Solids (mg/L)70The addition of chemicals also resulted in the rupturing of bacterial cellmembranes (as was shown in Phase I of this research); therefore, suspended solids andvolatile suspended solids decreased (Figure 5.3) while dissolved solids increased.Table 5.1 summarizes percent VSS destruction during solubilization of WAS. Itcan be seen that the addition of sodium hydroxide was more effective in lysing the cellsthan calcium hydroxide.Table 5.1.^Average Percent of VSS Destruction During SolubilizationNaOH19232728 run #1234WAS Ca(OH)27129121110987654371run # 1 run # 2 run # 3 run # 4,: '^v-::L,...% ...,..,.,11.i 1.,.I20^ 60^80^ 100^20^140^160Total Running Time (days)— WAS — Ca(OH)2 ^ NaOHFigure 5.3. Phase II - Solubilization of WAS: Volatile Suspended Solids(mg/L)5.2.2. Chemical Oxygen DemandSoluble COD in non-treated WAS was very low, whereas soluble COD, after 5hours of anoxic mixing with chemicals, increased significantly for both chemicals (Figure5.4). From Table 5.2 it can be observed that percent of soluble COD was 2.0 to 3.5times higher for sodium hydroxide addition than for calcium hydroxide addition. This72support the results obtained in Phase I of this resesarch and alos the resultes reported byRajan et al [1989].Table 5.2. Average Percent of Soluble COD in WAS With and WithoutPretreatmentrun # WAS Ca(OH)2 NaOH1 .4 9.2 18.52 .5 8.2 21.73 .8 6.9 24.64 .8 10.7 27.75.2.3. Total Organic CarbonThe concentration of organic carbon in solution was very low, only 6 -29 mg/Lfor non-treated WAS. From Figure 5.5 it can be seen that TOC concentration increasedwith the addition of both chemicals. Again, as for soluble COD, the addition of sodiumhydroxide released much more organic material into the solution than the addition ofcalcium hydroxide.Good correlation between TOC and soluble COD (Figures 5.6 and 5.7) allow fora 2500rnE--co 2000O0150035003000400010005000 0^20^40^60^80^100Total Running Time (days)— WAS — Ca(OH)2 NaOHFigure 5.4. Phase II - Solubilization of WAS: Soluble COD (mg/L)run # 1 I run # 2irun # 3\ i.,run # 4..•\ /^v• .;^.\ .-• .-^•• I..^,V VI \ ifV/i\V\-.',- V1---„/120 140 160the conclusion that the constant fraction of the COD was due to organic carbon.73120010008006004002000run# 1„,......1.--.^/^\r^V^V„...,.^.^v,...^//run# 2/•.^.^..,..\NA \ 'A„,.....A.Arun# 3AC'v.... run # 4;^•jAvNrAv20^40^ 1^120^1^160Total Running Time (days)— WAS — Ca(OH)2 NaOHFigure 5.5. Phase II - Solubilization of WAS: Total Organic Carbon (mg/L)460^660^860^lowCODs (mg/L)1200 1400 160074Figure 5.6. Phase II - Solubilization of WAS: Correlation Between TOC -soluble COD for Ca(OH)2 Addition to WAS200500^1000^1 500^2000^2500^3000CODs (mg/L)Figure 5.7. Phase II - Solubilization of WAS: Correlation Between TOC -soluble COD for NaOH Addition to WAS755.2.4. NitrogenRelease of different forms of nitrogen into solution was also a good indicator ofWAS solubilization. The concentrations of both soluble TKN and NH 4-N increased withthe addition of calcium hydroxide and sodium hydroxide (Tables 5.3 and 5.4). Theconcentration of NH4-N increased for pretreated WAS, but the percent of NH 4-N insoluble TKN actually decreased. The concentration of soluble TKN was much higherthan NH4-N concentration. This leads to a conclusion that the concentration ofproteinaceous compounds (organic nitrogen forms) released by rupturing the bacterial cellmembranes increased and that these compounds were the major constituents of solubleTKN in WAS pretreated with chemicals. It is possible that, due to the elevated pH, theTable 5.3.^Average Concentration of Soluble TKN (mg/L) in WAS With andWithout Pretreatmentrun # WAS Ca(OH)2 NaOH1 6.7 94.5 185.52 5.2 103.6 264.83 8.3 86.9 277.94 6.8 90.2 244.176Table 5.4.^Average Concentration of NH 4-N (mg/L) in WAS With andWithout Pretreatmentrun # WAS Ca(OH)2 NaOH1 4.1 15.2 19.42 2.6 15.0 16.43 4.8 16.7 19.34 4.2 12.2 14.4fraction of NH4-N pool was converted to free ammonia (as mentioned in Section 4.2.6,amminia concentrations were not determined). The percent of nitrogen compounds otherthan NH4-N, increased from 40 - 50 in non-treated WAS, to 90 - 94 in WAS treated withsodium hydroxide and 81 - 86 in WAS treated with calcium hydroxide.5.2.5. PhosphorusWAS used in this study was rich in phosphorus, since it was supplied from theUBC pilot plant which operates as a phosphorus removal facility. From Figures 5.8 and5.9 it can be observed that the release of phosphorus was significant for the addition ofsodium hydroxide but not for calcium hydroxide addition; this can be attributed to theprecipitation of phosphorus as calcium phosphate.The major portion of soluble phosphorus was in the PO 4-P form, 69 to 10077percent (Table 5.5).Table 5.5.^Average Percent of PO4-P in Soluble TP With and WithoutPretreatmentrun # WAS Ca(OH)2 NaOH1 97 82 722 97 87 683 91 91 694 100 86 75300250200E 15013_100500run # iA.:...../run#2/^\♦,\run # 3\-^•- . •run #4A^,1^ :_1--0^20^40^60^80^1^120^140^160Total Running Time (days)— WAS — Ca(OH)2 NaOHFigure 5.8. Phase II - Solubilization of WAS: Release of Phosphorus: SolubleTotal Phosphorus (mg/L)78(mg/L)Eai - 1502002505000^20^40^6080^100Total Running Time (days)— WAS — Ca(OH)2 --- NaOHFigure 5.9. Phase II - Solubilization of WAS: Release of Phosphorus: PO4-Prun # 1 run # 2A/!run # 3Arun # 4L;; .; ‘I 'vi... ;A,^IA II ..^;1 .1 A I  if. 1 a i 1 ; I',...,11*I^/  1%,,i..s120 1 40 160795.3. DIGESTER PERFORMANCEThe characteristics of WAS and primary sludge used in this study were subjectto normal variability as a result of the daily and the seasonal fluctuations in operation ofthe UBC pilot plant. However, the use of the control reactor allowed for valid relativecomparisons between reactors; therefore, adjustment of influent characteristics betweenruns was not done. This kind of variability is also common in the "real world" so it wasfelt that, by not adjusting influent characteristics, this study would give more "real"results.5.3.1. pH and TemperatureOne of the most important environmental conditions for successful anaerobicdigestion is proper pH. During this study pH was monitored on a daily basis and properaction was taken to maintain pH in the range of 6.6 to 7.2. Target pH in the digesterswas maintained by sodium bicarbonate addition.Figure 5.10 presents effluent pH profiles for all three units. It can be seen thatpH was the lowest in the control unit and the highest in the exp NaOH unit. This wasthe consequence of the chemical addition to WAS for the experimental units - influentpH for the experimental units was higher than influent pH for the control unit. Therefore,chemical addition to WAS had a beneficial effect on pH values in the digesters. From80the same Figure it can be seen that the addition of sodium hydroxide was able tomaintain a higher pH than the addition of calcium hydroxide. It should be mentioned herethat, although pH values in WAS were elevated up to 9.0 to 10.0 during thesolubilization process, influent pH values (pretreated WAS + primary sludge) werebetween 6.1 to 8.4 for the exp Ca(OH) 2 unit and between 6.6 to 9.5 for the exp NaOHunit.As noted, target pH was maintained by sodium bicarbonate addition. As SRT wasdecreased, the need for pH adjustment increased. Table 5.6 summarizes the averagenumber of sodium bicarbonate additions. It can be seen that the addition of sodiumbicarbonate increased from once every 16 - 17 days for the control unit and once every25 days for both experimental units during the 25 day SRT run, to once every 3 days forthe control unit and once every 3.5 days for the experimental units at the 10 day SRT.At the same time, however, accumulation of VFA's was not detected, nor was there anincrease in carbon dioxide production. Since anaerobic digestion is a very complexprocess with a number of reactions happening at the same time, a pH decrease cannotbe attributed to only one prevalent reaction. pH change is rather a function of manyreactions taking place during digestion; however, it was not in the scope of this work tostudy pH change in detail. At this time, a satisfactory explanation for the behaviour ofdigester pH values is not possible.Temperature profiles for the effluents are presented in Figure 5.11. It can be seenthat effluent temperature was quite stable and that there was not any significant differencebetween effluent temperatures from different units. It can be also noted that effluent81temperature was slightly higher than ambient temperature (35°C), indicating that reactionsduring anaerobic digestion are exothermic and produce additional heat.SRT = 25 SRT = 20 SRT = 15 SRT = 10..10;4‘1. •20^40^60^80^1^120^140^160Total Running Time (days)— cont^exp Ca(OH)2^exp NaOHFigure 5.10. Phase II - Performance of Digesters: Effluent pH ValuesTable 5.6.^^Average Number of Sodium Bicarbonate Additions per SRTSequence, to Maintain Desired pH Rangerun #i cont exp Ca(OH)2 exp NaOH length of run (days)1 ( SRT=25 ) 3 2 2 502 ( SRT= 20 ) 3 3 3 403 ( SRT= 15 ) 5 5 5 304 ( SRT=10 ) 1 1 10 10 357.57.47.37.27.1I 7a6.96.86.76.66.5a)EI-82.41JSRT = 25 SRT = 20 S RT = 15 SRT = 1039-. t.. I.% i f i^yrl AM;37-I36-35-34 ,..Total Running Time (days)— cont^— exp Ca(OH)2 ^ exp NaOHFigure 5.11. Phase II - Performance of Digesters: Effluent Temperatures (°C)5.3.2. Oxidation - Reduction PotentialORP measurements were taken as an indicator of anaerobic conditions indigesters. Unfortunately, it was not possible to take ORP measurements for the controlunit since a built-in port for the ORP probe was not big enough. Both experimental unitshad ORP values regularly between -220 mV and -315 mV, which was consideredindicative of a true anaerobic environment. There was no reason to believe that theU^40^bU^tSU^100 140 083control unit was anything other than fully anaerobic, despite the lack of ORP readings.5.3.3. SolidsOne of the most important parameters in assessing digester efficiency is reductionin volatile sludge mass over a specific period of time. The process efficiency wascalculated using a mass balance approach, which can be expressed by the followingequation:change in mass = amount in - amount out ± net change within system ( 5.1.)(influent) (effluent)^(change in digester mass)The determination of daily solids concentrations in both influent and effluent sludgeallowed for the use of this mass balance approach. All solids added/removed from thesystem, during a particular run, were used to calculate a single value for percent solidsreduction during that run. The equation used for calculating percent solids reduction isas follows:% solids reduced =— re4 CeVe - ACRVR^  100^( 5.2.)E7-1  CiP7where: Ci - concentration of solids in influent (mg/L)Vi - daily volume of influent (L)Ce - concentration of solids in effluent (mg/L)Ve - daily volume of effluent (L)84CR - concentration of solids in reactor (mg/L)VR - volume of reactor (L)n - number of days in the runSince, in this study, solids were reduced during the solubilization process itself,as well as during subsequent digestion in the reactors, percent solids reduction wascalculated as:1. Digester Solids Removal, in which case Ci = concentration of solids in influent(WAS + primary sludge) after solubilization of WAS2. Overall Solids Removal, in which case Ci = concentration of solids in influent(WAS + primary sludge) before solubilization of WAS; that is, overall solidsremoval accounting for solids removal during solubilization of WAS plus removalof solids in the reactor.In order to calculate overall solids removal or reduction, it was necessary tocalculate the concentration of solids in influent before WAS was solubilized for thosedays when samples of raw WAS and WAS after 5 hours of mechanical mixing were nottaken. This was done using the following equation:VTVSS' = VTVSS + VwAs OVSSwAs^( 5.3.)From Equation 5.3:VSS' = VSS( 1 + 0.65R)^ ( 5.4.)where: VSS' - VSS concentration in influent before WAS pretreatment (mg/L)VSS - VSS concentration in influent after WAS pretreatment (mg/L)VT^- total volume of influent (L)SRT = 25 SRT = 20 SRT = 15 SRT = 10I ilinfluentI•V1lii .j zC1 .• effluent-- -1-•-•.y^_.^ .16141264285VwAS^- volume of WAS in influent (L)ovss WAS change in VSS during solubilization of WAS (mg/L)R - average value of OVSSwAs/VSS for particular runVWAS/VT = 0.650^2 4^60^BO^100^120^140^160Total Running Time (days)— cont^— expCa(OH)2^expNaOHFigure 5.12. Phase II - Performance of Digesters: Influent and EffluentConcentrations of Volatile Suspended Solids (mg/L)Figure 5.12 indicates that the effluent VSS concentration from all three units was86relatively stable and that influent VSS concentrations were highly variable (as expected).It can be observed from the same Figure that during the second and third run, (SRT of20 and 15 days), the VSS concentration in the effluent was higher than for the fourthrun (SRT of 10 days), due to the fact that influent VSS levels were somewhat higherduring these two runs.Table 5.7 summarizes percent digester VSS reduction. It can be seen that theefficiency of VSS reduction was very stable from run to run, for all three digesters. SRTdid not have any significant influence on digester performance. It is also apparent thatthe same efficiency in VSS reduction was achieved for all three units, at any particularSRT. Such stable digester VSS reduction was attributed primarily to excellent mixing ofthe digester contents.Table 5.7.^Average Values of Digester VSS Reduction (%)SRT (days) cont exp Ca(OH)2 exp NaOH25 47 47 4820 49 48 4815 48 46 4810 48 48 46A summary of overall VSS reduction is presented in Table 5.8. For the control87unit, digester VSS reduction equalled overall VSS reduction, since WAS was notsolubilized in this unit. It can also be noted that overall VSS reduction for the control andboth experimental units was not a function of SRT. If the performance between reactorsis compared, than it can be readily seen that both experimental units achieved betteroverall VSS reduction than the control unit (in some cases as much as 6 percent higher,on average). Better VSS reduction was attributed to solids destruction during thesolubilization process beforehand and not to better digester performance, per se. It canbe also observed that the best overall VSS reduction was achieved in the exp NaOH unit.Effluent quality, in terms of VSS concentration, can be compared betweendifferent runs for the same reactor, between different reactors during the same run andbetween different runs and different reactors. The most important results of this analysisare summarized in the following section.Table 5.8.^Average Values of Overall VSS Reduction (%)SRT (days) cont exp Ca(OH), exp NaOH25 47 51 5320 49 52 5515 48 49 5410 48 51 5488Effluent VSS concentrations for the 25 day SRT run and 10 day SRT run werenot statistically different for any of the units. This means that SRT can be decreased fromthe usual 25 days to 10 days without losing VSS reduction efficiency (see Appendix C).If effluent VSS concentrations for the control unit and the exp Ca(OH)2 unit arecompared, it was found that for all runs, except the 20 day SRT run, these two unitswere not statistically different. For the 20 day SRT run, the effluent VSS concentrationwas about 5 % higher for the control unit. If the control and exp NaOH units arecompared (see Appendix C), for all four runs, the effluent VSS concentration was higherin the control unit (for the 25 day SRT run, 5 percent and for all other runs, 10 percenton average). This leads to the conclusion that the control and exp Ca(OH) 2 units had thesame effluent quality, with respect to volatile solids, whereas the exp NaOH unitproduced better effluent quality, with lower VSS concentrations.Finally, if effluent VSS concentrations for the control unit during the 25 day SRTrun and effluent VSS concentrations for the exp NaOH unit during the 10 day SRT runare compared (extreme cases), it was found that the SRT for the exp NaOH unit couldbe decreased to 10 days without decreasing VSS reduction efficiency. Effluent VSSconcentrations for the exp NaOH unit were even lower than the control unit effluent VSSconcentrations at the 25 day SRT run.The inorganic content of the effluent sludge was calculated as a differencebetween TS and TVS. It can be seen from Table 5.9 that all three digesters had roughlythe same average inorganic content during the 25 day SRT run. It is also apparent thatthe inorganic content was much higher than for any other SRT run. This was probably89due to the high inorganic content of the Lions Gate sludge (used as a seed), which wasstill present in the digesters. The inorganic content decreased during the 20 day SRT runfor all three digesters. During the entire experiment, the inorganic content in the expCa(OH) 2 unit was the highest, whereas the control and exp NaOH units had similarconcentrations of inorganic material during all four runs.Table 5.9.^Average Effluent Concentrations of Inorganic Material (mg/L)SRT (days) cont exp Ca(OH)2 exp NaOH25 2860 2894 282420 2322 2410 232215 2524 2731 243410 2417 2606 24835.3.4. Carbon Content and RemovalCarbon content of the digester mixed-liquor was monitored through thedetermination of soluble and total COD, as well as soluble TOC.90Using a mass balance approach similar to that used for the analysis of volatilemass reduction, carbon removal (in terms of COD removal) was calculated and ispresented in Table 5.10. Since samples for carbon content were not taken on a dailybasis, the average value of carbon content was calculated for each run and each digesterand that value was used in mass balance calculations.A number of trends can be discussed. For all three digesters, removal of totalCOD increased with a decrease in SRT, reflecting a higher metabolic activity, as afunction of higher organic loading with decreasing SRT. Also, it can be seen that totalCOD removal was higher for both experimental units, with exception of the exp Ca(OH)2unit for 20 day and 15 day SRT runs. The best total COD removal was achieved in theexp NaOH unit at each SRT tested.Table 5.10. Carbon Removal (kg/day): COD basisSRT total^COD^removal soluble^COD^removal(days) cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH25201510.0366.0571.0696.0882.0332.0644.0729.0776.0041.0091.0127.0190.0009.0014.0029.0055.0375.0697.0749.091691An overall increase in soluble COD removal can be observed for bothexperimental units, but little or no soluble COD removal in the control unit; the effluentconcentration of soluble COD was always higher than the influent concentration (Figure5.13). This may be due, in part, to the fact that the solubilization of WAS for the controlunit actually took place inside the digester. Again, the best soluble COD removal wasachieved in the exp NaOH reactor, at each SRT.It can be seen from Table 5.11 that effluent TOC concentration increased for thecontrol unit, as SRT decreased to 10 days. This indicates that microorganisms didnot have enough time at the shorter SRT's to utilize the soluble carbon present in thereactor. For both experimental units, the effluent TOC concentrations increasedsignificantly from the 25 day SRT run to the 20 day SRT run, but became stable at thelower SRT's. This indicates that the quality of the control unit effluent (with respect toorganic carbon) kept deteriorating, while the quality of the experimental unit effluentremained fairly constant, below an SRT of 25 days.Influent TOC concentrations were much higher for both experimental units thanfor the control unit (consequence of WAS solubilization), meaning that soluble carbonwas readily available to microorganisms in both experimental units right after thefeeding/wasting process.Percent removals shown in Table 5.11 verify that the rate of carbon utilizationwas much higher in both experimental units than in the control unit. It can be also seenthat the utilization rate was the highest in the exp NaOH unit.92/I1Ar^ISRT = 25,%,‘ SFR = 20I ,• A/^1^t ',4•••• ''^/' ' ^%/^V^\^1• '..., /• ,V,SRT" = 15 A^f ^',• .s^.1^I, /^\^1^1■ ,; ,^I,.( I^VII.1A•■.,..‘SAT = 10 ,e/t^', e• I,^■ ..^%^1; \ ,....■ •• • , •I' \ •^Si ti , I^•I..• /• , \ i's1„  ' VIV S / .... I 1 ' IlifI;^; ■^•••: ' • %. %. ..6.'".• /„; i .• 1^ . : -: .. ! ... ■ fl ....• 1^■ 0. ." 1^"VIf.^.,: "4... ..'. ........ ., ...............o20^40^60^80^1^120^1^160Total Running Time (days)^— cont4nf   expCa(OH)24nf^expNaOH-infcont-eff   expCa(OH)2-eff^expNaOH-effFigure 5.13. Phase II - Performance of Digesters: Influent and EffluentConcentrations of Soluble COD (mg/L)Table 5.11. Average TOC Concentrations (mg/L)SRT(days)cont exp^Ca(OH)2 expNaOHinf eff % rem inf eff % rem inf eff % rem25 91 23 74.7 264 21 92.0 415 34 91.820 62 44 29.0 212 55 74.0 499 94 81.215 112 77 31.2 232 67 71.1 526 89 83.11 0 100 84 16.0 239 64 73.2 476 93 80.52000-E0010-0935.3.5. Gas production and compositionThe volume of gas produced during digestion was recorded at a temperature of35°C, although gas was produced at the higher temperature (on average 37-38°C). Thetemperature of 35°C was used since it was the ambient operating temperature and gasproduced in the digesters had to travel through collection lines before its volume wasrecorded on the gas meters. This volume of gas was then calculated for standardtemperature of 20°C according to the generalized Gas Law:p iV I /Ti = p2V2/T2^( 5.5.)All further calculations were done using the corrected values for gas volume.Table 5.12 summarizes gas production during all four runs. It can be seen thatthe volume of gas produced increased from the longer to shorter SRT's. Differencesbetween the control and the exp Ca(OH) 2 unit were not statistically significant,Table 5.12. Average Volume of Gas Produced (L/day) Corrected to 20°CSRT (days) cont exp Ca(OH)2 exp NaOH25 18.2 19.8 22.220 30.6 31.2 34.915 42.4 41.7 45.910 48.6 49.9 56.094throughout all four runs. The exp NaOH unit had the highest daily gas production. Sincevolume of gas is directly proportional to the strength of influent sludge, comparison ofdigester performance by total volume of gas produced can be misleading. In order toimplement a true comparison of digester performance, the volume of gas produced perkilogram of VSS reduced was calculated (Table 5.13). These values are defined as "unitgas production".A number of trends can be discussed form Table 5.13. The best unit gasproduction was achieved in the exp NaOH unit. Unit gas production increased for allthree digesters at any particular SRT. An increase in unit gas production, at less than a15 day SRT, was only observed for the exp NaOH unit whereas, for the control and expCa(OH) 2 units, the unit gas production decreased when the SRT decreased to 10 days.This can be also seen from Figure 5.14. Both the control and exp Ca(OH) 2 digesters hadtheir maximum unit gas production during the 15 day SRT run. Although unit gasproduction for the exp NaOH unit was still increasing at the 10 day SRT, it is likely thata maximum value would have been reached for a shorter SRT, since the rate of increasehad leveled off.Table 5.14 summarizes methane production per total COD removed. It can beseen that presented values are very close to the theoretical value of 350 L of methane perkg of COD removed.The major portion of the gas produced in all three units was methane. The percentmethane was stable throughout the whole experiment, for all three digesters. It wasalways slightly higher in both experimental units (Figure 5.15). The second most95always slightly higher in both experimental units (Figure 5.15). The second mostTable 5.13. Average Volume of Gas Produced per Mass of VSS Reduced inDigesters (L/kgVSSreduced) Corrected to 20°CSRT (days) cont exp Ca(OH)2 exp NaOH25 558 658 82220 770 849 109215 884 957 112010 799 881 1149Table 5.14. Volume of Methane Produced per Mass of Total COD Removed(L/kg CODt)SRT (days) cont expCa(OH)2 expNaOH25 322 324 35620 269 318 29815 318 337 35110 348 320 358SRT=10SRT=25^SRT=20^SRT=15SRT (days)120011001000900800/700 ^600^/500Figure 5.14. Phase II - Performance of Digesters: Average Gas Production (Lof gas/kg VSS reduced)96expNaOHexpCa(OH)2cont0^40^60^ 1^120^140^160SRT = 25 SRI = 20 SRT = 15 SKr = 10: \- . \7065. 60I05550097Total Running Time (days)- cord^- exp Ca(OH)2 -- exp NaOHFigure 5.15. Phase II - Performance of Digesters: Methane Content (%)Table 5.15. Average Composition of Digester Gas (%)cont exp^Ca^(OH)2 exp^NaOHS CH4 CO2 N-2, other CH4 CO2 N2 other CH,, CO2 N2 otherRT25 58.7 39.5 1.5 .3 59.8 37.2 2.7 .3 60.4 36.8 2.5 .320 56.9 41.8 1.2 .1 58.8 39.8 1.4 59.8 39.0 1.415 56.1 42.8 1.1 57.6 40.7 1.7 58.6 40.8 .610 55.5 43.6 .9 57.0 41.0 2.0 59.0 40.7 .3985.3.6. NitrogenEffluent concentrations of soluble nitrogen forms, from all three units, were high,higher than influent concentrations. From Table 5.16 it can be seen that the percent oftotal soluble nitrogen (determined as soluble TKN) in the effluent was stable throughoutthe whole experiment for all three digesters; it was always the highest for the exp NaOHunit.Effluent concentrations of soluble TKN are presented in Table 5.17. It can beseen that the highest soluble TKN was in the exp NaOH effluent, whereas effluents fromthe control and exp Ca(OH) 2 units contained almost the same soluble TKNconcentrations. The major portion of effluent soluble TKN was in NH 4 +-N form (TableTable 5.16. Average Percent of Effluent Soluble TKN in Total TKNSRT (days) cont exp Ca(OH)2 exp NaOH25 45.4 46.1 48.320 44.5 45.2 49.615 45.4 44.0 49.510 45.2 44.4 50.3average 45.1 44.9 49.45.18) and average values were about the same for all three digesters.Table 5.17. Average Effluent Concentrations of Soluble TKN (mg/L)SRT (days) cont exp Ca(OH)2 exp NaOH25 216 222 22720 269 270 29115 264 261 28310 210 199 224Table 5.18. Average Percent of Effluent NH 4+-N in Soluble TKNSRT (days) cont exp Ca(OH)2 exp NaOH25 77.8 79.1 78.320 77.3 81.2 77.215 79.8 84.8 82.110 80.7 75.5 78.2average 78.9 80.1 78.999100From the results presented above, it can be concluded that pretreatment of WASdid not have any significant impact on effluent quality in terms of nitrogen speciespresent.5.3.7. PhosphorusWAS used in this study was rich in phosphorus (as explained in Section 3.1), sohigh effluent concentrations of phosphorus were expected. It can be seen from Table 5.19that almost all soluble phosphorus was in the PO4-P form; from 91 to 100 percent. Theconcentration of PO4-P in the effluent from the control and exp NaOH units werecomparable (Table 5.20) but exp Ca(OH) 2 effluent always had considerably lower PO 4-Pconcentrations. The same can be seen for soluble TP concentrations (Figure 5.16). LowerTable 5.19. Average Effluent Percent of PO4-P in Soluble TPSRT (days) cont exp Ca(OH)2 exp NaOH25 94 95 9620 94 91 9615 98 92 10010 100 97 99101Table 5.20. Average Effluent Concentrations of PO 4-P (mg/L)SRT (days) cont expCa(OH)2 expNaOH25 91.4 81.8 97.720 135.4 94.7 143.115 163.7 104.8 168.410 131.6 84.7 132.9soluble phosphorus concentrations in the exp Ca(OH) 2 effluent was due to phosphorusprecipitation with calcium hydroxide. It can be observed from Figure 5.16. and also fromTable 5.20, that effluent phosphorus concentrations for all three units increased duringthe 20 day and 15 day SRT runs, whereas for the 25 day and 10 day SRT runs, theseconcentrations were much lower. This pattern was also seen for most nitrogen species,carbon and solids and it can be attributed to variations in influent concentrations ofphosphorus, nitrogen and carbon (influent concentrations were somewhat higher duringthe 20 day and 15 day SRT runs due to variations in sludge quality from the UBC pilot-plant - see Appendix D for raw data).From the data presented, it can be concluded that WAS pretreatment with sodiumhydroxide did not have any significant impact on effluent quality, compared to thecontrol. When calcium hydroxide was used for WAS pretreatment, a decrease in solublephosphorus concentration in the effluent was significant. This may have importantSRT = 25 SRT = 20,$RT = 15:i.SRT = 10- ....... -....!.^. -180170160150140% 130Eco120i--110100908070102ramifications if bio-P sludge is to be treated in this manner, in conjuction with primarysludge.0^20 40^60^80^100^120^140^160Total Running Time (days)— cont-eff^— expCa(OH)2-eff --- expNaOH-effFigure 5.16. Phase II - Performance of Digesters: Effluent Concentrations ofSoluble TP (mg/L)1035.3.8. Volatile Fatty AcidsVolatile fatty acids that were determined were: acetic, propionic, isobutyric,butyric, 2-methyl butyric, 3-methyl butyric, valeric and hexanoic. VFA concentrationwas expressed in mg/L as acetic acid. The most important VFA is acetic acid, since itis a direct precursor for methane production. Table 5.21 presents average VFAconcentrations in the influent and also gives the average percent of acetic acid in theinfluent. Influent VFA concentrations were always higher for both experimental unitsthan for the control unit. The concentration of acetic acid in influent was stable and itwas between 58 and 65 percent.Effluent VFA concentrations were always low (Table 5.22). The highest effluentVFA concentrations were observed in the exp NaOH unit. However, these concentrationswere also low and never higher than 13 mg/L as acetic acid. The major constituent ofeffluent VFA's was acetic acid (up to 100 percent).Low concentrations of VFA in effluent indicate that VFA's did not accumulatein the digesters and that the decrease in digester pH noted earlier was due to otherbiomechanisms occuring in the digesters.104Table 5.21. Average Influent VFA Concentrations (mg/L) as Acetic Acid andAverage Percent of Acetic Acid in InfluentSRT(days)cont exp^Ca(OH), exp^NaOHVFA % acet. ac. VFA % acet. ac. VFA % acet. ac.25 119 61 230 62 233 6220 93 65 183 62 227 6115 122 58 176 62 203 5810 114 58 178 62 161 58Table 5.22. Average Effluent VFA Concentrations (mg/L) as Acetic Acid andAverage Percent of Acetic Acid in EffluentSRT(days)cont exp^Ca(OH)2 exp^NaOHVFA % acet. ac. VFA % acet. ac. VFA % acet. ac.25 4 88 5 92 8 8520 4 100 7 87 10 8515 6 95 8 84 11 7610 10 78 12 76 12 731055.3.9. Sludge DewaterabilityDigested sludge dewaterability was determined by measuring capillary suctiontime (CST). Higher CST values indicate lower dewaterability. It can be seen from Figure5.17 that all three units had similar sludge dewaterability at the begining of theresearch.After 20 days, differences in dewaterability were very noticeable. The bestdewaterability was achieved in the exp Ca(OH)2 unit throughout the whole experiment.The exp NaOH unit had the lowest (i.e. worst) dewaterability, although, at times, CSTvalues were close to the control unit dewaterability. It can be concluded that the additionof sodium hydroxide had an overall negative effect on sludge dewaterability, whereascalcium hydroxide addition was beneficial. It can be also noted that dewaterability wasnot a function of SRT in this research. Consideration of the above results should beaccounted for in an overall evaluation of cost-benefit analysis for pretreatment of WAS.5.4. SUMMARYAs a summary to the discussion of the results contained in this Chapter, Table5.23 is presented.SRT = 25 SRT = 20 SRT = 15 SRI = 10,...\.......\..-...--,.. ......•^.20 40^60^80^100^120^140^16045403520151 0025106Total Running Time (days)— cont^exp Ca(OH)2^exp NaOHFigure 5.17. Phase II - Performance of Digesters: Sludge DewaterabilityNotable from Table 5.23 are the following key observations: the same digesterVSS reduction values throughout all four runs for all three digesters; better overall VSSreduction in both experimental units and the best overall VSS reduction in the exp NaOHunit; better total and soluble COD removal in both experimental units and the best CODremoval in the exp NaOH unit; an increase in total and soluble COD removal with a107decrease in SRT; better unit gas production in both experimental units and the best unitgas production in the exp NaOH unit; an increase in unit gas production in all threedigesters with a decrease in SRT to 15 days; a continued increase in unit gas productionfor the exp NaOH unit during the 10 day SRT run but a decrease for the control and expCa(OH)2 units; a higher content of methane in the off gas in both experimental units; anincrease in effluent TOC concentration with a decrease in SRT; higher effluent TOCconcentrations in the exp NaOH effluent for all four runs, compared to the control uniteffluent, whereas the exp Ca(OH) 2 effluent had lower TOC concentrations during the 15day and 10 day SRT runs; an increase in effluent VFA concentrations with a decreasein SRT; the lowest effluent VFA concentrations found in the control unit during all fourruns; an increase in effluent total and soluble TKN during the 20 day and 15 day SRTruns but decreasing for the 10 day SRT run; somewhat higher effluent concentrations ofsoluble nitrogen forms (soluble TKN and NH4-N) in the experimental units; the sameeffluent total TP concentrations for all three units, during all four runs; an increase ineffluent PO4-P, total and soluble TP during the 20 day and 15 day SRT runs and adecrease for the 10 day SRT run for all three digesters; the same effluent concentrationsof soluble TP and PO4-P in the control and exp NaOH units, but lower concentrationsin the exp Ca(OH) 2 unit.It is evident from Table 5.23 that WAS pretreatment did influence, and in manycases, enhance anaerobic digestion. If the control unit performance at SRT = 25 daysand the performance of the experimental units at SRT = 10 days is compared (i.e.extreme runs), then it is notable that: digester VSS reduction was about the same for allTable 5.23. Summary of Digester Performance and Effluent Qualityparameter SRT^= 25^days SRT^= 20^days SRT^=^15^days SRT^= 10^dayscont expCa(OH)2expNaOHcont expCa(OH)2expNaOHcont expCa(OH)2expNaOHcont expCa(OH)2expNaOHdigest. 47 47 48 49 48 48 48 46 48 48 48 46VSSred.^%overall 47 51 53 49 52 55 48 49 54 48 51 54VSSred. %CODt rem.(kg/thy).0332 .0366 .0375 .0644 .0571 .0697 .0729 .0696 .0749 .0776 .0882 .0916CODs rem.(kg/day)unit gas prod. 558.0009658.0041822 770.0014849.00911092 884.0029957.01271120 799.0550881.01901149(L/kgVSSrem)% CH,unit CH4 prod.58.732759.839460.449756.943858.849959.865356.149657.655258.665655.544457.050259.0678(L/kgVSSrem)eff TKNt(mg/L)eff TKNs(mg/L)eff NH4-N476216168482222176471227178605269208597270219587291224582264211594261222571283232464210210448199199446224224(mg/L) 800eff TN (mg/L) 159 162 159 222 221 218 246 248 242 197 193 190eff TPs(mg/L)eff P0,-P(mg/L)eff TOC(mg/L)eff VFA(mg/L)989123486822151029834814413544410495557149143941016816477611310567816916889111321328410888564121351339312CF1 4/CODrem 322 324 356 269 318 298 318 337 351 348 320 358(L/kgCODtrm)110three units; overall VSS reduction was better in both experimental units, with the expNaOH unit being the best; total and soluble COD removal was better in bothexperimental units,with the highest in the exp NaOH unit; unit gas production was higherin both experimental units, with the exp NaOH production being the highest; methanecontent was higher in the exp NaOH unit but lower in the exp Ca(OH) 2 unit comparedto the control unit; effluent concentrations of TOC, VFA and total TP increased for bothexperimental units; effluent concentrations of total and soluble TKN were lower for bothexperimental units; effluent concentrations of N1-14-N increased for both experimentalunits; effluent concentrations of soluble TP and PO4-P were lower for the exp Ca(OH) 2unit but higher for the exp NaOH unit.From the preceding discussion it can be concluded that WAS pretreatment hadsignificant beneficial effects on the anaerobic digestion of combined wastewater sludges,especially if volatile mass reduction, COD removal and methane production areconsidered as the most important performance indicators.As discussed earlier, Mavinic and Anderson [1990] reported a noticeable decreasein digester efficiency (with respect to VSS reduction) with the addition of WAS. Theyalso found that the differences in gas production between control and experimentalreactors were also quite evident, in that the gas production (both in terms of overallvolume produced and volume produced per unit mass of COD destroyed) decreased asthe proportion of WAS in the digester increased. They concluded that the addition ofWAS to the anaerobic digester will result in a decrease in digester operational efficencyand that it may substantially hinder plant operations. Contrary to this, if low-level111alkaline pretreatment of WAS is applied, the efficiency of the process increases, as foundin this research and research conducted by Ray et al [1990].1126. CONCLUSIONS AND RECOMMENDATIONS6.1. CONCLUSIONSDuring the course of this pilot-scale research, a detailed examination wasundertaken of the performance and enhancement of the anaerobic sludge co-digestionprocess (35 percent primary sludge and 65 percent WAS) through solubilization of WAS.Solids Retention Times studied were 25, 20, 15 and 10 days, at 35°C operatingtemperature. Chemicals used for solubilization of WAS were calcium hydroxide andsodium hydroxide at a dose of 15 meq/L. From this examination, the following majorconclusions can be drawn:1. Solubilization of WAS can be effectively performed using both chemicals separately:calcium hydrOxide and sodium hydroxide. However, for the same chemical dosage,sodium hydroxide was more effective in WAS solubilization and it released muchmore organic material into solution.2. The addition of chemicals during WAS solubilization had a beneficial effect ondigester pH. Both experimental units had a slightly higher pH than the control unit,resulting in less frequent buffering requirements. A decrease in digester pH was morepronounced during shorter SRTs. However, a decrease in digester pH was not due toaccumulation of VFA's, since effluent concentrations of VFA's was always low for113all three units.3. Solubilization of WAS did not have any appreciable effect on actual digester VSSreduction efficiency; all three digesters had similar digester VSS reductions, a resultof excellent mixing conditions in each unit. However, there was no detrimental effecton digester efficiency due to the addition of the solubilized WAS. Any differencesbetween digesters were not statistically significant. Also, digester VSS reductionefficiency was not a function of SRT; all three units had stable digester VSS reductionefficiency throughout all four runs.4. Better "overall" VSS reduction was achieved in the experimental units; this wasattributed to the destruction of solids during the solubilization process. Overall VSSreduction was not a function of SRT. The best overall VSS reduction was achievedin the exp NaOH unit and it was due to better efficiency in solubilization of WAS bysodium hydroxide.5. Carbon removal (in terms of total and soluble COD removal) increased with adecrease of SRT for all three digesters. WAS pretreatment enhanced carbon removalefficiency, since soluble carbon was readily available for utilization. The best total andsoluble carbon removal was observed in the exp NaOH unit. Improved carbonremoval in the experimental units was also reflected in a higher content of methane(in the off gas) in these two units. The methane content was stable during all four runs114and was not a function of SRT.6. Solubilization of WAS improved unit gas production (defined as volume of gasproduced per mass of VSS reduced in the digester). Both experimental units had betterunit gas production than the control unit. The exp Ca(OH) 2 and control units reachedtheir maximum unit gas production at an SRT of 15 days, whereas unit gas productionin the exp NaOH unit continued to increase at SRT = 10 days. It is not known,however,if maximum unit gas production was reached during the 10 day SRT run forthe exp NaOH unit, as SRT was not decreased further.7. The addition of calcium hydroxide or sodium hydroxide did not have any beneficialor detrimental effect on effluent quality in terms of nitrogen species. However, theaddition of calcium hydroxide had beneficial effects on effluent soluble phosphorusconcentrations. The effluent from the exp Ca(OH) 2 reactor had lower solublephosphorus concentrations than the effluent from the other two units. This wasattributed to the precipitation of phosphorus with calcium hydroxide. However, thelevel of total phosphorus was the same for all three reactors. The addition of sodiumhydroxide did not have any appreciable effect on effluent quality in terms ofphosphorus species.8. The addition of calcium hydroxide improved waste sludge dewaterability (measuredas CST values) from the exp Ca(OH) 2 unit, whereas sodium hydroxide addition had115a reverse effect - it decreased the dewaterability of the waste sludge, compared to thecontrol unit.9. Overall, except for sludge dewaterability and the beneficial effect on effluent solublephosphorus concentrations (that were better for the exp Ca(OH) 2 unit), the exp NaOHunit outperformed both the control and exp Ca(OH) 2 units. However, WASpretreatment in general allowed a decrease of digester SRT from 25 days to 10 days,without major effects on effluent quality in terms of TOC, VFA, nitrogen andphosphorus concentrations (except as noted above). It also enhanced volatile massreduction, total and soluble COD removal, unit gas production and gas quality. Thesepilot-scale results show great promise for potential to scale-up and implement a full-size demonstration study, including a complete cost-benefit analysis. Systemoptimization is also warranted.1166.2. RECOMMENDATIONSBased on this research a number of recommendations can be proposed:1. Further research in this area should try to optimize chemical dosages for WASsolubilization. Since differences between the control and exp Ca(OH) 2 units were notsignificant in most cases, further research should focus on WAS pretreatment withsodium hydroxide.2. Besides chemical dosage, mechanical mixing time should be optimized. Furtherresearch sohould try to decrease both chemical dosage and anoxic mixing time inorder to decrease operating costs of this treatment process.3. The possibility of combining the beneficial effects of adding of both chemicalstogether to WAS should be investigated.4. It would be of scientific interest and importance to study further the cause of the pHdrop in the anaerobic digesters when the SRT was decreased.5. It would be important to investigate the level of destruction of pathogenicmicroorganisms during this process. Some pathogen destruction, during WASsolubilization, is expected [Anderson and Ley, 1992], as pH is elevated up to 9.0 to11710.0; however, the fate of pathogens during anaerobic digestion, after WASpretreatment, should be examined. It would be also interesting to determine thedifferences in pathogen destruction between digesters containing only WAS chemicallypretreated and digesters where the mixture of WAS and primary sludge is pretreated.6. A study on temperature reduction, i.e. less than 35°C, is also warranted. 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Elsevier Biomedical Press, New York, N.Y., 1982, pp. 23APPENDIX A: Phase I - WAS SolubilizationAl : Total Solids (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 9590 9590 9590 9533 9533 9533 9076 9076 90763 9250 9875 9636 9990 9180 9313 10166 92265 9400 10063 9963 9523 10330 10020 9906 10623 96207 9483 9863 9892 9700 10383 10060 9643 10760 105569 9475 9931 9867 9543 10310 10243 10090 10806 10590A2: Suspended Solids (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0^9284^9284^92843^9220^9124^90925^9152^9816^86607 9024^9665^86089^9296^9488^88088884^8884^88848844^9752^86608988^9672^82289496^9584^81849392^10296^78289076^9076^90768632^9608^84249252^9860^83769412^10064^76529316^10220^7652APPENDIX A: Phase I - WAS SolubilizationA3: Volatile Suspended Solids (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 8036 8036 8036 7704 7704 7704 7936 7936 79363 7988 7604 7812 7668 7884 7472 7524 7788 72765 7944 8112 7408 7780 7772 6972 8024 7820 60467 7816 8228 7324 8224 7708 6884 8172 7936 60079 8064 7848 7492 8184 8284 6568 8084 8048 5977A4: Total Volatile Solids (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 8200 8200 8200 7890 7890 7890 8176 8176 81763 8151 7987 7970 7820 7961 7624 7809 8140 76225 8100 8207 7993 7966 8200 7840 8340 7853 76677 7930 8396 7879 8390 8220 7866 8339 7463 75379 8220 8010 7883 8350 8453 8050 8526 7466 7230APPENDIX A: Phase I - WAS SolubilizationA5: Total Organic Carbon (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 94 94 94 107 107 107 57 57 573 131 130 172 118 136 157 94 151 1365 130 107 419 120 234 595 110 246 5027 134 115 487 113 196 755 115 304 10509 144 160 524 119 269 898 125 352A6: pHch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 6.73 6.73 6.73 6.57 6.57 6.57 6.59 6.59 6.593 6.56 8.16 8.28 6.67 9.19 8.06 6.64 9.52 7.665 6.56 8.21 9.27 6.70 9.19 10.04 6.79 9.68 9.987 6.57 7.97 9.14 6.55 8.91 9.82 6.63 9.56 10.569 6.57 7.89 8.93 6.56 8.72 9.62 6.66 9.40 10.24APPENDIX A: Phase I - WAS SolubilizationA7: Soluble CODs (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH035794134464373724214133974705025674134791198134415383693854174463643695776896778593694971586223124793625524104103693623948519301106362473A8: Total CODt (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 12726 12726 12726 12425 12425 12425 11820 11820 118203 12892 12561 12231 12184 12585 12425 11977 12214 116625 12550 13198 12665 12665 12892 12371 12135 114267 12793 12388 13198 13305 13140 12809 12450 12745 130669 13036 12469 12632 12561 12561 12809 13467 12906 13226average 12799 12668 12697 12628 12675 12672 12417 12364 12240st.dev. 163 288 344 375 245 204 575 402 752APPENDIX A: Phase I - WAS SolubilizationA9: NH4-N (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 34.0 34.0 34.0 34.3 34.3 34.3 37.4 37.4 37.43 33.5 34.4 36.3 34.4 34.3 35.0 37.0 35.1 37.35 32.9 35.9 35.8 35.4 34.1 34.8 36.7 36.8 37.47 35.4 38.8 36.7 35.6 38.2 31.4 37.6 36.89 35.4 39.3 38.4 35.7 41.2 31.5 38.3 37.7 37.1A10: PO4-P (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 74.6 74.6 74.6 72.3 72.3 72.3 72.1 72.1 72.13 77.6 27.2 71.8 75.6 8.8 69.9 64.8 8.9 71.35 76.3 22.8 83.2 75.3 8.2 81.2 71.9 6.9 78.67 74.7 23.3 84.3 73.5 7.7 92.2 73.7 6.9 91.99 75.5 23.4 86.8 73.6 8.5 94.9 72.2 7.4 109.8APPENDIX A: Phase I - WAS SolubilizationAl 1: Soluble TP (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 74.5 74.5 74.5 77.9 77.9 77.9 74.5 74.5 74.53 77.2 31.3 76.9 78.3 14.2 74.0 12.8 73.15 79.0 27.6 95.2 80.7 13.8 98.7 78.9 16.3 75.37 78.7 26.2 95.9 80.2 14.5 106.7 71.9 17.9 107.09 75.2 26.2 95.9 78.3 14.7 108.5 68.9 13.8 119.6Al2: Total TP (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 213.3 213.3 213.3 210.5 210.5 210.5 292.7 292.7 292.73 193.3 216.7 207.0 212.5 217.5 206.2 229.6 221.9 233.45 236.3 236.3 220.8 207.5 193.3 218.3 538.1 258.3 216.87 238.0 224.2 227.7 208.4 218.3 237.9 211.1 251.99 234.6 239.8 217.4 221.7 216.7 190.8 241.1 234.0 234.0average 223.1 226.1 217.2 213.1 209.3 208.8 307.9 243.6 245.8st.dev 17.4 226.1 7.0 5.3 8.7 10.1 117.2 29.1 26.0APPENDIX A: Phase I - WAS SolubilizationA13: Soluble TKN (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 50.6 50.6 50.6 48.8 48.8 48.8 63.8 63.8 63.83 48.5 50.6 64.7 48.7 60.0 58.7 67.6 40.9 41.25 58.7 61.0 128.3 46.5 48.0 66.8 36.5 65.9 95.97 56.7 64.5 145.6 52.2 75.4 218.5 37.1 72.4 202.19 58.7 68.3 152.7 58.7 230.7 227.6 38.0 84.3 252.4A14: Total TKN (mg/L)ch.dose 10 meq/L 15 meq/L 20 meq/Ltime (hr) WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH0 663.7 663.7 663.7 661.2 661.2 661.23 651.1 652.3 662.7 648.5 681.4 654.9 530.9 558.3 547.65 786.7 813.3 740.0 663.7 652.3 705.4 538.1 544.0 532.17 760.0 690.0 713.3 639.7 692.8 616.7 519.0 555.99 720.0 736.7 693.3 721.9 680.1 625.8 590.5 598.8 570.2average 716.3 711.2 694.6 673.8 662.9 668.0 569.1 555.0 551.5st.dev 52.7 58.7 29.6 28.3 16.1 28.3 35.9 28.9 13.8APPENDIX B: Phase II - WAS SolubilizationB1: Total Solids and Total Volatile Solids (mg/L)TS TVSrun # days WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH1 8166 9013 8701 6244 6383 60594 8493 9254 9090 6403 6617 64778 9308 9597 9420 6964 6727 662311 8608 8910 8617 6451 6241 602715 8670 8933 9020 6584 6383 619318 8617 9252 9052 6444 6374 63031 22 9171 9348 9268 6994 6748 668125 10212 10377 10500 7812 7526 730829 10327 10620 10631 7924 7800 742032 9650 11733 10530 7735 9120 735036 8375 8726 8733 6684 6536 607839 10887 11287 10743 8381 8439 796743 10250 10925 10556 8177 8265 736846 12345 12550 12613 9778 9229 953950 9308 9820 9640 7323 7305 6713average 9492 10023 9808 7327 7313 6940st.dev. 1104 1131 1063 944 997 90553 8925 9220 10270 7091 6435 674357 11687 12453 11955 9500 8690 832060 12675 12703 12915 10316 9700 9014Bl: Total Solids and Total Volatile Solids (mg/L) (cont'd)26467717478818588123071317910100978710079985483061343012750133601032010060102809997862213568126131381910216102291035010170875113650965410792812779028144787465841070288999298796570257897758660001041788039645778178237224708064689987averagest.dev.10939169511212169111358161487901397817413138081112139294969910110310610811011311712010220107709754949512366100271145010162102901034189129579107161102010030960012516105551150510367104941051492109708105271105510074982012513104871170310451105501062592259900803384867718744697777460916581007843814770417473814776936981720085427340883978557335794169077089737077697289706387346830845773687236750766487026averagest.dev.102818801052085310791836805774476565987441592B1: Total Solids and Total Volatile Solids (mg/L) (cont'd)41221251271291321361391431461481501531558156749193587379823773168675675865339775860790588745835779009640754184897660883269076933999589869355905086427837969077618600770489837165671010095896093879050643759407447587862965816690852985105769967967093687662395515714356175955547066575027500075306659677265646037562671075777608656236731494048107269641467646263averagest.dev.816196384349558470966643076661657726111729APPENDIX B: Phase II - WAS SolubilizationB2: Total Suspended Solids and Total Volatile Suspended Solids (mg/L)SS VSSrun # days WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH1 7840 8176 6880 6116 6012 53324 8068 9044 7748 6280 6616 59888 8936 7864 7236 6832 5488 549211 8092 7684 6280 6216 5304 470815 8324 8020 6248 6436 5748 468818 8100 7944 6576 6276 5848 50401 22 8988 8320 6732 7020 5904 510025 9804 9340 7536 7680 6828 575629 10388 9956 8224 8244 7508 641232 9264 10696 9256 7572 8464 761636 8040 7744 5992 6508 5784 480039 10452 10520 8300 8408 8044 657643 9840 10328 7180 7996 7900 574846 11852 9692 10616 9432 7184 851650 8936 9232 6656 7224 6976 5364average 9128 8971 7431 7216 6641 5809st.dev. 1113 1043 1211 952 976 105553 8568 7996 6788 6948 6012 552057 11220 11456 7692 9216 9096 637660 12168 12060 8840 10040 9344 7328B2: Total Suspended Solids and Total Volatile Suspended Solids (mg/L) (cont'd)264677174788185881169212652969610316967694608140129001033496808804862094289108772412076952010968748074166592649262281065296961054479888500791276886576104488216769668686732736870685836952879369224623662045516536451328756averagest.dev.105901560975314738061160786871324761512306690135339294969910110310610811011311712098121034093649116118759976109929756988099288556919693809920929286401114096921024088128920988478848932739275886740630491247392798468367004714860486768788084247624733696768108898878647984802868407576724077847252662087927540810067366864767659146964604462205516514075246060660055325656579248965508averagest.dev.989984393958177194777802771472907255874668B2: Total Suspended Solids and Total Volatile Suspended Solids (mg/L) (cont'd)4122125127129132136139143146148150153155782871928984708479087024832864886272938683248696839677206316877667647676646876845880588891968028840475645964499666004912567652166204448043367052598863605668648458807420582864845816684452284988767667567100676859164756680451365844486458804276429271286136646456484900412453884028468843125180365634645744482451364536averagest.dev.7839927741310325650792640678156268764614652APPENDIX B: Phase II - WAS SolubilizationB3: Soluble CODs; Total CODt; Total Organic Carbon (mg/L)CODs CODt TOCrun # days WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH1 0 412 991 8076 8492 8964 10 133 2844 34 366 955 8644 10487 10897 14 119 2378 25 858 1682 9424 8894 9672 12 241 49211 33 1536 2012 8220 8757 8572 12 330 50315 28 421 1391 5378 5448 5330 16 280 55618 20 1357 2478 9122 10228 12222 11 380 46722 30 1532 2690 9570 10255 11403 12 370 6701 25 55 1019 1957 11418 11605 13091 7 256 65629 51 848 1911 11661 11872 12417 11 236 42632 60 1187 1916 11736 14410 14946 6 355 55236 53 1286 2474 9776 10314 8360 358 69839 63 718 2524 13720 14044 13080 12 217 74443 68 1076 2447 12456 13373 11969 11 300 61646 64 1016 2314 14527 12751 15892 14 288 64450 49 1082 2278 11442 11374 11134 8 327 581average 42 981 2001 10345 10820 10816 11 279 542st.dev. 19 368 528 2307 2293 2672 3 78 14053 60 1093 2588 10784 10973 11718 15 292 48557 50 986 2992 13858 13848 14172 25 196 6092 60 87 1361 3164 15518 17546 18133 17 340 86664 65 1019 3896 12202 13263 15631 12 280 104067 101 708 2944 16799 12614 14595 7 179 776B3: Soluble CODs; Total CODt; Total Organic Carbon (mg/L) (cont'd)27174788185885563624074721192101611581061103857430602873260623672494266611476124741107610844106241600810850115601150810137963115220127991273811312105291051815521101010101922295199299275241104528550525629540478average 66 1019 2877 12878 12468 13424 14 245 639st.dev. 16 207 402 2185 2446 2305 6 66 17292 75 536 2581 11800 11594 11912 18 135 66494 88 488 2701 12250 12621 12175 23 128 60696 92 638 2894 11148 11356 11715 18 175 73699 79 992 3110 10648 10968 10855 11 298 723101 103 686 2865 14512 13995 15248 22 189 851103 105 659 3024 12754 12698 13057 21 178 8723 106 89 832 3358 12978 13014 12978 21 232 802108 103 1162 3218 11741 11777 11636 23 348 895110 102 798 3008 11297 11279 11368 21 191 820113 91 770 2994 12190 12358 12209 21 198 832117 92 1472 3107 10932 10689 11360 20 462 918120 123 763 2865 11242 11538 11520 27 193 688average 95 816 2977 11958 11991 12169 21 227 784st.dev. 12 265 205 1032 920 1115 4 93 95122 130 759 2435 9882 9639 9751 28 187 532125 69 1194 2498 8402 8388 8832 29 295 6344 127 100 747 2872 10982 10819 11417 21 170 743B3: Soluble CODs; Total CODt; Total Organic Carbon (mg/L) (cont'd)41291321361391431461481501531557795628856587876827210779059841025120912436988988371368265626992419297526052690287830163043320185339338904810958753582311193310730109441012384049536897196827590829211654106921096210237869995959586114548370804512230109371109210883182020162220202327252215256259328383196243229423641655564729788737861931929788averagest.dev.801999620427682768974112859605118410069129622426472733122APPENDIX B: Phase II - WAS SolubilizationB4: NH4-N; Soluble TKN; Total TKN (mg/L)NH4-N TKNs TKNtrun # days WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH1 0.5 12.3 10.9 10.6 110.1 76.0 454.9 478.9 493.64 1.9 20.2 39.3 2.6 26.8 79.8 493.3 532.2 513.68 3.8 13.8 15.9 4.0 80.2 160.8 491.8 483.6 533.211 1.8 6.1 4.8 2.5 118.9 201.8 475.4 500.2 489.815 3.6 20.7 9.4 6.4 82.4 203.5 490.9 477.3 509.418 2.4 20.6 20.5 3.6 94.6 181.2 518.1 509.4 584.422 1.4 9.2 9.0 3.1 142.3 260.9 537.9 575.2 655.41 25 4.6 13.9 14.5 7.8 89.3 187.3 687.2 633.9 667.929 4.7 26.3 40.4 8.3 74.8 146.2 657.7 613.6 655.332 8.5 22.0 39.4 12.2 95.7 165.3 585.7 627.6 587.836 5.4 10.0 8.8 7.9 121.9 208.8 513.9 526.4 530.539 8.4 15.8 17.6 12.8 83.6 255.1 734.2 727.8 697.143 7.9 15.8 15.7 8.3 100.4 226.7 635.9 699.0 627.146 4.2 12.7 24.1 4.7 94.6 221.6 748.0 739.6 824.350 2.0 8.9 20.3 5.3 101.4 208.2 605.6 627.0 569.3average 4.1 15.2 19.4 6.7 94.5 185.5 575.4 583.4 595.9st.dev. 2.5 5.5 11.3 3.3 25.1 52.2 94.1 88.1 89.753 1.0 16.8 18.1 2.9 103.3 232.2 536.3 530.8 564.557 1.3 17.6 12.1 4.1 99.4 263.0 771.5 809.9 718.560 2.8 16.7 18.4 6.2 125.0 288.5 860.7 845.7 812.8B4: NH4-N; Soluble TKN; Total TKN (mg/L) (cont'd)264677174788185883.79.61.42.81.01.31.52.018.718.214.512.615.213.29.212.824.426.212.419.29.910.19.420.37.314.53.45.42.52.83.44.8106.682.7114.6110.7124.5105.1101.666.3329.4283.8263.1290.4241.5220.5233.9266.2800.6856.9629.9654.1599.5598.7580.2887.1751.7705.0615.5634.3681.2559.2518.2836.2831.6930.2678.4666.5622.7573.8588.9927.1averagest.dev.2.62.415.02.816.45.75.23.3103.616.3264.830.6706.9123.8680.7114.3719.5129.73929496991011031061081101131171202.24.75.04.16.33.75.79.55.84.41.410.714.618.617.521.313.819.521.817.213.814.613.018.921.817.526.317.924.823.120.317.611.05.06.97.36.08.78.29.114.410.57.34.511.558.256.173.7103.682.874.898.8124.183.075.8140.571.2255.1300.2276.7275.2321.5285.4318.5284.6256.2254.7264.7242.5669.0626.4647.0599.0762.6692.1721.4665.0608.4687.2582.5637.3684.8633.3638.1591.9785.1693.0722.8649.8600.9667.0561.8630.3629.3648.0665.7573.5805.2693.0737.7630.3630.3697.3600.9610.7averagest.dev.4.82.116.73.319.34.48.32.786.924.4277.924.3658.250.3654.958.4660.261.8B4: NH4-N; Soluble TKN; Total TKN (mg/L) (cont'd)122 11.0 19.3 20.5 18.0 77.9 223.4 539.9 497.5 487.7125 2.8 12.1 10.1 5.7 113.3 223.4 454.6 460.3 460.3127 5.9 15.8 18.7 9.4 72.0 242.3 601.8 558.5 548.7129 4.2 12.7 11.4 6.6 98.2 221.6 489.6 427.6 474.1132 3.1 10.5 11.0 4.7 76.0 202.2 545.0 526.8 508.7136 4.6 10.0 11.5 5.8 83.9 228.2 404.1 376.0 424.2139 2.0 11.9 13.8 4.6 92.2 291.7 533.9 522.2 509.14 143 3.8 9.8 8.7 5.3 112.8 240.1 448.3 409.2 393.5146 3.6 9.7 9.4 4.6 113.9 221.5 420.9 417.0 393.5148 3.9 12.1 19.8 7.3 64.3 279.3 628.6 597.2 597.2150 2.4 9.8 17.9 4.6 71.1 266.4 566.4 538.3 562.4153 4.2 12.7 20.7 6.9 76.0 258.5 566.4 550.3 606.5155 3.0 12.8 13.1 4.9 120.4 274.3 542.3 542.3 542.3average 4.2 12.2 14.4 6.8 90.2 244.1 518.6 494.1 500.6st.dev. 2.2 2.6 4.3 3.5 18.7 26.3 66.8 66.1 67.8APPENDIX B: Phase II - WAS SolubilizationB5: PO4-P; Soluble TP; Total TP (mg/L)PO4-P TPs TPtrun # days WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH WAS Ca(OH)2 NaOH1 2.2 47.1 92.1 2.0 47.0 96.7 196.5 190.3 190.34 14.0 22.6 94.4 14.9 23.2 96.7 205.6 210.8 203.48 12.1 14.5 99.5 12.3 18.8 134.2 211.4 205.8 230.211 9.7 13.4 67.7 10.6 24.8 137.6 195.0 208.2 208.215 27.6 25.7 85.8 28.5 29.9 141.9 203.7 199.5 234.518 14.3 26.0 76.8 14.2 32.4 123.1 213.7 189.4 207.01 22 6.1 14.6 86.8 6.5 25.2 167.5 215.7 239.6 227.025 33.9 40.5 109.4 35.2 46.1 151.3 272.8 259.3 265.129 37.5 44.3 127.4 39.5 47.5 130.6 263.2 236.8 254.532 18.1 29.1 84.3 18.6 35.3 105.7 205.6 206.5 199.336 9.9 11.5 61.2 9.9 21.5 123.4 184.3 200.5 158.239 34.2 42.8 118.6 35.0 49.5 168.7 295.7 287.6 279.143 19.3 30.4 95.1 19.8 37.9 141.5 241.2 264.7 232.946 19.0 48.7 180.9 18.9 57.5 189.1 333.0 287.7 352.750 18.2 37.3 104.8 18.0 50.2 157.3 261.4 273.0 243.7average 18.4 29.9 99.0 18.9 36.5 137.7 233.3 230.6 232.4st.dev. 10.3 12.5 27.8 10.7 12.0 25.8 41.6 34.3 43.853 14.6 23.2 97.9 14.1 38.5 194.0 263.4 251.0 260.857 15.0 70.6 127.6 15.9 74.2 213.6 333.8 358.6 302.460 31.5 63.5 165.7 31.6 72.5 224.0 372.6 362.5 347.8B5: PO4-P;2Soluble TP;6467717478818588Total TP (mg/L) (cont'd)^28.8^64.642.1^63.111.0^53.924.1^54.16.2^64.77.6^69.018.1^47.622.2^93.0195.1206.3133.0135.4131.6134.7124.9223.429.443.811.625.26.79.418.022.772.565.665.666.875.875.959.9102.2253.5253.8214.2221.0213.3196.1212.4265.0356.8384.4286.1311.0297.5305.6297.2464.3323.2386.9281.5292.0328.5290.5267.1431.2367.5406.8293.8309.2299.6288.1297.0456.1averagest.dev.20.110.560.716.3152.337.820.810.670.014.4223.722.5333.954.6324.852.8329.956.139294969910110310610811011311712023.146.742.025.641.339.830.628.741.839.512.985.795.786.967.8100.189.389.969.582.384.553.9140.5190.5162.8131.8203.4169.3182.2160.2167.4162.3127.424.250.643.226.243.638.532.629.340.639.014.862.893.2103.996.978.9117.3102.1100.279.085.091.154.079.0249.7254.9248.9233.1268.4252.5274.2218.9214.0223.4228.6196.6354.9357.5345.6341.6411.3367.7384.7323.4311.6335.5288.3284.3356.6343.7341.9321.9393.4359.9370.0315.7303.3334.3280.9300.6341.7351.2354.4321.9408.6365.0375.0315.7300.8342.0295.8290.9averagest.dev.33.89.982.312.9163.422.537.112.390.115.6238.622.3342.235.6335.231.0338.633.8B5: PO4-P; Soluble TP; Total TP (mg/L) (cont'd)122 72.9 56.0 161.0 73.0 60.4 181.0 264.5 251.7 251.7125 32.2 38.5 99.2 29.7 47.3 170.4 227.5 221.4 226.2127 55.1 60.4 152.9 51.6 63.5 189.5 288.2 279.5 279.5129 34.0 40.9 103.3 33.6 49.3 165.8 232.9 211.1 228.9132 38.5 46.1 128.1 42.3 52.3 164.8 264.5 256.6 248.7136 43.8 37.6 125.1 43.4 44.4 179.6 228.9 217.1 240.8139 32.5 53.6 165.4 33.5 61.8 229.9 283.3 270.4 287.44 143 29.5 29.8 94.9 31.3 37.7 165.7 211.1 199.3 191.4146 27.7 26.1 87.9 28.6 34.7 157.7 195.3 199.3 193.3148 57.0 66.1 173.9 59.4 66.8 216.9 290.3 278.4 284.4150 32.9 49.3 139.2 31.5 57.9 184.9 262.4 242.4 250.4153 43.8 51.5 161.6 47.4 62.4 190.0 264.4 252.4 270.4155 29.0 41.5 204.2 26.8 51.8 195.1 242.4 242.4 246.4average 40.7 46.0 138.2 40.9 53.1 183.9 250.4 240.2 246.1st.dev. 13.0 11.2 34.1 13.3 9.8 20.2 28.8 27.1 29.7APPENDIX C: Phase II - Digester Performance: Soldis, Gas Production and Methane ContentC1: Solids: Total Solids (mg/L)day12345678910111213141516171819202122influentcont^expCa(OH)2 expNaOH10148 100837740^775710918^109738681^903910220^103268079^7474^80815907^6158^61608764^9128^857010230^9719^98908063^7823^76467136^7291^698310562^10261^1045111129^10900^1072012570^10560^1114611259^10344^983615634^15557^154737654^7620^72907377^7312^72007252^7328^70517367^7552^74007216^7340^70507282^7247^70737027^6853^66506953^6833^67467159^7143^70467079^6823^66977423^7533^7457run #1(SRT=25)cont 9797^81137563^784910583^79288560^78519954^7587effluent expCa(OH)2 expNaOH8022^78267639^72327928^76717557^75457697^7461C1: Solids: Total Solids (mg/L) (cont'd)1(SRT=25)23242526272829303132333435363738394041424344454647489616^10476^1043911600^11610^1115212370^11693^108239990^9650^977711992^11275^1082715434^14984^1405316595^15103^1541713659^13381^1336013883^13003^1198010396^9800^933211646^11433^1142016329^14240^1456913679^13477^1256412940^13623^1288012937^12607^1185712349^11697^1193310250^9873^987413168^11446^1199317383^16082^147817680^7593^76487406^7308^72877303^7540^73577259^7237^72777240^7290^71267394^7325^72397445^7400^71287242^7753^72237516^7393^73517407^7567^72957945^7715^78797738^7609^72847928^7763^74127815^7547^74398106^7929^77087927^7635^75357980^7670^76688200^7647^75338207^8004^8073 C1: Solids: Total Solids (mg/L) (cont'd)4950 12352^1129211540^11144^108822689^2383^226912187 8078^8148^79427581^7514^7356357 310 3238349^8072^79767958^7900^78298241^8180^80527895^7873^77822(SRT20)51525354555657585960616263646566676869707111782^12081^1130310867^11584^986413570^13260^1318013058^13207^1178312231^11620^1138013517^13230^1381911264^11691^1032312110^12568^1096212323^9760^1104310806^10419^1045214337^14106^126728132^7849^77507959^7843^76568115^7473^75809650 79948115^7816^76468158^7879^76848215^8027^77687895^7850^75858034^8463^78578187^7723^7517averagest.dev.7939^7861^782413700^12707^1317715433^13806^1352014104^13670^1335615723^15544^126468176110951455216054150137553^751210417^1043716003^1451016310^1567613386^12626C1: Solids: Total Solids (mg/L) (cont'd)2(SRT=20)7273747576777879808182838485868788899012259^13352^1254912996^13185^1184511871^10394^1088513723^12872^1220712255^13886^1175312503^12100^1186011226^11203^113549288^9712^90008767^9094^90647813^7787^76517767^7770^74838184^7848^74728145^7948^85478045^8081^78758077^7923^78327987^8007^73567800^8129^72287888^7693^71577473^7630^71497664^7545^69947630^6945^75457734^7684^71907548^7665^6990averagest.dev.12724^12456^118382026^2016^17118034^7847^7641360 261 337919293943(SRT=15)12449142601038314094^1293914644^1382810420^102208238^8251^75228543^8280^76288445^8316^7633C1: Solids: Total Solids (mg/L) (cont'd) 3(SRT=15)959697989910010110210310410510610710810911011111211311411511611711811912011634^13145^1279616152^12160^1802611400^11320^1085312893^12884^1285315907^12692^1191012623^12456^1162012447^11429^1086713741^13300^1331310743^10853^1033310120^11110^98899750^9715^937310367^10877^1014310090^10100^987111066^10952^1060012353^11767^1113311307^12161^1236411468^9858^939711816^12253^1231310961^11153^104258162^8400^77468355^8577^78178481^8546^81938290^8432^79288575^8237^78198467^8800^79939440^8175^77908056^7940^75878383^8332^75938277^8176^74938084^8222^75908287^8287^75908007^8190^73298152^8096^74938037^7839^69947923^7890^73037480^7670^72147714^7910^70357843^8123^7356734771937163736071397296733073977128698068067100730471137240728477677680780776507858807771867252731583877388701672697386751974237240716173277117705371217229776475277717768672577548717470436945691070076950707771407259724777406847693369706839697367207352661271567257722772496900C1: Solids: Total Solids (mg/L) (cont'd)averagest.dev.11997^11788^115941715^1295^19108238^8213^7575376 256 2891211221231241251261271281291301311321331341351361371381391401411421431092495267600101948262114971160012481823580251092310626104871143111090802598229790122778968925710020711711567917479421073782401162711990121938803855011562105171009095591063985679970965311732903999109437718411527919375841052784201193812007114038720917511332100531070310219108477797977692671188382139881926270554(SRT= 10)C1: Solids: Total Solids (mg/L) (cont'd)4(SRT=10)144^12507^12959^12400^7623^7448^7063145^8110^8136^8147^7557^7420^7143146^9712^9162^9584^7139^7200^7061147^8783^9387^9103^7272^7031^6884148^8446^8464^8213^6917^7039^6633149^9875^10327^10000^7506^7160^6924150^9671^9445^9173^7017^7253^7177151^9303^9824^9345^7003^7520^6821152^8770^8624^8280^6933^6950^6833153^11846^11739^12279^7039^6917^6697154^9482^9666^8957^7085^7140^6920155^13397^13142^13716^7493^7420^7132average^9945^9987^9885^17308^7325^7018st.dev.^1538^1460^1560^294 278^221 APPENDIX C: Phase II - Digester Performance: Solids, Gas Production and Methane ContentC2: Solids: Total Volatile Solids (mg/L)influent effluentrun # days cont^expCa(OH)2 expNaOH expCa(OH)2 expNaOH4415^44524136^40134449^42684153^42624339^41904341^41574154^41694197^40304390^43294220^4110cont 6958^45035170^43217997^42396387^42957469^42567493^71975300^53207790^83396681^66727827^78101234567891011121314151617181920211(SRT=25)6184^54714553^44586952^69617806^74876197^59415358^53718361^79768872^86229452^82038577^79844270^41783909^37533964^39184222^42473880^37325903^43654443^42436493^41977690^43205793^42495127^43318159^40958432^41238790^43327449^4085C2: Solids: Total Volatile Solids (mg/L) (cont'd)1(SRT=25)222324252627282930313233343536373839404142434445464712624^13043^128927527^8260^82009298^9240^87949446^8603^85208107^7527^76009271^8852^842013090^12460^1151313552^12413^1275011780^11100^1114711330^10730^98038272^7903^75039862^9465^921313000^11580^1198811100^10974^1010910043^10260^997710225^10370^98109780^9477^96708180^7879^794211102^9285^966214303^13384^122194662^4720^46704950^4843^49684657^4607^45674612^4749^46534554^4481^45004630^4597^44614726^4620^44724771^4647^43844800^5000^46695160^4710^47414960^5069^47645429^5193^52105094^4994^47945225^5146^48125040^4816^46985377^5206^50135223^4959^48855397^5070^50545651^5023^49805639^5379^5708 C2: Solids: Total Volatile Solids (mg/L) (cont'd)2(SRT=20)484950averagest.dev.515253545556575859606162636465666768697010319^10103^92519156^8798^85902389^2207^211211253^10463^1079012524^11664^1132311454^11693^1147413448^12922^103578587^9680^94139000^9594^803411194^10450^1113811057^10917^97369665^9337^937011690^11137^116199713^9709^85489630^10355^895210403^7880^88639210^8580^85665471^5452^53124722^4620^4531474^421 4395814^5475^54245436^5291^56285736^5542^55035512^5363^52895746^5323^52205654^5090^52145791^5897^517056875688^5072^51645800^5600^52905854^5660^54135587^5487^52385714^5963^54735918^5437^5217C2: Solids: Total Volatile Solids (mg/L) (cont'd)2(SRT=20)717273747576777879808182838485868788899011844^11984^1060010623^11268^1055610687^10318^98909542^8394^893910713^10161^1009010629^11818^982010731^10062^98309597^9236^94157755^7814^72277050^7019^69365676^5510^54795629^5440^53735590^5360^52665797^5329^51795710^5379^63375668^5539^55325734^5445^56815647^5521^51925495^5564^50415619^5500^50136741^5897^5832^5283^5240^50039097^8483^8477^5470^5152^488212421^13315^12090^5400^5165^482312797^13813^13152^5544^5280^503713097^11210^10464^5429^5344^4862averagest.dev.10419^8329^97071670^1812^15635641^5427^5298149^204^3039192933(SRT=15)10135^11481^1076812130^12103^114075884^5667^53256131^5713^5420C2: Solids: Total Volatile Solids (mg/L) (cont'd)8583^8393^81509545^10590^994114410^10063^158649641^9276^887011063^10732^989713943^9320^94639561^10314^951210343^9388^886711003^11170^110779227^8973^84988103^8593^80898097^8295^75308050^8348^78635987^5684^53405721^5716^53735855^5806^53495833^5621^54535507^5410^49176050^5600^54625851^5750^54986794^5302^53225597^5457^49735830^5525^51025710^5567^51905461^5422^51805567^5337^51079495969798991001011021031041051061073^108(SRT=15)^1091101111121131141151161171181198429^8137^7897^5443^5410^48748761^8962^8643^5565^5292^500010290^9427^8870^5537^5232^46909730^10235^10455^5503^5293^49759885^7964^7529^5213^5096^487610203^10270^10363^5322^5331^4745C2: Solids: Total Volatile Solids (mg/L) (cont'd)120^8803^8760^8213^5357^5377^49215714^5482^5141335 189^242averagest.dev.9997167395821137944418044(SRT=10)121^9294^9582^9527^5033^4819^4737122^8122^7529^7500^4868^4825^4552123^6096^6233^5938^4743^5817^4497124^8550^8790^8610^5060^4859^4580125^6503^6610^6747^4897^4555^4640126^9836^9652^9941^4904^4624^4657127^9643^9740^9783^4927^4686^4643128^10580^10103^9357^5090^4897^4745129^6917^7186^7140^4884^4872^4833130^6452^6967^7566^4829^4793^5453131^9383^9694^9474^4664^4804^4600132^9176^8789^8317^4856^4920^4607133^8687^8430^8684^5152^4707^4508134^9789^7594^8358^4930^4660^4559135^9045^8739^8893^5073^4727^4647136^6521^7013^6303^4975^4745^4433137^7948^7750^7679^5040^4887^4632138^7972^7481^7193^5023^4737^4630139^10690^9923^9030^5107^4893^4503140^7619^7381^6653^4860^4737^4480141^7553^7852^7990^5168^4497^4480142^8607^7743^7594^5147^4784^4565C2: Solids: Total Volatile Solids (mg/L) (cont'd)4(SRT=10)143^5947^5647^5558^4703^4558^4387144^10569^10676^10203^4983^4676^4420145^6367^6214^6213^4910^4603^4413146^7268^7438^9655^4543^4462^4368147^7290^7735^7540^4938^4506^4371148^6921^6671^6427^4633^4548^4203149^7925^8333^8024^5058^4510^4321150^7768^7372^7130^4552^4512^4532151^7641^7897^7417^4543^4897^4331152^6973^6862^6557^4643^4430^4373153^10135^9743^10258^4767^4473^4241154^7824^7714^7107^4694^4480^4343155^11114^10606^11250^4990^4647^4461 average^8249^8105^8046^4891^4718^4536st.dev.^1428^1304^1392^180^240^212 APPENDIX C: Phase II - Digester Performance: Solids, Gas Production and Methane ContentC3: Solids: Total Suspended Solids (mg/L)influent effluentrun # days cont^expCa(OH)2 expNaOH cont^expCa(OH)2 expNaOH1(SRT=25)1234567891011121314151617181920219712^9248^84206984^640810372^10152^93168400^8468^76289812^9672^92287812^6764^65365620^5448^45848428^8324^72089616^8804^77767660^6956^59766708^6376^522410140^9380^901210684^9988^936012068^9660^897610992^9512^83244892^5096^48284896^4880^46844808^4836^46964976^5072^47065012^4932^47764920^5200^47444772^4796^45484872^4988^45965168^5116^47285008^5100^47285080^5000^52484916^4812^47725096^5072^47965100^4888^49565064^4880^4952C3: Solids: Total Suspended Solids (mg/L) (cont'd)1(SRT=25)22^14696^14748^13688^5624^5724^537623^9232^9644^8716^5732^5748^549224^11136^11136^9512^5408^5556^530825^11752^10524^9052^5544^5776^544026^9596^9120^7812^5496^5656^5252272829^11512^10640^9460^5508^5484^526430^15040^14304^11808^5668^5708^536831^15932^14336^13568^5768^6052^546032^13192^12600^11720^5820^5988^561633^13328^11812^10616^5892^5824^565234^12704^12116^11156^6128^5972^546435^13724^13412^11204^6132^6268^571236^9980^9060^7744^6112^6320^564837^11180^10956^9156^6232^6236^574438^15240^13908^12128^6156^6008^532439^13132^13052^10988^6172^6224^586440^12200^12328^9992^6208^6144^580441^14032^13692^12724^6400^6164^556442^11068^10384^9836^6296^6216^579643^12420^11612^10112^6376^6380^606844^11732^11128^10072^6152^6136^589645^9840^9452^8192^6124^6100^580846^12624^10792^10476^6348^6352^568847^16688^15772^12912^6716^6528^5956 § 660863606648659670886680672471126784646067126824662466166588666065526620644865246672644868726496660865526676650866166772659663406672681266086848599264846464646063526216624064406256620060606140608059966016579262726112621660966580594458525796C3: Solids: Total Suspended Solids (mg/L) (cont'd)484950averagest.dev.14968^14952^1182814648^13220^1133211696^11296^956011496^10756^95082532^2468^21266428^6340^59006420^6476^57366588^6484^61045667^5679^5335594 577^4645152535455565758596061626364656667686970131521481613540154481387610608110761013213028125361092411916120401323210940113841146410688115321409611916132761244014592114369192119481067212200126441090012552115481217211268118928864971210272137121092012160120681043211880824095488084108849844900012820102241190485208804909684049008117962(SRT=20)C3: Solids: Total Suspended Solids (mg/L) (cont'd)2(SRT=20)7172737475767778798081828384858687888990averagest.dev.13764^12728^1112012132^11848^1050012476^11728^944410420^10032^878412500^11420^983613524^13728^112449908^10200^741211616^12308^989612132^11248^992810588^9992^91368892^9064^70088380^8508^70128544^8320^724410024^8100^83287828^6608^589610652^9656^864013908^15356^1195215412^15956^1418013460^12468^1061213576^13104^1042011904^11390^98061856^1972^17666644^6664^60286380^6612^58366596^6432^58926388^6636^61526368^6532^59166716^6652^61086504^6692^60686428^6640^59046772^6556^60366480^6548^59866512^6488^57726216^6564^57006312^6308^56526300^6420^56846132^6268^56246228^6140^54726132^6288^55646388^6700^60566732^6416^57366436^6480^55606547^6538^5985216^178^2496380^6528^59446904^6908^59766848^7008^613691929315424^13548^1166012020^13176^1114013516^13576^113603(SRT=15)C3: Solids: Total Suspended Solids (mg/L) (cont'd)3(SRT=15)94^9956^9804^8308^6596^6996^606095^11036^11708^10044^6648^6892^600896^12188^11112^10184^6540^6792^597297^10432^10288^8632^6500^6708^584898^13724^11912^10252^6448^6764^596899^10820^10408^8896^6716^6784^5868100^12260^12436^10804^6516^6552^6016101^13088^12176^10176^6552^6868^5980102^10984^10912^9472^6708^6716^6028103^11892^10940^9872^6408^6544^5784104^11496^11316^9880^6640^6820^5948105^9408^9136^7492^6456^6616^5996106^13192^12408^10404^6520^6536^5744107^10152^9904^8500^6248^6796^6060108^9172^9508^8172^6232^6604^5684109^9036^6196^7856^6580^6528^5680110^9648^9604^7996^6092^6552^5488111^9716^9836^8224^6036^6356^5564112^9628^9964^8192^6276^6256^5316113^9676^9096^7864^6084^6608^5440114^10624^9792^8752^6180^6368^5424115^8928^8864^7436^6124^6132^5116116^11808^10552^9004^6032^6212^5364117^10908^11684^10164^6140^6412^5272118^9160^8772^7008^6104^6220^5188119^11312^11460^9784^5812^6412^5216 C3: Solids: Total Suspended Solids (mg/L) (cont'd)120^9840^9712^8144^5936^6212^52765055^6590^5712276^243^315averagest.dev.110351597106601582918912444(SRT=10)121^10588^10660^9312^5636^6204^5316122^9052^8936^7592^5452^5656^4912123^6684^6860^5832^5264^5400^4852124^9988^9528^8564^5296^5516^4932125^7932^7398^6568^5132^5292^4784126^11192^10812^9452^5180^5416^4912127^10652^11396^9684^5404^5600^4924128^12096^11064^9300^5520^5612^5136129^7772^8112^6896^5548^5504^5032130^7704^7648^7148^5388^5548^4848131^10556^10192^9108^5520^5552^4840132^9948^9956^7892^5404^5648^4856133^9996^9464^8044^5568^5664^5036134^9512^8944^8356^5644^5648^5124135^10648^9780^8444^5920^5568^5356136^7704^7128^6376^5540^5496^5076137^8616^8988^7712^5486^5568^5264138^8788^8592^6868^5212^5580^4972139^11464^10940^9456^5524^5672^4840140^8364^8164^6476^5240^5808^4844141^8980^8852^7812^5188^5572^4664142^9496^9008^7188^5328^5516^4972C3: Solids: Total Suspended Solids (mg/L) (cont'd)4(SRT= 10)143^6888^6432^5468^5120^5388^4632144^11672^11872^10112^5236^5548^4768145^7292^7360^6024^5272^5368^4744146^9324^8280^7188^5172^5444^4900147^8432^8036^7876^4972^5452^4820148^8044^7784^6340^4944^5276^4516149^9480^9356^8140^5092^5192^4608150^9148^8320^7316^5052^5332^4672151^8640^8844^7512^5024^5304^4572152^8420^7732^6372^4952^5056^4456153^11220^11164^9700^5224^5340^4540154^9284^8784^7032^4848^5352^4704155^12668^12368^10728^5224^5312^4396average^9378^9107^7825^5160^5497^4852st.dev.^1476^1471^1310^234 197 229 APPENDIX C: Phase II - Digester Performance: Solids, Gas Production and Methane ContentC4: Solids: Total Volatile Suspended Solids (mg/L)influent corrected influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1(SRT=25)1234567891011121314151617181920217492^6824^63684972^48008628^7924^75046796^6464^60127972^7480^74606232^4980^50764580^4016^35646912^6464^58288012^6968^63486328^5428^48727492^6891^68775398^54348628^8603^84956796^6653^62017972^8121^84456232^5853^59474580^4267^40356912^7018^65988012^7560^73286328^5893^55163624^3760^35963688^3612^35563548^3564^35243688^3744^34963760^3676^36203680^3620^35603560^3540^34363632^3612^34003892^3732^35443692^3720^34965408^4760^4068^5408^5207^52048500^7492^7520^8500^8134^85139012^8076^7752^9012^8768^877610324^7740^7360^10324^8018^81638544^7564^6784^8544^8212^76803908^3816^41323764^3676^37043860^3832^36603700^3628^37843800^3648^3720C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd) 222324252627282930313233343536373839404142434445464712784^12620^11864^12784^13345^13112^4236^4248^40647684^7708^7244^7684^8369^8201^4296^4292^42009384^9096^7932^9384^9876^8980^4032^4044^40249912^8528^7524^9912^9081^8774^4148^4256^41448064^7308^6472^8064^7934^7327^4104^4136^39281(SRT=25)9632^8560^7800^9632^9038^8990^4080^4076^431013024^12168^10128^13024^13211^11466^4236^4220^412813852^12096^11672^13852^13133^13214^4308^4496^411211568^10768^10204^11568^10188^10175^4428^4440^430411696^10044^9188^11696^10905^10402^4412^4272^426410996^10140^9528^10996^11009^10787^4672^4320^413611928^11380^9760^11928^12355^11049^4652^4628^43528644^7520^6608^8644^7990^7718^4700^4704^43289720^9292^7980^9720^10088^9034^4814^4660^439613056^11748^10392^13056^12755^11765^4720^4444^406811200^10888^9328^11200^11124^10518^4724^4624^449210408^10300^8642^10408^11183^9784^4704^4548^443611960^11464^10856^11960^12446^12290^4876^4568^42129580^8644^8432^9580^9385^9546^4808^4596^440010964^9848^8844^10964^9910^10305^4920^4764^470410088^9364^8612^10088^10166^9750^4720^4616^44848444^7836^6930^8444^8508^7845^4708^4528^446410824^8992^8920^10824^10453^9515^4912^4692^436014444^13456^11184^14444^14609^12661^5112^4860^4628513649365208517654925224530856205352511252805248524852645268535252725324516852764996482851844914496849125020492049645120501247685080519250525252479649444968494049404824486850444876486847844828486247244760456849844844502648565064472047204628C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd)484950averagest.dev.12848^12612^1016011990^10948^960810208^9544^83209747^8810^79872323^2329^199412848^13693^1150211990^11886^1087710208^9705^95299747^9451^90082323^2492^21994952^4688^45244940^4824^44245092^4812^47164288^4203^4067499^436^3885152535455565758596061626364656667686970115081289612116134361200093249760890011312110529590103281066811736970810020994493801012412444101521159210824124329736785810304961410380107569344105489940105169724100947404824888561196094201078810768914810296719284247068946886688036110409474105927588770878407336797610436115081289612116134361200093249760890011312110529590103281066811736970810020994493801012412444109421249411432133991049384691038210362111881120810071113691071311478104811087992558890954512890109031248611696105881191783241027081811095810430930112778109651173687828921869884919231120792(SRT=20)C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd)71 12332 11080 9880 12332 11808 11018 5396 5124 486472 10768 10318 9348 10768 11121 10819 5176 5088 470473 10992 10028 8396 10992 10808 9718 5324 4928 475274 9152 8520 7748 9152 9669 9240 5168 5108 499675 10836 9688 8668 10836 10442 10032 5148 4916 476076 11908 11768 9952 11908 12684 11518 5600 5108 493677 8488 8508 6340 8488 9170 7338 5240 5128 491278 10324 10688 8776 10324 11041 10333 5220 5104 478079 10648 9616 8732 10648 10364 10106 5480 5036 481680 9340 8464 8036 9340 9122 9301 5252 5032 488081 7684 7584 6100 7684 7987 7610 5312 4992 46882 82 6980 6840 5976 6980 7372 6917 5020 5020 4596(SRT=20) 83 7224 6744 6188 7224 7269 7162 5120 4816 457284 8564 6616 7164 8564 7131 8292 5096 4840 460885 6708 5340 5072 6708 5821 6010 5000 4800 455686 9276 8188 7592 9276 8825 8787 5084 4728 445687 12132 13578 10539 12132 14634 12198 5012 4808 450088 13580 13892 12592 13580 14490 13691 5216 5148 495289 12108 10764 9380 12108 11601 10856 5484 4916 458690 11814 11276 9196 11814 12153 10643 5228 5008 4426average 10428 9745 8624 10428 10486 9958 5246 4987 4778st.dev. 1691 1824 1602 1691 1888 1735 150 126 16391 13440 11536 10140 13440 12140 11942 5172 5090 48483 92 10564 11380 9804 10564 11796 10997 5668 5372 4868(SRT=15) 93 11780 11572 9984 11780 12178 11758 5620 5428 5004 •--a\v)C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd)3(SRT=15)94^8552^8204^7096^8552^8620^8528^5364^5404^496495^9536^9940^8732^9536^10461^10284^5428^5308^488096^10740^9480^8952^10740^9721^10322^5292^5232^484497^8826^8568^7408^8826^9017^8724^5292^5196^469698^12064^10196^8968^12064^10730^10562^5236^5188^495299^9420^8840^7756^9420^9305^9183^5164^5560^4732100^10772^10760^9572^10772^11324^11273^5300^5046^4860101^11484^10412^8916^11484^10986^10314^5352^5284^4812102^9460^9268^8350^9460^9754^9834^5440^5176^4888103^10488^10940^7852^10488^11309^9183^5176^5032^4672104^10008^9580^8632^10008^10082^10166^5424^5126^4788105^8108^7724^6532^8108^8129^7693^5264^5104^4840106^11696^10736^9184^11696^11313^10736^5260^5028^4612107^8980^8476^7436^8980^8920^8757^5072^5244^4876108^7996^7956^7132^7996^8689^8647^5064^5048^4600109^7882^5040^6828^7882^5304^8041^5352^4988^4604110^8376^8060^6888^8376^8788^8401^4908^5012^4412111^8352^8248^7068^8352^8680^8324^4896^4828^4378112^8296^8182^7076^8296^8611^8333^5072^4792^4280113^8376^7620^6784^8376^7848^8237^4948^5080^4364114^9308^8344^7628^9308^8781^8983^4880^4848^4332115^7672^7466^6408^7672^7857^7547^4972^4692^4104116^10052^8768^7624^10052^9227^8979^4872^4768^4334117^9612^10092^9028^9612^10692^10291^4996^4928^4260118^7880^7376^6022^7880^7763^7092^4960^4764^4164119^9964^9900^8640^9964^10419^10175^4720^4826^4196^'Z.)"0 C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd)120 8872^8192^7076^8872^8589^8420^4836^4768^4224averagest.dev.9618143690951471798411365167^5072^4613234^222^2789618143695681526939112604(SRT=10)1211221231241251261271281291301311321331341351361371381391401411429376^9048^8168^9376^9674^9602^4584^4956^44008056^7600^6676^8056^7969^7705^4480^4424^40125864^5712^5052^5864^6107^5939^4288^4192^39008696^8004^7444^8696^8558^8751^4356^4252^39806936^6116^5712^6936^6846^6853^4220^4132^39249932^9260^8324^9932^9901^9786^4260^4192^39969328^9784^8516^9328^10184^9836^4448^4360^401610512^9452^8132^10512^10106^9560^4520^4360^41966804^6916^6064^6804^7365^7234^4576^4280^40886840^6512^6316^6840^6963^7425^4350^4316^39329666^8832^8112^9666^9443^9536^4568^4348^39248856^8620^6996^8856^9036^8163^4464^4448^39848828^8044^7136^8828^8601^8389^4556^4412^41368336^7612^7388^8336^8139^8685^4644^4404^41809320^8264^7340^9320^8836^8629^4960^4344^44126760^5980^5592^6760^6598^6569^4592^4268^41447512^7512^6688^7512^8032^7862^4488^4312^40427640^7152^5948^7640^7647^6992^4288^4368^402010276^9564^8528^10276^10190^9609^4584^4372^39807332^6868^5688^7332^7343^6687^4296^4536^39607820^7504^6860^7820^8023^8065^4260^4376^37968360^7696^6308^8360^8229^7416^4360^4310^4064C4: Solids: Total Volatile Suspended Solids (mg/L) (cont'd)4(SRT= 10)143^5968^5236^4692^5968^5854^5713^4224^4192^3796144^10472^10044^8748^10472^10739^10284^4292^4288^3872145^6204^6008^5112^6204^6424^6010^4316^4194^3796146^8248^6964^6296^8248^7416^7286^4208^4180^3940147^7452^6816^7004^7452^7288^8234^4158^4216^3848148^6896^6428^5372^6896^6784^6627^4032^4056^3664149^8136^7840^6980^8136^8383^8206^4116^3996^3660150^7932^6880^6296^7932^7283^7551^4076^4084^3776151^7424^7340^6378^7424^7848^7498^4080^4064^3712152^7256^6388^5464^7256^6830^6423^4044^3982^3548153^9900^9632^8536^9900^10045^9812^4248^4112^3680154^8008^7268^6024^8008^7771^7082^3936^4068^3726155^11088^10580^9388^11088^11308^10838^4228^4016^3416average^8230^7699^6836^8230^8222^8024^4346^4269^3929st.dev.^1349^1336^1189^1349^1377^1329^212^182^211 Corrected influent = VSS' (Equation 5.3)16.6514.8018.1017.5018.0012.4512.4010.159.5511.5014.5012.208.958.957.6014.4017.6015.0015.1020.4020.7514.8512.8018.3015.5016.7013.3013.3010.6011.2013.4516.4014.1010.0510.058.6014.8018.2016.9014.5523.5523.1015.8414.0817.2216.6517.1211.8411.809.669.0810.9413.7911.618.518.517.2313.7016.7414.2714.3619.4119.7414.1312.1817.4114.7515.8912.6512.6510.0810.6512.7915.6013.419.569.568.1814.0817.3116.0813.8422.4021.9816.7414.4120.8815.9818.9312.9912.9911.1812.4115.7916.6514.2710.1310.089.4216.8420.4518.3615.0823.5425.83APPENDIX C: Phase II - Digester Performance: Solids, Gas Production and Methane ContentC5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at T=20 CT=35 C T=20 Crun # days cont^expCa(OH)2 expNaOH cont^expCa(OH)2 expNaOH1(SRT=25)12345678910111213141516171819202117.6015.1521.9516.8019.9013.6513.6511.7513.0516.6017.5015.0010.6510.609.9017.7021.5019.3015.8524.7527.15C5: Gas Production: Volume of Gas Produced per Day (L./day) at T=35 C and Corrected at T=20 C (cont'd)1(SRT=25)22^27.40^30.40^37.70^26.07^28.92^35.8623^17.80^21.60^27.45^16.93^20.55^26.1124^23.65^26.40^28.45^22.50^25.11^27.0625^20.15^21.40^26.00^19.17^20.36^24.7326^14.60^16.45^17.00^13.89^15.65^16.1727^14.65^16.45^17.05^13.94^15.65^16.2228^12.55^15.93^16.60^11.94^15.15^15.7929^17.60^18.70^20.30^16.74^17.79^19.3130^22.40^21.75^25.45^21.31^20.69^24.2131^26.40^25.25^31.25^25.11^24.02^29.7332^26.70^29.05^35.30^25.40^27.64^33.5833^25.20^29.75^31.15^23.97^28.30^29.6334^24.20^29.25^33.15^23.02^27.83^31.5435^22.00^27.25^30.40^20.93^25.92^28.9236^21.65^25.95^25.35^20.60^24.69^24.1237^20.60^23.60^23.65^19.60^22.45^22.5038^23.60^28.95^29.35^22.45^27.54^27.9239^26.90^31.40^35.60^25.59^29.87^33.8740^23.60^25.00^26.40^22.45^23.78^25.1141^24.65^26.40^29.60^23.45^25.11^28.1642^25.00^27.15^30.80^23.78^25.83^29.3043^27.45^28.40^31.30^26.11^27.02^29.7844^23.50^26.05^28.70^22.36^24.78^27.3045^19.70^22.50^25.30^18.74^21.40^24.0746^25.15^25.35^28.15^23.93^24.12^26.7847^25.85^27.70^28.55^24.59^26.35^27.16^ 1:114=. C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at T=20 C (cont'd)484950averagest.dev.^26.60^29.55^33.7526.30^27.50^30.9025.40^26.60^30.0019.16^20.84^23.295.80^6.56^7.5125.3025.0224.1618.225.5228.11^32.1126.16^29.4025.30^28.5419.82^22.166.24^7.142(SRT=20)515253545556575859606162636465666768697029.1533.8039.4036.2033.4029.8533.2531.2030.0035.4035.5031.6533.1037.0033.6032.2031.2029.5032.0535.9534.6041.0043.1542.6037.4035.6038.2033.1034.1540.9037.9034.3538.3543.4038.8037.1033.6031.2034.3041.2027.7332.1537.4834.4431.7728.4031.6329.6828.5433.6833.7730.1131.4935.2031.9630.6329.6828.0630.4934.2030.2535.1537.1535.3031.1029.0031.8531.5029.7036.9036.3031.4034.8538.1034.4032.4530.3029.6532.3035.7528.7833.4435.3433.5829.5927.5930.3029.9728.2535.1034.5329.8733.1536.2432.7230.8728.8228.2130.7334.0132.9139.0041.0540.5335.5833.8736.3431.4932.4938.9136.0532.6836.4841.2936.9135.2931.9629.6832.6339.19C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at T=20 C (cont'd)2(SRT=20)7172737475767778798081828384858687888990averagest.dev.39.2038.7037.4538.6536.9036.3026.9532.9033.1031.1527.2521.2521.0523.2521.0022.2030.0533.0538.0537.0040.1038.3039.3038.1038.3036.8028.9536.3036.6032.4028.6022.0022.5523.6522.0021.6029.7534.5539.1537.8043.7040.5041.6038.7041.3542.7032.2038.9039.2536.6032.8526.7025.7527.8026.1027.1033.7037.0042.6041.10^32.22^32.76^36.685.07 5.10^5.0737.29^38.15^41.5736.82^36.43^38.5335.63^37.39^39.5736.77^36.24^36.8235.10^36.43^39.3434.53^35.01^40.6225.64^27.54^30.6331.30^34.53^37.0131.49^34.82^37.3429.63^30.82^34.8225.92^27.21^31.2520.22^20.93^25.4020.02^21.45^24.5022.12^22.50^26.4519.98^20.93^24.8321.12^20.55^25.7828.59^28.30^32.0631.44^32.87^35.2036.20^37.24^40.5335.20^35.96^39.1030.65^31.16^34.894.97^4.91^4.923(SRT=15)919293^43.28^39.19^41.5742.81^43.85^46.8046.61^50.18^52.56cr■45.50^41.20^43.7045.00^46.10^49.2049.00^52.75^55.25C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at T=20 C (cont'd)3(SRT= 15)94^47.75^46.60^52.10^45.42^44.33^49.5695^49.40^51.80^56.30^46.99^49.28^53.5696^47.15^46.90^49.50^44.85^44.62^47.0997^41.25^40.80^44.80^39.24^38.81^42.6298^51.35^49.00^51.70^48.85^46.61^49.1899^50.00^47.90^52.30^47.57^45.57^49.75100^51.05^48.25^53.20^48.56^45.90^50.61101^50.40^49.40^52.60^47.95^46.99^50.04102^45.55^43.15^48.80^43.33^41.05^46.42103^45.90^43.70^49.00^43.66^41.57^46.61104^44.90^42.40^47.70^42.71^40.34^45.38105^38.60^38.40^44.05^36.72^36.53^41.90106^51.70^48.80^55.90^49.18^46.42^53.18107^52.25^49.50^58.15^49.71^47.09^55.32108^40.20^43.45^45.55^38.24^41.33^43.33109^39.30^42.10^44.60^37.39^40.05^42.43110^39.75^39.45^44.55^37.81^37.53^42.38111^37.05^36.40^41.00^35.25^34.63^39.00112^38.30^37.20^43.10^36.43^35.39^41.00113^37.90^37.20^42.50^36.05^35.39^40.43114^40.50^41.10^44.70^38.53^39.10^42.52115^37.95^36.50^40.85^36.10^34.72^38.86116^43.15^39.65^46.95^41.05^37.72^44.66117^44.90^45.65^51.60^42.71^43.43^49.09118^36.75^38.25^42.00^34.96^36.39^39.95119^48.05^47.20^51.50^45.71^44.90^48.99^ '--.3.-.1 C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at 1=20 C (cont'd)120^47.50^43.75^46.35^45.19^41.62^44.09^42.43^41.68^45.965.45^5.06^5.34averagest.dev.44.604.9243.824.6748.324.804(SRT=10)121^53.70^57.60^61.25^51.08^54.79^58.27122^52.90^50.55^55.15^50.32^48.09^52.46123^45.90^46.45^47.00^43.66^44.19^44.71124^55.60^53.40^61.20^52.89^50.80^58.22125^45.60^44.45^50.45^43.38^42.29^47.99126^53.30^55.90^64.05^50.70^53.18^60.93127^64.90^62.30^70.65^61.74^59.27^67.21128^58.40^60.50^67.05^55.56^57.55^63.78129^50.20^55.00^59.30^47.76^52.32^56.41130^46.65^48.40^59.95^44.38^46.04^57.03131^50.90^57.00^66.55^48.42^54.22^63.31132^58.90^58.50^67.60^56.03^55.65^64.31133^59.80^56.65^67.20^56.89^53.89^63.93134^53.15^54.00^65.70^50.56^51.37^62.50135^52.40^51.35^59.85^49.85^48.85^56.94136^47.90^48.05^54.15^45.57^45.71^51.51137^48.20^49.50^52.95^45.85^47.09^50.37138^40.40^48.05^53.70^38.43^45.71^51.08139^58.45^59.70^64.25^55.60^56.79^61.12140^47.30^51.30^55.80^45.00^48.80^53.08141^53.85^55.85^64.25^51.23^53.13^61.12142^53.65^56.85^65.15^51.04^54.08^61.98C5: Gas Production: Volume of Gas Produced per Day (L/day) at T=35 C and Corrected at T=20 C (cont'd)4(SRT = 10)143^41.30^43.05^50.55^39.29^40.95^48.09144^57.80^58.55^65.75^54.99^55.70^62.55145^43.85^46.00^50.90^41.71^43.76^48.42146^45.75^47.55^50.55^43.52^45.23^48.09147^51.10^51.50^54.40^48.61^48.99^51.75148^46.60^48.10^53.00^44.33^45.76^50.42149^51.70^52.50^58.70^49.18^49.94^55.84150^50.25^50.55^54.90^47.80^48.09^52.23151^47.25^48.15^52.20^44.95^45.81^49.66152^43.15^45.95^51.65^41.05^43.71^49.13153^53.70^56.95^62.75^51.08^54.18^59.69154^51.00^52.20^62.05^48.52^49.66^59.03average^51.04^52.42^58.84^48.56^49.87^55.98st.dev.^5.54^4.95^6.31^5.27^4.82^6.19 APPENDIX C: Phase II - Digester Performance: Solids, Gas Production and Methane ContentC6: Methane Content (%) and Average Production per Run (L/day) Corrected at T=20 Crun # days cont expCa(OH)2 expNaOH238152259.360.757.160.260.959.160.059.462.261.058.459.559.363.761.21 29 59.4 60.9 62.2(SRT=25) 36 56.2 58.3 59.944 57.2 58.6 60.250 57.1 58.7 58.8aver. % 58.7 59.8 60.4st.dev. 1.7 1.2 1.6aver.(L/day) 10.7 11.9 13.457 57.1 58.8 58.965 56.9 58.3 58.472 55.6 57.6 59.72 78 56.7 58.8 60.2(SRT=20) 85 58.4 60.6 61.9aver. % 56.9 58.8 59.8st.dev. 0.9 1.0 1.2aver.(L/day) 17.3 18.2 20.892 55.8 57.5 59.095 55.7 57.3 59.3C6: Methane Content (%) and Average Production per Run (L/day) Corr55.2 56.9 57.955.6 57.6 57.556.6 58.3 58.257.3 57.8 58.557.1 57.6 59.555.2 57.5 58.856.1 57.6 58.60.8 0.4 0.623.2 23.2 26.353.0 51.3 56.155.0 54.8 58.856.0 56.7 59.356.0 57.6 58.354.4 57.5 59.255.1 58.0 59.456.2 57.6 59.354.0 56.2 57.656.2 58.4 59.859.2 62.1 62.155.5 57.0 59.01.6 2.6 1.527.0 28.2 32.83(SRT= 15) 99102106110113120aver. %st.dev.aver.(L/day)4(SRT=10)121125128131135138142145149155aver. %st.dev.aver.(L/day)APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusDl: Carbon: Influent and Effluent Soluble COD (mg/L)influent effluentrun # day cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 152 451 846 466 438 4484 165 358 814 686 580 6008 137 674 1417 686 584 59211 349 1009 1054 639 564 66415 109 356 788 457 384 46218 289 1174 1924 670 578 6881 22 515 1350 2292 636 580 732(SRT=25) 25 357 956 1880 680 616 76129 400 841 1669 694 613 74232 558 1160 1846 700 605 72736 328 1050 1864 767 654 80139 380 774 1869 677 570 70943 394 1161 1776 816 718 89546 272 786 1678 814 719 85750 381 1030 1782 864 712 899average 319 875 1567 683 594 705st.dev. 129 298 455 109 89 13253 416 1100 1855 842 710 91757 211 834 2042 901 765 94360 234 988 2068 901 774 912Dl: Carbon: Influent and Effluent Soluble COD (mg/L) (cont'd)64 348 1001 2373 894 753 92367 260 715 1940 941 781 94671 386 1149 2256 1019 841 10522 74 340 912 1984 996 824 1088(SRT=20) 78 296 941 1792 832 716 91681 194 923 1716 884 752 93585 159 742 1682 824 757 88488 458 838 1981 780 685 822average 300 922 1972 892 760 940st.dev. 93 129 203 69 44 7092 478 823 2033 782 686 84794 345 619 1893 821 728 89596 458 840 1954 798 706 84699 460 1055 2190 828 708 850101 345 778 1828 786 714 836103 349 736 2074 806 710 832106 418 926 2222 782 647 8213 108 376 1052 2124 862 660 844(SRT=15) 110 444 886 2034 911 666 922113 329 768 1918 920 656 914117 494 1291 2467 890 662 918120 588 950 1998 854 574 859average 424 894 2061 837 676 865st.dev. 75 171 166 48 40 35Dl: Carbon: Influent and Effluent Soluble COD (mg/L) (cont'd)4(SRT=10)808^573^738704^515^693713^518^711710^533^686807^611^782831^612^800815^589^845849^584^726870^550^578930^604^714924^584^714838^559^736825^551^794average^365^905^1938^817^568^732st. dev.^109^161^204^70 32 63122125127129132136139143146148150153155411^754^1704328^974^1791508^920^2107332^915^1986456^975^1943222^758^1573400^945^2142232^895^1726276^994^1864237^608^1814288^768^2111506^944^2167543^1310^2271APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD2: Carbon: Influent and Effluent Total COD (mg/L)influent effluentrun # day cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 10984 10456 10852 5640 6000 59804 9556 10133 9947 6594 6278 56828 8876 7832 9672 6966 6170 629411 11882 11216 12307 6279 6020 554015 4464 4347 4909 3245 3597 355018 14354 14670 13722 6436 6258 67921 22 22180 23167 21060 7096 6812 7394(SRT=25) 25 14891 13440 13616 8534 7878 750629 16589 15521 15814 6880 7488 702632 19762 18424 16246 7530 8486 741636 13590 13994 14416 8780 8396 797439 15940 17403 18330 8006 7640 781443 15751 19260 15946 8518 7974 867546 17644 15001 17067 8754 8644 833150 16210 16850 15930 9160 8620 8320average 14178 14114 13985 7228 7084 6953st.dev. 4343 4629 3872 1485 1344 131253 20390 19880 22234 10078 8940 931257 15890 17608 17248 9723 9404 938360 18924 20139 18031 10090 9846 9300D2: Carbon: Influent and Effluent Total COD (mg/L) (cont'd)6467711786516988212231802414419176921786516345183909590905590119610957789198712879583862 74 16061 15739 16824 9217 9418 9398(SRT=20) 78 15311 15834 16283 8889 8833 823581 12258 11484 11582 9191 8665 845885 10115 9671 9954 9111 7961 792188 19946 19438 19740 8909 9135 8005average 16816 16357 16772 9351 9119 8719st.dev. 3261 3236 3277 425 509 53692 16914 17998 17475 9764 8980 866294 13286 13212 12692 9484 8871 820396 14890 15192 14815 9278 8881 810699 14857 14216 14668 9575 9142 8860101 19289 20138 18478 9497 9424 9036103 15977 15750 15594 9577 8972 8632106 15692 15985 9182 8764 83803 108 13905 13393 14081 9164 8762 8267(SRT= 15) 110 12992 12780 12710 8985 8332 8155113 14686 14166 14240 8698 9144 8216117 16831 16980 16868 8117 8192 7707120 14054 13905 14128 8382 8735 8178average 15281 15248 15145 9142 8850 8367st.dev. 1710 2184 1724 490 325 353D2: Carbon: Influent and Effluent Total COD (mg/L) (cont'd)4(SRT= 10)1221251271291321361391431461481501531551374210490160191078015400111041535499081126011825127281485218651138921022816272111501520211565149299091109301175112195148661842313221112441630911002140971087314755957411218117891239615370185756908^7918^73399188^7505^74318028^7574^72127998^7812^81267996^7660^72858203^7934^74738456^7819^66867144^7182^69968313^7591^74467994^7232^68987894^8026^74968000^6482^76858186^7958^7464average^13239^13115^13109^8024^7592^7349st.dev.^2549^2598^2483^535^410^348APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD3: Carbon: Total Organic Carbon (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 68 172 199 9 5 144 58 124 219 1 1 48 46 417 10 3 2411 113 377 419 1 1 815 38 251 321 1 11 618 95 335 385 3 1 222 141 312 455 1 1 11 25 85 256 484 41 29 56(SRT= 25) 29 102 184 435 46 36 6232 149 326 472 47 38 4936 281 364 44 40 6239 100 229 587 36 30 5543 106 320 502 26 32 5546 68 237 442 31 25 3550 103 290 528 51 59 78average 91 264 415 23 21 34st.dev. 31.6 68 102.7 19.3 18.0 25.953 119 312 667 60 106 9057 56 220 509 59 53 4860 58 249 535 30 76 106D3: Carbon: Total Organic Carbon (mg/L) (cont'd)646771855064215172226656579447942710391072 74 12 132 327 163(SRT=20) 78 45 180 518 12281 34 221 457 12385 40 195 289 48 22 6188 117 213 505 62 55 82average 62 212 499 44 55 94st.dev. 31.7 43.7 112.5 17.9 32.5 36.994 95 164 438 71 59 7096 123 232 505 44 42 8092 118 139 495 61 51 56101 92 214 450 83 71 89103 81 204 579 77 51 95106 116 254 593 73 54 75108 81 272 617 75 88 983 110 121 214 552 97 88 106(SRT=15) 113 76 190 383 89 73 102117 145 358 647 95 96 128120 165 241 500 86 60 84average 112 232 526 77 67 89st.dev. 26.1 57.9 75.0 15.3 16.3 18.0122 83 181 392 87 69 84D3: Carbon: Total Organic Carbon (mg/L) (cont'd)4(SRT=10)125^85^253^482^63^48^84127^131 205 321 71 57 90129^93^220^495^57^51^81132^117 225 414^76 59 86136 56^177^397^54^47^68139^105 245^512^94 53 69143^58^234^413^68^57^99146^106 288 500^124 87 142148 68^166^545^102^86^113150^ 226 607^122 85 125153^154^281^530^89^52^85155^140 405 582 86 76 84 average^100^239^476^84^64^93st.dev.^30.4^59.7^80.1^21.6^14.5^20.7 APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD4: Nitrogen: NH4 - N (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 7.2 13.5 17.1 84.4 83.9 80.24 8.9 17.4 37.4 171.8 180.9 172.78 10.6 16.1 15.8 151.5 157.3 156.511 11.4 17.2 23.0 145.1 159.9 179.015 10.1 20.1 19.7 144.7 144.4 142.518 14.0 27.3 24.6 160.5 179.9 182.21 22 15.6 24.3 34.0 167.9 182.3 175.5(SRT=250 25 14.0 25.3 35.8 158.9 165.8 172.429 15.7 25.7 38.3 183.5 178.4 192.932 19.8 24.2 39.6 167.9 173.8 184.036 15.2 21.7 24.8 175.4 184.5 194.039 22.0 24.5 46.0 162.0 180.4 187.743 15.6 29.3 36.5 232.2 242.0 209.446 13.1 22.1 38.4 221.8 225.9 234.950 25.7 21.1 29.7 191.9 197.9 206.2average 14.6 22.0 30.7 168.0 175.8 178.0st.dev. 4.8 4.3 9.0 33.1 34.4 33.753 8.4 24.6 26.2 196.5 213.3 214.957 6.8 11.0 31.2 202.3 211.2 208.760 13.5 23.5 37.1 194.0 202.1 207.8D4: Nitrogen: NH4 - N (mg/L) (cont'd)64677116.019.218.438.829.427.139.046.042.4207.8200.3203.5216.3212.0219.8221.2216.3222.42 74 23.0 29.0 35.6 206.5 217.4 226.2(SRT=20) 78 13.4 23.6 36.2 227.5 238.8 253.081 10.8 22.2 30.5 230.4 238.4 247.585 10.1 20.2 27.8 212.6 226.4 225.388 17.0 23.0 33.8 209.5 214.9 224.9average 14.2 24.8 35.1 208.3 219.1 224.4st.dev. 4.8 6.5 5.7 11.1 10.8 13.692 22.4 28.6 34.4 225.1 230.1 241.694 23.7 23.5 37.8 221.7 232.5 239.796 22.1 26.5 35.8 215.4 226.8 242.299 20.7 29.5 44.8 225.9 231.6 250.5101 24.2 26.8 46.8 212.3 227.8 233.6103 17.4 21.1 34.4 199.7 207.8 219.3106 17.6 23.6 33.6 196.1 206.2 212.93 108 22.2 31.0 30.6 197.1 198.0 221.2(SRT=15) 110 21.2 28.9 37.4 194.9 235.0 214.5113 14.7 23.7 29.3 221.4 228.2 243.6117 18.3 20.6 23.8 212.0 216.2 235.7120average 20.4 25.8 35.3 211.1 221.8 232.3st.dev. 2.9 3.3 6.2 11.6 12.0 12.4D4: Nitrogen: NH4 - N (mg/L) (cont'd)4(SRT=10)^185.1^179.9^201.4187.9^182.1^195.9183.6^186.8^197.0186.9^191.6^200.9206.7^176.5^197.1204.4^152.0^164.5166.7^167.1^163.0160.8^160.8^162.2155.1^154.5^169.7143.9^145.5^159.0133.9^137.2^147.9144.5^147.6^164.4142.1^146.6^158.812212512712913213613914314614815015315522.3^24.2^31.214.8^21.2^22.621.2^27.9^33.316.4^20.5^26.815.4^19.4^31.413.8^18.0^26.412.7^21.0^30.113.2^16.6^22.511.1^15.9^21.59.9 16.0^26.413.3^17.2^25.212.9^19.4^29.716.2^23.5^27.0averagest.dev.14.9^20.1^27.2^169.4^163.7^169.63.4 3.4 3.6^23.7^17.3^18.8APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD5: Nitrogen: Soluble TKN (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 14.3 46.6 84.2 198.0 201.1 203.84 13.9 28.5 45.7 206.7 208.4 203.98 15.5 63.3 127.0 215.0 219.7 209.411 18.4 77.2 145.8 205.6 208.6 210.315 15.9 65.5 119.5 217.1 215.2 221.018 20.8 81.0 142.3 193.8 215.6 206.522 24.4 84.1 174.9 201.6 214.2 223.025 22.7 63.6 120.6 202.6 211.6 208.71 29 25.6 62.8 129.7 199.5 210.6 214.5(SRT=25) 32 32.8 82.7 166.3 228.1 228.1 245.636 23.2 78.1 151.0 234.0 236.0 243.339 34.2 66.8 162.6 229.3 232.1 249.343 23.5 72.6 151.8 236.8 242.4 257.546 18.7 71.5 148.6 232.2 241.8 256.750 20.0 67.5 144.7 239.9 248.6 256.3average 21.6 67.4 134.3 216.0 222.3 227.3st.dev. 5.9 14.0 32.1 15.5 14.2 20.753 22.2 72.9 146.6 251.5 259.2 272.657 16.0 65.9 157.2 265.9 251.5 277.560 19.9 78.5 184.7 259.3 267.4 268.7D5: Nitrogen: Soluble TKN (mg/L) (cont'd)64677122.223.523.277.559.580.3195.4182.3172.0269.7251.8263.1265.9260.3253.7284.7276.2304.42 74 33.4 77.9 180.1 287.3 288.3 302.9(SRT=20) 78 19.4 83.2 158.6 287.3 276.6 308.781 15.6 73.4 143.8 271.9 283.5 301.985 15.5 67.5 145.0 281.3 290.4 301.588 26.2 60.9 177.3 275.3 271.2 298.5average 21.6 72.5 168.3 269.5 269.8 14.1st.dev. 5.0 7.6 17.2 12.1 12.9 14.192 37.7 66.5 171.3 284.4 284.4 307.694 26.5 52.5 169.8 269.8 271.8 291.496 28.5 62.4 181.6 273.7 268.8 295.399 27.8 85.0 177.4 260.5 262.3 282.6101 30.4 68.5 185.1 251.3 249.4 289.4103 28.4 60.5 179.1 269.3 275.4 295.43 106 27.5 74.3 200.2 260.9 261.9 275.8(SRT=15) 108 39.5 97.3 184.8 259.2 259.2 267.0110 35.6 69.9 173.0 261.1 255.2 276.8113 21.7 64.2 170.8 271.9 262.8 278.9117 28.8 98.5 189.0 257.7 249.6 276.9120 45.4 72.8 168.1 253.3 237.6 258.2average 31.5 72.7 179.2 264.4 261.5 282.9st.dev. 6.4 13.6 9.1 9.1 12.2 13.0D5: Nitrogen: Soluble TKN (mg/L) (cont'd)4(SRT= 10)122125127129132136139143146148150153155^2 3.4^221.5^236.2^219.5^201.8^221.5197.9^195.9^226.9206.6^201.7^233.6205.6^189.1^219.1214.7^206.7^228.8207.8^193.4^232.6220.2^204.7^224.3216.1^196.5^216.1214.0^195.4^235.8205.2^194.4^218.0192.4^191.4^208.2207.2^198.3^218.0average^22.4^68.0^158.9^210.0^199.3^224.5st.dev.^4.9 10.9^11.2^8.6 8.1 8.33 .0^58.6^142.821.7^78.3^162.430.1^61.1^167.423.5^67.0^153.322.5^62.2^149.516.8^65.6^150.322.3^74.5^183.020.3^81.2^152.116.1^81.7^145.916.1^51.2^159.320.2^57.7^168.721.2^57.7^158.827.1^87.3^172.8APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD6: Nitrogen: Total TKN (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 502.6 460.6 486.3 422.2 449.7 424.94 422.0 424.4 419.3 439.4 466.6 401.08 458.0 427.6 448.0 421.6 368.2 438.511 460.4 462.4 465.2 443.6 443.6 413.415 358.5 355.7 352.7 402.4 475.4 394.618 541.5 537.7 530.8 465.6 439.4 472.422 643.0 604.3 643.2 477.9 477.9 468.21 25 559.1 548.6 539.8 470.9 500.1 485.5(SRT=25) 29 521.2 498.2 538.0 451.4 490.2 477.332 565.8 585.5 555.2 483.3 488.2 521.136 490.2 483.2 473.6 521.6 526.4 502.439 666.6 617.5 617.5 521.6 536.9 512.043 589.9 586.8 550.4 534.0 529.3 532.146 663.3 657.4 675.2 540.4 516.4 477.950 582.5 642.4 597.1 545.2 526.0 540.4average 535.0 526.2 526.2 476.1 482.3 470.8st.dev. 86.0 86.8 84.4 45.4 43.5 45.753 563.2 540.4 569.3 545.2 535.6 530.857 605.6 620.7 559.7 578.9 596.3 581.860 774.3 721.7 740.4 615.5 582.6 592.0D6: Nitrogen: Total TKN (mg/L) (cont'd)64 665.3 695.3 671.9 610.8 592.0 582.667 687.9 650.9 651.3 610.8 615.0 585.42 71 648.7 653.1 648.4 645.5 559.1 552.5(SRT=20) 74 583.9 553.6 549.6 601.2 603.2 603.278 560.5 624.2 553.6 608.1 617.8 603.281 505.6 486.5 472.8 598.0 602.9 593.285 430.0 392.0 427.4 599.0 614.1 588.988 709.4 745.4 760.5 644.4 649.5 639.4average 612.2 607.6 550.0 605.2 597.1 586.6st.dev. 93.5 101.2 99.5 26.5 29.1 26.592 572.1 604.0 583.9 643.3 644.4 624.294 530.4 510.8 525.5 618.6 613.7 594.196 540.0 532.0 528.9 573.5 550.4 545.899 521.5 522.7 527.3 591.9 564.3 559.6101 584.2 574.6 564.5 634.7 634.7 574.6103 562.5 558.8 534.0 573.7 591.1 573.73 106 626.0 618.5 591.1 573.7 583.7 538.9(SRT=15) 108 496.4 488.4 493.3 542.2 571.5 610.7110 566.4 540.7 540.7 601.3 651.8 601.3113 495.3 498.0 472.8 591.2 601.3 560.9117 527.7 552.0 538.0 542.2 561.8 518.2120 513.4 483.5 512.8 503.0 561.8 552.0average 544.7 540.3 534.4 582.4 594.2 571.2st.dev. 37.1 41.6 32.6 38.8 3a5 30.2D6: Nitrogen: Total TKN (mg/L) (cont'd)4(SRT= 10)122125127129132136139143146148150153155411.3386.8480.0396.7464.5343.8458.0338.6334.7432.7457.8506.2486.1429.5368.3501.7419.9460.5359.9510.2330.8377.8444.4466.0550.3526.2430.9342.6509.4400.5456.4327.7483.6330.8370.0452.3462.0522.2502.5^450.5^470.2^450.5499.6^460.3^430.9460.3^440.7^440.7481.8^489.6^458.6464.5^400.1^480.0400.1^416.2^404.1487.5^464.0^456.2440.5^456.2^448.3471.9^456.2^456.2456.2^444.4^440.5462.0^450.0^433.9494.1^429.9^437.9466.0^454.0^462.0averagest.dev.442.0^430.1^422.9^464.2^448.6^446.166.4^66.5^56.7^24.8^22.4^17.7APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD7: Phosphorus: PO4-P (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 43.6 39.7 68.2 94.4 94.3 93.94 49.1 24.6 73.5 93.9 91.7 94.88 45.3 14.2 65.8 87.6 95.111 33.7 25.5 56.3 89.0 81.2 97.315 44.5 24.4 62.8 91.2 80.2 92.518 39.6 28.9 57.1 89.8 83.3 93.722 42.6 35.4 71.4 78.6 81.3 95.425 51.6 41.8 79.1 84.4 79.3 94.81 29 57.6 44.7 93.1 88.7 78.2 96.3(SRT=25) 32 42.2 35.3 65.6 91.1 78.4 98.736 33.2 23.9 49.1 89.5 77.3 96.639 60.1 40.8 85.2 89.5 74.9 97.443 39.8 41.2 68.8 97.9 79.4 100.746 46.8 45.6 109.3 97.4 80.0 106.150 48.1 49.1 83.9 103.9 79.3 112.5average 45.2 34.3 72.6 91.4 81.8 97.7st.dev. 7.3 9.8 15.0 5.9 5.2 5.153 45.5 40.9 73.5 107.8 85.8 119.757 45.2 47.2 87.8 119.1 91.2 127.360 58.0 57.5 109.5 123.7 91.0 130.0D7: Phosphorus: PO4-P (mg/L) (cont'd)64677156.072.253.967.059.359.1116.895.692.3125.8134.7136.591.496.793.9137.1142.6143.92 74 75.0 50.4 93.7 139.4 92.8 145.8(SRT=20) 78 52.1 62.9 96.3 143.3 97.9 156.781 49.5 58.6 90.7 149.8 97.5 154.385 52.7 42.8 88.8 151.1 101.3 157.488 72.3 90.2 149.5 158.1 102.6 159.8average 57.5 57.8 99.5 135.4 94.7 143.1st. dev. 10.3 12.9 19.1 14.5 4.8 26.192 78.2 80.6 107.2 156.3 110.0 174.894 78.6 77.2 127.4 168.9 112.5 167.096 66.8 74.8 104.1 159.8 104.5 165.399 56.2 63.3 91.5 163.1 104.2 169.7101 69.5 80.6 137.0 158.5 105.8 163.3103 75.9 75.8 111.7 164.1 105.2 163.7106 69.2 78.9 116.3 164.0 107.2 167.83 108 72.9 55.9 102.3 163.2 100.9 172.3(SRT=15) 110 82.3 66.3 113.5 168.3 105.9 168.7113 65.2 69.9 103.2 170.0 101.9 172.1117 56.1 49.5 91.2 165.0 95.2 167.6120average 70.1 70.2 109.6 163.7 104.8 132.9st.dev. 8.3 10.0 13.2 4.1 4.4 3.5D7: Phosphorus: PO4-P (mg/L) (cont'd)4(SRT=10)^150.3^95.6^156.3137.2^86.2^137.2131.6^85.6^132.7136.6^88.6^137.8132.3^87.2^135.4133.0^84.9^130.8126.1^86.8^132.6138.6^85.1^126.9130.4^83.0^130.9124.9^78.6^121.5120.0^78.2^121.9125.6^80.8^132.3124.9^80.9^131.6average^56.4^43.5^86.7^131.6^84.7^132.9st.dev.^9.1 9.3 12.5^7.6 4.5^25.012212512712913213613914314614815015315577.4^51.8^102.051.5^37.9^72.873.0^55.8^97.860.3^41.5^77.655.5^46.8^86.553.6^32.2^86.655.3^51.1^107.044.8^26.8^70.443.8^29.1^63.556.3^51.5^98.753.8^42.9^85.654.3^54.2^92.054.0^43.5^86.3APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD8: Phosphorus: Soluble TP (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 42.5 40.6 68.6 93.1 95.0 97.54 49.6 25.4 74.1 99.1 96.2 96.78 45.8 20.2 95.2 100.9 96.7 99.111 35.9 33.7 86.8 98.6 90.4 99.615 44.6 27.0 82.8 101.4 85.0 97.018 40.4 34.0 84.0 91.5 85.5 98.422 43.1 39.7 97.0 86.0 82.5 98.625 53.8 44.7 96.5 91.7 81.6 99.41 29 58.4 45.9 99.7 90.8 78.3 97.5(SRT=25) 32 43.2 41.3 86.0 98.0 82.9 107.436 34.3 31.5 80.4 98.3 82.8 100.239 62.3 49.3 103.1 98.3 79.9 106.043 40.8 44.8 91.5 102.4 83.8 101.646 48.5 51.2 129.9 102.5 82.0 111.850 51.9 55.5 109.9 111.3 87.8 118.7average 46.3 39.0 92.4 97.6 86.0 102.0st.dev. 7.6 9.8 14.6 6.0 5.7 6.153 48.4 49.7 112.3 116.7 90.8 127.057 48.5 57.3 116.2 130.4 96.7 132.860 58.9 62.0 143.2 128.5 97.1 131.9D8: Phosphorus: Soluble TP (mg/L) (cont'd)2(SRT=20)6467717478818588averagest.dev.^58.2^67.0^155.575.0^63.8^168.356.4^65.0^137.479.1^57.2^140.056.6^70.2^137.153.1^65.9^127.455.4^50.3^133.072.3^98.8^179.760.2^64.3^140.910.0^12.6^19.5136.4141.3148.2148.2155.9149.6160.3165.8143.814.199.0^146.7107.4^150.1106.9^153.3107.2^153.5106.7^157.8109.1^156.3114.1^166.8112.1^163.8104.3^126.76.9 12.63(SRT=15)92949699101103106108110113117120averagest.dev.82.8^86.4^157.879.8^82.8^162.266.5^81.9^151.260.7^73.3^145.574.4^89.6^164.078.0^83.0^153.971.8^84.9^159.776.2^62.3^137.678.7^64.8^134.666.7^73.9^137.557.4^63.1^137.582.7^64.3^123.773.0^75.9^147.18.1 9.7 12.4169.8^120.1^173.7168.3^118.0^171.8172.3^115.0^169.3169.5^118.5^174.0161.0^120.9^171.7172.2^119.3^175.7169.8^114.3^170.8167.3^113.7^163.4166.3^110.8^164.4173.6^110.7^173.6163.3^104.5^163.3158.4^95.5^155.4167.7^113.4^168.94.5 7.1 5.8OND8: Phosphorus: Soluble TP (mg/L) (cont'd)4(SRT= 10)122125127129132136139143146148150153155^144.2^103.8^147.2^139.1^89.7^134.1132.1^87.7^137.2133.3^89.8^141.8132.3^86.8^130.3133.3^90.8^133.3130.0^83.9^138.0132.0^84.9^131.0129.0^80.9^132.0125.0^80.4^136.2132.1^87.4^134.2123.0^85.3^128.1130.1^87.4^129.6average^58.5^48.4^114.0^132.0^87.6^134.8st. dev.^8.7 8.7 9.3^5.2 5.6 5.177.1^55.4^117.952.4^43.6^112.973.1^58.5^124.062.7^45.4^109.656.3^51.8^111.554.8^38.0^111.557.0^57.5^137.046.4^33.2^101.944.4^34.9^97.961.0^56.5^120.058.4^47.2^113.858.9^59.7^111.358.4^47.5^112.8APPENDIX D: Phase II - Digester Performance: Carbon, Nitrogen and PhosphorusD9: Phosphorus: Total TP (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 143.5 140.3 142.8 134.0 140.3 147.64 149.2 142.6 152.4 149.8 157.2 145.08 180.2 173.6 176.6 151.4 145.0 147.511 155.8 159.6 152.2 145.0 152.2 135.215 139.5 139.3 136.8 139.3 146.8 136.818 166.8 176.9 174.4 151.8 151.8 170.922 191.7 176.9 184.4 159.4 156.8 156.925 191.3 184.9 183.9 151.3 158.5 156.11 29 209.4 184.9 204.1 148.9 165.7 157.5(SRT=25) 32 161.4 158.5 150.3 158.5 160.9 165.736 162.4 155.8 150.8 173.2 175.7 165.739 234.0 204.5 212.0 170.7 170.7 163.243 188.3 188.1 163.2 179.2 178.2 177.246 245.8 211.9 241.2 180.1 180.1 165.550 224.3 219.2 199.7 194.8 185.0 192.3average 182.9 174.5 175.0 159.2 161.7 158.9st.dev. 32.3 24.4 28.6 16.4 13.3 14.853 202.8 194.8 209.5 198.7 198.7 199.757 226.2 248.6 219.2 211.9 209.5 202.160 258.6 269.2 244.6 210.2 198.0 205.3D9: Phosphorus: Total TP (mg/L) (cont'd)646771242.9288.1238.9242.2250.1232.4249.5266.5234.8212.7212.7234.8206.3227.4227.4205.3210.2227.42 74 241.6 220.5 229.6 224.8 222.4 222.4(SRT=20) 78 239.6 242.3 220.0 232.1 234.5 229.681 224.7 218.4 202.5 228.0 225.6 223.285 209.6 187.6 200.0 234.8 232.2 232.388 328.1 316.8 309.4 244.8 247.2 244.8average 245.6 238.4 235.1 222.3 220.8 218.4st.dev. 34.1 33.8 30.5 13.3 15.0 14.092 261.4 269.2 259.7 252.2 252.2 244.894 255.7 240.6 248.1 248.1 238.1 238.196 245.5 239.2 231.7 241.7 236.7 231.799 247.5 241.7 231.7 251.8 241.7 239.2101 256.5 258.7 251.1 261.2 256.2 240.9103 259.7 251.5 238.9 249.0 251.2 249.0106 267.8 274.2 261.1 249.0 251.5 238.93 108 208.9 214.0 211.5 236.3 246.2 246.2(SRT=15) 110 225.4 228.6 231.1 256.9 264.7 256.9113 221.5 208.3 202.8 254.3 259.5 249.2117 212.8 211.5 206.5 236.3 246.2 227.9120 216.8 206.5 204.0 221.4 233.8 236.3average 240.0 237.0 231.5 246.5 248.2 241.6st.dev. 20.5 22.6 20.4 10.5 9.1 7.7D9: Phosphorus: Total TP (mg/L) (cont'd)4(SRT=10)122125127129132136139143146148150153155187.5153.6202.0173.6193.4165.7199.3139.9147.8191.4184.2202.3186.2197.3163.5212.0181.5187.5173.6203.1143.9151.8195.3186.2226.3194.2182.6163.3202.0163.8181.5169.7202.3139.9139.9191.4176.2194.2182.1^199.6^206.8^202.0202.0^202.0^189.9204.4^187.5^192.3203.2^197.3^193.4197.3^197.3^193.4197.3^201.3^193.4207.2^199.3^199.3187.4^191.4^183.4195.3^187.4^187.4183.4^179.5^179.5194.2^190.2^184.2200.3^174.2^178.2194.2^190.2^190.2average^185.9^179.0^176.1^197.4^192.6^189.7st.dev.^22.4^20.3^19.6^6.4 8.9 6.8APPENDIX E: Phase II-Digester Performance: Volatile Fatty Acids, Dewaterability and Environmental ConditionsE1: Environmental Conditions: Effluent pH and Temperature (C)pH Trun # days cont^expCa(OH)2 expNaOH cont^expCa(OH)2 expNaOH^7.08^7.08^7.107.04^7.15^7.067.09^7.12^6.927.02^6.88^6.857.04^7.08^6.927.03^7.05^7.0638.0^38.0^37.637.9^37.4^37.338.2^37.7^38.239.1^38.1^37.837.7^38.0^38.537.7^38.2^37.538.1^37.8^37.638.0^37.6^37.938.5^38.0^37.838.3^38.0^38.238.0^37.8^37.937.8^37.9^37.81(SRT=25)12345678910111213141516171819202134.9^34.5^34.337.9^37.8^37.938.0^37.6^38.038.0^37.9^37.638.1^37.6^37.87.00^7.11^7.097.11^7.11^7.016.89^7.04^7.117.11^7.15^6.986.93^7.07^7.057.00^7.00^7.006.85^7.10^7.057.07^6.80^7.026.70^7.00^7.006.94^6.95^6.956.95^6.86^6.706.93^6.92^6.90E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)1(SRT=25)22^6.85^7.04^7.10^37.5^37.3^37.323^7.00^7.10^7.11^37.7^37.6^37.824^6.90^6.97^7.06^38.2^38.1^38.025^6.92^6.87^6.89^37.8^37.8^38.026^6.80^7.04^7.01^37.8^37.2^37.12728^6.97^6.86^6.98^38.0^38.1^37.629^6.95^6.92^6.86^37.6^37.4^37.630^6.74^6.90^7.00^37.7^37.7^37.431^6.89^6.91^6.98^37.8^37.8^37.732^6.86^6.93^6.98^37.8^37.8^37.433^6.90^6.90^6.94^37.8^37.6^37.434^6.83^6.82^6.80^37.6^37.8^37.535^6.61^6.81^6.93^37.7^37.5^37.436^6.61^6.80^6.96^37.9^37.6^37.337^6.73^6.78^6.70^37.6^37.6^37.538^6.78^6.65^6.57^37.9^37.7^37.839^6.85^6.96^6.94^37.9^37.6^37.440^6.98^7.09^6.90^38.3^37.9^37.841^6.98^6.98^6.90^37.6^37.5^37.642^6.97^6.71^7.07^37.2^37.4^37.043^6.81^6.74^6.77^37.6^37.8^37.444^7.47^7.36^7.30^38.0^37.9^37.945^6.96^6.98^7.04^37.7^37.4^37.246^6.92^6.88^6.81^37.8^37.7^37.747^6.78^6.86^6.93^38.0^37.7^37.6 48495051525354555657585960616263646566676869707172736.716.876.936.906.916.836.906.816.806.776.856.676.776.776.776.816.886.836.796.786.806.826.786.796.716.736.696.816.916.856.916.836.906.846.826.836.876.706.756.786.706.856.766.796.796.776.776.806.786.756.756.786.706.946.936.986.996.876.956.896.956.946.846.796.796.886.766.966.946.836.896.906.876.916.836.826.856.7937.637.737.938.137.537.937.537.837.337.537.637.837.738.138.038.138.038.038.437.738.137.837.938.037.837.837.637.737.637.937.637.537.637.537.337.237.437.737.637.838.037.837.938.038.037.737.837.837.837.637.637.937.537.537.8 37.737.837.437.637.437.337.037.537.437.737.637.837.837.738.037.937.837.837.837.537.737.438.0E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)2(SRT=20)37.337.637.837.838.038.138.237.737.737.737.737.637.837.737.837.839.137.937.637.737.537.739.238.037.737.937.637.837.938.038.037.637.637.937.537.637.637.637.637.839.0 38.037.437.537.937.438.837.937.537.774757677787980818283848586878889909192939495969798996.776.726.786.966.896.916.716.876.806.856.706.836.666.776.766.626.686.736.686.736.686.736.716.816.726.736.836.776.846.966.926.936.786.916.846.876.786.886.756.846.836.656.786.756.766.756.776.766.776.836.806.766.896.746.836.916.916.886.776.906.836.846.816.916.796.856.846,646.796.736.756.686.786.746.836.806.846.7537.537.838.038.038.138.138.437.737.737.937.737.738.037.837.937.539.537.937.737.737.937.739.537.938.038.0E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)2(SRT=20)3(SRT=15)3(S RT= 15)4(SRT=10)1001011021031041051061071081091101111121131141151161171181191201211221231241256.776.796.756.816.716.776.676.746.736.936.896.906.886.816.786.756.766.746.726.626.726.676.816.736.776.616.856.816.786.796.746.756.716.736.776.946.966.926.876.866.846.816.796.816.746.716.766.756.826.796.776.686.886.806.816.796.796.746.776.706.746.876.906.866.836.846.756.816.746.816.716.736.706.876.826.846.766.76E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)^38.0^37.7^37.537.7^37.7^37.638.2^37.9^37.537.9^37.8^37.738.2^37.9^37.437.6^37.6^37.637.7^37.6^37.337.7^37.5^37.537.8^37.6^37.437.9^37.7^37.838.2^37.7^37.638.1^37.9^37.938.1^38.0^37.938.1^37.9^37.637.9^37.8^37.837.8^37.6^37.537.9^37.8^37.738.0^37.8^37.537.8^37.7^37.737.8^37.7^37.537.8^37.8^37.737.2^37.1^37.037.3^37.0^37.037.4^37.1^37.337.9^37.6^37.5E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)4(SRT= 10)126^6.90^6.98^6.92^37.4^37.4^37.4127^6.84^6.98^7.01^37.5^37.2^37.1128^6.82^6.90^6.84^37.7^37.5^37.4129^6.71^6.83^6.88^37.9^37.6^37.4130^6.73^6.80^6.80^37.3^37.2^37.3131^6.65^6.71^6.75132^6.73^6.78^6.80^36.9^36.6^36.8133^6.67^6.77^6.84^36.8^36.4^36.4134^6.70^6.75^6.76^36.7^36.5^36.6135^6.52^6.65^6.73^37.0^36.6^36.6136^6.60^6.68^6.53^37.0^36.8^36.9137^6.89^6.91^7.00^37.0^36.6^36.6138^6.95^6.96^6.96^37.2^37.0^37.1139^6.57^6.60^6.74^37.0^36.6^36.6140^6.97^7.01^6.98^37.0^36.9^36.8141^6.79^6.76^6.90^37.0^36.8^36.7142^6.82^6.83^6.80^36.5^36.4^36.4143^6.65^6.76^6.85^37.0^36.6^36.7144^6.82^6.85^6.86^36.7^36.5^36.6145^6.68^6.78^6.86^36.9^36.7^36.6146^6.94^7.03^7.03^36.9^36.7^36.8147^6.85^6.89^6.96^37.0^36.8^36.7148^6.73^6.77^6.82149^6.78^6.81^6.84150^6.82^6.88^6.92151^6.90^6.95^6.97 E1: Environmental Conditions: Effluent pH and Temperature (C) (cont'd)152 6.83 6.92 6.954 153 6.74 6.77 6.84(SRT= 10) 154 6.86 6.90 6.98155 6.69 6.76 6.79APPENDIX E: Phase II - Digester Performance: Volatile Fatty Acids, Dewaterability and Environmental ConditionsE2: Environmental Conditions: Oxidation - Reduction Potential (mV)run # day cont^expCa(OH)2^expNaOH59^-231^-236-290^-3101 19 -329^-333(SRT=25) 27 -275^-28338 -263^-27046 -242^-22555 -219^-2282 62 -224^-278(SRT=20) 70 -285^-29288 -296^-28595 -281^-2803 108 -298^-295(SRT= 15) 117 -270^-275125 -293^-301137 -281^-2934 146 -285^-281(SRT= 10) 155 -282^-290APPENDIX E: Phase II-Digester Performance: Volatile Fatty Acids, Dewaterability and Environmental ConditionsE3: Volatile Fatty Acids (mg/L)influent effluentrun # days cont expCa(OH)2 expNaOH cont expCa(OH)2 expNaOH1 57 111 118 6 4 74 49 133 197 5 5 58 28 94 88 2 4 411 158 235 254 2 9 715 17 240 87 1 2 518 96 316 235 4 6 822 211 309 341 7 9 1225 123 250 312 2 4 91 29 163 230 245 6 3 7(SRT=25) 32 237 321 313 7 7 1036 125 232 251 4 8 839 134 233 286 5 8 1243 153 325 304 4 1 1146 77 177 229 0 4 1150 163 251 231 5 5 8average 119 230 233 4 5 8st.dev. 62.7 71.6 77.4 2.1 2.4 2.553 154 257 198 4 8 957 55 122 209 3 5 1160 64 164 230 4 7 12 ,t-)--.1E3: Volatile Fatty Acids (mg/L) (cont'd)646771110591422041272582682042934368591110132 74 90 180 232 7 9 11(SRT= 20) 78 114 180 248 5 7 1181 55 172 231 4 8 1185 29 112 138 3 4 888 156 235 246 6 7 8average 93 183 227 4 7 10st.dev. 42.4 49.2 38.7 1.3 1.6 1.592 156 235 328 7 10 1494 115 110 214 5 7 1496 178 250 223 8 9 1199 178 265 276 7 12 15101 113 178 232 7 8 13103 92 182 238 4 7 9106 143 192 105 9 10 113 108 54 79 108 6 4 11(SRT= 15) 110 62 103 166 6 8 6113 94 166 126 5 8 11117 146 176 227 6 8 10120 132 175 195 6 7 11average 122 176 203 6 8 11st.dev. 39.4 55.1 64.6 1.3 1.9 2.4E3: Volatile Fatty Acids (mg/L) (cont'd)4(SRT=10)12^25^167 1 1011^15^1311 17 1312^15^77 9 1415^17^1310 14 139^15^169 10 1710^11^1314 8 70^1^1122125127129132136139143146148150153155103^158^166117 186 146127^244^151102 169 128157^204^20357 109 100127^197^20069 115 9598^154^13468 127 11284^124^139187 267 259191^266^262averagest.dev.114^178^161^10 12 1241.4^52.9^52.8^3.6^6.3^4.3APPENDIX E: Phase II - Digester Performance: Volatile Fatty Acids, Dewaterability and Environmental ConditionsE4: Dewaterability: Capillary Suction Time (sec)effluentrun # day cont expCa(OH)2 expNaOH4 22.5 15.9 15.21 18 14.1 14.3 15.4(SRT=25) 26 18.1 17.3 22.845 32.5 25.3 37.366 26.0 24.9 31.22 75 27.8 27.4 32.2(SRT=20) 87 24.5 23.5 24.93 107 26.6 23.9 36.0(SRT=15) 119 20.7 16.0 22.8130 38.6 28.5 41.84 144 32.8 24.4 30.7(SRT= 10) 151 22.1 18.7 22.1

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