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Aerobic treatment of CTMP wastewater in sequencing batch reactors Dubeski, Cara V. 1993

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We accept this thesis as conforming to the required standardAEROBIC TREATMENT OF CTMP WASTEWATERIN SEQUENCING BATCH REACTORSbyCara V. DubeskiB.A.Sc., The University of British Columbia, 1986A THESIS SUBMITTED IN PARTIAL FULFILLMENT OF THE REQUIREMENTSFOR THE DEGREE OF MASTER OF APPLIED SCIENCEINTHE FACULTY OF GRADUATE STUDIESDEPARTMENT OF BIO-RESOURCE ENGINEERINGTHE UNIVERSITY OF BRITISH COLUMBIAApril, 1993© Cara V. Dubeski, 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.(S ig n at u re) Department of Bio—Resource Engineering The University of British ColumbiaVancouver, CanadaDate^April 28, 1993DE-6 (2/88)ABSTRACTThis research evaluated the application of a bench-scale aerobic SBR system tothe treatment of CTMPTTMP wastewater. The wastewater treated was from QuesnelRiver Pulp, and had a COD of approximately 7200 mg/I and BOD5 of roughly 2700mg/I. SBR cycle times used were 24 and 48 hours, with hydraulic retention times of34.3 and 68.6 hours respectively. The 24-hour cycle consisted of 22 hoursaeration, one hour settling and one hour decant. Sludge retention times were 20days for most runs. By the end of the study, the sludge in the system had been runon effluent from the same source from the same mill for 1 and 1/2 years.For the runs without pH adjustment, COD removals of 32-41% and BOD5reductions of 70-75% were achieved by the end of each 24-hour cycle (after onehour in-situ settling). When the decanted wastewater was settled for an additionalthree hours, COD reductions of 53-59% and BOD5 reductions of 90-94% wereobtained. From intermediate time point samples, it was found that most of theoxygen demand reduction occurred within the first 16 hours of the cycle.Little improvement was found in effluent from 48-hour cycles compared to 24-hour cycles. The rate of COD removal was greatly decreased in the 48-hour cycles,even during the early hours of aeration. Comparison of columns with unregulatedpH to pH-controlled columns at 6.5 and 7.5 pH showed little difference in CODremovals. COD and BOD5 percentage removals in samples after the longersettling, were almost as high as in other aerobic systems treating similarwastewaters, though the SBR system had a higher loading.MLVSS concentrations were 3900 to 4600 mg/I at the end of 24-hour cycles, andSludge Volume Indices ranged from 54 to 78 ml/g (for reactors without pHadjustment). Sludge yields in the 24-hour cycle runs were about 0.12 kg MLVSSper kg COD removed, and 0.15-0.18 kg MLVSS per kg BOD5 removed. This is onlyabout one quarter the sludge yields typical in AS systems, both on a COD andBOD5 basis. Some recommendations for the design of an SBR pilot system for apulp mill are made.IITABLE OF CONTENTSPageABSTRACT^ iiTABLE OF CONTENTS^ iiiLIST OF TABLES vLIST OF FIGURES^ viACKNOWLEDGMENTS viiiINTRODUCTION^ 1CHAPTER 1. LITERATURE REVIEW^ 3CTMP Wastewater^ 3Aerobic Treatment of CTMP Wastewaters^ 6Foaming and Bulking in Activated Sludge Treatment^ 10The Sequencing Batch Reactor Process^ 10CHAPTER 2. MATERIALS AND METHODS 16The SBR System^ 16Aeration tests 18Biological Treatment Runs^ 19Sampling Methods^ 23Wastewater for Main Treatment Runs^ 24Analytical Methods^ 26CHAPTER 3. EXPERIMENTAL RESULTS AND DISCUSSION^29Aeration Tests^ 29Biological Treatment Runs^ 32Run A Treatment Results 41Run B Treatment Results^ 52iiiRun C Treatment Results^ 65Comparison of Runs A, B and C 79Statistical Analysis^ 89CHAPTER 4. Design and Scale-up of the SBR system^ 90CHAPTER 5. CONCLUSIONS^ 97Aeration tests^ 97Biological Treatment Runs^ 976. NOMENCLATURE SUMMARY 100Symbols^ 100Abbreviations 1007. REFERENCES^ 102APPENDIX A. Theory of Oxygen Transfer^ 108APPENDIX B. Example Nutrient Levels from Runs B and C^ 112APPENDIX C. Solids Concentrations for Runs A, B and C^ 113APPENDIX D. COD Measurements from Runs A, B and C^ 116ivLIST OF TABLESTable^ PageTable 1. Usual Range of TMP and CTMP Wastewater Characteristics^ 3Table 2. Typical Wastewater Characteristics for Quesnel River Pulp TMP andCTMP Effluents^ 5Table 3. Percentage of Total Resin Acid Content in Quesnel River PulpBCTMP Wastewater for Specific Resin Acids^ 6Table 4. KLa Values for 35°C and Air Flow Rate of 800 ml/min, andCorresponding Aeration Capacities^ 29Table 5. a Values from Aeration at 35°C and Air Flow Rate of 800 ml/min, with13 Values for Each Effluent^ 31Table 6. Characteristics of Quesnel River Pulp CTMP/TMP Wastewater^34Table 7. Volatile Fatty Acids in Untreated Quesnel CIMPTTMP Wastewater^ 38Table 8. BOD5 Percentage Removals for Run A^ 48Table 9. BOD5 Percentage Removals for Run B 60Table 10. Resin Acids and Fatty Acids in Untreated Wastewater and 22-HourSample, Run B^ 64Table 11. Reduction-Oxidation Potential During Settling Period^66Table 12. BOD5 Percentage Removal Results for Run C^ 72Table 13. Zone Settling Rates for a 24-hour Cycle of Run C 77Table 14. 15-minute Microtox EC50 for Samples from Run C^ 78Table 15. Summary of Percentage COD Removals From 24-hour Cycle Runs ^ 83Table 16. Summary of MLVSS Concentrations and Sludge Yields^87Table 17. Standard Deviation and Coefficient of Variation for AnalyticalMethods^ 89Table 18. Recommended Initial Protocol for Pilot Plant^ 93VLIST OF FIGURES Figure^ PageFigure 1. The Sequencing Batch Reactor Process^ 11Figure 2. Illustration of the Experimental Sequencing Batch Reactors^ 17Figure 3. Example Aeration Curves for Water and Wastewater with Air^ 30Figure 4. KLa Graphs of the Aeration Curves in Figure 3^ 30Figure 5. pH Values, Run A^ 42Figure 6. COD Removal (1-Hour Settled Samples), Run A^ 44Figure 7. COD Removal (4-Hour Settled Samples), Run A 45Figure 8. Average COD Removals in 1-Hour and 4-Hour Settled Samples, RunA^ 46Figure 9. COD Removals in 1-Hour and 4-Hour Settled Samples and pHValues, For Last Five 24-Hour Cycles of Run A^ 49Figure 10. Solids Concentrations, Run A^ 51Figure 11. pH Values, Run B^ 54Figure 12. COD Removal (1-Hour Settled Samples), Run B^ 55Figure 13. COD Removal (4-Hour Settled Samples), Run B 56Figure 14. COD Removals in 1-Hour and 4-Hour Settled Samples, Run B^58Figure 15. Average COD Removals in 1-Hour and 4-Hour Settled Samples forStandard Conditions Columns and Acid-Added Columns, Run B^ 59Figure 16. Solids Concentrations and Sludge Volume Index for StandardColumns, Run B^ 62Figure 17. Solids Concentrations and SVIs for Standard and Acid-AddedColumns, Run B^ 63Figure 18. pH Values, Run C^ 67Figure 19. COD Removal (1-Hour Settled Samples), Run C^68Figure 20. COD Removal (4-Hour Settled Samples), Run C 70viFigure 21. Average COD Removals in 1-Hour and 4-Hour Settled Samples forStandard Conditions Columns, Run C^ 73Figure 22. Average COD Removals in 1- and 4-Hour Settled Samples, Run C ^74Figure 23. Solids Concentrations and Sludge Volume Index for Run C^ 76Figure 24. pH Summary for Runs A, B and C^ 80Figure 25. Comparison of Average COD Removals in 1-Hour and 4-HourSettled Samples for the Standard Conditions Columns of Runs A, B and C ^82Figure 26. Solids Concentrations for the Standard Conditions Columns ofRuns A, B and C^ 86viiACKNOWLEDGMENTS I would like to thank my supervisors Dr. Richard Branion and Dr. K.V. Lo for theiruseful discussions and encouragement throughout this work.The helpful assistance provided by the shop personnel and librarian of the Pulpand Paper Centre is also gratefully acknowledged.The financial support of the B.C. Science Council, NSERC (via an operatinggrant to Richard Kerekes) and PAPRICAN is gratefully acknowledged.viiiINTRODUCTIONOver the past decade the production of chemithermomechanical pulp (CTMP)and other "alphabet" pulps has greatly increased. Much research has recently beendone to bring the knowledge of wastewater treatment technology for these pulpingprocesses up to that available for the kraft process. Although TMP(thermomechanical pulp) and CTMP wastewaters do not contain theorganochlorines that are often a focus of environmental concern with kraft processeffluents, they are highly toxic. This toxicity is primarily the result of the higherconcentrations of resin and fatty acids liberated by the high temperatures andpressures of these pulping processes. B.C. has CTMP mills discharging effluentinto both coastal and interior waters.Aerobic treatment processes such as activated sludge (AS) and aerobicstabilization basins, are well established as successful treatment methods forpulping wastewaters, both in BOD reduction and detoxification. The sequencingbatch reactor (SBR), though a proven technology for treatment of both municipalwastewater and various industrial effluents, has not often been considered forpulpmill wastewaters. The SBR process has several potential advantages that areas relevant to pulpmill wastewater treatment as to other industries where SBRs arenow being used. Some of these advantages are increased process flexibility, thecombination of equalization basin, reaction tank, and clarifier in one unit, and thelack of short-circuiting possibility for wastewater flow.This research studies the application of an aerobic SBR process to CTMPpulpmill effluent treatment. Biological treatment runs are carried out in six ten-litreSBR columns using CTMP/TMP wastewater from an interior B.C. pulp mill (QuesnelRiver Pulp). The primary objectives of this thesis are toa) study the oxygen transfer characteristics of our system for several CTMPeffluent samples,b) assess the performance of the test system with respect to such processvariables as chemical and biological oxygen demand and sludge production,c) estimate the highest effluent quality possible for this system by examining theimpact of an extended hydraulic retention time,d) compare runs with unregulated pH to pH-controlled runs to determine if anyinhibitory effect from high pH is being exhibited in the non-controlled runs, and ifpH control yields improvements in any process parameters,1e) generate design recommendations for a pilot scale CTMP/TMP wastewatertreatment system.2CHAPTER 1 LITERATURE REVIEWCTMP WastewaterWastewaters from thermomechanical pulping, including IMP and CTMP, containoxygen demand, suspended solids, and materials toxic to aquatic life which must beremoved prior to discharge. Table 1 presents the typical ranges of values forvarious water pollution parameters for TMP and CTMP, compiled from severalsources [Cornacchio 1988, Urbantas 1985, Servizi 1986a, CH2M Hill 1989, Bathija1990].Table 1. Usual Range of TMP and CTMP Wastewater CharacteristicsParameter IMP CTMPBOD mg/I 200 - 2800 1000 - 5000BOD avg. kg/adt 12.5 -46 21 -82COD mg/I 3000 - 7000 6000 - 9000COD avg. kg/adt 36.3 - 68.8 73.7 - 200COD/BOD typical 2.5 - 2.6 2.3 - 3Flow m3/adt 10 - 45 15 - 3096-hr LC50 1.3 - 35.3 % 0.83 - 1.8 %pH 6.5 - 8 7 - 8Resin acids total mg/I 2 - 100 26 -300Relative to kraft mill wastewater and domestic sewage, the COD and BOD5values are high. Typically for kraft whole mill effluent the BOD5 is 300 mg/I, COD is1200 mg/I and the COD/BOD5 ratio is 4. For sewage the respective values are 220mg/I, 500 mg/I and 2.3 [Metcalf 1979]. The high COD/BOD5 ratio for IMP andCTMP indicates that much of the organic matter present in these wastewaters is noteasily biologically degradable. However, since the BOD5 of those nonbiologically3degradable components is negligible, there should be little oxygen depletion in thereceiving water attributable to the discharge of biologically treated effluent.The LC50 is the concentration of wastewater in pure water that kills 50% of thetest organism (typically rainbow trout or daphnia) within the assay exposure period,usually 96 hours. The LC50 values shown for IMP and CTMP are quite low,indicating a high degree of toxicity. CTMP wastewater is usually more toxic thanTMP wastewater, due to the greater liberation of wood extractives.The TMP process entaiis presteaming wood chips at temperatures above 100°C,then refining them under pressure in one or more stages above 1000C [Mackie19881. The CTMP process primarily involves adding chemicals to the chips prior tothe pressurized refining, mainly sodium sulfite on a 1-4% Na2S03 per bone dry pulpbasis [Mackie 1988]. The use of sodium sulfite in the CTMP process releaseslignins, tannin, resin and fatty acids which are also released in the kraft process butnot in IMP. However, in kraft production these components are captured in thecooking liquor and burned in the recovery boilers [Reeser 1990].Toxic components in IMP and CTMP effluents are primarily natural organiccompounds extracted from the wood during the pulping process. The major groupof these is the resin acids, which account for 60-90% of the overall toxicity inmechanical pulping wastewaters [Leach 1976]. Of these, pimaric, palustric,isopimaric, abietic and dehydroabietic and levopimaric acid are major toxicants, withsandaracopimaric and neoabietic acid being minor toxicants. Resin acids havebeen shown to be biologically degradable [Leach 1977a, Servizi 1986b]. Toxicity isalso generated by neutral constituents such as pimarol, isopimarol and juvabione[Leach 1976]. As similar wood species are used in TMP/CTMP and in kraft pulping,many of the same toxic compounds are released from the wood, though thequantities liberated by the different processes vary.Quesnel River Pulp supplied almost all the wastewater used in this research.Table 2 gives the typical wastewater characteristics of the IMP and CTMPwastewaters from this mill, obtained from two recent studies at the mill. The firstthree rows of the table give information from Rankin et a/. [1992], the rest of thevalues are from MacLean et al. [1990]. The TSS values given are likely forwastewater leaving the dissolved air flotation unit, as they are consistent with thevalue for that wastestream provided by technicians at the mill [personalcommunication March 1993]. The resin acid concentrations are high compared tothe usual values shown in the previous table. This is due to the furnish used in the4interior mills which contains higher resin acid concentrations than the tree speciesused in B.C.'s coastal mills.Table 2. Typical Wastewater Characteristics for Quesnel River Pulp TMP andCTMP EffluentsParametar TMP CTMPWastewater Production 14-18 m3/adt 17-20.5 m3/adtBOD5 32 kg/adt 66-80 kg/adtTSS 12 kg/adt 12-26 kg/adtCOD 4000 mg/I 7200 mg/IBOD5 1800 mg/I 3100 mg/ICOD/BOD5 2.22 2.32TSS 300 mg/I 400 mg/IResin acids 50-200 mg/I 50-550 mg/ILC50 0.5-1.5% 0.3-1.0%Inorganic Sulfur 200 mg/I 300 mg/IH202 0 mg/I 50-100 mg/IpH 5-6 7-8Quesnel River Pulp also produces some CTMP from aspen furnish, which hasthe same water use per ton as the other CTMP, but produces about 120 kg BOD5and 18 kg TSS per air dry tonne pulp (adt) [Rankin 1992]. The total IMP andCTMP production at the mill averages 900 adt per day [personal communicationwith QRP technicians, March 1993]. If the COD and BOD5 values in table 2 arecombined for a 2:1 CTMP:TMP ratio, they fall within the range of concentrationsmeasured in the batches of combined wastewater used in this research, and withinthe current range specified by the QRP technicians for this wastewater stream.From 10 to 30% of the BOD discharge of the QRP TMP/BCTMP (bleachedCTMP) wastewater is due to the resin acid content, as the biodegradation of resin5acids exerts approximately 3 mg BOD5 per mg resin acid [MacLean 1990]. Thehigher resin acid concentrations occur in this wastewater when there is a high finescontent in the sewered whitewater, and during fresh wood usage or winter months[MacLean 1990]. The whitewater stream is specified as the major source of bothsoluble COD and toxicity for this wastewater.McCarthy et al. [1991] found that resin acids inhibit anaerobic activity. From acomparison with results for a resin acid mixture, it was evident that the presence ofresin acids alone cannot fully account for the toxicity of BCTMP wastewater toanaerobes. The wastewater studied was from Quesnel River Pulp and had a resinacid concentration of 36 mg/I. This is low for this wastewater, but within the rangeof values given for this effluent after dissolved air flotation (20-120 mg/I) [personalcommunication, Anna Rankin, QRP, 1993]. The mean resin acid percentages ofBCTMP effluent samples from five separate occasions are shown in Table 3.Table 3. Percentage of Total Resin Acid Content in Quesnel River Pulp BCTMPWastewater for Specific Resin AcidsResin acid PercentageAbietic 26Dehydroabietic 22Levopimaric / Palustric 21Isopimaric 12Pimaric 7Sandaracopimaric 6Neoabietic 6Aerobic Treatment of CTMP Wastewaters Although anaerobic treatment has advantages over aerobic treatment such aslower energy demand and the production of methane gas, it is unable to sufficientlydetoxify CTMP wastewater [Lo 1991, MacLean 1990]. Resin acids are only slightlybiologically degraded under anaerobic conditions, as has been evident from6experiences with full-scale anaerobic systems during BCTMP production [MacLean1990]. Anaerobic treatment removes a maximum of 40-60% COD and 70-80%BOD5 [Lo 1991]. Furthermore, as the information mentioned above on the toxicityof BCTMP to anaerobes illustrates, for biological treatment of strong CTMPwastewaters, aerobic treatment may be superior.Various studies have examined the performance of a range of aerobic biologicalsystems for the treatment of CTMP wastewaters, in bench-scale [Lo 1991], pilot-planfs [Rankin 1992, Campbell 1990, Reeser 1990, Servizi 1986a] and full workingsystems [Bathija 1990, McAllen 1989]. However, there is still much less informationavailable on the treatment of these wastewaters compared to kraft mill wastewaters,due to the more recent development of the TMP/CTMP industry.A recent study examined the effectiveness of several strategies of AS treatmentfor the Quesnel River Pulp mill [Rankin 1992]. The different treatments comparedwere i) a two-stage AS system at 4-day HRT, ii) a two-stage AS system at 3-dayHRT, iii) a single stage AS system at 3-day HRT, and iv) treating effluent from thecurrent upflow anaerobic sludge blanket system (UASB) in a single stage ASsystem with 2-day HRT. The influent to i, ii and iii was 80% clarified preacidificationeffluent (the same wastewater used in our research except that our wastewater wasobtained prior to clarification) and 20% gravity clarifier effluent (e.g. trench flowsand cooling water).Sludge retention times (SRT) in the single stage AS system was 20 days and 15days (a 20-day SRT was used for most of our research). The two-stage AS systemhad an anoxic selector in the second stage. For the latter part of the study a 30minute HRT anaerobic zone at the influent end of the system was added, improvingthe sludge settling characteristics. The single stage AS system with 3-day HRT,which had an 8 hour HRT anaerobic selector, had an average SVI of 105 ml/g and aMLSS of about 4000 mg/I. The 3-day HRT two-stage system had SVIs of around150 ml/g.All strategies resulted in LC50s for trout and Daphnia magna of greater than100%. Effluent pH ranged from about 7.9 to 8.3. Average COD removals rangedfrom 77-91%. BOD5 values in the final effluent (after clarification) from the differentphases of the study ranged from 14-50 mg/I. TSS concentrations ranged from 52-123 mg/I. These are both well below the current limits. It was concluded thatsuccessful treatment for this mill could be achieved with 1) a two-stage AS systemwith 64.5 hour or 96 hour HRT, 2) a single stage AS system with 64 hour HRT, or 3)a single stage AS system with 48-day HRT treating effluent from the UASB reactors.7One of the most comprehensive recent studies evaluated several parameters forthe treatment of CTMP wastewater in aerated chemostats [Lo 1991]. Investigatingthe effect of pH using a 3-day HRT and pH levels of 5, 6, 7 and 8, more than 96% ofBOD5 and resin and fatty acids (RFA) were removed at each pH. However, CODreduction increased from 70 to 80% as pH increased from 5 to 7, then decreased to74% as pH increased to 8. From 43% (pH 5) to 52% (pH 7) of the lignosulfonates inthe wastewater were biodegraded, and it was suggested that the lignosulfonatesreleased during CTMP pulping contain low molar mass compounds more easilybiodegraded than the lignosulfonates in spent sulfite pulping liquor. Good sludgesettling was achieved for all pH levels studied, with sludge volume indices (SVI)from 60-138 ml/g.When the effect of HRT was studied, it was found that with an HRT of only 0.5days (resulting in an F/M of approximately 4.5 kg BOD5/kg MLSS.d) 88% reductionin BOD5 and 96% reduction in RFA were obtained. BOD5 and COD removalsincreased significantly as HRT increased from 0.5 to 2 days, but did not increasefurther for HRTs of 3 or 5 days. SVI increased as HRT increased from 0.5 to 3days.Investigation of the effect of dissolved oxygen (DO) levels from 2.5 to 8.2 mg/Idemonstrated that a higher DO generally improved the .removal of lignosulfonates.It was also found that at lower DOs the mixed liquor generated a bad odour and thewastewater was darker. No significant differences were found in the microbialpopulations under the different pH levels, DO concentrations or HRTs studied.Evaluating the differences between treatment temperatures of 20, 30, 40 and50°C, revealed that at the thermophilic temperature (thermophilic range is 45-75°C)BOD5 and COD removals greatly decreased. Other than for the 50°C temperature,the various other treatment conditions demonstrated little variation in BOD5 andRFA removals, though COD removals were strongly influenced by changes in theparameters. SVIs obtained were all low, ranging from 30 to 138 ml/g (SVIs of under150 ml/g are associated with easily settled sludge).A study of full-scale activated sludge (AS) treatment of a variety of German pulpand paper mill wastewaters evaluated the ratio of BOD eliminated to CODeliminated [Mobius 19881. The study concluded that DO levels had no effect onCOD removal for levels above one mg/I. The best COD reduction was obtained inaeration cascade reactors (compared to completely mixed tank reactors) and twostage aeration reactors. It was recommended that to avoid bulking sludge, aerationcascade reactors should be operated at a BOD loading of about 0.2 kg/kg sludge.d,8and that the completely mixed tank systems should be operated at BOD loadings of0.25-0.35 kg/kg•d. These values are typical loadings for conventional AS system[Metcalf 1979].Many recent papers discuss the reduction of colour for kraft mill effluents, usingsuch methods as activated carbon, ultrafiltration, ozone and ozone with peroxideoxidation [Amoth 1992], various peroxygens [Saugier 1991] and biotreatment withPhanerochaete chryosporium [Chambers 1991]. However, though many otherpapers mention the problem of colour development during aerobic biologicaltreatment, no specific information was found on the reduction of colour for CTMPeffluents.Pulpmill wastewaters are generally nutrient deficient, both as to nitrogen andphosphorus [Vaananen 1988]. Though almost all the N and P in the wood dissolvesand enters the effluent in the pulping and bleaching process, these nutrientscomprise only 100-300 g P and 1500-2000 g N per ton pulp produced [Meloni1991]. A typical BOD7:N:P for pulp and paper mill wastewaters is roughly100:1.0:0.2 [Vaananen 1988].It has been established that nitrogen and phosphorus deficiency in AS causesdeterioration of sludge settling characteristics, such as bulking or loss offlocculation or granulation [Jones 1965]. Due to the higher surface area to volumeratios, the filamentous organisms implicated in bulking problems are well suited forassimilating nutrients from dilute solutions [Gostick 1990]. The nutrient requirementratio for extended aeration has been given as 100 BOD5 to 0.8 N to 0.2 P [Gostick1990], compared to the standard 100:5:1 or 100:3:0.6 used for activated sludge.Nitrogen is normally added in the form of ammonium. As using nitrate insteadmay lower operational costs, a study by Corey and Benefield [1991] examined theperformance of an activated sludge system when nitrate was the sole source ofnitrogen. They found that wastewaters can be treated effectively with nitrate. Theamounts of nitrogen and phosphorus required per unit biomass were lower forsludge grown with nitrate compared to ammonia. For each of the SRTs studied, theMLVSS was lower in the nitrate reactor and had a lower sludge yield. It was notedthat this could result in lower costs for treatment due to the lower amounts of oxygenand nitrogen consequently required. Both nitrogen sources yielded similar levels oftreatment and very good settling properties.9Foaming and Bulking in Activated Sludge TreatmentBulking occurs when filamentous organisms protrude from flocs and interferewith the compaction and settling of sludge. These organisms are usuallydistinguished on a morphological basis, as some have not yet been isolated andgrown in pure culture to be fully characterized [Soddell 1990]. Foaming, a commonproblem in AS plants worldwide, is also due to branching, filamentous bacteria,primarily nocardioform actinomycetes [Blackall 1991a]. It appears as a persistent,viscous, grey to cream-brown scum up to 30 cm deep or more [Blackall 1991b] onthe liquid surface in the aeration chamber and sometimes in secondary clarifiers[Goddard 1987]. This foam is not the same as detergent-caused foams or thosesometimes occurring at the startup of treatment plants [Soddell 1990 and referencestherein].A common foam control strategy has been reduction in sludge age with thecorresponding reduction in mixed liquor suspended solids [Blackall 1991b] and theuse of anoxic selectors (a low oxygen period or a low-oxygen chamber prior to theaeration zone) [Soddell 1990]. Anoxic or anaerobic selectors are also used toreduce the growth of some filamentous organisms causing bulking [Albertson 1987,Flippin 1992, Flammino 1989]. Other bulking control methods are implementation ofhigh to low F/M (food to microorganism) gradient, chlorination [Jeffries 1989], andpH control [Unz 1988, Hu 1991].The Sequencing Batch Reactor Process The treatability of a TMP/CTMP wastewater in an aerobic sequencing batchreactor (SBR) process was the focus of our investigations. The SBR process is acontinuing cycle of fill, react (aerate with mixing), settle, decant and optional idle(see figure 1). Some portion of the settled sludge is retained for each subsequentcycle.10I STATIC FILL 2 MIXED FILL^3 REACT FILL5 SETTLE^6 DECANT4 REACT7 WASTE SLUDGE^8 IDLEFigure 1. The Sequencing Batch Reactor ProcessFor the fill period, level sensing devices in addition to the ones at the minimumand maximum liquid volumes can be incorporated into the tank design to allow moreflexible operating policies. For example, following a static fill period, a mixed fill oran aerated fill segment may be beneficial once some intermediate fill depth isreached. The react period completes the treatment which commenced during the fillperiod. React time may be set to a specific duration or may be related to the levelin another SBR tank in a fill cycle. A major virtue of the SBR is its flexible react timecompared to an aerated lagoon or continuous activated sludge process, where thehydraulic retention time is more or less fixed. Thus, in an SBR process, a difficult-to-treat batch of wastewater could be aerated for as long as necessary (within themaximum period available before filling must restart) to reach acceptable BODlevels.The settling period is usually between 0.5 and 1.5 hours long [Irvine 1989].Because the SBR system uses its entire volume for solids separation, it may providemore than ten times the settling volume of the secondary clarifier used in acomparable conventional AS plant. The SBR also precludes the need for a solidsreturn underflow system, as mixed liquor does not leave the reactor, virtually all11sludge wasting occurs separately from the decanting of the treated effluent. As onlyclarified effluent is wasted, the SBR system also prevents the possibility of washoutof the mixed liquor solids during hydraulic surges.Withdrawal of effluent may use a pipe fixed at the desired depth and controlledby pump or automatic valve. However, a floating weir just below the liquid surfacehas the advantage of allowing maximum clarification of the effluent for the settlingperiod allowed, in that effluent is always decanted from the most clarified zone. Asthe sludge blanket may begin to rise due to gas formation, the draw period shouldnot be overly prolonged. During temporary extremely high influent flows to thetreatment system, the draw period in one tank may be terminated before theminimum level is reached so filling can switch to that tank.Idle is a holding period which may occur if another tank is being allowed to reachits maximum liquid level before flow is switched over. Sludge wasting may becarried out during this period. During long idles, aeration or mixing may be desired.Idle time can vary between different cycles if the influent flow rate varies becausethe fill time to maximum volume changes.Surface scum is easily kept within the tank by withdrawing the effluent from justbelow the liquid surface so scum removal is usually not a problem in SBRs. Thescum becomes well mixed with influent during the next fill and is therefore subject todigestion. Although if the scum level builds up it may require removal, this is not thecontinuous skimming and disposal problem common in continuous-flow AS [Irvine1989].Irvine and Ketchum note that because of the great impact of aeration and mixingstrategies, the relationships between sludge age, HRT, mass loading and tankvolume are not clear for SBRs [1989]. Also, a kinetic-based definition of sludge ageis not possible because of the unsteady-state fill and react periods. Sludge age forthis process therefore is defined simply as the biomass present divided by the massof solids wasted per day.For industries that generally or often operate close to 24-hours each day, anSBR system would usually comprise at least two tanks. If there are only two tanks,the time required for react, settle and decant in each tank cannot exceed fill time ofthe other tank. Adding a third tank of the same volume doubles the treatmentcapacity as the available time for react through idle stages is the sum of the filldurations for all other tanks, i.e. 1.5 times the volume with 1 1/3 times the daily reacttime available per tank, allows influent flow rate to be doubled. Similarly, the12capacity of a system increases if the total treatment volume is divided among moretanks. Use of multiple tanks also increases system flexibility, eliminates surgedischarges and evens out the power requirement for aeration over the day.As the SBR is a suspended growth, mixed culture system, it can in a generalsense be considered an activated sludge process. However, the conventional ASprocess is spatially oriented whereas the SBR is a time-oriented periodic processwhich could be characterized as an unsteady-state AS system [Irvine 1989]. TheSBR fulfills such functions as equalization, reaction and settling in sequential timeperiods, rather than sequential locations. This time orientation allows addedoperating flexibility. Through appropriate design of aeration protocol and tankvolume, the SBR can replace any conventional continuous AS process, includingcontact stabilization and extended aeration [Irvine 1989]. Operation of the SBR caneasily be adjusted to accommodate changing economic or regulatory conditions,changes in wastewater characteristics or fluctuations in flow rate.The theoretically ideal reactor design for biological effluent treatment in terms oftank volume requirements, has been shown to be a completely mixed reactor,followed by a plug-flow reactor (PFR) [Bischoff 1966]. Irvine and Ketchum [1989]describe the basic kinetics of such a system to show that the SBR models this idealconfiguration as far as reactor volume requirements. Due to the time-orientednature of the SBR, both the continuous flow stirred tank reactor equivalent, the fillperiod, and the PFR equivalent, the react period, can be easily adjusted comparedto the spatially-oriented conventional equivalents.The SBR process has been applied for biological phosphorus removal, nitrogenremoval, control of sludge bulking and hazardous waste treatment, and thedegradation of a wide range of organic compounds in municipal and industrialapplications. Irvine and Ketchum [1989] describe how the controlled growth ratevariations and oxygen tension variations of an unsteady state AS system such asthe SBR, can be used to mitigate the selective pressures of variations in influent todevelop a beneficial organism distribution for such processes.The objective of the SBR control policy is to regulate the selective pressures ofgrowth rate and oxygen tension to enrich for the organism distribution whichprovides the optimal result. For example, using a static fill period allows feastconditions to be established. An extended react period provides famine conditions.It has been demonstrated that alternating feast and famine conditions can be usedto control the growth of filamentous organisms [Albertson 1991, Mobius 1989]. AnSBR system used in dairy wastewater treatment, where bulking problems are13common, has reported consistently good sludge volume indices with values as lowas 25 ml/g [Albertson 1991].Nitrification/denitrification can be achieved through manipulating oxygen tensionduring the fill period. The nitrite and nitrate produced during an aerated fill periodare used as alternative electron acceptors during a following mixed fill. Forbiological phosphorus removal, anoxic and anaerobic conditions in a mixed fill canbe used to select for the desired organisms. Recent work by Qasim et al. [1992]demonstrated that (continuous flow) anoxic-aerobic and anoxic-anaerobic-aerobictreatment processes gave superior performance for biological nutrient removalcompared to a conventional aerobic process. The anoxic-aerobic process had thesame nutrient removal capacity as the anoxic-anaerobic-aerobic process. All threeprocesses had similar BOD removals and nitrification performance. SBR systemshave been used in nutrient removal applications to provide anoxic-aerobicconditions sequentially in time similar to those created in such continuous flowsystems in sequential chambers [Okada 1990, Ketchum 1987, Manning 1985, Palis1985, Irvine 1983, Silverstein 1983, Alleman 1980].Fill and draw treatment technology has been used with success for manydecades. Irvine and Ketchum [1989] give a comprehensive review of the findings ofmany SBR investigations and list a large number of full-scale municipal SBRsystems and industrial waste systems from across the U.S. Eight different full-scalemunicipal treatment facilities were evaluated in a study by Arora et al. [1985].Though the plants all had similar water quality objectives, they were operated undera wide range of design criteria. HRT ranged from 7.6 hours to 49 hours and F/Mranged from 0.18 day-1 to 0.032 day-1. The largest of the eight systems wasdesigned for an average load of 3140 m3 per day. All the plant operators reportedthe facilities were easier to operate than conventional continuous-flow systems.A disadvantage of the process for pulpmill wastewater treatment has beenuncertainty as to whether it can be operated feasibly on a large scale. MunicipalSBR sewage plants have been built and operated to handle daily flows of up to23,000 m3/d (Oklahoma), and industrial SBR systems designed to handle flows ashigh as 3790 m3/d (paper waste, Ontario) [Irvine, 1989]. Typical mechanical pulpeffluent flows are of the order of 20 m3/adt of pulp which, for a typical mill producing350 t/d, means a daily wastewater flow of 7000 m3/d. Although larger thanindustrial SBR applications found in the literature, this is well within the same orderof magnitude.14Recently work has been done on adapting the IAWPRC activated sludge kineticmodel to the computer-aided design of SBRs [Oles 1991]. The modified modelgave a reliable simulation of experimentally determined concentration profiles. Themodel could be a useful tool in the optimization of treatment strategies for SBRresearch.Other work applying a kinetic model of the SBR process to municipal wastewatertreatment, concluded that increased aeration time per cycle can decrease the netsludge production (with resulting increase in energy requirement as oxygen)[Nakazawa 1991]. Increasing aeration time per cycle would also increase thepercentage of inert suspended solids for a given SRT. Another conclusion was thatusing a fill period without aeration gives the lowest total oxygen consumption percycle, but the highest peak oxygen consumption rate. It was also confirmed thatusing an anoxic period during fill is beneficial to control filamentous growth andprevent bulking.Studying organic loading with a full-scale municipal SBR system, Irvine et al.[1985] found that under two different loadings (0.16 and 0.42 day -1 ) the energyrequired per kg of BOD5 oxidized was quite similar. Though both reactors achievedBOD5 and suspended solids of less than 10 mg/I, slightly better effluent quality wasachieved in the lower-loaded SBR, and the higher-loaded system was more difficultto operate. The more highly loaded system used approximately 30% less energyper kilogram BOD5 applied, but also had a 46% higher sludge yield, which if sludgewere treated aerobically could be expected to eliminate the cost savings.15CHAPTER 2 MATERIALS AND METHODSThe SBR System The SBR system (shown in figure 2) is composed of six 76 cm (30 inch) deepacrylic columns with inside diameters of 14 cm (5.5 inch). Each column is filled withwater or wastewater to a depth of 65 cm (25.6 inch). The aspect ratio is therefore9.3. The liquid volume in each column is ten litres. In each column is centred a 1.3cm (1/2 inch) stainless steel agitator shaft on which two 7.6 cm (3 inch) diameterstainless steel marine-type impellers are located. The first is 8 cm from the bottom,the second 50 cm. The top impeller is positioned such that it still remains fullybelow the liquid surface after all the samples required throughout the duration of awastewater treatment run are taken. The impellers were rotated at their maximumspeed of 150 RPM during all aeration periods, using a 1/2 hp Dayton DC gearmotor.Each column is fitted with a non-airtight lid made of two semicircles of Plexiglas.In one semi-circle are fitted Swageloks to hold a 1.3 cm (1/2 inch) i.d. effluentwithdrawal tube, and a 0.65 cm (1/4 inch) i.d. air line. Both of these tubes are rigidacrylic; flexible tubing is attached to both above the lid. Another Swagelok in eachlid anchors a Omega T-type thermocouple linked to a ten-channel Omega 650thermometer (Omega Engineering Inc., Stamford, CT).Each column is equipped with one small-bubble diffuser positioned on thebottom of the column against the agitator shaft so that the bubbles must flowupward through the first impeller. During the aeration tests, 3 cm long glass particleairstones were used. However, these had to be replaced after the first biologicalruns as they were found to foul easily. This resulted in too much variation in bubblesize because of differences in the blockage on airstones between the differentcolumns. Each airstone was replaced by a 12 cm long strip of perforated flexibletubing, which created bubbles of similar sizes to the previous airstones at the sameair flow rates. There was little adherence of biomass to this tubing. Both types ofaerators are commonly available at aquarium supply stores. All biological runsdocumented in this thesis used the tubing-type aerators.The six columns are positioned inside an insulated Plexiglas tank, which is usedas a water-bath with a 1500 watt Colorabath circulating heater to maintain the liquidtemperature in the columns at 35°C. A divider is positioned between the columns toprevent short-circuiting of the hot water between the entry and exit. Two Masterflex16PERISTALTIC PUMPSFOR EFFLUENTWITHDRAWL(Cole Parmer, Niles, IL) peristaltic pumps with three standard size 18 heads eachare used to decant the effluent from the columns. A Cole Parmer benchtopdissolved oxygen meter/controller and 30 cm long polarographic probe were used insome runs, with the probe positioned through a fitting in the column lid. In-situ pHcontrol when used, was performed with two Cole Parmer 7142 control/pumpsystems and Broadley James pH probes (Broadley James Corporation, Santa Ana,CA).TIMING CHAIN0.5 hp DRIVE MOTOR^ DRIVE GEAR10 CHANNELTHERMOMETERGAS FLOWMETERS 14 cm I.D.ACRYLIC TUBE10 =1c=1100100000000IMPELLER SHAFTEFFLUENTWITHDRAWAL TUBEWATER BATHFILL LINEWATER BATHMARINE-TYPEIMPELLERAUXILLARYAIR PUMPTIMING CHAINDRIVE BELTRECIRCULATINGHOT WATER BATHSMALL BUBBLEDIFFUSERFigure 2. Illustration of the Experimental Sequencing Batch Reactors17Aeration tests Aeration tests were performed using the unsteady-state aeration method [ASCE1984]. This involves writing the oxygen transfer equation in the form ofNN = dC/dt = KLa (C* - C)and integrating it (see Appendix C for definition of symbols and a summary of thetheory of oxygen transfer). From the slope of a semi-log plot of C*-C vs. time, onedetermines ika, the overall mass transfer coefficient.In the aeration test the water or wastewater is stripped of dissolved oxygen (DO)by sparging it with N2. When the DO is zero, air or 02 is sparged in and the DOconcentration is monitored using a calibrated DO probe. The probe is calibrated ina sample with zero DO and then in a sample of known DO concentration.All tests were performed using the same column, airstone and rotameter. Ifsignificant variation from the desired test conditions for gas flow rate or liquidtemperature occurred during a run, that run was discarded and repeated. Allaeration tests were run at a liquid temperature of 34-350C, except one additionalseries at 200C. The impellers are rotated at 150 RPM during all aerationexperiments as this is the maximum speed for the motor used and is the agitationchosen for the wastewater treatment trials. Air flow rates were 800 ml/min and 400ml/min. Results presented are averages of duplicate runs.All of the wastewaters used were untreated effluents from B.C. pulp and papermills:'Powell' is a CTMP chip wash effluent from MacMillan Bloedel in Powell River. Ithad a COD of approximately 5000 mg/I and a BOD5 of roughly 1300 mg/I.'Quesnel 1' is a CTMP wastewater from Quesnel River Pulp, composed ofeffluent from the chip washer and plug screw feeder. It contained no white-water ormill wash water. It had a COD of 13,000 mg/I and a BOD5 of roughly 4,500 mg/I.'Quesnel 2' is a combined final effluent from Quesnel River containing 70%CTMP and 30% TMP. It contained chip wash water, plug screw feeder wastewaterand white-water. The COD was 7200 mg/I and the BOD5 2670 mg/I.'Crofton' is a CTMP final effluent from the Fletcher Challenge mill in Crofton. Ithad a COD of 2,550 mg/I and a BOD5 of approximately 900 mg/I.Oxygen solubilities for the wastewaters were measured using the Hachspectrophotometric method [Hach 1988]. Careful dilutions were required for18analysis of the Quesnel River wastewaters, due to high levels of colour andturbidity.Biological Treatment Runs A preliminary series of 22 consecutive two-day cycle treatment runs wereconducted in the summer of 1990 using the Crofton CTMP wastewater. The seedsludge built up for these runs was 50% from the activated sludge (AS) system at theCrofton mill, and 50% from the Civil Engineering AS pilot plant at U.B.C. Nitrogenand phosphorus supplementation was used during the weeks in which the biomasswas built up and during the run, at the typical AS dosing [Gostick 1990] of 1 gsoluble phosphorus and 5 g ammonia nitrogen to approximately 100 g initial BOD5.The runs were performed in triplicate, using three of the six SBR columns with atotal volume of ten litres and a minimum volume of three litres after decanting. Thecolumns were kept at 33-35°C. Aeration was applied for 46 hours of each 48-hourcycle, at an air flow rate of 800 ml/min per column.Several runs were performed between September 1990 and May 1991 usingQuesnel River Pulp wastewater, but did not reach completion due to inadequatewastewater supplies. Runs were abandoned when only 40 litres of wastewaterremained, and then this remaining wastewater was carefully aliquotted to keep thesludge of one column fed until more wastewater arrived. By the end of theresearch, sludge had been grown continuously on this particular CIMP/TMPwastewater for 17 months.Each time sludge from the one column was divided among additional columns toagain grow up the required amount of biomass, nutrients were added at the rate of 3g N to 0.6 g P to 100 g influent BOD5 until the desired solids concentrations wereestablished. Sludge wasting was not performed for the first two weeks duringbiomass regeneration, and then sludge wasting was resumed as usual. Most runsused sludge retention times of 20 days, so 1/20 of the sludge volume was wastedper day after thoroughly mixing the volume remaining after decanting.One test successfully carried out in spring 1991 used four columns at 35°C, witha 24-hour cycle with 34.3 hour hydraulic retention time (HRT = 10 litre total liquidvolume divided by flow rate of 7 litres per 24 hours). The sludge residence time(SRT) was 20 days and the liquid volumes were as per the Crofton tests. Twocolumns were fed nutrient at the beginning of each cycle based on 100 g initialBOD5 to 3 g N to 0.6 g P, using urea and diammonium phosphate for nutrients. Theother two columns had no nutrient added. For the runs on Quesnel River Pulp19wastewater a greatly increased air flow rate of 2.5 l/min per column was supplied.This was primarily to provide improved mixing, but part of the increase was alsorequired because the KLa in the Quesnel CTMP effluent was only 3/4 the value inthe Crofton CTMP wastewater.The main biological treatment trials were carried out in the SBR system fromJune 1991 to February 1992. Three different batches of CIMPiTMP wastewaterfrom Quesnel River Pulp were treated (referred to below as A, B and C). Theexperimental SBR system consisted of up to six columns run in parallel with areactor volume of ten litres each, with seven litres of wastewater treated per cycle.The columns were kept at 35°C, and were supplied an air flow rate of 2.5 l/minuteeach, except where otherwise specified. The sludge used had, by the start of run A,been run on CTMP Wastewaters for a year. However, it was reinoculated with seedsludge from the Civil Engineering pilot plant to maximize the variety of speciesavailable for selection under the various conditions of these later runs.Each wastewater was used in a 24-hour cycle run for at least 20 days, followedby a 48-hour cycle run which lasted until that batch of wastewater was exhausted,typically another 22 days. The 24-hour cycles have 22 hours of aeration followedby one hour of settling. The treated wastewater is then decanted, a portion ofsludge is wasted to maintain the desired sludge retention time (SRI), and thecolumns are refilled. The 48-hour cycles are the same except with 46 hours ofaeration. HRT of the 24-hour cycle is 34.3 hours and 68.6 for the 48-hours cycle.All columns were run at 20-day SRTs, with the exception for wastewater C of onecolumn run at 30-day sludge retention time (SRT).If the SBR system had been automated, or if the assistance of a second personhad been available, a shorter cycle time than 24 hours could also have beenstudied. An 18-hour cycle with 25.7 hour HRT would have been used for one run.The lower cycle times of 18 or 24 hours are closer to that expected for the scale-upof such a system than the 48-hour cycle. The SRTs of 20 days and 30 daysspecified in this research are nominal SRTs, as these were calculated based on thesolids wasted intentionally at the end of each cycle and do not consider the smallamount of biomass wasted in the treated effluent (discussed further in Results andDiscussion).Before the start of every run, all sludge was thoroughly removed from thesystem, mixed well and equally aliquotted back to each column. This was to ensurethat all columns started each run without any differences in biomass carried over20from previous tests. This mixing and pouring of warm sludge was the only operationof the research to generate any emissions that annoyed other lab users.Any sludge that accumulated on the inside walls of the columns (due to foaming)was thoroughly scraped back into the reactors every day. The head space allowedfor in selecting the liquid volume for runs had been based on early treatment trials.It provided adequate room for the maximum expected foam layer, so that nobiomass would be unintentionally wasted from the top of the columns. In all runsevaporative losses of the wastewater ware not great (about 4% in 24-hour cycles ofruns A, B and C), because of the fairly high aspect ratio of the columns.Acid added and pH-controlled runs were performed to determine if the slow ratesof COD removal after 16 hours aeration were in part due to inhibition by the highpHs which developed during the cycles. These runs were also used to examine pHeffects on sludge settling characteristics and foaming. Other research [Unz 1988]has proposed pH adjustment as a possible aid in sludge bulking control.Run A used three columns tested under the same standard conditions (2.5I/minute air, uncontrolled pH, 20 day SRI). The 24-hour cycles ran starting June 12through the cycle starting July 6 for a total of 25 cycles. The last 24-hour cycle wasthen continued an additional 24 hours, becoming the first 48-hour cycle (this wasalso done in runs B and C). This was done to maximize the number of 48-hourcycles possible from the quantity of wastewater remaining. The 48-hour cycles ofrun A continued to July 31 (13 cycles).Run B had two columns (1 and 6) at standard conditions, and two columns (4and 5) with 50 ml of 2 N sulphuric acid added to each at the four-hour markimmediately after removing the four-hour samples. The other two columns were runon pure oxygen, column 2 at 7 mg/I DO and column 3 around 20 mg/I DO. Run B24-hour cycles started September 5 using an earlier batch of the Quesnelwastewater for the first 11 days (to maximize the duration of the 24-hour cycles),switching onto "B" wastewater on September 16. 24-hour cycles continued throughthe September 26 cycle, for a total of 22 cycles. The acid additions and pureoxygen activation were begun September 15, as it was desired to build up equalamounts of sludge in all columns before changing the conditions.48-hour cycles ran from September 26 until October 18 (11 cycles). For the 48-hour cycles acid addition was discontinued, as the two previously acid-addedcolumns were now being used primarily to maintain sludge for the next run. As thissludge would be mixed in with the other sludge, and 4 of the 6 columns in the next21run would not have pH control, it was desired that this sludge be reacclimatized toconditions of no pH adjustment. Though these two columns could not beconsidered replicates of the two columns which continued at standard conditions,analyses were still performed on them for the 48-hour cycles of run B.The two columns that had in the 24-hour cycles had acid addition, as carefullyrun duplicates, provide a further quantification of between-column variation. It wasalso interesting to observe if they equilibrated at a different rate to the change to 48-hour cycles than the two stand.,rd conditions columns. They also provided someindication of what the 48-hour cycle COD removals would be for columns at slightlylower pH than the columns that had never had acid addition.For the 24-hour cycles of run C, two columns were run at the standardconditions, one column was run at pH 6.5, one column was run at pH 7.5, onecolumn was run using a controller to maintain the dissolved oxygen (DO) level at3.0 mg/I, and one column was run with an SRT of 30 days. For the pH-controlledcolumns, sulphuric acid was used. In mill applications, other acids such asphosphoric acid might be used; here sulphuric acid was used specifically to avoidadding any nutrients to the controlled columns and so prevent introducing anothervariable between columns.For the 48-hour cycles of run C, two columns were run at the standard conditionsand one column was run at 30-day SRT. The 48-hour cycles of 30-day SRT did notcontinue long enough to ensure reaching 30-day SRT equilibrium conditions, butdoes provide information on where the longer SRI data was heading relative to the20-day SRI results. The pH 6.5 column was also continued, but with pH controlhalted. It was being fed to keep sludge active for a possible subsequent run. As itwas being operated anyway, samples were taken for analysis, as it might beinformative to see how quickly the COD removals and sludge characteristicsapproached those of the standard conditions columns.Run C 24-hour cycles started November 14 using another batch of wastewater,switching to wastewater C on November 20. The 24-hour cycles ended after theDecember 5 cycle, for a total of 22 cycles with the last 16 on wastewater C. The 48-hour cycles began December 5 and ended with the December 19 cycle (eightcycles).All batches of Quesnel River Pulp wastewater used in this research were effluentspecifically collected when the same combination of CTMP and IMP pulps werebeing produced using the same furnish. There was therefore almost no22reacclimatization necessary when the feeds were switched over to B and C batchesof wastewater after the start of those runs. The data presented in the results areonly from cycles after the wastewater source had been switched over to batches Bor C.After the wastewater for trial C had run out, and it had been four days since thelast feeding, another student using the same batch of wastewater finished his runand made available to this project another 60 litres of wastewater. It was decided touse this wastewater by continuing on 96-hour cycles with the two standardconditions columns for another 16 days, for a total of five cycles ending January 8.Though such long retention times would not be designed for using an SBR system,these cycles could be used to provide some information on how such parameters assludge settling characteristics in our system might change during a short near-starvation period, such as might occur if pulp production was temporarilydecreased.For these 96-hour cycles the sludge removal rate was halved, because little orno net sludge production would be expected with such a long treatment period. Thesludge removed was the minimum necessary to allow full sludge measurements.Though this removal rate would correspond to an SRT of 40 days, an SRT is notmentioned for this run in subsequent discussion, as the columns were onlybeginning to approach that sludge age by the end of this short run, and the sludgeconcentrations were still clearly decreasing, so to specify an SRT would beerroneous.SVIs were performed for three cycles in run A, and almost all cycles in runs Band C. Settled sludge volumes were noted for most cycles, including those early inthe runs before sludge concentrations were measured. This was done becausethese volumes served as an indication of the system beginning to come toequilibrium. The sludge volumes were also found to be a reliable indicator of anychange in system parameters, e.g. sludge volumes were quickly affected by anysignificant interruption in air supply.Sampling Methods Effluent samples were taken at the end of the settling period, i.e. at 23 or 47hours into the cycle, with some samples also taken at 0, 2, 4 and 16 hours.Samples are designated according to the hours of aeration that had occurred priorto sampling, with the start of aeration being defined as zero hours, thereforesamples are referred to as 0, 2, 4, 16, 22, 46 or 94-hour samples. Samples for COD23tests were frozen immediately after sampling. Samples for other tests were kept intightly closed containers with almost no air space and stored in a refrigerator at 4°Cuntil analysis.Samples were taken from the columns with full mixing on, except in the case offinal points, i.e. 22-hour sample of 24-hour cycles and 46-hour sample of 48-hourcycles, which were taken after settling. Except for these final samples, samples atall time points were settled for one hour after sampling (to equal the one hoursettling the final samples had in the columns), and the clarified wastewater wasused to fill the sample vials.Additional samples for CODs were settled for a further three hours at roomtemperature in beakers, and the supernatant poured into sample vials. Theextended settling was done in capped sample vials, to continue at the virtually zeroDO that existed in the covered SBR columns by the end of one hour settling. Thisextended settling, though not necessarily identical in impact to exactly four hoursadded settling in-situ, would indicate if significant improvement in the effluent couldbe had with increased clarification. The samples collected after the additionalsettling were generally a clear supernatant, and are therefore referred to in the texteither as four-hour settled samples or supernatant samples.Each sludge sample was the biomass wasted from the column by subtracting therequired fraction of the sludge after the decanting period. The sludge was mixedthoroughly before the samples were removed from each reactor. Sludge samplesare designated by the date of the beginning of the cycle, with the sample beingtaken at the end of the cycle. As sludge samples were taken just before thecolumns were refilled, measurements on these samples accurately show the initialsludge concentrations for the following cycle. These are calculated by dividing thesolids in the retained sludge volume over the total liquid volume after refilling, i.e.solids concentration * 3 I (sludge volume) /10 I (filled total volume). These initialsludge concentrations are shown in the various graphs reporting solidsmeasurements.Wastewater for Main Treatment Runs The Quesnel River Pulp wastewater consists of approximately two parts BCTMPwastewater and one part IMP wastewater. It is 65-70% whitewater and 30-35%wastewater. The furnish is approximately 55% white spruce, 40% lodgepole pineand 5% alpine fir. The effluent is obtained immediately upstream of the air flotation24unit. The average chemical oxygen demands (COD) of the batches used for runs A,B and C were: A - 5980 mg/I, B - 8990 mg/I, C - 6860 mg/I.The average BOD5 of wastewaters A, B and C were 2240 mg/I, 3190 mg/I and2600 mg/I, for COD to BOD5 ratios of 2.67:1, 2.82:1 and 2.64:1. The pH ofwastewater A ranged from 6.55 to 6.67 with an average value of 6.60. The pH of Branged from 5.82 to 5.93 and averaged 5.88. C ranged from pH 6.25 to 6.34, withan average of 6.29.All wastewater used in the research, was stored in a walk-in refrigerator at thePulp and Paper Centre, maintained at 2-40C. Each batch of Quesnel Riverwastewater (shared by two or three research projects) was shipped in two one-tonne totes by truck, generally taking 2 days in transit. When the wastewaterarrived it was pumped into 23 litre plastic pails, filled as fully as possible and tightlycovered. It was requested of the person pumping the effluent to avoid entrainingthe fibrous settled solids at the bottom of the tank, as it would be impossible todistribute this material evenly among the pails, and would also be difficult in turn todivide evenly among the columns. It would also be impractical to try to withdraw thewastewater from the pails without risking resuspending some of this material, andwould result in the wastage of too much wastewater.If more cold storage space had been available, larger batches of wastewatercould have been stored. This would have permitted far fewer runs to be performedas all runs could have been carried to completion, and would have enabled alltreatment tests to be extended to a duration equal to several SRTs as is desirable.Wastewater for each cycle was taken out of the refrigerator 15 hours in advance toallow it to come to lab temperature (210C).Wastewater was screened through 1/4 inch mesh and then passed through a 0.5mm mesh filter before being used. The filtering was done to maximize thehomogeneity of the wastewater (both between different columns and different days),as occasionally small pieces of wood or clumps of fibres were found in the pails. Itwas particularly important for the accuracy of the solids analyses that such materialbe excluded from the columns. The screening was done just before the wastewaterwas poured into the columns, as it aerated the wastewater and it was not wished tointroduce additional oxygen into the wastewater before it was used.Near the end of runs B and C a few wastewater pails were found to have grownlarge fungus colonies on the surface of the wastewater. These pails of wastewaterwere not used for the runs.25Analytical Methods Temperatures were measured in-situ using 1-type Omega thermocouples(Omega Engineering Inc., Stamford, CT) connected to a Omega 650 ten-channelthermometer measuring to +1- 1°C. The temperature of at least one column wasalso verified each cycle using a glass thermometer with 0.5°C divisions. SamplepHs were measured using a Broadley James (Broadley James Corporation, SantaAna, CA) pH probe and Cole Parmer meter (Cole Parmer, Niles, IL), and were doneon all wastewater samples as soon as they were removed from the reactors. Redoxmeasurements were made using a Broadley James combination electrode with thecalibration checked in pH-buffered quinhydrone solutions. Dissolved oxygenreadings were taken with a YSI meter and YSI 5700 DO probe (Yellow SpringsInstruments, Yellow Springs, CO).CODs were conducted on previously frozen samples using the closed vialmethod from Standard Methods for the Examination of Water and Wastewater[1989] for all earlier runs and run A. CODs for runs B and C were carried out usingpurchased Hach COD vials which come prefilled with reactants (potassiumdichromate, mercuric sulphate and sulphuric acid similar to the standard method).CODs were performed on both the samples settled for one hour and the samplessettled an additional four hours.The coefficient of variation (CV) for CODs on the extended clarification sampleswas found to be quite low, permitting the use of only single COD vials for allsubsequent tests of these samples. Duplicate vials were prepared for CODs on allone-hour settled samples, however, as these samples were less homogeneous andtherefore the within sample variances were higher. A few CODs were alsoperformed on centrifuged samples, to compare to values for the extended settlingsamples.All other analyses were performed on samples settled for one hour, as this wasthe actual settling period in the SBR protocol used. BOD5 and solids tests werealso performed as outlined in Standard Methods, using fresh samples stored withinthe recommended time limits. Because samples for CODs could be frozen, CODswere performed on all the wastewater samples described, but BOD5s could beperformed on far fewer because of time demands during the running of thebiological tests, and the many hundreds of BOD bottles that would have beenrequired to analyze all the samples within the allowed storage period.26BOD5s were done on one of the last two cycles of both the 24-hour and 48-hourcycles of each run, as it was desired to have BOD results for treatment as close toequilibrium as possible. The inoculant for the BOD dilution water (important for theuntreated wastewater samples) was fresh sludge from the reactors. This seedsludge was therefore extremely well acclimatized to the samples tested.Sludge Volume Index measurements were carried out similarly to the standardmethod but the settled sludge volume used in the calculation was determined fromin-situ measurements. This was because not enough sludge was wasted per cycleto allow use of the one litre graduated cylinder described in Standard Methods (oran Imhoff cone). Therefore, the only significant differences between the twomethods was that the 30-minute settled fraction was measured in a larger cylinderand was stirred near the vessel wall by slowly rotating the columns forward andbackward, rather than with thin rods rotating around the periphery (recommendedperipheral speed no greater than 1.3 cm/s). Sludge depths were measured to thenearest 1/4 inch. This was the greatest precision realistically possible in mostcases, due to the slight unevenness of the surface of the sludge.Zone settling rates were determined for all columns at the end of the 24-hourcycles of run C. Again these analyses were performed in-situ as far too little sludgecould be removed without interfering with the runs, to allow the measurements to beconducted in a separate apparatus. The differences between our technique and thestandard method, are that Standard Methods recommends the use of a cylinder atleast one m high and the SBR columns were only 76 cm high, and the requiredperipheral stirring was supplied by slowly rotating the columns rather than by usingrods circling within two rod diameters of the internal wall (as in the settled sludgevolume method). This test was done at the end of one stage of the run because thecolumns were allowed to settle longer, a total of 100 minutes, for these tests and itwas not wished to alter the settling period during a run.Ammonia and nitrate analyses were carried out as per Hach Spectrophotometricmethods: Ammonia Nitrogen - Salicylate method and the MR (mid-range) Nitrate -Cadmium Reduction method respectively [Hach 1988]. Orthophosphate analysiswas also according to a Hach spectrophotometric method: Reactive Phosphate -PhosVer 3 (Ascorbic Acid) method. Four additional samples were analyzed usingStandard Methods for total Kjeldahl nitrogen and total phosphorus, by TakisElefsiniotis of Civil Engineering at U.B.C.Resin acid analyses were performed on stored frozen samples by AlexandraKwong at the Paprican Vancouver Laboratory using chemical extraction followed by27gas chromatography [Paprican internal procedures]. Microtox analysis was done ona few samples. The Microtox unit was not available and functioning properly untilseveral months after the treatment runs were completed. A few samples from run Chad been preserved at pH 2 and 40C. It was thought that though these were notideal storage conditions or durations, these conditions would have less potentialimpact on the toxicity than freezing of samples. These samples should allow somerelative comparison of their toxicity. pH of the samples was adjusted to 7.0 beforeMicrotox analysis, and both the additions of acid and base used in the dilutioncalculations.28CHAPTER 3 EXPERIMENTAL RESULTS AND DISCUSSION Aeration Tests The KLa values determined at an air flow rate of 800 ml/min for the four CTMPwastewaters tested, varied from 60 to 83% of the '<La values measured in waterunder the same conditions (Table 4). (The corresponding aeration capacitiesshown were calculated using equation 6 shown in Appendix C).Table 4. KLa Values for 35°C and Air Flow Rate of 800 ml/min, and CorrespondingAeration CapacitiesLiquid KLa^hrl Oc g/hTap water 12.54 0.99Powell 9.64 0.73Quesnel 1 7.52 0.55Quesnel 2 8.78 0.64Crofton 10.43 0.80Typical aeration curves for clean water and Quesnel 2 wastewater, arepresented in Figure 3. The KLa graphs for those two runs follow (Figure 4), usingthe aeration data points between 20 to 80% oxygen saturation, adjusted such thatthe first point used appears at time zero.29_-a 80 -oCo= 60 -illu)40-00 20 -100 - •M----.,.."--^ODODDDimll DOD—ri—n0-1:31=1• '—,---^,-,0• u/ 0• DEIjorz 001100( O/ 0/j0/-0— Quesnel 2 BCTIVIP Wastewater—N— Clean Water-000—1 0.2 -0.0I^I^Iill2 4^6^8^10 12 14 16TIME (Minutes)Figure 3. Example Aeration Curves for Water and Wastewater with Air1.4;....,, 1.20II0 Quesnel 2 BCTMP Wastewater• Clean WaterI^I^I^I^i^I^I^I1 2^3^4^5^6^7^8TIME (Minutes)Figure 4. KLa Graphs of the Aeration Curves in Figure 330Table 5. a Values from Aeration at 35°C and Air Flow Rate of 800 ml/min, with 13Values for Each EffluentWastewater a 0Powell 0.77 0.96Quesnel 1 0.60 0.92Quesnel 2 0.70 0.93Crofton 0.83 0.97The wide range of alpha values for the CTMP wastewaters used (Table 5),illustrates the importance of aeration testing using the actual wastewaters to betreated, for design and optimization of aeration systems. If an assumed a value isused in aerator design, the probability exists that either under-design of the system,or significantly increased and unnecessary capital and operating costs would result.Two series of aeration runs were performed at an air flow rate of 400 ml/min, halfthat used for the other air tests, to illustrate that KLa is not directly proportional to airflow rate. At 35°C in clean water, the KLa at 400 ml/min was 7.97 hrl , 64% of thecorresponding value for 800 ml/min. At 35°C in Quesnel 1 wastewater, the KLa was4.65 hr-1, 62% of the value for 800 ml/min. The a value for the Quesnel 1wastewater at 400 ml/min was 0.58.Three aeration runs were conducted in Quesnel 1 wastewater at 20°C todetermine if the generally accepted theta value of 1.024 for temperature correctionwould apply. For an air flow rate of 800 ml/min and agitation at 150 RPM, the(K0)20 was found to be 6.4 hrl, 85% of the (KLa)35. Solving for 0 (using equation4 described in Appendix C):(K0)35/(KLa)20 = 035-201.17 = 035-200 = 1.011Though this limited series of tests is not adequate to determine an accurate 0, itshows that the usual 0 of 1.024 would be high for this case. Using 1.024 for 0 here,would result in an overestimation of (KLa)35 by 22%. Though the standard 0 valueis adequate for most applications between 10 and 30°C, researchers have observedOs from 1.01 to 1.05 depending on temperature [Bass 1977].31A second series of tests at 20°C performed in clean water gave a '<La of 11.0hrl, 88% of the value for clean water at 35°C. Using a 0 of 1.024 to adjust the(KLa)20, would have overestimated the (KLa)35 by 21%. From these aeration testsat 20°C, an a value of 0.58 was determined for Quesnel 1 wastewater at 20°C andan air flow rate of 800 ml/min.The three a values determined for Quesnel 1 wastewater in the above testsvaried slightly under the different conditions. However, the differences were smallcompared to the variability of KLa between different wastewnters in the first series oftests.Two sets of aeration tests were performed at 35°C using pure oxygen at a flowrate of 800 ml/min. The KLa values for pure oxygen aeration of clean water andQuesnel 2 wastewater were 96% and 95% respectively of the corresponding valuesfor air. The slight decrease in the values for oxygen was considered due to lag inthe DO probe response, which only becomes noticeable at the high rate of increasein oxygen pressure that occurs during the pure oxygen tests. The effect of the DOprobe lag could also be observed on the KLa graphs, as the curves for all of thepure oxygen tests were slightly concave from above.A second series of aeration tests for pure oxygen was conducted for two of thewastewaters - Quesnel 2 and Crofton. The tests were performed at an oxygen flowrate equivalent to that in the air runs, i.e. at 20.9% of 800 ml/min, therefore 170ml/min. The KLa values were 37 and 38% of the corresponding values for air, in theQuesnel 2 and Crofton wastewaters respectively. The corresponding aerationcapacities for these two tests are 1.15 g/h and 1.47 g/h, approximately 1.8 timesthose at the same temperature with air at the same flow rate of oxygen. If it wasassumed that the aeration capacity would be 4.8 times greater for pure oxygendelivery than for air containing the same quantity of oxygen, the flow rate of oxygenneeded for this system would be greatly underestimated.Biological Treatment Runs As mentioned in Materials and Methods, several runs were unable to reachcompletion due to inadequate wastewater supplies. Several runs were also abortedafter building power failures, as both the SBR temperature control and, mostcrucially, the aeration was shut down. One shorter power failure occurred while theresearcher was present, so aeration was supplied by oxygen cylinders for the houruntil power was restored. One run was reaching completion in March 1991 when32another student, seeing the aeration turned off during the decanting period, turned itback on, resulting in two thirds of the sludge being wasted.In 1991 there were also problems with the air compressor in the Pulp and PaperCentre, which was the source of air for aeration. The compressor cut out severaltimes, supposedly due to overheating from low UBC water pressure. Duringcompressor failures, sludge was aerated using the oxygen cylinders which werealways kept on hand for such emergencies. However, due to the temporary mid-cycle anoxic conditions which existed until the researcher observed the aerationstoppage, and the change in aeration while oxygen was used (fluctuations in DO,sometimes with very high DOs, and differences in DO among the columns, as onlyone dissolved oxygen controller was available), it was considered necessary torestart the two runs affected. To summarize, runs which could not be used for databecause they were not completed were a result of extraneous factors, not problemswith the SBR process itself.The preliminary series of 22 consecutive 48-hour cycle treatment runs using theCrofton CTMP wastewater, were performed primarily to "debug" the system. OnceCOD removal efficiency stabilized, the runs consistently showed 31-35% CODreduction after 24 hours and 43-47% COD removal by the end of the 48-hour cycle.Except for the first hour after aeration was recommenced, the DO level was neverfound to be below 3 mg/I. The DO was usually near the saturation value of 6.7 mg/Iduring the final 34 hours of the 46 hours of aeration.All other runs were performed using Quesnel River Pulp combined CTMP/TMPwhitewater and wastewater. The pH, BOD5 and COD for the specific batches A, Band C were presented in Materials and Methods. The overall range ofcharacteristics for this wastewater stream were detailed by the technicians at themill [personal communication, March 1993] and are presented in the following table.The values are for the combined wastewater before entering the dissolved airflotation clarifier, except for the resin acid value which is from immediately after. Inthe final column of the table are the typical values for the same parameters aftertreatment, before discharge into the Fraser River. This effluent has been treated inan upflow anaerobic sludge blanket (UASB) system with an HRT of 8-10 hours, andthen an aerated stabilization basin with an HRT of 2.9 days.33Table 6. Characteristics of Quesnel River Pulp CIMPTTMP WastewaterUntreated Wastewater Final Treated EffluentCOD 5,000-10,000 mg/I 1700 mg/IBOD5 1,500-3,500 mg/I 200 mg/ICOD/BOD5 2-3 8.3TSS 900-2,000 mg/I 480 mg/IpH 5.75-6.75 not givenTotal Resin Acids 20-120 mg/I ^ 2 mg/ILC50 <1% >100%The runs conducted on Quesnel wastewater to assess the need for nutrientaddition showed no significant difference between the four columns. The influentCOD was 6700 mg/I, final CODs in the nutrient added columns were 3940 mg/I and4170, and in the no addition columns were 4140 mg/I and 4100 mg/I. The CODremovals were therefore 41 and 38% for the two nutrient added columns, and 38and 39% for the two columns without addition. The difference between theaverages of the pairs is extremely small (65 mg/I) compared to between-columnvariation for replicate columns in some other runs. Though the decision to not usenutrient addition for the subsequent tests was based on these results, in retrospectthis may have been premature. The effects on sludge settleability caused bynutrient scarcity may take longer to appear than the duration of this test.Nutrient analysis of clarified samples of the influent and treated effluent from acolumn without nutrient addition (near the end of the run), showed that the levelswere low but probably adequate. Total Kjeldahl nitrogen of the influent was 16 mg/I,and 5 mg/I in the 24-hour effluent. Total phosphorus was 4.7 mg/I in the influentand 2.5 mg/I in the 24-hour effluent.Though the treatment system used was an activated sludge process, due to thelong aeration periods and long hydraulic and sludge retention times used, and thelow sludge yields produced in early runs, the nutrient requirements could beexpected to be closer to the 100:0.8:0.2 BOD5:N:P required for extended aeration[Gostick 1990] rather than the "rule of thumb" 100:5:1 generally allowed for AS.The wastewater used for runs in the spring of 1991 (including the nutrient to no34nutrient addition comparison run) had an average COD of 6700 mg/I, and BOD5 ofabout 2300 mg/I, and average nutrient levels of 12 mg/I nitrate-N, 1.5 mg/Iammonia-N and 3.3 mg/I orthophosphate-P. The BOD5:N:P ratio (including bothnitrate and ammonium nitrogen) was approximately 100:0.59:0.14. Though this isonly 73% the nutrient ratio recommended by Gostick, the nutrient concentrationspresent in the columns during treatment were never found to drop below acceptablelevels. It should also be noted that much of the Kjeldahl nitrogen that was notinitially in the form of ammonia was also utilized in the process, as shown by thedecrease in Kjeldahl nitrogen levels mentioned above.The recommendations given in a presentation on pulpmill wastewater treatmentby the CH2M Hill engineering consulting company, were used as a guideline forlevels of nutrients [CH2M Hill, 1989]. They are 1.5-2.5 mg/I ammonia nitrogen and0.3-0.5 mg/I soluble phosphorus as minimum recommended operating levels for AStreatment. Based on the information cited in the literature review, which states thatusing nitrate as the primary nitrogen source should not impair treatment, bothammonia and nitrate nitrogen were added in calculating available nitrogen to meetthis guideline.Though concentrations varied somewhat for the different batches of wastewater,in cycles without nutrient addition ammonia-N was generally around 0.2 mg/I at theend of 24-hour cycles, nitrate-N was about 6 mg/I and orthophosphate-P was about0.7 mg/I, consistently exceeding the minimums cited above. It was found thatnutrient concentrations at the end of 48-hour cycles were typically a little higherthan at the end of 24-hour cycles. This is thought to be due to nutrients released inthe digestion (during later hours of the 48-hour cycles) of some of the sludge thathad built up during the 24-hour cycles. Some nutrient measurements from laterruns B and C are shown in appendix C.All these nitrate, ammonia and phosphate values are from supernatant from fullycentrifuged samples as the spectrophotometric methods used would not beaccurate for samples containing suspended solids. Though the organic solids ofpulpmill wastewater are not high in nitrogen or phosphorus, the nutrients liberatedfrom the solids during treatment likely contributed to the nutrient pool.It must be noted that a portion of the solids wasted each cycle after settling,actually comprises suspended solids from the influent which became settleablematter during treatment. While some of the wastewater solids are broken downduring treatment, some is also simply added to the biomass during settling. The35sludge added by these non-digested solids does not constitute any nitrogen orphosphorus demand.Though there was not a drop in COD removal with no nutrient addition for thesespecific conditions, it must be noted that we are not suggesting that otherapplications of SBRs to pulpmill effluents would not require nutrient addition. If thewastewater were any lower in nutrient to BOD ratio than the effluent used here, ormore rapidly degradable, or if a lower HRT or SRT were used, nutrientsupplementation would be required. However, running the research system withoutadding unnecessarily high levels of nutrients is of relevance, given increasingconcerns about effluent nutrient levels.One batch of Quesnel wastewater not used in this research, would indeed havebeen too low in nutrients to maintain the desired biomass. Therefore, even for ourlow-demand system, not all batches of this wastewater could be assumed to beadequate without nutrient supplementation. Because of this fluctuation, in full-scaleimplementation of such a system at that mill, nutrients would be added to everycycle. Also in practice, due to the high cost of aeration, it would be better to incurthe cost of a moderate dosing of nutrients rather than risk having to unnecessarilyprolong aeration due to a decreased rate of substrate degradation from nutrientlimitation.It was not practical with our manually-operated system to use any cycle timesunder 24 hours. Lower cycle times were also not important for the study due to thehigh BOD5 concentrations in the influent. In addition to the one-day cycle times(HRT of 34.3 hours), a second cycle time of 48 hours (HRT of 68.6 hours) wasstudied. Though the mass loadings for the 48-hour cycles (0.29-0.33 kg BOD5applied/kg MLVSS.d using average MLVSS values from final two cycles) were stillwithin the range of conventional AS systems, this longer cycle time represents anextreme of SBR operation.Information from the extended cycle time runs can serve to gauge the maximumpossible BOD and COD reduction possible for our system, and verify whether or notthe COD remaining after the shorter retention times could possibly have beenreduced by any significant amount by further increasing the retention time. Theresults show that the organic load remaining after 34 hours retention time could notbe significantly reduced simply by increasing the aerobic reaction time.The early runs that did not come to completion did demonstrate what minimumfinal liquid volume was adequate to fully contain the settled sludge for our solids36concentrations and the range of sludge volume index experienced, and preventsolids from being drawn into the effluent withdrawal tube. This minimum volumewas found to be about 2.8 I, therefore the minimum liquid volume for all subsequentruns was set at 3 litres - 30% of the total liquid volume.In only one run was the allowed head space of 11 cm found to be inadequate tocontain the foam generated near the end of each cycle. In late 1990, foaming onthe columns filled the head space and it was necessary to reduce the liquid volumeto 8.5 I. By the timP the run was terminated (due to lack of wastewater), at the endof cycles the foam completely filled the 20 cm high space and was beginning toprotrude through the openings in the lids. It was evident that foaming was apotential concern for the system (apparently due to the high pH reached near theend of cycles) so records on foaming were kept on subsequent runs.Some cycles in a run in January 1991 were conducted using a two-hour settlingperiod at the end of cycles instead of one hour, with no drop in COD removals at thefour-hour sample points of the subsequent cycles. This indicates that the greatersettling period did not have a significantly deleterious effect on the health of thesludge. The longer settling period did result in notably better COD removals at theend of the settling period.Typical sludge settling times used in SBRs range between 0.5 and 1.5 hours[Irvine 1989], so a one-hour settling time was selected for all subsequent runs. Itwould not be recommended to extend the settling time for a full-scale system muchover two hours without further study, as no examples of full-scale systems using asettling period of over two hours were found in the literature. Irvine [1989]recommends that the sum of settle and draw periods should usually be less thanthree hours.At the end of March 1991, one column was completely cleaned of sludge andused to test the removal of volatile fatty acids (VFAs) from the wastewater byaeration alone. The column was aerated at 2.5 Umin air for 22 hours (at 350C) andthen influent and effluent samples were tested using high-performance liquidchromatography (HPLC). The wastewater used was a batch of the QuesnelCTMP/TMP wastewater with a COD of 8700 mg/I. The VFAs present in theuntreated wastewater are shown in table 7 below. The total VFAs in the untreatedwastewater were 2,277 mg/I, and 2,076 mg/I in the aerated wastewater, for areduction of 8.8% during the aeration period. This indicates that during biologicaltreatment, little of the reduction in volatile organics can be attributed simply tovolatilization.37Table 7. Volatile Fatty Acids in Untreated Quesnel CTMP/TMP WastewaterAcid Acetic N-Caproic Formic N-Valeric Propionic 1-Butyricmg/I 814 712 466 193 56 36On two different days, influent for the next cycles did not come up to 21°Cbecause the lab temperature was temporarily lower, so the wastewater was heatedto 21°C using immersion heaters in the pails. The wastewater was continuallymixed during heating so the wastewater was not locally heated much above thedesired temperature. During all runs liquid temperature in the columns were veryconsistent, being 27-28°C when the fresh wastewater was first mixed into thecolumns, 34-350C by two hours, and always 35°C before four hours. Once thistemperature was reached, temperature fluctuation in the columns was generallywithin +/- 10C, with 37°C occasionally being reached, but the temperature was notobserved to drop below 34°C during runs A, B or C. In pulp industry applicationthere would also be a temporal temperature gradient in the SBR, but this would befrom a higher initial temperature.In all runs that were interrupted due to power or air compressor failure, it wasfound that the aeration stoppage, even if only an hour long, was reflected in the pHat the next time point measured being significantly lower than the previous valuesfor that sampling time. If pH is monitored during treatment, it might serve as aninexpensive early warning of any upset to the system as an adjunct to othermonitoring systems such as dissolved oxygen.In run A, at the beginning of each cycle (zero-hour time point) the DO wasalways higher than 4 mg/I. At both the two and four-hour points DOs were at least1.5 mg/I. At the 16, 22 and 46-hour time points the oxygen concentration wassaturated. In runs B and C, at the zero-hour mark DO levels were greater than 2mg/I. At both the two and four-hour points during all cycles, DOs were at least 1mg/I, but rarely over 2.5 mg/I. At the 16-hour sampling point, DO ranged between5.5 mg/I and saturation. At the 22 and 46-hour marks the DO was at saturation.The 24-hour cycle runs of A, B and C are considered to have reached or verynearly reached equilibrium conditions, as both the stable COD removals and sludgevalues show. The 48-hour runs are not considered long enough to have reachedequilibrium, but the COD removal results from these runs probably do accuratelyindicate removals that would occur once steady-state was reached, as little38movement in these values was usually evident by the end of the runs. However, thesolids concentrations still appeared to be moving towards lower values at the end ofthese runs so the final solids are probably still higher than equilibrium values,particularly for runs B and C.After the one-hour settling of the zero and two-hour samples, (particularly thezero-hour samples from 48-hour cycles), a little of the material still suspendedappeared to be small sludge flocs. However, the suspended solids wasted in theeffluent at the end of cycles appeared indistinguishable from the fine suspendedsolids in the influent, i.e. most of the suspended material in the influent becomessettleable during treatment, but not all settles during the one hour. The sludge flocssettled much more quickly than this material, so in most cases (for the later timepoints), the primary difference between one-hour and four-hour settled samples isthought to be the result of the slow but eventual settling of these suspended woodsolids.Almost all flocculated biomass is already settled after one hour, with a littlevariation visible between different columns (there is also likely variation betweencolumns in the small amount of non-flocculated cells still suspended in thewastewater). Therefore, though some VSS is wasted in the effluent, this is notconsidered to significantly affect the SRT, as at the end of all cycles most of thebiomass appeared to have settled. (VSS measurements of a few effluent samplesare discussed under run B.)Eight samples from run A were centrifuged and compared to identical sampleswhich instead of centrifugation had been given the additional settling of three hours,but in a refrigerator at 4°C to minimize biological activity. The CODs of thecentrifuged samples gave values approximately equal to those of the samples fromextended settling for six of the samples. The other centrifuged samples had CODsof 94% and 97% of the same samples subjected to the additional three-hour settlingperiod, i.e. a significant amount of solids had remained suspended after four hoursin only these two samples.Because six of the eight extended settling samples had CODs similar to thecentrifuged samples, it is evident that most of the clarification possible had occurredby the end of the three hours of additional settling, so little would be gained byfurther increasing this settling period. For almost all samples given the (roomtemperature) extended settling in runs A, B and C, the supernatant was visuallyfound to be as clear as centrifuged samples and almost free of suspended solids.39Eight other samples (two each of time points 0, 4, 16 and 22 hours from run A)were settled for four hours in the refrigerator and compared to identical samples thatinstead had been settled at room temperature. The small amount of endogenousrespiration which likely occurred in the settled biomass of room-temperature settledsamples would have had no effect on the comparison to samples settled inrefrigeration, as only the COD in the supernatant after settling was measured. Itwas found that there was good agreement between the refrigerated and room-temperature settled samples for the 16 and 22-hour point samples (room-temperature samples had CODs of 97-99% of the refrigerated samples). Therewere slightly lower CODs (4% lower) in the room temperature samples from thefour-hour point, and a significant drop in the COD of the zero-hour point (9% lowerthan the refrigerated zero-hour sample).This demonstrated that during the low-oxygen settling period, very littleadditional wastewater degradation will occur in the later samples to supplement theCOD reduction that already occurred under favourable conditions during lengthyaeration. However, in the zero-hour samples, there are significant concentrations ofeasily-degradable organics of which some is utilized by the biomass in the sample(particularly until the dissolved oxygen is exhausted, although there is alsoassumed to be a little activity by facultative anaerobes). All other settling wasconducted at room temperature, as refrigerated settling would have no relevance tofull-scale treatment.The small amount of biological activity during the extended settlings of samplesis not very significant for the COD measurements, but results in a proportionallylarger change in the BOD measurements (as the BODs are so much lower thanCODs, especially at later time-points). Therefore, this biological activity likelyaccounts for a portion of the drop in BOD5s between the one-hour and four-hoursettled samples. The small amount of biomass still suspended after one-hour thatsettles out during the further three hours, would also cause a reduction in BOD5 thatwould be more significant than in the COD measurements. The less digestiblewood solids that settle out during the extended settling are thought to be the majorpart of the drop in CODs, but would be less significant in the BOD5 measurements.For all the graphs of COD removals in the following section it should be notedthat results for zero-hour samples do not only reflect the drop in the influent CODthat occurs upon mixing with the wastewater remaining in the column from theprevious cycle. During the one or four hours of settling the samples are given aftersampling, there is significant settling of the suspended material from the influent40and a small amount of biological activity occurs (as discussed above). Zero-hoursamples were taken to determine the impact of this improved settling on CODs, sothat the reduction in CODs by the two or four-hour time points would noterroneously be attributed merely to aerobic digestion of the wastewater organics.The suspended matter in the influent does not settle during quiescent conditionsin wastewater storage, but dramatically improves in settleability after being mixedwith the sludge. This is considered due to the rapid absorption of a significantfraction of the organic matter onto the flocs, as in a contact stabilization process.The samples took up to ten times longer to fully clarify than for the flocs to settle.The material that settles much more slowly probably has little adsorbed biomass.Run A Treatment ResultsRun A was conducted to study the performance of the system under standardconditions and to determine the between-column variation, before runs wereperformed applying different conditions to various columns. This between-columnvariation is quantified throughout this section by averaging the columns on allgraphs and showing error bars depicting the 90% confidence interval for agreementbetween columns.Run A used three columns tested under the same standard conditions: 20-daySRT, 2.5 l/min air flow rate and no pH adjustment. BOD5 of the influent was about2300 mg/I, for a BOD5 to COD ratio of approximately 1:2.6. The 24-hour cycles ranstarting June 12, 1991 through the cycle starting July 6 for a total of 25 cycles. Thelast 24-hour cycle was then continued an additional 24 hours, becoming the first ofthe 48-hour cycles, which continued to July 31 (13 cycles).Figure 5 shows pH values at the 0, 2, 4, 16 and 22-hour points during the final24-hour cycles. After the axis break are shown pH values at the 0, 4, 16, 22 and46-hour points of some of the 48-hour cycles. All values are averages of the threereplicate columns. The error bars represent 90% confidence intervals for this andall other figures showing error bars. As the replication between columns is quitegood, the fluctuation shown between different days during the run is accurate. Thisvariation is greater than the fluctuations exhibited in COD removal and solidsconcentrations.419.08.5 -7.5 -7.0^Jul 1^Jul 3^Jul 5^Jul 11^Jul 17^Jul 23^Jul 29HR —0-2 HR^4 HR —v--- 16 HR ----22 HR -x- 46 HRFigure 5. pH Values, Run AThis figure shows pH values at the 0, 2, 4, 16 and 22 hour points during some final24-hour cycles of Run A, which started June 12, 1991. After the axis break areshown pH values at the 0, 4, 16, 22 and 46 hour points of some of the 48-hourcycles, which started July 6. All values are averages of the three replicate columns.The error bars represent 90% confidence levels. There is good replication betweenthe columns. The readings appear to be stabilizing. Comparing the final few daysof both portions, pH values at time points in the 24-hour cycles are significantlyhigher than the same time points during the 48-hour cycles. However, pH values atthe end of 24-hour cycles are comparable to the pH reached in 48-hour cycles.42The pH readings from the last few 24-hour cycles appear to be stabilizing.Comparing the final few days of 24 and 48-hour cycles, pH values at time points inthe 24-hour cycles are significantly higher than the same time points during the 48-hour cycles. However, pH values at the end of 24-hour cycles are comparable tothe pHs reached at the end of 48-hour cycles.COD removal percentages at the 0, 2, 4, 16 and 22-hour points during somefinal 24-hour cycles of Run A are shown in figure 6. After the axis break are shownCOD removal percentages at the 0, 4, 16, 22 and 46-hour points of the final 48-hourcycles. All values are averages of the three replicate columns. The readings fromthe last few 24-hour cycles appear to have reached equilibrium. Comparing thefinal few days of both portions, COD removals at time points in the 24-hour cyclesare significantly higher than the same time points during the 48-hour cycles.Figure 7 shows COD removal percentages at the five time points each of thefinal 24-hour cycles and final 48-hour cycles, for supernatant from samples given anadditional three hours settling after the initial one hour. All values are averages ofthe three replicate columns. The COD removals in these last 24-hour cycles appearto be stable. Comparing the final few days of both portions, COD removals at timepoints in the 24-hour cycles again are significantly higher than the same time pointsduring the 48-hour cycles.The COD error bars of both figures 6 and 7 show that there was a small amountof between-column variation, however the differences between the columns wereconsistent day-to-day in the 24-hour cycles, so the error bars are quite similar insize. The proximity of the zero-hour points to the four-hour points can be deceptive.Though a large amount of treatment occurs during the first four hours of aeration,some of this treatment is also accomplished during the extended settling of thezero-hour samples, raising the zero-hour line close to the four-hour data,particularly for the 48-hour cycles.Average percentage COD removals are shown in figure 8 for the triplicatestandard conditions columns of run A. The graph shows COD removal in both one-hour settled samples and supernatant from additional settling. An average of thelast three cycles of each part of the run are used to calculate the five time pointseach of the 24-hour and 48-hour cycles. Though all 24-hour cycle points are higherthan the result from the same aeration time in the 48-hour cycles, the difference ismost dramatic for the zero to four-hour points. The biomass at the end of the 24-hour cycles must be much healthier, resulting in increased treatment during both theone-hour and four-hour (supernatant) settlings of the zero-hour samples.4310 —040 —3080 20 —c*"^/1^Jul 1^Jul 3^Jul 5^Jul 11^Jul 17^Jul 23^Jul 29—0-0 HR —0-2 HR —A-4 HR —v— 1611R —0-22 HR —x— 46 HRFigure 6. COD Removal (1-Hour Settled Samples), Run AThis figure shows COD removal percentages at the 0, 2, 4, 16 and 22 hour pointsduring some final 24-hour cycles of Run A, which started June 12, 1991. After theaxis break are shown COD removal percentages at the 0, 4, 16, 22 and 46 hourpoints of some of the 48-hour cycles, which started July 6. All values are averagesof the three replicate columns. The error bars represent 90% confidence levels.The readings from these last 24-hour cycles appear to be stabilizing. Comparingthe final few days of both portions, COD removals at time points in the 24-hourcycles are significantly higher than the same time points during the 48-hour cycles.4460 —20 —10 —^fi^04030 —c*"50 —Jul 1^Jul 3^Jul 5^Jul 11^Jul 17 Jul 23 Jul 29—D— HR —0— 2 HR —A-4 HR —v— 16 HR —0— 22 HR —x— 46 HRFigure 7. COD Removal (4-Hour Settled Samples), Run AThis figure shows COD removal percentages at the 0, 2, 4, 16 and 22 hour pointsduring some final 24-hour cycles of Run A, which started June 12, 1991. After theaxis break are shown COD removal percentages at the 0, 4, 16, 22 and 46 hourpoints of some of the 48-hour cycles, which started July 6. COD values shown arefor supernatant from samples given four hours settling. All values are averages ofthe three replicate columns. The error bars represent 90% confidence levels. As inthe previous graph, the readings from these last 24-hour cycles appear to be stable.Comparing the final few days of both portions, COD removals at time points in the24-hour cycles are again higher than the same time points during the 48-hourcycles.450^2^4^16 22^0^4^16 22 46TIME POINT (hr)^1-HOUR SETTLING^4-HOUR SETTLINGFigure 8. Average COD Removals in 1-Hour and 4-Hour Settled Samples, Run AAverage percentage COD removals are shown for the triplicate standard conditionscolumns of run A. An average of the last three cycles of each part of the run areused to calculate the 0, 2, 4, 16 and 22 hour points of the 24-hour cycles, and the 0,4, 16, 22 and 46 hour points of the 48-hour cycles. Error bars show a 90%confidence interval for agreement between cycles. Though all 24-hour cycle pointsare higher than the result from the same aeration time in the 48-hour cycles, thedifference is most dramatic for the 0 to 4 hour points. The biomass at the end of the24-hour cycles must be more active, resulting in both increased treatment during the1-hour and extended settlings of the zero-hour samples.46Figure 9 illustrates the cycling of COD removals and pH for the 0, 2, 4, 16 and22 hour sample points of the last five 24-hour cycles, with zero hours of thecumulative time shown being set at the zero-hour point of the first of these fivecycles. Both results from one-hour settled samples and supernatant from additionalsettling are shown. Though pH increase tapers off by the 16-hour points, there isstill notable COD removal in both one-hour and four-hour settled samples betweenthe 16 and 22 hour points. Both COD series appear to show equilibrium. pHequilibrium lags slightly behind, so in the first couple of these five cycles a smallincrease is still seen in pH.A great amount of COD removal is effected simply by subjecting samples to onehour settling after fresh influent is mixed into the columns. In run A, these "zero"hour points show approximately 23% COD removal. This is a combination of threefactors: a) the dilution of the influent with the three litres of treated wastewaterremaining in the column, b) biological activity that continues during settling,particularly until the oxygen that entered the wastewater during straining is used upand c) the visible improvement in settleability of wastewater solids resulting fromthis hour of biological treatment.As mentioned previously, settling that occurs during this hour would not haveresulted by simply allowing the wastewater to remain under quiescent conditionswithout exposure to the biomass. The wastewater used has little settleable solidsprior to this treatment as most settled out in the shipping containers. The settledmatter in the individual stored buckets is not put into the columns (as discussed inMaterials and Methods), partly because only buckets filled from near the bottom ofthe shipping containers have any noticeable amount, and it would amplify between-day variation in the influent to include this.The difference between the zero hour COD removals from the 24-hour cyclesand the 48-hours cycles is very large. The biomass must be far more active at theend of the 24-hour than at the end of the 48-hour cycles, and therefore is far moremetabolically active during the hour of settling of the zero-hour points of the 24-hourruns. This difference is not due to any difference in DO at the beginning of thecycle, as the sludge remaining in the column was always at zero DO, thewastewater being poured into the columns was always subjected to the samemethod of straining, and the brief non-aerated mixing was of the same duration inboth cycles and in any case would have added little to the DO. Though there weresmall differences in DO at the time the zero-hour samples were taken, this is47considered to be primarily due to the difference in the biomass activity affecting thespeed at which the oxygen from the influent is exhausted.In the 48-hour cycles, the zero-hour removal is actually only about 60% of whatwould be expected purely from the dilution of the influent with three litres treatedwastewater. This means that the settleability of the biomass has actually decreasedfrom the process of being mixed and undergoing another hour of settling. This mustbe because at the end of the hour of in-column settling the flocs are vulnerable tobeing broken up by mixing, some of which is carried oi it at the end of the cycle toallow the sludge sample to be taken, and the rest which occurs when freshwastewater is mixed into the column. This destruction of the flocs is notexperienced by the 46-hour samples because they are taken right at the end of thesettling period (immediately before the sludge is mixed for sampling). Thedisruption of the flocs would also have been occurring in the 24-hour cycles, but theincreased biological activity could recoup the COD removal losses, and in additionthe healthier flocs may have been less susceptible to fragmentation.Percentage removals of BOD5 for samples from near the end of the 24-hourcycles and 48-hour cycles are given in table 8. All values are averages ofquadruplicate tests. For the 22-hour samples an average of 19.6% additional BOD5removal results from the extended settling. The influent BOD5 averaged 2240 mg/I.Table 8. BOD5 Percentage Removals for Run ADate Sample hr Column 1-hr settling% BOD5 Removal4-hr settling% BOD5 RemovalJuly 05 22 4 73.77 92.99July 05 22 5 71.69 92.30July 05 22 6 75.00 93.87July 05 22 average 73.49 93.05July 30 46 4 77.29 90.61July 30 46 5 78.02 92.48July 30 46 6 78.89 91.92July 30 46 average 78.07 91.67489-81ca.70^20^40^60^80^100^120TIME (hr)—0— 1-HOUR SE I I LING —0— 4-HOUR SETTLING —0-- pHFigure 9. COD Removals in 1-Hour and 4-Hour Settled Samples and pH Values,For Last Five 24-Hour Cycles of Run AThis figure shows COD removals and pH for the 0, 2, 4, 16 and 22 hour samplepoints of the last five 24-hour cycles of run A, with 0 hours of the cumulative timeshown being set at the 0-hour point of the first of these five cycles. Error barsrepresent 90% confidence levels. Though pH increase tapers off by the 16-hourpoints, there is still notable COD removal in both 1-hour and 4-hour settled samplesbetween the 16 and 22 hour points. Both COD series appear to show equilibrium.pH equilibrium lags slightly behind, so in the first couple of these five cycles a smallincrease is still seen in pH.49Foam heights at the end of the aeration periods increased slightly during theearly 24-hour cycles of run A, stabilizing at heights of 8 to 10 cm (occasionallyreached the underside of the column lids 11 cm above liquid surface). The foamhad some substance, but dissipated within three minutes of aeration being halted.During the first 48-hour cycles, the foam reached heights of 9-11 cm (during the firstcycle also filled the small opening in the lid). However, by the end of the run thefoam heights were typically 7 to 9 cm.Mixed liquor total solids, total suspended solids and volatile suspended solids forrun A are shown in figure 10. All values are averages of the three replicatecolumns. The values for June 25 to July 5 are from the final 24-hour cycles, andlater dates show values from some 48-hour cycles near the end of the run. Valuesfrom the 24-hour cycles show quite stable levels for all three solids measurements.The concentrations from 48-hour cycles are slowly decreasing. The final 48-hourvalues and corresponding wasted sludge rates are approximately 60% of the 24-hour values. From the sludge volumes measured for one of the 24-hour cycles andthree of the 48-hour cycles of this run, the SVIs for the 24-hour cycles were 57-61ml/g and 63-76 ml/g in the 48-hour cycles.The sludge concentrations in the individual columns show more cycle-to-cyclevariation than is evident in this graph, as averaging the three columns tends tosmooth this fluctuation. This is also seen in the figures of sludge concentrations forrun B which show averages of duplicate columns.503500E 3000CO0— 25000(1) 2000("N^ N.).• \.).•ep op S ,zrb 6>, ,zfrr^\Co 90 (19, et re (jib 0§)11/LTS i M_TSS^M_VSSFigure 10. Solids Concentrations, Run AMixed liquor total solids, total suspended solids and volatile suspended solids areshown. All values are averages of the three replicate columns. The error barsrepresent 90% confidence levels. The values for June 25 to July 5 are from the 24-hour cycles which started June 12, 1991, and later dates show values from the 48-hour cycles which started July 6. Values from both parts of the run show quitestable levels for all three solids measurements, though the values from the 24-hourcycles portion show slightly less variation. This might be expected as the first partof the run was of longer duration. The 48-hour values and corresponding wastedsludge rates are roughly 60% of the 24-hour values.51Run B Treatment ResultsRecommended pH operating ranges for AS systems are 6.5 to 8.5, with theoptimum pH between 6.8 and 7.5 [CH2M Hill 19891. The reactors in run A reacheda pH of approximately 8.7 by the end of 24-hour cycles, and earlier runs hadreached pHs as high as 8.8 in 24-hour cycles. Run B was performed to determine ifthe high pH being reached at the end of all cycles was limiting the activity of thebiomass during the later hours of aeration. This was assessed by comparing resultsfrom columns run at standard conditions to columns having acid added during eachcycle to limit the pH reached. It was also attempted to compare the standardcolumns to columns using pure oxygen-activation, but this was not successful.Run B had two columns (1 and 6) at standard conditions. Two columns (4 and5) were run identically to these except that 50 ml of 2 N sulphuric acid were addedinto each column immediately after the four-hour samples were taken (for pH controland possibly sludge bulking control). Columns 2 and 3 were run on pure oxygen.The pure oxygen-activated columns had lower COD removals than the othercolumns and falling sludge concentrations, but this is considered likely due to thedecreased mixing caused by the lower gas flow rates required. It was observed thatthe sludge flocs in the air-activated columns were being broken up to a far greaterdegree. Once the columns were switched over to pure oxygen, the sludgeconcentrations began dropping significantly Because of the poor mixing in theoxygen columns, the results from those columns are not considered representativeof oxygen-activation and the those results are not discussed further here.Run B 24-hour cycles started September 5, 1991 using an earlier batch of theQuesnel wastewater for the first 12 days, switching onto "B" wastewater onSeptember 17. 24-hour cycles continued through the September 26 cycle, for atotal of 22 cycles. 48-hour cycles ran from the beginning of the last 24-hour cycleuntil October 18 (11 cycles).Figure 11 shows pH values at the 0, 4 and 22-hour points during the 24-hourcycles. All values are averages of the duplicate columns. The two standardcolumns appear to be at equilibrium. The readings for the two acid-added columnswere still dropping at the first dates shown, but this change appears to be slowing atthe final dates. It had been desired to achieve a pH reduction of about 0.75 - 1 pHunit compared to the 22-hour point of nonadjusted columns and this was met usingthis level of acid addition. The agreement between duplicate columns was verygood for the zero and 22-hour points. It is understandable that the four-hour points52had more variation, as pH levels are changing rapidly during the early hours oftreatment.Figure 12 shows COD removal percentages at the 0, 4 and 22-hour pointsduring 24-hour cycles of run B. All values are averages of the duplicate columns.Standard columns demonstrate slightly superior COD removals, particularlynoticeable for the four-hour points. Even early in the run, before the pH after the 4-hour point might have dropped too far, the acid-added runs did not havesignificantly superior COD reductions.Figure 13 illustrates COD removal percentages at the three time points during24-hour cycles, for supernatant given the additional three hours settling. All valuesare averages of the duplicate columns. Acid-added columns have dramaticallyhigher removals for the zero-hour points, but much of this improvement over thestandard columns is lost by the four-hour point. By the 22-hour point the twotreatments are not significantly different.The pH values resulting immediately after the addition of acid appeared to reachequilibrium values of approximately 5.28 and 5.20 for columns 4 and 5 bySeptember 24. This stabilization at the lowest pH values coincided with the smallbut consistent drop in COD removals for the one-hour settled samples near the endof the run. However, there was little corresponding drop in the COD removals in thesupernatant samples, so the activity of the biomass had not been affected, only thesettleability of suspended solids. As the SVIs were unaffected, it was primarily theinfluent suspended solids that decreased in settling speed rather than the flocs. Itis possible that the temporary low pH conditions existing after the four-hour pointsnear the end of the run somehow caused a poorer adsorption of organic matter ontothe flocs.hese temporarily low pHs were a little lower than intended. If discrete acidaliquots were used for pH adjustment in a full scale system, it would be advisable touse multiple smaller aliquots to obtain less variation in pH levels over the cycle. IfpH limitation was desired for a full-scale application, pH controllers would likely beused, eliminating the problem of either pH extreme. Two pH controllers becameavailable for use in run C, so it was possible to compare run B to results where alow pH was maintained with less fluctuation during the cycle.538.6 -0,,,so 00/ 08.4 -8.2 -8.0 -= 7.8 -o_--I 7.6 -a_u)7.2 -7.06.8 -6.6 -6.4Sep 16 Sep 18^Sep 20 Sep 22 Sep 24^Sep 26AColumns 1 and 6 —0— 0 HR —A— 4 HR —0- 22 HRColumns 4 and 5 —11— 0 HR -A- 4 HR —41— 22 HRFigure 11. pH Values, Run BThis figure shows pH values at the 0, 4 and 22 hour points during 24-hour cycles ofRun B, which ran from September 5 to 27, 1991. All values are averages of theduplicate columns. Columns 1 and 6 were run at standard conditions. Columns 4and 5 were run identically except that 50 ml of 2 N sulphuric acid were added intoeach immediately after the 4 hour samples were taken. The standard columnsappear to be at equilibrium. The readings for the acid-added columns are stilldropping at the first dates shown, but appear to be stabilizing at the final dates. Ithad been desired to achieve a pH reduction of about 0.75 - 1 unit compared to the22 hour point of nonadjusted columns and this was met using this level of acidaddition.54g80cpSep 16^Sep 18^Sep 20 Sep 22 Sep 24 Sep 26STANDARD COLUNNS -A- 0 hr —0— 4 hr —0— 22 hrACID ADDED COLUMNS -A- 0 hr —II— 4 hr --s— 22 hrFigure 12. COD Removal (1-Hour Settled Samples), Run BThis figure shows COD removal percentages at the 0, 4 and 22 hour points during24-hour cycles of Run B, which ran from September 5 to 27, 1991. All values areaverages of the duplicate columns. Columns 1 and 6 were run at standardconditions and had no pH adjustment. Columns 4 and 5 were run identically exceptthat 50 ml of 2 N sulphuric acid were added into each immediately after the 4-hoursamples were taken. The standard columns generally have slightly higher CODremovals. The largest difference occurs at the 22-hour point for the last few cycles,where the reduction in the acid-added columns appears to be reaching a newequilibrium.55Sep 16^Sep 18^Sep 20 Sep 22^Sep 24^Sep 26STANDARD COLUMNS —a-0 hr —0-4 hr —0-22 hrACID ADDED COLUMNS -A- 0 hr —0— 4 hr —11— 22 hrFigure 13. COD Removal (4-Hour Settled Samples), Run BThis figure shows COD removal percentages at the 0, 4 and 22-hour points during24-hour cycles of Run B, which ran from September 5 to 27, 1991. COD valuesshown are for supernatant from samples given 4 hours settling. All values areaverages of the duplicate columns. Columns 1 and 6 were run at standardconditions and had no pH adjustment. Columns 4 and 5 were run identically exceptthat 50 ml of 2 N sulphuric acid were added into each immediately after the 4 hoursamples were taken. The difference between the acid-added and standard columnswere small except for the 0-hour point where COD removals in the acid-addedcolumns were nearly as great as in the 4-hour samples.56Shown in figure 14 are the average percentage COD removals for the 0, 4 and22-hour time points of the 24-hour cycles and the 46-hour point of the 48-hourcycles of Run B for the two standard conditions columns. COD removals for bothone-hour settled samples and supernatant from additional settling are graphed.The values are averages of the last three cycles of each part of the run. The errorbars are much smaller on supernatant as would be expected, as the only one-hoursettled samples can have significant variation in the amount of biomass stillsuspended. Removals at the end of 48-hour cycles are only moderately higher thanat the end of 24-hour cycles.Percentage COD removals for both one-hour settled and additional-settledsamples are shown in figure 15 for the three time points. All values shown areaverages of duplicate columns. The averages from the standard columns are onthe left of each pair, the acid-added columns to the right. The numbers used areaverages of the last three 24-hour cycles. The standard conditions results areconsistently higher than the acid-added removals for the one-hour settled samples.The acid-added columns had the advantage however when the samples were giventhe additional settling, resulting in dramatically higher removals for the zero-hoursamples. The suspended material in the wastewater is quite effectively settledduring the additional three hours clarification after being mixed with the biomassfrom the end of the previous acid-added cycle. However, most of this improvementover the standard columns was lost by the 22-hour point.This run indicates that pH was not limiting near the end of the cycles in thestandard columns, as the acid-added columns had only slightly superiorsupernatant COD removals at the 22-hour point. In fact, during the latter part ofeach cycle when the pH was high, was when the nonadjusted columns made upsome of the large deficit in removal evident at the beginning of each cycle. ThoughpH is not thought to have been limiting in the nonadjusted columns, the addition ofacid did confer an advantage for the removal of COD in the supernatant samples ofthe early time points, particularly the zero-hour point. However, because thestandard columns had almost as good final CODs for the extended settling samples,and did have slightly better results for the more typical settling period, the additionof the acid is not considered to have been an advantage in this run.574^22^46TIME POINT (hr)1-HOUR SETTLING • 4-HOUR SETTLINGFigure 14. COD Removals in 1-Hour and 4-Hour Settled Samples, Run BShown are the average percentage COD removals for the 0, 4 and 22 hour timepoints of the 24-hour cycles and the 46 hour point of the 48-hour cycles of Run B forthe two standard conditions columns. The values are averages of the last threecycles of each part of the run. Error bars show 90% confidence intervals foragreement between cycles. Error bars are much smaller on the supernatant fromextended settling, as would be expected because the samples settled for only onehour can have significant variation in the amount of biomass still suspended.Removals at the end of 48-hour cycles are only moderately higher than at the end of24-hour cycles.5850 —40 _30 —8-0c:*D 20 —10 —600^4^22TIME POINT (hr)1—HOUR SETTLING ^ 4—HOUR SETTLINGFigure 15. Average COD Removals in 1-Hour and 4-Hour Settled Samples forStandard Conditions Columns and Acid-Added Columns, Run BCOD removals for both 1-hour and 4-hour settled samples are shown for threedifferent time points of run B. Averages of the duplicate columns are used, with thestandard columns shown on the left in each pair, the acid-added columns to theright. The numbers used are averages of the last 3 24-hour cycles. Error barsrepresent 90% confidence intervals for the cycle-to-cycle variation. The standardconditions results are consistently at least slightly higher than the acid-addedremovals, with the exception being the result for the zero-hour point in thesupernatant from extended settling.59BOD5 reductions at the final time points at the end of the 24-hour cycles and 48-hour cycles are listed in table 9. These removals are slightly lower than the resultsfrom run A (which had a lower BOD5 loading). There is a greater differencebetween the standard and acid-added columns for the one-hour settled samplesthan four-hour settled samples, which was also the case for the CODmeasurements. The BOD5 of the untreated wastewater averaged 3190 mg/I.Table 9. BOD5 Percentage Removals for Run BDate Sample hr Column 1-hr settling% BOD5 Removed4-hr settling% BOD5 RemovedSep-26 22 standard 70.23 89.65Sep-26 22 acid-added 67.04 88.11Oct-16 46 standard 76.58 94.62Wastewater B had a total solids concentration of 8,625 mg/I, TSS of 950 mg/Iand VSS of 930 mg/I. This TSS is near the bottom of the range of 900-2000 mg/Ispecified by the Quesnel mill technicians for combined whitewater and wastewaterfrom that mill, which is probably because the measurement of wastewater B doesnot include the fraction of solids that settled out during shipping and storage.However, this is higher than the concentration in the wastewater entering theQuesnel mill's biological treatment system, which has been clarified in a dissolvedair flotation system and has a TSS of about 150-300 mg/I.The treated wastewater from the September 24, 24-hour cycle had a TSS of 500mg/I (+/-16 mg/I at 90% Cl.) and a VSS of 480 mg/I (both averages of foursamples). This just meets the TSS regulation in effect for Quesnel River Pulpwhich, based on production and effluent flow rate, works out to a daily maximum of837 mg/I and a maximum of 502 mg/I for the monthly average. TSS regulations willlikely become even stricter in the near future [personal communication, Vernon E.McAllen of H.A. Simons Ltd. 1993]. The Quesnel River Pulp final effluent has anaverage TSS of 480 mg/I.During the 24-hour cycles the standard columns had significantly more foam atthe end of aeration periods (7-10 cm) than the acid-added columns (2-4 cm).Comparing foam heights between duplicate columns, showed that the columnoperating at slightly higher pH also had slightly more foam. The foam on the acid-added columns also broke up within three seconds after the aeration stopped, whilein the standard columns the foam lingered for one to two minutes. The acid addition60had a large impact on foaming, but the SVIs of the acid-added columns remainedsimilar to those in the standard columns.Mixed liquor total solids, total suspended solids, volatile suspended solids andsludge volume index for run B are shown in figure 16. All values are averages ofthe duplicate columns at standard conditions. The values for September 18 to 26are from some final 24-hour cycles; later dates show values from 48-hour cyclesnear the end of the run. The SVIs are steady at between 54 and 60 ml/g for the 24-hour cycles, and then clearly deteriorate during the 48-hour cycles.Values from the 24-hour cycles are relatively stable by this stage of the run forall sludge measurements. The solids wasted per cycle at the end of the run of 48-hour cycles were still greater than the equilibrium values expected for the very loworganic loading. The concentrations in the final 48-hour cycles are approximately73% of the 24-hour cycle values, which is high compared to run A. At the end of therun the solids concentrations are still declining from sludge built up during the 24-hour cycles, and the SVIs are still deteriorating.Shown in figure 17 are the mixed liquor total solids, total suspended solids,volatile suspended solids and sludge volume index for the 24-hour cycles of run B,comparing the standard and acid-added columns. The acid-added columns haveslightly lower solids concentrations, but SVIs are similar. Agreement was highbetween the two standard columns.Resin acids and fatty acids were determined by GC for the influent and a 24-hour cycle treated wastewater sample. The treated sample was the one-hoursettled sample of the 22-hour point in standard column 1, from the September 26cycle. The results are shown in table 10. High resin acid concentrations wereexpected for this batch of wastewater as its COD and BOD5 were the highest of allthe batches of wastewater used. The resin acids present in the highestconcentrations are dehydroabietic and abietic acid, consistent with the resin acidpercentages for the QRP wastewater in a recent study [McCarthy 1991]. The 41.9%reduction in total resin acids is low compared to that of other aerobic treatmentsystems mentioned in the literature review, but cannot be considered as typical forthe system without the analysis of further samples.617000600050000) 4000o 30000(I) 2000100009080 E7060 ?-W D4030Qcoe9^^ ^ coe9 C^C^d^CNc^N91^q9;^9'^9,v^sz.v tcr^king M_TS^IVLTSS I ovussFigure 16. Solids Concentrations and Sludge Volume Index for Standard Columns,Run BMixed liquor total solids, total suspended solids, volatile suspended solids andsludge volume index are shown. All values are averages of the duplicate columnsat standard conditions. The values for September 18 to 26 are from the 24-hourcycles which started September 5, 1991. Later dates show values from the 48-hourcycles which started September 26. Values from the 24-hour cycles are relativelystable by this stage of the run for all sludge measurements. Though the solidsconcentrations of the 48-hour cycles are only slowly decreasing during the datesshown, the SVIs are still deteriorating. The final 48-hour cycle MLVSS is 73% of theaverage 24-hour cycle values, and is probably still above equilibrium levels.62701339000^ 65 —E80005527000^ 50456000 a40 D_Jcn5000(/)0 4000co STANDARD CONDITIONS ACID ADDEDI^I IVLTS^M_'TSS^MSFigure 17. Solids Concentrations and SVIs for Standard and Acid-Added Columns,Run BThis figure illustrates the mixed liquor total solids, total suspended solids, volatilesuspended solids and sludge volume index for the 24-hour cycles of run B,comparing the standard and acid-added columns. Acid-added columns consistentlyhave slightly higher SVIs, and slightly lower solids concentrations. Solidsmeasurements for both treatments appear to be at equilibrium.60a63Table 10. Resin Acids and Fatty Acids in Untreated Wastewater and 22-HourSample, Run BUntreated 22-Hour Sample % ReducedResin Acid mg/1 mg/1 %Dehydroabietic 95.82 66.90 30.2Abietic 67.77 36.48 46.2Levopimaric & Palustric 62.70 20.60 67.1Isopimaric 54.01 40.33 25.3Pimaric 41.51 28.97 30.2Neoabietic 21.87 6.25 71.4Sandaracopimaric 4.13 2.67 35.3Total resin acids 347.81 202.20 41.9Fatty acid mg/I mg/1 %Linoleic 80.00 11.56 85.6Oleic 58.41 0.00 100.0Pinolenic 24.46 0.00 100.0Stearic 12.08 8.14 32.6Palmitic 10.19 0.49 95.2Palmitoleic 1.78 0.00 100.0Myristic 1.52 0.91 40.6Lignoceric 1.14 1.41 -23.7Lauric 1.06 0.33 68.6Caproic 0.55 0.00 100.0Total fatty acids 191.19 22.83 88.164Run C Treatment Results Run C was carried out to investigate if lower, controlled pH conditions wouldcause any improvement in COD removal or sludge settleability. A column was alsorun using an on-off DO controller to limit the aeration to maintaining adequate DOlevels, to assess the effect of less mixing. The air flow rate used for this columnwas set at about 2 l/min, so that the column would not take much longer to come upto acceptable DO levels than the other columns. This flow rate was also chosen sothat the problems encountered from the even lowPr gas flow rates of the oxygen-activation columns in run B could be decreased. In addition, one column was runwith a lower fraction of sludge wasting, to study the effects of a longer SRT onsludge concentrations and COD removal.In run C all columns were run at standard conditions of 20-day SRI, 2.5 l/min airflow rate and uncontrolled pH except as specified. For the 24-hour cycles, Column1 was controlled at a pH of 6.5. Column 2 was controlled at a DO of 3 mg/I.Column 3 was run at an SRI of 30 days. Column 4 was controlled at a pH of 7.5.Columns 5 and 6 are a duplicate at standard conditions. For the 48-hour cycles,columns 5 and 6 were still at standard conditions, column 3 was continued at 30-day SRTs, and column 1 was continued but without pH control. As with the pureoxygen-activated columns of run B, it was observed that in the 3 mg/I DO columnthe flocs were fluffier, and the lower degree of mixing was again easily visible.Run C 24-hour cycles started November 14, 1991 using another batch ofwastewater, switching to wastewater C on November 20. The 24-hour cycles endedafter the December 5 cycle, for a total of 22 cycles with the last 16 on wastewater C.The 48-hour cycles began December 5 and ended with the December 19 cycle(eight cycles).Results from the two columns run on four-day cycles at the end of run C are notincluded in the various figures in this section. This is because these were onlymeasurements of transient conditions and it would be misleading to include themnext to data from near-equilibrium conditions. The four-day cycles provideinformation on what might happen during a short period of low organic loading, suchas might happen during a production decrease, a work stoppage, or a majorequipment breakdown on one of the pulping lines.Figure 18 shows pH values at the 22-hour sample point during the 24-hourcycles. The 3 mg/I DO column had significantly lower pH levels than the other threecolumns without pH control. The differences between the standard columns and the65longer SRT column, though consistent, are not larger than between-columnvariations demonstrated in the previous runs. pHs in all the columns in the 24-hourcycles appear to have reached equilibrium.The fluctuations shown for the columns with controlled pH are primarily due tothe increase in pH that occurred once the samples were removed from the columns.This change was faster the lower the sample pH was. In all runs, this change in thesample pH was minimized by measuring the pHs immediately after the sampleswere removed from the reactors, and measuring the different samples in as rapidsuccession as possible.The reduction-oxidation (Redox) potential measured during settling of column 6at the end of the December 4 cycle is shown in the following table (11). Asdissolved oxygen had always been zero by the end of the settling periods, it wasinteresting to find out how low the Redox dropped. Though the mixed liquorremained aerobic for most of the settling period, it was well into the anoxic region bythe end of the hour of settling. At the end of the 30-minute decanting period (at 1.5hours after aeration halted) immediately before refilling with wastewater, the sludgewas quickly mixed manually and the Redox potential measured to be -209 mV.Table 11. Reduction-Oxidation Potential During Settling PeriodMinutes into settling 0 15 25 40 50 60Redox Potential, mV 42 19 14 8 -10 -45Figure 19 shows COD removal percentages of cycles late in each segment ofrun C. Before the axis break are COD removals at the 22 hour sample point during24-hour cycles. After the axis break are shown COD removal percentages at the46-hour sample point during 48-hour cycles. The greatest COD removal wasachieved in the 3 mg/I DO column. The longer SRT and pH 7.5 columns are next inCOD removal, with the standard columns consistently below them. The pH 6.5column typically had the poorest COD removal.669.08.5 -6.5 -6.0Nov 25^Nov 27^Nov 29^Dec 1^Dec 3^Dec 5COLUMNS: —0— 1 —0-2 -----3 —v-4 —O--5 —+-6Figure 18. pH Values, Run CShown above are pH values at the 22 hour sample point during 24-hour cycles ofRun C, which ran from November 14 to December 6, 1991. All columns were run atstandard conditions of 20-day SRI, 2.5 l/min air flow rate and uncontrolled pHexcept as specified. Column 1 was controlled at a pH of 6.5. Column 2 wascontrolled at a DO of 3 mg/I. Column 3 was run at an SRI of 30 days. Column 4was controlled at a pH of 7.5. Columns 5 and 6 are a duplicate at standardconditions. The 3 mg/I DO column had significantly lower pH levels than the otherthree columns without pH control. All columns without pH control appear to be atpH equilibrium.67000^_o0 A0 0+-+-+40 -g300 -20 -10 -50 ^/1^Nov 25^Nov 29^Dec 3^Dec 10 Dec 16COLUNN: —0-- 1 —0-- 2 -A- 3 —v— 4 —0— 5 —+— 6Figure 19. COD Removal (1-Hour Settled Samples), Run CBefore the axis break are shown COD removal percentages at the 22-hour pointduring 24-hour cycles of Run C, which ran from November 14 to December 6, 1991.After the axis break are removals at 46 hours during 48-hour cycles, which ran fromthe last 24-hour cycle to December 21. Columns were run at standard conditionsexcept as follows. For the 24-hour cycles, Column #1: pH 6.5; #2: 3 mg/I DO; # 3:30-day SRT; # 4: pH 7.5. For the 48-hour cycles, columns #5 and 6 were still atstandard conditions, #3 was continued at 30-day SRI, and #1 was continued butwithout pH control. In the 24-hour cycles the 3 mg/I DO column had the bestreduction. In 48-hour cycles, the previously pH 6.5 column was at similar levels tothe longer SRT column but appeared to be dropping towards the standard columns.68For the 48-hour cycles, the longer SRT column was still marginally moreeffective than the standard columns. The column which had been previouslycontrolled at pH 6.5 was at similar levels to the longer SRI column, but appears tobe dropping towards the results of the standard columns. This initial improvementin its COD removal is consistent with the similarity between the longer SRI and pH7.5 columns in the 24-hour cycles. This might be expected while the previously pH6.5 column temporarily still has its average pH closer to 7.5 than to the pHs of thestandard columns.For the supernatant from samples that were given the additional three hours ofsettling, COD removal percentages of the later cycles are shown in figure 20.Before the axis break are shown COD removal percentages at the 22-hour samplepoint during 24-hour cycles. After the axis break are shown COD removalpercentages at the 46 hour sample point during 48-hour cycles. The COD removalsappear to be fairly stable at the end of the run of 24-hour cycles, though with morevariation than the previous two runs.For the 24-hour cycles, the pH 6.5 column had marginally higher COD removals,followed by the pH 7.5 column and the longer SRI column which had similarremovals. The other three columns were roughly similar to each other with slightlylower removals. There was less difference between the COD removals in thesesupernatant samples than in the samples from the shorter settling period shown inthe previous graph. At the end of the 48-hour cycles, the 30-day SRI column andthe two standard columns were perhaps beginning to stabilize. The previously pH6.5 column still had the highest COD removal (63.1%), but appeared to becontinuing to drop towards the values of the other columns. The higher SRIcolumn again had slightly better removal than the two standard columns.There is a small gap between the COD removals (figure 19) of the standardcondition duplicates, columns 5 and 6. However, looking at the supernatant CODremovals (figure 20), this gap virtually disappears. The variation between thesecolumns may be because a small increase developed in the air bubble size incolumn 5. Even though the difference in bubble size was small, the slight change inmixing could account for the minor difference in settling noticed in the columns anddemonstrated in the difference between their one-hour settled COD values. All theother columns had no discernible difference in bubble size, all being similar tocolumn 6.691^/^70 - 60 -50 -40 -030 -20-10 -Nov 25^Nov 29^Dec 3^Dec 10 Dec 16COLUMN: —0-1 —0— 2 —A— 3 —v— 4 —0-5 —+— 6Figure 20. COD Removal (4-Hour Settled Samples), Run CBefore the axis break are shown COD removals at the 22-hour point during final 24-hour cycles of Run C. After the break are removals at 46 hours during final 48-hourcycles. Values shown are for supernatant samples after 4 hours settling. Allcolumns were run at standard conditions of 20-day SRI, 2.5 I/min air flow rate anduncontrolled pH except as follows. For the 24-hour cycles, Columns #1: pH 6.5; #2:3 mg/I DO; #3: 30-day SRI; #4: pH 7.5. For the 48-hour cycles, columns #5 and 6were still at standard conditions, #3 was continued at 30-day SRI, and # 1 wascontinued but without pH control. The pH 6.5 column had marginally highestremovals. In the 48-hour cycles, the previously pH 6.5 column still had the bestremoval, but was dropping towards the other columns.70Of note is that when samples only experienced one hour of settling, the 3 mg/IDO column which had much lower air flow, had removals slightly higher than any ofthe five other columns. Yet when samples were given an additional three hours ofsettling, this column then yielded some of the lowest COD removal results. Whatappears to have been occurring, both from COD and SVI results and observation ofthe columns, was that the flocs in the lower air flow rate column were far less brokenup than in the other columns.The fluffier sludge caused slightly higher SVIs, and the lower mixing resulted inslightly lower COD removals in the supernatant. However, after only a short periodof settling, COD results were better because more of the biomass settled out of thesupernatant. As the flocs were much less broken up, significantly less biomassexisted in the columns outside the flocs compared to the other columns. As SVIsare important in determining required SBR reactor volume, and the SBR systemwould be operated on the basis of thorough settling, this slight improvement in theCODs for the 3 mg/I DO column for one-hour settled samples would not beconsidered an advantage.Figure 21 shows the average percentage COD removals for the two standardconditions columns, for the 4, 16 and 22 hour points of the 24-hour cycles and the46-hour point of the 48-hour cycles. COD removals for one-hour and four-hoursettled samples are compared. The values are an average of the last three cyclesof each part of the run. There is a deterioration in removals in the 48-hour cycles,particularly in the CODS of samples settled for only one hour, indicating that inaddition to not achieving better treatment, sludge settleability has also fallen.Percentage COD removals for both one-hour settled and additional-settledsamples are shown in figure 22 for three different time points for the six columns ofrun C. The numbers used are again averages of the last three 24-hour cycles.Even though the 6.5 pH column settled very well, at four and 22 hours it had lowerCOD removals after the one-hour settling period than the other columns. This waslikely due to its significantly higher biomass concentrations resulting in morebiomass suspended in the partially-clarified wastewater. However, at all three time-points the 6.5 pH column had the best COD removal in the supernatant fromadditional settling. Though the four-hour settled COD removal of the 3 mg/I DOcolumn was lowest by 22 hours, it had the best one-hour settled COD removals atfour and 22 hours, likely due to its less broken up sludge resulting in lesssuspended biomass after the shorter settling period. Limitation of mixing velocities71has been shown in other research to improve settleability and effluent suspendedsolids [Gaul 1991].BOD5 values for samples from the final 24-hour and 48-hour cycles and the secondto last 96-hour cycle are shown in table 12. The initial BOD5 of the wastewater was2600 mg/I. All the 22-hour effluents after one hour of settling had at least 72%removal, or less than 725 mg/I BOD5. All the 22-hour samples after extendedsettling had at least 90% removal, or BOD5s of less than 257 mg/I.Table 12. BOD5 Percentage Removal Results for Run CDate Sample hr Column 1-hr settle% BOD5 Removal4-hr settle%B0D5 RemovalDec-05 4 std (5) 62.55 78.74Dec-05 4 std (6) 64.04 77.73Dec-05 16 std (5) 67.80 86.64Dec-05 16 std (6) 69.96 85.96Dec-05 22 pH 6.5 72.12 94.45Dec-05 22 3 mg/I DO 77.09 90.12Dec-05 22 30-d SRT 74.44 92.40Dec-05 22 pH 7.5 75.00 93.64Dec-05 22 std (5) 72.91 90.77Dec-05 22 std (6) 73.67 91.31Dec-19 46 prey pH 6.5 80.63 95.79Dec-19 46 30-d SRT 81.91 93.03Dec-19 46 std (5) 80.65 93.38Dec-19 46 std (6) 79.28 91.31Dec-31 94 std (5) 82.24 95.73Dec-31 94 std (6) 83.32 97.5472430 -80° 2010 -60 -50 -16^22^46TINE POINT (hr)1-HOUR SETTLING^4-HOUR SETTLINGFigure 21. Average COD Removals in 1-Hour and 4-Hour Settled Samples forStandard Conditions Columns, Run CThis figure shows the average percentage COD removals for the two standardconditions columns of run C, for the 4, 16 and 22 hour points of the 24-hour cyclesand the 46 hour point of the 48 hour cycles. The values are an average of the lastthree cycles of each part of the run. 90% confidence intervals are shown foragreement between cycles. There is a deterioration in removals in the 48 hourcycles, particularly in the one-hour settled CODs, indicating that in addition to notachieving better treatment, settleability of suspended solids has also fallen.7370 —60 —5048 30 —c:*320 —10 —4^16^22TINE POINT (hr)•71 1—HOUR SETTLING I I 4—HOUR SETTLINGFigure 22. Average COD Removals in 1-Hour and 4-Hour Settled Samples, Run CPercentage COD removals for regular and additional-settled samples are shown forrun C, going from column 1 to 6, left to right. The values used are averages of thelast three 24-hour cycles. All columns were run at standard conditions except asspecified. Columns 1 and 4 were controlled at pH 6.5 and 7.5 respectively. Column2 was controlled at 3 mg/I DO. Column 3 had a 30-day SRT. Even though the 6.5pH column (1) settled very well, it had lower 1-hour settled COD removals than theothers at 4 and 22 hours. However, the 6.5 pH column had the best COD removalat all three points in the supernatant from additional settling. The 3 mg/I DO column(2) had the best regular CODs at 4 and 22 hours, but did not have superior 4-hoursettled COD removals.74The following observations on foam depths uses descriptions similar to thoseemployed in a study by Blackall et a/. [1991a]. In the 24-hour cycles it wasobserved that the mixed liquor in the pH 6.5 column reacted to aeration as did thepure Quesnel wastewater during aeration tests. The bubbles had no stability so nofoam layer formed. The pH 7.5 column had 1 to 2.5 cm of foam with fragile bubbles,and insufficient stability to form films. The foam collapsed within a second or two ofaeration being stopped. The standard columns, 3 mg/I DO column and 30-day SRTcolumn had foam with some stability, 5-10 cm in height (3 mg/I DO column thelowest, standard column 5 the most). The foams lasted up to two minutes afteraeration ceased.In the latter part of the 48-hour cycles, standard column 5 still had the greatestfoam height (10 cm); standard column 6 and the 30-day SRT column had foamdepths of 7-8 cm. The pH 6.5 column started the 48-hour cycles with virtually nofoam, but by the end of the run had 3-4 cm of foam.Figure 23 shows mixed liquor total solids, total suspended solids, volatilesuspended solids and sludge volume index for dates near the end of the 24-hourcycles portion of run C. The sludge concentrations appear to be stabilizing for mostof the columns by the last dates shown. The pH 6.5 column has significantly highersludge concentrations and lower SVIs. The 30-day SRT and pH 7.5 columns haveslightly higher sludge concentrations than the lower DO and standard columns.The differences between the lower DO and standard columns for all sludgemeasurements are not significant when compared to the variation exhibited betweenthe replicate columns at standard conditions. Excluding the pH 6.5 column, SVIsare not significantly different among the columns. During the run, pH-controlledcolumns had appeared to have denser sludge packing by the end of the hour ofsettling (SVIs are measured at 30 minutes) than the other columns, but with the 6.5pH column settling more rapidly and compactly than the 7.5 pH column. In the 48-hour cycles, the 30-day SRT column had the most densely packed, granular-appearing sludge. The final sludge measurements in the 48-hour cycles showedthat the MLVSS had dropped by 9% (30-day SRT column) to 22% (standard column5) from the concentrations during the 24-hour cycles.751000022-Nov 24-Nov 26-Nov 29-Nov 01-Dec 03-Dec90807060 D5040 0600050004000cy)u) 300002000M_TS L2A M_TSS^ryLvssFigure 23. Solids Concentrations and Sludge Volume Index for Run CMixed liquor total solids, total suspended solids, volatile suspended solids and SVIsare shown for dates near the end of the 24-hour cycles of Run C, which ran fromNovember 14 to December 6, 1991. All columns were run at standard conditions of20-day SRT, 2.5 I/min air flow rate and uncontrolled pH except as specified.Columns 1 and 4 were controlled at pH 6.5 and 7.5 respectively. Column 2 wascontrolled at 3 mg/I DO. Column 3 was run at 30-day SRT. Sludge concentrationsappear to be stabilizing for most columns. Column 1 had significantly higherconcentrations and lower SVIs. Columns 3 and 4 had marginally higher solids than2, 5 and 6. SVIs are not significantly different among columns 2 through 6.76The fact that the pH 6.5 column had only slightly better supernatant CODremovals than the other columns while its solids concentrations were significantlyincreasing, means that increased digestion of the wastewater cannot alone accountfor the higher sludge concentrations. It appears that the sludge underwent lessdestruction during the later hours of each cycle. This is also supported by theobservation that there was a greater decrease in the supernatant CODs between 16and 22 hours for this column than the other columns. Whereas some of the othercolumns had little or no further improvement in the COD removals in supernatantsamples (four-hour settled samples), the supernatant COD removal for the pH 6.5column still improved between these time points. In the other columns, though asmall amount of wastewater digestion is likely still occurring in addition toendogenous respiration, the breakdown of some of the biomass may release a littlesoluble organic material back into the supernatant. This was demonstrated in a fewsamples where the overall COD did drop slightly between 16 and 22-hour points,but the supernatant COD slightly increased.Zone settling rates were measured at the end of the December 3 24-hour cycle.These are shown in Table 13. The sizable differences between the settling rates ofcolumns 2 through 6 are not echoed by the SVIs, which showed little variationbetween these columns.Table 13. Zone Settling Rates for a 24-hour Cycle of Run CColumn Zone Settling Rate, cm/min#1 pH 6.5 3.81#2 3 mg/I DO 1.83#3 30-day SRT 2.51#4 pH 7.5 3.05#5 standard 2.67#6 standard 2.29The 96-hour cycles yielded final COD removals that were a little poorer than inthe 48-hour cycles for column 5, but a little higher in column 6. The solidsconcentrations continued to drop. The SVIs were clearly deteriorating, but by theend of the five cycles were still settling well compared to sludge volumes occurringin some AS systems for pulpmill wastewaters [Jeffries 1989]. This indicated that thesystem could survive a short-term low loading situation, without exacerbating the77sludge reduction by decanting large amounts of biomass with the treatedwastewater.Microtox results presented in Table 14 show that the wastewater has hightoxicity which, though reduced by two orders of magnitude, was not fully detoxifiedduring treatment. This wastewater batch was particularly toxic. Later batches of thesame type of Quesnel River pulp mill effluent used in other research projects had15-minute EC50s that ranged from about 0.3-3%. For these Microtox tests the "r"values, giving the correlation coefficient of the line estimated from serial dilutions ofeach sample, ranged between 0.985 and 0.997.Table 14. 15-minute Microtox EC50 for Samples from Run CDate Sample Column EC5n, % 95% C.I.91-12 Influent 0.22 0.16-0.3112-05 22 hour pH 6.5 15 11.8-19.112-05 22 hour standard 21 16.5-26.812-19 46 hour 30-d SRT 32 26.1-39.212-19 46 hour standard 25 20.3-30.8The two 48-hour cycle samples gave a higher EC50 for the 30-day SRT columnthan for column 6 at standard conditions, consistent with the fact that the 30-daySRT column also had higher COD reduction. For the 24-hour cycles, the differencebetween the EC50s for the pH 6.5 and standard column is not reflected in the CODs.As rainbow trout and daphnia bioassays on the wastewater must have LC50s of100% to meet the effluent regulations, the examination of toxicity reduction usingthese bioassays would be a critical part of further research on this system.78Comparison of Runs A, B and C Measurements of four-hour settled CODs, solids concentrations, SVIs and pHvalues were very stable for the last few 24-hour cycles of each run. The one-hoursettled CODs showed a little more variability. This high degree of between-cyclesagreement would not be expected in pilot-plant or full-scale applications. In normalpulpmill operation the BOD and COD concentrations in the untreated wastewatercan change greatly from one day to the next, as the type of pulp being produced orthe furnish used changes.A summary of pH at various sample times for runs A, B and C is shown in Figure24. All time points shown except 46 hours are for samples taken during 24-hourcycles. Points plotted use an average of the last three cycles of the 24-hour cyclesor 48-hour cycles segment of each run, with error bars showing the agreementbetween the three cycles. Run A points are an average of three columns; B and Cpoints are each an average of two columns. All data shown in this figure is from thecolumns at standard conditions (i.e. uncontrolled pH, 2.5 I/min air flow and 20-daySRT). In the 24-hour cycles, run A had the highest pHs except at the 16-hour point.The pH increase with treatment time was significant in all three runs, particularlyfor the early hours of treatment. For runs B and C, pH at the end of the 48-hourcycles was consistently higher than pH at the end of the 24-hour cycles. Theuncontrolled pH columns typically had a pH of at least 8.5 by the end of 22 hoursaeration, 8.5-8.9 by 46 hours aeration, and 9.0 by 94 hours. With all pH-unadjustedruns the relationship held that for a given batch of wastewater the columns whichdeveloped the highest pHs had the highest overall COD removals.The colour of all columns except pH-controlled columns darkened greatly duringtreatment. Colour was found to be very pH dependent, with the samples around 6.5pH from the early hours of treatment in uncontrolled columns not being discerniblein colour from samples from the end of treatment from the 6.5 pH column (thesamples were different in turbidity). Colour of the acid-added columns of run B atthe end of cycles, was similarly comparable to the colour of the standard columnsearlier in each cycle. It was also observed qualitatively that a significant amount ofthe colour increase in the samples from the uncontrolled-pH columns could bereversed by neutralizing the pH. As darkening of the effluent is a common problemin the aerobic treatment of pulpmill wastewater, the colour-pH relationship in thisSBR system merits further investigation.791^/^9.0 -t8.5 -7.5 - /7.0 -1 I^I^I^I^I I^'^I^'^I^'  /^ i4^8^12^16^20^24 46TREATMENT TIME (hr)—0— RUN A —0— RUN B --A--- RUN CFigure 24. pH Summary for Runs A, B and CA summary of pH at various sample times for Runs A, B and C is shown. All timepoints shown except 46 hours are for samples taken during 24-hour cycles. Pointsplotted use an average of the last three cycles of the 24-hour cycles or 48-hourcycles segment of each run. Run A points are an average of three columns; B andC points are each an average of two columns. Error bars (for variation betweencycles) depict a 90% confidence interval. All data shown in this figure is fromcolumns at standard conditions, i.e. uncontrolled pH, 2.5 Umin air flow and 20-daySRI. pH increase with treatment time was significant in all three runs, particularlyfor the early hours of treatment. For runs B and C, pH at the end of the 46 hourcycles was higher than pH at the end of the 24 cycles.80Percentage COD removals from all the time points of the 24-hour cycles and the46-hour time point of the 48 hour cycles are illustrated by figure 25. The valuesshown are averages of the three standard conditions columns of run A, the two ofrun B and the two of run C. Both COD removals from one-hour settled samples andsupernatant from additional settling are charted. Each value is an average of thelast three cycles of the 24-hour cycles or, in the case of the 46-hour point, the lastthree 48-hour cycles. Run A shows the best COD removal, run B the poorest. The48-hour cycle removals were generally slightly lower than the end of the 24-hourcycles. The relationship between different time points is quite consistent betweenruns.In all three runs, the most rapid COD removal occurred in the first four hours.Very little, if any, additional COD removal was achieved by running the system on48-hour cycles rather than 24-hour cycles. It was clear from the COD data(especially obvious from comparing the time points of the 48-hour cycles to the 24-hour cycles in run A) that the use of a 48-hour cycle greatly decreased removalefficiency, treatment was greatly slowed and took longer than 22 hours of aeratedtreatment to meet what was achieved in the 24-hour cycles by 16 hours aeration.CODs of the supernatant from extended settling showed little reduction betweenthe 16-hour and 22-hour points. Therefore, even though some one-hour settledCODs still showed significant improvement between the 16 and 22 hour points, ifthe system is run with adequate clarification, there is no benefit to having a longerreaction period than 16 hours. The amount of sludge digested during the extra sixhours of treatment would not likely be considered sufficient compensation for thegreatly increased operating cost.Fluctuations in COD values between cycles near the end of the runs wereprimarily due to differences in settling characteristics, as much of the fluctuationdisappears if results from the extended settling samples are examined rather thanthose from the one-hour settled samples. Indeed, for most samples where CODswere found to vary significantly from the average, it had been noted in lab recordsthat the column had experienced a drop in settling performance - for example thatthere was an increase in the amount of fine, feathery flocs, which tend not to settle,or that there was sludge floating on the wastewater surface, some of whichoccasionally got mixed into the supernatant as the sample was being taken.8150 —40—c23 20—8030—60—10— 0 ^ //I^0 5^10^15^20^45TINE POINT (hr)1—HOUR SETTLING^—0— RUN A —o— RUN B -A- RUN C4—HOUR SE I I LING^—11— RUN A —40— RUN B -A- RUN CFigure 25. Comparison of Average COD Removals in 1-Hour and 4-Hour SettledSamples for the Standard Conditions Columns of Runs A, B and CPercentage COD removals from all the time points of the 24-hour cycles and the 46-hour time point of the 48 hour cycles are illustrated. The values shown areaverages of the three standard conditions columns of run A, the two of run B andthe two of run C. Each value is an average of the last three cycles of the 24 hourcycles or, in the case of the 46-hour point, the last three 48-hour cycles. 90%confidence intervals show the agreement between cycles.82Both of these situations had little impact on samples from additional settling asthere was virtually no suspended matter in the supernatant. Because most of thecycle-to-cycle variations in the one-hour settled samples appear to be the result offluctuations in settling characteristics, with the average sample having experiencedvery good settling, most COD values lower than the median are distributed over afar smaller range than values higher than the median.Table 15 gives the percentage COD removals from the various scenarios of 24-hour cycles of runs A, B and C for the 4 and 22-hour time points. Run A had thehighest COD removals in one-hour settled samples, matched by the 3 mg/I DOcolumn for the 22-hour point but not the four-hour point. The best COD removals inthe four-hour settled samples occurred in the pH 6.5 column.Table 15. Summary of Percentage COD Removals From 24-hour Cycle Runs1-hour4 hourssamplessettled22 hours4-hour4 hourssamplessettled22 hoursRunA: standard (avg of 3 columns) 33.88 41.25 50.69 57.05B: standard (avg of 2 columns) 19.92 31.70 44.35 53.03B: acid-added (avg of 2 columns) 18.01 28.15 44.48 52.21C: standard (avg of 2 columns) 24.68 35.82 49.74 59.24C:^D.O. limited to 3 mg/I 26.05 41.24 51.82 58.41C: Extended SRT of 30 days 22.11 38.33 48.62 60.93C: pH controlled at 6.5 21.62 33.93 52.43 65.52C: pH controlled at 7.5 23.51 38.95 51.58 61.49The increase in COD removals in the pH 6.5 and 7.5 columns compared to thehigher pH, standard columns is consistent with the research results on CTMPwastewater of Lo et al. summarized in the literature review. In their study the pH 7reactor had a higher COD removal than the pH 8 reactor. They also found thatreactors with HRTs of 3 or 5 days did not have greater COD removals than reactorsat a 2-day HRT. This is similar to the lack of improvement in the 66-hour HRTscompared to the 33-hour HRTs found in this SBR research.COD concentrations are very high immediately after the fresh wastewater ismixed into the columns as the wastewater is only diluted with the three litres ofliquid retained. These initial CODs are far higher than what would occur in the83continuous mixed conditions of even most high-rate AS systems. All runs toleratedthis shock loading, as indicated by the large amount of COD removed in the first fewhours, and the high oxygen consumption in evidence from the slow increase in DOlevels despite high air flows. (During aeration tests with 800 ml/min air flow percolumn, other batches of this wastewater saturated within 20 minutes, while duringtreatment with 2.5 l/min air flow saturation always took well over four hours. Atseveral points during the study, air flow was temporarily halted while oxygen uptakerate measurements were attempted, but the mixing throughout the column wasinadequate without air flow to allow more than localized DO measurements.)Average BOD5s in the untreated wastewater were 2240, 3190 and 2600 mg/I forruns A, B and C respectively. BOD5 reductions in the one-hour settled sampleswere typically 73% at the 22-hour point of 24-hour cycles and 79% at the 46-hourpoint of 48-hour cycles. The BOD5 removals in the supernatant from extendedsettling were approximately 92% and 93% for the final points of the 24-hour and 48-hour cycles respectively. All the four-hour settled samples met the BOD5 regulationfor Quesnel River Pulp which, based on the reference production rate, works out to335 mg/I [personal communication with Quesnel River Pulpmill technicians, 1993].The BOD5 results showed less variation than the COD results. This drop in thespread of values was true for results of columns with different conditions, the 24-hour and 48-hour cycles of the same run, and different runs. This means that undervarious scenarios, the reactors were able to utilize the more easily degradableorganics with similar effectiveness. The larger differences occurred in the ability tobreak down the COD that was not initially present as BOD5, reflected in the greaterfluctuations in COD measurements. This is consistent with the findings of the Lo etal. study [1991], which found that under a wide range of operating conditions,bench-scale aerated chemostats treating CTMP wastewater yielded very similarBOD reductions, though COD removals varied.Control of foaming using measured acid aliquots or pH control were bothsuccessful, but with the pH 6.5 column having the only complete elimination offoam. In all cycles, no foam was present during the first hours of aeration, butconsistently developed by the 16-hour sample points (except for pH 6.5 column),and slowly increased in height as the cycle continued. In the columns without pHcontrol, foam filled most of the 11 cm head space by the time the pH reached 8.5.At the equivalent points in the cycles, the acid-added and pH-controlled columnsshowed little or no foam and also had no lumps of the floating sludge whichoccasionally occurred in the other columns. It was observed that in comparing foam84on different columns within a run that the columns reaching the highest pHs at theend of cycles also consistently had the greatest foam heights.In figure 26 the total solids, total suspended solids, and volatile suspendedsolids are shown for the 24-hour and 48-hour cycles of runs A, B and C. All valuesshown are for columns run at standard conditions, with run A values being averagesof triplicate columns, and runs B and C averages of duplicate columns. An averageof the last three sludge samples for the 24-hour cycles is used, and an average ofthe final two sludge samples used for the 48-hour cycles. The run using wastewaterof the highest concentration yielded the highest sludge concentrations, and the runwith most dilute wastewater, the lowest solids. Run B had slightly greater between-cycle variation in sludge concentrations, which is demonstrated by the larger errorbars.The average mass loadings for the 24-hour cycles of standard conditioncolumns, in terms of kg BOD5 applied/MLVSS.d were 0.38 for run A, 0.48 for B and0.47 for C. These values would be slightly lower if it were possible to determine theaverage MLVSS present during the cycle and use this in the calculation rather thanthe concentration present at the end of cycles (which is assumed to be slightlylower). Run A, which had the lowest mass loading, consistently had the highestCOD removals in the treated effluent decanted from the system (i.e. after one hoursettling).30-minute settled sludge volumes were slightly more variable between cyclesthan the one-hour depths observed, as while the sludge is still noticeably settlingboth variations in compactibility and settling speed impact on the measuredvolumes. By one hour, settling is basically complete and the sludge is only slowlycompacting further, therefore the depths at this point were less variable. Becausethe sludge volume index uses 30-minute settled volumes, these valuessubsequently fluctuate more on both a cycle-to-cycle and between columns basisthan the corresponding solids concentrations and the sludge volumes observed atthe end of the settling periods. The columns which settled most rapidly consistentlyhad the highest fractions of granular-appearing sludge, e.g. the pH 6.5 column.Error bars on the solids concentrations shown in the various solids graphsillustrate both between-column variation and the heterogeneous nature of thesludge. In cases where there were slightly larger chunks of sludge in the column, itwas more difficult with one sample to obtain as accurately representative a sampleas possible in cycles or columns where the sludge flocs were of more uniform,smaller size.857000– 6000 –5000–...--,.-e-jo 4000 -Ecno— 3000–0CO2000–1000 –24 48CYCLE TIME (hr)MLTS^MLTSS ^ MLVSSFigure 26. Solids Concentrations for the Standard Conditions Columns of Runs A,B and CThe total solids, total suspended solids, and volatile suspended solids are shownfor averages of the standard conditions columns from the 24-hour cycles of runs A,B and C, followed by the same measurements from the 48-hour cycles. An averageof the last three sludge samples is used for the 24-hour cycles and an average ofthe last two samples for the 48-hour cycles. Error bars give the 90% confidenceintervals for agreement between the averaged cycles. The run using wastewater ofthe highest concentration yielded the highest sludge concentrations, and the runwith most dilute wastewater, the lowest solids.86Listed below in Table 16 are average mixed liquor volatile suspended solids(MLVSS) values from the three runs. Listed in the fourth column is the quantity ofsludge MLVSS removed from each SBR column per litre of wastewater treated, inmg per day. The fifth column gives the sludge yield - the mg of VSS wasted percycle divided by the mg of total mg of COD removed from the wastewater per cycle.The sixth column also gives sludge yield, but on the basis of BOD5 removed. Thevalues are averages from the final three cycles of solids measurements for the 24-hour cycles, and averages of the last two cycles measured for the 48-hour cycles(as the solids concentrations in the 48-hour cycles were stiii decreasing). Thevalues for standard conditions columns are also averages of the triplicate columnsof run A and the duplicate columns of runs B and C.Table 16. Summary of MLVSS Concentrations and Sludge YieldsRun and Column MLVSS mg/d VSS removed kg VSS/ kg VSS/cycle hr mg/I per I ww treated kg COD kg BOD5A, 24 standard 4115 294 0.119 0.179A, 48 standard 2455 175 0.166 0.203B, 24 standard 4609 329 0.116 0.147B, 24 acid-added 4461 319 0.126 0.151B, 48 standard 3422 244 0.158 0.200C, 24 standard 3892 278 0.113 0.146C, 24 pH 7.5 3872 277 0.104 0.142C, 24 pH 6.5 4455 318 0.137 0.170C, 24 3 mg/I DO 3983 285 0.101 0.142C, 24 30 d SRT 4124 196 0.075 0.102C, 48 standard 3157 226 0.203 0.217The pH 6.5 column had the highest sludge yield for 24-hour cycles. The sludgeyields for the 48-hour cycles are higher than the 24-hour cycles because the sludgeconcentrations are still falling from levels built up during the 24-hour cycles. Typicalsludge yields for AS systems are 0.4 ( range from 0.25 - 0.5) mg VSS / mg COD and0.6 ( range from 0.4-0.8) mg VSS / mg BOD5 [Metcalf 1979]. This SBR processproduced only 1/4 the typical sludge yield on both the COD and BOD5 basis (for the20-day SRT). This indicates that this system was able to incorporate some sludgedigestion into the cycles.87If the fraction of the VSS leaving the system in the supernatant that is generatedbiomass rather than wood solids could be determined, and were added to thecalculation of sludge wasted, this would slightly increase the sludge yield values.However, if the quantity of sludge that is composed of wood solids that have settledout during treatment were determined and the corresponding fraction removed fromthe calculation of the sludge wasted, it would reduce the sludge yield value. Thiswould at least partially counterbalance the increase in the calculated value fromincluding the microbial matter wasted in the supernatant. The settling of much ofthe suspended wood solids that occurred in the SBRs during treatment would likelybe performed by a primary clarifier process in an AS system, so the sludge wastedfrom the AS system would be almost entirely sludge created through wastewaterdigestion.From the data presented in the Rankin et al. study [1992] of conventional ASwastewater treatment at QRP, it is calculated that the 3-day HRT single stage ASsystem with a 15-day SRT, had a sludge yield of 0.5 kg MLVSS/kg BOD5 removed.This further corroborates that the sludge yields from the SBR research system aremuch lower than expected for a continuous-flow system under similar conditions.88Statistical Analysis Using quadruplicate tests performed on the same sample (except for the BOD5between-samples result), the coefficient of variation for the methods used areshown in the following table.Table 17. Standard Deviation and Coefficient of Variation for Analytical MethodsAnalysis Standard Deviation Coefficient of Variation, %COD 97 mg/I 2.7COD settled sample 51 mg/1 1.8BOD5 within 32 mg/I 6.3BOD5 between 38 mg/1 7.2TS 61 mg/I 1.6TSS 52 mg/1 2.2VSS 35 mg/I 1.6Ammonia - N 0.005 mg/I 9.5Nitrate -N 0.05 mg/1 4.3Orthophosphate 0.024 mg/1 3.5The ammonia nitrogen tests were found to have a large coefficient of variationand this was expected as the readings were near the bottom of the range of thatspectrophotometric method.89CHAPTER 4 DESIGN AND SCALE-UP OF THE SBR SYSTEM Because of the fairly long HRT required for effective treatment of thiswastewater, a minimum of three tanks would be recommended for a full-scaleapplication of this process. For only one or two tanks, some aeration during fillwould be required due to the extended fill period. Therefore feast conditions couldnot be maximized before aerobic digesoon began. Also, the shorter fraction of thecycle occupied by the react period requires that more of the fill period be utilized fortreatment as an aerated-fill period. For example, if just two tanks are used for an18-hour cycle, the protocol might be a 9-hour fill with 1 hour aeration every 2 hours(for 4.5 hours total aerated fill), then 6 hours react, 1.5 hours settle and 1.5 hoursdecant. For four tanks providing the same aeration time per 18-hour cycle, a fillperiod of 4.5 hours could be used including two 0.5 hour aerated fill periods,followed by 9.5 hours react, 1.5 hours settle, 1.5 hours decant and 1 hour idle. Alarger number of tanks increases the total time available for react per cycle, andlowers the ratio of fill to decant times. It also increases system flexibility byincreasing time allotted as idle time which acts to increase the safety margin of thedesign, and by allowing greater adaptability in total reactor volume as one or morereactors can be taken in or out of service as needed.The biggest change that would occur in a full-scale version of the research SBRswould be the increase in the fill period duration. This is because the test systemused a very short fill period in which stored wastewater was poured into thereactors. In the full-scale system with four reactors, fill time would equal one thirdthe total react, settle, decant and idle periods of each tank (time of react + settle +decant + idle = E time of fill of all other tanks). This extended fill period could beused for a phosphorus or nitrogen removal strategy, but this is not required for thenutrient levels present in pulpmill wastewaters. The fill stage will therefore serveprimarily as an equalization period with a low level of substrate removal (much ofthe period will probably be anoxic). By minimizing aeration until fill is complete, thetemporary feast conditions useful to select for organisms with good settlingcharacteristics, can be maximized.The other major change between the research system and a pilot-scale and full-scale system would be the change from a consistent feed source to the highlyvariable on-line wastestream. An important research objective for a pilot-scale test90would be to determine if solids loading and SVIs stayed fairly stable under thesevariable loading conditions.An idle period is also incorporated into the design to provide a buffer of time tobe drawn from for fill time fluctuations due to flow rate variations (and for some reacttime adjustments as changes in mill processes of furnish dictate).The choice of sludge wasting rates (and corresponding SRT) is largely a designtrade-off between sludge digestion in the reactor and sludge treatment afterremoval. A higher sludge wasting rate would correspond to lower aeration energyrequirements, but increased manpower and sludge treatment requirements. Thedecision is a compromise based on expected costs of the extended aeration and theresulting increase in tank volume required, versus the costs of sludge disposal andtreatment.If the SBR incorporates solids clarification which would otherwise be performedin a preclarifier, this would increase the total concentration of MLVSS that must beretained in the reactor. At least the same concentration of active biomass would stillbe needed, but a significant fraction of the MLVSS would now consist of woodsolids. This increase in the sludge loading would increase the reactor volumerequired because the minimum liquid level would have to increase to contain thegreater volume of sludge. However, for influent solids levels that are notexcessively high, and SVIs that are reasonably low, this increase in reactor volumecould still be significantly lower than the additional volume that would be required ifa separate preclarifier were used.During non-aerated fill, the SBR acts as a stepwise equalization tank.Equalization and buffering requirements can often be accommodated throughproper design of the minimum liquid level and of the mixing and aeration periodsduring fill. The Quesnel River CTMP effluent includes no compounds that areknown to be significantly inhibitory of aerobic organisms at the concentrationspresent. Therefore for this design, providing buffering capacity with the liquidvolume retained after each cycle is not a concern.The greater the fraction of wastewater decanted per cycle, the more the feastconditions are maximized at the beginning of aeration. However, minimum liquidlevel and SRI are not independent. For any MLSS and SVI there is a maximumbiomass that can be contained in the tank, therefore setting a limit on sludge age forany minimum liquid volume fraction. For our typical MLSS of 4000 mg/I and anexpected SVI of 125 ml/g or less after 1.5 hours settling, the minimum liquid volume91would be 0.5 times the maximum volume (4g/I mixed liquor x 0.125 I sludge/g = 0.5I sludge per I mixed liquor). Similarly, adequate tank volume is also determinedonce mass loading and desired MLVSS are specified. It has been suggested that ataround 0.4 kg BOD5/kg MLVSS/d and lower, the SBR is not stressed andacceptable effluent quality should result [Irvine 1989].Almost all SBRs now in operation use jet aerators [Irvine 1989], which alsoprovide mixing when the blowers are off. If separate recirculation pumps areinstalled for mixing, or if nonaerated mixing (for nutrient removal) is not requiredthan a wide range of diffused air or floating mechanical aerators can be used.Using approximated rates of oxygen consumption from Irvine and Ketchum'sreview paper [1989], results in a rough estimate of adequately supplied oxygenconsumption rate of 20 g/kg MLVSS-h during aerated fill and the first few hours ofreact, and 15 g/kg MLVSS-h during the rest of the react period. Actual demandduring the end of the react period may fall even lower because the BOD5degradation rate has dropped so far by then, and sludge growth and respiration istherefore slowed. For the pilot system proposed below, 20 g/kg MLVSS-h works outto a consumption of 80 g 02 per hour per 1000 I tank.The results of the research are used to make the following recommendations fora pilot plant SBR for the Quesnel River Pulp mill. The pilot-scale system would beinstalled to receive the combined wastewater and whitewater that enters thedissolved air flotation clarifier (DAF) prior to anaerobic bio-treatment (the samewastewater source used in the research). This wastewater had a COD of 5000-10,000 mg/I, a BOD5 of 1500-3500 mg/I (average of roughly 2300 mg/I) and a TSSof 900-2000 mg/I [personal communication with Quesnel River Pulp technician AnnaRankin, 1993]. Alternately, if the SBR were installed after the DAF, this wouldreduce the usual influent COD to 2000-5000 mg/I, BOD5 to 800-2800 mg/I (averageof approximately 1650 mg/I) and TSS to 150-300 mg/I.The proposed pilot plant (summarized in table 18), is composed of four 1000 Itanks, each handling 500 I per cycle, or 667 I per day. The following specificationsuse an HRT slightly greater than that of the 24-hour cycles in the research system.92Table 18. Recommended Initial Protocol for Pilot PlantVolume out per tank 0.5 x maximum volume = 500 IStatic fill 3.5 hoursAerated fill 1 hourReact 9.5 hoursSettle 1.5 hoursDraw 1.5 hoursIdle 1 hourTotal cycle 18 hoursCycles/tank 1.33 per dayRatio draw / fill 0.33Residence time 36 hoursLoading 0.42 kg BOD5/kg MLSS-dEstimated Sludge wasted 0.33 kg/cycle per tankSludge age 12 daysThe loading is based on a BOD5 of 2500 mg/l. Uncommonly high BOD5loadings could be accommodated by utilizing the buffer capacity provided by theidle period, or by increasing the fraction of the fill period that is aerated. CommonF/M (mass loading, i.e. food to microorganism) ratios for conventional AS systemsare 0.2-0.4. High rate systems typically have F/M ratios between 0.4 and 1.5[Metcalf 1979]. The waste sludge concentration is approximately 10,000 mg/I for afinal SVI of 100 ml/g, as wastage occurs after settling. Therefore the waste sludgeflow rate is 133 l/day for the total 4000 I system.Sludge yields would likely be a little higher than in the research system, due tothe total aerated time comprising a smaller fraction of each day (14 hours ratherthan 22 hours). The reduction in sludge age is based on the higher wasting raterequired to allow for an increase in the sludge yield by up to 100% (to 0.3 kg/kgBOD5 from the value of 0.15 typical in the research system). The sludge age is93based on maintaining an MLVSS of 4000 mg/I with the expected maximum sludgeyield and an average reduction of 90% of the influent BOD 5 (using an influent BOD 5of 2500 mg/I).The actual sludge age would be adjusted based on early results, to establish thedesired solids loading. The sludge wasted could be significantly reduced if thesludge yield is closer to the yields that occurred in the research system. The dailyvolume of wastewater the reactors could treat might also increase if the SVIs arecloser to the research results than the more typical value allowed for, permitting agreater fraction of the treated wastewater to be decanted (as long as final BODsunder the slightly shorter HRT remained acceptable).Under the recommended operation conditions, both TSS and BOD5 regulationswould be easily met by the pilot plant if results corroborate the findings of thebench-scale research. A major objective in the assessment of the pilot-plant wouldbe to evaluate toxicity reduction with regular trout and/or daphnia bioassays.Quesnel River Pulp currently uses nutrient addition for the biological treatmentsystem that is aimed at 3 parts N and 0.7 parts P to 100 parts influent BOD5[personal communication, Anna Rankin 1993]. This would be a suitable,conservative starting level for the SBR pilot plant, with decreases likely possibledepending on early results, based on maintaining adequate soluble N and P levelsin the reactors at all times. Unless nutrient restrictions were implemented, it wouldnot be advisable to attempt to decrease nutrient addition too far, as it wouldnecessitate more stringent monitoring of nutrient concentrations than is necessaryunder a reasonably generous rate of supplementation.A microcomputer would be used to control the SBR cycles, with float controlsused for maximum and minimum liquid levels. The aerated fill period could becontrolled by timer or triggered by a level sensing device (e.g. to start when tank is3/4 full) or a DO probe (e.g. to terminate aeration period once a DO of 1.0 mg/I wasreached).The decanter should be designed to follow the fall of the liquid level, tocontinually draw from the most clarified region. This, accompanied by a longersettling period, would improve both the BOD 5 and TSS of the effluent compared tothose obtained with the bench-scale research system. The entrance to the decantershould be positioned to draw effluent from 15-20 cm below the surface [Shubert1986] to prevent any floating scum from entering. Entrance turbulence should beminimized to avoid resuspending sludge as the decanter system approaches the94depth of the settled sludge. A skimming device is probably not required as littlescum accumulated during operation of the bench-scale system, and would not bedrawn into a properly-designed decanting system.It is recommended that the pilot-scale system have a depth as close as practicalto the typical SBR design, to allow proper assessment of settling. Full-scalesystems typically have at least a 2.4 m minimum depth [Shubert 1986]. For a 4000 Ipilot plant with a 1.2 m minimum depth, example dimensions are 2.4 m maximumliquid depth and 73 cm diameter for each of four reactors. For the full-scale plant,the separate reactors might share common walls between rectangular chambers.The aerator system sizing is based on the ability to adequately meet the peakdemand periods. The actual oxygen requirement (AOR) is calculated from agenerous allowance for expected oxygen required per quantity BOD5 removed, i.e.1.5 kg 02/kg BOD5 (would also include an oxygen allowance for nitrification if therewere larger concentrations of ammonia), or oxygen per quantity MLVSS per hour asmentioned above. The standard oxygen requirement (SOR) is calculated bydividing the AOR by a correction factor for oxygen transfer conditions such as liquidtemperature, atmospheric pressure and wastewater characteristics.For an operating temperature of 350C, a fine bubble diffuser depth of 2 m, a of0.7 and 13 of 0.95 (estimated from the oxygen transfer measurements on QuesnelRiver Pulp wastewater), and 2.0 mg/I residual DO, using the standard equation[Shubert 1986] the correction factor is calculated to be 0.529. The rate at whichoxygen must be applied to the system is then calculated by dividing the SOR by theefficiency of the air delivery system (e.g. approximately 5.9% per m of immersiondepth for a fine bubble diffuser [Shubert, 1986]. For the example given above of 80g 02/hour per 1000 I tank, this works out to 1280 g 02 per hour, or 0.25 m3 of airper minute per tank.Scaling up the pilot plant based on the maximum expected flow rate of 21,000m3/d (including all wastewater sources) would require a system with a volume of31,500 m3. Though this is very large it would have to be judged against an ASsystem of comparable HRT and flow rate, including the volume of the equalizationbasin and clarifier for the AS system, which would generally be unnecessary for anSBR system. The ASB at Quesnel River Pulp is 53,000 m3.The SBR volume might be reduced somewhat based on favourable results in thepilot plant, but major reductions could not be made because the system must allowfor possible fluctuations in SVIs and the large swings in BOD5 loading possible.95Due to the highly variable wastewater characteristics the system must besignificantly oversized compared to one capable of handling only the averageloading.For an example maximum (filled) depth of 8 m with a minimum (decanted) depthof 4 m, the surface area of this system would be 3938 m2, i.e. 62.7 m square. Depthselected would depend on both the aerator system chosen and the land areaavailable.There are several municipal SBR systems in place treating this large a flow rate,but they are much smaller due to the lower HRTs. No examples were found in theliterature of an industrial wastewater treatment SBR system designed for more than4000 m3/d, and most applications are under 1000 m3/d [Irvine 1989].It is expected that few companies would seriously consider a system that was notalready in place on a similar scale treating similar wastewaters, unless strongevidence was given supporting an expectation of substantial cost savings. Thebench-scale research system demonstrated several assets, such as low sludgeyield and low SVIs, which could be translated into direct cost savings on sludgetreatment, but similar results in a long-term pilot plant would have to be shown togenerate more interest in applying the SBR system to pulpmill wastewatertreatment.96CHAPTER 5CONCLUSIONSBecause the development of the TMP/CTMP industry is relatively recent, muchless research has been performed on the treatment of CTMP pulp mill wastewatersthan kraft mill wastewaters. Furthermore, though the sequencing batch reactorprocess has been applied to a wide variety of industrial wastewaters, littleinformation exists on its application to pulp mill wastewaters. This researchexamined the application of an SBR system to the aerobic treatment of CTMPTTMPwastewater.Aeration testsAlpha values for the wastewaters studied with the bench-scale SBR system,ranged from 0.60 to 0.83. Beta values determined ranged from 0.92 to 0.97.Though the aeration tests were performed to determine the oxygen transfercharacteristics of the particular system with the wastewaters that were to be used inbiological treatment research, a few more general conclusions can be drawn:As with other complex industrial wastewaters, there is a wide range of effluentcharacteristics possible from different TMP/CTMP mills and from different pulpingruns in the same mill. This results in a greater range of possible alpha, beta andtheta values than would be encountered in municipal aerobic treatment design. Asthe expense of either over-design or under-design for aerobic treatment can be verygreat, these results demonstrate that adequate testing is needed for thesecoefficients to predict oxygen transfer under actual operating conditions. Care isalso needed when choosing samples representative of the range of wastewatercharacteristics that will be produced.Biological Treatment Runs Throughout the work, several potential benefits of the SBR system overconventional activated sludge systems were apparent: much lower sludge yield,better sludge settling than often occurs in AS systems for pulpmill wastewater, thepossibility of combining equalization basin, reactor and clarifier in one unit, and highsystem flexibility. However, these advantages demonstrated in a bench-scalesystem are unlikely to change the practices of engineers designing CTMPwastewater treatment facilities. An SBR pilot plant would have to be installedtreating CTMP effluent wastewater, and show stable long-term results with a97significant improvement in cost efficiency over AS treatment, before a full-scaleplant would be considered. If the demonstrated benefits were not sizable,designers could be expected to stay with the proven AS system.Using Quesnel River CTMP/TMP wastewater, average COD reductions (in one-hour settled samples) near the end of runs with a 24-hour cycle time and 34.3-hourHRT were 28-41%, and 31-37% for 48-hour cycles with 68.6-hour HRT. Forsamples taken after an additional three hours of settling in beakers, these rangeswere 52-66% and 51-63% respectively. The extended HRT runs demonstrated thatalmost all the COD that could be removed by this process was removed during 24-hour cycles. COD removals were roughly 26% by four hours aeration, and 35% by16 hours aeration. The SBR reactors were able to tolerate the shock loadings ofvery high COD and BOD5 loadings (and high concentrations of toxins) at thebeginning of cycles.These results experienced generally minor variation between columns, includingthe 6.5 or 7.5 pH trials, trials with acid added at four hours, or the extended SRItrial. The pH-adjusted runs demonstrated that the low rates of removal after the first16 hours of aeration were not the result of inhibition by the high pH in uncontrolledpH columns. BOD5 in the one-hour settled samples for the various treatmentconditions were 67-77% for the 24-hour cycle runs, and 88-94% for samples afterthree hours additional settling. For the 48-hour cycles, BOD5 removal in the one-hour settled samples were 77-82%, and 91-96% in the four-hour settled samples.BOD5 and COD removal percentages for the one-hour settled samples were lowcompared to aerobic treatment results for similar wastewaters reviewed in theliterature. The removal percentages in the four-hour settled samples were onlyslightly lower than values from the literature, though the SBR was generallysubjected to much higher BOD5 loadings.Though nutrient levels were consistently low, the dissolved N and P levels at theend of the cycles were still adequate. The colour of all columns except the pH-controlled columns darkened greatly during treatment. Colour was found to be verypH dependent, with the samples around 6.5 pH from the early hours of treatment inuncontrolled columns not being discernibly different in colour from the samples atthe end of treatment in the 6.5 pH column. SVIs for this system were between 53and 82 ml/g in 24-hour cycles, and 58-96 ml/g in 48-hour cycles. The settlingcharacteristics varied little between columns, except for the pH 6.5 column whichconsistently settled more compactly. This column also accumulated a significantlygreater concentration of sludge.98Sludge yields for this system were uniformly low. The values for the 24-hourcycles were 0.11-0.12 kg MLVSS per kg COD removed and 0.15-0.18 kg MLVSSper kg BOD5 removed. Both are about 1/4 the typical ratios for conventional ASsystems. The values for the 48-hour cycles were higher (0.16-0.20 and 0.20-0.22respectively) as the sludge concentrations were still falling from levels establishedduring the 24-hour cycles. The low sludge yields would translate directly intosavings in sludge treatment costs.Recommendations for the design of a pilot-plant for a BCTMP pulp mill weremade. Though an often-mentioned benefit of the SBR is the combination ofreaction tank and clarifier in one unit, for our system separate additional settlingtime was more effective than the diminishing returns of continuing aeration beyond16 hours. In scale-up of the system, if no separate clarifier were used, the settlingperiod should be made as long as possible without seriously deteriorating the healthof the sludge. Based on the results, a total aeration time of about 12 hours with acycle time of 18 hours and HRT of 36 hours, is suggested as the initial protocol for apilot plant based on this system for comparable wastewater. A primary focus for thepilot plant would be to determine if adequate reduction in toxicity could be achievedduring that retention time.996. NOMENCLATURE SUMMARYSymbolsa^interfacial area per unit volume of liquid (NV)A^interfacial area between the gas and liquid phasesactual dissolved oxygen concentration in the liquid phaseC*^dissolved oxygen saturation concentrationCs'^saturation concentration of DO at equilibrium with the gas entering theliquid at an equivalent pressure to the liquid above the aeratorF/M^food to microorganism ratioHenry's law constantKL^mass transfer coefficientKLa^volumetric oxygen mass transfer coefficientmass of 02 transferred per unit timeOc^aeration capacity, i.e. the rate of oxygen transfer during aeration for aspecified temperature and in water that is completely deoxygenatedPg^partial pressure of a specific gas in the gas phase.o^volumetric flow rateV^liquid volumea ratio of KLa measured in process water to KLa in clean water underequivalent conditions of temperature, mixing and geometry13^ratio of C* in process water to C* in clean water at the same conditionsof partial pressure and temperatureempirical temperature correction coefficientAbbreviations AOR^actual oxygen requirementBCTMP^bleached chemithermomechanical pulpBOD^biochemical oxygen demand100BOD5^BOD exerted in a 5-day test periodC.I.^confidence intervalCOD^chemical oxygen demandCTMP^chemithermomechanical pulpDAF^dissolved air flotationDO^dissolved oxygenEC50^effective concentration to reduce light output to 50% ofunchallenged Microtox culturesHRT^hydraulic retention timeLC50^lethal concentration causing the death of 50% of test organismMLSS^mixed liquor suspended solidsMLVSS^mixed liquor volatile suspended solidsPER^plug flow reactorQRP^Quesnel River Pulp millRFA^resin acids and fatty acidsSBR^sequencing batch reactorSOR^standard oxygen requirementSRT^solids retention timeSVI^solids volume indexIMP^thermomechanical pulpIS^total solidsTSS^total suspended solidsUASB^upflow anaerobic sludge blanketVS^volatile solidsVSS^volatile suspended solids1017. 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Water PoIlut. Control Fed., 51, 255-263 (1979).Flammino, A., Bellanca, M.A. and Tracy, K.D., Pilot study of activated sludgeprocess incorporating an anaerobic selector for the treatment of pulp and paperwastewater. TAPPI Environ. Conf., Seattle, Wash., 305-320 (1989).Flippin, T.H. and Bellanca, M.A., Diagnosing and solving a pulp and paper mill'spoor activated sludge settleability problems through treatability studies. TAPPIEnviron. Conf., Seattle, Wash., 541-548 (1992).Galil, N., et al., The influence of mixing on the physical characteristics of biologicalflocs. Res. J. Water Pollut Control Fed., 63, 768, (1991).Goddard, A.J. and Forster, C.F., Stable foams in activated sludge plants. Enzymeand Microbial Technology, 9, 164-168 (1987).Gostick, N.A., Nutrient requirements in biological effluent treatment. Pap. Technol.Ind., 31, 8, 33 (1990).Hach. Hach DR/2000 Spectrophotometer Handbook. Loveland, Colorado: HachCompany, (1988).Hu, P., et al., Effects of pH on fungal growth and bulking in laboratory activatedsludges. Res. J. Water Pollut. Control Fed., 63, 276 (1991).Irvine, R.L. and Ketchum, L.H. Jr., Sequencing batch reactors for biologicalwastewater treatment. Crit. Rev. Environ. Control, 18, 4, 255-294 (1989).Irvine, R.L., Ketchum, L.H., et al., An organic loading study of full-scale sequencingbatch reactors. Res. J. Water Pollut. Control Fed., 57, 847-853 (1985).103Irvine, R.L., Ketchum, L.H., et al., Municipal application of sequencing batchtreatment. Res. J. Water Pollut. Control Fed., 55, 484-488 (1983).Jeffries, D.W., Ellerman, M, et al., Identification and control of activated sludgesettling problems at a sulfite pulp and paper mill. TAPPI Environ. Conf. Proc.,335-343 (1989).Kang, S.J. and Fifield, C.D., Anoxic selector technology for control of filamentousbulking for paper mill wastewater. TAPPI Environ. Conf., Seattle, Wash., 435-440 (1992).Kantardjieff, A., Jones, J.P., et al., Degradation of toxic compounds in TMP milleffluents by biological aerated filter. TAPPI Environ. Conf., Seattle, Wash., 251-259 (1990).Ketchum, L.H. Jr., et al., A comparison of biological and chemical phosphorusremovals in continuous and sequencing batch reactors. Res. J. Water Pollut.Control Fed., 59, 13-18 (1987).Lau, A.O., Strom, P.F. and Jenkins, D., The competitive growth of floc-forming andfilamentous bacteria: a model for activated sludge bulking, Res. J. Water Pollut.Control Fed., 56, 1, 52-61 (1984).Leach, J.M., Mueller, J.C. and Walden, C.C., Biodegradability of toxic compoundsin pulp mill effluents. Transactions, 3, 4 126-130 (1977a).Leach, J.M. and Thakore, A.N., Compounds toxic to fish in pulp mill waste streams.Prog. Wat. Tech. 9, 787-798 (1977b).Leach, J.M. and Thakore, A.N., Toxic constituents in mechanical pulping effluents.Tappi, 59, 2, 129-132 (1976).Lo, S.-N., Liu, H.W., et al., Characterization of pollutants at source and biologicaltreatment of a CTMP efflluent. Appita, 44, 2, 133-138 (1991).Mackie, D.M. and Taylor, J.S., Review of the production and properties of alphabetpulps. Pulp and Paper Canada, 89, 2, 58-65 (1988).MacLean, B., de Vegt, A.L. and van Driel, E., Full-scale anaerobic/aerobic treatmentof TMP/BCTMP effluent at Quesnel River Pulp. TAPPI Environ. Conf., Seattle,Wash., 647-661 (1990)Manning, J.F. and Irvine, R.L., The biological removal of phosphorus in asequencing batch reactor. Res. J. Water Pollut. Control Fed., 57, 87-94 (1985).104McAllen, V.E., Operational results for treatment of chemi-thermomechanical pulpingeffluents. Presented at "Workshop on Treatment of TMP/CTMP Wastewater",Organized by Environment Canada, Vancouver, B.C. April 5-7, 1989.McCarthy, P.J., Kennedy, K.J. and Droste, R.L., Anaerobic toxicity of resin acids inchemithermomechanical pulp wastewater. Proc. 45th Ind. Waste Conf., PurdueUniv., West Lafayette, Ind., 435-440 (1991).Meloni, E., Practical experience with biological removal of phosphorus from pulpand paper mill effluerts. Water Sci. TechnoL (G.B.), 24, 3/4, 277-286 (1991).Metcalf & Eddy, Boston. Wastewater Engineering: Treatment, Disposal & Reuse,Second Ed. Toronto: McGraw-Hill Book Company, 64 (1979).Mobius, C.H., Nitrogen and phosphorus limits for nutrient deficient industrialwastewaters. Water Sci. Technol. (G.B.), 24, 3/4, 259-267 (1991).Mobius, C.H., Biological treatment of papermill wastewater in an activated sludgecascade reactor. Water Sci. Technol. (G.B.), 21, 1825-1828 (1989).Mobius, C.H., Improvement of COD elimination in activated sludge treatment plantfor pulp and paper mill waste waters. Water Sci. Technol. (G.B.), 20, 1, 121-132(1988).Nakazawa, H. and Tanaka, K., Kinetic model of sequencing batch activated sludgeprocess for municipal wastewater treatment. Water Sci. Technol. (G.B.), 23, 4-6,1097-1106 (1991).Okada, M., Terazono, K. and Sudo, R., Removal of nutrients and BOD fromsoybean fermentation wastewater in a ten-year-old sequencing batch reactoractivated sludge process. Water ScL Technol. (G.B.) 22, 9, 85-92 (1990).Oles, J. and Wilderer, P.A., Computer aided design of sequencing batch reactorsbased on the IAWPRC activated sludge model. Water ScL Technol. (GB.), 23,4-6, 1087-1095 (1991).Palis, J.C. and Irvine, R.L., Nitrogen removal in a low-loaded single tanksequencing batch reactor. Res. J. Water Pollut. Control Fed., 57, 82-86 (1985).Prouty, AL., Bench-scale development and evaluation of a fungal bioreactor forcolor removal from bleach effluents. Appl. Microbiol. Biotechnol., 32, 490-493(1990).Qasim, SR., Chang, S.-Y. and Parker, C.E., Comparative performance ofconventional anoxic-aerobic, and anoxic-anaerobic-aerobic treatment processes105for biological nutrient removal. Proc. 46th Ind. Waste Conf., Purdue Univ., WestLafayette, Ind., 641-649 (1992).Rankin, A., Irvine, G.A., et al., Pilot studies on activated sludge at Quesnel RiverPulp. Preprints of the 1992 Spring Conference, Canadian Pulp & PaperAssociation, Technical Section, Pacific Coast and Western Branches. May 13-16, 1992.Reeser, D.M., Johnson, W. and Gibson, L., Selecting equipment for aerobictreatment c' CTMP effluent. TAPPI Environ. Conf., Seattle, Wash., 535-555(1990).Saugier, R.K. and Vegega, A.M., AOX and color removal from bleach plant effluent -meeting the challenge with peroxygens. TAPPI Environ. Conf., Seattle, Wash.,375-383 (1991).Servizi, J.A. and Gordon, R.W., Detoxification of TMP and CTMP effluentsalternating in a pilot scale aerated lagoon. Pulp and Paper Canada, 87, 11, 42-46 (1986a).Servizi, J.A., Martens, D.W., et al. Microbiological detoxification of resin acids.Water Poll. Res. J. Canada, 21, 1, 119-129 (1986b).Shubert, W.M., Sequencing Batch Reactor, Aqua-Aerobic Systems, Inc., Rockford,Illinois, 1986.Silverstein, J. and Schroeder, E.D.,^Performance of SBR activated sludgeprocesses with nitrification/denitrification. Res. J. Water Pollut. Control Fed., 55,377-384 (1983).Soddell, J.A. and Seviour, R.J., Microbiology of foaming in activated sludge plants.J. Appl. Bacterial. 69, 145-176 (1990).Standard Methods for the Examination of Water and Wastewater. M.A.H. Franson,ed., American Public Health Association, Washington (1989).Unz, R.F. and Williams, TM., The effect of controlled pH on the development ofrosette-forming bacteria in axenic culture and bulking activated sludge. WaterSci. Technol. (GB.), 20, 249-255 (1988).Urbantas, R.G. and MacEwen, H.D., Characterization of effluents fromchemimechanical, chemithermomechanical and thermomechanical pulping ofblack spruce. Preprints of 71st Annual Meeting, Canadian Pulp and PaperAssocation, A213-219 (1985).106Vaananen, P., Control of the phosphorus level of effluent in the treatment of forestindustry waste waters. Water Sci. Technol. (G.B.), 20, 1, 81-86 (1988).Wong, A., Breck, D. and Costantino, J., TMP effluents. Tappi, 61, 8, 19-22(1978).WPCF. Aeration (WPCF Manual of Practice, #FD-13). Water Pollut. Control Fed.and Am. Soc. of Civ. Eng. (1988).107APPENDIX A. Theory of Oxygen TransferSince the SBR process studied is aerobic, oxygen must be supplied to themicroorganisms that are removing the BOD. Following is an overview of the theoryof oxygen transfer.Oxygen transfer from a gas phase to a liquid phase can be described byequation 1.N KLA ( C* - C ) ^ (1)where N is the mass of 02 transferred per unit time,KL is the mass transfer coefficient,A is the interfacial area between the gas and liquid phases,C* is the solubility of oxygen in the liquid phase when in equilibrium with the gasphase, andC is the actual dissolved oxygen concentration in the liquid phase.Consider the individual terms in equation 1 with respect to their effects on 02transfer in a wastewater treatment system:The required N is determined by the BOD of the wastewater. Thus if the inletBOD of the wastewater is x mg/I, the desired outlet BOD is y mg/I and the dailyflowrate of wastewater is Q 1/d, then N is Q(x-y) mg of 02/d. Adequate levels ofoxygen must also be provided for the respiration requirements of the biomass, evenonce most of the wastewater BOD has been removed. Dissolved oxygen (DO)levels are always maintained at least slightly higher levels than theoreticallyrequired, to ensure that despite changing wastewater and biomass conditions anoxygen deficit does not occur.KL, the mass transfer coefficient, is determined by the physical properties of theliquid and gas. The relevant properties are the gas - liquid density difference, liquidviscosity, diffusivity of the gas in the liquid, and the molecular weight of the gas.Thus for a particular gas and liquid at a given temperature, KL is fixed.A is the interfacial area between the liquid and gas phases. To put this in termsof interfacial area per unit volume of liquid, a, divide both sides of equation 1 by theliquid volume V, thusNN = KLa [C* - C] ^ (2)where a = AN.108A and a are affected by the parameters of the oxygen delivery system, includingsuperficial gas velocity and power input per unit volume. Provision of adequatevalues of a is the major expense in aerobic biological wastewater treatment. Thisexpense is associated with the cost of running compressors and/or agitators. Sincevalues for a are difficult to measure and values for KLa are not, data correlations areusually done in terms of the product KLa, the volumetric mass transfer coefficient.Aerator suppliers sometimes also rate their equipment in terms of KLa.C is the level of dissolved oxygen present in the wastewater. It is desirable tokeep this value as low as practical, to maximize transfer rates.C* is the concentration of dissolved oxygen in the liquid in equilibrium with thegas phase, i.e. the oxygen saturation concentration. Henry's law states that C* for agas in a liquid is directly proportional to the partial pressure of the gas in theatmosphere in contact with the liquid. Oxygen is only slightly soluble in water, soHenry's law can be used as an equilibrium relationship.C* = H.pg   (3)where H is the Henry's law constant for oxygen andpg is the partial pressure of oxygen in the gas phase.Note that C* is affected by the mole fraction of oxygen in the gas phase and thetotal pressure on the system. C* is also a function of temperature since the Henry'slaw constant is temperature dependent - the higher the temperature the lower thesolubility. For example, in pure water at 200C exposed to an atmosphere containing21% oxygen, C* is 9.17 mg/I, whereas at 300C, it is 7.63 mg/I. C* is also affected bythe composition of the wastewater through the presence of dissolved solids, beingparticularly affected by electrolytes. Values quoted in textbooks and handbooks areusually those for pure water.Pure oxygen is sometimes used in aeration because the value of Pg is 1.0compared to 0.209 at atmospheric pressure for air. Thus C* should be 4.78 timeshigher when pure 02 is used. If pure 02 is used as the oxygen source then,because C* is much higher, the driving force is much greater. So if the oxygendemand is the same, the KLa value necessary for an 02 system should besignificantly less. This should lead to reduced capital and operating costs for theaeration system. These savings of course must be balanced against the increasedcosts of the pure 02. There are now over 200 oxygen-activated plants in operationaround the world for the treatment of both industrial and municipal wastewaters[WPCF 1988].109In comparing air and 02 treatment systems, it should be borne in mind that thesize of the aeration tank is determined by BOD removal kinetics and sludge settlingcharacteristics. Provided there is an adequate level of dissolved 02, BOD removalrates are not affected by this parameter. However, with a pure oxygen system ahigher level of microbial cell concentration can be maintained in the reactor withoutDO becoming rate-limiting, and therefore the rate of BOD reduction per unit volumecan be higher.Values for C should be at least 1-2 mg/I to ensure that dissolved 02 is not rate-limiting. In systems like the SBR and activated sludge, in which organisms grow inflocs, the higher the DO level, the greater the penetration of DO into the floc. Thiscan affect the species mix in the floc's microbial population and can affect thesettleability of the flocs in the settling stage of an SBR or in the clarifier of anactivated sludge process [Lau 1984].In addition to KLa, aeration can also be characterized using the three factorsalpha, beta and theta, and the aeration capacity. The ratio of KLa measured inmixed liquor (wastewater and biomass) or process water to KLa measured in cleanwater under the same conditions, is designated alpha. Beta is defined as the ratioof C* in the wastewater to C* in clean water, both in equilibrium with the same gascomposition at the same temperature and pressure.A theta factor (A) is used to correct the molecular diffusion rate of oxygen fortemperature. It is commonly used to standardize test data collected at operatingtemperature to the standard liquid temperature of 200C. Equation 4 illustrates this.(KLa)T = (K0)20 x (e)T-20   (4)where (KLa)r is the value of the coefficient at the specified temperature,(K0)20 is the value of the coefficient at 200C, andT is the temperature in 0C.The standard theta value of 1.024 is usually adequate for most applicationsbetween 10 and 300C [Bass 1977].If values of C* and KLa obtained in water are to be used in the design of anaeration system for wastewater treatment, rewrite equation 2 asN = a.(K0)20.0T-20.(13c* _ C) ^ (5)where KLa and C* are values for clean water.110The aeration capacity (Os) is often defined as the rate of oxygen transfer duringaeration for a specified temperature and in water that is completely deoxygenated.It can be calculated using equation 6.Os = KLa•V • Cl   (6)where V is the liquid volume, andCsi is the saturation concentration of DO at equilibrium with the air or oxygenentering the liquid at an equivalent pressure to the liquid above the aerator [Boon1980].In this research oxygen saturation values at atmospheric pressure weremeasured and used to calculate 13 values. For the aeration capacity calculationsthese values are corrected for the mid-depth pressure of the reactor.111APPENDIX B. Example Nutrient Levels from Runs B and C Ammonia Nitrate OrthophosphateDate Column Sample, hr Nitrogen, mg/I Nitrogen, mg/I Phosphorus, mg/I10.16 1 22 0.25 0.3910.16 4 22 0.40 0.4410.16 5 22 0.45 0.6810.16 6 22 0.45 0.6512.03 5 4 0.20 10.5 1.3112.03 6 4 0.15 8.5 1.2012.03 5 16 0.10 8.5 1.2812.03 6 16 0.10 8.5 1.1512.03 5 22 0.10 8.5 0.9212.03 6 22 0.15 8.0 1.0312.15 5 46 0.20 9.5 1.3312.15 6 46 0.15 8.0 1.1391.09 IN 1.10 14.0 3.3891.09 IN 1.15 13.5 3.5991.12 IN 0.75 11.5 2.0591.12 IN 0.75 12.0 2.15All nutrient measurements are of supernatant from fully clarified samples112Appendix C.^ Solids Concentrations in Runs A, B and CCOL 1 COL 1 COL 2 COL 2g/I SL mg/I g/I SL mg/I g/I SL mg/I depth, in ml/g g/I SL mg/I g/I SL mg/I g/I SL mg/IMLVSSdepth, inSETTLEml/gSVICYCLE TS MLTS TSS MLTSS VSS MLVSS- SETTLE SVI TS MLTS TSS MLTSS VSS625629630701703704 NOTE g/I SL:mg/I:gives actual concentration in g/I of the sludge remaining in the 3 litres after decantingthese measurements are the corresponding calculated mixed liquor concentrations705714716720722724726728730918 21.70 6510 17.16 5148 15.90 4770 7.50 56.9 20.17 6051 16.32 4896 14.95 4485 9.00 71.8919 20.62 6186 16.90 5070 15.69 4707 7.00 53.9 19.35 5805 15.88 4764 14.49 4347 8.00 65.6922 20.65 6195 16.32 4896 15.23 4569 7.50 59.8 17.03 5109 13.95 4185 12.67 3801 7.50 70.0924 20.86 6258 17.07 5121 15.92 4776 7.50 57.2 16.74 5022 13.16 3948 12.10 3630 8.25 81.6926 20.26 6078 16.69 5007 15.47 4641 7.00 54.6 15.92 4776 12.03 3609 11.50 3450 7.50 81.21006 17.47 5241 12.53 3759 11.72 3516 6.50 67.5 6.501008 16.96 5088 12.43 3729 11.67 3501 6.75 70.7 6.001014 16.55 4965 12.21 3663 11.05 3315 7.00 74.6 6.751016 16.52 4956 11.67 3501 11.07 3321 7.00 78.1 6.501122 17.20 5160 13.26 3978 12.46 3738 6.00 58.9 17.17 5151 13.71 4113 12.65 3795 7.50 71.21124 17.66 5298 14.27 4281 13.43 4029 6.00 54.7 17.69 5307 13.85 4155 13.32 3996 8.00 75.21126 19.56 5868 15.23 4569 14.35 4305 6.75 57.7 17.56 5268 14.54 4362 13.62 4086 8.50 76.11129 19.98 5994 15.69 4707 14.92 4476 7.00 58.1 17.62 5286 14.05 4215 13.41 4023 8.50 78.81201 20.27 6081 15.75 4725 15.00 4500 7.50 62.0 17.69 5307 13.51 4053 12.98 3894 8.50 81.91203 19.81 5943 15.40 4620 14.63 4389 7.00 59.2 17.87 5361 14.00 4200 13.44 4032 8.25 76.71213 17.79 5337 14.44 4332 13.88 4164 8.50 76.61217 16.71 5013 13.59 4077 13.02 3906 8.25 79.0122312271231104113Appendix C.^ Solids Concentrations in Runs A, B and CCOL 3 COL 3 COL 4 COL 4./I SL m• I .11 SL MBERE •/1 SL MEM de•th, in MEM •/1 SL m• I IIERNIEVAIMMENI m /I de•th^in mIt•MLTS TSS629 5160 14.78 4434 14.14 424216.21 4863 14.19 4257 13/85001 13.05 3915 12.4712.93 3879 12.54 376214.33 4299 13/9 41375064 13.28 6.00324012.972766 8.89 4.75• 3435 9.30 8.803441 9.25• 20.67 6201 16.05 S. 8.25 19.55 15.94 4782 14.88SI. IS• 4065 12.44 7.50 72.114.61 4383 17.95 4152 13.13 75.3122312271231104114Appendix C.^ Solids Concentrations in Runs A, B and CCOL 5 COL 5 COL 6 COL 6MMWMWMINEM.MMM= de th, in Ejj=MMWM.MMOMMMaINIE:g1n. de .th, inCYCLE TS^MLTS^TSS^MLTSS^VSS^MLVSS SETTLE SVI TS MLTS^TSS^MLTSS^VSS^MLVSS SETTLE SVI625 16.15 4845 15.35 4605 14.79 4437 16.12 4836 14.02 4206 13.47 4041629 16.33 4899 15.24 4572 14.77 4431 16.67 5001 14.29 4287 13.84 4152630 16.54 4962 15.36 4608 14.89 4467 16.00 4800 13.26 3978 12.83 3849701 17.46 5238 14.81 4443 14.35 4305 17.49 5247 14.54 4362 14.10 4230703 17.25 5175 14.54 4362 14.05 4215 17.00 5100 14.46 4338 14.09 4227704 17.00 5100 15.16 4548 14.70 4410 16.25 4875 14.06 4218 13.68 4104705 16.83 5049 14.88 4464 14.37 4311 6.50 56.9 16.08 4824 13.88 4164 13.42 4026 6.50 61.0714 13.63 4089 9.60 2880 9.25 2775 4.75 64.4 12.27 3681 8.98 2694 8.64 2592 4.75 68.9716 12.55 3763.71 9.51 2853 9.11 2733 12.76 3828 8.71 2613 8.45 2535720 12.12 3636 9.25 2775 8.89 2667 5.00 70.4 12.22 3666 8.97 2691 8.61 2583 5.00 72.6722 11.77 3531 9.09 2727 8.72 2616 11.93 3579.03 8.89 2667 8.48 2544724 11.79 3537 8.90 2670 8.64 2592 5.00 73.2 11.70 3510 8.59 2577 8.19 2457 5.00 75.8726 11.70 3510 8.92 2676 8.44 2532 11.73 3519 8.45 2535 8.00 2400728 12.10 3630 8.42 2526 8.05 2415 11.50 3450 8.04 2412 7.75 2325730 11.62 3486 8.46 2538 8.18 2454 11.77 3531 8.06 2418 7.73 2319918 20.45 6135 16.49 4947 15.70 4710 7.50 59.2 20.88 6264 16.80 5040 15.67 4701 7.75 60.1919 20.72 6216 17.03 5109 15.62 4686 7.50 57.3 20.71 6213 16.95 5085 15.73 4719 7.25 55.7922 19.93 5979 16.11 4833 14.83 4449 6.50 52.5 19.92 5976 15.73 4719 14.66 4398 7.00 57.9924 19.96 5988 15.98 4794 15.16 4548 6.75 55.0 20.99 6297 16.46 4938 15.34 4602 7.25 57.4926 20.22 6066 16.32 4896 15.37 4611 7.00 55.8 20.62 6186 16.80 5040 15.55 4665 7.00 54.31006 19.03 5709 15.04 4512 13.75 4125 7.00 60.6 18.60 5580 14.59 4377 13.38 4014 7.00 62.51008 18.45 5535 14.99 4497 13.58 4074 7.00 60.8 17.33 5199 13.93 4179 12.98 3894 7.00 65.41014 17.63 5289 14.37 4311 13.13 3939 6.75 61.2 16.69 5007 13.02 3906 12.03 3609 7.75 77.51016 17.01 5103 13.38 4014 12.46 3738 6.75 65.7 16.46 4938 12.66 3798 11.47 3441 7.75 79.71122 17.26 5178 13.29 3987 12.12 3636 7.00 68.6 17.10 5130 13.80 4140 12.91 3873 7.00 66.01124 16.92 5076 14.25 4275 12.91 3873 7.25 66.2 17.08 5124 13.75 4125 12.61 3783 7.00 66.31126 16.44 4932 13.55 4065 12.56 3768 7.75 74.5 16.89 5067 14.46 4338 13.32 3996 7.75 69.81129 16.66 4998 13.80 4140 12.54 3762 8.25 77.8 17.25 5175 14.33 4299 13.29 3987 8.50 77.21201 16.58 4974 13.38 4014 12.64 3792 7.75 75.4 17.59 5277 13.88 4164 13.21 3963 8.00 75.01203 16.73 5019 13.55 4065 12.80 3840 8.00 76.9 17.45 5235 14.27 4281 13.36 4008 8.50 77.61213 14.06 4218 10.62 3186 10.08 3024 7.25 88.9 15.78 4734 11.75 3525 11.44 3432 7.75 85.91217 13.61 4083 10.15 3045 9.85 2955 7.50 96.2 15.03 4509 11.25 3375 10.72 3216 8.25 95.51223 13.20 3960 9.74 2922 9.36 2808 7.75 103.6 13.91 4173 10.11 3033 9.76 2928 7.75 99.81227 12.41 3723 8.84 2652 8.41 2523 8.00 117.8 13.68 4104 9.99 2997 9.63 2889 8.00 104.31231 12.44 3732 8.76 2628 8.26 2478 8.00 118.9 13.59 4077 9.91 2973 9.51 2853 8.25 108.4104 11.97 3591 8.37 2511 7.88 2364 8.00 124.5 13.21 3963 9.38 2814 8.88 2664 8.50 118.0115APPENDIX D. COD Measurements from Runs A, B and C In the following tables there are several abbreviations that do not appear in themain body of the text. These are explained here.Sample Names:A^16 hour sample point, with sample taken 16 hours into aeration. Samples arethen settled for one hour in beakers and supernatant used as actual sample.22 hour sample point, with sample taken following 22 hours aeration and 1hour in-situ settling in 24-hour cycles, or following 22 hours aeration in 48-hour and 96-hour cycles and then settled for one hour in beakers andsupernatant used as in 16-hour point.46 hour sample point, with sample taken following 46 hours aeration and 1hour in-situ settling in 48-hour cycles, or following 46 hour aeration in 96-hour cycles and then settled for one hour as in 16-hour point.S-COD^COD of supernatant from additional three hours of settling.116Appendix D.^ COD Measurements From Runs A, B and CRUN A COL 4 COL 5DATE TIME pH COD %REM S-COD %REM DATE TIME pH COD %REM S-COD %REM7.01 B 8.61 3569 40.33 2819 52.87 7.01 B 8.57 3729 37.65 2731 54.347.02 0 7.59 4566 23.65 3534 40.91 7.02 0 7.53 4651 22.23 3463 42.097.02 2 8.10 4227 29.32 3364 43.75 7.02 _ 2 8.03 4373 26.88 3235 45.917.02 4 8.23 3949 33.97 3188 46.69 7.02 4 8.20 4077 31.82 3041 49.147.02 A 8.47 3580 40.13 2672 55.32 7.02 A 8.45 3756 37.20 2748 54.047.02 B 8.60 3492 41.60 2549 57.37 7.02 B 8.63 3577 40.18 2690 55.027.03 0 7.62 4652 22.20 3592 39.93 7.03 0 7.58 4797 19.78 3633 39.247.03 2 8.11 4250 28.93 3411 42.97 7.03 2 8.04 4343 27.38 3358 43.857.03 4 8.25 3933 34.23 3112 47.97 7.03 4 8.28 4112 31.23 3077 48.557.03 A 8.52 3700 38.13 2696 54.92 7.03 A 8.56 3697 38.18 2701 54.837.03 B 8.63 3545 40.71 2684 55.12 7.03 B 8.62 3521 41.13 2713 54.637.04 0 7.63 4634 22.51 3469 41.99 7.04 0 7.65 4666 21.98 3440 42.487.04 2 8.17 4233 29.21 3241 45.81 7.04 2 8.22 4134 30.87 3153 47.287.04 4 8.28 3911 34.60 2912 51.30 7.04 4 8.31 3992 33.24 2912 51.307.04 A 8.53 3615 39.54 2678 55.22 7.04 A 8.55 3671 38.61 2631 56.00_^7.04 B 8.68 3490 41.65 2543 57.47 7.04 B 8.71 3507 41.35 2567 57.087.05 0 7.64 4623 22.69 3399 43.16 7.05 0 7.70 4616 22.81 3446 42.387.05 2 8.23 4205 29.68 3129 47.67 7.05 2 8.24 4091 31.58 3077 48.557.05 4 8.34 4006 33.00 2965 50.42 7.05 4 8.36 3875 35.20 2901 51.497.05 A 8.58 3636 39.20 2631 56.00 7.05 A 8.60 3691 38.27 2655 55.617.05 B 8.72 3528 41.01 2532 57.67 7.05 B 8.74 3557 40.52 2584 56.787.06 0 7.61 4652 22.21 3498 41.50 7.06 0 7.69 4666 21.98 3516 41.207.06 2 8.20 4247 28.97 3252 45.61 7.06 2 8.22 4152 30.57 3194 46.597.06 4 8.29 3952 33.92 2989 50.02 7.06 4 8.29 3940 34.11 2942 50.817.06 A 8.52 3633 39.25 2637 55.90 7.06 A 8.58 3642 39.10 2690 55.027.06 B 8.65 3510 41.30 2573 56.98 7.06 B 8.69 3522 41.11 2602 56.49117Appendix D. COD Measurements From Runs A, B and CRUN A COL 6DATE TIME pH COD %REM S-COD %REM7.01 B 8.62 3513 41.25 2825 52.777.02 0 7.52 4695 21.49 3504 41.407.02 2 8.04 4297 28.15 3118 47.877.02 4 8.22 4007 32.99 3053 48.957.02 A 8.51 3706 38.03 2772 53.657.02 B 8.66 3533 40.91 2602 56.497.03 0 7.62 4787 19.96 3545 40.717.03 2 8.09 4401 26.40 3323 44.447.03 4 8.27 4109 31.29 3129 47.677.03 A 8.58 3664 38.74 2737 54.247.03 B 8.68 3517 41.19 2549 57.377.04 0 7.68 4556 23.81 3440 42.487.04 2 8.21 4038 32.47 3200 46.507.04 4 8.32 3907 34.66 3041 49.147.04 A 8.60 3586 40.03 2643 55.817.04 B 8.73 3416 42.87 2502 58.167.05 0 7.70 4538 24.11 3440 42.487.05 2 8.27 4237 29.15 3223 46.107.05 4 8.37 4031 32.59 2901 51.497.05 A 8.62 3656 38.86 2701 54.837.05 B 8.76 3557 40.52 2660 55.517.06 0 7.70 4552 23.87 3469 41.997.06 2 8.26 4251 28.91 3229 46.017.06 4 8.32 3969 33.63 2977 50.227.06 A 8.55 3674 38.57 2666 55.417.06 B 8.72 3533 40.91 2555 57.27118Appendix D.^ COD Measurements From Runs A, B and CRUN A COL 4 COL 5DATE TIME pH COD %REM %REM DATE jjJ pH COD %REM S-COD %REM7.12 0 7.56 5497 8.08 33.61 7.12 7.58 5482 8.33 3950 33.957.12 4 8.08 4809 19.58 36.79 7.12 8.10 36.297.12 A 8.61 4227 29.31 S 49.25 8.66 48.757.12 B 8.67 3958 3921 •7.12 C 3670 3630 39.297.14 5545 56887.14 4 S 51037.14 43767.14 B 4261 8.807.14 C 39977.16 6.768.07047.22 A7.220AB 8.53 4200 29.77 3055 • 7.24 3035 49.25C 8.67 4000 33.11 3020 5 7.24 3005 49.75• 0 7.45 5627 5.90 4065 S 7.26 3980 33.44• 4 7.84 5303 11.32 3860 7.26 5 3920 34.45• A 8.36 4421 26.07 3085 7.26 3125 47.74• B 8.52 4283 28.38 3050 5. 7.26 • 3105 48.08•fl C 8.59 3994 33.21 2925 5. 7.26 • 2990 50.00C 8.58 3843 35.74 2900 7.28 • 2950 50.67• 0 7.47 5673 5.13 4015 7.30 3950 33.954 7.89 5140 14.05 3840 • 7.30 3820 36.12A 8.37 4233 29.21 3080 7.30 3050 49.00B 8.53 3946 34.02 2970 S 7.30 2990 50.007.30 C 8.61 3831 35.93 2935 50.92 7.30 C 8.57 3823 36.07 2940 50.84119Appendix D. COD Measurements From Runs A, B and CCOL 6DATE TIME pH COD %REM S-COD %REM7.12 0 7.53 5355 10.46 3965 33.707.12 4 8.11 4855 18.82 3850 35.627.12 A 8.66 4300 28.09 3100 48.167.12 B 8.75 4052 32.25 3030 49.337.12 C 8.85 3664 38.74 2965 50.427.14 0 7.66 5561 7.01 4175 30.187.14 4 8.14 5212 12.84 4080 31.777.14 A 8.69 4491 24.90 3300 44.827.14 B 8.78 4224 29.36 3325 44.407.14 C 8.86 3918 34.48 3185 46.747.16 0 7.66 5576 6.76 4000 33.117.16 4 8.12 5306 11.27 3905 34.707.22 0 7.42 5548 7.22 4060 32.117.22 4 7.86 5142 14.01 3950 33.957.22 A 8.39 4276 28.50 3295 44.907.22 B 8.63 4100 31.44 3075 48.587.22 C 8.69 3858 35.49 3065 48.757.24 0 7.43 5685 4.94 4090 31.617.24 4 7.84 5145 13.96 3945 34.037.24^. A 8.38 4333 27.54 3145 47.417.24 B 8.57 4145 30.68 3060 48.837.24 C 8.69 3958 33.82 3020 49.507.26 0 7.47 5655 5.44 4060 32.117.26 4 7.85 5212 12.84 3955 33.867.26 A 8.39 4303 28.04 3200 46.497.26 B 8.51 4140 30.77 3005 49.757.26 C 8.58 3906 34.69 2990 50.007.28 C 8.60 3757 37.17 2890 51.677.30 0 7.48 5487 8.25 4010 32.947.30 4 7.90 4990 16.56 3820 36.127.30 A 8.35 4290 28.26 3110 47.997.30 B 8.49 4034 32.54 2985 50.087.30 C 8.55 3851 35.59 2950 50.67120Appendix D.^ COD Measurements From Runs A, B and CRUN B COL 1 COL 4DATE TIME pH COD %REM S-COD %REM DATE TIME pH COD %REM S-COD %REM9.17 0 7.29 7843 12.75 6590 26.70 9.17 0 7.10 7733 13.98 5655 37.109.17 4 7.98 7060 21.47 5230 41.82 9.17 4 7.96 7349 18.26 4970 44.729.17 B 8.45 6351 29.35 4095 54.45 9.17 B 8.10 6343 29.45 4140 53.959.18 0 7.23 7840 12.79 6600 26.59 9.18 0 7.04 7853 12.64 5365 40.329.18 4 7.88 7323 18.54 5080^- 43.49 9.18 4 7.81 7233 19.54 4770 46.949.18 B 8.53 6343 29.45 4155 53.78 9.18 B 8.08 6026 32.97 4110 54.289.19 0 7.31 7683 14.53 6465 28.09 9.19 0 6.86 7840 12.79 5400 39.939.19 4 8.02 7320 18.58 4935 45.11 9.19 4 7.65 7410 17.58 4615 48.679.19 B 8.56 6389 28.94 4365 - 51.45 9.19 B 7.95 6051 32.69 4005 55.459.20 0 7.28 7883 12.31 6650 26.03 9.20 0 6.71 7830 12.90 5550 38.269.20 4 8.00 7107 20.95 5450 39.38 9.20 4 7.73 7390 17.80 4990 44.499.20 B 8.55 6300 29.92 4325 51.89 9.20 B 7.85 6151 31.57 4280 52.399.21 0 7.13 7600 15.46 6400 28.81_ 9.21 0 6.67 7710 14.24 5460 39.279.21 4 7.95 7003 22.10 5310 40.93_ 9.21 4 7.70 7170 20.24 4760 47.059.21 B 8.56 6180 31.26 4210 53.17 9.21 B 7.78 6094 32.21 4195 53.349.22 0 7.15 8000 11.01 6505 27.64 9.22 0 6.63 7793 13.31 5415 39.779.22 4 8.12 7253 19.32 5260 41.49 9.22 4 7.60 7237 19.50 4775 46.899.22 B 8.55 6340 29.48 4150 -^53.84 9.22 B 7.69 6023 33.00 4055 54.899.23 0 7.14 7863 12.53 6485 27.86 9.23 0 6.62 7870 12.46 5310 40.939.23 4 8.07 7230 19.58 5045 43.88 9.23 4 7.66 7263 19.21 4790 46.729.23 B 8.48 6143 31.67 4270 52.50 9.23 B 7.79 6386 28.97 3920 56.409.24 0 7.19 7920 11.90 6490 27.81 9.24 0 6.63 7743 13.87 5325 40.779.24 4 7.96 7280 19.02 4915 45.33 9.24 4 7.68 7220 19.69 4740 47.279.24 B 8.50 6294 29.99 4360 51.50 9.24 B 7.77 6354 29.32 4295 52.229.25 0 7.26 7997 11.05 6695 25.53 9.25 0 6.72 8073 10.20 5530 38.499.25 4 7.95 7343 18.32 5000 44.38 9.25 4 7.63 7477 16.83 5140 42.839.25 B 8.63 6337 29.51 4425 -^50.78 9.25 B 7.72 6477 27.96 4215 53.119.26 0 7.18 7960 11.46 6580 26.81 9.26 0 6.63 8053 10.42 5515 38.659.26 4 7.96 7253 19.32 5120 43.05 9.26 4 7.67 7230 19.58 5000 44.389.26 B 8.59 6326 29.64 4250 52.73 9.26 B 7.76 6406 28.75 4240 52.8410.06 B 8.62 6813 24.22 4005 55.45 10.06 B 8.42 6243 30.56 4190 53.3910.06 C 8.78 6085 32.31 3815 57.56 10.06 C 8.62 6108 32.06 3935 56.2310.08 C 8.81 5975 33.54 3905 56.56 10.08 C 8.71 6138 31.73 3885 56.7910.10 C 8.88 5935 33.98 3895 56.67 10.10 C 8.80 5760 35.93 3725 58.5710.14 C 8.75 5863 34.79 3830 57.40 10.14 C 8.76 5843 35.01 3735 58.4510.16 C 8.80 5880 34.59 3820 57.51 10.16 C 8.80 5868 34.73 3760 58.18121Appendix D.^ COD Measurements From Runs A, B and CRUN B COL 5 COL 6DATE TIME • H COD %REM S-COD %REM DATE TIME0pH7.30COD7753%REM13.76S-COD6520%REM27.47• 0 • 12.01 5310 40.93 9.17• 4 20.01 5035 43.99 9.17 4 7.96 7194 19.97 5120 43.05• 8.15 29.86 4085 54.56 9.17 B 8.50 6243 30.56 4190 53.3912.53 5255 41.55 9.18 0 7.25 7770 13.57 6310 29.8118.50 4980 44.61 9.18 4 7.92 7293 18.87 5055 43.7731.99 4040 55.06 9.18 B 8.60 5943 33.89 4195 53.349.71 5470 39.15 9.19 0 7.37 7953 11.53 6565 26.9716.02 4835 46.22 9.19 4 7.91 7457 17.06 4970 44.7232.43 4020 55.28 9.19 B 8.60 6220 30.81 3940 56.1712.79 5640 37.26 9.20 0 7.30 7577 15.72 6410 28.7017.72 5025 44.10 9.20 4 7.94 7280 19.02 5010 44.2729.48 4335 51.78 9.20 B 8.38 6154 31.54 4365 51.4512.57 5130 42.94 9.21 0 7.11 7540 16.13 6025 32.98• 7.64 19.06 4960 44.83 9.21 4 7.87 6983 22.32 5085 43.44• 7.82 • 28.46 4250 52.73 9.21 B 8.46 6217 30.84 4360 51.50• 6.61 • 11.94 5165 42.55 9.22 0 7.07 7683 14.53 6125 31.87• 7.63 • 19.17 4895 45.55 9.22 4 7.86 7033 21.76 5000 44.38• 7.72 • 29.83 3995 55.56 9.22 B 8.52 5980 33.48 3965 55.906.60 1 11.12 5655 37.10 9.23 0 7.11 7790 13.35 6335 29.53• 7.64 19.47 4900 45.49 9.23 4 7.86 7010 22.02 4875 45.77B 7.78 27.86 4045 55.01 9.23 B 8.47 5917 34.18 3835 57.34• 0 6.63 12.27 5205 42.10 9.24 0 7.16 7763 13.64 6155 31.54• 4 7.62 18.54 4795 46.66 9.24 4 7.78 7037 21.73 4850 46.05• B 7.75 27.67 4270 52.50 9.24 B 8.47 5951 33.80 4230 52.950 6.69 10.72 5585 37.88 9.25 0 7.21 7963 11.42 6290 30.03• 4 7.61 16.61 5145 42.77 9.25 4 7.73 7143 20.54 5145 42.77• B 7.65 • 27.51 4400 51.06 9.25 B 8.45 5897 34.41 4140 53.95• 0 6.60 11.01 5470 39.15 9.26 0 7.17 7857 12.61 6360 29.25• 4 7.63 16.83 5125 42.99 9.26 4 7.79 7137 20.62 4985 44.55• B 7.76 • 27.73 4360 51.50 9.26 B 8.48 6034 32.88 3930 56.28B 8.41 • 25.22 4145 53.89 10.06 B 8.56 6100 32.15 3815 57.56C 8.62 31.28 3825 57.45 10.06 C 8.80 5945 33.87 3650 59.40C 8.71 32.48 3875 56.90 10.08 C 8.85 6038 32.84 3905 56.56C 8.78 5773 35.79 3970 55.84 10.10 C 8.92 5830 35.15 3785 57.90• C 8.73 5780 35.71 3660 59.29 10.14 C 8.82 5915 34.20 3835 57.348.72 6040 32.81 3690 58.95 10.16 C 8.83 5940 33.93 3855 57.12122Appendix D.^ COD Measurements From Runs A, B and CRUN C COL 1_COL 2DATE TIME pH COD % REM S-COD % REM DATE TIME pH COD % REM S-COD % REM11.26 B 6.50 4733 31.00 2880 58.02 11.26 B 8.00 4215 38.55 2860 58.3111.27 B 6.34 4820 29.74 2725 60.28 11.27 B 7.97 4318 37.06 3047 55.5811.28 B 6.45 4777 30.37 2820 58.89 11.28 B 8.02 4191 38.90 2930 57.2911.29 B 6.65 4766 30.53 2735 60.13 11.29 B 8.05 4321 37.01 2845 58.5312.01 B 6.66 4658 32.11 2785 59.40 12.01 B 8.00 4063 40.78 3020 55.9812.02 4 6.61 5223 23.86 3280 52.19 12.02 4 7.93 4903 28.52 3360 51.0212.02 A 6.42 4755 30.69 2660 61.22 12.02 A 8.00 4435 35.35 2685 60.8612.02 B 6.56 4603 32.91 2415 64.80 12.02 B 8.01 4083 40.49 2715 60.4212.03 4 6.73 5230 23.76 3155 54.01 12.03 4 8.06 5015 26.90 3250 52.6212.03 A 6.62 4643 32.33 2610 61.95 12.03 A 8.02 4540 33.82 2830 58.7512.03 B 6.50 4465 34.91 2290 66.62 12.03 B 7.97 4010 41.55 2890 57.8712.04 4 6.77 5491 19.96 3230 52.92 12.04 4 8.10 5103 25.61 3310 51.7512.04 A 6.63 4690 31.63 2530 63.12 12.04 A 8.04 4563 33.48 2865 58.2412.04 B 6.76 4572 33.35 2450 64.29 12.04 B 8.05 4050 40.96 2900 57.7312.05 4 6.74 5409 21.15 3405 50.36 12.05 4 8.09 5100 25.66 3355 51.0912.05 A 6.67 4755 30.69 2500 63.56 12.05 A 8.10 4581 33.22 2815 58.9712.05 B 6.68 4560 33.53 2355 65.67 12.05 B 8.05 4032 41.22 2770 59.6212.11 C 8.67 4373 36.25 2530 63.1212.13 C 8.65 4188 38.95 2385 65.2312.15 C 8.66 4235 38.27 2445 64.3612.17 C 8.71 4493 34.50 2660 61.2212.19 C 8.67 4539 33.83 2530 63.12123Appendix D.^ COD Measurements From Runs A, B and CRUN C COL 3 COL 4DATE TIME pH COD % REM S-COD % REM DATE TIME pH COD % REM S-COD % REM11.26 B 8.53 4518 34.14 2780 59.48 11.26 B 7.50 4442 35.24 2610 61.9511.27 8.58 is 34.40 2854 58.40 11.27 B 7.51 33.35 2685 60.868.54 33.04 3095 11.28 B 7.41 2940 57.148.52 36.08 3005 11.29 B 7.50 5 2910 57.5812.01 38.12 3055 12.01 B 2865 58.2412.02 3490 12.02 4•3200 53.352920 12.02 A 59.482755 12.02 B 62.613355 12.03 4 50.872900 12.03 A 4400 • 60.502660 12.03 B 61.5212.04 4 53.1312.04 59.9112.04 61.1520.41 12.05 4 21.68 50.7333.92 12.05 A 59.1138.64 12.05 61.8138.9537.7636.73C 37.4212.19 36.53124Appendix D.^ COD Measurements From Runs A, B and CRUN C COL 5 COL 6DATE TIME pH COD % REM S-COD % REM DATE TIME pH COD % REM S-COD % REM11.26 B 8.72 4673 31.88 3060 55.39 11.26 B 8.60 4539 33.83 2930 57.2911.27 B 8.74 4748 30.79 3010 56.12 11.27 B 8.67 4693 31.60 2930 57.2911.28 B 8.66 4809 29.91 3210 53.21 11.28 B 8.59 4760 30.62 3180 53.6411.29 B 8.65 4819 29.75 3125 54.45 11.29 B 8.56 4702 31.46 3100 54.8112.01 B 8.73 4650 32.22 3005 56.20 12.01 B 8.62 4305 37.24 3025 55.9012.02 4 8.21 5133 25.17 3475 49.34 12.02 4 8.14 5220 23.91 3645 46.8712.02 A 8.70 4505 34.33 2910 57.58 12.02 A 8.64 4538 33.86 2845 58.5312.02 B 8.73 4370 36.30 2705 60.57 12.02 B 8.65 4290 37.46 2885 57.9412.03 4 8.14 5081 25.94 3395 50.51 12.03 4 8.08 5116 25.42 3520 48.6912.03 A 8.71 4658 32.11 2905 57.65 12.03 A 8.61 4643 32.33 2920 57.4312.03 B 8.75 4348 36.62 2775 59.55 12.03 B 8.62 4288 37.49 2795 59.2612.04 4 8.26 5093 25.76 3380 50.73 12.04 4 8.21 5310 22.59 3370 50.8712.04 A 8.68 4741 30.89 2925 57.36 12.04 A 8.59 4699 31.50 2935 57.2212.04 B 8.74 4490 34.55 2835 58.67 12.04 B 8.66 4415 35.64 2860 58.3112.05 4 8.23 5280 23.03 3470 49.42 12.05 4 8.17 5123 25.32 3550 48.2512.05 A 8.70 4713 31.30 3070 55.25 12.05 A 8.61 4575 33.31 2890 57.8712.05 B 8.74 4472 34.81 2715 60.42 12.05 B 8.65 4402 35.83 2795 59.2612.11 C 9.01 4510 34.26 2430 64.58 12.11 C 8.90 4645 32.29 2245 67.2712.13 C 8.86 4578 33.27 2465 64.07 12.13 C 8.72 4583 33.19 2380 65.3112.15 C 8.94 4443 35.23 2810 59.04 12.15 C 8.83 4735 30.98 2670 61.0812.17 C 8.96 4605 32.87 2955 56.92 12.17 C 8.82 4721 31.18 3030 55.8312.19 C 8.91 4587 33.13 2940 57.14 12.19 C 8.84 4742 30.87 2964 56.7912.19 E 8.98 4563 33.48 2934 57.23 12.19 E 8.93 4539 33.83 2790 59.3312.23 E 9.10 4812 29.85 2922 57.41 12.23 E 9.05 4560 33.53 2964 56.7912.27 E 9.00 4948 27.87 3024 55.92 12.27 E 8.97 4449 35.15 2802 59.1512.31 E 9.10 4899 28.59 3210 53.21 12.31 E 9.01 4887 28.76 2988 56.441.04 E 9.00 4501 34.39 3180 53.64 1.04 E 8.91 4398 35.89 3096 54.87125


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