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Treatment of high ammonia concentration landfill leachate with an anaerobic filter and rotating biological… Henderson, J. Paul 1994

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TREATMENT OF HIGH AMMONIA CONCENTRATION LANDFILL LEACHATE WITH AN ANAEROBICFILTER AND ROTATING BIOLOGICAL CONTACTOR (RBC)byJ. PAUL HENDERSON, P.ENG.B.A.Sc, The University of British Columbia, 1989A THESIS SUBMITTED IN PARTIAL FULFILMENT OFTHE REQUIREMENTS FOR THE DEGREE OFMASTER OF APPLIED SCIENCEinTHE FACULTY OF GRADUATE STUDIESDepartment of Civil EngineeringWe accept this thesis as conformingto the required standardTHE UNIVERSITY OF BRITISH COLUMBIAApril 1994© J. Paul Henderson, 1994In presenting this thesis in partial fulfilment of the requirementsfor an advanceddegree at the University of British Columbia, I agree that the Library shall make itfreely available for reference and study. I further agree that permission for extensivecopying of this thesis for scholarly purposes may be granted by the head of mydepartment or by his or her representatives. It is understood that copying orpublication of this thesis for financial gain shall not be allowed without my writtenpermission.(Signature)______________________Department of Civil EngineeringThe University of British ColumbiaVancouver, CanadaDateApril 20, 1994DE-6 (2J88)iiABSTRACTLandfill leachate discharge potentially results in degradation of the receivingenvironment. One of the primary leachate contaminants of concern is nitrogen,which in the form of ammonia is toxic to aquatic life, and in the form of nitratemay cause eutrophication of the receiving water body. For these reasons, it isoften desirable to totally remove nitrogen from leachate prior to discharge tothe environment.Biological nitrogen removal appears to be the most practical method of removingnitrogen from leachate. Rotating biological contactors (RBC’s), in particular,have been shown to effectively nitrify high ammonia leachate. If sufficientcarbon is available, anaerobic biological treatment processes have been shown toeffectively denitrify aerobically treated leachate.This thesis investigates the use of a predenitrifying anaerobic filter and arotating biological contactor to remove nitrogen from a high ammoniaconcentration leachate from a municipal solid waste landfill in Kaohsiung,Republic of China. The primary objective of the research was to determine theeffects of high ammonia concentration on RBC ammonia loading and removal.Secondary objectives include removing organics and metals from the leachate.The research indicated that 97% ammonia removal from high ammonia leachate (mean2,140 mg/L) can be achieved at RBC loading rates up to 1.5 g/m2/day. At higherloading rates, ammonia removal was inhibited.Nitrogen removal for the system averaged 66%, including an estimated 54% in theRBC. Nitrogen removal in the RBC was either the result of simultaneousnitrification/denitrification or air stripping of ammonia in combination withnitrification. Both alkalinity consumption and COD removal results support theexplanation that simultaneous nitrification/denitrification (potentially aerobiciiidenitrification) occurred, but since RBC off—gasses were not monitored, neithertheory can be confirmed.BOD and COD removal in the system averaged 92% and 49%, respectively. COD:BODremoval was 3.7:1.The system did not effectively remove metals. Overall removal of dissolvedmetals ranged from —19% for nickel to 59% for manganese. Organic complexing ofthe metals most probably resulted in low removals.ivTABLE OF CONTENTSABSTRACT iiTABLE OF CONTENTS ivLIST OF TABLES viiLIST OF FIGURES viiiLIST OF EQUATIONS AND EXAMPLES ixACKNOWLEDGMENTS x1. INTRODUCTION 12. LITERATURE REVIEW 32.1 LANDFILL LEACHATE CHARACTERISTICS, GENERATION AND DETRIMENTALEFFECTS 32.1.1 Leachate Characteristics 32.1.2 Leachate Generation 62.1.3 Detrimental Effects of Leachate 62.2 THEORY OF BIOLOGICAL NITROGEN REMOVAL 62.3 LEACHATE TREATMENT 102.3.1 Biological Treatment Aerobic Treatment 11Suspended Growth Systems 12Fixed Film Systems 16Trickling Filters 17Rotating Biological Contactors (RBC’s) Anaerobic Treatment Biological Metal Removal 282.3.2 Physical/Chemical Treatment Recycle/Recirculation Land Application 302.3.2.3 Air Stripping 312.3.2.4 Adsorption 312.3.2.5 Chemical Coagulation/Precipitation 322.4 LITERATURE REVIEW CONCLUSIONS AND EXPERIMENTAL OBJECTIVES . . . 333. SITE DESCRIPTION 35V4. EXPERIMENTAL DESIGN .5. ANALYTICAL PARAMETERS AND METHODS5.1 BOD (BIOCHEMICAL OXYGEN DEMAND)5.2 COD (CHEMICAL OXYGEN DEMAND)5.3 AMMONIA5.4 pH5.5 METALS5.6 FLOW5.7 ANIONS5.8 RBC SPEED5.9 SUSPENDED SOLIDS5.10 TKN (Total Kjeldahl Nitrogen)5.11 TOTAL ALKALINITY6. RESULTS6.1 LEACHATE, FILTER EFFLUENT AND RBC EFFLUENT6.2 FLOW6.3 MASS BALANCE6.4 BOD and COD REMOVAL6.5 NITROGEN6.5.1 Effect of Hydraulic Retention Time on6.5.2 Inhibition of Nitrification6.5.3 Nitrogen Removal6.6 METALS6.7 pH6.8 TOTAL ALKALINITY6.9 ANIONS6.10 RBC SPEED6.11 SUSPENDED SOLIDS7. SUMMARY OF RESULTS8. CONCLUSIONS991019. RECOMMENDATIONS 102REFERENCES 103APPENDIX 1: DA LIAO LANDFILL PLAN 10940454546474747484848484949CHARACTERISTICSAmmonia Removal505051• . . . 535965707276809295969898APPENDIX 2: AMMONIA PROBE SAMPLE CALCULATIONS AND OUTPUT110viAPPENDIX 3: KAOHSIUNG DAILY PRECIPITATION DATA 112APPENDIX 4: LEACHATE, FILTER EFFLUENT AND RBC EFFLUENT DATA 113APPENDIX 5: BOD AND COD DATA 120APPENDIX 6: NITROGEN DATA 122APPENDIX 7: METAL DATA 123APPENDIX 8: ION CHROMATOGRAPH SAMPLE OUTPUT 125viiLIST OF TABLESTABLE 1:TABLE 2:TABLE 3:TABLE 4:TABLE 5:TABLE 6:TABLE 7:TABLE 8:TABLE 9:TABLE 10:TABLE 11:TABLE 12:TABLE 13:TABLE 14:TABLE 15:TABLE 16:TABLE 17:TABLE 18:TABLE 19:TABLE 20:TABLE 21:LANDFILL STABILIZATION STAGESCHARACTERISTICS OF LANDFILL LEACHATEFACTORS AFFECTING NITRIFICATIONACTIVATED SLUDGE SYSTEM PARAMETERSAERATED LAGOON METAL REMOVALTRICKLING FILTER DESIGN PARAMETERSAMMONIA AND ORGANIC LOADING RATES FOR RBCRBC METAL REMOVALANAEROBIC LEACHATE TREATMENTPRECIPITATION AND TEMPERATURE DATA FOR KAOHSIUNGDA LIAO LANDFILL WATER BALANCEANALYTICAL PARAMETERS AND MONITORING FREQUENCY .LEACHATE CHARACTERISTICSANAEROBIC FILTER AND RBC EFFLUENT CHARACTERISTICSBOD AND COD REMOVALNITROGEN AND AMMONIA REMOVALOVERALL METAL REMOVALEFFECT OF pH ON METAL COMPOUND SOLUBILITYRBC EFFLUENT METAL LEVELS COMPARED TO B.C. POLLUTIONCONTROL OBJECTIVESTOTAL ALKALINITYANION DATA457131617192527383946505160668090919597viiiFIGURE 4:FIGURE 5:FIGURE 6:FIGURE 7:FIGURE 8:FIGURE 9:FIGURE 10:FIGURE 11:FIGURE 12:FIGURE 13:FIGURE 14:FIGURE 15:FIGURE 16:FIGURE 17:FIGURE 18:FIGURE 19:FIGURE 20:FIGURE 21:FIGURE 22:FIGURE 23:FIGURE 24:FIGURE 25:FIGURE 26:6869717374778182838485• 86• 87LIST OF FIGURESFIGURE 1: KAOHSIUNG LOCATION PLANFIGURE 2: LANDFILL SITE PLANFIGURE 3: ANAEROBIC FILTER/ACTIVATED SLUDGE SYSTEM SCHEMATIC363741435256575862636467ANAEROBIC FILTER/RBC SYSTEM SCHEMATICSYSTEM FLOWANAEROBIC FILTER COD REMOVALANAEROBIC FILTER NITROGEN REMOVAL . .ANAEROBIC FILTER IRON REMOVALLEACHATE AND RBC EFFLUENT BODLEACHATE AND RBC EFFLUENT CODBOD AND COD REMOVAL EFFICIENCYLEACHATE AND RBC EFFLUENT AMMONIA .AMMONIA REMOVALAMMONIA MASS REMOVALAMMONIA REMOVAL VS INFLUENT FLOW . .AMMONIA REMOVAL VS TOTAL FLOWRBC EFFLUENT NITRITE AND NITRATE . •RBC NITROGEN REMOVALCHROMIUM TREATMENT EFFICIENCYCOPPER TREATMENT EFFICIENCYIRON TREATMENT EFFICIENCYMANGANESE TREATMENT EFFICIENCYNICKEL TREATMENT EFFICIENCYLEAD TREATMENT EFFICIENCYZINC TREATMENT EFFICIENCYSYSTEM pH 93ixLIST OF EQUATIONS AND EXAMPLESEQUATION 1: LANDFILL WATER BALANCE 6EQUATION 2: NITRIFICATION 7EQUATION 3: HALDANE INHIBITION MODEL 8EQUATION 4: DENITRIFICATION 9EQUATION 5: AEROBIC NITRIFICATION/DENITRIFICATION 10EQUATION 6: ARRHENIUS EQUATION 20EQUATION 7: AMMONIA/AMMONIUM EQUILIBRIUM EQUATION 31EQUATION 8: MASS BALANCE CALCULATIONS 53EQUATION 9: ALKALINITY RELATIONSHIP 94EQUATION 10: CARBONIC ACID EQUILIBRIUM RELATIONSHIP 94EXAMPLE 1: MASS BALANCE SAMPLE CALCULATIONS 54xACKNOWLEDGMENTSI would like to thank my supervisor Professor Jim Atwater for his help andguidance on this thesis over the last three years. I would also like to thankProfessor Donald Mavinic and Doctor David Forgie for reviewing my draft thesis.The project would not have been possible without the support and assistance ofProfessor Yang Lei of the National Sun Yat Sen University in Kaohsiung, Republicof China, and Professor Lin Cheng—Fang of the National Taiwan University inTaipei, Republic of China.I would also like to thank the research assistants and students of the NationalSun Yat Sen University Department of Marine Environment, Chen Xiao Hua, Zhen WenXi, Cai Hui Mei, Zhen Ren Hao, Zhuang Mei Ying, Chen Hong Liang, and the entire1992 4th Year Marine Environmental Engineering Class, whose help, patience andhospitality made my stay at the National Sun Yat Sen University a greatexperience.My thanks also go to John Evans and Brian Davies of the City of Vancouver forbeing flexible enough to allow me to undertake and complete this project, and toGwyn Dryer for typing a large portion of the text of my thesis.Finally, I would like to thank Nikki who has put—up with me as I have struggledto complete my Master’s degree.Partial funding for this project was received from the National Science andEngineering Research Council of Canada. The majority of the funding was providedby Professors Yang Lei and Lin Cheng—Fang as part of a Taiwan EnvironmentalProtection Agency research grant.11. INTRODUCTIONSanitary landfilling is the most common method of disposing of municipal solidwaste in North America and much of the rest of the world. Landfilling maydetrimentally affect the local environment through the production and dischargeof contaminants to the atmosphere and land. A major source of contaminants isthe discharge of leachate to ground or surface water.Landfill leachate is generated by the percolation of water through refuse. Theorganic and inorganic decomposition products of the waste dissolve in the waterproducing an odorous, dark liquid known as leachate. Major contaminants ofconcern include dissolved organic material, ammonia, and metals.For older landfill leachates, the primary contaminant of concern is ammonia,which is toxic to fish, and if converted to nitrate may result in eutrophicationof the receiving environment. For these reasons, complete nitrogen removal fromleachate is often desirable.Several authors have shown that the rotating biological contactor (RBC) iseffective at converting leachate ammonia to nitrate (Peddie and Atwater, 1985;Hartmann and Hoffmann, 1990; Hosomi et al., 1991; Masuda et al., 1991). Undercertain conditions, RBC’s may also simultaneously remove nitrogen from the system(Masuda et al., 1991; Hosomi et al., 1991, Atwater and Bradshaw, 1981). Ammoniahas also been shown to be toxic to ammonia oxidizing bacteria at high influentconcentrations (Azevedo, 1993), but the RBC process may be more resistant toammonia toxicity than suspended growth processes (Hartmann and Hoffmann, 1990).To fully remove nitrogen from wastewater, an anoxic basin is generally used. Themost common method is to either use a basin prior to the aerobic reactor withrecycle or a basin following the aerobic basin. In each case, supplementalcarbon is generally added to provide an energy source for denitrification. Ifsufficient carbon is available, predenitrification may be possible without2supplemental carbon addition.The leachate used in this experiment has very high ammonia concentration withrelatively high COD. Therefore, it was hypothesized that a process train of apredenitrifying anaerobic filter followed by an RBC may be effective in removingnitrogen from the leachate. The primary objective of the experiment was to usethis process train to investigate the effects of high ammonia concentration onloading rates and removal efficiencies. Secondary objectives included removingorganics and metals from the leachate.The experimental work described in this thesis was conducted at the National SunYat Sen University, Department of Marine Environment, Kaohsiung, Taiwan, Republicof China, during the winter and spring of 1991/1992.32. LITERATURE REVIEW2.1 LANDFILL LEACHATE CHARACTERISTICS, GENERATION AND DETRIMENTAL EFFECTS2.1.1 Leachate CharacteristicsThe characteristics of landfill leachate vary from site to site and over time atan individual site. The variation between sites is based on differences inclimatic conditions, hydrogeological conditions, and waste composition (Pohiandet al., 1985). The variation over time at an individual site is a result of thedegree of stabilization of the waste.Pohiand et al. (1985) have divided the stabilization of landfills into a numberof discreet stages. A summary of those stages is given in Table 1.Due to the continuous rather than batch nature of landfilling, and the length oftime required to reach Phase V (up to 20 years; Pohiand et al., 1985), it iscommon to describe leachate as either acidic or methanogenic (Ehrig, 1985), oras young, mature, aging or old based on the BOD:COD ratio (young = 0.7, mature= 0.5, aging = 0.3, old = 0.1) (Henry et al., 1987). The length of timeassociated with the transition from young to old after the start up of a landfillis typically from 2 — 10 years depending on circumstances (Forgie, 1988a).4TABLE 1: LANDFILL STABILIZATION STAGESPhase I: Initial Adjustment— Landfill is under aerobic conditions prior to the depletion of all theentrained air in the refuse— No leachate generation because the refuse has not reached fieldcapacityPhase II: Transition— Landfill is in transition from aerobic to anaerobic stage— Leachate production beginsPhase III: Acid Formation— Volatile organic fatty acids are the primary component of COD resulting ina high biologically oxidizable organic fraction, and consequently a highBOD:COD ratio.— Leachate is characterized by low pH— Metals tend to be mobilePhase IV: Methane Fermentation— Volatile organic fatty acids are converted to methane and carbon dioxide— Leachate is characterized by neutral to slightly alkaline pH— Reducing environment within the landfill results in thedisappearance of nitrates and suiphates.— Metals are complexed with suiphide and organic ligands andprecipitated from solution— Total organic strength (COD) significantly lower— Humic and fulvic compounds dominate COD resulting in a low biologicallyoxidizable fraction, and consequently a low BOD:COD ratio.Phase V: Final Maturation/Stabilization— Relative dormancy— Gas production all but ceases— Settling ceases— Recalcitrant organics may be slowly converted to humic substances capableof forming soluble complexes with heavy metals, remobilizing themSOURCE: Pohland et al., 19855Expected characteristics of acid phase and methanogenic phase leachate as wellas example characteristics are provided in Table 2.TABLE 2: CHARACTERISTICS OF LANDFILL LEACHATEParameter Expected Expected Example ExampleAcidic Methanogenic Acidic Methanogenic1 2 3 4pH 6.1 8 5.8 8.1BOD (mg/L) 13,000 180 9,660 100COD (mg/L) 22,000 3000 13,780 1,000BOD:COD 0.6 0.06 0.7 0.1NH3—N (mg/L) 750 750 42 340Total N (mg/L) 1,250 1,250 212 340Total P (mg/L) 6 6 0.77 0.2Cd (ig/L) 5 6 6 0.10 14Ni (j.ig/L) 200 200 1080 220Pb (jig/L) 90 90 — <100Cr (ig/L) 300 300 — 60Cu (ig/L) 80 80 190 120Mn (mg/L) 25 0.7 — —Fe (mg/L) 780 15 1070 11Zn (mg/L) 5 0.6 5.04 0.34SOURCES/NOTES:1. Ehrig (1989a)2. Ehrig (1989a)3. Henry et al. (1987)4. Knox (1985)5. Metals are totals for example acidic, but not stated for the rest.Note that although the expected parameter values for acidic and methanogenicleachate described by Ehrig (1989a) are not exactly the same as the exampleleachates from Henry et al. (1987) and Knox (1985) major parameter values tendto be similar (e.g. pH, BOD, COD, BOD:COD ratio). Variations from the expectedvalues are a result of site specific conditions.62.1.2 Leachate GenerationLeachate generation depends on the amount of moisture infiltrating into alandfill.Various models are used to calculate leachate flow from a landfill. They are allbased on creating a water balance for the landfill. A simple water balance,which assumes groundwater flow and surface run—off to be zero, is given in Jasperet al. (1985a) and is shown in Equation 1.EQUATION 1: LANDFILL WATER BALANCELeachate Production = Precipitation + Refuse Input— Refuse Uptake — EvapotranspirationCalculating the rate of leachate production is necessary to size treatmentfacilities. A commonly used model for calculating leachate production rate isthe HELP model, which was developed in the United States and is described inFarquhar (1989).2.1.3 Detrimental Effects of LeachateIf landfill leachate is discharged directly to a receiving body (ground orsurface water), the potential detrimental effects include toxic effects on fishand other aquatic organisms (Cameron and Koch, 1980), and contamination of thegroundwater or surface water with organic or inorganic contaminants.Consequently, prior to discharge, treatment to remove both organic and inorganicconstituents is required.2.2 THEORY OF BIOLOGICAL NITROGEN REMOVALNitrogen is a critical component of living organisms. On average, nitrogen makesup 12—14% of cell protein (Barnes and Bliss, 1983). When organisms die or theyexcrete waste products, the nitrogen is released into the environment.A degradation product of proteins is ammonia. In solution, ammonia is either inionic form (ammonium) or dissolved gaseous form (ammonia). At pH 7 and 20 °C,7approximately 100% of ammonia is in the ammonium ion form. At H 11 and 20 °C,approximately 100% of ammonia is in dissolved gaseous ammonia form (Viessman andHammer, 1985). Landfill leachate is generally in the pH range of 4.5 to 8(Ehrig, 1989a). Therefore, unless the pH is artificially adjusted, the majorityof ammonia will be in the ammonium ion form. In this thesis, the term ammonia(or the symbol NH3) is used to refer to the sum of ammonium ion and free ammonia.Under aerobic conditions, ammonia is converted to nitrate through the reactionsshown in Equation 2 collectively termed nitrification.Step 2N02 + 0.5 02 —>SOURCE: Barnes and Bliss, 1983The conversion is done by autotrophic organisms (Step 1 Nitrosomas, Step 2Nitrobacter), which use the energy generated for synthesis and other lifeprocesses. These organisms, by definition, use inorganic carbon rather thanorganic carbon.Nitrification can be affected by many environmental conditions. These factorsare shown in Table 3.TABLE 3: FACTORS AFFECTING NITRIFICATIONReduced temperaturesLow 02 valuespH values outside the optimum7.9 — 8.2 Nitrosomas7.2 — 7.6 NitrobacterFree ammonia (unionized)Free nitrous acidShock nitrogen loadingSOURCE: Ehrig, 1985EQUATION 2: NITRIFICATIONStep 1NH4 + 1.5 02 —> N02 + H2O + 2H + (240 — 350 kJ)NO3 + (65 — 90 kJ)Note that the pH optimum for Nitrosomas (ammonia to nitrite) is higher than thepH optimum for Nitrobacter (nitrite to nitrate). Alleman (1984) suggests thatSNitrobacter may be selectively inhibited by pH, low temperature, low oxygenpartial pressure, low carbon dioxide partial pressure, free ammonia, and processover—loading. This would result in prolonged nitrite build—up.Gee et al. (1990) found that inhibition of the rate of oxidation of ammonia tonitrite in batch experiments was successfully modelled by the Haldane inhibitionmodel which is presented in Equation 3:EQUATION 3: HALDANE INHIBITION MODELr = kXSSk5 + S +s2/kr5 = substrate utilization rate (M/L3T)k = maximum substrate utilization rate (T’)k8 = half velocity coefficient (M/L3)k = inhibition coefficient (M/L3)X = concentration of microbial species carrying outoxidation (M/L3)S = substrate concentration (M/L3)The conversion of nitrite to nitrate was not effectively modelled by the Haldaneinhibition model. It was observed that nitrite oxidation was inhibited by thesimultaneous presence of nitrite and ammonia rather than simply nitrite.In a continuous flow activated sludge experiment, Azevedo (1993) found fullnitrification could be achieved up to influent ammonia— N concentration of 1,500mg/L, but that at 2,000 mg/L ammonia—N effluent ammonia levels increased to 700mg/L. This occurred at both 10 day and 20 day aerobic solids retention time(SRT). Azevedo (1993) found an accumulation of nitrite began to occur atinfluent ammonia—N levels of 600 mg/L. Turk and Mavinic (1989) found nitritebuild—up began to occur at free ammonia—N levels of 5 mg/L or total ammonia—Nconcentration of 90 mg/L at pH 8. Turk and Mavinic (1989) could not maintain anitrite build—up.As a result of nitrification, hydrogen ions are released (see Equation 2; Step1). If the leachate is not effectively buffered, a reduction in pH will result9leading to suboptimal conditions and reduced nitrification. To maintain pHbalance, the theoretical alkalinity demand is 7.14 mg alkalinity as CaCO3 per mgNH3-N oxidized.In many cases, nitrified wastewater is released directly to a receiving body, butsince nitrogen is an essential nutrient, its release may stimulate aquatic plantgrowth, which may be undesirable. High nitrate levels in drinking water may causeinfant methaemoglobinaemia (blue baby); blockage of haemoglobin with nitriteions, which prevent oxygen transport and suffocate the infant (Barnes and Bliss,1983). Therefore, complete nitrogen removal from the leachate is sometimesappropriate.Under anoxic conditions, nitrate ions can be used as terminal electron acceptorsby facultative, heterotrophic, microorganisms (Barnes and Bliss, 1983). Thenitrate ions are thus converted to nitrogen gas by the reactions shown inEquation 4 in a process called denitrification.EQUATION 4: DENITRIFICATIONStep 1N03 + 1/3 CH3O -> N02 + 1/3 CO2 + 2/3 H20Step 2N02 + 1/2 CH3OSOURCE: Barnes and Bliss, 1983In Equation 4, methanol is shown as the electron donor, but other organicsubstrates may also be used. Since hydroxide ions are produced duringdenitrification, an increase in alkalinity results. The theoretical increase inalkalinity due to denitrification is 3.57 mg CaCO3 per mg N.The first step in denitrification involves converting nitrate back to nitrite.Turk and Mavinic (1989) found that if the second step of nitrification wasskipped (conversion of nitrite to nitrate) the overallnitrification/denitrification reaction could be improved resulting in 1) 40%—> N2 + 1/2 CO2 + 1/2 H20 + OH10reduction in COD demand, 2) 63% increase in denitrification rate, 3) 300%decrease in sludge production from anaerobic growth. They could not maintain abuild—up of nitrite, finding instead, that over time, the oxidation of nitriteto nitrate in the reactor could not be prevented.Robertson and Kuenen (1984) showed that certain bacteria, for example Thiospaerapantotropha, are capable of simultaneously nitrifying and denitrifying ammoniawastewater under fully aerobic conditions. These bacteria are heterotrophicnitrifiers and aerobic denitrifiers, and are able to simultaneously use nitriteand oxygen as terminal electron acceptors.Robertson and Kuenen (1984) showed aerobic denitrification occurred by bothmeasuring nitrogen gas production from an aerobic reactor and measuring theeffects of adding denitrifying inhibitors. This reaction is still contingent onthe presence of a suitable electron donor (e.g. acetate). The aerobicsimultaneous nitrification/denitrification reaction is shown in Equation 5.EQUATION 5: AEROBIC NITRIFICATION/DENITRIFICATIONNH4 -, NH2O -‘ N02 -, N20 4 N2SOURCE: Robertson et al., 1988It should be noted that Equation 5 does not include the organic electron donornecessary for the reaction to proceed. Also, since the reaction does not proceedto nitrate, the COD requirement should be 40% less than conventionaldenitrification.Robertson and Kuenen (1984) and Robertson et al. (1988) conducted their researchat a reactor temperature of 37 °C. The reason for using such a high temperatureis not provided in their papers.2.3 LEACHATE TREATMENTDue to the complexity of landfill leachate, to completely treat leachate, prior11to discharge to the environment, generally requires a multi—component processtrain consisting of both biological and physical/chemical processes (Beszeditsand Silbert, 1990). The following review explores the benefits and draw—backsof a wide range of processes.2.3.1 Biological TreatmentBiological treatment methods rely on heterotrophic and autotrophic microorganismsto, by some means, render contaminants in leachate innocuous, either by removingthem completely from the leachate or by binding them into sludge so that they canbe separated and removed. There are two basic forms of biological treatment usedin treating landfill leachate; aerobic and anaerobic treatment systems. Aerobic TreatmentAerobic leachate treatment is based on the theory that, in the presence ofoxygen, aerobic heterotrophic microorganisms will use the organic substratespresent as a food source for growth and energy, and convert them to carbondioxide and water. Consequently, the BOD and COD of the leachate will bereduced. Other leachate contaminants of concern (ammonia, and metals) may alsobe removed from the wastewater either through assimilation, oxidation orprecipitation. Marie et al. (1985) found a BOD:N of 20 was required toeffectively remove ammonia from leachate through assimilation. Under favourableconditions, ammonia is oxidized to nitrate by chemo—autotrophic organisms, andmetals are removed through the formation and precipitation of insoluble metaloxides and hydroxides (Henry, 1985).Aerobic treatment is most appropriate in the BOD:COD range of approximately 0.1 —0.4 (Forgie, 1988c). In this range, oxidation of ammonia to nitrate can beachieved, and biodegradable organics are still present. Below a BOD:COD ratioof approximately 0.1, the majority of biodegradable organics have been removed,and aerobic treatment would only be considered for ammonia removal. For BOD:CODratios greater than approximately 0.4, less energy intensive anaerobic treatment12is more appropriate (Forgie, 1988c).The other requirements for aerobic treatment are adequate nutrients (phosphorousaddition to achieve a BOD:P ratio of 100:0.5 is often required (Henry, 1985;Ehrig, 1985), and sufficiently low levels of toxic substances. Various authorshave discussed toxicity with respect to specific processes, and therefore,toxicity will be dealt with when describing individual processes.Aerobic biological processes consist of either suspended growth systems(activated sludge, extended aeration and aerated lagoons) or fixed film systems(trickling filter and rotating biological contactors) (Forgie, 1988a). Insuspended growth systems, the microorganisms are suspended in the wastewater, ina “floc”, either mechanically or with air bubbles. In a fixed film system, themicroorganisms are attached to inert media and are placed in contact with theleachate.Suspended Growth SystemsIn the activated sludge system, microorganisms are suspended in a “floc” eithermechanically or with bubbles. The unique feature of an activated sludge systemis that sludge is recycled and “wasted” to control the sludge concentration and“sludge age” within the reactor. The variables which are controlled in anactivated sludge system are aeration rate, sludge recirculation rate, sludgewasting rate, and influent flow. These variables determine loading andoperational parameters for the system including BOO loading (kg/m3/day and kg/kgmlvss/day), sludge age, hydraulic retention time, and BOO removal. The typicalsystem parameter values for conventional activated sludge (tapered aeration)wastewater treatment plants are shown in Table 4.13TABLE 4: ACTIVATED SLUDGE SYSTEM PARAMETERSBOD LoadingVolume 0.5 - 0.65 kg/m3/dayF/M * 0.2 - 0.5 kg/kgSludge Age 5 — 15 daysHydraulic Retention 6 — 7.5 hoursSludge Recycle 30%BOD Removal 80 — 90%Notes:* F/M = Food to microorganism ratio or BOD to MLVSS ratio.SOURCE: Viessman and Hammer, 1985.Extended aeration systems are simply a variation of activated sludge systems,providing lower loading rates (0.15 — 0.5 kg BOD/m3/day), and higher hydraulicretention times (20 — 30 hours, Viessman and Hammer, 1985). This results in lesssludge production because the microorganisms are in an endogenous state.Aerated lagoon systems are similar to activated sludge systems except that norecycle is used. Therefore, lower loading rates and less system control areachievable. Municipal wastewater hydraulic retention times for aerated lagoonsare typically around 10 days depending on temperature.Activated sludge has been used extensively to treat landfill leachate.Albers et al. (1986) used activated sludge to treat landfill leachate effluentfrom an anoxic reactor with COD up to 15,000 mg/L, and influent TKN up to 2,000mg/L. They found that, to ensure proper sludge settling, phosphorous additionwas necessary. For full nitrification, bicarbonate addition (HC03) was necessaryto achieve an alkalinity as CaCO3:TKN ratio of at least 6:1.The plant was run with predenitrification and 500% effluent recycle. EffluentCOD was approximately 1500, BOD was less than 25 mg/L and ammonia was less than20 mg/L. Effluent nitrate—N was reduced from approximately 1000 mg/L toapproximately 200 mg/L by mixing 7 parts anaerobic effluent to 3 parts rawleachate feeding the activated sludge plant. This raised the influent COD from14an average of approximately 5,000 to an average of approximately 12,500. Alberset al. (1986) attribute the removal of nitrate to denitrification. They foundthe COD:N ratio required to remove 80% of the nitrate was 4.Dedhar and Mavinic (1985) used activated sludge following an anoxic fully mixedreactor on an old leachate (BOD:COD = 0.06) to remove nitrogen. The influentammonia was up to 288 mg/L and influent COD was up to 318 mg/L. The system wasrun at 15 days solids retention time. Effluent ammonia was less than 1 mg/L, andeffluent nitrate was as low as 20 mg/L. Glucose addition into the anoxic reactorup to 1,500 mg/L was required to achieve denitrification. Influent metalconcentrations (totals) were zinc 0.019 —. 0.155 mg/L, manganese 0.024 — 0.286mg/L, iron 10.5 — 36.25 mg/L and nickel 0.025 — 0.066 mg/L. Effluent sampleswere filtered and removal rates were zinc 35—100%, manganese 78—100%, iron 80—100%, nickel 0—20%. As part of the experiment, zinc and manganese spiking wasdone to investigate the toxicity of these metals. Manganese did not result ininhibition of nitrification at 12.5 mg/L concentration, but inhibition did appearwith zinc concentration at 17.6 mg/L.Jasper et al. (1985b) used a similar system to Dedhar and Mavinic (1985). Theirsystem was run at nominal hydraulic retention time (aerobic basin volume/influentflow) of 24 hours, and sludge age of 5, 10, 15 and 20 days for the aerobic basin.Influent ammonia concentration averaged 161 mg/L. They could not achieve theirtarget of 10 mg/L effluent ammonia except sporadically, and postulated the poorammonia removal was due to metal toxicity.Keenan et al. (1984) investigated the full scale treatment of a landfill leachatewith influent ammonia of 890 mg/L. Early attempts to treat the leachate were notsuccessful due to phosphorous limitation and ammonia toxicity. To reduce theinfluent ammonia concentration, an air stripping lagoon at high pH wasincorporated into the system. Air stripping reduced the influent ammonia byapproximately 50%. The total system ammonia removal was subsequently 72% for two15activated sludge vessels in parallel and 99% for two activated sludge vessels inseries.Knox (1985) used a pilot activated sludge system to treat landfill leachate.Knox (1985) found that under certain conditions, extensive foaming occurred, andthat good sludge settling characteristics could not be achieved even withphosphorous addition.Ehrig (1985) investigated the use of full scale aerated lagoons with hydraulicretention times of greater than 10 days and loading rate less than 20 gBOD/m3/day for leachate treatment. He found that both effluent ammonia and BODlevels were seriously affected at temperatures below 5 °C (effluent BOD > 50mg/L), and therefore concluded that aerated lagoons were not appropriate forGerman climatic conditions.Azevedo (1993) used an continuous flow completely mixed activated sludge reactorwith 20 day solids retention time to treat leachate. The experiment involvedsupplemental ammonia addition to investigate the effects of ammonia toxicity.The system completely nitrified the ammonia up to 1500 mg/L ammonia—N, butcomplete inhibition of nitrification occurred at ammonia—N concentration of 2000mg/L. This may have been the result of an insufficient air supply, which failedto provide a mixed liquor dissolved oxygen level of 2—3 mg/L (Dr. Donald Mavinic,University of British Columbia, Personal communication, March 1994).Robinson and Grantham (1988) used full scale aerobic lagoons to treat leachatewith influent COD of 5518 mg/L, BOD of 3670 mg/L, ammonia—N of 130 mg/L. Theyfound that effluent values for COD of 153 mg/L, BOD of 18 mg/L, and ammonia—N of9.4 mg/L could be achieved down to water temperatures of 2 to 3 °C by maintaininga hydraulic retention time of 10 days. Ammonia removal was by assimilationrather than nitrification. Robinson and Mans (1983) earlier found that BOD:Nvalues greater than 100:3.6 provided complete ammonia removal through16assimilation. Robinson and Grantham’s (1988) system provided metal removal asshown in Table 5.TABLE 5: AERATED LAGOON METAL REMOVALMetal * Influent Effluent Removal(mg/L) (mg/L) (%)Fe 242 3.2 98.7Zn 4.9 0.2 95.9Mn 40 2.4 94.0Mg 85 63 25.9Cu 0.13 <0.1 >20Cr <0.1 <0.1 —Ni <0.1 <0.1 —Cd <0.1 <0.1 —Pb <0.1 <0.1 —Forgie (1988a) provided the following potential problems with suspended growthsystems: leachate foaming, high power consumption, metal inhibition, temperatureloss and inorganic precipitates caused by aeration, high sludge production whentreating young leachate, and poor sludge settling due to inadequate phosphorous.Fixed Film SystemsFixed film systems include a variety of biological treatment systems in whichmicroorganisms grow attached to an inert medium. The microorganisms are “fed”by either passing the wastewater over the medium (as in a trickling filter) orpassing the medium through the wastewater (as in a rotating biologicalcontactor). Examples of fixed film systems include trickling filters, rotatingbiological contactors (RBC), and packed or expanded bed systems (Forgie, l988a).In this review, only trickling filters and RBC’s will be investigated.NOTES* Authors did not state whether metals were dissolved or totals.SOURCE: Robinson and Grantham, 1988.17Trickling FiltersTrickling filters are packed columns of rocks or other media through whichwastewater is percolated or “trickled” at a controlled rate. Design parametersfor low—rate trickling filters for municipal wastewater are given in Table 6.TABLE 6: TRICKLING FILTER DESIGN PARAMETERSBOD Loading (kg BOD/m3/day) 0.08 — 0.4Hydraulic Loading (m/2day) 1.8 — 4.7Bed Depth (m) 1.5 — 2.1SOURCE: Viessman and Hammer, 1985Knox (1985) investigated the pilot-scale treatment of landfill leachate using atrickling filter over a two year period. Influent concentrations of ammonia were340 mg/L. The system hydraulic retention time was varied from 4.5 days to 15hours. Sodium bicarbonate (NaHCO3) was added to maintain an effluent pH of 7.5and sodium dihydrogen phosphate (NaH2PO4) was added to provide a Total OxygenDemand:Phosphorous ratio of 100:1. Effluent ammonia ranged from 2—34 mg/L, andammonia removal rates ranged from 8 — 70 g N/m3/day (unit volume of plasticmedia). Anticipated problems of scaling and clogging due to inorganicprecipitates did not occur. This was potentially because the leachate waslagooned for several months prior to treatment.A full—scale trickling filter in the United Kingdom failed due to clogging withferric oxide precipitates and its inability to handle fluctuating flows (Henry,1985).Rotating Biological Contactors (RBC’s)Rotating biological contactors (RBC’s) have been in use in Europe since 1958.They initially were used for organics removal, but now are also used for ammoniaremoval (Poon and Chao, 1979). The potential advantages of RBC’s over othertechnologies include excellent response to shock organic and hydraulic loadings18(Peddie and Atwater, 1985), tolerance to high influent ammonia—N concentrations(up to 2000 mg/L) (Hartmann and Hoffmann, 1990), low maintenance (Hosomi et al.,1991) and low operating costs (Clark et al., 1978).The treatment of landfill leachate and other high strength wastewaters usingRBC’s have been investigated by various authors. Since this thesis examines thetreatment of a landfill leachate using an RBC, a significant portion of thisliterature review will be dedicated to previous work using RBC’s.Rotating biological contactors consist of a series of disks which are immersedapproximately 40% in wastewater and rotated at a range of speeds. Weng and Molof(1974) and Wilson and Murphy (1980) showed that disk surface area loading is thekey design variable for RBC’s rather than hydraulic or volume loading rates.For municipal wastewater treatment, the critical design parameter is BOD loading.The recommended loading rate is 15 g total BOD/m2/day at 13 °C. A disk areaincrease of 15% for each 3 °C decrease in temperature is recommended (Viessmanand Hammer, 1985). For high ammonia wastewater such as leachate, ammonia loadingis often the determining design factor . According to Forgie (l988c), if theBOD:NH3-N ratio is less than 1, treatment system design should be based onammonia loading rather than organic loading. This “rule of thumb” applies to allaerobic systems.RBC ammonia and organic loading rates from various sources are given in Table 7.As shown in Table 7, ammonia loading rates for RBC are generally less than 2g/m2/day. Ehrig (1985) achieved greater than 95% nitrification at ammonialoading rates up to 17 g/m2/day, but he recommended loading rates be restrictedto less than 2 g/m/day to avoid nitrite build—up and subsequent operatingproblems. The Pitsea full scale leachate treatment plant was designed based onan ammonia loading rate of 4.8 g/m2/day at 20—25 °C (Water Quality19International, 1987).TABLE 7: AMMONIA AND ORGANIC LOADING RATES FOR RBCWastewater Influent Ammonia BOD COD Speed T Ammonia SourceAmmonia Loading Removal(mg/L) (g/m2/day) (RPM) (°C) (%)Sewage 40 0.8 NG 5.3 6.75 20 100 1Leachate 2000 2.0 6 NG 2Leachate 460 0.77 5 11.7 8—32 NG 59 3Leachate 460 0.77 5 11.7 8—32 NG 99 3SludgeSupernatant 780 2.2 0.5 2.7 13 15 99 4SludgeSupernatant 780 4.4 1.0 5.4 13 17 72 4Synthetic 125 1.0 NG NG NC 10—30 95 5AS Effluent 20 1.6 1.6 NC NC 13 95 6Synthetic 1.65 0.06 NG 6.1 10 NC 96 7Synthetic 3.85 0.13 NG 13.4 10 NC 63.1 7Synthetic 39.2 1.4 NG 23.3 10 NC 36.8 7Leachate 7—46 0.5 6.0 10.9 6 >5 95 8Leachate NC 2.0 NG NG NC NC 96 9Leachate 30 1.0 1.1 16 NG NG 95 10Leachate 350 4.8 NG NG 1.5 20—25 99 11Sewage 30 1.6 NG 9.9 16 15 87 12Sewage 22 1.1 NG 13.9 16 15 98 12Leachate 154 1.2—7.3 0.21—1.3 2.8—28.4 2.3 20 95 13NC = Not givenSOURCES:1. Pretorius, 19712. Hartmann and Hoffmann, 1990. These values are design recommendations.3. Hosomi et al., 1991. The first values are for a standard RBC. The secondvalues are for a modified RBC containing an anaerobic biofilter in thesame tank.4. Lue—Hing et al., 19765. Masuda et al., 19916. Antonie, 19747. Ahn and Chang, 19918. Peddie and Atwater, 19859. Ehrig, 198510. Albers et al., 198611. Water Quality International, 198712. Pano and Middlebrooks, 198313. Spengel and Dzombak, 1991Factors affecting nitrification rate include RBC speed, temperature, alkalinityavailability, BOD, and toxicity.Hosomi et al. (1991) investigated the effects of varying RBC rotational speed onnitrification rate over a range of 8—32 RPM. Japanese design standards areperipheral velocity of 15—20 rn/mm (28—38 RPM for the disks used). Hosomi et al.20(1991) found that in a standard RBC, nitrification rates increased withincreasing rotational speed , but that at 32 rpm the effluent becomes white andturbid due to detached biofilms. Weng and Molof (1974) found that over the rangeof 10—42 RPM (peripheral velocity of 5—20 rn/mm), maximum nitrification wasachieved at 42 rpm. Both Hosomi et al. (1991) and Weng and Molof (1974) linkincreased nitrification with increased tank dissolved oxygen.Nitrification rate depends on temperature for all aerobic processes. Wilson andMurphy (1980) studied TKN removal from municipal wastewater over a temperaturerange of 12—18 °C, and used an Arrhenius temperature correlation for RBC’sdeveloped by Murphy et al. (1977) to normalize removal rates to 20 °C. TheArrhenius correlation is shown in Equation 6.EQUATION 6: ARRHENIUS EQUATIONKT = K200(T_O)= TKN removal rate at T °C (g/m2/day)K20 = TKN removal rate at 20 °C (g/m/day)‘3 =1.09SOURCE: Murphy, 1980Pano and Middlebrooks (1983) also found nitrification in RBC’s of domesticwastewater followed the Arrhenius relationship with 0 = 1.10. They also foundno nitrification occurred below 5 °C. Peddie and Atwater (1985) found nonitrification of landfill leachate occurred using an RBC at water temperaturesless the 5 °C. Water Quality International (1987) reported that the designersof the full scale Pitsea leachate treatment system used landfill gas to heatleachate to 20-25 °C prior to treatment in an RBC.During the nitrification process, hydrogen ions are produced, and therefore tomaintain a constant pH, alkalinity or buffering is required. The theoreticalalkalinity requirement of nitrification is 7.14 mg alkalinity as CaCO3 per rngammonia—N oxidized (Ehrig, 1985). Chen et al. (1989) found that, in an RBC,nitrification rate was independent of bulk alkalinity at 6.7 mg/L alkalinity as21CaCO3 per mg/L ammonia—N. Lue—Hing et al. (1976) found a net alkalinity asCaCO:ammonia—N ratio of 6:1 was required to maintain a stable pH. Chen et al.(1989) found that to maintain nitrification in an RBC, the bulk alkalinity neededto be kept above 50 mg/L as CaCO3.Various authors have suggested that the autotrophic microorganisms responsiblefor nitrification (Nitrobacter and Nitrosomas) have slower growth kinetics thanthe heterotrophic organisms responsible for organic decomposition (Barnes andBliss, 1983; Antonie, 1974; Harremoes, 1982). In activated sludge systems, thisrelationship results in a longer sludge age for nitrification than for organicoxidation.In an RBC plant, nitrification is generally considered to not proceed unless theorganics have been removed enough so that the heterotrophs do not “choke out” theslower growing autotrophs. Therefore, organic removal primarily proceeds in thefirst stages of the RBC and nitrification primarily proceeds in the followingstages (Weng and Molof, 1974).Harremoes (1982) found that at dissolved oxygen concentrations of 3 mg/L amaximum filtered BOD of 20 mg/L was required for nitrification. Weng and Molof(1974) found nitrification did not proceed until the COD and BOD were removed toapproximately 50 and 14 mg/L, and a minimum dissolved oxygen concentration of 2mg/L was present.Several authors have examined simultaneous nitrification and organic removal, andsimultaneous nitrification/denitrification in biofilme.Pano and Middlebrooks (1983) measured the COD and ammonia concentration in theeffluent of each stage of a four stage RBC to develop kinetic relationships forsimultaneous organic and ammonia removal. They noted that the disks in the firststage were covered in thick grey biofilm and subsequent disks were covered in a22thinner, smooth, brown biofilm. Weng and Molof (1974) found that grey biofilmindicates a heterotrophic community, and brown biofilm indicates a nitrifyingcommunity.Pano and Middlebrooks (1983) found the majority of COD removal occurred in thefirst stage, and that COD removal followed Monod kinetics in the first stage andvariable order kinetics in subsequent stages. Ammonia removal followed Monodkinetics, but was inhibited by organic loading. In the first stage, the levelof inhibition varied linearly with organic loading.Gonenc and Harremoes (1990) found that pure nitrification (no organic substratepresent) is 1/2 order with respect to oxygen concentration (oxygen ratelimiting). They found that in the presence of organic substrates, thisrelationship must be modified to account for the fraction of nitrifiers in thebiofilm and the distribution of the nitrifiers through the biofilm. Theyconcluded that to achieve nitrification, the ratio between soluble BOD anddissolved oxygen concentration must be less than five.Masuda et al. (1991) investigated simultaneous nitrification/denitrification oflandfill leachate in a covered RBC with controlled oxygen partial pressure. Theyfound that heterotrophs, nitrifiers and denitrifiers were throughout thethickness of the biofilm. The activity of each of the groups was found to beindependent of the biofilm location (surface, middle, bottom), but stronglydependent on oxygen partial pressure in the air over the RBC.Masuda et al. (1991) found that with a C:N ratio of 3.5:1, ammonia loading rateof 1.0 g/m2/day, and an operating oxygen partial pressure of 0.05 atmospheres,up to 55% of the nitrogen could be removed through denitrification. Atatmospheric pressure (oxygen partial pressure of 0.2 atmospheres), approximately50% of the nitrogen was removed. At C:N of 1.5:1, up to 40% of the nitrogen wasremoved at oxygen partial pressure of 0.05 atmospheres, but only 5% was removed23at 0.2 atmospheres.Masuda et al. (1991) concluded that heterotrophs, nitrifiers and denitrifierscoexist throughout the biofilm. The activity of each group being stronglydependent on oxygen partial pressure. In an aerobic RBC, if rnicroaerobicenvironments exist, nitrifiers and denitrifiers can work together to producesimultaneous nitrification/denitrification. The nitrogen removal efficiency wasfound to depend on the partial pressure of oxygen in the air phase, watertemperature, hydraulic detention time, and the ratio of influent organics toammonia.Hosomi et al. (1991) compared a standard RBC to a RBC plus submerged anaerobicbiofilter. They found approximately 40% nitrogen removal from leachate in astandard RBC at ammonia—N and BOD loading rates of 0.77 g/m2/day and 5.0g/m2/day, and up to 90% nitrogen removal in the modified RBC. No additionalcarbon source was required. They found BOD removals of greater than 95% in eachsystem, but that COD removal was much higher in the modified RBC than standardRBC (85% compared to 65%).In their paper, Hosomi et al. (1991) do not suggest a mechanism for increased CODand nitrogen removal, but simply state that the combination method of aerobic andanaerobic treatment was effective in reducing refractory organic compounds.Chen et al. (1989) modelled the simultaneous removal of organics and nitrogen inan aerated, fully submerged, RBC. They found that, for simultaneous removal, abulk dissolved oxygen concentration, which balanced the aerobic and anoxic partsof the biofilm, was required. For their study, the required bulk dissolvedoxygen concentration was 2.5 mg/L. They found approximately 50% of totalnitrogen could be removed from synthetic wastewater with influent ammonia—Nconcentration of 20-30 mg/L and COD of 50—200 mg/L.24Atwater and Bradshaw (1981) found up to 50% nitrogen removal in an RBC treatingseptic tank effluent with nitrate—N up to 20 mg/L. They attributed the nitrogenremoval to denitrification.Gupta et al. (1994) found up to 87.6% nitrogen removal in an RBC treating highstrength synthetic nitrogen fertilizer wastewater. Nitrogen loading rates of 9.4to 16.1 g/m2/day were investigated. For influent TKN ranging from 1000 to 2000mg/L, TKN removal ranged from 96% to 60%. Gupta et al. (1994) attribute thenitrogen removal to simultaneous nitrification/denitrification by Thiospaerapantotropha, a heterotrophic nitrifier and aerobic nitrifier.The results of the preceding experiments indicate that, under certaincircumstances, nitrification and denitrification can occur simultaneously in aprimarily aerobic fixed film system. This may be the result of the presence ofanoxic regions within the biofilm or, as discussed by Gupta et al. (1994), dueto bacteria capable of denitrifying under aerobic conditions.Leachate constituents, which in excess, could inhibit the RBC nitrificationprocess include metals, ammonia, organics or xenobiotics. Organics have beenshown to inhibit nitrification in RBC’s as previously discussed. Ammonia isanticipated to inhibit nitrification, but other authors have successfullynitrified high ammonia wastes.Using an RBC, Lue—Hing et al. (1974) fully nitrified sewage sludge supernatantwith ammonia—N concentration of 780 mg/L. Hartmann and Hoffmann (1990) suggestleachate with influent ammonia of up to 2,000 mg/L can be successfully nitrifiedusing an RBC.Rotating biological contactors are designed to remove ammonia and organics. Theyhave also been shown to remove metals present in the leachate. Peddie andAtwater (1985) found metal removal rates shown in Table 8.25TABLE 8: RBC METAL REMOVALMetal* Influent Effluent Removal(mg/L) (mg/L) (%)Mn 1.77 0.21 88.1Fe 18.6 3.2 82.8Zn 0.11 0.019 82.7Pb 0.0036 0.0016 55.6Cu 0.0019 0.0009 52.6Ni 0.00113 0.00091 19.5Cr 0.00068 0.00057 16.2Notes:* All values totalsSOURCE: Peddie and Atwater, 1985The leachate described in Table 8 has lower metals concentration than theleachate described in Table 5: Aerated Lagoon Metal Removal, but the removalefficiencies are in the same range.Potential improvements to the conventional RBC have been suggested in severalpapers.One potential weakness of RBC’s is that they tend to produce effluent with higherfine suspended solids than suspended growth systems due to the turbulent shearingaction in the RBC tank (Watanabe et al., 1990). Watanabe et al. (1990) developeda two storey laboratory scale RBC in which the bottom one—half was used as aclarifier. They achieved a final suspended solids concentration of approximately10 mg/L without a final clarifier.Tanaka et al. (1991) found that the fine suspended solids produced by RBC’s couldnot be effectively removed by gravity settling alone. They found that increasingRBC hydraulic retention time reduced the number of fine particles in theeffluent, and that any small particles in the effluent could be most effectivelyremoved using coagulation/flocculation.Ahn and Chang (1991) compared a two storey RBC with the lower level acting as a26settling tank to a conventional RBC loaded at 6.1—23.3 g COD/m2/day and 0.06—1.4g NH3—N/m2/day. They found soluble COD removal rates were similar for bothunits, ammonia removal was slightly higher in the two storey RBC, and suspendedsolids removal was much better in the two storey RBC producing effluent with 1.8—6.2 mg/L compared to 12.5—19.6 mg/L in the standard unit.Nyhuis (1990) was able to achieve nitrification rates of 3.3 g N/m2/day in a fullscale sewage treatment plant by filtering the wastewater prior to the RBC toseparate organic matter removal and nitrification, and periodically reversingflow in the RBC to produce even growth throughout the stages.Surampalli and Baumann (1989) improved both organic removal and nitrification ina full scale RBC plant by adding supplemental aeration to the RBC tank. Thenitrification rate was increased from 20% to more than 50% for the same effluentCOD value (40 mg/L).Hosomi et al. (1991), treating landfill leachate, compared a standard RBC to amodified RBC, which incorporated an anaerobic biofilter into the tank under theRBC. The modification resulted in nitrogen removal, without organic substrateaddition, of more than 70% (up to 88%) compared to 40% in the standard unit, andimproved BOD and COD removal. Anaerobic TreatmentAnaerobic leachate treatment methods include both fixed film and suspended growthmethods. They potentially provide low maintenance, low energy, methods oforganics removal from high strength leachate. Another advantage of anaerobictreatment is that methane is produced as a byproduct, which can be either usedto improve reaction rates by heating the system or sold.Forgie (1988c) suggests that leachate with a BOD:COD ratio greater thanapproximately 0.4 is amenable to anaerobic treatment. Since high BOD:COD ratios27are typically transient, existing during the acidic phase, conditions conduciveto anaerobic treatment will generally be short term.The effluent from an anaerobic treatment process will be similar to “older”leachate (low BOD:COD ratio), and require further treatment using aerobic orphysical chemical treatment methods prior to discharge (Forgie, 1988c).An alternative method of producing low BOD:COD leachate would be to recirculateleachate through the landfill, since the landfill is essentially a largeanaerobic treatment vessel. Leachate recirculation is now accepted as astabilization method by the United States Environmental Protection Agency(Federal Register, 1991). Leachate recirculation is discussed later in thisreview.The results of various authors’ experiments treating leachate anaerobically areshown in Table 9.Method CODUpf low FilterSOURCES:1 Chang, 19892 Henry et al., 19873 Mendez et al., 19894 Muthukrishnan and Atwater, 1985TABLE 9: ANAEROBICTreatmentLEACHATE TREATMENTBOD: HRT Loading Temp Efficiency Source(days) (kg COD! (°C) (% COD Rem.)m!day)Upflow Bed&Filter 0.7 7.7 1.4 35 92.1 10.7 2.7 21.8 35 67.9 1Upflow Filter 0.7 4.0 1.45 21—25 95 20.7 2.0 2.89 21—25 68 20.3 1.0 1.26 21—25 95 20.3 0.5 3.14 21—25 60 20.5 1.0 1.35 21—25 90 20.5 0.5 2.66 21—25 88 2Digester Tank “old” 8.3 0.1 20&37 35 3“young” 15 0.29 20 46 3“young” 15 0.29 37 51 3“young” 4 1.1 20 29 3“young” 4 1.1 37 47 30.7 1.0 1.8—4.0 22 70 428Table 9 shows that, at COD loading rates of approximately 1.3 kg COD/m3/day andat BOD:COD ratios of as low as 0.3, high COD removal can be achieved. Table 9also shows that at high loading rates, temperature affects treatment efficiency.Anaerobic treatment does not effectively remove COD from old leachate.Mendez et al. (1989) found that phosphorous addition was not necessary foranaerobic treatment, removal was not improved by recycle, and inhibition probablycaused by heavy hydrocarbons resulted in a complete halt of the degradationprocess. They also found that addition of NaC1 to 20 g/L produced significantinhibition of degradation activity.Anaerobic treatment has been shown to be inhibited by unionized hydrogen sulphideconcentrations of 110 and 350 mg/L as sulphur, which resulted from influentsulphate concentrations in excess of 625 mg/L as sulphur (Parkin et al., 1991).A pH outside of 6 — 8 results in a sharp decrease in methane production in ananaerobic reactor (Speece et al., 1986).Anaerobic organic oxidation has been shown to be strongly inhibited by freeammonia. Heinrichs et al. (1990) found that unionized ammonia concentrations of200 mg/L totally inhibited methane production.A second application of anaerobic reactors in leachate treatment is as an anoxicbasin for denitrification. Dedhar and Mavinic (1985) achieved up to 100%denitrification by adding glucose to a predenitrifying suspended growth system(anoxic basin precedes aerobic basin). Ehrig (1985) found that a COD:N ratio of5—6 was required to achieve full denitrification. Biological Metal RemovalDissolved heavy metals in leachate can be removed during anaerobic or aerobictreatment of the leachate.29In anaerobic treatment, sulphate in the leachate is generally reduced to suiphideby sulphate reducing bacteria. Heavy metal ions form insoluble compounds withthe sulphide, which precipitate out as metal sulphides (Chang, 1989). Accordingto Barnes et al. (1991), to achieve sulphate reduction and heavy metalprecipitation, a redox potential of —100 mV (compared to —300 my formethanogenisis), a reactor pH of 5 to 9 (optimum 7.5), and an available carbonsubstrate are required.In aerobic processes, metals are oxidized and precipitated out (e.g. as metalhydroxides or oxides). Precipitation may result in clogging of media if usingtrickling filters (Henry, 1987). To avoid clogging of the aerators fromprecipitates of iron and calcium, suspended growth systems require coarse bubbleaerators (Ehrig, 1985).2.3.2 Physical/Chemical Treatment2.3.2.1 Recycle/RecirculationLeachate recycle involves collecting leachate and either above or below groundirrigating the landfill with the leachate. In the United States EPA LandfillRegulation (Subtitle D) 40 CFR Parts 257 and 258, effective October 9, 1993, ifa landfill is equipped with a composite liner and a leachate collection systemdesigned to maintain a maximum hydraulic head of 30 cm on the liner, leachaterecirculation is acceptable (Federal Register, 1991). The goals of leachaterecirculation are to speed up the stabilization of the landfill through theintroduction of additional moisture, improve leachate quality (reduce BOD andCOD), and increase the quality and quantity of methane production (FederalResister, 1991).Pobland et al. (1985) note that leachate recirculation may reduce thestabilization period from 15—20 years to 2—3 years. The EPA notes (FederalRegister, 1991) that under humid conditions, leachate recirculation is not30recommended because sufficient moisture is already available and additionalmoisture will increase total leachate production and may increase the hydraulichead acting on the liner system.Birkbeck and Tomlins (1985) note that potential problems associated with leachaterecirculation include clogging of irrigation equipment and landfill surface withprecipitates of carbonates and iron oxides, odours, and vegetation kill from airspraying leachate.Pohiand et al. (1985) found that even following recirculation, leachate stillcontains significant organic and inorganic contaminants, and in most cases willrequire additional treatment prior to disposal. Additionally, sincerecirculation involves using the landfill as an anaerobic bioreactor and ammoniais not removed through anaerobic decomposition (except through assimilation),recirculation should not significantly reduce leachate ammonia concentration.Therefore, under certain circumstances (low moisture), recirculation could beused to reduce organic constituents of leachate, but additional treatment willbe required prior to discharging the leachate. Land ApplicationLand application involves discharging leachate to land other than the landfilland relying on evaporation plus the assimilative capacity of the land to renovatethe leachate. According to Forgie (l988b), land application of leachate has notbeen widely investigated. Land application has been successfully used in GreatBritain as a treatment system, but in North America its use is restricted topolishing previously treated leachate (Henry, 1985).A full scale leachate treatment plant in Sarnia, Ontario, discharges treatedeffluent to wetlands prior to discharge to a creek. The wetlands provideapproximately one month of retention time to utilize residual nitrogen and31phosphorus (Environmental Science and Engineering, 1991). Air StrippingThe equilibrium between ammonium ion concentration and dissolved ammonia gas inwater depends on pH and temperature (lower temperature shifts balance towardsammonium ions) (Viessman and Hammer, 1985). At 25 °C, the equilibriumrelationship between ammonium ion concentration and free ammonia concentrationis shown in Equation 7.EQUATION 7: ANMONIA/ANNONIUM EQUILIBRIUM EQUATIONj3] [Hf] = 10 —9.245[NH4]T = 25°CSOURCE: Viessman and Hammer, 1985By raising the pH of wastewater to between 10.8 — 11.5 with NaOH or Ca(OH)2 andsubsequently aerating the wastewater, ammonia gas can be stripped from the waterto the air, thus removing the ammonia from the wastewater (Forgie, 1988b).Keenan et al. (1984) took advantage of the high pH following chemicalprecipitation of metals using lime to air strip ammonia. The ammonia wasstripped in a 1.74 day hydraulic retention time aerated lagoon precedingactivated sludge treatment. Keenan et al. (1984) found that influent ammoniaconcentration of up to 1000 mg/L inhibited the activated sludge microorganisms,but following 50% reduction through air stripping, the ammonia was no longerinhibitory.The disadvantages of air stripping include large chemical requirements due to thewell buffered nature of leachate, chemical costs (lime costs represented 30% oftotal costs for Keenan et al. (1984)), and sludge disposal requirements. AdsorptionTreatment by adsorption generally involves using either granulated activated32carbon (GAC) or powdered activated carbon (PAC). GAC is used in a filter orcolumn and PAC is added to the leachate as a liquid slurry (Forgie, 1988b).Activated carbon adsorption is most effective at removal of high molecular weightorganics, which predominate in either biologically treated leachate or oldleachate. Therefore, activated carbon adsorption is most effective as apolishing technique to remove recalcitrant organics (Forgie, 1988b). COD removalon biological treatment plant effluents of 85% are possible (Mendez et al.,1989).Various authors have shown that activated carbon is also effective at metalsremoval under certain circumstances (e.g. in the presence of organic complexingagents) (Bhattacharyya and Cheng, 1987; Corapcioglu and Huang, 1987), butcoagulation/precipitation techniques are more commonly used for metals removal(Enzminger et al., 1987).Another potential adsorption method is metals removal by adsorption to peat ina column. Available literature on adsorption of metals with peat is laboratoryscale only (McLellan and Rock, 1988).Corbett (1975) used laboratory scale peat columns to treat landfill leachate.Corbett (1975) achieved 59% metal removal at pH 7.1, and found that a dry weightof approximately 159 kilograms of peat was required per 1,000 litres of leachate.Corbett (1975) also found that “resting” the peat for one month, followingtreatment, was not sufficient to reuse the peat, and that desorption of metalsoccurred if water was percolated through the peat. Chemical Coagulation/PrecipitationChemical coagulation involves creating flocs by adding multivalent metal ions(e.g. Ca2, Fe3, Al3), which settle and trap suspended solids and colloidalmatter. Precipitation involves adding agents, which chemically bind withdissolved ions, creating insoluble precipitates. Lime is the most common33precipitation agent (Lema et al, 1988).Ehrig (1989b) found that flocculation was not a suitable treatment method forhigh strength leachate, but found iron salts could be used effectively to removeCOD (50% removal) from old leachate. Forgie (1988c) states that coagulation canbe used to remove residual suspended solids and colour. Lime precipitation canbe used as a pretreatment step for metals removal prior to biological treatmentprocesses to avoid potential inhibition of the treatment process (Forgie, 1988c).Keenan et al. (1984) used lime addition to remove metals prior to biologicaltreatment. The resultant high pH was utilized through air stripping to removeammonia. pH readjustment is required prior to biological treatment(Environmental Science and Engineering, 1991).In general, physical/chemical processes cannot be considered substitutes forbiological treatment methods, but rather should be considered a component of acombined biological/physical chemical treatment train designed to meetincreasingly stringent discharge standards. Other methods not discussed in thisreview include chemical oxidation (e.g. chlorination), membrane techniques suchas reverse osmosis and ultra—filtration, and ion exchange.2.4 LITERATURE REVIEW CONCLUSIONS AND EXPERIMENTAL OBJECTIVESThe leachate used in this experiment was a methanogenic stage leachate, with veryhigh ammonia concentration and relatively high COD concentration. Based on thereview of available literature, the system design was based on ammonia removalrather than organics removal.To remove ammonia, either a suspended growth or a fixed film system should beused. It appears that influent ammonia—N concentrations exceeding 2,000 mg/Lcompletely inhibit the activated sludge process (Azevedo, 1993), although theinhibition observed by Azevedo may have been due to insufficient process aeration34(Dr. Donald Mavinic, University of British Columbia, Personal communication,March 1994). Forgie (1988a) mentions several other potential problems withsuspended growth systems.RBC’s appear to nitrify leachate up to ammonia-N concentrations of 2000 mg/L atloading rates up to 2 g/m/day (Hartmann and Hoffmann, 1990). The additionaladvantages of RBC include low operating costs (Clark et al., 1978), lowmaintenance costs (Hosomi et al., 1991), and good response to shock loadings(Peddie and Atwater, 1985). It also appears that RBC’s may provide full nitrogenremoval under certain conditions (Masuda et al., 1991; Hosomi et al., 1991;Atwater and Bradshaw, 1981; Gupta et al., 1994).Unless the leachate being treated has a very high COD:ammonia—N ratio, the mosteffective method to completely remove nitrogen from the leachate appears to beusing biological denitrification. This can be achieved in an anoxic basin eitherpreceding or following the aerobic system. Supplemental carbon addition toprovide an energy source for denitrification is common, but not necessary ifsufficient carbon is available in the leachate.Based on the review of available literature, the system selected for thisexperiment was an RBC for nitrification and a predenitrifying anaerobic filterwithout supplemental carbon addition. It was postulated that nitrification wouldoccur in the RBC and denitrification would occur in the anaerobic filter usingthe COD in the leachate as an energy source. Organics and metal removal wereanticipated to occur simultaneously.The objectives of this research were to determine the loading rates at whichnitrification occurs in an RBC at high influent ammonia concentration, and todetermine whether a predenitrifying anaerobic filter could be used on theleachate without supplemental carbon addition. Secondary objectives includedremoving organics and metals.353. SITE DESCRIPTIONLeachate for the experiment was collected from Da Liao Landfill near Kaohsiung,located in south—western Taiwan, Republic of China. The landfill serves twosmall communities on the outskirts of Kaohsiung. A map of Taiwan showingKaohsiung is provided in Figure 1.According to the Kaohsiung County Environmental Protection Branch, the Landfillreceives refuse from approximately 400,000 people (Mr. Zhang, Personalcommunication, June 27, 1993). According to Mr. Zhang, the Landfill accepts450,000 tonne per year of refuse, but the Landfill has no weigh scales. Basedon the population estimate provided by Mr. Zhang, and Kaohsiung City’s per capitawaste generation of 0.4 tonnes/cap/year (Kaohsiung Municipal Government, 1992),a more conservative estimate of the annual refuse disposed of at the landfill is160,000 tonnes. From observations of truck traffic at the site, 160,000 tonnesper year is probably more accurate.A schematic drawing of the Landfill is provided in Figure 2, and a site plan isprovided in Appendix 1. Based on the plan in Appendix 1, the total area of theLandfill is approximately eight hectares.The Landfill began operation sometime around 1987.The landfill is underlaid with a geotextile membrane, and a concrete retainingwall is located at the eastern end of the landfill at which point leachate iscollected in a 27 cubic metre sedimentation basin. The leachate flow is measuredcontinuously using a Parshall Flume. The leachate is pumped to an on—sitefacility treating leachate plus septage. Septage is treated at the facilitybecause, in Taiwan, all buildings have sedimentation/septic tanks.36FIGURE 1: KAOHSIUNG LOCATION PLAN37LANDFILL SITE PLANN.T.S.STORAGESEPTAGED!SPOS’LANAEROBICTREATMENTVESSELADMINISTRATIONBUILDINGGATEMAINTENANCEBUILDINGFLOW MEASUREMENTAND SAMPLING LOCATIONPUMP SEDIMENTATIONCHAMBER CHAMBERCONCRETERETAININGWALL(15m HIGH)(lOOm WIDE)LANDFILL AREA(GU LLEY)FIGURE 2: LANDFILL SITE PLAN38The treatment plant includes an anaerobic treatment tank, an oxidation ditch, anda final clarifier. Chemicals including powdered activated carbon, polymer andsodium hydroxide are added to the oxidation ditch. Neither plant performancedata nor facility sizing data are available.Mean monthly precipitation and mean daily temperature data for Kaohsiung for theyears 1934—1989 are provided in Table 10. Table 10 also includes precipitationdata for the period the experiment was conducted (October 1991 to May 1992).Daily precipitation data for Kaohsiung are provided in Appendix 3.TABLE 10: PRECIPITATION AND TEMPERATURE DATA FOR KAOHSIUNGMonth Precipitation Precipitation Mean Daily(1934—1989 mean) 1991 & 1992 Temp.(mm) (mm) (°C)January 15 1992 33.0 18.6February 18 59.9 19.3March 38 127.8 21.8April 55 262.2 24.7May 171 146.7 27.2June 412 27.9July 407 28.4August 390 28.0September 166 27.6October 41 1991 35.1 25.9November 20 3.4 23.1December 13 34.6 20.0SOURCE: Personal communication, Taiwan Central Weather Agency, 199239An approximate water balance for each month is shown in Table 11. The leachateproduction results in Table 11 are a summary of the data provided in Appendix 4.Table 11 shows that, on average, approximately 105% of precipitation wascollected as leachate. Since some of the precipitation would have evaporated,or been stored in the incoming refuse, it is probable that the actual area fromwhich leachate was collected exceeded eight hectares.TABLE 11: DA LIAO LANDFILL WATER BALANCEMonth Precipitation Leachate Precipitation!Volume Production Leachate Prod.(ms) (ms)1 2November 270 4,020 0.07December 2,770 5,580 0.50January 2,640 5,210 0.51February 4,790 4,230 1.1March 10,220 4,780 2.1April 20,980 19,580 1.1Total 41,670 43,400 0.96NOTES:1. Based on 1991 and 1992 precipitation volumes from Table 10 and landfillarea of 8 hectares.2. From weakly leachate production volumes in Appendix 4.404. EXPERIMENTAL DESIGNApproximately one year prior to arriving in Taiwan, the author begancorresponding with Professor Lin Cheng—Fang of the National Taiwan University inTaipei to develop a research program.During the summer of 1991, Professor Lin informed the author he and a colleaguefrom National Sun Yat—Sen University in Kaohsiung (Professor Yang Lei) would beinvestigating the treatment of landfill leachate using the treatment train shownin Figure 3. The treatment train consisted of denitrification in an anaerobicfilter, nitrification and organics removal in an activated sludge treatmentvessel and clarification in a final clarifier.Following an initial literature review of potential treatment methods, the authorproposed to use a similar treatment train to the one proposed by Professor Lin,but to substitute an RBC for the activated sludge system.ANAEROBICFILTER/ACTIVATEDSLUDGESYSTEMSCHEMATICAruerobicF’derMixer‘7 RecycLePurpFeedVesseLFIGURE3:ANAEROBICFILTER/ACTIVATEDSLUDGESYSTEMSCHEMATIC42The leachate treatment system investigated in this project is shown schematicallyin Figure 4. The system consisted of:1) A peristaltic feed pump2) A 20 litre leachate feed container with 0.5 litre increments marked on theside of the container3) A 30 litre anaerobic filter made out of plexiglass and filled with 2.5 cmdiameter perforated balls called tn—packs4) A 10 litre RBC with 3 stages, and a total of 75 disks. The disks were 20cm diameter, 2 mm wide, and spaced on 9.2 mm centres. The total disk areawas 4.7 m2, and a minimum clearance of 0.5 cm was allowed between the disksand the tank. The RBC was rotated by an electric motor at 10—25 RPM5) A 10 litre final clarifier6) A recirculation peristaltic pump7) system piping was Nalgene 8000 (6.4 mm internal diameter, 1.4 mm wallthickness)ANAERDBICFILTER/RBCSYSTEMSCHEMATICAnxeroblcV=30LRototingBoLo0;cilCon-tctor’V10LA=4.7W’2Recycl.ePur’ipFeedVeeLFIGURE4:AN1EROBICFILTER/RBCSYSTEMSCHEMATIC44Based on the anticipated high ammonia concentration of the leachate andconversations with Professors Atwater, Lin and Yang, ammonia loading wasdetermined to be the critical design factor for the RBC. Subsequently, based onloading rates shown in Table 7, RBC ammonia—N loading rates of 1, 3 and 5g/m2/day were selected for investigation. Based on an estimated ammonia—Nconcentration of 1,700 mg/L (Chang, 1989), design flow rates of 2.8, 8.3 and 14litres per day were selected.The design of the anaerobic filter was based on an estimated COD of 5,000 mg/L,and minimum design loading rate of approximately 0.5 kg/m3/day. These loadingrates are based on previous work provided in Table 9. From the design loadingrate and design flows from the RBC calculations, a design volume of 30 litres wascalculated.The design of the clarifier was based on achieving a minimum detention time of2 hours (Viessman and Hammer, 1985) using up to 500% recycle (Jim Atwater,Personal communication, October 1991). Based on maximum design influent andrecycle flow, the design clarifier volume was 10 litres.To achieve denitrification, recycle was from the clarifier to the inlet of thefilter. To avoid clogging of the filter, effluent recycle was selected ratherthan sludge recycle. No facilities were included for sludge removal because theanticipated sludge volume was small, thus allowing manual removal.455. 1NALYTICAL PARIMETERS ND METHODSLeachate and effluent from the anaerobic filter and the RBC (collected from thefinal clarifier) were analyzed for a variety of parameters.The analytical parameters and their monitoring frequency are provided in Table12.5.1 BOO (BIOCHEMICAL OXYGEN DEMAND)BOD analysis was initiated within two hours of sample collection and followed theprocedure described in Standard Methods (American Public Health Association etal., 1985). All samples (including blanks) were seeded with effluent from theactivated sludge system or RBC system, and samples were not filtered prior toanalysis. No nitrification inhibitor was added. Dissolved oxygen was measuredusing a Syland—Temp-O2-Mat 4000 L meter. No long—term BOD tests were conductedto determine whether the seed was sufficiently acclimated or whether anitrification inhibitor was required.46TABLE 12: ANALYTICAL PARAMETERS AND MONITORING FREQUENCYLeachateWeeklyBOD (mg/L)COD (mg/L)Ammonia—N (mg/L)Suspended Solids (mg/L)pHMetals (dissolved, mg/L)Cd ,Cr, Cu, Fe, Pb, Mn, Ni, ZnNO3 (mg/L)N02 (mg/L)CF (mg/L)S042 (m/L)Flow (m /hour)PeriodicallyTKN (mg/L)Total Alkalinity (to pH 4.5) (mg/L as CaCO3)Anaerobic Filter & RBC EffluentMinimum Twice Per WeekFlow (L/day)Temp (RBC and Filter) (°C)RBC Speed (RPM)WeeklyBOD (mg/L)COD (mg/L)Ammonia—N (mg/L)pHMetals (dissolved, mg/L)Cd ,Cr, Cu, Fe, Pb, Mn, Ni, ZnNO3 (mg/L)N02 (mg/L)CF (mg/L)SO42 (mg/L)PeriodicallySuspended Solids (mg/L)5.2 COD (CHEMICAL OXYGEN DEMAND)COD analysis was initiated within two hours of sample collection, and followedthe K2CrO7 titration procedure described in Standard Methods (American PublicHealth Association et al., 1985). Since nitrites are generally assumed to be insmall quantities (American Public Health Association et al., 1985) no chemicaladdition to account for nitrite interference was included. Samples were notfiltered prior to analysis.To calculate RBC effluent COD, measured COD was adjusted to account for nitritepresent in the effluent as per Standard Methods (American Public Health47Association et al., 1985).5.3 AMMONIAAmmonia was measured within four hours of sample collection. Initially a SchottCG 840 meter with an ammonia membrane probe was used according to StandardMethods (American Public Health Association et al., 1985), but from January 15to February 15, 1992, replacement membranes were not available. Therefore, anion chromatograph (IC) (TOA ICA — 5000) with an SIC Chromatocorder 12 striprecorder was used.Ammonia probe samples were not filtered, but IC samples were filtered with a 0.4tm filter to avoid clogging the column.A sample set of data plus calculation methodology for the ammonia probe isprovided in Appendix 2.5.4 pHpH was calculated using a Schott CG 840 pH meter. Samples were analyzed withintwo hours of collection. Samples were not filtered prior to analysis.5.5 METALSDissolved metals (cadmium, chromium, copper, iron, lead, nickel, manganese andzinc) were measured following vacuum filtration with 0.4 jim filter paper.Samples were directly measured using premixed standards and an 0.05 N HC1 blank.A Hitachi Z—8000 Atomic Absorption Mass Spectrometer using flame atomizer, C2Hfuel and air as an oxidant was used.485.6 FLOWLeachate was added to the 20 litre feed vessel each one to two days. The meanretention time in the feed vessel was maintained at approximately three days. Theeffect of storage on leachate quality is unknown since a comparison between freshand stored leachate was not made.The leachate feed vessel was marked with 0.5 litre increments. Influent flow wasdetermined by recording the change in leachate feed volume over each one to twoday period, and subsequently calculating mean daily influent flow for the period.Recycle flow was calculated by measuring the system influent and filter effluentflows over a 15 minute period. The difference equalled the recycle flow.5.7 ANIONS (N03, N02, S042, CF)Anions including nitrate, nitrite, sulphate and chloride were measured in theleachate, filter effluent and RBC effluent using a TOA ICA—5000 ion chromatograph(IC) with a SIC Chromatocorder 12 strip recorder. Samples were filtered, priorto analysis, using a 0.4 i.m filter to avoid clogging the column.5.8 RBC SPEEDRBC speed was measured by counting the number of disk revolutions in a minute.5.9 SUSPENDED SOLIDSSuspended Solids were measured following vacuum filtration with a Whatman 42filter. Samples were dried at 105 °C overnight.495.10 TKN (Total Kjeldahl Nitrogen)TKN was analyzed on unfiltered leachate samples using the method described inStandard Methods (American Public Health Association et al., 1985).5.11 TOTAL ALKALINITY (titration to pH 4.5)Total alkalinity was measured titrimetrically to pH 4.5 using the proceduresdescribed in Standard Methods (American Public Health Association et al., 1985),and a Schott CG 840 pH meter to determine the titration end point.506. RESULTS6.1 LEACHATE, FILTER EFFLUENT AND RBC EFFLUENT CHARACTERISTICSThe mean, maximum and minimum parameter values for the leachate are provided inTable 13. Data are provided in Appendix 4. The results in Table 13 summarizethe data from the analysis of a total of 21 samples taken weekly over a six monthperiod. Leachate for the experiment was collected on a weekly basis in 20 litrecontainers, and stored at 4 °C prior to being dispensed into the leachate feedvessel.TABLE 13: LEACHATE CHARACTERISTICSParameter Mean Minimum Maximum(mg/L unless stated)pH (units) 8.1 7.8 8.8Ammonia—N 2140 1260 2700Suspended Solids 220 75 375BOD 705 465 1270COD 5040 3205 8420Total Alkalinity 10820 10510 11100TKN 2920 2470 3640Cd * 0.01 0.01 0.02Cr 3.05 1.91 4.10Cu 0.13 0.08 0.19Fe 7.30 5.34 14.65Mn 0.77 0.41 1.70Ni 0.22 0.19 0.27Pb 0.26 0.02 0.39Zn 1.01 0.49 1.29Cl 2450 1960 2860SO42 35 0.0 290N03 0.9 0.0 10.0N02 0.0 0.0 0.0NOTES:* All metals dissolved (filtered through 0.4 jm filter)Table 13 shows that the BOD:COD ratio of the leachate was approximately 0.1,which is indicative of a methanogenic phase leachate. The ammonia concentrationof the leachate was very high. No higher ammonia concentrations for landfillleachate have been found by the author in the literature. Comparing the metalsconcentrations to the expected methanogenic leachate composition shown in Table2, shows that cadmium, copper, iron, manganese and nickel are in the expectedrange, zinc is slightly higher than expected (a factor of two) and chromium is51particularly high (factor of 10). Given the amount of heavy industry in Taiwanand particularly in Kaohsiung, fairly high metals levels were anticipated.Mean, maximum and minimum parameter values for the anaerobic filter and RBCeffluent are provided in Table 14. Detailed discussion of the results isprovided in subsequent sections.TABLE 14: ANAEROBIC FILTER AND RBC EFFLUENT CHARACTERISTICSFILTER EFFLUENT RBC EFFLUENTParameter Mean Minimum Maximum Mean Minimum Maximum(mg/L unless stated)pH (units) 8.4 8.0 8.6 8.5 7.2 9.3Ammonia—N 1690 1040 2600 220 0.0 555Suspended Solids 170 65 290 170 64 280BOD 415 130 740 63 26 140COD 4480 2670 7245 2660 1020 3790Total Alkalinity 8150 6510 10980 3500 2630 4490Cd * 0.01 0.01 0.02 0.01 0.01 0.01Cr 3.17 2.42 4.09 3.41 2.52 4.93Cu 0.09 0.03 0.14 0.13 0.06 0.24Fe 4.31 2.20 8.15 4.59 2.29 5.94Mn 0.43 0.24 0.82 0.32 0.12 0.52Ni 0.25 0.17 0.35 0.27 0.18 0.33Pb 0.16 0.06 0.28 0.22 0.03 0.92Zn 0.63 0.40 0.89 0.85 0.52 1.32CF 2510 1940 2920 2740 2100 3050SO4-2 30 0.0 260 75 0.0 220N03 0.0 0.0 0.0 30 0.0 150N02 0.0 0.0 0.0 550 20 890NOTES:* All metals dissolved (filtered through 0.4 pm filter)6.2 FLOWDuring the experiment, a total of five system flow regimes were investigated overa period of approximately one month per flow regime. The influent and recycleflow during each period are shown in Figure 5.The maximum mean flow was 6.6 L/day with 90% recycle. The maximum recycle ratewas 220% at mean influent flow of 6.1 L/day. The experimental design called fora maximum flow of 14 L/day and 500% recycle, but full nitrification could not beSystemFlow80100Days-InfluentFlowInfluentFlow(L/day)Recycle(Llday)Flow(I/day)** BBB_BBB B.16 14 12 10 8 6 4 2 0 F. RI•.U—U..•.BBII”••BB.U BI•—IlBU-—.B0201p40U,r’.)60IIFu’8.1R-13.4F•6RO-F-8.8R.6F.3.SR.8IPeriodMeanPeriodMean120140160180200*RecycleFIGURE5:SYSTEMFLOW53achieved at the maximum flows used. Therefore, higher flows were notinvestigated. Daily flow data are provided in Appendix 4.6.3 MASS BALANCEAs previously discussed, to allow for a mass balance to be calculated across thesystem, parameters were measured in each of the leachate, anaerobic filtereffluent, and RBC effluent. The total mass of any parameter in each systemcomponent can be calculated using the relationships shown in Equation 8.EQUATION 8: MASS BALANCE CALCULATIONSSystem In (g/day) = I*CiFilter In (g/day) = I*Ci + R*CeFilter Out (g/day) = (I + R)*CfRBC Out (g/day) (I + R)*CeSystem Out (g/day) = I*CeFilter Removal (g/day) = I*Ci + R*Ce — (I+R)*CfRBC Removal (g/day) = (I+R)*Cf — (I+R)*CeSystem Removal (g/day) = I*(Ci_Ce)I = Influent Flow (L/day)Ci = Influent Concentration (g/L)R = Recycle Flow (L/day)Ce = Effluent Concentration (gIL)Cf = Filter Effluent Concentration (gIL)54Parameter removal in the anaerobic filter for COD, nitrogen and iron are shownin Figures 6, 7 and 8. Example mass balance calculations from data in Appendices5, 6 and 7 are shown in Example 1.EXAMPLE 1: MASS BALANCE SAMPLE CALCULATIONSCODNo Recycle (Day 27)I = 2.7 L/dayR = OL/dayCi = 5.06 g/LCf = 2.67 g/LCe = 2.13 g/LFilter Removal =RBC RemovalSystem RemovalRecycle (Day 34)I = 6.2 L/dayR = 13.4 L/dayCi = 3.82 g/LCf = 2.97 g/LCe = 2.36 g/LFilter Removal =RBC Removal =System Removal =I*Ci + R*Ce — (I+R)*Cf= 6.45 g/day = 47%= (I+R)*Cf— (I+R)*Ce1.5 g/day = 11%= I*(Ci_Ce)= 7.9 g/day = 58%—2.9 g/day12.0 g/day9.1 g/day—12%51%39%55EXAMPLE 1 CONTINUED: MASS BALANCE SAMPLE CALCULATIONSNitrogen:No Recycle (Day 27)I = 2.7 L/dayR = 0Ci = 1.630 g/LCf = 1.595 g/LCe = 0.054 g/lFilter Removal = 0.095 g/day = 2%RBC Removal = 4.16 g/day = 95%System Removal = 4.26 g/day = 97%Recycle (Day 55)I = 6.4 L/dayR = 13.4 L/dayCi 2.160 g/LCf = 1.040 g/LCe = 0.452 gIL (Sum of Ammonia—N, Nitrate and Nitrite)Filter Removal = —0.71 g/day = —5%RBC Removal = 11.64 g/day = 84%System Removal = 10.93 glday = 79%MetalsNo Recycle (Iron, Day 27)I = 3.0 L/dayR = 0Ci = 0.00640 g/LCf = 0.00291 g/LCe = 0.00229 g/LFilter Removal 0.0105 glday = 55%RBC Removal = 0.0019 g/day = 10%System Removal = 0.0123 g/day = 64%Recycle (Iron, Day 48)I = 6.0 L/dayR = 13.4 L/dayCi = 0.00644 g/LCf = 0.00477 g/LCe = 0.00572 g/LFilter Removal = 0.0228 g/day = 59.0%RBC Removal = —0.0184 g/day = —47.6%System Removal = 0.0044 g/day = 11.4%Figures 6, 7 and 8 show that parameter removal across the anaerobic filter variedwidely both over time and within individual flow periods. The large variationseems due to insufficient system stabilization time between changes in flowregimes. The total system volume was 50 litres, and the generally acceptedrequirement to ensure steady state conditions are achieved is three hydraulicretention times. Therefore, for system flows of 2.7 and 6.0 L/day, stabilizationtimes of 55 and 25 days would have been required.56>0EID0C)a)0.00L..CV.CIUCICCUU.0ICIU.ICIUCIIU-*****<.*(f******00CN0cc0cc00-aO%U.Eoj_ccOpoLc1a—0Co 2.h...•00 0.0.I.IL‘I0E0,0000 0 0 0 0U) U) 0 II)I 1I I“3AnaerobicFilterNitrogenRemovalNitrogenRemoval(%)80100120Time(days)F2.7RaOF&1R”13.4F-6R-OF68R-8IF3.eReI40 20 0-20-40-60-80-100-120-********.)I****IIIIILn —.10204060F•PeriodMeanInfluentFlow(L/day)R•PeriodMeanRecycle(L/day)140160180200FIGURE7:ANAEROBICFILTERNITROGENREMOVAL58o o 0c’100c’J000>b0-a‘-C,E‘ICuCC.00o• •CICIIICICCILI.0->0EC0—I-.a).I0.a0a)C0ICIII.qI1CIIi0ICIIIII-0EC00 0 0cc cj59In order to investigate as many flow loading regimes as possible, flow regimeswere changed as soon as system effluent ammonia stabilized. Since ammonia wasremoved primarily in the RBC (which was only 10 litres) it responded rapidly tochanges in influent flow. A more rigorous approach would have been to wait afull three hydraulic detention times prior to implementing flow regime changes.Since parameter removal in the anaerobic filter and RBC varied widely throughoutthe experiment, parameter removal in each system component cannot be accuratelycalculated. Estimates of parameter removal for the anaerobic filter and RBC areprovided, based on values from flow period three (See Figure 5), which was thelongest flow period (60 days).Overall system removal results are provided for each parameter for each flowperiod.6.4 BOD and COD REMOVALAccording to Forgie (1988c), biological treatment is inappropriate for organicsremoval for leachate with a BOD:COD ratio of less than approximately 0.1, due tothe recalcitrant properties of the existing organic material. The mean BOD:CODratio of the leachate from Table 13 is 0.14. Therefore, although some degradablecarbon was present in the leachate, the COD removal was anticipated to be low.60Table 15 shows system BOD and COD removal from data provided in Appendix 5.TABLE 15: BOD AND COD REMOVALDay 0—27 28—55 56—111 112—146 147—163Flow (L/day) 2.8 6.1 6.0 6.6 3.6Recycle (L/day) 0.0 13.4 0.0 6.0 6.0BOD Results Mean*Influent BOD (mg/L) 465 670 620 920 1270 705Effluent BOD (mg/L) 26 47 64 85 57 63BOD Removal (%) 95 93 90 91 96 92COD ResultsInfluerit COD (mg/L) 4100 4590 5160 7220 4898 5040Effluent COD (mg/L) 2140 2630 2750 2960 2502 2660COD Removal (%) 48 43 47 59 49 49COD:BOD Removal 4.5 3.1 4.3 5.1 2.0 3.7Notes:* Mean values are the mean of all samples.The results in Table 15 show period mean BOD removal ranged from 90—96%, with anoverall mean of 92%. Period mean COD removal ranged from 43—59%, with an overallmean of 49%. Period mean COD:BOD removal ranged from 2:1 to 5.1:1, with a meanof 3.7:1.Given that BOD is generally assumed to represent the biologically degradableportion of COD, the COD:BOD removal values appear high. In other landfillleachate treatment experiments, Hosomi et al. (1991) found a COD:BOD removal of2.3:1, Albers et al. (1986) found a COD:BOD removal of 7.5:1, Spengel and Dzombakfound a COD:BOD removal ratio of 6.6:1. Based on these results, the COD:BODremoval ratios found in this experiment do not seem unreasonable.These results seem to indicate that either the COD test was overestimating theorganic content of the leachate or the BOD test was underestimating thedegradable component of the organic matter.To determine if the BOD test was underestimating the degradable organic content,61long term BOD tests would be required to estimate the ultimate BOD, and determineif the seed was sufficiently acclimated (Dr. David Forgie, Associated EngineeringLtd., Personal communication, April 1994).According to Standard Methods (American Public Health Association et al., 1985),chloride content exceeding 2000 mg/L may result in interference of the CODmeasurement. From Table 13, the mean chloride concentration of the leachate was2450 mg/L. Whether the high chloride concentrations interfered with themeasurement of COD is unknown.Based on the data provided in Appendix 5, both BOD and COD removal were primarilyin the RBC.Figures 9 and 10 show leachate and RBC effluent BOD and COD concentrations overtime.Figure 11 shows system BOD and COD removal with increasing flow. Figure 11 showsthat both BOD and COD removal were independent of system flow. This result wasanticipated because the system was only lightly organically loaded at all flowrates.620.4-I2Nw0a)IctlC)a,-J00(‘400CD07-01-u)>friE0Co00(‘10CI.wC)*.1-I0-J0C0.cI-JC04.’.1-ICC)0C000CCIII.CICCIIIaICIUICIU.CI.U-1a.-j-aoCu.CCCC1C.aa.I I7- co (‘40 00 0zQ0LeachateandRBCEffluentCODCODConcentration(mg/L)(Thousands)10U8-6-II*2-********0IIII020406080100120140160180200Time(days)F•2.8RIOFaLlRa13.41F18R.OF•e.eR.61F13eR-8Leachate*RBCEffluentF-PeriodMeanInfluentFlow(L/day)R•PeriodMeanRecycle(Llday)FIGURE10:LEACHATEANDRBCEFFLUENTCOD640U0C-I-Iw>0Ea)00UV.•UUI’.U**** **0ECU00*>1-J.2LIE0U)**0CCa0a:i*EU0**I0010 0C)000cii656.5 NITROGENGiven the low BOD:COD ratio and the high ammonia concentration of the leachate,ammonia and nitrogen removal were the prime goals of the study.To measure nitrogen transformations within the system, ammonia was measuredthroughout the duration of the experiment. Nitrite and nitrate were measuredcommencing in mid—January 1992 due to a delay in receiving an anion column forthe ion chromatograph. TKN (total keldahl nitrogen) was measured in theleachate mid—December to mid—January, to develop a correlation between ammoniaand TKN data. Correlation calculations and leachate, filter effluent and RBCeffluent nitrogen data are provided in Appendix 6.Nitrogen removal across the system is based on influent ammonia—N concentrationrather than TKN, because TKN was measured in the leachate only, and was onlymeasured on a few occasions (See Appendix 6). Additionally, ammonia removalrates are more commonly referred to in the literature than TKN removal. The meanTKN:ammonia—N ratio was 1.4:1, which equals the ratio found by Dedhar (1985) inhis leachate treatment investigation.Table 16 shows nitrogen forms and removal efficiencies in the system at varyingflows.Figure 12 shows leachate and RBC effluent ammonia concentration.66TABLE 16: NITROGEN AND AMMONIA REMOVAL0—27 28—55Dayefficiency at varying RBC mass loadingloading rates based on a mean ammoniaremoval of 18% in the anaerobic filter. This removal rate is based on data fromflow period 3. Azevedo (1993) found anoxic ammonia removal of 8%. Carley (1988)and Mavinic and Randall (1990) found anoxic ammonia removals of 6% and 10%.Figure 13 shows decreasing removal with increasing loading. The linearregressions statistics equal: Slope = —5.9 %/(g/m2/day), r2 = 0.39, indicatinga non—linear relationship between removal and loading.Ammonia removal throughout the study exceeded 80%, but at loadings greater than1.5 g ammonia—N/m2/day, mean effluent ammonia exceeded 100 mg/L, which wasconsidered too high.Figure 14 shows ammonia mass removal with increasing loading. Figure 14 showsa linear relationship, indicating that, on a mass loading basis, the process wasnot inhibited.56—111 112—146 147—163 Mean1Flow (L/day) 2.8 6.1 6.0 6.6 3.6Recycle (L/day) 0.0 13.4 0.0 6.0 6.0Influent NH3—N (mg/L) 1856 2235 2244 2254 1957 2142RBC NH3—N Loading (g/m2/d) 2 0.9 2.5 2.0 2.9 1.3Effluent NH3—N (mg/L) 59 454 173 251 52 222Effluent NO2—N (mg/L) —— 71 590 834 495 552Effluent N03—N (mg/L) —— 3 3 70 90 32Overall NH3—N Removal (%) 97 80 92 89 97 90Overall Total—N Removal (%) —— 76 66 49 67 66NOTES:1. Mean values are mean of all samples.2. RBC loading is estimated based on 18% ammonia removal in the anaerobicfilter.Figure 13 shows overall ammonia removalrates. These rates are estimated RBC67C0EEa4Ca)21IwC)at,Ca)-CC)G)-Jaaa **a *a*a *a *a *aa *aa *aa *aaa *a0000-10-0-C”U)-0cc-o-oC-o-oC”0CaCaU.CaCCaU0ICaUw0aCaU.0IC”aLI.00I-JzC0EE•1-’C0IIwC)*0-C(3a —0..Co—C.00h..CC• UI I I I IU) C’J U) It)C41 00AmmoniaRemovalAmmoniaRemoval(%)100-********90-*****co80-*70-60IIIII00.511.522.533.5RBCAmmoniaLoading(g/m2/day)FIGURE13:ANMONIAREMOVAL69+It)++>0Ewlx++ ++++U)U)+++C.,-DE0,CCu0-jU)C0EE1-1<C)U)0+0EE++‘I0Ea,CEECO C1 0 CO CD C’J 01 1- 1-+70Although Figure 14 shows that, on a mass loading basis, ammonia removal was notinhibited, full ammonia removal could only be achieved up to an RBC loading rateof 1.5 g/m2/day. Given that Spengel and Dzombak achieved 95% ammonia removalat an RBC loading rate of up to 7.3 g/m2/day at influent ammonia—N of 154 mg/Land 20 °C, the results of this experiment show inhibition of nitrification.Possible reasons for inhibition are discussed subsequently.6.5.1 Effect of Hydraulic Retention Time on Ammonia RemovalWeng and Molof (1974) and Wilson and Murphy (1980) showed that disk substratesurface area loading is the key design variable for RBC’s, rather than hydraulicretention time. However, Peddie (1986) found good correlation between hydraulicretention time and ammonia removal for an RBC treating landfill leachate.Figure 15 shows ammonia removal compared to system influent flow. Since leachateammonia concentration did not vary significantly during the study, Figure 15 issimilar to Figure 13. The linear regression statistics equal: Slope = —3.0%/(L/day), r2 = 0.52, which is again indicative of a non—linear relationship.71_______________0.2 *LL.C>D-oIC**LL>0E2w *E10*U—*CoCJ HE*z0EE II I 00 0I 0 000Lfl1-1H72Figure 16 shows ammonia removal compared to total system flow (influent plusrecycle). Figure 16 shows a more linear relationship between ammonia removal andtotal flow than shown in either Figure 13 or 15. The linear regressionparameters equal: Slope = — 0.95 %/(L/day) r2 = 0.67, which is a bettercorrelation than either mass loading or influent flow, but is still a relativelypoor correlation. No similar results are available in the literature, sinceRBC’s are most often run as a complete treatment system without recycle.6.5.2 Inhibition of NitrificationFigure 17 shows RBC effluent nitrite and nitrate concentrations over time.Figure 17 shows a long term (greater than 100 days) nitrite build—up. The buildup seemed to occur with or without recycle and nitrate in the effluent was allbut eliminated. The results indicate that the transition from ammonia to nitritewas occurring, but the transition from nitrite to nitrate was being inhibited.Alleman (1984) suggests certain factors (elevated pH, low temperature, low oxygenor carbon dioxide partial pressure, free ammonia and process overloading) mayselectively inhibit Nitrobacter, resulting in a prolonged nitrite build—up.Several factors including pH, metals or ammonia could have caused inhibition ofthe oxidation of nitrite to nitrate. Given that the influent ammoniaconcentration to the RBC generally exceeded 1,500 mg/L, inhibition by the ammoniaor free ammonia is most likely.Working with a continuous flow activated sludge reactor, Azevedo (1993) found anitrite build—up occurred at influent ammonia—N concentrations of 600 mg/L. Geeet al. (1990) found that the rate of conversion of ammonia to nitrite isinhibited by ammonia, and can be modelled by Equation 3: The Haldane InhibitionModel.AmmoniaRemovalVsTotalFlowAmmoniaRemoval(%)100-****90-******80-*70 60I02468101214161820RBCFlow(includingrecycle)(L/day)FIGURE16:AMMONIAREMOVALVSTOTALFLOWRBCEffluentNitriteandNitrateConcentration(mgN/L)1-••0.8-06-•U0.4-•0.2-•+++I111+11++i020406080100120140160180200DaysF-2.BROF.&1R_13.4jF.5R-OF-6.8R•eF.3.6R•6Nitrite+NitrateF•PeriodMeanInfluentFlowCL/day)R•PeriodMeanRecycleCL/day)FIGURE17:RBCEFFLUENTNITRITEANDNITRATE75The conversion of nitrite to nitrate was not effectively modelled with theHaldane Inhibition Model, and the oxidation of nitrite to nitrate was found tobe strongly inhibited by simultaneous high concentrations of ammonia and nitrite(approximately 1,000 mg/L total N). These results support the conclusion thathigh influent ammonia concentration caused the inhibition of the conversion ofnitrite to nitrate and resulted in the observed nitrite build—up.Since nitrite/nitrate were not measured until day 45 of the experiment,definitive conclusions cannot be made. But given, ammonia was almost completelyremoved from the leachate at ammonia—N loading rates up to 1.5 g/m2/day (97%),and initial analysis two weeks after increasing loading rates showed only aslight nitrite build—up (71 mg/L), a plausible conclusion is that nitrite buildup would not occur at low (<1.5 g/m2/day) ammonia loading. This conclusion issupported by Ehrig(1985), who recommends ammonia loading of less than 2 g/m/daybe maintained to avoid nitrite build—up.As previously mentioned, in addition to an observed nitrite build—up, the removalof ammonia from the system appeared to be inhibited at ammonia loading ratesexceeding 1.5 g/m2/day. Spengel and Dzombak (1991) achieved 95% ammonia removalat RBC loading of up to 7.3 g/m2/day. Ehrig (1986) achieved full ammonia removalat ammonia loading rates of 17 g/m2/day. Given the high ammonia and nitriteconcentrations in the RBC, it is reasonable to assume that the inhibition ofammonia removal was also a result of the high ammonia and nitrite concentrations.Azevedo (1993), using an completely mixed activated sludge reactor, foundcomplete inhibition of nitrification (effluent ammonia—N equal 700 mg/L) at aninfluent ammonia concentration of 2000 mg/L.766.5.3 Nitrogen RemovalAs previously discussed, developing an accurate mass balance for major parameterscould not be achieved. Although steady—state was not fully achieved, anapproximate mass balance for nitrogen for the RBC can be determined bycalculating the total nitrogen entering and exiting the RBC. Figure 18 shows RBCnitrogen removal based on RBC influent ammonia and effluent total nitrogen(ammonia plus nitrite and nitrate).Based on the results shown in Figure 18, the mean total nitrogen removal in theRBC was 54%. The mean system total nitrogen removal was 66%. Nitrogen removalappeared to be independent of loading rate.The nitrogen removal in the RBC could be the result of assimilation, strippingor denitrification. Given that influent ammonia concentration substantiallyexceeded influent BOO, only a small portion of the nitrogen removal would havebeen through assimilation.The RBC effluent pH ranged from 7.2 to 9.3 and averaged 8.5 (see Table 14).According to Equation 7, 0% to 50% of ammonia would be in dissolved gaseous form.Therefore, air stripping and denitrification would have combined to remove thenitrogen from the system.Although off—gasses from the RBC were not analyzed, ammonia odours were neverpresent over the RBC. This is not sufficient evidence to show that the ammoniaremoval was not a result of air stripping. The odour threshold for ammonia is46.8 ppm (Weiss, 1980). Therefore, given that daily ammonia—N removal ranged upto approximately 10 g/day, sufficient ammonia would have been produced to makeapproximately 200 litres/day of air exceed the odour threshold. Since the roomthe experiment was conducted in was not ventilated, this quantity of ammonia mayor may not have been detectable.RBCNitrogenRemovalNitrogenRemoval(%)100*80-***60-****40-**20-0IIIII00.511.522.533.5RBCAmmoniaLoading(gIm2/day)FIGURE18:EECNITROGENREMOVAL78As shown in Table 14, alkalinity was removed from the system. This is evidencethat nitrification occurred in the system. As shown subsequently in Section 6.8,the alkalinity:animonia—N removal ratio was not sufficient to suggest completenitrification, unless denitrification is also assumed to have occurred.As shown in Equation 4, denitrification requires a carbon substrate. Based onthe stoichiometric requirements of denitrification using methanol as a carbonsubstrate, the approximate COD requirements are 3.0 g/g—N for denitrification ofnitrate and 1.7 g/g—N for denitrification of nitrite. The overall mean COD/Nremoval for the experiment was 1.8 g-COD/g—N. Therefore, assuming all of the CODconsumed was used for nitrogen removal, and denitrification from nitriteoccurred, sufficient COD was consumed to support denitrification.Various authors have shown nitrogen removal in RBC’s, including Masuda et al.(1991), Hosomi et al. (1991), Atwater and Bradshaw (1981), and Gupta et al.(1994). The maximum nitrogen removal observed was 87.6% at influent totalnitrogen concentration of 1786 mg/L and total nitrogen loading of 9.36 g/m2/day(Gupta et al., 1994). These authors postulate that nitrogen removal is a resultof concurrent nitrification/denitrification in the RBC. Masuda et al. (1991)attribute the results to the simultaneous presence of aerobic and anoxicconditions within the fixed film. Masuda et al. (1991) showed increasing nitrogenremoval with decreasing oxygen partial pressure (ie. decreased dissolved oxygen),which supports the hypothesis of denitrification occurring under anoxicconditions within the biofilm. Gupta et al. (1994) attribute the nitrogenremoval to simultaneous aerobic nitrification/denitrification as described byRobertson and Kuenen (1984) and shown in Equation 5.Based on the results of this experiment, two possible explanations of theobserved nitrogen removal are possible:1. Removal is the result of nitrification/denitrification reactions, with79nitrification proceeding only to nitrite as shown in Equation 5.2. Removal is the result of ammonia stripping occurring simultaneously withnitrif icat ion.In similar work currently being conducted by the author, an RBC is being used tonitrify landfill leachate with influent ammonia—N of up to 300 mg/L, and totalBOD of approximately 50 mg/L. The RBC effluent pH ranges from 7.4 to 8.9 with anaverage of 8.1, and no nitrogen removal is occurring. This observation suggeststhat little ammonia stripping would occur over the pH range observed in thisresearch (7.2—9.3).Although neither nitrification/denitrification or ammonia stripping can be provento have caused the observed RBC nitrogen removal since RBC off—gasses were notanalyzed, it seems most likely that the former caused the nitrogen removal. Thisis because:1. Robertson and Kuenen (1984) and Kuenen (1988) have shown that aerobicnitrification/denitrification is possible, and other authors have shownnitrification/denitrification can occur in a primarily aerobic biofilm2. Both alkalinity consumption and COD removal results support the explanationof simultaneous nitrification/denitrification3. Ongoing research by the author suggests that in the pH range observed,ammonia stripping is unlikelyAlthough, as previously discussed, system mass balances cannot be used toquantify mass removals in each of the system components, the results of thisresearch show that full denitrification occurred in the anaerobic filter duringrecycle. This conclusion can be made because nitrite and nitrate were not80present in the filter effluent under all operating conditions (see Table 14>,including 100% recycle and recycle nitrite—N concentration greater than 800 mg/L.6.6 METALSAs part of the study, filtered samples were measured for iron, zinc, lead,copper, cadmium, manganese, chromium and nickel on a weekly basis. Data from theanalysis are shown in Appendix 7. Overall mean removal ranged from —19% fornickel to 59% for manganese,, and are shown in Table 17. Measured values aredissolved only (filtered through a 0.4 m filter). Totals were not measured.TABLE 17: OVERALL METAL REMOVALMetal Leachate Filter RBC RemovalEffluent Effluent(mg/L) (mg/L) (mg/L) (%)Mn 0.77 0.43 0.32 59Fe 7.30 4.31 4.59 37Pb 0.27 0.16 0.22 17Zn 1.01 0.63 0.85 16Cd 0.01 0.01 0.01 0Cu 0.13 0.09 0.13 0Cr 3.05 3.17 3.41 —12Ni 0.22 0.25 0.27 —19Although system component removals cannot be accurately calculated, based on theconcentration of the effluent from the anaerobic filter and RBC shown in Table17, the majority of metal removal appears to have been in the anaerobic filter.The variation of overall metal removal is shown in Figures 19 to 25 from data inAppendix 7.ChromiumTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)40*20-* *:::: -60- -80-*-100II0246810Flow(L/day)FIGURE19:CHROMIUMTREATMENTEFFICIENCYCopperTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)60**4020-*Occ*-40-*-60III0246810Flow(L/day)FIGURE20:COPPERTREATMENTEFFICIENCYIronTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)70***60-50-40-30-***20-*10-*010III0246810Flow(L/day)FIGURE21:IRONTREATMENTEFFICIENCYManganeseTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)120100-**80-*****60-*40-*20**0II0246810Flow(L/day)FIGURE22:MANGANESETREATMENTEFFICIENCYNickelTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)20 0*** *-20-**-40--60-*-80I0246810Flow(L/day)FIGURE23:NICKELTREATMENTEFFICIENCYLeadTreatmentEfficiencyOverallSystemTreatmentEfficiency(%)100**0*-50--1O0-co*-150--200--250-*-300I0246810Flow(L/day)FIGURE24:LEADTREATMENTEFFICIENCY8701>C)Ca)IsIIII•1-’C >#1% 0wE .!-‘ .2CD>V-J0C4Jo 0 0cc C41C)zHC)HE•io 0 0 0 0(N CDI I I088Figures 19 to 25 show generally non—linear relationships between flow and metalremoval.Chang (1989) states that the main mechanism for removal of metals in an anaerobicfilter would be the formation and precipitation of metal suiphides. Barnes etal. (1991) anaerobically treated acid mine drainage with influent sulphateconcentration exceeding 1000 mg/L to remove metals. They achieved 100% removalof zinc, cadmium, cobalt and copper. Chang (1989) removed 95% of soluble ironfrom a leachate with influent iron of 570 mg/L and influent sulphate of 1830mg/L.The leachate was analyzed for sulphate, but sulphate was only present in 2 of 11samples, and did not exceed 290 mg/L. Sulphate was present in 6 of 11 RBCeffluent samples. Hydrogen suiphide odour was not detected in the leachate oranaerobic filter effluent. Given that the odour threshold for detection ofhydrogen suiphide is 0.0047 ppm (Weiss, 1980), even trace amounts of hydrogensuiphide should have been noticeable.These results indicate that sufficient sulphate and sulphide may not have beenpresent in the leachate to fully precipitate the metals present.The lack of metal removal in the RBC cannot be adequately explained. Resultsfrom aerobic systems (aerated lagoon and RBC) in Table 5 and Table 8 show removalefficiency up to 99% for iron in an aerated lagoon system (Robinson and Grantham,1988) and 88% for total manganese in an RBC system (Peddie and Atwater, 1985).In comparison, based on the information in Table 17 zero or negative removaloccurred in the RBC for most metals.Under aerobic conditions, iron and manganese are removed from wastewater throughthe oxidation of Fe2 and Mn2 to Fe3 and Mn4. The oxidized species are muchless soluble than the reduced species. For instance, according to Benefield et89al. (1982), at pH 8, Fe2 concentration can be up to 10 mg/L. Under the sameconditions, Fe3 concentrations would be in the io mg/L range. Therefore,following oxidation in the RBC, iron and manganese should have been totallyremoved from the leachate.pH also affects the metal solubility. An increase in pH occurred across theanaerobic filter for the duration of the experiment, and a further increase inpH occurred across the RBC for the first part of the experiment. Table 18 showsthe effect of pH on the solubility of the metals analyzed in compounds withsulphide, hydroxide and oxide.90TABLE 18: EFFECT OF pH ON METAL COMPOUND SOLUBILITYMetal S+2 OH 0+2Mn A A AFe(II) A A AFe(III) d A APb A w wZn A A wCd A A ACu A A ACr d A aNi A w AA: Insoluble in water, but soluble in acidd: Decomposes in waterw: Sparingly soluble in water, but soluble in acida: Insoluble in water, sparingly soluble in acidSOURCE: CRC Handbook, 1989—1990For each of the metal compounds shown in Table 18 except chromium sulphide, anincrease in pH should result in a decrease in solubility. Therefore, the lackof metal removal cannot be associated with increasing pH.The metals that increased across the treatment system, chromium and nickel, maysimply have not been treated by the system, and the measured increase is theresult of experimental error. Peddie (1985) found RBC removals of less than 20%for chromium and nickel compared to removals exceeding 80% for manganese andiron, indicating biological treatment is ineffective at removing these metals.The high solubility of metals and consequential lack of removal by the system mayindicate that the metals were complexing with organic molecules such as humic andfulvic acids. According to Benefield et al. (1982), the presence of thesemolecules will significantly increase metal solubility. To test this theory,extraction of the organics would be necessary.Another possible explanation is that metals were released from leachate solidsduring treatment. This theory cannot be verified because only dissolved metalswere measured. In future work, to ensure all metal forms are measured, total91metals rather than dissolved should be measured.Since metal discharge levels are not regulated in Taiwan, RBC effluent metallevels are compared to B.C. Pollution Control Objectives (1976) AA and BB valuesfor discharge to receiving bodies in Table 19.TABLE 19: RBC EFFLUENT METAL LEVELS COMPARED TO B.C. POLLUTIONCONTROL OBJECTIVESMetal Effluent B.C. Pollution Control ObjectivesAA BB(All values dissolved mg/L unless stated)0.01 0.005 0.013.41 0.1 0.30.13 0.2 0.54.59 0.3 1.00.22 0.05 0.10.32 0.05 0.50.27 0.3 0.50.85 0.5 5.0***CdCrCuFePbMnNiZnNOTES:* B.C. Pollution Control Objectives Levels AA and BB for these parameters aretotals rather than dissolved.SOURCE: British Columbia Department of Lands, Forests and Water Resources, 1976Table 19 shows that the system effluent exceeded both AA and BB levels for lead,iron and chromium, and additional treatment would be required prior to discharge.North American experience has shown that many metals can be removed incidentallyduring biological treatment processes. Based on the results of this experiment,it appears that higher strength, more complex, leachates’ metals are removed toa lesser extent through biological treatment, and therefore these leachatesrequire tertiary treatment for metals removal. Based on the literature surveyof potential physical/chemical treatment methods, precipitation with lime isprobably the most appropriate method.926.7 pHThe pH of the leachate was measured each week. While the author was in Taiwan,the pH of the filter effluent and RBC effluent were also measured weekly.Subsequently, the pH of the filter and RBC were measured on a less frequentbasis.The pH of the leachate, filter effluent, and RBC effluent are shown over time inFigure 26, and system pH data are provided in Appendix 4.The leachate pH ranged from 7.8 to 8.8 with a mean of 8.1. This is typical ofa methanogenic phase leachate. Filter effluent ranged from 8.0 to 8.6 with amean of 8.4. RBC effluent ranged from 7.2 to 9.3 with a mean of 8.5. Theobserved effect of increasing pH across the RBC during the early part of theexperiment was unexpected because nitrification results in the release ofhydrogen ions and is consequently acidifying. Szwerinski et al. (1986) verifiedthis theoretical result for a nitrifying biofilm.The phenomenon of increasing pH across a nitrifying biofilm was observed bySpengel and Dzombak (1991). They found a change in pH from 7.4 in the firststage of an RBC to 8.1 in the last stage (influent pH 7.8). They attributed theincrease in pH to high carbon dioxide concentration in the leachate prior toaeration. The carbon dioxide was present because of anaerobic decompositionwithin the landfill and degradation of organic substrates in the leachate. Duringaeration, the carbon dioxide was stripped from the leachate resulting in anincrease in pH.This phenomenon is explained in detail by Sawyer and Mccarty (1978), and is basedon the alkalinity equation shown in Equation 9.SystempHData10-9.5- 9-8.5-±7.5-*7-iIII020406080100120140160180200DayF-2.8ROF.e.1R.13.4jF.6ROF”8.OR-8IF”3.6R-eRawLeachate+FilterEffluent*RBCEffluentF•PeriodMeanInfluentFlow(Llday)R•PeriodMeanRecycle(L/day)FIGURE26:SYSTEMpH94EQUATION 9: ALKALINITY RELATIONSHIPCO2 + H20 + H2C03 * HC03 + HThe equilibrium relationship for carbonic acid, carbonate and hydrogen ion isshown in Equation 10.EQUATION 10: CARBONIC ACID EQUILIBRIUM RELATIONSHIP[H][HCO3j/2CO K1According to Sawyer and McCarty (1978), [H2C03] is the sum of the concentrationsof free carbon dioxide and carbonic acid. Free carbon dioxide represents 99% ofthe total. During aerobic treatment, carbon dioxide present in the leachate dueto organic decomposition processes is stripped off to equilibrium with the air.Since the total alkalinity remains constant (Sawyer and McCarty, 1978), thehydrogen ion concentration must drop, and the pH must therefore rise. Accordingto Sawyer and McCarty (1978), at 25 °C, for aerated water with 100 mg/L totalalkalinity as CaCO3, the equilibrium pH will be 8.6. A higher alkalinity wouldresult in a higher equilibrium pH.This phenomenon may not be observed if pH is not measured at the site. If thepH is measured on a stored sample, a higher carbon dioxide concentration may bepresent, and a lower pH would be observed. This effect can be seen in workcurrently being performed by the author in which site measurements of RBCeffluent pH are up to a unit higher than laboratory measurements.956.8 TOTAL ALKALINITYTotal alkalinity (titration to pH 4.5) was measured in the raw leachate, filtereffluent, and RBC effluent weekly from day 20 to day 62 of the experiment. Themeasured data are shown in Table 20.TABLE 20: TOTAL ALKALINITYDAY LEACHATE FILTER RBC REMOVALALKALINITY EFFLUENT EFFLUENTALKALINITY ALKALINITY(mg/L) (mg/L) (mg/L) (mg/L)20 10,980 10,980 2,630 8,35027 10,850 9,020 2,630 8,22034 11,100 8,650 3,510 7,59041 10,690 6,510 3,325 7,36548 10,800 6,770 4,490 6,31055 10,510 6,960 4,395 6,115Mean 10,820 3,500 7,320Mean ammonia removal for period = 1,790 mg/L (from Appendix 6)Table 20 shows that the alkalinity of the raw leachate was high. Ehrig (1989a)states that leachate typically has total alkalinity of 6,700 and ranges from 300to 11,500. Chang (1989), investigating the treatment of leachate from anotherlandfill in southern Taiwan, found a leachate alkalinity of 8,500. The leachateinvestigated by Chang (1989) was younger than the leachate used in thisexperiment (pH 7). More volatile fatty acids and consequently lower alkalinitywould therefore be expected.Since the waste characteristics of the landfill are unknown, the source of thehigh alkalinity is unknown.Based on the data in Table 20, the mean change in alkalinity as CaCO3 per unitammonia—N removed is 4.1 g/g. This is below the theoretical requirement of 7.14g/g for nitrification to nitrite or nitrate.96If one assumes that denitrification occurred in the RBC and anaerobic filter, thenet alkalinity requirement would be the requirement for nitrification minus thealkalinity gained from denitrification, which equals 3.57 gIg.Therefore, as previously discussed, the observed reduction in alkalinity tonitrogen removal ratio , compared to the theoretical requirement, could have beenthe result of concurrent nitrification/denitrification.6.9 ANIONSIn addition to nitrate and nitrite, anions including chloride and sulphate weremeasured in the leachate, filter effluent, and RBC effluent using an ionchromatograph (IC).Sample output from the IC is shown with each peak labelled in Appendix 8.In addition to the other anions analyzed, the IC standards also includedphosphate, but due to interference from the adjacent chloride peak, phosphatecould not be measured in any of the samples. Enough phosphate was added directlyto the RBC on a daily basis to ensure a BOD:N:P ratio of 100:5:0.5 wasmaintained, as suggested by Ehrig (1985). Leachate, filter effluent, and RBCeffluent values of chloride, nitrite, nitrate and sulphate are shown in Table 21.The results in Table 21 show that, although the mean leachate, filter effluentand RBC effluent chloride concentrations were not statistically equal at the 95%confidence level, they were close enough to indicate no removal occurred in thesystem. This is as expected, as chloride is not removed through aerobic oranaerobic biological treatment.TABLE21:ANIONDATALeachateFilterEffluentRBCEffluentDateC1’SO4N03N02C1’S042N03N02C1’S042N03N02(mg/L)(mg/L)(mg/L)001/13/9201/17/9201/27/9202/13/9202/21/9202/27/9203/02/9203/16/9203/23/9203/30/9204/06/9204/13/9204/20/9204/27/9205/04/92MeanSTD24002860249028201980252027501960208024402680000000100001000002900000026806001200025401002026906002023900002390001600282000029001400570025900002590004700272000030500107800247000028900089001940000210001068002690000289070270680283026006030302208086029200002920190808700 0 0222000027201503002300203010000275080806200.90251330072740756053030425524533531095%+—18317213998The results also show that sulphate was only present in the leachate and filtereffluent 20% of the time compared to 60% of the time in the RBC effluent.Nitrite and nitrate were not present in the leachate and only present 13% of thetime in the filter effluent, compared to 100% in the RBC effluent. This resultindicates that the leachate and filter effluent were generally fully reduced,containing no oxidized species. Oxygen/reduction potential measurements wouldbe required to confirm this hypothesis.6.10 RBC SPEEDRBC speed could not be controlled precisely because of the type of drive motorused, but was adjusted on an approximately daily basis to maintain a speedbetween approximately 10 and 25 RPM (6—16 rn/mm peripheral speed). RBC speeddata are provided in Appendix 4. Since nitrification rate has been shown todepend on RBC peripheral speed (because it controls dissolved oxygenconcentration and consequently oxygen transfer into the system (Hosomi et al.,1991)), future work should ensure RBC speed is kept constant.6.11 SUSPENDED SOLIDSEffluent suspended solids were not measured on a regular basis because RBC is afixed film process, and suspended solids are not a key design parameter. Fromthe system data provided in Appendix 4, the mean raw leachate suspended solidswas 220 mg/L, filter effluent suspended solids was 170 rng/L, and the meaneffluent suspended solids was 170 mg/L. Sludge recycle, rather than effluentrecycle, may have reduced effluent suspended solids since sludge would not havehad time to float, due to denitrification in the sludge. Sludge recycle was notused to avoid clogging the anaerobic filter.997. SUMMARY OF RESULTSThe leachate used in this experiment had BOD:COD ratio and pH typical of amethanogenic stage leachate. The leachate ammonia—N (mean of 2140 mg/L) anddissolved chromium (mean of 3.05 mg/L) were both particularly high compared toexpected values.1. Parameter removal in each of the RBC and anaerobic filter could not beaccurately calculated because removal values varied widely throughout theexperiment. This result can be attributed to insufficient stabilization timebetween changes in system flow. Overall system removal rates for each flowperiod could be determined.2. The period mean BOD removal rates ranged from 90—96%, with an overall mean of92%. The period mean COD removal rates ranged from 43—59%, with an overall meanof 49%. Period mean COD:BOD removal ranged from 2:1 to 5.1:1, with an overallmean of 3.7:1. BOO and COD removal were unaffected by flow.3. Ammonia removal throughout the experiment exceeded 80%, but at loading ratesgreater than 1.5 g/m2/day, mean effluent ammonia—N exceeded 100 mg/L, which wasconsidered unacceptable. At RBC loading rates less than 1.5 g/m2/day, 97% ammoniaremoval was achieved. Other authors have found nitrification at significantlyhigher loading rates, but lower influent ammonia concentration.4. Ammonia mass removal increased linearly at all RBC loading rates.5. Ammonia removal, on a percent removal basis, decreased with increasing massloading, influent hydraulic loading and total hydraulic loading. The linearregression parameter r2 was highest for total hydraulic loading at 0.67,indicating the best linear correlation to ammonia removal.1006. A long term (greater than 100 days) build—up of nitrite occurred in thesystem. RBC effluent nitrite concentrations averaged 530 mg/L.7. The mean total nitrogen removal in the RBC was approximately 54%, and thetotal system nitrogen removal was approximately 66%. Nitrogen removal appearedto be independent of flow.8. Overall mean removals for iron, zinc, lead, copper, cadmium, chromium andmanganese and nickel equalled 37%, 16%, 17%, 0%, 0%, —12%, —19% and 59%. Themajority of metal removal appeared to be in the anaerobic filter.9. system effluent metals levels exceeded B.C. Pollution Control Objectives forlead, iron and chromium.1018. CONCLUSIONS1. The system effectively removed BOD, but COD was not fully removed.2. RBC ammonia loading, rather than organic loading, was the critical designparameter for the system. Total hydraulic loading appeared to provide the bestcorrelation with ammonia removal.3. At RBC loading rates exceeding 1.5 g/m2/day, inhibition of nitrification wasobserved. At higher loading rates, although overall mass removal continued toincrease, full nitrification could not be achieved. High influent ammoniaconcentration was most likely responsible for the observed inhibition ofnitrification.4. Inhibition of Nitrobacter, resulting in a prolonged nitrite build—up, occurredin the system. The high influent ammonia concentration was most likelyresponsible for the inhibition of Nitrobacter.5. Nitrogen removal in the RBC can be attributed to either simultaneousnitrification/denitrification or air stripping of ammonia. It is most likely thatsimultaneous nitrification/denitrification caused the observed nitrogen removal.6. Low metal removals in the system was most likely the result of complexing ofthe metals with organics. The North Anierican experience of incidental metalremoval during biological treatment may not be the case for stronger, morecomplex, leachates. Additional physical/chemical treatment processes,potentially lime treatment, would be required to remove system metals toacceptable discharge levels.1029. IECOMHENDATIONSFuture work investigating RBC treatment of the leachate used in this experimentshould take the following recommendations into account:1. Off—gasses from the RBC should be analyzed to determine the fate of nitrogenin the system.2. Total metals should be analyzed.3. To determine if metals are complexing with organics, extraction of theorganics and subsequent metal analysis would be required.4. Nitrification inhibitors should be added to BOD analysis samples.5. Long term BOO tests should be conducted to determine if the seed issufficiently acclimated, to determine the ultimate BOO of the leachate, and todetermine if nitrification affected the BOD results.6. 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Journal of Water Pollution Control Federation, Vol. 52(3), pp. 610—621.109Date:Sample:StandardConcent.(mg/L)10 1 —3350 1.69897 —76100 2 —95200 2.30103 —113500 2.69897 —1361000 3 —155Unknown -77Linear RegressionRegression Output:Constant 27.3Std Err of Y Est 0.6R squared 1.00No. of Observations 6.0Degrees of Freedom 4.0X Coefficient(s) —60.8Std Err of Coef. 0.4LOG Unknown ConcentrationUnknown Concentration110APPENDIX 2: AMMONIA PROBE SAMPLE CALCULATIONS AND OUTPUT12/24/91RBC EffluentLOG ProbeConc. Reading(m)1.7252 mg/LC)r3ProbeReading(aid)3 3 C,C,i*CR(4CR(R)OIICRIIIIIIII-’111111t0’-’IOo%JIb)(joQlIIIJI(Il10111fl010111001IIL11111C’’WI-I’llO’bjflIIII 1.110(no101•1(40I(*01(401•m•I—’101IIIII—IlII......l0•II;.IIIIII.II-’‘-IJOa(4ICJIIlIIlliIIIII••“01CR#1.110IIIIIII\JOlI’IIaCR01III.I1td&U,a lota t,&OlCA•1CC(Ac•ICR,ICICR,M,aCAIa0I-’COJON0(IIIIIICIIflII-I-I,1*rII0JOIIIIIIIIIIIIMTI-’‘.1111111111110 \I-’ 10011111111111111111111111I—lI11111IJOJO-’I’I-’IIIIII(jill1011IO’MCII’-’* I-’ -D I [‘Ill•1II•II10111III’01 C10101IIIIII‘-I (MWTO (A CR 01 Sd 0 0 I-a TOIt z H Pd w S. 0 CD H C z C w ID.H t.N It C) H It H ‘-3 ‘.3 H 0 w ‘-3I-IH L.a‘HRIIIIIIIIII11111111111111111111IIIIAppendx4:Leachate,FilterEffluentandRBCEffluentData0.016.750.080026.790.120.420016400.170.410.019490.121.700016.440111,550.016.330.110.846.120.190.576.310.130.556.340.160.4914.651.306.000.435.340.425.890.515990.7911.301.046.700.47LeachateDataCollect.TimeInst.Cum.MeanpHAmmoniaTSSBODCODTotalTKNZincPbCdFeCuMnCrNiDateFlowFlowFlowAlkalinity(D)(D)(D)(D)(D)(D)(D)(D)(m3lhr)(m3)(m3/hr)(units)(mg/I)(mg/I)(mg/I)(mg/I>(mg/ICa>(mg/I>(mg/I>(mg/I>(mg/I)(mg/I>(mg/I)(mg/I)(mg/I)(mg/I)18/11/911030AM25/11/911000AM02/12/911030AM09/12/9110:30AM16/12/9110.30AM23/12/9110:30AM30/12/9110:30AM06/01/9210:30AM13/01/9210:30AM20/01/9210:30AM27/01/9210:30AM03102/9210:30AM10/02/9210:30AM17/02/9210:30AM24/02/921030AM02/03/9210.30AM09/03/9210:30AM16/03/9210:30AM23/03/9210:30AM30/03/9206/04/9213/04/9220/04/9227/04/9202)05/9210:30AMMean5.52316307.775.823272065818262334394.38.821156.72344175.88.524505.82357878.28.212606.62371988.479916306.92384717.67.8722855.52398067.97.98218572409827.0823106.2241837518.0221605.12431888.082535824788.225715.52474156.38.219096.52485366.7819848.219846.62517736.48.224038.227008888.216007.4279816292823136.228.398.142142.001965002224320441557634541.243434653707109801.167750601085024701.26630382011100325335049043371069036400.95330900562010800275508915310510247514532051910.9628198045190.992746204392097137620515410326054070150.49147470607915592052470,9021884171.183767999129113228127051760.962054621219.747050050398010821.672918.600.330290380.330.230310.240.230.310.020160,280,390260280203.350.213.200242.590.252.790.232.970.193.640.,492.703241912.751.—iAppendix4.Leachate,FilterEffluentandRBCEffluentDataREClnfluent/AnaerobcFilter EffluentDataCoilectDayLeachFilterP04RecyclpHAmmoniaSSTSFSODCODTotalTKNClorideSulfateFeZnPbCuCdMnCrNiDaleFlowTempFlowAkaI(D)(D)(D)(D)(D)(D)(D)(D)(I/day)(C)(I/day)(%)(units)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/ICa)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)09/12/911302015249012/12/9116280601985286313/1219117320.6016/12/91202.30.30172026017/12/912142040277518/12/9122500.502.20.3950.0550.0250.0150.282.47020519/12/912323040805147528201098020/12/91241702021/12/9125290608044752670902023/12/91270.30.8024/12/9128250608.01171513486502.910.4750.090.0750.010.242.4202125/12/91294.211026/12/91305.81.512.315852963192427/12/91315.71.528/12/9132610.730/12/91347.00.4852129024501/01/92365.60.002/01/9237600003/01/9238600.004/01/9239600.0689505/01/9240600006/01/92416.00010204908150760.140.10010422.95025.p07/01/92427800862111508/01/9243720.065612009/01/9244460.013.5124809380289110/01/92453.40012/01/92477.00.013/01/924833014/01/9249640.010304770.720.160090.010.592.8202915/01/925084816/01/925158112017/01/92527.114.4946770254012.620/01/92557021/01/92566.30104029022/01/92576319085696024/01/925967200433027/01/92625.81980207028/01/92636.32029/01/92648022346060.,810.2130/01/926560232390Appendix4.Leachate,FilterEffluentandRDCEffluentDataCollect.DayLeach.FilterP04RecyclpHAmmoniaSSTSFSBODCODTotalTKNClorideSulfateFeZnPbCuCdMnCrNiDateFlowTempFlowAkal.(D)(D)(D)(D)(D)(D)(D)(D)(I/day)(C)(I)day)(%)(units)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/ICa)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/i)(mg/I)31/01/92666,82303/02/9269542005/02/927121507/02/92731.52010/02/92761.2211922320460611/02)9277172112/02)92784.0203.,FilterEffluentandRBCEffluentDataCollectDayLeach.FilterP04RecyclpHAmmoniaSSTSFSSODCODTotalTKNClaudeSultateFeZnPbCuCdMnCrNiDateFlowTempFlowAkal.(D)(D)(D)(D)(D)(D)(D)(D)(I/day)(C)(I/day)(%)(Units)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/ICa)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(rrig/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)01/04/92127612802/04/921281900240283025503/04/92129582706/04/921326.8245862600130378108/04/9213466257921290220222.7909/04/92135291810/04/921366.22413/04/921396.324.5738431416/04/921429.82320/04/92146724521/04/921472623/04/9214935924/04/921503426.525/04/921512727/04/921538.2152071554.540.50.210.343.2128/04/921543.612729/04/9215530/04/921563.827221501/05/9215717023999216802/05/921583628.504/05/921603628.58.61517590906/05/9216234507/05/9216316383000202015808/05/9216437828.2Appenix4:Leachate,FilterEffluent andRBCEffluentDataRBCEffluentMeasuredfromtheFinalClarifierCollect.RBCpHSpeedAmmoniaSSTSFSGODCODTotalClorideNitriteNitrateSulfateFeZnPbCuCdMnCrNiDateTemp.Alkalinity(D)(D)(D)(D)(D)(D)(D)(D)(C)(units)(RPM)(mg/I)(mg/I)(mg/I)(mgIl)(mg/I)(mg/I)(mg/ICa)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)09/12/9172232912/12/9155235513/12/9115.516/12/911817/12/911920203218/12/911919.52.490.5150.,FilterEffluent andRBCEffluent DataCollect.RBCpHSpeedAmmoniaSSTSFSBODCODTotalClorideNitriteNitrateSulfateFeZnPbCuCdMnCrNiDateTemp.AIkaliniti(D)(D)(D)(D)(D)(D)(D)(D)(C)(units)(RPM)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/ICa)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)13)02/9216.517.8290056601361410219216.52117/02/921722.58020313718/02/921711.219/02/9216.5204.360.910.230.160.333.570.2720/02/921514.52593473021/02/921514.522102/921510.824/02/9213.57.819120423125/02/921611.526/02/9215.5145.,FilterEffluent andRBCEffluent DataCollect.RBCpHSpeedAmmoniSSTSFSBODCODTotalClorideNitriteNitrateSulEateFeZnPbCuCdMnCrNiDateTemp.Alkalinity(D)(D)(D)(D)(D)(D)(D)(D)(C)(units)(RPM)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/ICa(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)(mg/I)09/04/9229188668319410/04/92211968213/04/92203088470616/04/922119.517/04/92211820/04/92373621/04/92241231724/04/92241925)04)922614.527/04/928.26257300828/04/922421.563629/04/923.490.860.110.163.0430/04/922715.5271523229815201/05/928.1335436300021685171002/05/922619.504/05/922681946303005/05/9223507/05/922545615257708)05/9226.520.5Appendix5:BOOandCODDataBiochemicalOxygenDemandLeachateFilter EffluentRBCEffluentBODMeanBODMeanTreat.BODMeanTreat.OverallOverallDateDayFlowRecycleBODBOOEff.BOOEff.Treat.MeanEff.Treat.12Eff.(Llday)(Liday)(mgIL)(mg/L)(mg/L)(mg/L)(%)(mg/L)(mgIL)(%)(%)18/11/91-826/11/9102.70465368269502/12/9162.7009/12/91133.0016/12/91202.804652605623/12/91273.00475269530/12/91346.213.4630673245355-123447106959306/01/92415.913.4490490-210353039313/01/92486.013.4900330-172939220/01/92556.413.4I-27/01/92626.303206165183364909003/02/92696.5010/02/92761.5098032067140188617/02/92835.50620600320949724/02/92906.00620600320949702/03/92976.70540550-288868409/03/921048.2016/03/921115.508023/03/921186.269209203701088085-17919130)03/921256.96240829106/04/921326.36130909013/04/921396.56740889020/04/921469.8627/04/921533.56127012704151085757-12969604/05/921603.7607/05/921633.66Mean7054156392Notes:1.Filter TreatmentEfficiency=((Ce*R+Ci*l)-(R+l)*Cf)/(Ci*l)*1002.RBCTreatmentEfficiency=(Cf-Ce)*(R+l)/(Ci*l)*1 00=Influent flow(L/day)Ci=Leachateconcentration(mgIL)R=Recycleflow(Liday)Ce=Effluent concentration(mg/L)Cf=Filtereffluentconcentration(mg/L)Appendix5:BOOandCODDataLeachateFilterEffluentRBCEffluentMeanMeanCODMeanCODMeanTreat.CODN02MeanNO2MeanMeanTreat.OverallOverallDateDayFlowRecycleCODCODEff.NO2Adjust.CODAdjust.Eff.Treat.MeanCODCODEff.Treat.123Eff.(Llday)(Lfday)(mg/L)(mg/L)(mg/L)(mg/L)(%)(mg/L)(mg/L)(mg/L)(mgIL)(mg/L)(mg/L)(%)(%)(%)1533.561603.761633.66517548984621504071554898-19530104955-9630153000448131761.Filter TreatmentEfficiency((Ce*R+Cil)-(R+l)*CO/(Ci*l)*1002.AccordingtoStandardMethods(1985),nitriteproducesaCODof1.1g/gN02.Therefore,AdjustedCOD=COD-1.1NO2.MeanperiodNO2valuesareusedbecausenitritedataarenotavailableforallCODdata.3.RBCTreatmentEfficiency=(Cf-Ce)(R+I)I(Ci*l)*100I=Influent flow(Llday)CiLeachateconcentration(mgIL)RRecycleflow(L/day)Ce=Effluentconcentration(mg/L)Cf=Filtereffluentconcentration(mg/L)37551424443067250224761524.491435522658534947 49ChemicalOxygenDemand-8 0 6 13 20 2750002.70320540972.7041553.0034542.8037103.005060346.213.4415.913.4486.013.4556.413.4382045924337562018/11/9126/1119102/12/9109/12/9116/12/9123/12/9130/12/9106/01/9213/01/9220/0119227/01/9203/02/9210/02/9217/02/9224/02/9202/03/9209/03/9216103/9223/03/9230/03/9206/04/9213/04/9220/04/9227/04/9204/05/9207/05/92MeanNotes:62 69 76 83 90 97 1041116.30519051636.501.5045205.5043906.0051556.7070158.205.5047052713267527952670296529282890433052624605415576905850494046404995378043157245232340251960472130-122435-1172655302517 -2167053135-49423041053815-53450-263535366044374040470537351186.261256.961326.361396.561469.860214321432340196021307123572705262712025772229471625913401275056610204732485778358089234553165677280077783426183875295885927438662823378828185245722084158000481032234711585138432175483 797738438031-4951454076502266135347I—.59Appendix6’NitrogenDataNitrogenValuesLeachxteFilterEffluentRECEffluentDateDayFlowRecycl.Ammon.MeanAmmon.MeanAmmoNitrAmmon.MeanR8CMeanN03N02TotalMeanAmmoNitr.Over,Over.OverOver.Over.Ammon.Ammon,Treat.Treat,Ammon.AmmonRECNitrTotalTreat.TreatAmmoAmman.NitrMeanMeanEff.ElfLoadLoad.NitrElf.ElfTreat.Treat.Treat.AmmoNrtrElfElf.Treat.Treat123456Elf.Elf.(gIm2(gIrn”2(L)day)(Lfday)(mgIL)(mg1L)(mgIL)(mg1L)(%)(%)(mg/L)(mg/L)Id)Id)(rng/L)(mg/L)(mg/L)(mg/L)(%)(%)(%)(g/day)(%)(%)(%)270.0182618561772590.90997270.021151.03.00024501818641.379977280012600.62.70.0163022540.86.213.42285-475554542,62.55.913.42185-203802.46.013.42310-754502.56413.42160-7-54302.5630.0253518181801732.92.0650.0001.50.02478222200.7550.025704480266000191026261912167001985111125024820.077327305500198534341842.062602403-44-11327251272.96960251636.02700-82-481763.1656.09.86.026/11/91002/12191609/12/911316/12/912023/12/912730/12/913406/01/924113/01/924820/01/925527/01/926203/02/926910/02/927617/021928324/02/929002/03/929709/03/9210416/03/9211123/03/9211830/03/9212506/04/9213213/04/9213920/04/9214627/04/921533.56.01600195716111594-167-11004/05/921603.76.023131577-77-3207/05/921633.66.0Mean21421690-18-462521.01.315437559163626363965639767411.52561568117557988712223255210854901066NotesIFilterAmmoniaTreatmentEfficiency((AeR+Ai*l)-(II*l)*Af)/(Ail)1002FilterNitrogenTreatmentEfficiency=((NeR*AM)-(N+l)Af/(Ai1)1003.RBCammonialoading=Ai*l*.82/4.5/1000(basedon18%removedinfilter,meanofflowperiodthree)4.RBCAmmoniaTreatmentEfficiency=(I +R)(Af-Ae)l(l*Ai)*1005RECNitrogenTreatmentEfficiency(1-Ne/A1006SinceRSCnitrogenremovaliscalculatedbasedoninfluentnitrogentotheRECratherthanthesystem,filterplusRECremovaldoesnotequaloverallremovalAiMeaninfluent ammonia-N(mg/L)IInfluent flow(L/day)At=Meanfilter effluent ammonia-N(mg/L)Ne=Meaneffluent totalnitrogen(mg/L)R=Recycleflow(L/day)Ae=Meaneffluent ammonia-N(mgIL)TKNDataDateAmmTKNTKN/Amm.23/12/91163024701530/12/91228532531406/01/92218536401.713/01192231027551.220)01/92216024751.12235224420(X)172015951438115510671075104020701826192224791405176818371301192219282600225495974528123761180761028311612057687468111750224528757801179016234276875839315879266056656678711004770473553937897147810778979643090104908921142763587124276841496778705633911056477771151115713140861352894984859119483866112517557931658l— t’JI-’)Appendix7MetalDataMeanValues(mg/l)7.301010.270.130.010773.050224310.630.160090010433.170254.590.850.220130.010.323.410.27643-4-9-4-23-25-359371617-21415-8-1059-12-19LeachateAnaerobicFilterEffluentRBCEffluentDateDayFlowRecyc.FeZnPbCuCdMnCrNiFeZnPbCuCdMnCrNiFeZnPbCuCdMnCrNi(Liday)(Lfday)(mg/L)(mg/L)(rrig/L)(mgIL)(mg/L)(mg/L)(mg/L)(mg/L)(mg/L)(mg/L)(mg/L)(mg/L)(rng/L)(mg/L)(mg/L)(mg/L)(mg/L)(mgfL)(mg/L)(mg/L)(mglL)(mg/L)(mg/L)(mgIL)FilterIronRemov.(%)26/11/9102.7002/12/9172.7009/12/91133.006.751240.3300800116/12/91202.806.791160290.120020423350212200400.060030020.282470.212.490520.,702.590258.150.760.140,100.010,422.950.256.830.880.,130.010.522.900.265920/01/92556.413,427/01/92626306330960310110.010842970193.460600200060.010672810214650730200.014503/02/92696504180.9402210/02/92761.506120990.240190573640.203100500120090353190354917/02/92835.506310970.230130554100213820780.270130353780.234.360.910.233924/02/92906.006341030310160493820274750.840.280.140394090.295.181.270242502/03/929767014.650490.021302095160.890.080323.945040.820.076509/03/921048204520.430.100.820.1716103/921115506.000790.160430.225050.670.1423/03/921186.265340.900.280.423494460.780.214.0030/03/921256.9606/04/921326.365.891180.390512.705941.320.920.282.5413/04/921396.565.991290.260,793.2420/04/921469.8611.301130281.0419127/04/921533566.700960200472.754.540500210343213490860110163.04504/05/921603.760100160.160.243184.303.574.933.840460.360.330.380.240.370.330.310270.330.18I—)(J)Treatment (%)OverallTreatment (%)41384233Appendix7’Metal DataOverallTreatmentEfficiency(%)DateDayFlowRecyc.FeZnPbCuCdMnCrNi(Llday)(Llday)(mg/L)(mgIL)(mgIL)(mg/L)(mg/L)(mgIL)(mg/L)(mg/L)26/11/9102,70.002/12/917270.009/12/9113300016/1219120280.0635690505010025-223/12/91273.0006454744407210-230/12/91346.213.406/01/92415913.428758-8084-24-813/01192486013.4116-13-18066-4-1320/01/92556413.427/01)92626.3002724359045-7-7403/02/9269650010/02)9276150017)02/9283550.03160-234013-2924/02/9290600.018-2323-5022-29-2202/03/92976.70.066-67-25082-8409/03/921048.20016/03/921115.500161513141823/03/921186.26.0161325100-1530/03/921256.96.0-06/041921326.36.0-1-12-13645613/04/921396.56.020/04)92146986.027/04/921533.56.048104566-1104/05/921603.76.02: CLfl-tt’1N*•m2:‘-Vcii2:ciCmcid& & U +cici03&‘I—I‘- cicici ci ciVE +oci-ui-VIci-ci2:ciçci & U + ci-0i-W‘•-NUIaNLcII.4ajcirLtit.JGIJfla03ci(ei-P.O1N4--’j40N-LJ1cs(,tc4bioC>3.-CtF-I-.-2:0oVtjNfr’•r-1.02:I—-4—1V032:V2:030rmci ci ci 4ci>JaNNcicitOcii-U1i-NLfl0XIN4ø’”’iN—1.i cici ci ci ciVB +o:ci0vi-VI,ci ciaciaciU + ci-0I-.ciN—LUciO1Nci’-i)ciciciC0’J03Jci*(iiciNLUciaiL(1-.JN-ici‘3 V-I 1“4a-NNciJ1NN03‘0NNU(31ci‘JNNNI” 0.b.“4N CII.RNN.*-N.tJ1tCI•1.cl03N-da(IlciNO3N0NLJ1N4hNNtr.fl00L)1*0ciciciciciciL)l I. N‘—0NN-c’ciN(31NLi)i-’Cq(JlCflciJwNNciLU*’N00cli0103iJI,*I-C’ S cc -I 3. d-.. 13 is’0 p ‘ii -n r If’ z -1 0,I’. C,-c LI.’ 0(-a 0 3Li’ -i V z VC’-)0 NI— (.10 U 2: 0Co-.3V XI N I-i NrLI—ts,iiciw ‘I N 0—Iinainoa”iawvsHJVTDOIVWO}TllDMOl:9xiciaaav


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