301 17 Pilot Study of Aerobic Granulation for Wastewater Treatment Qi-Shan Liu and Yu Liu CONTENTS 17.1 Introduction 301 17.2 Startup of Pilot-Scale Aerobic Granular Sludge SBRs 302 17.2.1 Comparison of Pilot- and Laboratory-Scale SBRs 302 17.2.2 CharacteristicsofAerobicGranulesDevelopedinPilot-and Laboratory-Scale SBRs 305 17.2.2.1 Granule Size and Morphology 305 17.2.2.2 Settling Property 305 17.2.2.3 Physical Strength 306 17.2.2.4 Microbial activity 306 17.3 Startup of a Pilot-Scale SBR Using Stored Granules as Seed 306 17.4 Startup of a Pilot-Scale SBR Using Activated Sludge as Seed 310 17.5 Conclusions 311 References 311 17.1 INTRODUCTION Aerobic granulation technology has been applied for the high-efciency treatment of a wide variety of wastewater including toxic wastewater, and it has been demonstrated inpilot-scaleplants(deBruinetal.2004;deKreuk,deBruin,andvanLoosdrecht 2004;Liuetal.2005),whileitsfullscaleapplicationhasnotyetbeenreported. In industrial practice, the fast and easy startup of upow anaerobic sludge blanket (UASB) reactors can be realized by seeding anaerobic granules directly into the reactor.Thiswillsignicantlyreducethetimerequiredforanaerobicgranulation whichusuallytakes2to8months.Asimilarstartupstrategyisalsoapplicable in initiating aerobic granular sludge sequencing batch reactors (SBRs). Existing evidenceshowsthataerobicgranulescanbestoredoveraperiodof7weeks,andits activity quickly recovered (Zhu and Wilderer 2003), while J. H. Tay, Liu, and Liu (2002)alsofoundthataerobicgranulescanbestablystoredfor4monthsat4°C. Thesendingssuggestthatuseofthestoredaerobicgranulesasseedwouldbe feasible in full-scale operation of aerobic granular sludge SBRs. 53671_C017.indd 301 10/29/07 7:52:42 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC 302 Wastewater Purification 17.2 STARTUP OF PILOT-SCALE AEROBIC GRANULAR SLUDGE SBRS J.H.Tayetal.(2004)investigatedaerobicgranulationinapilot-scaleSBR.The pilot-scale aerobic granular sludge SBR was initiated by seeding mature aerobic granules harvested from a laboratory-scale SBR. 17.2.1 COMPARISON OF PILOT- AND LABORATORY-SCALE SBRS Theseedaerobicgranulesusedinthepilotstudyhadameandiameterof0.83mm (gure 17.1A). It was found that aerobic granules tended to disintegrate shortly after seedingintothepilot-scaleSBR,andlooseocsbecamedominantinthereactor onday5(gure17.1B).Asaresult,themeandiameterofbioparticlesdecreased to0.19mmandthesludgevolumeindex(SVI)increasedfrom19to175mLg –1 (gure 17.2A). However, compact aggregates were gradually re-formed on day 20, indicatedbyameandiameterof0.4mmandanSVIof63mLg –1 (gure 17.1C). Thegranulesizecontinuedtoincreaseuptoapeakvalueof1.4mmonday50,and nallystabilizedatthislevelwithanSVIofaround26mLg –1 (gure 17.2A). It can beseenthatthesteady-stategranulesinthepilot-scaleSBRhadacompactstructure similartotheseedgranules,buttheywerelargerinsize(gure17.1AandD).Unlike theevolutionofaerobicgranulesinthepilot-scaleSBR,aerobicgranulesinthelabo - ratory-scale SBR remained stable throughout the whole study period, indicated by relativelyconstantgranulesizeandSVI,andtherewasanincreaseinsizeduringthe rst 2 weeks (gure 17.2B). AB CD FIGURE 17.1 Morphologyofbioparticlesinthepilot-scaleSBRatday1(A),day5(B), day20(C),andday65(D).Scalebar:4mm.(FromTay,J.H.etal.2004.Proceedings of Workshop on Aerobic Granular Sludge, Munich, Germany.Withpermission.) 53671_C017.indd 302 10/29/07 7:52:43 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC Pilot Study of Aerobic Granulation for Wastewater Treatment 303 Theinitialincreaseingranulesizeinthelaboratory-scaleSBRwasprobablydueto Low biomass concentration would lead to fewer collisions among granules and weaker detachment from individual granule. Difference in granule size observed in the pilot- and laboratory-scale SBRs at steady state can likely be attributed to differ- entshearanddetachmentforcesinthetworeactors.Figure17.4showsthatmorebio- mass was retained in the bottom half of the laboratory-scale SBR, whereas an even biomass distribution was observed in the pilot-scale SBR. The high accumulation of granular sludge at the bottom of the laboratory-scale SBR would certainly increase the collision and detachment rate among the granule particles. Consequently, smaller granules were developed in the laboratory-scale SBR. As discussed in chapter 2, the size of aerobic granules is inversely correlated to the shear force generated by the airbubblesandcollisionsamongthesludgeparticles(J.H.Tay,Liu,andLiu2004). Thesizeofthegranulesdevelopedinthestablelaboratory-scaleSBRwassimilarto the seed granules (gure 17.2). The similarity in size is not unexpected because the reactor conguration and operating conditions were similar in the laboratory-scale SBR and the reactor used for precultivation of seed granules. The biomass concentration in both pilot- and laboratory-scale SBRs was the sameatthelevelof0.4gL –1 tration tended to gradually increase to 6.5 g L –1 intherst3weeksofoperationin both reactors. A drop in biomass concentration was observed in the period of day 30 0.5 1.0 1.5 2.0 Sludge Size (mm) 50 100 150 200 A 0.0 0.5 1.0 1.5 0 102030405060708090 100 Time (days) Sludge Size (mm) 0 50 100 150 B 0.0 0 SVI (mL g –1 ) SVI (mL g –1 ) FIGURE 17.2 Changesinmeandiameter(D)andSVI($)ofbioparticlesinthecourseof operationofapilot-scaleSBR(A)andalaboratory-scaleSBR(B).(DatafromTay,J.H.etal. 2004. Proceedings of Workshop on Aerobic Granular Sludge, Munich, Germany.) 53671_C017.indd 303 10/29/07 7:52:45 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC the relatively low sludge concentration when the reactor was started up (gure 17.3B). at the reactor startup (gure 17.3). The biomass concen- 304 Wastewater Purification to40,whichresultedfromareducedsettlingtimeintheSBRfrom5to2min.Obvi- ously, this would cause the washout of slow-settling sludge, leading to a temporary reductioninbiomassconcentration.Ontheotherhand,theshortersettlingtimealso exerted a stronger selection pressure on biomass, which in turn encourages the reten - tion of biomass with excellent settleability, as discussed in chapter 6. Consequently, the biomass concentration gradually increased over time and nally stabilized at 8.0gL –1 in both reactors. These results seem to indicate that the seed granules in the laboratory-scale SBR can be successfully maintained, and new granules can growimmediatelyafterthereactorstartup,whilegranulescanbelostbutre-formed shortlyfromdisintegratedgranulesinthepilot-scaleSBR. The distribution of biomass concentration along the reactor height was different in the pilot- and laboratory-scale SBRs (gure 17.4). The biomass was distributed rather evenly along the reactor height in the pilot-scale SBR, whereas more biomass was accumulated in the lower half of the laboratory-scale SBR. This may be due to the difference of hydrodynamic conditions in the two reactors. It is believed that the initial disappearance of aerobic granules and dominant growth of bioocs in the pilot-scaleSBRwaslikelylinkedtotheprevailinghydrodynamicconditionsdueto different reactor diameters. Moreover, the size and location of air diffusers in the column SBR would also affect the hydrodynamic ow pattern. However, the cycle 2 4 6 8 10 0 2 4 6 8 0 102030405060708090100 Time (days) B 0 A MLSS (g L –1 )MLSS (g L –1 ) FIGURE 17.3 Sludge concentration versus time in pilot-scale (A) and laboratory-scale (B) SBRs. (From Tay, J. H. et al. 2004. Proceedings of Workshop on Aerobic Granular Sludge, Munich, Germany.) 53671_C017.indd 304 10/29/07 7:52:46 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC Pilot Study of Aerobic Granulation for Wastewater Treatment 305 operation of SBR provides a selective process that allows for the gradual redevelop- mentofgranularbiomasswithgoodsettlingcharacteristics.Forinstance,ashort settlingtimepromotestheselectionoffast-settlingbioparticles. 17.2.2 CHARACTERISTICS OF AEROBIC GRANULES DEVELOPED IN P ILOT- AND LABORATORY-SCALE SBRS 17.2.2.1 Granule Size and Morphology Themeandiameterofaerobicgranulesdevelopedinthepilot-scaleSBRwas1.37mm 0.83mm.Aerobicgranulescultivatedinthelaboratory-scaleSBRhadasimilarsize astheseedgranules.Thesetwokindsofaerobicgranulesexhibitedasimilarmor - phologyintermsofaspectratioandroundness.Infact,averywidesizerangeof aerobicgranuleshasbeenreported,from0.2mmupto16mm(Morgenrothetal. 1997;J.H.Tay,Liu,andLiu2001;Zhengetal.2006). 17.2.2.2 Settling Property Aerobicgranulesinthepilot-scaleSBRhadanSVIaslowas26.5mLg –1 andahigh specicgravityof1.017,whiletheSVIwas34.4mLg –1 andspecicgravitywas 1.015forthosegranulescultivatedinthelaboratory-scaleSBR.Thevolatilesolids contentofgranulesinthepilot-scaleSBR(62.4%)waslowerthanthatofgranules cultivatedinthelaboratory-scaleSBR(74.9%).Thisindicatesasignicantaccumu - lation of inorganic materials in the granules developed in the pilot-scale SBR. The higherinorganiccontentwaspartiallyresponsiblefortheobservedlowSVI. 0 20 40 60 80 100 120 140 012345 Reactor Height (cm) 0 20 40 60 80 100 120 140 0102030 Reactor Height (cm) Biomass Concentration (g L –1 ) (b)(a) Biomass Concentration (g L –1 ) FIGURE 17.4 Sludge distribution along the reactor height during the rst day (A) and at steady state (B). D:pilot-scaleSBR; : laboratory-scale SBR. (From Tay, J. H. et al. 2004. Proceedings of Workshop on Aerobic Granular Sludge, Munich, Germany.) 53671_C017.indd 305 10/29/07 7:52:47 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC (table17.1),whichwaslargerthanthatoftheseedgranuleswithatypicalsizeof 306 Wastewater Purification 17.2.2.3 Physical Strength Thephysicalstrengthofaerobicgranules,expressedasintegritycoefcient,was 96.0% in the pilot-scale SBR and 96.9% in the laboratory-scale SBR, that is, aerobic granulesdevelopedinthelaboratory-scaleSBRwerecomparablewiththoseinthe pilot-scale SBR. 17.2.2.4 Microbial activity The specic oxygen uptake rate (SOUR) as an indicator of microbial activity was 74.1 mg O 2 g –1 volatile suspended solids (VSS) h –1 forgranulesinthepilot-scaleSBR and80.6mgO 2 g –1 VSS h –1 for the granules in the laboratory-scale SBR (table 17.1). The slightly low microbial activity of aerobic granules in the pilot-scale SBR is thoughttobesize-related.Infact,thelimitationofmasstransportanddiffusionis generallymorepronouncedforlargergranules,whichwouldresultinlowmicrobial activity,asdiscussedinchapter8.Itisapparentthatuseoffreshaerobicgranulesas seed is feasible to quickly start up an aerobic granular sludge SBR. 17.3 STARTUP OF A PILOT-SCALE SBR USING STORED GRANULES AS SEED Liuetal.(2005)usedaerobicgranulesthathadbeenstoredfor4monthstoinitiate apilot-scaleSBR,andfoundthattheseedgranulesweremaintainedstably,andnew granulescouldbesuccessfullyformedthereafter.Thesizeofgranulesgradually increasedfrom1.28to1.7mmwithin1week(gure17.5),andthendecreasedtoa size similar to the seed granules. Similar to gure 17.2B, the initial increase in granule sizeisduetothefewercollisionsamonggranulesandsubsequentweakdetachment, becauseoflowbiomassconcentrationinthereactorintheinitialperiod.Newgranules begantoformafterday5,andbiomassconcentrationgraduallyincreasedaccordingly (gure 17.6). TABLE 17.1 Characteristics of Aerobic Granules Cultivated in Pilot-Scale and Laboratory-Scale SBRs. Items Pilot-Scale SBR Laboratory-Scale SBR Mean diameter (mm) 1.37 (± 0.09) 0.89 (± 0.07) Aspect ratio 0.67 (± 0.16) 0.69 (± 0.15) Roundness 0.69 (± 0.15) 0.69 (± 0.16) SVI (mL g –1 ) 26.5 (± 5.9) 34.4 (± 6.9) Specic gravity 1.017 (± 0.0005) 1.015 (± 0.0005) VSS/SS (%) 62.4 (± 2.8) 74.9 (± 3.6) Integrity coefcient (%) 96.0 (± 2.0) 96.9 (± 2.5) SOUR (mg O 2 g –1 VSS h –1 ) 74.1 (± 12.4) 80.6 (± 18.2) 53671_C017.indd 306 10/29/07 7:52:47 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC Pilot Study of Aerobic Granulation for Wastewater Treatment 307 Abiomassconcentrationofthestoredaerobicgranulesof1.03gL –1 was initially seeded into the pilot-scale SBR, and remained unchanged in the rst 4 days. After- wards,itgraduallyincreasedtoastablelevelof6.0gL –1 .Itshouldbepointedoutthat the pilot-scale SBR was initiated with an initial biomass concentration of 1.03 g L –1 andlowinuentCODof400mgL –1 .Thisresultedinagranulesurfaceloading rateof8.7gCODm –2 d –1 at the beginning of the study, as shown in gure 17.7. The granulesurfaceloadingratethenuctuatedfrom6.5to11.0gCODm –2 d –1 till day 6, depending upon the biomass concentration in the reactor and the organic loading rate applied. At steady state, the surface loading rate dropped to 1.4 g COD m –2 d –1 because of the high biomass concentration in the reactor. It is mostly likely that a highgranulesurfaceloadingratewouldpromotethegrowthofsuspendedbacterial cellsinsteadofgranules.Thus,alowgranulesurfaceloadingratemightbeapplied forthereactorstartupinordertopreventtheoutgrowthofsludgeocs,particularly during the initial period. 1.0 1.2 1.4 1.6 1.8 0 10203040 Time (days) Size (mm) FIGURE 17.5 Sludge particle size versus operation time in the pilot-scale SBR. (From Liu,Q S.etal.2005.Environ Technol 26:1363–1369.Withpermission.) 0.0 2.0 4.0 6.0 8.0 0 10203040 Time (days) 0 50 100 150 200 250 SVI (mL g –1 ) Biomass Concentration (g L –1 ) FIGURE 17.6 Biomass concentration ( )andSVI(D) versus operation time in the pilot- scaleSBR.(FromLiu,Q S.etal.2005.Environ Technol 26:1363–1369.Withpermission.) 53671_C017.indd 307 10/29/07 7:52:49 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC 308 Wastewater Purification Theseedaerobicgranulesafter4monthsofstoragehadaSOURof13.4mgO 2 g –1 VSS h –1 (gure 17.8). After 2 days of cultivation in the pilot-scale SBR, the SOUR increasedto94.5mgO 2 g –1 VSS h –1 , which is comparable to that of fresh aerobic granules. These results clearly showed that the stored aerobic granules can be revived withafullrecoveryofmicrobialactivitywithin2days.Theshortrecoverytimeof themicrobialactivityofstoredgranuleswouldbeverymuchadvantageousforits applicationinindustrialpractice.Seedgranuleshadalightgreycolorwithablack core (gure 17.9A), which is suspected to be due to the sulde generated by sulfate- reducing bacteria during storage, while fresh aerobic granules often have brown - ish-yellow color. However, after 2 days of reviving, the apparent color of the stored Figure 17.10 shows the reactor performance of the pilot-scale SBR in terms of inuent and efuent COD. The reactor was initiated by supplying an inuent COD of400mgL –1 ,andaftertherstSBRcycle,theefuentCODwas173mgL –1 .With FIGURE 17.8 Activityrecoveryofstoredaerobicgranulesduringtheoperationofthepilot- scaleSBR.(FromLiu,Q S.etal.2005.Environ Technol 26:1363–1369.Withpermission.) 0.0 4.0 8.0 12.0 040302010 Time (days) Surface Loading Rate (g m –2 d –1 ) FIGURE 17.7 Granule surface loading rate versus operation time. (From Liu, Q S. et al. 2005. Environ Technol 26:1363–1369.Withpermission.) 53671_C017.indd 308 10/29/07 7:52:50 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC aerobicgranulesturnedtothatoffreshgranules(gure17.9B). 0 50 100 150 200 0 10 20 30 40 Time (days) SOUR (mg O 2 g –1 h –1 ) Pilot Study of Aerobic Granulation for Wastewater Treatment 309 the gradual recovery of granule microbial activity, the efuent COD decreased to 82 mg L –1 after1dayofSBRoperation,andfurtherto60mgL –1 at the end of the second day. The inuent COD was increased to 550 mg L –1 onday4andfurtherto 800mgL –1 onday7becauseaerobicgranuleactivityhadbeenfullyrecoveredand newgranuledevelopmentwasalsoobserved.Itappearsfromgure17.10thatthe increase in the inuent COD had little impact on the removal efciency, and stable efuent COD concentration of 37 mg L –1 was recorded, corresponding to a COD removal efciency of 96%. Successfulstartupofthepilot-scaleaerobicgranularsludgeSBRbyseeding stored granules was demonstrated to be feasible. The microbial activity of stored granulescanfullyrecoveredwithin2days.Infact,thegranulescultivatedfrom benign substrates, such as acetate, can be used as the microbial seeds to produce granules to degrade toxic substrates, such as phenol (S. T. L. Tay et al. 2005). This FIGURE 17.9 Apparentcolorsofstoredaerobicgranules(A)andthoseafter2daysof reviving (B). (From Liu, Q S. et al. 2005. Environ Technol 26:1363–1369.Withpermission.) 0 200 400 600 800 1000 0 10203040 Time (days) COD Concentration (mg L –1 ) FIGURE 17.10 COD concentration proles observed in the pilot-scale SBR seeded with stored aerobic granules. : inuent; D:efuent.(FromLiu,Q S.etal.2005.Environ Technol 26:1363–1369.Withpermission.) 53671_C017.indd 309 10/29/07 7:52:51 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC 310 Wastewater Purification furtherextendstheapplicationofseedgranulestoothertypesofwastewaterortoxic wastewater treatment. 17.4 STARTUP OF A PILOT-SCALE SBR USING ACTIVATED SLUDGE AS SEED Aerobic granulation directly from activated sludge ocs with municipal wastewater wassuccessfullydemonstratedinapilot-scaleplantintheNetherlands(DeBruin etal.2004).TwocolumnSBRs6minheightand0.6mindiameterwereoperated in parallel treating wastewater at a ow rate of 5.0 m 3 h –1 (gure 17.11). Forma- tionofaerobicgranuleswithanSVIof55mLg –1 couldtakeplaceinafewweeks. Granularsludgealsohadagoodcapabilityfortheremovalofnitrogenandphosphate present in the municipal wastewater. It was found that pretreatment to remove sus - pendedsolidparticlesinordertoimprovegranulationandthepost-treatmentmight be needed so as to satisfy the stringent discharge limits. It appears that there will be noproblemforaerobicgranulationfrombioocsinpilot-scaleSBRs. Two parallel column reactors FIGURE 17.11 AerobicgranularsludgepilotplantinstalledintheNetherlands.(From DeKreuk,M.K.,DeBruin,L.M.M.,andvanLoosdrecht,M.C.M.,2004.Paperpresented at IWA Workshop on Aerobic Granular Sludge, Munich, Germany.) 53671_C017.indd 310 10/29/07 7:52:53 AM © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor & Francis Group, LLC [...]... of Aerobic Granulation for Wastewater Treatment 311 17. 5 CONCLUSIONS Aerobic granulation in pilot-scale SBRs is an important step for its full application in the industrial-scale plant Aerobic granular sludge SBRs can be initiated by seeding either fresh or stored aerobic granules The microbial activity of stored aerobic granules can be quickly recovered within a short time of 2 days Meanwhile, aerobic. .. Benjamin, M., and Tay, J H 2005 Startup of pilot-scale aerobic granular sludge reactor by stored granules Environ Technol 26: 1363–1369 Morgenroth, E., Sherden, T., van Loosdrecht, M C M., Heijnen, J J., and Wilderer, P A 1997 Aerobic granular sludge in a sequencing batch reactor Water Res 31: 3191–3194 Tay, J H., Liu, Q.-S., and Liu, Y 2001 Microscopic observation of aerobic granulation in sequential aerobic. .. Microbiol 91: 168 175 Tay, J H., Liu, Q.-S., and Liu, Y 2002 Characteristics of aerobic granules grown on glucose and acetate in sequential aerobic sludge blanket reactors Environ Technol 23: 931–936 Tay, J H., Liu, Q.-S., and Liu, Y 2004 The effect of upflow air velocity on the structure of aerobic granules cultivated in a sequencing batch reactor Water Sci Technol 49: 35–40 Tay, J H., Liu, Q.-S., Liu, Y.,... of aerobic granulation in pilot- and laboratory-scale SBRs Proceedings of Workshop on Aerobic Granular Sludge, September 27–28 Munich, Germany Tay, S T L., Moy, B Y P., Jiang, H L., and Tay, J H 2005 Rapid cultivation of stable aerobic phenol-degrading granules using acetate-fed granules as microbial seed J Biotechnol 115: 387–395 Zheng, Y M., Yu, H Q., Liu, S H., and Liu, X Z 2006 Formation and instability... a short time of 2 days Meanwhile, aerobic granulation directly from bioflocs as seed has also been demonstrated in the pilot plant Results from the pilot studies show that aerobic granulation is a promising technology for wastewater treatment due to its compact footprint, lower sludge production, and simultaneous organic and nutrient removal REFERENCES de Bruin, L M M., van Der Roest, H F., De Kreuk,... 2004 Promising result pilot plant research aerobic granular sludge technology at WWTP Paper presented at IWA Workshop on Aerobic Granular Sludge, September 27–28 Munich, Germany de Kreuk, M K., De Bruin, L M M., and van Loosdrecht, M C M 2004 Aerobic granular sludge: From idea to pilot plant Paper presented at IWA Workshop on Aerobic Granular Sludge, September 27–28 Munich, Germany Liu, Q.-S., Liu,... S H., and Liu, X Z 2006 Formation and instability of aerobic granules under high organic loading conditions Chemosphere 63: 179 1–1800 Zhu, J R and Wilderer, P A 2003 Effect of extended idle conditions on structure and activity of granular activated sludge Water Res 37: 2013–2018 © 2008 by Taylor & Francis Group, LLC © 2008 by Taylor 311 53671_C 017. indd & Francis Group, LLC 10/29/07 7:52:53 AM . Wastewater Treatment 311 17. 5 CONCLUSIONS Aerobicgranulationinpilot-scaleSBRsisanimportantstepforitsfullapplication intheindustrial-scaleplant.AerobicgranularsludgeSBRscanbeinitiatedbyseed- ing. SBRS J.H.Tayetal.(2004)investigatedaerobicgranulationinapilot-scaleSBR.The pilot-scale aerobic granular sludge SBR was initiated by seeding mature aerobic granules harvested from a laboratory-scale SBR. 17. 2.1. 301 17 Pilot Study of Aerobic Granulation for Wastewater Treatment Qi-Shan Liu and Yu Liu CONTENTS 17. 1 Introduction 301 17. 2 Startup of Pilot-Scale Aerobic Granular Sludge SBRs 302 17. 2.1