Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving b Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving b

Inhibition and recovery of nitrification in treating real coal gasification wastewater with moving b

  • 期刊名字:环境科学学报(英文版)
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  • 论文作者:Huiqiang Li,Hongjun Han,Maoan
  • 作者单位:State Key Laboratory of Urban Water Resources and Environment
  • 更新时间:2020-06-12
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° Science directental Sciences 2011, 23(4)568-5Inhibition and recovery of nitrification in treating real coal gasificationwastewater with moving bed biofilm reactorHuiqiang Li, Hongjun Han, Maoan Du, Wei Wangtate Key Laboratory of Urban Water Resources and Emvironment, Harbin institute of Technology, Harbin 150090, China.Received 04 May 2010; revised 18 July 2010: accepted 19 July 2010AbstractMoving bed biofilm reactor(MBBR) was used to treat real coal gasification wastewater Nitrification of the MBBR was inhibitedalmost completely during start-up period, Sudden increase of infuent total NH; concentration was the main factor inducing nitrificationinhibition. Increasing DO concentration in the bulk liquid(from 2 to 3 mg/L)had little effect on nitrification recovery. Nitrification ofthe MBBR recovered partially by the addition of nitrifying sludge into the reactor and almost ceased within 5 days. Nitrification ratioof the MBBR achieved 65% within 12 days by increasing dilute ratio of the influent wastewater with tap water. The ratio of nitrificationdecreased to 25% when influent COD concentration increased from 650 to 1000 mg/L after nitrification recovery and recovered 70%Key words: moving bed biofilm reactor; coal gasification wastewater; nitrification inhibition; nitrification recoveryDoI:l0.1016S10010742(10)60494Citation: LiHQ. Han H J, Du M A, Wang W, 2011. Inhibition and recovery of nitrification in treating real coal gasification wastewaterwith moving bed biofilm reactor Jourmal of Environmental Sciences, 23 (4): 568-574Introductionfor the treatment of high strength ammonia wastewater(Yun and Kim, 2003; Kim et al., 2003: Peng et al ., 2004)Coal gasification wastewater is generated in the process Nitrification requires two bacteria populations performingof coal gas purification and contains large quantities of two series processes which are the oxidation of ammoniaorganic and inorganic pollutants(Ye et al., 2002). Main to nitrite by the ammonia oxidizing bacteria(AOB)andpollutants in the wastewater are phenolic compounds the oxidation of nitrite to nitrate by the nitrite oxidizingwhich can inhibit biotransformation(Hill and robinson, bacteria(NOB). NOb are more sensitive to free ammonia1975)and ammonia which is one of the worst contamina- in the range of 0. 1-1.0 mg/L while AOB are inhibited bytors for aquatic life in the form of free ammonia(Effler et free ammonia in the range of 10-150 mg/L Nitrificationcan be incomplete or even ceased if free ammonia level isBiological treatment is widely used to treat the wastew- high( Ganigue et al., 2007)ater after being pretreated by the processes of ammonia Nitrification can be affected in treating wastewater con-stripping and phenols solvent extraction to reduce the taining organic pollutants for oxygen shortage( Figueroaoncentration of toxic compounds(zhang et al., 2006). and Silverstein, 1992). Moreover, heterogeneous bacteriaAmmonia is usually removed by autotrophic nitrification compete with nitrifying bacteria for available oxygen andwhich is sometimes affected severely in the presence of nourishment in the reactor. The oxygen saturation coef-high organic content and inhibitory compounds contain- ficients were found to be 0.3 g O2/mfor AOB and 1.1ing in the wastewater( Gupta and Gupta, 2001; Okabe g O/mfor NOB (Wiesmann, 1994). Ruiz et al.(2003and Ozawa, 1996), because the activity and growth reported that do had no infuence on nitrite accumulationof autotrophic nitrifying bacteria are suppressed easily at 5.7-2.7 mg/L, a temporal accumulation of nitrite wasby fast-growing heterogeneous bacteria(Ling and Chen, happened at do of 1.7 mg/L, and both nitrite accumulation2005). Ammonia removal of the coal gasification wastew- and中国煤化工 at Do of05mgLater avoiding environmental damage is a complicatedprocess and all pollutants must be treated simultaneously (VazqCNMHGAuctuation (Fdiand effectivelyPolanco et al, 1994), nitrifying bacteria being washed outFree ammonia is an important factor in the nitrification in suspension systems( blackburne et al., 2007), can alsosCorrespondingauthorE-mail:Han13946003379@163.cominduce nitrification inhibition. Attached biofilm systemsInhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactorhave high sludge retention time and less sensitivity to solvent extraction processes to facilitate subsequent bio-the change of environment which are suitable for treating logical treatment. Properties of the pre-treated wastewaterwastewater containing high strength ammonia and in are shown in Table l. As can be seen, concentrations ofhibitory compounds. At the same time, a continuous stirred pollutants in the wastewater changed greatly. One or sev-tank reactor(CSTR) is recommended to avoid abnormal eral pollutants might increase abruptly beyond the givenincrease of inhibitory compounds concentration in some range because of abnormal operation of the pre-treatmentparts of the reactor(Kim et al., 2006).Nitrification can be affected either inupended wastewater treatment systems and some adjust-Table 1 Properties of experimental wastewaterments of the system should be done to recover nitrification.ParameterRangeMeanNitrification recovery is more difficult in the suspendedsystem than in the adhered system because the nitrifying COD(mg/L)15002500bacteria are more susceptible in suspended form. Kim NH+-N(mg/L)100-250et al. (2009) pointed out that nitrification was almost Total phenol (mg/L)300600ceased in treating coke plant wastewater in a full-scaletreatment process for shorting of alkalinity and nitrificationvas not recovered by adding NaHCO,. Kim et al.( 2007) 1.3 Experimental setupreported that a full-scale suspended nitrification process The MBBR was operated at(33* 1)C. DO concen-was instable in summer due to washing out of nitrifiers tration in the bulk liquid of the reactor was controlledby fast growth of competitive microorganisms at higher at(1.5+0.2)mg/L by regulating air flow rate to keeptemperature with increasing phenol and thiocyanate con- partial nitrification to nitrite in the reactor Inoculum sludgecentrations. Adhered system is suitable for nitrification of the mbbr was collected from full-scale activatedbecause the nitrifying bacteria grow adhering to carrier and sludge process treating the coal gasification wastewateree et al.(2004) repin the coal gasification factory. Sedimentation pond withthat nitrification of the nitrifying biofilm was affected I L volume was used to separate sludge from effluentwhen it had been exposed to organic carbon-containing wastewater by gravity. Part of sludge at the bottom ofwastewater for a prolonged period and was recovered the sedimentation pond was recycled into the MBBRfor heterotrophic biofilm deterioration after the substrate maintain the suspended sludge retention time around 30shifting from acetate to ammoniadays during start-up period.In this study, a moving bed biofilm reactor(MBBR)wasCarrier filling ratio was an important factor affectingused to treat real coal gasification wastewater because of MBBR performance Increasing carrier filling ratio wouldits high capacity on mixing and tolerance to the inhibitory elevate biomass in the reactor. and enhance the collisioncompounds. Nitrification ratio of the MBBR increasedamong carriers. Wang et al.(2005)studied carrier fillinggradually at the beginning of start-up period and almost ratio varied from 10% to 75% using suspended carrierceased suddenly. Possible factors inhibiting nitrification of biofilm reactor, and the optimum carrier concentration wasthe mbbr were disced Some adjustments of the reac- 50%. At the same time, high carrier filling ratio neededtor operation conditions were also performed to investigate high air flow rate to assure carriers movement in the reac-the feasible method to recover nitrificationtor. Low air flow rate was used to control do concentrationaround 1.5 mg/L in the reactor, thus, carrier filling ratio1 Materials and methodsof the MBBr was 40% in the experiment to maximizethe biomass on the premise of carriers movement in the1.1 Moving bed biofilm reactorreactorThe MBBR used had a working volume of 4 L withInfluent of the MBBR, supplied at a rate of 0. 13 L/hr,cylindrical shade, with height 30 cm and radius 14 cm. was diluted with tap water based on COD concentrationThe reactor did not use stirred device and movement of of the pre-treated coal gasification wastewater. Sodiumcarriers depended on aeration solely. Compressed air wbicarbonate(1 g/L) was added into the feed of the MBBrsupplied at the bottom of the reactor using four separate serving as inorganic carbon source to support nitrifyingdiffusers with adjustable valve each. Such configurationwould prevent anoxic zone in the reactor at low air flow 1.4 analytical methodslene and the density was about 0.98 kg/m The carrier The samples were taken from effiuent of the MBBrhad cylindrical shape with cross configuration inside and every day and were analyzed immediately after filteredbiofilm grew on the inner surface of the carrier.through 0.45 um filter paper. Soluble COD, total phenol1.2 Coal gasification wastewater中国煤化工n were measuredInDO and ph in theThe coal gasification wastewater used in the experimentbulkCN Gen meter(Model 58was collected from Harbin Coal Gasification Factory andYSI Instrument Company, USA), and pH meter(PHS-31had been pre-treated by ammonia sapping and phenols Ltd, China) respectively570Joumal of Environmental Sciences 2011, 23(4)568-574/ Huiqiang Li et al2 Results and discussiontion Influent and effluent total phenol concentration of thereactor had no obvious variety during nitrification inhibi-2.1 Nitrification inhibitiontion period, thus, nitrification inhibition of the MBBr musto Nitrification ratio of the MBBR increased gradually not be caused by phenolic compoundsuring start-up period and reached approximately 35%TNH3 in the wastewater has two forms which areafter 25 days. Oxidation of total ammonia was almost ammonium(NH4*-N) and free ammonia(NH3-N). NH3-NNO2-N(Fig. la), and effluent NO2-N concentration concentration, relevant to total ammonia concentration,achieved 25 mg/Ltemperature and ph value, wavas an often mentioned fac-t. The mBBr had good effects on COD and total phenol tor affecting nitrification. NH3-N concentration could beoval at the beginning of the experiment because thecalculated by the following equation(Anthonisen et alfor more than one year( Fig. 1b). Effuent COD concen-tration was in the range of 200-250 mg/L when infuentCOD concentration was 1000 mg/L Influent total phenol INu N exp/633TNH:. 10PHconcentration was fluctuated from 150 to 250 mg/L andeffluent was stable after 20 daysInfluent TNH3 concentration of the mbbr did notNitrification ratio decreased suddenly at day 29 and control at the beginning of start-up period and increased toalmost ceased within 4 days. Operation conditions of the 200 mg/L abruptly(Fig. la)on day 30, although influentreactor, such as DO concentration and temperature, were wastewater was diluted almost twice to control influentnormal through out the period of nitrification failure. Thus, COD concentrationnitrification failure was not due to failure of aeration and NH3- n concentration based on effluent TNH3 concen-heater. Wett and Rauch(2003)pointed out that inorganic tration and ratio of NH3-NTNH3 are shown in Fig. 2.carbon limitations may be the main reason for decrease NH3-N concentration in the reactor was around 5 mg/L atof nitrifying bacteria activity. Scarcity of inorganic carbon the beginning of the experiment and increased to 40 mg/Lcould not be the factor affecting nitrification because sharply for sudden increase in infuent TNH, concentra-NaHcO, was added into the influent of the reactor in theexpenmentPhenolic compounds were another factor inducing nitri-fication inhibition at certain concentration. Dyreborg and40F.NH3-N/TNH,Arvin(1995)indicated that pseudo-critical concentrationbacteria; Kim et al. (2008)reported that threshold phenolconcentration for inhibiting nitrification was 200 mg/Lin treating cokes wastewater with batch activated sludge 8 20 hibitory concentration for AOdsystem. Tremendous difference of the phenol inhibi- zhtion concentration would be due to different operationconditions. Extended aeration process was used in theexperiment, and influent total phenol concentration was inbitory concentration for NOBthe range of 150-250 mg/L. Nitrification ratio increased51015202530gradually( Fig. Ib), which indicated that nitrification of theMBBR could be achieved at such total phenol concentra- Fig. 2 NH3-N concentration and ratio of NH3-N/TNH, before and after20 fluent TNH· Effluent NO, -Nfluent COD Influent total phenolo Effluent COD o Effluent total phenol18000010中国煤化工CNMHGTime( day)Time(day)Fig. 1 Total ammonia removal (a)and COD and total phenol removal b)of the MBBR before and after nitrification inhibition.nhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactor571tion. Ratio of NH3-N/TNH3 achieved 38% when TNH3 do concentration from 2 to 3 mg/L(Fig 3). Influent CODconcentration increased sharply. Free ammonia inhibition concentration was well controlled around 1000 mg/Leffect on the activity of the AOB during nitrification was TNH3 and total phenol concentrations were in the normalstudied by many researchers and inhibition concentration range compared with the level before nitrification inhibi-was different greatly (10-150 mg/L)(Kim et al., 2006). tion COD and total phenol removal of the mBBr wasIn our experiment, NH3-N concentration around 10 mg/L enhanced a little with the increase in DO concentration.had no obvious inhibitory effect on nitrification(Fig. 2). Dissolved oxygen consumed by heterogeneous bacteriaThe faster growing heterogeneous bacteria would be es- had no obvious increase for the limit of available organictablished at the outer biofilm layer while slower growing pollutants in the influent. Thus, available oxygen in thenitrifying bacteria would be developed near the attachment deeper layer of the biofilm was increased for the nitrifyingsurface in treating high C/N ratio wastewater. This arrange- bacteria.ment increased mass transfer resistance formonia toThe increase of do concentration in the mbbr wasbe diffused into the deeper lying nitrifying biofilm layer achieved by increasing air flow rate at the bottom of theand the configuration would decrease NH3-N inhibitory reactor. Biofilm sloughing would be enhanced with theeffect on the nitrifying bacteria Nitrification of the MBBr increase of air flow rate. In our study, we wanted to knowwas almost ceased while NH3-N concentration increased whether the activity of nitrifying bacteria was recoveredto 40 mg/L suddenly which indicated that the activity by increasing DO concentration based on the configurationof the AOB was inhibited almost completely. Ratio of of the biofilm, and DO concentration should be increasedNH3- N/TNH3 was highest as well. Thus, NH3-N inhibition at certain range to prevent badly breakage of the biofilmwas the main reason inducing nitrification failure of the At the same time, the aim of the experiment was toMBBR during start-up periodachieve partial nitrification at low DO concentration Being2.2 Nitrification recoveryexposed at high do concentration for long time wouldshift partial nitrification to complete nitrification in theAlthough NH3-N concentration decreased around 10 reactor, thus, period of increase DO concentration shouldmg/L soon after the sharp increase by replacing influent not be longwastewater of the mbbr. nitrification of the mbbr didnot recovery for another 5 days( Fig. la). Some adjust- 2.2.2 Sludge additionments of the MBBR operation conditions were done to Biomass in the mBBr was divided into two parts thatrecover the activity of nitrifying bacteria so as to recover were adhered on the carrier and suspended in the bulkliquid, respectively. Nitrification of the MBBR was dueto the co-effect of the adhered and suspended nitrifying2.2.1 Dissolved oxygen(DO) concentrationbacteria, although adhered nitrifying bacteria played aDO is a key factor affecting nitrification. Sudden in- major role. Adding nitrifying sludge into the reactor mightnitrifying bacteria and the balance between nitrifying Nitrifying sludge of 0.4 L(about 6000 mg VSS/L)wasbacteria and heterogeneous bacteria in the biofilm was added into the MBBR at the bottom of reactor. Thebroken. Increasing DO concentration in the bulk liquid nitrifying sludge was cultured with SBR model using thewould enhance oxygen penetration in the deeper layer same influent wastewater as the MBBR used, therefore, theof the biofilm which might recover activity of nitrifying sludge adapted the wastewater well and had good nitrifyingbacteriaability. Performance of the MBBR after adding sludge isNitrification of the MBBr did not recover by increasing shown in Fig. 4.Influent CODo Effluent CODInfluent CODEffluent CODv Influent total phenol v Effluent total phenolv Influent total phenol Effluent total phenols Influent TNH,△ Effluent No2NInfluent TNH,△ Effluent No2NEffluent TNH● Effluent NO3Effluent TNH,o Effluent NO,-N110012501000800g4700D0-3mgL-1500300只中国煤化工CNMHGdoTime(day)Fig 3 Performance of the MBBR after increasing DO concentration inFig 4 Performance of the MBBR after adding sludge.the bullJoumal of Environmental Sciences 2011, 23(4)568-574/ Huiqiang Li et alNitrification of the MBBR was improved after addingn Influent CODD Effluent CODnitrifying sludge and effluent NO2-N concentrationInfluent total phenol o Effluent total phenolreached 15 mg/L at day 53, but decreased gradually andalmost ceased at day 58(Fig. 4). The sludge adding intothe mBBR was cultured in a batch manner which would 900promote nitrifying bacteria growing. That was the reason E soo250why nitrification of the system recovered partly afteradding nitrifying sludge. COD and total phenol removal600were improved little after adding the sludge, the results 2 500indicated that heterogeneous bacteria adhered to the carrierwere enough to effectively degrade most pollutants in 8300wastewater and organic pollutants in the effiuent were200difficult to be biodegraded using aerobic process (Lai etal.,2007)Influent total phenol and TNH3 concentration were inTime(daythe normal range after adding sludge into the MBBr whichndicated that nitrification of the reactor ceased graduallyInfluent TNH,△ Effluent NO2Nwas not caused by the inhibition of NH3-n or phenolo Effluent TNH◆ Effluent NO,NThe nitrifying bacteria were difficult to adhere and growon the biofilm that was already occupied by the activeheterogeneous bacteria. Nitrification recovery would be Sdue to the activity of the suspended nitrifying bacteria.Although the washed sludge was recycled once a day. thenitrifying bacteria would be suppressed in the depositiontank for lacking oxygen. Then, the recycled sludge wouldhave less nitrifying ability than the sludge added into the iMBBR at first. This was the reason why nitrification of =30the mBBr was weaker and weaker with the operation of AMBBR2.2.3 Organic and TNH3 loadL△合。合△△△4A0△A个。◆Influent wastewater of the mbbr was diluted withTime(day)tap water to decrease COD concentration to around 650 Fig. 5 COD and total phenol removal (a)and TNH] removal (b)of themg/LCOD and total phenol concentrations in influent and MBBR after adding more dilute water into the influent.effluent are shown in Fig. 5a and TNH removal of theMBBR is shown in Fig 5b.gain more nourishment(such as inorganic carbon, phosInfluent COD concentration decreased to 650 mg/L andhorus nutrition) from the bulk liquid because of biofilmTNH3 concentration varied between 42.1 and 58.9 mg/L attenuationfrom day 60 to day 72(Fig 5a, b ). Eluent COD concen- At the same time, recovery of the nitrification wouldtration was around 200 mg/L. Nitrification of the mBbr also be due to the decrease of infuent total ammoniarecovered gradually and the nitrification ratio reached 65% concentration. NH3-N concentration and ratio of NH3-at day 72. Then, influent COD concentration increased N/TNH3 during the experiment of nitrification recovery areto 1000 mg/L and effluent COD concentration increased shown in Fig. 6a little to 250 mg/L. Nitrification ratio of the MBBRNH3-N concentration was around 10 mg/L and occupidecreased to 25% at day 74 and recovered to 70% for approximately 15% of TNHy during the period of DOanother 4 days. Effluent NO2-N concentration reached concentration increase and sludge addition Nitrification of55 mg/L at day 89 and nitrification ratio of the mbbr the mBbr was not affected with FA concentration aboveachieved around 90%. NO3-n concentration was belo10 mg/L and ratio of NH3-NTNH3 around 15% before5 mg/L through out the start-up period of the MBBRnitrification inhibition and was not recovered although theEluent COD concentration decreased only 50 mg/L NH3-N concentration decreased to 10 mg/L after nitriwhen influent COD concentration decreased to 650 mg/Lation inhibition(Fig. 2). Effluent TNH3 concentrationThus, available organic pollutants for heterogeneous bacte- decreased a little comparing with influent TNH3 concen-ria in the reactor were decreased which approved indirectly tration because of nitrifying bacteria inhibition and NH3-Nthat the activity of the heterogeneous bacteria was affected concentration in the mBBr was around 10 mg/L whichand the oxygen demanding could be reduced. Although would中国煤化工bacteria seriouslnitrification inhibition of the mBbr was not caused by To acuent of the MBBrbeing short of oxygen(afore mentioned), shortage of wouldCN Gs to reduce NH3-Navailable organic matter would make more heterogeneouscationbacteria shed from biofilm and nitrifying bacteria would recovery. NH3-N concentration decreased gradually andwas below 1 mg/L after 20 days when nitrification ofInhibition and recovery of nitrification in treating real coal gasification wastewater with moving bed biofilm reactorNH-N D NH, -/TNH,This work was supported by the High TechnologyOrganic and TNH, load decreaseResearch and Development Program(863)of China(No2007AA06A411). We are grateful to Min Yuan for hisReferences要Anthonisen A C, Loehr R C, Prakasam T S, Srinath E G,1976. Inhibition of nitrification by ammonia and nitrousacid. Water Pollution Control Federation, 48(5): 835-852.Blackburne R, Yuan Z G, Keller J, 2007. Partial nitrificationto nitrite using low dissolved oxygen concentration as theTime(day)nain selection factor. Biodegradation, 19(2): 303-312.Fig 6 NH3-N concentration and ratio of NH]-N/TNHy during the perod Dyreborg S,, Arvin E, 1995. Inhibition of nitrification by creosote-trification recovery.contaminated water. Water Research, 29(5): 1603-1606Effer S W, Brooks CM. Auer MT, Doerr SM, 1990. Free ammo-the MBBr recovered. Ratio of NH3-N/TNH3 decreased tonia and toxicity criteria in a polluted urban lake. Researcharound 5%. Thus, NH3-n concentration was an importantJournal of the Water Pollution Control Federation, 62(6)control parameter in treating the coal gasification wastew-771-779aterFdz-Polanco F, Villaverde S, Garcia P A, 1994. TemperatureNitrification of the mbbr was affected when influentfect on nitrifying bacteria activity in biofilters activation andCOD concentration increased to 1000 mg/L and recoveredfree ammonia inhibition. Water Science and Technology,0(11):121-130fast which indicated that the nitrifying bacteria were af- Figueroa L A, Silverstein J, 1992. The effect of particulatefected slightly by increasing organic and TNH3 loadingesearch,64(5):728-733Increase in organic load would enhance the activity of the Ganigue R, Lopez H, Balaguer M D. Colprim 3. 2007. Partialeterogeneous bacteria and consume more oxygen whichmmonium oxidation to nitrite of high ammonium contentcould reduce oxygen supply for nitrifying bacteria insideurban landfill leachates. Water Research, 41(5): 3317-3326the biofilm, and increase of TNH3 concentration might Gupta A B. Gupta S K, 2001. Simultaneous carbon and nitrogenbe another factor affecting nitrification. Whereas, shortagemoval from high strength domestic wastewater in anof oxygen supply for nitrifying bacteria was temporaryaerobic RBC biofilm. Water Research, 35(7): 1714-1722.because DO concentration in the bulk liquid was controlled Hill G A, Robinson C W, 1975. 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