| Comparing to traditional nitrification-denitrification process, CANON （completelyautotrophic nitrogen removal over nitrite） process, which attracted a lot of attentions,could decrease O2consuming as much as60%and hardly consumed COD theoretically,and was suitable for wastewater treatment of high NH4+concentration and low C/Nratio. CANON sludge was cultivated in SBR in this thesis; and then influence factors,contributions of nitrogen removal and the mechanism of N2H4enhancing CANONprocess were investigated by batch tests; at last, based on ASMs （Activated SludgeModels） and IbM （Individual-based Model）, a1D and2D biofilm model was developedrespectively to describe microbial population dynomics and reactor dynomics ofCANON SBR. The achievements would provide important theoretical basis and guidethe design for full-scale CANON SBR.The results were given as follows:①CANON SBR was successfully started-up in160days under alternativelimited-oxygen/anaerobic operation mode, total nitrogen removal rate and total nitrogenremoval efficiency reached at0.312±0.015kgN/m3/d and71.2±4.3%, respectively.Starting process of CANON should experience3phases in general: nitrification phase,partitial nitritation leading phase and CANON phase. Two different forms of biomasswere found in obtained sludge, one form was floccular（radius＜300μm）, which madeup61%of total volume of sludge; the other was granular（radius≥300μm）, which madeup39%of total volume of sludge. Comparing to continuous limited oxygen operationmode, alternative limited-oxygen/anaerobic operation mode is conducive to the startupand stable operation for CANON SBR. N2H4addition could inhibit the growth of NOB,recover and even enhance the performance of CANON SBR in which healthy NOB（Nitrite-Oxidizing Bacteria） formed.②Orthogonal test method was used to investigate the effects of DO concentration,initial NH4+-N concentration and pH on CANON performance of SBR. The resultsindicated that DO and initial NH4+-N concentrations had significant effects on aerobicammonium oxidation rate while the effect of pH was not significant; DO and initialNH4+-N concentrations had significant effects on nitrite oxidation rate while the effectof pH was not significant; DO, initial NH4+-N concentrations and pH had little effect on anaerobic ammonium oxidation rate. Aerobic ammonium oxidation, as controllingreaction of CANON process, directly determined the system’s total nitrogen removalcapacity, and DO concentration was the key factor. The optimal operating conditions ofthe CANON process were determined as follows: the optimal DO concentration was0.3±0.05mg/L, the optimal initial NH4+-N concentration was150mg/L and the optimalpH was7.4.③The nitrogen removal contribution of CANON process was investigated bybatch experiment. The results showed that AnAOB （Anaerobic Ammonia-OxidizingBacteria） was the dominant contributor to autothrophic nitrogen removal, whereas thecontribution from nitrifier denitrification by AOB （ammonia-oxidizing bactiria） wasless than13.55%of the N removal. With NO2-addition into CANON sludge underoxygen-limitation, the N removal rate was rapidly increased. N2was the main gaseousproduct in CANON process. N2O primarily produced from nitrifier denitrification ofAOB was0.41%-7.25%of the N removal, and there was a positive correlation betweenthe nitrite concentration and N2O production. Under anaerobic conditions,10mMmethanol could not completely inhibit AnAOB activity.④A total nitrogen removal rate of0.198±0.023kgN/m3/d and a total nitrogenremoval efficiency of86.5±5.0%were obtained without NO2addition. With addingtrace NO2into CANON SBR long-term, total nitrogen removal rate and total nitrogenremoval efficiency reached at0.277±0.017kgN/m3/d and67.5±6.2%, respectively.Trace NO2could enhance the performance of CANON SBR and make the operationmore stable.⑤By adding trace N2H4to two CANON SBR long-term, total nitrogen removalrate increased from0.202±0.011kgN/m3/d to0.370±0.016kgN/m3/d, and total nitrogenremoval efficiency increased from65.1±3.75%to77.4±3.8%in SBR1; total nitrogenremoval rate increased from0.200±0.005kgN/m3/d to0.362±0.047kgN/m3/d, and totalnitrogen removal efficiency increased from65.5±1.6%to77.4±7.7%in SBR2. Theratio of NO3--N production to NH4+-N removal was0.058and0.053in two SBR,respectively, which was much lower than the theoretical value （0.11）. The resultsindicated that addition of trace N2H4could enhance the performance of CANON, andreduce the effluent NO3--N concentration significantly. Batch test results showed thatsuitable N2H4concentration was around3.99mg/L in CANON SBR. N2H4could inhibitthe activity of AOB，and AnAOB can utilize N2H4as an electron donor and NO2-as anelectron acceptor to produce N2. N2H4addition can force AnAOB to utilize NH4+as an electron donor and NO3-as an electron acceptor to carry out ANAMMOX in absence ofNO2-. The electrons from the oxidation of additional N2H4by HD （HydrazineDehydrogenase） catalytic, which replace the oxidation of NO2-to NO3-, replenish theconsume by synthesis of AnAOB, therefore N2H4could enhance ANAMMOX andreduce the production of NO3-.⑥Based on ASM1（Activated sludge model No.1）, a1D biofilm model involvedwith autotrophic microorganisms, heterotrophic microorganisms, EPS （extracellularpolymeric substances）, SMP （soluble microbial products） and inert biomass wasdeveloped with AQUASIM to describe microbial population dynomics and reactordynomics of CANON SBR. After sensitivity analysis and calibration for parameters,the simulation results of effluent NH4+-N concentration and NO2--N concentration wasconsistent with the measured value, whereas effluent NO3--N concentration was a littlelower than the measured value, this was due to the presence of a small amount of NOBin CANON sludge. The simulation results showed that when air-aeration load/influentNH4+-N load was about0.18Lair/mgN, the total nitrogen removal efficiency of about90%was obtained. Then the operation conditions was optimized according to thesimulation results, total nitrogen removal rate increased from0.312±0.015kgN/m3/d to0.485±0.013kgN/m3/d, and total nitrogen removal efficiency increased from71.2±4.3%to85.7±1.4%in CANON SBR.⑦Based on ASM1and IbM （Individual based model）, a2D biofilm model wasdeveloped with iDynoMiCS to describe microbial population dynomics and reactordynomics of CANON SBR. The simulation results indicated that biofilm thickness andrelative content of AOB increased with DO concentration, while relative content ofAnAOB decreased when increasing DO concentration. High or low DO concentrationis not conducive to the startup of CANON process. The simulation results of1D and2D biofilm model both indicated that AOB and AnAOB were the dominant bacteria,while NOB and heterotrophic microorganisms were eliminated. AOB mainlydistributed at the outer layer of biofilm while AnAOB at the inner layer. Theconcentration of organics produced in microbial metabolic processes was extremelylow, which leaded to the elimination of heterotrophic microorganisms directly, andNOB was at a disadvantage in competition with AOB for DO and AnAOB for NO2-,which leaded to the elimination of NOB. Biofilm thickness obtained with2D modelwas much lower than that with1D model, and this was related with the method ofbiofilm detachment in two kinds of software. The performance of bioreactor simulated with2D model was lower than that with1D model. |
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