| Comparing to traditional nitrification-denitrification process, completelyautotrophic nitrogen removal over nitrite (CANON) process, which is consistent withthe current requirements for energy saving and emission reduction and sustainabledevelopment of wastewater treatment technologies, can decrease O2consuming as muchas60%and hardly consumed COD theoretically. The previous research has beenfocused on influence factors, contributions of nitrogen removal and the capability oftrace hydrazine (N2H4) addtion enhancing for CANON process. Therefore, further studyfor the effect of trace N2H4addtion on characterization of kinetics for ammonium andnitrite oxidation, characteristics of N2O production and functional microbial communityof CANON process were investigated in this thesis. By optimizing the additive N2H4concentration in a CANON system to enhance anammox and inhibite NOB activity inmaximum extent while minimizing the inhibitory influence on AOB activity, and furtherincreasing the denitrification efficiency with N2O production decreasing, whichprovided important data and scientific foundation for engineering application ofCANON. The results in this thesis are given as follows:①The two-step kinetics expression of aerobic ammonium oxidation associatedwith hydroxylamine (NH2OH) was set up; the nitrifying process was dividied intothree-step and kinetic parameters of aerobic ammonium oxidation and nitrite oxidationwere estimated using the respirometry with oxygen uptake rate (OUR); this deepens thecomprehending and understanding of biological nitrification②The kinetics for ammonium oxidation and nitrite oxidation under the inhibitionof hydrazine was competitive and noncompetitive, respectively, the inhibitive effect ofN2H4on nitrite oxidation was stronger than that on ammonia oxidation; the three-stepkinetics model of nitrification inhibited by N2H4was established, and the maximumspecific rate and half-saturation coefficient of N2H4oxidation (7.96±0.811mgN2H4-N/L,0.0916±0.0188mgN2H4-N/mgCOD/h, respectively) with the nitrifying sludge, and theinhibition coefficients of N2H4for hydroxylamine oxidation and nitrite oxidation(7.88±0.783mgN2H4-N/L,1.223±0.555mgN2H4-N/L, respectively) was estimated forthe first time by simulating exogenous OUR profiles of nitrifying reaction with traceN2H4addtion, respectively.③In nitrifying sludge, cloning sequences of ammonia monooxygenase α subunit (amoA) of AOB were mainly related to Nitrosococcu and Nitrosomonas genuses, whilethe rest were clustering in the Nitrosospira genus; cloning sequences of nitriteoxidordeuctase β subunit (nxrB) of NOB were related to Nitrobacter genus, the majoritywere Nitrobacter winogradskyi specie, only a small part was clustering to Nitrobactervulgaris and Nitrobacter hamburgensis; long-time trace N2H4addtion couldsiginificantly restrained the growth of both AOB and NOB.④In CANON sludge, AOB amoA cloning sequences were closely related toNitrosomonas and Nitrosococcus genuses; NOB nxrB cloning sequences were related toNitrobacter genus; the community composition of anaerobic ammonia oxidation(ANAMMOX) bacteria was abundant, and some cloning sequences of hydrazinesynthase α subunit (hzsA) of ANAMMOX bacteria were clustering in CandidatusScalindua genus; long-time trace N2H4addtion partially inhibit the growth of AOB butobviously promote the growth of ANAMMOX bacteria.⑤The enrichment CANON granular sludge in CANON reactor with long-timeN2H4addtion are mainly spherical and ellipsoidal, and there was a more compactstructure and a few tiny microbes gap in outer layer, which made DO could not easilypenetrated the granule surface and caused anoxic/anaerobic region formed; aerobicAOB mainly located at the surface layer of granular sludge; anaerobic ANAMMOXbacteria are mainly located inside the granular sludge.⑥In CANON system with alternant oxygen limited and anaerobic operationmode, pathways of N2O production include NH2OH biological oxidation and nitrifierdenitrification by AOB; under oxygen limited conditions, N2O produced by NH2OHbiological oxidation was more than that by nitrifier denitrification via AOB; underanaerobic conditions, N2O was mainly produced by nitrifier denitrification via AOB.⑦The batch tests with CANON sludge indicated that under oxygen limitedconditions, trace N2H4addition decrease N2O production; under anaerobic conditions,trace N2H4addition accelerate N2O production; in CANON reactor with alternantoxygen limited-anaerobic operation mode, trace N2H4added in oxygen limited stagewas completely degraded to eliminate the possible negative influence of N2H4onanaerobic stage; therefore, in CANON reactor with alternant oxygen limited andanaerobic operation mode, trace N2H4addtion could enhance the denitrificationefficiency while effectively reducing N2O production; in the enhanced CANON processby long-time trace N2H4addition under alternant oxygen limited and anaerobicoperation mode, N2O average production rate lower at0.066±0.047mgN/L/d was only 0.018±0.013%of the total nitrogen removal，which was below the results reported byreferences. |
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