Partial Nitrification And Multi-path Nitrogen Removal Process Treating Kitchen Waste Fermentation Wastewater

Focusing on the problems of high-concentration ammonia nitrogen（NH₄⁺-N）and insufficient carbon source of kitchen waste fermentation wastewater（KWFW）,the technology of partial nitrification and denitrification（PND）was developed.With the sequencing batch biofilm reactor（SBBR）as research object,the influences of inoculum,filler type,microbial growth mode,ammonia nitrogen concentration increasing mode and temperature on the construction of PND system with high ammonia nitrogen wastewater were explored,and the method and key control parameters for stably construting systems were also obtained.The microbial population structure and dominant functional species of constructed system were analysed by 16S r RNA high-throughput sequencing technology.Then,the effects of dissolved oxygen（DO）concentration,carbon to nitrogen ratio（C/N）and ammonia nitrogen loading on PND efficiency were also investigated at different temperature,while the action mechanism of free ammonia（FA）and free nitrous acid（FNA）in PND system was clarified,and the optimal operating parameters were obtained.Based on those,the treatment efficiency of the PND system on KWFW under the optimal operating conditions was explored,and the microbial working mechanism of the system was revealed.The main conclusions were as follows:Inoculum,filler type,microbial growth mode,ammonia nitrogen concentration increasing mode and temperature all significantly affected the construction of PND system with high ammonia nitrogen wastewater.The partial nitrification construction process of the system inoculated with dewatered sludge from urban wastewater treatment plant（UWTP）is more stable.And nitrogen removal efficiency of SBBR was higher than that of sequencing batch reactor（SBR）.Compared with the mode of gradually increasing influent ammonia nitrogen concentration,the initial ammonia nitrogen inhibition to nitrite oxidizing bacteria（NOB）was stronger under directly increasing mode,and the accumulation of high-concentration nitrite hindered nitrogen removal.And the nitrogen removal efficiency under 40℃was lower than 30℃,while the effluent nitrite concentration was higher and organic matter was consumed more.The PND efficiency of fiber-combined filler SBBR,which was constructed with UWTP dewatered sludge and gradually increasing mode,was better.Under 30℃,the removal rate of NH₄⁺-N,total nitrogen（TN）and chemical oxygen demand（COD）and nitrite accumulation rate（NAR）of SBBR were 82.7%±0.1%、78.7%±0.4%、86.2%、88.4±0.9%respectively,when they respectively decreased 3.6%、3.4%、2.7%but COD removal rate increased 6.1%under40℃.The SBBR systems constructed with UWTP dewatered sludge under 30℃and 40℃were multi-path coupled systems of partial nitrification,anaerobic ammonium oxidation（Anammox）and denitrification.Ammonia oxidizing bacteria（AOB）in system included Nitrosomonas and Nitrosospira.NOB included Nitrospira and Nitrobacter,and their abundance was low.And NOB community structure tended to succession to Nitrospira at40℃.Meanwhile,the anaerobic ammonia oxidizing bacteria（An AOB）enriched in the system both were Candidatus Brocadia at 30℃and 40℃.The denitrifying bacteria in the system were composed of anoxic and aerobic denitrifying bacteria,Bacillus and Pseudomonas were the main aerobic denitrifiers.Under 30℃and 40℃,DO concentration,C/N and ammonia nitrogen loading all significantly affected the PND efficiency of SBBR system with high ammonia nitrogen wastewater,and Anammox cooperated with the PND process.At 30℃,the PND efficiency was optimal when the DO concentration was 7.0±0.5 mg/L,C/N was 5.2 and ammonia nitrogen loading was 0.25kg N/（m³·d）,and TN removal rate was 85%.Specially,the nitrification path changed from partial nitrification to conventional nitrification once ammonia nitrogen loading decreased to 0.10kg N/（m³·d）due to the weakened FA and FNA inhibition to NOB activity.At 40℃,the PND efficiency was best under DO concentration5.0±0.5mg/L,C/N 5.2 and ammonia nitrogen loading 0.10kg N/（m³·d）,and TN removal rate was 89.9%.And Anammox activity was still detected in the system at 30℃and 40℃when C/N was 5.2,which were 1.53 and 2.10 mg TN/（L·h）,respectively.The higher inhibition to NOB by FA in the early stage and the subsequent inhibition of FNA were the key to realize partial nitrification in high ammonia nitrogen system.Besides,the stronger inhibition to NOB activity under high temperature also was a vital factor for realizing partial nitrification at 40℃.Under above each optimal condition,the peak value of FA inhibition rate(γ_FA)and the final value of FNA inhibition rate(γ_FNA)at30℃were 10.0%and 6.6%,14.2%and 0.3%,0.2%and 5.4%respectively,when those at 40℃were 21.5%and 3.3%,27.6%and 0.2%,7.6%and 6.1%.The FA peak value of40℃system increased and the inhibition was enhanced,which became the inhibition factor except high temperature.However,the Anammox activity of 40℃system was also enhanced.The PND nitrogen removal efficiency of the KWFW treatment systems were high under optimal conditions.And the removal rate of NH₄⁺-N,TN,COD at 30℃were99.7%,94.3%±0.1%,91.6%±0.2%respectively,when 99.5%,96.3%±0.1%,91.7%±0.1%at 40℃.The NAR of above systems were more than 95.5%and 88.0%respectively,indicating their high efficiency of partial nitrification.The results of 16S r RNA high-throughput sequencing revealed that the common AOB and NOB in the system at 30℃and 40℃were Nitrosomonas and Nitrospira respectively.An AOB,Candidatus Brocadia,were detected in both systems.And the denitrifying functional bacteria of 30℃system included Thauera,Burkholderiales＿unclassified,Dechloromonas and Pseudomonas,when Rhodocyclaceae＿unclassified,Thermomonas,Dechloromonas and Pseudomonas in 40℃system,where anoxic and aerobic denitrifier coexisted.