Study On Nitrogen And Phosphorus Removal Performance And Microbial Community Of SNADPR Process

In order to solving environmental problems such as water eutrophication caused by excessive emission of nitrogen and phosphorus,it is necessary to further develop innovative wastewater treatment process that is more effective and energy-saving.Simultaneous partial Nitrification,Anammox,and Denitrification?SNAD?process attaches the advantages possessed by autotrophic nitrogen removal process including low aeration energy consumption and zero dosage of external carbon source.Meanwhile,COD and advanced nitrogen removal can be achived through heterotrophic denitrification whthin SNAD process.However,when SNAD is applied in treating municipal sewage characterized by poor ammonia-nitrogen,it is difficult to realize short-cut nitrification continuously and stably,and the excessive nitrate accumulation is easy to occur,which reduces the nitrogen removal efficiency.Besides,the isolated SNAD process is powerless to remove phosphorus from wastewater.Above problems hinder the further application of SNAD process.In this study,by coupling SNAD with denitrifying phosphorus removal?DPR?process in a single-tank integrated fixed-film activated sludge/sequencing batch biofilm reactor?IFAS/SBBR?,a novel integrative Simultaneous partial Nitrification,Anammox,and Denitrifying Phosphorus Removal?SNADPR?process was designed to treat municipal sewage.The residual nitrate after the SNAD process was successfully removed by DPR process,which not only improved the nitrogen removal efficiency,but also reached a satisfactory synchronous phosphorus removal.During the start-up and operation of SNADPR process,the"macro factors including reactor operation performance,nitrogen removal activity of microorganism,and the‘micro factors'like proportions of pecific functional genera,spatial and temporal characteristics of the microbial community structures,were both analyzed.The conclusions in this study are as follows.?1?First of all,denitrifying polyphosphate-accumulating organisms?DPAOs?were successfully domesticated in a sequencing batch reactor.The SNAD process was initiated in a IFAS/SBBR reactor at the same time.When the SNAD process was applied in treating simulated domestic sewage?NH₄⁺-N=50 mg/L?under the optimized conditions?C/N=1.4,DO=0.35 mg/L?,the concentrations of effluent NO₃^--N was 10.12±2.25 mg/L,and TN removal efficiency was 78.13±4.68%.?2?Subsequently,parameters of C/N ratio and DO were investigated and optimized after start-up of the SNADPR process.Under the optimized condition?C/N=4.0,DO=0.45 mg/L?in SNADPR process,the final effluent concentrations of TN,PO₄^3--P,and COD were 5.51±1.07mg/L,0.35±0.03 mg/L,and below 4 mg/L,respectively,with the corresponding removal efficiencies of 89.15±2.19%,92.93±0.60%and over 96.00±0.06%,respectively.It suggested that the SNADPR process achieved an obviously better nitrogen removal performance than that of the SNAD process.?3?Furthermore,in terms of time,the application of IFAS/SBBR operation mode has created different conditions to match different reactions,including COD removal reaction in the anaerobic period,nitrogen removal and P-uptake in the intermittent aeration period processes.Meanwhile,in terms of space,the application of IFAS/SBBR operation mode has constructed two different habitats including biofilm-attached carriers and suspended floc for the better survival of various functional bacteria in SNADPR system.And the distinctive microbial community distribution in spatial was harvested,where AnAOB?Candidatus_Kuenenia and Candidatus_Brocadia?were mainly located in biofilm,whereas DPAOs?Dechloromonas and Pseudomonas?and AOB?Nitrosomonas?basically lived in suspended floc.The separation of sludge retention time between AnAOB and DPAOs was realized in a single-tank reactor by conserving biofilm-attached carriers while termly discharging phosphorus-rich floc,which effectively guaranteed the successful operation of SNADPR process.