Study On The Novel SNAD-based Technology For Simultaneous Removal Of Nitrogen And Phosphorus From Municipal Sewage

With the further research in water treatment microbiology and the progress of various scientific research techniques in recent years,the biological nitrogen and phosphorus removals process has gradually changed from a simple superposition of several basic principles to a coupled process.Simultaneous partial nitrification/anaerobic ammonia oxidation/denitrification（SNAD）process has gradually become a research hotspot of wastewater nitrogen removal field,because of its advantages of energy saving,environmental protection and no need for additional carbon sources.However,when treating municipal sewage,a small amount of nitrate was accumulated in the final effluent.At the same time,the SNAD process can not remove phosphorus.Therefore,this study chose to couple denitrifying polyphosphate-accumulating organisms（DPAOs）or algae to form a simultaneous nitrification/anaerobic ammonia oxidation/denitrifying phosphorus（SNADP）removal process or a simultaneous nitrification/anaerobic ammonia oxidation/denitrification/algae（ASNAD）process for simultaneous nitrogen and phosphorus removal.This article focused on the optimization of the conditions during the startup of the two processes,and the actual treatment effect combined with the anaerobic hydrolysis（ANHA）process.At the same time,the activity and community structure changes of related functional bacteria in the system were analyzed,aiming to provide technical guidance for the practical application of the two processes in municipal wastewater.The conclusions of this study are summarized as follows.（1）The ANHA-SNADP combined process was constructed to treat municipal wastewater.When C/N was 3.0 and DO was 0.15 mg/L,the SNADP process started successfully.The concentrations of effluent total nitrogen（TN）,total phosphorus（TP）and chemical oxygen demand（COD）were 2.69,1.00,and 4.10 mg/L,respectively.In order to ensure that the SNADP process is in the best condition,the previous ANHA process was selected to be run at HRT for 5 h.At this time,the effluent COD concentration was 135 mg/L,and the VFAs/COD ratio was 0.504（VFAs were mainly acetic acid）.The final effluent TN,TP and COD concentrations of actual municipal wastewater were 4.17,0.64,and 12.07 mg/L,respectively,so the treatment effect of various pollutants was good.The main bacterial groups in the ANHA process were Lactococcus and Trichococcus.In the SNADP process,An AOB mainly existed in filler to form biofilm,and the rest mainly existed in suspended sludge.（2）The ANHA-ASNAD combined process was also constructed to treat municipal wastewater.Various conditions in the ASNAD process were optimized by batch experiments using response surface methodology.The best experimental conditions were as follows:the influent carbon to nitrogen ratio was 2.7,the algae to bacteria ratio was 20（V/V）,and the light to dark ratio was 2.5.Under the best experimental conditions,the effluent concentrations of ammonia（NH₄⁺-N）,TN,TP and COD were 2.01,3.74,0.21 and 14.28 mg/L,respectively.When treating actual municipal wastewater and the ANHA process with a HRT of 5 h,the final stable effluent concentrations of NH₄⁺-N,TN,TP and COD were 0.56,2.04,0.28 and15.08 mg/L,respectively.Compared with no introduction of algae,there was no significant difference of the proportion of related functional bacteria in the process system.