Operating Characteristics Of Partial Nitrification And Denitrifing Phosphorus Removal System Treating Municipal Wastewater And Nitrate-contained Sewage

Nitrogen and phosphorus removal from sewage is a hot topic in recent years.Because of the low C/N Ratio and the shortage of carbon source,it is difficult to meet the discharge standard by using traditional biological nitrogen and phosphorus removal process.Nitrate wastewater from fertilizer,explosive and other industries also needs to be treated urgently.Therefore,it is necessary to find a biological nitrogen and phosphorus removal process for simultaneous treatment of low C/N municipal wastewater and nitrate wastewater.In this study,the start-up and treatment characteristics of DPR-SNED system,DPR-SPNED system and EPDPR system for low C/N municipal wastewater and nitrate wastewater were investigated.The start-up and operation of simultaneous nitrification and denitrification?DPR-SNED?system were investigated.The results showed that the simultaneous nitrification and denitrifying phosphorus removal?SNEDPR?system could be started on 60 days when the anaerobic/anoxic operation mode was adopted with 3 h's anaerobic duration and 0.5-1.0 mg/L DO concentration.It can be seen that the concentration of PO₄^3--P in effluent was below 0.5 mg/L and the removal rates of nitrogen and phosphorus,COD,SNED and COD_insns were maintained above 90%,80%,70%and 95%respectively.Then the operation mode was changed and nitrate-contained sewage was added at the beginning of anoxic stage.DPR-SNED system was achieved with the effluent PO₄^3--P concentration<0.5 mg/L,nutrient and COD removal efficiencies above 88%and 90%,respectively,and SNED efficiency and COD_ins efficiency maintained at 62%and 90%,respectively.The system has good ability of denitrifying phosphorus removal and endogenous denitrification,which provides a sludge source for subsequent start-up of EPDPR system,and it can treat low C/N municipal wastewater and nitrate wastewater independently.Subsequently,the effect of different electron acceptors?NO₂^--N and NO₃^--N?on denitrifying phosphorus removal was studied.The results showed that DPR-SNED system had strong ability of denitrifying phosphorus removal,and denitrifying phosphorus removal bacteria could use nitrite as electron acceptor for denitrifying phosphorus removal.The denitrifying phosphorus removal rate decreased with the increase of NO₂^--N concentration.When the concentration of NO₂^--N was 10 mg/L,the phosphorus removal rate was the highest,which showed that high concentration of NO₂^--N could inhibit the denitrifying phosphorus removal to some extent.In DPR-SNED system,the ability of denitrifying phosphorus removal by NO₃^--N is strong.When the DPR-SNED system used NO₃^--N as an electron acceptor at low concentrations for denitrifying phosphorus removal,the denitrifying phosphorus removal rate increased with the increased of NO₃^--N concentration.When NO₃^--N concentration is10mg/L,the phosphorus removal rate reaches the highest,and then decreases.When the concentration of NO₃^--N is low,DPAOs has more advantages than DGAOs,so there is almost no accumulation of NO₂^--N at low concentration.When the concentration of NO₃^--N is high,DGAOs can use NO₃^--N as electron acceptor to carry out endogenous partial denitrification and realize the accumulation of NO₂^--N,which provides a basis for the startup of EPDPR system.Then the start-up and operation of the denitrifying phosphorus removal coupled simultaneous partial nitrification endogenous denitrification?DPR-SPNED?system were studied.The results show that the start-up of DPR-SNED system can be realized by adjusting the aeration rate and aeration time in aerobic section on the basis of DPR-SNED system.Partial nitrification can be realized in aerobic section system.The total nitrogen removal rate of the system was above 90%.More than 95%of PO₄^3--P and 100%of NO₃^--N can be removed by enhanced denitrifying phosphorus removal in anoxic stage.Based on the molecular biological analysis of the original sludge and the sludge from the DPR-SPNED system,it can be concluded that the anaerobic/anoxic/aerobic operation mode and the low DO concentration can effectively inhibit NOB and realize partial nitrification.The ratio of AOB?about 4.5%?to NOB?about 1.4%?is the key to realize partial nitrification.Bacteria belonging to GAOs?about 5.5%?were favorable for the realization of SNED,while PAOs?about 7.5%?was dominant for the realization of denitrifying phosphorus removal.Compared with DPR-SNED system,the optimized DPR-SPNED system has lower aeration time and quantity,but the total nitrogen removal rate remains at a higher level,which saves energy and improves the reaction efficiency.Finally,the start-up and optimal operation of the endogenous partial denitrifying phosphorus removal?EPDPR?system were investigated.The results showed that the system was operated in anaerobic/anoxic mode,and the start-up of EPDPR system could be realized in 100 days by adjusting the influent mode?end-anaerobic drainage?,increasing the influent NO₃^--N concentration and prolonging the anoxic running time.The concentration of PO₄^3--P in the effluent is less than 0.5 mg/L,and the system has good denitrifying phosphorus removal capacity.The removal rate of COD was maintained at a high level?90%?.NO₃^--N in the effluent is less than 0.5 mg/L,and the nitrite accumulation rate is 65%.The effluent NH₄⁺-N:NO₂^--N is about 1:1 and can be connected to Anammox.