Study On The Efficiency Of ABR-MBR Process Treating Domestic Wastewater Based On Short-cut Denitrifying Phosphorus Removal

Anaerobic baffled reactor?ABR?is mainly used in the treatment of high concentration wastewater,but studies have shown that ABR reactor combined with other reactors to treat low concentration domestic sewage can also achieve better treatment results.The ABR reactor can not only realize the effective separation of microbial phase,but also the transformation of substrate at different stages and different levels,and provide high-quality carbon sources,such as VFAs,for subsequent phosphorus removal.With its high effective biological interception and the advantage of SRT and HRT separating completely,and with decrease of membrane producing and operating cost,membrane bioreactor?MBR?is increasingly widely applied in recent years.The main studying contents and conclusions of this study are as follows:1.The operational control conditions of realizing short-cut nitrification in MBR was investigated in a lab-scale combined ABR-MBRprocess,which laid the foundation for further research on the performance of denitrifying phosphorus removal of the system.The experimental results showed that short-cut nitrification in MBR was achieved by controlling low Dissolved Oxygen?DO?concentration of0.3⁰.7mg/L and HRT of MBR was 3h under the condition that HRT of ABR was 6h,sludge reflux ratio was 100%,NO_x^--N reflux ratio was 300%and temperature was30±2?and nitrite accumulation rate reached above 60%.The analysis of the influencing factors of short-cut nitrification showed that maintaining low DO concentration and gradually shortening HRT were the key factors,and pH,free ammonia?FA?,free nitrous acid?FNA?,temperature and sludge retention time?SRT?had a slightly positive effect on short-cut nitrification.In the period of short-cut nitrification,the stable and high efficiency of the removal of COD and NH₄⁺-N were achieved and the average concentration of the effluent of COD and NH₄⁺-N whose removal rates were above 90%were below 50mg·L^-1 and 2mg·L^-1,respectively,and the removal efficiency of total nitrogen?TN?reached 72%.2.In the experiment,volume loading rate?VLR?of ABR was set at 0.76,1.01,1.51and 2.27kg·?m³·d?^-1,respectively.The performance of removal of carbon,nitrogen and phosphorus in the system and the effect of VLR of MBR on nitrification performance were observed at each VLR of ABR.The results showed that under the condition that VLR of ABR was 1.51kg·?m³·d?^-1,the amount of CDO removal in A2chamber was the largest and the short-cut nitrification was achieved in MBR when VLR of MBR was 1.51kg·?m³·d?^-1.Meanwhile,the removal efficiency of NH₄⁺-N and TN reached more than 90%and 72%,respectively,anaerobic P-release and anoxic P-uptake were 7.41mg·L^-1and 15.42mg·L^-1,respectively,and the concentration of PO₄^3--P in effluent was lower than 0.5mg/L,which indicated that the short-cut nitrification was more conducive to strengthening the performance of denitrifying phosphorus removal in ABR-MBR system.3.The influence of NO_x^--N recycling ratio on nitrogen and phosphorus removal was investigated at NO_x^--N recycling ratio of 100%,200%,300%and 400%,respectively.The results under different conditions showed that the efficiency of denitrifying phosphorus removal in ABR was found to increase with increasing NO_x^--N recycling ratio from 100%to 300%but decrease when NO_x^--N recycling ratio was 400%.Short-cut nitrification was achieved by controlling low Dissolved Oxygen?DO?concentration ranges from 0.3 to 1.0 mg?L^-1 and short HRT of 3h in MBR reactor and nitrite accumulation ratio reached above 60%while NO_x^--N recycling ratio was 300%.Meanwhile,short-cut denitrifying phosphorus removal?NO₂^--N mainly acted as electron acceptor of denitrifying phosphorus removal?was achieved and played the dominant role in phosphorus removal.