Full-scale Experimental Study On Treatment Of Domestic Wastewater By A~2/O Bio-contact Oxidation Reactor

Recently,sewage discharges in small towns and rural areas have been increasing.This type of pollution is both point source pollution and non-point source pollution,and the pollution sources are scattered and varied.However,sewage treatments in these areas are always ignored,resulting in serious water pollution.Therefore,it is of great significance to develop wastewater treatment technologies suitable for these areas.Based on the economic conditions of small towns in China and the characteristics of sewage,this topic researched and developed a simple,high-efficiency,low-energy new process for nitrogen and phosphorus removal,namely A²/O biological contact oxidation process.By combining traditional A²/O process and biological contact oxidation method,This topic added fillers in anaerobic tank,anoxic tank and aerobic tank respectively to research and develop a new A²/O bio-contact oxidation reactor.This reactor has an activated sludge-biofilm composite biological treatment system with functions of organic matter degradation,nitrogen and phosphorus removal,and removal of SS.The integrated device of A²/O bio-contact oxidation reactor can be used for rural distributed sewage treatment,centralized treatment of township sewage group,urban sewage treatment without pipe network,sewage interception treatment.It has a wide range of uses.In this study,the actual domestic sewage in small towns was treated as the treatment object.The removal efficiency of organic matter,nitrogen and phosphorus in A²/O bio-contact oxidation reactor under different dissolved oxygen,mixed liquor reflux ratio,sludge reflux ratio and sludge age were to determine the optimal operating parameters.At the same time,the kinetic model of the removal of organic matter,nitrogen and phosphorus was derived by the kinetic analysis of the A²/O bio-contact oxidation reactor.The reactor was inoculated with a sludge method.Successfully started-up in 12 days,the reactor had the stable removal ratio more than 75%in COD and 80%in NH₄⁺-N separately.At this time,the water in anaerobic pool and anoxic pool were black and smelly,and the filler was also covered with a black biofilm.Microscopic examination revealed a large area of bacterial micelles,filamentous bacteria,and a small amount of rotifers,vorticella,etc.The aerobic pool filler was covered with a yellow-brown biofilm.A large number of vorticella,rotifers,and filamentous fungi can be seen through microscopic examination.The MLSS measurement of the biofilm on the filler in each pool and the suspended microorganisms showed that the microorganisms in the reactor were mainly based on the biofilm on the filler.The test showed that with daily treatment capacity of 2m³/d,dissolved oxygen of 3.5mg/L,sludge age SRT of 11d,the sludge reflux ratio r of 50%,mixture reflux ratio R of 200%,A²/O bio-contact oxidation reactor had the best contaminant removal.Under the optimal parameters,the average removal rate of COD,NH₄⁺-N,TN and TP can reach 80.21%,89.43%,68.80%,87.93%,and the average effluent concentration was 45.44mg/L,2.52mg/L,8.53mg/L,0.42mg/L,which can stably reach the the grade I Class A standard of Discharge Standard of Pollutants for Municipal Wastewater Treatment Plan?GB18918-2002?.During the operation,the reactor encountered the impact of industrial wastewater.After 3 days,the system basically returned to normal,indicating that the system has good impact load resistance.