Study On Single-stage Anoxic/aerobic Cyclic Activated Sludge Process

At present, the eutrophication problem become more and more serious. What’s worse, the original process has been unable to meet the requirements in urban sewage treatment with low carbon to nitrogen ratio. Designing city sewage treatment plant process must consider the efficiency of utilization of carbon sourse and denitrifying and phosphorus removal. In view of the above problems, Professor Yanqiu Zhang invented the anoxic / aerobic cycle activated sludge process. Even though the waste water Inflow anaerobic tank firstly as the usual A2/O process, the unique large internal reflux ratio not only realized the short range denitrification and phosphorus, but also ensured the lower phosphorus effluent concentration. The treatment effect of the city sewage with low carbon to nitrogen ratio in anoxic/aerobic cyclic activated sludge process has been designed and experimental studied. The results show that:By use of controling single factor test method the influence of internal reflux ratio, C/N ratio of the process operation were both studied. From the comparison of different working conditions, it’s obvious to discovery that when setting the internal reflux ratio as 10, System of each reaction zone of sludge concentration is reasonable, and the concentration of NO2-N in anoxic zone is best, wuich high effect of denitrifying phosphorus removal is achieved. As s result, process is of optimal running effect with organic matter and pollutant distribution equilibrium. On the other hand, in the condition of setting C/N as 3, the supply of carbon source In the sewage to is sufficient whichi can ensure phosphorus release fully in the anaerobic zone. Better effect of denitrifying phosphorus remove with adequate NO2-N in anxoxic Zone would be have accordingly. Under the condition that the internal reflux ratio is 10 and the C/N is 3, the anoxic/aerobic cyclic activated sludge process will reach the best removal efficiencies. The average removal rate of COD, NH3-N,TN and TP were respectively 83.43%, 98.14%, 86.72% and 85.39%. As the influent concentration of COD, NH3-N, TN and TP were respectively 206.64mg/L, 46.25mg/L, 65.76mg/L and 9.38mg/L, and the concentrations of these four targets in the outflow were 34.23mg/L, 0.86mg/L, 8.73mg/L and 1.37mg/L, among which the concentration of COD, NH3-N and TN were better than the standard provided by the first level standard A of the pollutant discharge standards of the urban wastewater treatment plant(GB18918-2002) and the concentration of TP in the outflow also achieve the first level standard B.