Operation Parameter Optimization Of Combined Process Of A/O-constructed Wetland And Screening Of Plants For The Treatment Of Rural Waste Water

With the development of the rural economy and enterprises, the pollution of the rural water environment is becoming more and more serious. The main reason about the pollution problem is that domestic sewage, industrial wastewater and waste water containing pesticide and fertilizer are directly discharged without treatment. Accordingly, we should take steps to boost rural water infrastructure construction and pay more attention to the treatment of rural domestic sewage and emission. However, rural domestic sewage is characterized with wide distribution, decentralization and wide source. It is, thus, difficult to adopt large-scale pipe network and sewage disposal system to collect and treat.To solve the problems in the treatment of rural waste water, the treatment of A/O-constructed wetland was employed and the influences of operation parameters and plants grown on constructed wetland on the removal rate of pollutant were investigated. The main results showed as follows:(1) When the circumfluence ratio was 2 or 3, both COD and NH3-N in the effluent could reach emission standard. Considering the aspect of power consumption and dissolved oxygen concentrations on denitrification stage,2 was the appropriate circumfluence ratio for the system.(2) In the A/O treatment, the removal rate of COD and NH3-N increased with the increase in dissolved oxygen concentration, but when dissolved oxygen increased to a certain extent, the organic substrate became the limiting factor, and dissolved oxygen concentration had limited impact on the removal rate of COD and NH3-N. Under inlet conditions, in order to avoid the increase of operating costs, the proper dissolved oxygen concentration was 2-3mg/L, and the effluent could reach emission standard.(3) The removal rate of constructed wetland which had been grown plants was significantly higher than that of the control. With the exception of total phosphorus, the highest season’s removal rate of the other three pollutants was reed> canna> windmill grass, but the average removal rate was on the contrary, i.e., windmill grass> reed> canna. Therefore, the windmill grass was more suitable as constructed wetland plants in the three plants selected.