Research on Upgrading and Reconstruction in Low Concentration Urban Sewage Treatment Plants

Abstract

Carrousel oxidation ditch treatment technology with front-facing anaerobic tank is adopted in sewage treatment plant of a southern city in China. Based on A standard of urban sewage treatment plant pollutant discharge standards (GB18918-2002), TN and TP concentrations of the actual effluent are beyond the standard. Analyzing the process flow, inlet and outlet water quality, the main reason of the low removal rate of TN and TP was the lower inflow organic concentration compared to the design value. It’s difficult to form aerobic/anaerobic alternating operation environment as design for nitrogen and phosphorus removal in oxidation ditch. The corresponding reconstruction was carried out. The results showed that stable up-to- standard of effluent quality was achieved by changing vertical surface aerator to microporous aeration, on- demand aeration controlling nitrogen, reducing or closing internal reflux, adding the carbon source, completing the sewage collection system and so on. The average removal rate of tested TN and TP in 2017 can reach 50% and 88% respectively.