New Integrated Self-Refluxing Rotating Biological Contactor for rural sewage treatment

Abstract

Rural sewage pollution has become a serious obstacle to the development of rural areas in China. To overcome this problem, economic, efficient, stable, and low-consumption technologies are urgently needed. To this end, new equipment based on the New Integrated Self-Reflux Rotating Biological Contactor (NISRRBC) was developed for rural sewage treatment in this study. In the development process, the optimal operating parameters were determined to be 5 r/min disk rotation speed, 8 h hydraulic residence time (HRT), 40% submergence diameter of the disks (SDD), and 200% reflux ratio through orthogonal test. Then, two laboratory-scale simulations were conducted with 0% reflux as a control group and 200% reflux as a test group, and the sewage purification efficiency, sludge yield, microorganism, and microenvironment characteristics of the biofilm were investigated. The results indicated that reflux of sludge and nitrification liquid enhanced the NO3−-N concentration and biomass of NISRRBC, thereby improving the pollutant removal efficiency. Compared to 0% reflux, the removal rates of COD, SS, NH4+-N, and TN increased by 5.25 ± 4.18, 5.49 ± 0.64, 5.67 ± 2.68, and 32.63 ± 3.67%, respectively, at 200% reflux. The COD, SS, NH4+-N, and TN concentrations in the effluent were 15.34 ± 7.29, 5.32 ± 2.33, 1.70 ± 2.47, and 12.73 ± 3.94 mg/L, respectively. At 200% reflux, the biofilm formed a favorable gradient for microenvironmental conditions and functional flora, thus facilitating the removal of pollutants in sewage. The operating results of the pilot-scale NISRRBC indicate that the effluent meet the Class B Discharge standard of pollutants for municipal wastewater treatment plants (GB, 18918–2002). Overall, NISRRBC is one of the priority choices for rural sewage treatment owing to its low sludge yield, integrated design concept, and simple operation mode.