Integrated Treatment Technology for Domestic Sewage in Rural Areas

Abstract

A2/O, as a classic sewage treatment process, has been extensively applied in rural sewage treatment. The A2/O process is superior in efficiently removing organic matters, total nitrogen (TN) and total phosphorus (TP), but defective in its unstable effect of denitrification and phosphorus removal, which is not applicable for the treatment of sewage with low C/N and C/P. The short residence time of denitrification and long residence time of nitrification is the cause of unstable TN in water treated by the A2/O process. Moreover, the nitrate nitrogen of reflux sludge affects the anaerobic environment, leading to a poor effect of biological anaerobic phosphorus release effect (Chen et al. in Environ Protect Eng 37(3):218–219, 234, 2019a; Technol Water Treat 45(5):126–128,134, 2009b). Also, under the influence of living habits, C/N and C/P are low in most rural sewage, which may result in unsatisfactory nitrogen and phosphorus removing efficiency by the A2/O process (Qin et al. in China Sci Technol Inf (5):13, 85–86, 2018). Therefore, the A3/O process is developed to further improve the efficiency of nitrogen and phosphorus removal by adding a pre-denitrification zone before the anaerobic zone. It returns the sludge to the pre-denitrification zone, thus removing nitrates while maintaining a perfect anaerobic environment in the back-end anaerobic zone and overcoming the defects related to the A2/O process.