Purification effect of non-dynamic cascading bio-filter on domestic sewage in a mountainous village

The present study investigated the performances of a set of non-power cascade bio-filter system constructed based on the low mountains and hills terrain on rural sewage. A continuous one-year monitoring of the performances of this system had been carried out in the typical rural village in low mountainous areas of the Sichuan Basin. The results showed that the average concentrations of chemical oxygen demand (COD), total nitrogen (TN), ammonium nitrogen (NH4+-N) and total phosphorus (TP) in the rural domestic sewage were 147.33, 32.52, 14.39 and 3.03mg/L, respectively. The average removal efficiencies of COD, TN and TP in the cascading bio-filter were 59.6%, 60.8% and 67.4%, with the multi-stage bio-filter units being 39.1%, 44.1% and 54.1%, respectively. The seasonal reduction rates of TN and TP were in the order of summer (autumn) > spring > winter. Influent concentrations, air temperature, plant biomass and hydraulic loading (HL) were regulators of the purification efficiency. Thus, the low-temperature-resistant plants and rain-sewage separation in the later stage to optimize purifying efficiency and improve the general applicability were recommended to improve domestic sewage purification to protect water environment in mountainous villages of the upper reaches of the Yangtze River. © 2021, Editorial Board of China Environmental Science. All right reserved.