Performance of Biological-Ecological Process for Rural Domestic Sewage Treatment in Taihu Lake Region

Rural domestic sewage is one of the main pollution sources of Taihu Lake. To seek suitable sewage treatment technology, investigation and pilot research was conducted in rural places in Taihu Lake region. Field investigation was done by questionnaire and sewage sampling analysis. Demonstration project was built with a biological-ecological process consisting of anaerobic hydrolysis, waterfall aeration contact oxidation and constructed wetland in a village named Linzhuang. The influent and effluent samples of this system were monitored for 6 months. Field investigation data showed sewage indexes in rural villages fluctuated greatly. Operation results of the pilot system indicated this combined process was efficient in pollutants removal. Chemical oxygen demand (COD), total phosphorus (TP) and total nitrogen (TN) in the effluent from this process was stably below 50 mg/l, 0.5 mg/l and 12.9 mg/l respectively. COD was mainly removed by anaerobic hydrolysis and contact oxidation, while nitrogen was mostly distripped by nitrification in contact oxidation unit and denitrification in hydrolysis unit. Most of TP removal was accomplished in the constructed wetland by filter interception, plant adsorption and microbial transformation. Owing to mutually complementary interaction between biological and ecological methods, the performance of this system was not obviously affected by influent and temperature fluctuation. This system was efficient in pollutants removal and cost effective in building and operating.