Garden slow percolation system for processing rural distributed wastewater

According to the problems of non-point source pollutions resulted from decentralized rural domestic wastewater in China, on the basis of self-purification capability of soil, garden land infiltration system was constructed in a garden land at Caohuang village of Xinghua city in Jiangsu province, which combined the techniques of traditional slow rate land treatment system and the Australian land filter system. Hydraulic loading rates were calculated based on the growth characteristics of camphor tree (Cinnamomum camphora), meteorological conditions and land capacity of the site. Water distribution and drainage system were also optimized in the present study for improving treatment capability. The garden land infiltration system had run for six months since June, 2010. The results showed that the average removal rates of total nitrogen (TN), total phosphorus (TP), chemical oxygen demand (COD), total organic carbon (TOC) and ammonium nitrogen (NH4+-N) were 80.7%, 89.2%, 89.5%, 60.2% and 85.7%, respectively. The concentration of pollutants in the outflow met the requirements of the first standard (A level) of National Discharge Standard of Pollutants for Municipal Wastewater Treatment Plant (GB18918-2002). No significant difference was found after the experiments between the groundwater qualities in the experiment plot and the control plot. The treatment efficiency of this garden land system has preferably reached the design requirements. According to the calculation, the construction cost of the system was only 36 000 Yuan with the treatment capacity of 14.7 m3/d, which was much lower than other wastewater treatment techniques. The garden land infiltration system has the advantages of technique-feasible, cost-effective and maintenance-convenient, and can also provide a viable alternative for decentralized wastewater treatment in rural areas of China.