A Survey Of Discharge State Of Rural Sewage In Nansihu Lake Drainage Area And Its Treatment Processes Research

A survey of some villages across the country conducted by the Ministry ofConstruction showed that:96%of the villages had no drainage ditches and sewagetreatment system. Sewage was discharged into surrounding water directly, whichresulted in water pollution in rivers, ponds, etc. This was a major hidden danger and abig problem for ecological civilization and social development. Adaptaion to localconditions, according with the characteristics of rural of the technical routes andprocess measures were effective measures to solve the rural water pollution.An on-site investigation was carried out in Xiwan Village, Weishan County,Jining City, Shandong Province, which located in the South-to-North Water DiversionProject（segment of ShanDong） and the southern four lakes water source protectionarea. The quantity and quality of sewage，sewage collection and treatment situationwere involved in the investigation，and the quality of domestic sewage was analyzed,and the appropriate sewage treatment processes were put forward. Combining withthe development of new rural construction planning, technological measures werestudied and put forward to meet the requirements of the future development process.The conclusions are as follows:（1） Through the survey of rural domestic sewage in the southern four lakesregion, the range of the water consumption was20.27to42.9L per day per capitawith an average of31.55L per day per capita. The water consumption for washingdishes and pans, showering, and washing clothes account for the largest portion otfthe total sewage production,76.46%of the total water consumption, and90.64%ofthe total domestic sewage production, and they were the main source of domesticsewage. The average domestic wastewater quantity was25.67L per day per capitawith the range of14.86to35.2L per day per capita, and the pollutants producingcoefficient was0.79. It should be noted that there is mainly dry closet for this village,hence there is no manure enter into domestic wastewater, which is in fact gray water.（2） Although the rural domestic sewage pollutant concentration is low, thevariation range is large. The concentration of COD, NH₃-N, TP and SS were53.7～176.86mg/L,7.32～35.17mg/L,1.62～8.28mg/L,84～237mg/L, respectively. Ruralareas was lack of sewage collection pipelines network, and sewage is collected and transported by open ditches built on the sides off streets, which then flow into waterbodies nearby without any treatment.（3） Ecological approach was used in sewage treatment because of the lowpollutants concentration in sewage. Based on the terrain features of Xiwan Village,eco-ditch system can be constructed with the existing drainage system by engineeringreformation, which include increased the sewage ecological functions such asadsorption, absorption, uptake, degradation, metabolism and disinfection by predatoryand UV radiation of pollutants and pathogenic bacteria and viruses by aquatic plants,micro-organisms and soil media. Surface runoff pooled into eco-ditch by gravity, andinflux region was120,000m2, design velocity0.59m/s.（4） Along with the improvement of rural living standards and new countrysideconstruction, rural residents will have changes in their life style. such as establishedsystematic sewage collection pipe network, the toilet from dry to flushing and thepopularity of shower facilities, etc. These will increase pollutants concentration insewage. Therefore, more effective and efficient domestic wastewater treatmenttechnologies is needed to research and develop, and the submerged biofilm basins-ponds system was put forward.（5） The submerged biofilm basins-ponds system for treating rural domesticsewage from newly built houses with water closets and bathing/shower facilities inthe future was studied by experiment as well, which was not necessary for secondsedimentation tanks and sludge reflux. The results showed that, the average removalrate of COD, NH₃-N, TN and TP were84.33%,97.02%,80.18%and77.34%,respectively; Average concentrations in the effluent were14.88mg/L,1.06mg/L,9.92mg/L and0.53mg/L, respectively. In the effluent of submerged biofilm, thesludge concentration was zero. Consequently, the quality of effluent from stabilizationpond was fine, which can satisfy the tertiary treated wastewater reuse.