Treatment Of Rural Sewage By Using Combined Processes Multi-layered Biological Filter And Constructed Wetland

Along with further development of new socialist countryside, both village infrastructure and environment has gone through great changes. However, problem of inappropriate rural sewage treatment is also becoming serious. Because of the intermittent discharge of rural sewage , the water quality and volume inside is not stable and the COD density is comparatively high. Additionally, rural sewage contains plenty of people and animal excreta, including high volumes of TN and TP especially. Facing these problem, SJTU developed a combined process of biological filter and constructed wetland to deal with rural life sewage. Depending on two important scientific research projects of Shanghai Science and Technology Committee, this research was carried out for two years, regarding adsorbed NP volume of packing, operational effects of small-scale combined stratification biological filter and the demonstration project.This project make research on the adsorb volume of sintered aggregate, volcanic rock and gas brick under static conditions. Results show that the equilibration time of static adsorption is about 4 hours and the absorb volume of gas brick is 5.59mg/g. By comparing sewage discharge effects of combined stratification biofilter and single packing biofilter, we find that biofilters with sintered aggregate, volcanic rock as the packing could reach over 80% COD removal efficiency, 55% to NH4+-N, but only 20% to TP. Biofilter filled with gas brick could reach sound TP removal effect to over 70%. However, its removal effects to COD and NH4+-N, are quite low. The combined stratification biofilter has great discharge efficiency to all kinds of pollutant and its removal rate to COD, NH4+-N, TN and TP could reach 79.35%,54.22%,45.79% and 47.18% respectively. Conclusion made from the two years examination on Caojiabang demonstration project shows that: with a water flow rate of 60m3/d, the combined process could meet various pollutant standard in water when treating rural sewage water in Caojiabang. Among all the pollutants, COD, NH4+-N, TN and TP have an effluent concentrationof 62.4mg/L,8.2mg/L,12.6mg/L and 0.94mg/L with a removal efficiency of 80%,50%,50% and 70% respectively., meeting the standard of GB 18919-2002.The combined sewage treatment technology enjoys low operational fee that less than 0.15 Yuan per ton. With traits of good pollutant removal efficiency, strong adaptation and little system residue, this combined process is easy for management and regular protection. Because of its low requirement on operator, the combined process is suitable to be promoted and applied in countryside.