Study On Municipal Sewage Treatment By Filler Dosed Enhanced Sedimentation Process

Current situation of some small town was not optimistical in China. For the little population, underdeveloped economic, small treatment scale, abundance of low concentration urban sewage, and difficult to be maintened and managed, thus the treatment process with the feature of low-cost, simple operation and maintenance system, stable and reliable, effective and low energy consumption should be chosen. But the suitable technologies were very limited at present. In recent years, many new enhanced primary treatment process and improved primary treatment process had received wide concern in the field of domestic sewage treatment, because of their high efficiency and low consumption. A new kind of efficient sedimentation tank was developed by adding suspended filler into the traditional sedimentation tank to strengthen the efficiency of pollutant removal and achieve the purposes of efficient pretreatment of wastewater in small town in this study. Through this study, a kind of highly efficient wastewater treatment sedimentation technique would be developed which was suitable for the sewage treatment in small towns, and provide a viable solution for the wastewater treatment problem of small cities.Pollutant removal efficiency of the filler dosed enhanced precipitation process was investigated by the treatment of low and high concentration sewage using this technology, and the influence of different factors on the treatment efficiency was analyzed in this study. Furthermore, the influence of flocculation on pollutant removal efficiency and system operation cycle was investigated by adding coagulant on the basis of filler dosed enhanced precipitation process.The results showed that:(1) After adding fillers in the precipitation device, pollutants removal efficiency of the equipment had significant improvement. Flow velocity could greatly impact SS, TP removal efficiency in filler dosed enhanced precipitation process. With the flow velocity increased and reaction time extended, the pollutant removal rate decreased. And with the increase of flow velocity, operation cycle gradually became shorter. Under the experimental conditions, for the treatment of the low concentration wastewater, optimal operating conditions were:Flow velocity was less than 5.0m/h and operational cycle time was 20 ~ 24h. (2) Polyethylene cylinder filler had more advantages compared with the spherical polypropylene filler in the filler dosed enhanced precipitation process. Flow velocity had significant impact on the operation cycle in two kinds filler dosed enhanced precipitation process. With the flow velocity increased, the operation cycle became shorter and shorter. But the polyethylene cylinder filler had better SS, COD and TP removal efficiency and longer running cycle.(3) Filler dosed enhanced precipitation process could remove SS and COD more efficiently than that by the primary sedimentation tank of the sewage treatment plant.(4) Filler packing height had a significant impact on the removal efficiency of pollutants. The higher the filler layer, the better the pollutants removal efficiency. The height of precipitation layer also had a great influence on the removal efficiency of pollutants and the operating cycle. The higher the sedimentation layer, the better the removal efficiency of pollutants. In addition, increasing of the height of precipitation layer could extend operation cycle effectively. (5) Adding coagulant could increase the pollutant removal efficiency in filler dosed enhanced precipitation process. Coagulant dosage had great influence on removal efficiency of pollutants. When the coagulant dosage was less than 30mg/L, the removal efficiency of pollutants increased along with the dosage increase in the precipitation device; When the coagulant dosage increased over 30mg/L, Coagulant dosage had small effect on the removal rate of pollutants, at this point, SS, COD, TP removal rates were 80%, 67% and 70%, respectively; For the coagulation + filler dosed enhanced precipitation process system continuously operated, adding ferric chloride had better phosphorus removal effect, but the running cycle shortened than that of the simple filler dosed enhanced precipitation process. Adding PAC had better SS, COD, TP removal rate than that by simple filler dosed enhanced precipitation process. Adding PAC had better COD removal efficiency than adding ferric chloride, the removal rate increased by an average of about 5%, and the running cycle had also been extended. In conclusion, PAC was more suitable coagulant for the treatment of municipal wastewater by the coagulation + filler dosed enhanced precipitation process.