Optimization Study On The Key Parameters Of Small Town Domestic Sewage Treatment By Strengthened Constructed Rapid Infiltration System

Because of unbalanced economic development, many small towns have almost no construction and planning of the sewage treatment facilities.Then large amount of sewage is discharged directly without treatment, causing serious pollution of the receiving water.Based on the investigation of the present situation of the small town sewage, we should select the suitable sewage treatment technology to ensure the harmonious development of the social economy and the ecological environment of the small town.Constructed Rapid Infiltration system,which has the characteristics of high water quality, low energy consumption, simple equipment, convenient management and maintenance, and low investment, is especially suitable for small town sewage treatment.In view of the low removal rate of TN, TPand asy to plug and so on,by the improvement of the former, the strengthenedconstructued rapid infiltration system(SCRI) is proposed.Experimental results show that the effluent concentration of SCRI can reach the level A standard of "urban sewage treatment plant pollutant discharge standard".In this study, the key parameters of SCRI were optimized. Through the analysis of the removal efficiency and removal mechanism of COD, ammonia nitrogen, total nitrogen and total phosphorus, the key parameters of the system were determined. And provide the basis for the application of SCRI in small town domestic sewage treatment.Through the experimental study on the optimal structure parameters for small town sewage treatment using the SCRI system, we found that with the increase of the height of the non saturated water layer and saturated water layer, the removal rate of COD, ammonia nitrogen, total nitrogen and total phosphorus were all increased.The removeof COD and ammonia nitrogen were mainly in the non saturated water layer, and the remove of total nitrogen and total phosphorus were mainly in the saturated water layer.According to the constructed rapid infiltration column height microbial proportion changes, combined with the different height of the dissolved oxygen content and the pollutants removal effect, the optimal unsaturated water layer height 70 cm and the optimal saturated layer height is 60 cm when processing sewage of small towns by SCRI.The optimal operation parameters for small town sewage treatment using the SCRI experimental results show that, with the increase of the ratio of wet to dry, the removal of COD, ammonia nitrogen and total nitrogen first increased and then decreased, the optimal ratio of wet and dry 1:5. The removal rate of COD, ammonia nitrogen and total nitrogen decreased with the increase of the hydraulic load cycle, and the optimal hydraulic load cycle was 6h. With the gradual increase of hydraulic load, the removal rate of COD, ammonia nitrogen and total nitrogen decreased gradually, and the optimal hydraulic load was 1.5m3/(m2·d).The removal efficiency of TP was almost not affected by the operating parameters.Under the optimal conditions of key parameters, theaverage removal rate of COD, NH3-N, TN and TP were 91.15%, 87.65%, 74.33% and 98.68% respectively, the mean effluent concentrations were respectively for 3.84mg/l, 27.58mg/l, 9.34mg/l, 0.06mg/l, meet the "urban sewage treatment plant pollutant discharge standard" level of a standard.