Theoretical Study And Practice Of Geological Body Biological Aerated Filter For Domestic Sewage Treatment

Water pollution is very serious in our country,Especially the river basin generally contaminated and appeared development trend.Not up to standard of rural domestic sewage discharge is one of the main influence factors.There are a lot of processing technology for rural domestic sewage.Considering the conditions of the rural economy and domestic sewage.Need to use the processing system with miniaturization,low construction cost,low operating cost,management and maintenance convenience,treatment effect and ecological landscape with good effect.In this study,using aeration biological filter method as the core of treatment system to treatment the rural domestic sewage.The aeration biological filter using geological body as the filler material.By using the combination of natural gravel,limestone and river sand to study the feasibility of the geological body as aeration biological filter packing.Through the indoor experiment,the structure and size of the filter,the aeration mode,the selection and arrangement of the filter,the water distribution mode and the control of the inlet and outlet water were analyzed and studied.The biological aerated filter was set up,and the hydraulic parameters of the filter were determined.Study on biofilm formation of biological aerated filter,after the biofilm was successfully applied,the influence of filter thickness,aeration time and residence time on the treatment of wastewater was studied by single factor analysis.By orthogonal experiment,the optimal conditions of the three factors were analyzed,and the regression equation of each index was established.Finally,through the continuous monitoring of biological aerated filter in different seasons,the removal rate of each index and the optimal operating temperature of biological aerated filter were obtained.Through the above methods,the experimental results and conclusions are as follows:?1?This experiment uses the blower to carry on the aeration to the filter.When the aeration tube diameter is DN25,The distance between the two tubes is 200mm,the pore size of the vent hole is 10mm,the pore space is 100mm and the small hole is provided with an anti clogging cover layer;The filter is filled with gravel-limestone-river sand-limestone-river sand-limestone,and the water pipe and the back flushing pipeline are embedded in the filter,so the water can be layered and distributed according to the need;The permeability coefficient of the filler matrix was 130.60?214.23m/d,and the porosity of the filter was 19.98%.?2?This experiment uses the natural hanging film condition method,and hanging film initial success after 30 days.From the beginning of the hanging film to the initial success of hanging film.The removal rate of COD from the initial 13.26%to the final stability in the vicinity of 65%,and the highest removal rate of up to 66.73%;The removal rate of TN increased from 8.78%to 38.29%;The removal rate of NH₄⁺-N increased from 28.19%to 73.81%;The removal rate of TP was minimum affected by biofilm,from the first day of the hanging film,the removal rate of TP reached 57.78%,and the removal rate was stable at about 72.96%,the maximum removal rate was 84.67%.The turbidity increased slightly from the beginning of the hanging film,from the sixth day the filter is used to remove suspended solids in the wastewater,and the turbidity of the filter outlet begins to decline,the average turbidity reduction rate was 49.47%at initial success of hanging film,and the highest reduction rate was 76.35%.?3?Under the condition of different filter layer thickness,there was no significant difference in the removal efficiency of COD,TN,NH₄⁺-N.With the increase of filter thickness,the removal rate of COD and NH4-N was increased,and the removal rate of TN was less influence;there was significant difference in the removal efficiency of TP in different filter layer thickness,The filter has a great influence on the removal rate of TP under different thickness,the greater the filter thickness,the better the removal effect of TP.?4?Under the condition of different aeration time,there was significant difference in the removal efficiency of COD,TN,NH₄⁺-N.The removal rate of COD and NH₄⁺-N increased with the increase of aeration time and the removal rate of TN increased with the increase of aeration time;There was no significant difference in the removal efficiency of TP in different aeration time,Different aeration time had little effect on the removal rate of TP.?5?Under the condition of different residence time,there was significant difference in the removal efficiency of COD,TN,NH₄⁺-N,TP.The removal rate of COD,TN,NH₄⁺-N,TP increased with the increase of residence time.?6?Through orthogonal test,at temperature was 21.8?25.5 ?,pH was 7.0?8.5 and flow rate was 3?5m3/d,When the filter thickness was 1.55m,aeration time was 30min/3h,and the residence time was 1.08?1.79d,the biological aerated filter had the best effect on domestic sewage treatment.?7?Under the optimal operating conditions,the linear regression and log regression equations of each index are established.The regression equation of COD in the influent concentration of 47.19?83.93 mg/L was C_No=0.3395C_Ni-1.7197 and C_No=21.311n(C_Ni)-68.627;The regression equation of TN in the influent concentration of 18.41?31.10 mg/L was C_No=0.4131C_Ni+1.7969 and C_No=9.98851n(C_Ni)-19.932;The regression equation of NH₄⁺-N in the influent concentration of 7.99?14.29 mg/L was C_No=0.2269C_Ni+0.1932 and C_No=2.44091n(C_Ni)-3.1251;The regression equation of TP in the influent concentration of 0.89?2.35 mg/L was C_No=0.2201C_Ni+0.0428 and C_No=0.334711n(C_Ni)+0.2522.?8?The removal efficiency of biological aerated filter was significantly affected by water temperature.When the water temperature is 20?25 ?,COD removal rate reached 68.73%,TN removal rate reached 51.54%,NH₄⁺-N removal rate reached 75.42%and TP removal rate reached 75.24%.When the temperature drops to 10? and below,the removal rate of each index was very low,COD removal rate was 32.70%,TN removal rate was 13.38%,NH₄⁺-N removal rate was 25.24%and TP removal rate was 52.6%.It is concluded that the optimal operating temperature of biological aerated filter was 15?25 ?.?9?Geological body filler has many characteristics,such as low price,easy to obtain,by demonstrating experiment,Use geological body as aeration biological filler material is practicable and it has significant advantages to remove the TP.