Study On The Treatment Of Urban Domestic Sewage By Sequencing Batch Mud-Film Composite Biological Pool

In this paper,we adopts the sequencing batch mud-film composite biological pool process to conduct experimental research on urban domestic sewage treatment for the first time.The process is run in series by the first-stage anoxic biological pool and the second-stage mud-film composite biological pool,using floating biological filler and passing Cycle cycle mode operation.This experiment explores the optimization of its operation mode and parameters,studies the treatment effect on domestic sewage,and provides reliable operating parameters and basis for engineering applications.It is determined that the cycle of the municipal wastewater treated by the sequencing batch mud-film composite biological pool during the start of the membrane is 1.5h,wherein the aeration and influent time is 45min,the standing time is 15min,and the water discharge time is 30min.The membrane start-up was carried out according to the method of gradually increasing the water-filling ratio.The water-filling ratio was 0.05 on the 5th day before the start,and then the water-filling ratio was increased by 0.05 every 5 days.After 20 days of membrane culture,the effluent COD_Crr and NH₄⁺-N were removed.The rate is stable at 85%and above 90%.The cycle time of the sequencing batch mud-film composite biological pool was further optimized.On the basis of the membrane start cycle time,the removal rate of COD_Crr and NH₄⁺-N decreased while reducing the aeration time;reducing the water intake time would result in a decrease in the removal rate of TN and TP.Decreased rest time leads to an increase in effluent COD_Crr and SS,and a decrease in effluent time leads to unstable COD_Crr and SS removal.Therefore,it is determined that each cycle lasts for 90 minutes,the aeration and water inflow time is 45 minutes,the standing time is 15 minutes,and the water discharge time is 30 minutes.At this time,the optimal effluent quality is obtained while ensuring the treated water volume.The aeration amount,mixed liquor return flow rate and sludge return flow of the second-stage mud-film composite pool were tested.The removal efficiency of various pollutants increased firstly with the increase of aeration volume,and the aeration amount was25m³/h,the system has the best removal ability.At this time,the removal rates of COD_Crr and NH₄⁺-N are 90.03%and 95.53%,respectively;TN and COD_Crr are most affected by the reflux of the mixture,and the flow rate of the mixture is 10m³/h.The pollutants have the best removal effect.At this time,the removal rates of TN and COD_Crr are 91.03%and 87.36%,respectively.When the sludge return flow is small,the sludge is easily deposited and cannot be in full contact with the sewage,which is unfavorable for the removal of various pollutants.If the sludge return flow is too high,the sediment will be stirred during the water discharge period,resulting in an increase in the effluent SS and COD_Cr.Therefore,when the system is running,8m³/h is the optimal sludge return flow.At this time,COD_Cr,SS,NH₄⁺-N,TN and TP all have better removal effects.The filler filling ratio of the sequencing batch mud-film composite biological pool is the best at 30%,and the continuous improvement of the filling ratio can not obtain better effluent quality.The increase of the water filling ratio of the sequencing batch mud-film composite biological pool can obtain a higher treatment water volume,but the treatment effect is reduced.When the water filling ratio is 0.2,the removal ability of COD_Crr and NH₄⁺-N is the strongest,and the removal rates are higher than 90%and 95%respectively.The effluent can meet the requirements of Class V water quality of Surface Water Environmental Quality Standard;for TN and The removal ability of SS is stronger,and the removal rate is higher than 95%and85%respectively.The effluent can be superior to the Class A emission standard of Pollutant Discharge Standard for Urban Sewage Treatment Plants,especially TN can be stable below5mg/L;The removal capacity of TP is generally higher,the removal rate is above 85%,and the effluent occasionally appears to be higher than the Class A emission standard of Pollutant Discharge Standard for Urban Sewage Treatment Plant.When the water filling ratio is 0.22,it can reach the Class A emission standard except TP;when the water filling ratio is 0.26,it can reach th Class B emission standard except TP.