Basic Research On Operation Optimization Of Activated Sludge Process In Sewage Treatment Plant

With the rapid development of environmental protection in China and the increasing number of sewage treatment tasks,people began to pay attention to the efficiency and energy consumption of sewage treatment.In order to improve the level of sewage treatment and realize energy conservation and environmental protection,it was necessary to optimize the activated sludge process of sewage treatment plant to maximize the total utility of sewage treatment.This study explored the feasibility of process operation optimization of activated sludge in sewage treatment plant from two aspects of energy saving,consumption reduction and quality improvement increment.Firstly,the total oxygen transfer coefficient（KLa）was measured by simulating the aeration system with the largest energy consumption in the sewage treatment plant,it was of great significance to improve the operation efficiency of aeration system and realize the energy saving and consumption reduction of sewage treatment plant.The change of DO value in the aeration system was measured by changing the aeration volume,mixing intensity and simulating the blockage of aeration equipment in the laboratory,and the difference of KLa（20℃）before and after changing the variables was calculated and compared.The results showed that KLa（20℃）is higher before aeration than after blockage.With the increase of mixing intensity,KLa（20℃）increased gradually,and then the increase rate slowed down.If the mixing intensity continued to increase,the improvement effect of KLA（20℃）of aeration system was not significant.The KLa（20℃）value increased linearly with the increase of aeration volume.Then the online monitoring system of sludge performance was used to monitor the change of DO value in the sludge water and calculate R,and evaluate the activity of biochemical sludge online in real time,so as to ensure the effectiveness of oxygen consumption in the system,improve the sewage treatment capacity and reduce the excessive energy consumption of biochemical system.Through online measurement of R_en,R,R_maxand nitrification activity of activated sludge,it was found that the R_enwas stable around 8.42 mg/L.The characteristics of the R curve of activated sludge were consistent with the description curve of the relationship between microbial proliferation rate and substrate concentration in Monod equation.When R reaches the maximum,the ratio of COD concentration to MLSS in raw water L>0.005.Using ATU as nitrification inhibitor,the measured nitrification activity of activated sludge is close to the theoretical oxygen consumption,and the monitoring results were effective,which can be used to verify the accuracy of measuring nitrification activity using online monitoring system.Subsequently,the ASM3 model of activated sludge was simplified,and the denitrification process of heterotrophic bacteria and aerobic bacteria was ignored.Only the aerobic nitrification process of aerobic bacteria was studied,and some kinetic parameters of sludge in the nitrification reaction process were corrected.The saturation constant and yield coefficient of nitrifying bacteria were higher than the typical value,and the NH4₊^--N concentration in the inlet and outlet water was close to the measured value.Through the rapid online estimation of NH4₊^--N concentration in the inlet and outlet water of the sewage treatment plant reactor,the inlet load of the sewage treatment plant activated sludge reactor and whether it was in normal operation state can be judged,and timely adjustment can be made to make it work in the best state.Finally,the hydrocyclone was used to optimize the sludge of the secondary sedimentation tank,which can not only realize the stable operation of the biochemical system,but also increase the sewage treatment capacity of the activated sludge system.It not only increased the significant economic benefits of the sewage treatment plant,but also reduced the difficulty of advanced treatment.By comparing the changes of sludge solids,sludge enrichment ratio,sludge sedimentation performance and sludge activity before and after swirling,it was found that after swirling,the underflow sludge sludge enrichment ratio increases;The SVI decreases,and the reaeration after swirling treatment will not cause the change of sedimentation.Besides,MLVSS/MLSS and SOUR of underflow sludge increased after swirling,and the agglomeration of underflow sludge was obvious,and the bacterial micelle was more than that of inlet sludge,it showed that the sludge activity of underflow sludge became better and the sedimentation performance was improved after swirling.By comparing the microbial flora before and after clone,it was found that the sedimentation performance,activity and ability of degrading pollutants in sewage were improved after clone,and the sedimentation performance and sewage treatment effect of biochemical system could be improved by returning the bottom flow sludge to biochemical section.The results confirmed the feasibility of using hydrocyclone technology to separate sludge from secondary sedimentation tank.