Study On Characteristics Of Sewer Wastewater And Optimization Operation Strategies Of Sewer System

At present, systematic and complete sewer systems have been established in most cities in China, while the operation and management of sewer systems are still simple and extensive. Meanwhile, the public understanding of features of sewer system operation also needs to be enriched. Based on using the sewer system of Lucun WasteWater Treatment Plant (WWTP) as the case, variation characteristics of sewer wastewater quantity and quality were studied in this thesis. Moreover, with the assistance of the sewer system model and the wastewater treatment process model, three kinds of optimization operation methods of sewer systems aiming at improving effluent water quality were developed. The effects of those methods were analyzed based on the effluent water quality of the WWTP.Statistic approaches like Regression Analysis and Spectrum Analysis were applied to elucidate the variation characteristics of the wastewater quantity in the case. It showed that the deviation of the wastewater quantity in one year was 10%, and the quantity of wastewater had a significant period of 24 hours. Five factors influenced the amount, including the flow from pump station at the upstream, the inflow of industry wastewater, the dry weather flow, the runoff and the rainfall induced infiltration water. The flow from pump station took up 83% of the wastewater quantity, but it did not vary dramatically; the amount of industry wastewater inflow was little; the dry weather flow had significant variation periods and changed a lot from month to month; the year value of the quantity of the runoff and the rainfall induced infiltration water were both 10% of that of the dry weather flow, the runoff coefficient was approximately 0.112, and the rainfall induced infiltration water was impacted by the rainfall in the previous three days.Methods like Regression Analysis and Cluster Analysis was applied to interpret the variation features of wastewater quality in the case. The results showed that the wastewater quality followed significant daily variation rules, the wastewater quality in the dry days was different from that in wet days, and the wastewater quality was significantly influenced by the rainfall. In addition, with the help of Multiple Regression and Artificial Neural Networks, the correlation between wastewater qualities at pump stations and the outfall of the sewer system was determined, and prediction models for the effluent water quality was developed. And Cluster Analysis was used to recognize the operation features of pump stations and classify them.The sewer system model Storm Water Management Model (SWMM) and the wastewater treatment process model Activated Sludge Model (ASM) were built up and calibrated based on the situation of sewage system in the case. Different strategies, including the setting of online storage tanks, the optimization operation of first stage stations and the optimization operation of inflow pumps of the WWTP, were developed. Based on SWMM and ASM models, their impacts on the effluent waster quality of the WWTP were analyzed and compared. The results of simulations showed that the first strategy had no effects; while the other two could assist in reducing the events of exceeding standard and improve the effluent water quality.