Research On Dynamic Variation Of Wastewater Quantity And Quality In Sewer System Based On Pollutant Hydrograph

Municipal wastewater collection system plays an important role in protecting public environment and health.Research on the fluctuating pattern of wastewater quantity and quality is beneficial for evaluation,regulation and operation of wastewater collection and treatment system.Based on studying the variation law of different components in sewer system,a pollutant hydrograph model was proposed to evaluate the inflow and infiltration process in different rainfall events and various sub-catchments.Furthermore,a visualized generator was constructed to simulate and predict the variation of wastewater quantity and quality in sewer system.Main conclusions includes:The relationship between level and flow at dry weather was fitted by exponential function.The variation of water quantity and quality was characterized by second order Fourier series model.The periodic regularity of dry weather flow and quality were near 24 hours.The mean value and fluctuation range of water quality such as COD,ammonia,phosphate,conductivity in residential area are larger than that in pump stations and WWTP.Among various pollutant indexes,conductivity was chose as a prior indicator to assess inflow and infiltration process due to its higher response sensitivity to inflow and infiltration according to KS test result.A pollutant hydrograph model to evaluate the dynamic process of inflow and infiltration was proposed by coupling conservation of mass equation and instantaneous unit hydrograph in the form of u?0,t?=1/??????/?^?-1?0)^?-/?.By fitting the model to the online monitoring conductivity data,in the monitoring residential area:the inflow rate was 22.7%and the infiltration rate was 13.2%for light rainfall events;the inflow rate was 10.1%and the infiltration rate was 8.2%for medium rainfall events;the inflow rate was 8.1%and the infiltration rate was 3.5%for heavy rainfall events.The model uncertainty under dry weather condition and in different sub-catchments,different rainfall types,different rainfall events was discussed.The result indicated that improving the acceptable threshold have most significant influence on the parameter K_RDI and N_RDI.The 90%confidence interval of parameters were obtained.Take small rainfall event for example,the inflow rate and infiltration rate was[20.3%,23.8%]and[12.3%,15.8%]separately for light rainfall events.The difference of parameter distribution in different sub-catchments reflects the comprehensive effects of physical features such as sewer system healthy condition and so on.Finally,based on the dry weather model,inflow and infiltration model,a visualized generator was constructed with Simulink module to simulate water quality and quantity variations at various rainfall scenario in different sub-catchments corresponding to residential area,pump stations and WWTP.