Abstract:By using the hydraulic model tools, combined with statistical analysis of operating data and test data, the causes of the high water level operation, low water load and not reaching the design conditions of the external trunk sewer for a wastewater treatment plant are diagnosed. The sewage volume, pipe network catchment capacity, trunk pipe water level, lifting pump station capacity and capacity improvement test are systematically analyzed. The conclusion shows that the main cause is the insufficient lifting water volume of the sewage lifting pump station.