Calculation of municipal sewage pollutant loadings and centralized sewage collection ratio

Abstract

The centralized collection rate of urban sewage is a key indicator of the operational efficiency of urban sewage systems, urban sewage pollutant loading is an essential parameter for calculating the sewage collection ratio. The high overflow of urban sewage systems and lack of monitoring data pose difficulties in calculating sewage collection ratio. By using the urban sewage system model and regular domestic water consumption and sewage treatment information, this study first time proposed two methods, which were based on the influent flow and pollutant loadings of the sewage treatment plant to calculate the urban sewage pollutant loadings and sewage collection ratio. The applicability of two methods was demonstrated including the required data, specific steps, and calculation results by a case of an urban area with almost 110 km2 square meters and nearly 100×104 inhabitants in a city in the Yangtze Delta area. The applicability of each method was discussed. Furthermore, the effects of the commuters, industry and commercial activities, personal discharge load on the estimation of sewage collection ratio in the cities at different levels of economic development are discussed and analyzed. The methods introduced in this study had practical significance for calculating the sewage collection ratio and evaluating the operation efficiency of urban sewage systems in China and part of the other countries.