STORMWATER QUALITY SIMULATION MODEL IN URBAN SEWER SYSTEMS

Abstract

Water pollution of the receiving waters that receive combined sewer overflows (CSOs) from urban sewer pipe systems has been deteriorating and spreading recently. The investigation of reasonable measures to prevent or mitigate the water pollution began to be taken up seriously in the early 1970s. The Public Works Research Institute (PWRI), the Ministry of Construction, has developed a water quality simulation model (PWRI Model) in sewered areas during the mid-1970s and early 1980s. This model, which is usually combined with the RRL method modified by the PWRI to evaluate stormwater runoff, is able to simulate practically the phenomenon in which the pollutants, including BOD, COD, and SS, remaining both on surfaces and in sewers are washed off.
The purpose of this paper is to clarify the adaptability of the model and improve or modify the model if necessary. First, the adaptability was investigated on the basis of the comparisons between observed runoff hydrographs, including pollutographs, and simulated ones in an urban drainage basin which area is about 40 ha. As a result, several methodological problems to be solved were indicated. Second, the modification of the model according to the indications resulted in improving the adaptability considerably.