Dynamic modelling of pollutants from CSOs

In a number of industrialised countries there is an effort made to reduce pollutant discharges from combined sewer overflows. After establishing proper treatment plants the CSO discharges are contributing with a higher percentage of the total pollutant load on the receiving waters. The acknowledgement of this issue has made the authorities in some countries issue requirements for maximum allowed pollutant loads and water quality from individual CSOs. However, in order to make standards for CSO emissions knowledge about the current state is needed and subsequently others needs to be able to document that they are in compliance with the standard. The question is how to calculate the annual pollutant load from a given CSO? The purpose of this article is to present results from calculation of annual loads in different ways.