ABSTRACT
Sewer systems can be direct contributors of pollution to watercourses. Stormwater outfalls can discharge pollution, as discussed in Section 6.4; and serious short-term pollution can arise from combined sewer overflows, as considered in Chapters 2 and 13. The effects can be counteracted by measures such as the inclusion of additional storage within the system and by rehabilitation or replacement of CSO structures. In order to design these measures to achieve high standards, and to evaluate them fully, it is necessary to have information on the rate at which pollutants flow into the structures from the sewer system, and how the pollutants are distributed in the storm flow. This information is provided by models of quality (distribution of pollutants) in sewer flow.
