The impact of rainwater reuse on CSO emissions

The increasing consumption of drinking water puts a heavy burden on our fut ure water resources. Therefore the reuse of rain water in households can be a good option to tackle this problem. On the other hand the rapidly draine d rain water leads to problems in the combined sewer systems and watercours es. If the storage in the rain water tanks can be used to flatten the rain water runoff, rain water tanks can have an additional benefit. The effect o f rain water tanks on the combined sewer overflow (CSO) emissions is theref ore investigated with a reservoir model. Compared with storage in the combi ned sewer system or at the overflow, storage in rain water tanks will be mo re efficient in reducing the overflow emissions. However much more storage in rain water tanks must be provided to obtain the same overflow frequency as when downstream storage is used, because the storage in rain water tanks is less frequently available. When all the economical, social and environm ental aspects are considered, rain water tanks can certainly be promoted as a good solution. (C) 1999 IAWQ Published by Elsevier Science Ltd. All righ ts reserved.