Abstract

Overflows from sewers always occur and in particular, combined sewer overflows (CSOs) may damage the surrounding bathing waters and the environment. Introduction of real-time control (RTC), monitoring, and regulation provides additional knowledge about the system’s capabilities or constraints. A combination of RTC and computer programs like MOUSE creates a solid background for optimizing the sewer system. For example, it enlarges the system’s capacity by small means and/or establishes retention basins or systems of interconnected basins, which results in reduced environmental impacts. Considering these possibilities, the City of Copenhagen proved it possible to establish several harbor baths in places where bathing was prohibited for decades. Prior to the baths, a bathing water forecast (BWF) system was set up, initially based on a 2D and later on a 3D hydraulic model—MIKE 21 and MIKE 3 FM, respectively—combined with online monitoring of CSOs within the harbor and surrounding areas. The model system has later been extended to cover the effects of CSOs and outlets from wastewater treatment plants on most of the Danish coast of the Sound and a part of the Swedish coast north of the Sound. The system covered a shoreline of approximately 200 km. The BWF is updated at least every 12 hours and always after CSOs. The forecasts are available through the internet, SMS, and through Smartphone applications. The BWF may serve as an example for future models in dense populated areas near bathing waters. Such models will be needed, as EU countries must promptly notify the public in the near vicinity of each bathing water before the end of 2014, if it is subject to short-term pollution. The City of New York describes the Copenhagen way for “redeveloping industrial harbor for public swimming” as best practice.