In this study, a method is proposed to activate the maximal in-sewer storage volume of a combined sewer system (CSS) with a limited number of flow regulators to reduce negative impacts of combined sewer overflows (CSO). Based on a detailed analysis of the CSS structure, it indicates suitable locations to install flow regulators. The method has been developed in the programming language R and tested on the Berlin’s biggest CSS. Flow regulators have been implemented in the CSS Infoworks model at the five most suitable locations found and tested for different rainfall conditions. It was found that significant additional in-sewer storage capacity can be activated (~50% of the already existing capacity) leading to CSO volume and pollutant load reductions up to 62% for a three-monthly rain event of 60 minutes duration.

Whilst the importance of integrated modelling of urban wastewater systems is ever increasing, there is still no concise procedure regarding how to carry out such modelling studies. After briefly discussing some earlier approaches, the guideline for integrated modelling developed by the Central European Simulation Research Group (HSG - Hochschulgruppe) is presented. This contribution suggests a six-step standardised procedure to integrated modelling. This commences with an analysis of the system and definition of objectives and criteria, covers selection of modelling approaches, analysis of data availability, calibration and validation and also includes the steps of scenario analysis and reporting. Recent research findings as well as experience gained from several application projects from Central Europe have been integrated in this guideline.

The importance of integrated modelling of urban wastewater systems is ever increasing, also due to the European Water Framework Directive. In order to facilitate its practical application, the Central European Simulation Research Group (HSG) has prepared a guideline document, suggesting a seven-step procedure to integrated modelling. Findings of recent research and application projects in Central Europe have been integrated in the guideline. The present paper outlines this guideline document. The full guideline will be made available on the Internet.