C. Engelhard

Suitability of CSO performance indicators for compliance with ambient water quality targets

The aim of the present paper is to assess the applicability of easily obtainable emission-based performance indicators for combined sewer overflows in order to describe the water quality in the receiving water. Theresultsof the computer simulations showed a correlation of some emission-based indicators with discharged loads. However, none of the emission-based indicators was correlated to acute effects. Owing to the correlation of the total overflow volume with the impacts in the receiving water, the outcomes of this study suggest thatreceiving waters in regions with a high annual rain volume are more endangered by combined sewer overflows.

A software-based sensor for combined sewer overflows

A new methodology for online estimation of excess flow from combined sewer overflow (CSO) structures based on simulation models is presented. If sufficient flow and water level data from the sewer system is available, no rainfall data are needed to run the model. An inverse rainfall-runoff model was developed to simulate net rainfall based on flow and water level data. Excess flow at all CSO structures in a catchment can then be simulated with a rainfall-runoff model. The method is applied to a case study and results show that the inverse rainfall-runoff model can be used instead of missing rain gauges. Online operation is ensured by software providing an interface to the SCADA-system of the operator and controlling the model. A water quality model could be included to simulate also pollutant concentrations in the excess flow.