Modelling an urban wastewater system via a space–time multivariate calibration to understand and improve water bodies quality

ABSTRACT The European Water Framework Directive requires good quality status for water bodies remaining solely attainable through a global approach. Urban wastewater integrated modelling is a promising tool for this purpose. However, certain barriers still hinder its application, such as the significant amount of data required and specifically in the sewer system, the issues with data quality or the monitoring and maintenance costs. This study develops an integrated model for Dijon Metropole in France using multiple hydraulic and quality data sources (e.g. sensors, analysers, laboratory measurements) and calibration criteria. The results show that long-term trends can be predicted for hydraulic and quality variables. The scenarios demonstrate that combined sewer overflows are responsible for most of the anoxic and ammonium high concentration periods in the rivers during rain events compared to the Water Resources Recovery Facility (WRRF). Therefore, adding storm tanks in the wastewater system will reduce stress on aquatic organisms during rainfall events. Reducing WRRF discharge during wet weather can also reduce the average and percentile of ammonium in the river. These results indicate that strategies should be adapted depending on the water quality objective (biological and/or physico-chemical) and the sensitivity of the organisms present in the river.