In 2000, the European Union (EU) launched the Water Framework Directive (WFD), calling for a good ecological status for water bodies by 2015 through integrated river basin management. Despite huge investments, the river Zenne (Belgium) still acquires high loads of pollutants. A multidisciplinary research project was therefore launched to evaluate the effects of river basin wastewater management plans on the river's ecological functioning. Different water quantity and quality processes were considered, and different models were used for each process. For the integration of these models – in view of a holistic analysis – we opted for the Open Modelling Interface (OpenMI). This paper discusses early results of integrated faecal bacteria modelling considering five models. The integrated model is shown to reproduce concentrations of Escherichia coli (used as indicator faecal bacteria) with ‘Very Good’, and ‘Satisfactory’ accuracy for dry weather, and long-term simulations respectively. For both cases, it is found that the E. coli concentrations in the river are well above EU level for bathing water, with occasional combined sewer overflows (CSOs) from the Brussels' sewer systems making the ecological status even worse. We also found OpenMI-based integration to be very useful. However, the calculation time overhead for such OpenMI integrated models remains significant.

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