Hazard and risk assessment related to CSOs in bathing waters in a context of climate change

16:15 Tuesday 28 May


Room S9


Luca Locatelli (Spain) 1; Beniamino Russo (Spain) 1; Montse Martinez (Spain) 1


Combined sewer overflows (CSOs) affect the water quality of the receiving water bodies and climate change is influencing future scenarios. As part of the BINGO project (European H2020) AQUATEC quantified people health hazard due to poor bathing water quality and the effect of a climate change scenario in Badalona. Badalona is a city that faces the Mediterranean sea and its beaches host over a million visitants per year. The Bathing Water Directive (Directive 2006/7/EC) safeguards public health and protects the aquatic environment in coastal and inland areas from pollution recommending monitoring of two bacteria, Escherichia coli and intestinal enterococci.

AQUATEC developed an urban drainage model to quantify combined sewer volume and spills; then bacteria measurements were used to estimate the concentrations of CSOs and, finally, a 3D marine model was developed to simulate spreading of the bacteria in the sea in front of Badalona. Both models were calibrated using field data and were combined to run continuous simulations of different periods with different inputs: 10 years of observed rainfall and 10 years of past and future decadal realizations.

Hazard and risk for bathers were assessed based on two simulated indicators: the average number of days where the sea water quality is considered poor and the time necessary to recover to an acceptable water quality after CSOs. Finally it was quantified how a future climate change scenario (2015-2024) based on decadal predictions affect the baseline (2005-2014) people hazard.

Overall, there seem to be an insignificant increase of future people hazard over the future 10 years. Further, the methodology presented in this study is generally applicable and the proposed way of quantifying risk for people bathing in water bodies affected by CSOs is useful for regulatory use.