Hazard assessment of bacterial contamination in coastal waters using a metocean modeling system: Application to bivalve mollusk harvesting areas in Cadiz Bay (SW Spain)

Metocean modeling resources from an operational oceanography system are applied to assess the hazard of bacterial contamination, resulting from domestic/industrial wastewater discharged into potential bivalve mollusk harvesting areas in Cadiz Bay (Andalusia). The proposed methodology is aimed to at meeting the European Union regulations and best practices for the management and monitoring of this harvesting activity. Modeled current fields, corresponding to scenarios with different wind and tidal conditions, are incorporated in a Lagrangian particle-tracking model, specifically designed to simulate the fate of the bacterial content of wastewaters discharged into the Bay. Numerical results are used to obtain various indices of occurrence and hazard maps of fecal contamination in seawater. The proposed indices also allow estimating fecal contamination fields if appropriate information of discharges and bacterial loads of the wastewater sources are available. Qualitative validation of results shows considerable agreement with measured contamination patterns. The areas with highest exposure to bacterial contamination are the Sancti Petri Channel and the central region of the Inner Bay, although a substantial variability depending on wind conditions is found. Unauthorized occasional wastewater discharges have a considerable impact on local water quality, while regulated wastewater sources are responsible for the larger-scale bacterial contamination pattern. The methodology developed is exportable to other environments and coastal management activities.