Estimated inorganic nutrient inputs to the coastal waters of Jersey from catchment and waste water sources

Concern over nutrient levels and eutrophication in the north-east Atlantic sea area has required a reduction in inputs at several urban centres. Implementation of a best European Practice by the States of Jersey has necessitated an assessment of the impact of the Island's waste water treatment works (WwTW) on inorganic nutrient inputs to the coastal zone. Inorganic nutrient concentrations in stream and sewage effluent inputs into St. Aubin's Bay, Jersey, were monitored during the phytoplankton growing season. Inorganic nutrient input budgets were calculated using estimates of runoff based on hydrological data for an instrumented catchment. Results indicated that the WwTW accounted for 54% of the inorganic nitrogen load and 98% of the inorganic phosphorus load over the survey period. The remaining inputs from catchments are driven by the seasonality of flow and nutrient concentrations. Installation of nutrient removal technology at the WwTW would reduce the total inorganic nitrogen load by 33% and the inorganic phosphorus load by 86%. Implications for the WwTW and compliance with the European urban waste water treatment Directive 91/271/EEC are discussed