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The current proposal for a revised European Directive concerning the quality of bathing water significantly increases the demands for the control of wet-weather discharges. A densely urbanised combined catchment was modelled for a 19-year long rainfall series in order to assess the current situation and to evaluate the benefits of potential solutions. Storage and advanced physical-chemical treatment of stormwater in the STP may significantly contribute for the reduction of the overflow volumes but reductions of the spill frequency under 2.5 spill days per bathing season are hardly obtained. This study reveals the severe strains that the local rainfall pattern may place on the control of the frequency of wet-weather discharges, pointing to serious technical, social and economical implications, at the local and at the national level, if the current proposal for a revised European Directive on Bathing Water is enforced. [ABSTRACT FROM AUTHOR]

Wet weather urban discharges are responsible for bathing water contamination. The proposal for a revised EU Directive concerning the quality of bathing water imposes significantly more stringent requirements for the management of bathing water quality, with particularly important repercussions on beaches subjected to short-term pollution incidents. The paper reviews the aspects from EU legislation most directly related to the problem of wet-weather discharges, placing special emphasis on the recent revision process of the Directive on bathing water quality, and evaluates the benefits of some potential solutions based on continuous modelling of a combined sewer system. Increasing the sewer system storage capacity or the STP hydraulic capacity may substantially reduce the untreated discharge volumes, but spill frequency reductions under 2 to 3 spill days per bathing season will hardly be achieved. Results show the severe strains that local rainfall patterns would place on compliance with the Commission's proposal for a revised Directive and highlight the importance of the changes introduced in the amended proposal recently approved by the Council, making it less prescriptive if adequate measures are adopted to prevent bathers' exposure to short-term pollution incidents. [ABSTRACT FROM AUTHOR]