The environmental implications of implementing the requirement for treatment of coastal sewage prior to discharge, which were put forward in an EC draft Directive on municipal waste‐water treatment, are examined. In order to establish the current situation, the results of a national survey of coastal and estuarine sewage discharges are presented. A review of the impact of sewage discharges on the marine environment is presented in conjunction with an assessment of the impact of sewage‐treatment processes on the land and in the air. These aspects are integrated into overall conclusions about net environmental impact. Finally, a decision‐tree approach to the assignment of priority to additional action required at individual locations is developed.

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