Disposal to the marine environment is generally regarded as an effective means of disposing of sewage effluent. In recent years legislation has been introduced to enable marine disposal in a more controlled and environmentally acceptable manner. The discharger must prove to the regulatory authorities that the proposed discharges comply with the relevant legislation.

This paper concentrates on the environmental aspects of marine disposal systems and gives examples from the UK. Emphasis is given to mathematical modelling techniques used to assess compliance with relevant legislation. Data requirements for model set up and calibration are discussed, together with assessment of the level of calibration achieved for two specific coastal applications. An improved representation of wind stress effects on the water column and requirements for a special radiation condition at open boundaries to render the boundary transparent to outgoing transients are also discussed.