Physical Oceanographic Studies for the Design of the Athens Sea Outfall (Saronikos Gulf, Greece)

The discharge of about 600 000 m³/day of untreated wastewater into the northern part of Saronikos Gulf constitutes the major source of pollution for the latter. To take corrective measures, a new treatment plant and sea disposal by a deep outfall system is under construction. The basic design concept is to produce a submerged sewage field below the pycnocline, during the stratified period, at a location where the ambient current field is strong enough to advect it diluted to the open sea. Accordingly, the objectives aimed at obtaining accurate descriptions of the annual variation of the density stratification regime and the local current field. The results obtained showed that during summer the density stratification off Psyttalia Island is sufficiently strong to warrant the submergence of the sewage field; moreover, coupled with the virtual absence of upwelling and the presence of a well organized current field ensures the adequate offshore dispersal of the diluted effluent plume.