Modelling and environmentally sound management of brine discharges from desalination plants

Sea water desalination plants discharge a concentrated brine effluent into coastal waters. Modem, large capacity plants require submerged discharges, in form of a negatively buoyant jet, that ensure a high dilution in order to minimize harmful impacts on the marine environment. Existing design practice favors a steep discharge angle of 60 degrees above horizontal that is based on very limited laboratory data on dilutions at the level of maximum rise. However, examination of more recent laboratory data and the parametric application of CorJet, a jet integral model within the CORMIX expert system suggest that flatter discharge angles of about 30 degrees to 45 degrees above horizontal may have considerable design advantages. These relate to better dilution levels at the impingement location, especially if bottom slope on port height are taken into account, better offshore transport of the mixed effluent during weak ambient current conditions, and the ability to locate in more shallow water near-shore.