Improved Discharge Configurations for Brine Effluents from Desalination Plants

Abstract

Sea water desalination plants discharge a concentrated brine effluent into coastal waters. Modern, large capacity plants require submerged discharges, in the 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 Existing design practice favors a steep discharge angle of 60° above horizontal, a practice based on limited and outdated laboratory data for dilutions at the level of maximum rise. Examination of more recent laboratory data and the parametric application of a jet integral model suggest that flatter discharge angles of about 30–45° above horizontal may have considerable design advantages. These relate to better dilution levels at the impingement location, especially if bottom slope and port height are taken into account, there is better offshore transport of the mixed effluent during weak ambient current conditions, and there is the ability to locate in more shallow water near shore.