Mixing zone analysis of surface brine discharges in coastal waters

The potential impacts of surface discharges of heated brine from a co-location power generation and seawater desalination plant in the coastal marine environment are investigated using CORMIX mixing zone model. Simulations are carried out for two scenarios: Scenario I is used to represent the positively buoyant heated brine discharge from a thermal desalination plant, and Scenario II represents the negatively buoyant heated brine discharge from a membrane desalination plant. In contrast to Scenario I, where discharge plume rises towards the surface, discharge plume for Scenario II would tend to sink and spread at the seabed. Due to inherent uncertainty in the input data, sensitivity analysis was conducted using iterative CORMIX simulations by varying the ambient velocity (to evaluate the effect of uncertainty in sea conditions), the discharge flow rate (to evaluate the effect of uncertainty on the desalination plant’s operation), the discharge density (to evaluate the effect of uncertainty on the brine characteristic) and the water depth at the open discharge channel (to evaluate the effect of uncertainty in coastal hydrographic features). Scenario I results show that the overall temperature rise is between 1.0 to 2.1oC (above ambient) at the end of the specified regulatory mixing zone of 300 m radius; and Scenario II results are in the range of 4.2 to 6.4oC (above ambient).