Numerical Simulations of Brine Dispersion Associated with the Discharge of the Proposed Stage 2 of the Perth Seawater Desalination Plant

The combination of growth and climate change is driving a need for additional water source options to secure the projected water demands for Perth’s Integrated Water Supply Scheme (IWSS). In 2018, Water Corporation, Western Australia’s main water utility, completed feasibility investigations for construction of a possible expansion of the existing Perth Seawater Desalination Plant (PSDP). The combined nominal capacity of the existing plant, and possible Stage 2 expansion, would provide approximately 95 billion litres of drinking water a year. This paper presents the results of hydrodynamic and water quality simulations undertaken to simulate the dispersion of the brine effluent on Cockburn Sound from the discharges of both the existing Stage 1 (PSDP1) and a possible Stage 2 (PSDP2). The study benefited from several existing data sets that were used for validation of both near and far field models of the PSDP1 discharge. The data collected over the years as part of the PSDP1 monitoring offered an excellent opportunity to demonstrate the model capability in predicting the effects of the desalination plant discharge on the receiving environment, and increased confidence in the model’s ability to simulate the combined effects of two discharges of similar magnitude in close proximity to each other. While the PSDP2 project is yet to be assessed by environmental regulators, the modelling results indicate the additional discharge from a possible second desalination plant is likely to meet the regulatory criteria applied to Cockburn Sound. As such, and pending approvals, the Stage 2 plant is considered a viable and potential option to support Perth’s future water demands.