Impact of the Coastal Intake Environment on the Operating Conditions of Thermal Desalination Plants: A Case Study in the United Arab Emirates
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The energy required to operate coastal thermal desalination plants and thus the relevant costs are greatly affected by coastal hydrodynamics. A multi-layered hydrodynamic model was developed in this study for a coastal area in the United Arab Emirates to investigate such an effect. The simulation was carried out using a curvilinear grid model with sigma layers in the vertical direction which incorporates the transport of salt and temperature interactively with water dynamics. Several simulations were carried out to investigate the impact of the brine and warm cooling water discharges released from the desalination plant as well as other nearby industrial facilities using a three-dimensional advection-dispersion surface formulation. The model output was used to determine suitable locations and configurations for water intakes as well as outlets to maintain the temperature and salinity of the water introduced to the plant at optimum acceptable levels, so that maximum efficiency and minimum operation cost are achieved. A number of alternative scenarios were also considered to fully assess the problem. This includes extreme desalination operation scenarios in summer and winter, possible maximum release of warm water by other industrial facilities, and scenarios of the future expansion of plant production. Three alternatives were investigated including shifting the intake to new offshore locations, moving the outfall away from the intake area, and having the outfall discharge its effluent into further and deeper zones. Cost analysis was carried out for two scenarios to evaluate the operation cost in terms of chemical and energy cost. The first alternative that involved shifting the intake location about 1km offshore was found to be the best option as it achieved the maximum reduction of chemical and energy costs for all tested scenarios when compared with the existing configuration. 2.5% of the total annual cost, equivalent to US $1.2 million is saved, taking into consideration a major expansion to the existing industrial facilities which will produce 10 times the existing effluent levels.
