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Abstract

The main water planning and management challenge facing Bahrain is in how to balance water availability and water use on a long-term basis in the face of increasing demands under the least economic and environmental costs and without endangering socio-economic development. To meet escalating municipal water demands desalination is becoming inevitable, which is associated with substantial financial, economic, and environmental costs. In this research, the environmental impact of seawater desalination on the surrounding marine environment is assessed at a government-owned MSF desalination plant (Sitra Power and Water Station (SPWS)). The assessment used a number of environmental indicators, namely temperature and salinity (TDS) at the desalination plant outfall area, and included a field survey to characterize the outfall area of the desalination plant, simulation modeling of the outfall area using CORMIX hydrodynamic model after its calibration by field data, and investigating mitigation scenarios. Characterization and simulation of elevated temperature and salinity of brine discharge was made for the winter season, where the maximum thermal impact occurs. The simulation indicated that the brine temperature is within Bahrain Mixing Zone Standards. The brine plume elevated temperature drops to ambient temperature within 37 minutes after traveling a distance of 350 meters downstream. The brine plume elevated salinity drops to the ambient seawater salinity within 41 minutes and a distance of about 390 m downstream. The effectiveness of a technical mitigation option of mixing of power cooling water with brine during the winter season was assessed and was found to have the potential of reducing the impact of the temperature by 30% and salinity by 38% in comparison to the current conditions. It is recommended that other quantifiable environmental indicators to characterize and assess desalination impacts on the marine environment, such as brine chemicals, air pollution, and biological communities, are used in assessing the environmental impacts of desalination; a regular monitoring program of seawater quality in the Near Field Region (NFR) and the Regulatory Mixing Zone (RMZ) is designed and implemented, and similar investigative and assessment studies are conducted on all the other desalination plants in Bahrain.

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