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Reverse osmosis brine concentration using falling film freeze crystallisation technology: a pilot-scale study
DESALINATION AND WATER TREATMENT, Volume: 203, Pages: 11 - 34
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The reverse osmosis (RO) desalination process has increasingly been utilized with aim of producing drinking water from different marginal sources of water such as seawater, and brackish ground and surface water, due to water scarcity. Unfortunately, desalination applications are limited by the brine...
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The reverse osmosis (RO) desalination process has increasingly been utilized with aim of producing drinking water from different marginal sources of water such as seawater, and brackish ground and surface water, due to water scarcity. Unfortunately, desalination applications are limited by the brine disposal challenges including the adverse impact of brine on the surrounding environment. Therefore, this paper is focused on the technical evaluation of falling film freeze crystallization (FFFC) technology for treating and concentrating RO brine. An industrial pilot plant using the FFFC process was tested and assessed for concentrating RO brine in this study. The experimental results showed that the crystallization experiments using a feed stage (without the sweating process) and at the operating end-point heat transfer medium (HTM) temperature of –6°C, achieved a salt rejection ratio and water recovery ratio of 56.6% and 49.8% respectively. Whereas at the endpoint HTM temperature of –24°C, the salt rejection ratio and water recovery ratios were 24.5% and 84.6% respectively. The multi-stage process experiments using feed and rectification stages (without the sweating process) achieved a salt rejection and product water recovery ratio of 46.89% and 64.24% respectively. By using a multi-stage process including feed, rectification, and stripping stages (with the sweating process), the salt rejection and product water recovery ratio reached 70.68% and 50.15% respectively. In general, the results showed that the FFFC technology, using a single freezing stage and without the sweating process, would be an ideal treatment system for concentrating RO brine and to produce saline water to near seawater quality that can be used directly as feed water for a RO plant. The research proved that the investigated FFFC process can be considered as a great solution available for brine concentration and as an alternative for reducing the environmental impact of the large volume of waste streams from coastal and inland desalination plants.
Faculty of Science and Engineering