Vibratory shear enhanced process (VSEP) for treating brackish water reverse osmosis concentrate with high silica content

Abstract In this study, a vibratory shear enhanced process (VSEP) was used to treat the concentrate generated from a spiral wound reverse osmosis (RO) system and increase the overall feed water recovery during brackish groundwater desalination. The feed water recovery of the spiral wound RO system was restricted to less than 75% due to silica polymerization on the membrane surface. Due to the high shear rate generated near the membrane surface by the VSEP system, high fluxes (50 – 100 Lm -2  h -1 ) were achievable. Although silica levels exceeding 240 mg/L were present in the spiral wound RO concentrate, deposition of colloidal silica was restricted on the VSEP membrane surface. But, the VSEP system did not prevent the precipitation of barium sulfate and required frequent chemical cleaning. Utilization of antiscalants and lowering of initial specific flux did not result in reducing the scaling potential but implementation of continuous crossflow operation resulted in a lower rate of specific flux decline. The rejection property of the VSEP system for ions, metals and organics was comparable to a spiral wound RO system. By using a VSEP system to treat spiral wound RO concentrate, the overall feed water recovery of the desalting process was enhanced.

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