Electrodialysis reversal for industrial reverse osmosis brine treatment

Abstract

Reverse osmosis (RO) brine typically contains high salinity and dissolved organics. Among the different approaches for RO brine management, electrodialysis reversal (EDR) offers high potential due to its moderate energy consumption, anti-scaling and anti-fouling properties, ability to produce highly concentrated brine and ease of operation. However, despite the potential benefits associated with EDR, its application for industrial RO brine management has yet to be adequately explored. This study aimed to evaluate the feasibility of a lab-scale EDR system for water recovery from industrial RO brine and minimizing the volume of the resulting concentrated brine. The relatively high concentration of organic and inorganic foulants such as hardness, sulfate and alkalinity in the industrial RO brine necessitate the assessment of anti-fouling and anti-scaling properties of the ion exchange membranes. In this study, it was noted that the limiting current to prevent polarization during electrodialysis process, in the lab-scale EDR system, was 0.89 A. Total organic carbon (TOC) removal efficiency was about 7.1% and no organic fouling was observed even after 6 d of continuous operation. This observation was probably attributed to the nature of organic foulants present in the industrial RO brine, the majority of which were low molecular weights (LWMs). However, the resistance of the EDR system increased during 8 h of operation due to high scaling potential of the EDR concentrate stream. Overall, the EDR process was able to achieve 85% water recovery and the volume of industrial RO brine was reduced by approximately 6.5 times.