Capacitive Deionization for RO brine recovery in NEWater production

Abstract

Reverse osmosis (RO) brine from water reclamation facility is a potential untapped water source, provided a feasible and economical treatment process is available to recover this waste stream. Organic and inorganic compounds are two major groups of pollutants in the RO brine. In this study, an integrated treatment scheme consisting of a biological activated carbon (BAC) column and a low pressure Capacitive Deionization (CDI) process was investigated. BAC was used as a pretreatment to remove the organic compounds prior to the inorganic removal using the CDI process. Two empty bed contact times, namely 20 min and 40 min tested in the BAC columns provided similar TOC removal efficiency within the range of 15–21%. High ions removals of more than 85% from the RO brine were achieved in the CDI process when operated with water recovery up to 89%. This study has successfully demonstrated that the integrated BAC with CDI process has high potential to increase water recovery of a water reclamation plant while gaining the advantage of a reduced volume of RO brine for disposal. This system could further contribute to enhancement of sustainable water reclamation practice.