Treatment of basal water using a hybrid electrodialysis reversal–reverse osmosis system combined with a low-temperature crystallizer for near-zero liquid discharge

Abstract

Basal aquifer water is saline groundwater that often needs to be dewatered prior to mining. The oil sands industry is seeking cost-effective methods to treat basal aquifer water in order to allow its recycle to the bitumen extraction process. A hybrid desalination system consisting of advanced electrodialysis reversal (EDR)–reverse osmosis (RO) combined with a low-temperature evaporator/crystallizer was assessed as an opportunity to treat basal aquifer water for a near-zero liquid discharge (ZLD) approach. The pilot-scale plant had a capacity of 50m3/day influent. Pretreatment through sedimentation and ultrafiltration proved to be effective in removing both suspended solids and turbidity. The hybrid EDR–RO desalination system achieved about 77% recoveries, with brine concentrations up to 125,000mg/L. The results showed that the evaporator-crystallizer was able to concentrate the EDR–RO brine to a conductivity of just over 250mS/cm, while producing additional freshwater. This proof-of-concept study demonstrated that the hybrid EDR–RO system combined with a low-temperature evaporator/crystallizer was an effective near-zero ZLD approach to produce freshwater and minimize brine discharge when treating basal aquifer water.