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

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 50 m3/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 125,000 mg/L. The results showed that the evaporator-crystallizer was able to concentrate the EDR–RO brine to a conductivity of just over 250 mS/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 nearzero ZLD approach to produce freshwater and minimize brine discharge when treating basal aquifer water. © 2015 Elsevier B.V. All rights reserved.

This proof-of-concept study was conducted to assess the efficiency of an EDR–RO high recovery hybrid system to treat basal aquifer water. The pilot plant was also equipped with a low-temperature evaporator/crystallizer to handle the final brine reject. The results indicated that the pretreatment through sedimentation and UF proved to be effective and reliable by removing both suspended solids and turbidity. The EDR–RO pilot plant achieved recoveries of approximately 77%. Brine concentrations of 92,000 mg/L up to 125,000 mg/L could be expected by the hybrid EDR–RO system. Under non-optimized energy consumption, the EDR–RO plant operated with 17 kWhe/m3 influent. However, electrical energy consumption could be reduced to less than 10 kWhe/m3 Conductivity (mS/cm) Flux Operational Time (Hours) Fig. 6. Conductivity of the evaporator/crystallizer (SaltMaker™) concentrate.