membrane distillation

reverse osmosis

brackish water

forward osmosis

Desalination

While mechanical vapor compression is typically applied for the concentration of brine, new approaches that are less costly and less energy intensive are needed to facilitate minimal and zero liquid discharge. Several variations of reverse osmosis for high-salinity desalination and increasing recovery rates beyond the pressure limitation of conventional RO have been proposed in the literature. The promise of these enhanced RO approaches entails a reduction in energy consumption when compared with thermal desalination methods. In this paper, low-salt rejection reverse osmosis (LSRRO), cascading osmotically mediated reverse osmosis (COMRO), and osmotically assisted reverse osmosis (OARO) were comparatively assessed via module-scale, cost optimization models to gain an accurate perspective of the performance differences between each of these configurations. We quantified the optimal levelized cost of water (LCOW) of each technology for the case of desalinating feedwater at 70 g/L at 75% recovery, which would result in a brine concentration near 250 g/L, a level that allows further treatment with crystallizers. For baseline scenarios, LCOW results for LSRRO, COMRO, and OARO were 6.63, 7.90, and 5.14 $/m 3 of product water, respectively, while the corresponding specific energy consumption (SEC) values were 28.9, 12.8, and 10.3 kWh/m 3 . A sensitivity analysis is also presented. • Module-scale, cost optimization models were developed for LSRRO, COMRO and OARO. • We considered desalinating feedwater with 70 g/L TDS at 75% water recovery. • LCOW and SEC results ranged from 5.1 to 7.9 $/m 3 and 10.3 to 28.9 kWh/m 3 , respectively. • OARO has the lowest LCOW, COMRO has the highest LCOW, and LSRRO has the highest SEC. • COMRO can achieve water recovery at high feed salinities without multiple stages.

Pathways for minimal and zero liquid discharge with enhanced reverse osmosis technologies: Module-scale modeling and techno-economic assessment