Low-recovery, -energy-consumption, -emission hybrid systems of seawater desalination: Energy optimization and cost analysis

Abstract

Ultraconcentrated seawater disposal is detrimental to marine biota, and carbon emissions from desalination processes are detrimental to the atmosphere. These detrimental effects are expected to increase, given the continuously growing global water demand and the associated water stress problems caused by water scarcity and population and economic growth. Along with political inclination to impose strict environmental regulations and a carbon tax on the price of freshwater, developing low-energy-consumption, low-carbon-emission desalination systems operating at low recovery is the future of SW desalination. Such desalination systems can be achieved by integrating electrodialysis, which does not have driving force limitations, with nanofiltration and brackish water reverse osmosis (RO), which provide low-energy-consumption desalination regions, to decrease energy consumption below that of current state-of-the-art RO systems. In this study, iterative optimization algorithms were developed for hybrid desalination systems. As a result, energy consumptions as low as 1.3 kWh/m(3) were achieved at recoveries < 30%. Despite the higher cost of freshwater production compared with that of state-of-the-art RO systems, owing to utilization of larger membrane areas, the hybrid systems reduced carbon dioxide emissions and brine concentrations from 63 to 26 and 41 to 34%, respectively.