Using Salt Gradient Energy and Thermal Energy to Enhance Reverse Osmosis Desalination

Abstract

Improving desalination energy efficiency is crucial for meeting rising global water demands. Reverse osmosis (RO) is a common desalination process that uses an applied pressure to overcome the natural osmotic potential of seawater to drive nearly pure water permeate through a semipermeable membrane. However, it has high specific energy consumption ranging from 4-5 kWh/m3 and environmental issues associated with discharging the highly concentrated brine that is left over after separation. This work investigates two methods of improving the energy efficiency of RO desalination: (1) Recovering salt gradient energy from desalination brine, and (2) Using thermal energy to pre-heat RO feed water and reduce mechanical pump work.