Fouling of high pressure-driven NF and RO membranes in desalination processes: Mechanisms and implications on salt rejection

Reverse osmosis (RO) membranes are widely used in seawater and brackish water desalination. Although RO membranes achieve high salt removal > 99%, their application is hindered by fouling, thus causing reduction in permeate flux, salt rejection and degradation of the membrane leading to shorter membrane lifespan. This study reviewed fouling of RO membrane during desalination processes. Also, nanofiltration (NF) membrane are briefly discussed due to their remarkable salt rejection efficiency for water softening. Various types of fouling, mechanisms and governing parameters are discussed in detail. The implications of fouling on membrane physicochemical properties and filtration performance are reviewed. Fouling mitigation strategies are presented, predominantly focusing on currently adopted methods. New fouling mitigation strategies are presented together with their challenges and feasibility assessment for adoption at pilot scale. Finally, recommendations are made on possible pretreatment approaches with the potential fouling reduction in seawater desalination.