Forward osmosis for industrial effluents treatment – sustainability considerations

Abstract

Access to clean water resources has become a global challenge in recent times, especially in developing countries, where huge amounts of highly polluted industrial and municipal effluents are produced and discharged into the receiving environments. Applications of membrane technologies to deal with effluents from various origins have recently received a great deal of attention due to their inherent advantages compared to other physico-chemical methods developed so far. Forward osmosis (FO) is among one of the efficient membrane-based processes adopted by wastewater treatment facilities, with various configurations currently being transferred from laboratory and pilot-scales to large-scale applications. Still, FO technologies are plagued with drawbacks such as fouling, internal concentration polarization (ICP), reverse solute flux and draw solution recovery, which invariably increases the cost of operation and restricts the feasibility for large-scale and long-term use because economic considerations are the most important sustainability criteria when selecting a wastewater treatment technique among the various alternatives. Several modifications have been introduced in recent years to overcome the existing limitations, such as incorporation of engineered nanomaterials onto the membrane surface to mitigate membrane fouling and to enhance their life-time, thereby minimizing the cleaning and (when necessary) replacement costs. Several FO based pre-treatment technologies have also been introduced for complex effluents treatment to minimize the operational costs arising from cleaning and replacement activities. Therefore, assessing the performance of such technologies according to sustainability indicators is the key to ensure long-term benefits from the application of FO technologies for the treatment of highly polluted effluents. In this review, treatment and water reclamation from industrial effluents using FO process and the current states of the standalone and hybrid technologies considering sustainability criteria are discussed. Scaling-up opportunities for the existing lab-scale modules have been evaluated and environmental footprint of the under-developed technologies are discussed. This review will therefore aid in selecting the most suitable configurations of FO technologies (standalone/hybrid) to deal with the highly polluted effluents for real world applications and to direct future studies in this emerging area. Perspectives and recommendations for future studies are also included.