Applicability of forward osmosis pre-concentration process for resource recovery from municipal wastewater: Opportunities, challenges and current advancements

Over the past decades, forward osmosis (FO) has gained recognition as a promising membrane separation technology for wastewater (WW) treatment and desalination. However, its application as a pre-concentration step in WW treatment processes is still progressing gradually as a novel approach. As an alternative costeffective membrane process, FO relies on the natural osmotic pressure difference between a concentrated draw solution (DS) and the WW to drive water through a semi-permeable membrane, thereby concentrating contaminants in WW while producing a high-purity water stream. The application of FO in existing WW treatment plants, especially for challenging WW treatment, as a versatile tool has received significant interest and increased technological effort to enhance overall resource recovery performance through combination with anaerobic treatment processes. In this review, we first assessed the opportunities for the FO process in various fields of application within municipal WW treatment. Then, the FO process's inherent limitations and technical challenges for subsequent resource recovery processes were discussed comprehensively, considering factors like contaminant rejection performance, salinity build-up, bidirectional solute transfer, and membrane fouling. Additionally, current advancements in the literature to address the challenges of FO-integrated resource recovery processes were compiled, presenting the latest solution pathways as a guideline. Economic aspects of the FOintegrated processes were evaluated to assess their competitiveness and applicability in municipal WW treatment.