Removal and Fouling Influence of Microplastics in Fertilizer Driven Forward Osmosis for Wastewater Reclamation

Insufficient removal of microplastics (MPs) and nanoplastics (NPs) may exert negative effects on the environment and human health during wastewater reclamation. The fertilizer-driven forward osmosis (FDFO) is an emerging potential technology to generate high-quality water for irrigation of hydroponic systems. In this study, the removal of MPs/NPs by the FDFO process together with their impact on FDFO membrane fouling was investigated, due to FDFO's low molecular weight cut-off and energy requirement by using fertilizer as draw solution. Plastic particles with two different sizes (100 nm and 1 μm) and extracellular polymers released by real wastewater bacteria were utilized as model compounds for FDFO performance comparison. Results show that FDFO membrane system could generate high-quality irrigation water with only fertilizer, completely removing extracellular polymers, MPs and NPs from wastewater. It was found that the MPs and NPs themselves do not cause a significant membrane fouling. Moreover, it could help to reduce the membrane fouling caused by extracellular substances. That is probably because MPs and NPs helped to form a loose and porous fouling layer. Therefore, the FDFO process could be a long-term stable (low fouling) process for the reclamation of wastewater with high-quality requirements.