The occurrence of microplastics (MPs) in wastewater has been widely reported and wastewater treatment plants (WWTPs) are now considered as a pathway for MPs in the environment. The fate of nanoplastics (NPs) through WWTPs has not been investigated due to analytical challenges in the detection of NPs in water. Hence, the number of NPs/MPs in wastewater could be higher than expected, which poses a concern regarding the performance of WWTPs processes such as filtration units. Due to their small size, NPs/MPs are most likely to foul membrane surfaces and decrease their filtration performance. Membrane fouling is a well-known phenomenon, usually addressed by modifying membrane surfaces to reduce the interactions with particles in water. Among all modification techniques, surface plasma grafting has been reported to successfully increase membranes antifouling properties against proteins and fats. However, the efficiency of plasma coatings to reduce the fouling induced by NPs/MPs has not been investigated yet. Limiting the fouling mechanism of NPs/MPs is critical to maintain high filtration performance and address the detrimental impact of NPs/MPs on WWTPs filtration processes. In this study, the fouling of a polysulfone ultrafiltration membrane induced by poly(ethylene) NPs/MPs was investigated after low-pressure direct surface plasma polymerization of acrylic acid. The amount of NPs/MPs in the feed, retentate and permeate was measured with Nanoparticle Tracking Analysis to monitor the antifouling properties of the surface-enhanced membranes. Filtration performance such as water flux and rejection rate were correlated to the roughness, surface charge and hydrophilicity of the modified membrane. After 48h of filtration, water flux only decreased from 150 L/h/m2 to 117 L/h/m2 instead of 81 L/h/m2 without plasma treatment, with a flux recovery ratio of 87% after cleaning and a NPs/MPs rejection rate of 80%. The plasma deposited acrylic acid layer increased the hydrophilicity of the membrane and decreased its surface charge density from -7 mV to -54 mV, resulting in a reduction of NPs/MPs fouling.

Addressing nano/microplastics fouling on filtration membranes by surface plasma treatment

2019 Fall National Meeting

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