Life Cycle Assessment of Microplastic Fouling Mitigation Strategies in Membrane Filtration

While membrane technologies are critical for preventing microplastics (MPs) release into aquatic ecosystems, MPs-induced fouling remains a persistent bottleneck, necessitating energy-intensive cleaning strategies that introduce their own environmental burdens. This study presents a systematic life cycle assessment (LCA) of fouling mitigation strategies, rigorously comparing hydraulic forward flushing and nitrogen (N₂) gas scouring across both unmodified and plasma-modified (acrylic acid, cyclopropylamine, and hexamethyldisiloxane) polysulfone membranes. Results reveal a stark divergence between operational performance and environmental sustainability. Baseline operations and the hydraulic flushing of unmodified membranes have environmentally costly global warming potential (GWP) ~150 kg CO₂-eq/m³), driven primarily by high electricity consumption and frequent membrane replacement. Conversely, cyclopropylamine (CPAm) plasma-modified membranes emerging as the optimal strategy, reducing global warming potential to 68 kg CO₂-eq/m³ and cutting electricity demand by 44% through superior fouling resistance. Crucially, the study uncovers a significant trade-off regarding gas scouring: While it achieves the highest technical performance (minimal flux decline of 0.33% h^-1), the upstream burdens of N₂ supply increased environmental impacts by over 100% across all categories. These findings challenge the assumption that maximum fouling control equates to sustainability, suggesting that surface engineering via plasma modification, rather than aggressive physical cleaning, offers the most viable pathway for sustainable MPs remediation.