Filtration-based reduction of surfactants and fiber-derived micro/nanoplastics from domestic laundry wastewater

Household laundry wastewater (LWW) is a significant yet often overlooked source of micro- and nanoplastic pollution, in addition to its substantial organic load originating from surfactants. Beyond being a waste stream, LWW represents a critical opportunity for source-level intervention, as it combines high water consumption with the release of persistent textile-derived pollutants. This study examines the concurrent behavior and attenuation of synthetic microfibers and anionic surfactants in real domestic laundry wastewater using two membrane-based strategies: sequential filtration (60 → 5 → 0.1 µm) and single-step microfiltration (0.45 µm). Laundry wastewater was generated under realistic washing conditions and characterized using total organic carbon (TOC), chemical oxygen demand (COD), turbidity, anionic surfactants (ANS), total suspended solids (TSS), and particle size distribution (PSD). Comparative evaluation of detergent-only, textile-only, and combined matrices enabled a mechanistic assessment of fiber-surfactant interactions and size-dependent removal behavior. The results indicate that both filtration strategies effectively reduce microfibers and surfactant-associated organic matter. In fiber-rich matrices, 0.45 µm membranes achieved COD and TOC reductions comparable to those obtained with 0.1 µm membrane filtration, likely reflecting secondary retention effects associated with microfiber deposition during filtration. In contrast, detergent-only systems relied predominantly on physical size exclusion, requiring finer cutoffs to enhance removal performance. PSD analysis consistently revealed a persistent sub-100 nm particulate fraction across all matrices, likely comprising fiber-derived nanoplastic-like particles together with surfactant-stabilized colloids that remained largely resistant to conventional microfiltration. Overall, the findings demonstrate that membrane filtration coupled with PSD analysis can serve not only as a low-energy pretreatment option but also as a diagnostic tool for elucidating interactions among microfibers, nanoplastic-sized particles, and surfactants, thereby supporting decentralized greywater reuse and circular water management strategies.