Nanoplastics in water and wastewater: remediation technologies, challenges, and future perspectives

Nanoplastics (NPs) are emerging contaminants of increasing concern in aquatic environments because their small size, colloidal behavior, and surface reactivity complicate their detection and remediation. This review critically evaluates physical, physicochemical, biological, and hybrid technologies for NP remediation in water and wastewater, focusing on treatment mechanisms and endpoints, analytical evidence, matrix-dependent performance, practical applicability, and sustainability. An evidence-based treatment-endpoint framework is applied to distinguish capture/separation, aggregation followed by separation, fragmentation, degradation, and mineralization rather than comparing technologies solely on the basis of reported removal efficiencies. Current evidence indicates that membrane filtration, coagulation/flocculation, and adsorption can achieve substantial aqueous-phase removal under suitable conditions but predominantly transfer NPs to membranes, sludge, concentrates, or spent adsorbents rather than destroying the polymer. Advanced oxidation processes can promote polymer degradation and, under appropriate conditions, mineralization; however, their performance depends on reaction conditions, water-matrix characteristics, resource requirements, and the analytical evidence supporting the treatment endpoint. Biological approaches may offer lower-input alternatives but remain constrained by slow kinetics, polymer specificity, and limited evidence of extensive degradation. Hybrid systems can integrate particle capture and degradation, although their complexity may limit large-scale implementation. Major barriers include inconsistent treatment endpoints, incomplete NP mass balances, reliance on pristine particles and simplified matrices, analytical limitations, secondary-residual generation, and limited pilot-scale validation. Future research should prioritize real water matrices, environmentally relevant and aged NPs, complementary analytical methods, mass-balance verification, and systematic evaluation of energy demand, chemical consumption, residual management, cost, scalability, and life-cycle impacts to distinguish apparent removal from effective and sustainable remediation.