Membranes and separation materials enable the removal of suspended solids, dissolved salts, microorganisms, organic compounds and trace contaminants from water. The category includes reverse-osmosis, nanofiltration, ultrafiltration, microfiltration, ion-exchange membranes, ceramic membranes, hollow-fibre modules, adsorbents and specialty filtration media. These technologies are used in desalination, drinking-water production, industrial wastewater treatment, ultrapure-water systems and water-reuse facilities. Performance depends on permeability, selectivity, fouling resistance, chemical compatibility, operating pressure and membrane life. Manufacturers are advancing low-energy membranes, anti-fouling surfaces, modular filtration systems and materials designed for emerging-contaminant removal. Research coverage assesses technology development, capacity additions, raw-material trends, supplier positioning, end-use demand and opportunities across PFAS treatment, high-recovery desalination and closed-loop industrial water systems.