Water scarcity, tighter regulations, and emerging contaminants like PFAS (per- and polyfluoroalkyl substances) are putting communities and industries under pressure worldwide. Membrane filtration is one of the key technologies for addressing these challenges, and the membrane technology market is growing to match. According to Global Water Intelligence, global desalination capacity has grown 40 percent since 2020, and water recycling capacity has grown by as much as 52 percent¹. This trend shows that processes like reverse osmosis (RO) and ultrafiltration (UF) are becoming increasingly important for drinking water, process water, and water reuse.

Membrane filtration is a separation process in which a membrane acts as a selective barrier: it lets certain components of a water or process stream pass through while holding others back. Membrane function is based on selective separation, allowing certain substances to pass through the membrane while retaining others depending on membrane characteristics. A few related terms often get used interchangeably: a membrane process refers to the application of membrane-based separation techniques, while membrane separation refers to the selective separation achieved by the membrane. Membrane technology is the umbrella term for all applications in which membranes are used to treat water or process fluids. Institutions worldwide, including the World Health Organization (WHO), emphasize the importance of reliable water treatment for ensuring drinking water quality².

Individual membranes aren't operated in isolation; they're grouped into membrane systems (also called filtration systems): modules bundle numerous membrane elements – such as hollow-fiber, flat-sheet, or spiral-wound designs – into compact units with a defined active filter area. Several modules are then combined into skids – pre-assembled units that include not just the membrane modules but also the frame structure, piping, instrumentation, and often the system controls, and that can be integrated as a whole into existing plants with relative ease. Individual components thus come together into complete membrane systems that can be configured, depending on requirements, with multiple treatment stages to achieve specific treatment objectives.

Several operating factors are critical to the performance of such systems: operating pressure has to be matched to the specific application, and flux – the permeate flow rate per membrane area – mainly determines throughput and energy consumption. Fouling can significantly reduce performance and increase energy demand, as independent research on fouling mechanisms in reverse osmosis membranes shows³. Fouling mostly refers to the deposit of substances on the membrane surface, which, depending on the cause, shows up as particulate fouling, biological fouling (biofilm formation), organic fouling, or scaling from inorganic deposits such as calcium and magnesium salts. Regular cleaning cycles are therefore essential to limit the effects of fouling and extend membrane life. That's exactly why getting the membrane system design right from the start is so critical: it influences not just initial performance but, crucially, the total cost of ownership (TCO) over the system's entire service life.

Where particles, microorganisms, or macromolecules are the focus, ultrafiltration technology is often sufficient. Where dissolved salts or low-molecular-weight contaminants need to be removed, reverse osmosis technology is often the preferred solution. In practice, the two membrane processes aren't mutually exclusive – they complement each other: ultrafiltration often handles pretreatment, while reverse osmosis provides advanced purification. Water quality, treatment goal, target recovery rate, and operational constraints are the key selection criteria.

Membrane filtration is drawing growing attention as part of a more sustainable approach to water management. Through the EU Drinking Water Directive, the European Commission is pursuing stricter quality standards for public water supply⁴ and is addressing PFAS contamination through its own policy measures⁵. The UNESCO World Water Development Report also underscores how critical efficient treatment and reuse technologies are to global water security⁶, while UN-Water points to growing water scarcity worldwide⁷. In this context, membrane technology and its applications make a decisive contribution to the circular economy: it enables water reuse, resource recovery, and compliance with growing regulatory requirements – making it a central tool for the water and process challenges of today and tomorrow.