hey filter out all the contaminants and particles from the feed water source once it has passed through pretreatment. Crossflow membrane filtration is a pressure-driven separation process. Application: Industrial, food, water, chemical, and biotechnology markets, as well as for those providing environmental protection. RO membranes are great solutions for many different applications. Membranes serve as highly-engineered, physical barriers that permit the passage of materials only up to a certain size, shape or character. Puritech offers reverse osmosis membranes (RO membranes), Filmtec membranes or Dow Filmtec membranes, Koch membranes, and Hydranautics membranes in a variety of configurations, materials and sizes; each designed to meet specific application needs. Puritech also stocks their brand of spiral membranes.