Four types of membrane modules are available in the marketplace: plate and frame, tubular, spiral-wound and hollow-fiber. The spiral-wound module occupies the largest market share because of its relative ease of cleaning, fabrication technology and very large surface area per unit volume. When compared with the hollow-fiber module in terms of the method of fabrication and cost, the spiral wound is the best. The flow of feed and permeate in a spiral-wound module is shown in Fig. 4. A typical spiral-wound module may have a packing density of 250 m2/m3. The flow channel size is on the order of 0.05 cm. The continuous change of flow in the spiral-wound module allows good mixing of the feed solution.
Plate and Frame Module
Hollow Fibre Module
Tubular Module
Spiral-wound Module
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