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Membrane Arrangements
Depending on the shape and material of the membrane, different modules can be used for ultrafiltration process (Futselaar). Commercially available designs in ultrafiltration modules vary according to the required hydrodynamic and economical constraints as well as the mechanical stability of the system under particular operating pressures (Belfort). The main modules used in industry include:

Tubular Modules: The tubular module design uses polymeric membranes cast on the inside of plastic or porous paper components with diameters typically in the range of 5 – 25 mm with lengths from 0.6 -6.4 m [tamime]. Multiple tubes are housed in a PVC or steel shell. The feed of the module is passed through the tubes, accommodating radial transfer of permeate to the shell side. This design allows for easy cleaning however the main drawback is its low permeability, high volume hold-up within the membrane and low packing density (Belfort, Tamime).

Hollow Fibre: This design is conceptually similar to the tubular module with a shell and tube arrangement. A single module can consist of 50 to thousands of hollow fibres and therefore are self-supporting unlike the tubular design. The diameter of each fibre ranges from 0.2 – 3 mm with the feed flowing in the tube and the product permeate collected radially on the outside. The advantage of having self-supporting membranes as is the ease at which it can be cleaned due to its ability to be backflushed. Replacement costs however are high, as one faulty fibre will require the whole bundle to be replaced. Considering the tubes are of small diameter, using this design also makes the system prone to blockage. (Cheryan).

Spiral-wound modules: Are composed of a combination of flat membrane sheets separated by a thin meshed spacer material which serves as a porous plastic screen support. These sheets are rolled around a central perforated tube and fitted into a tubular steel pressure vessel casing. The feed solution passes over the membrane surface and the permeate spirals into the central collection tube. Spiral-wound modules are a compact and cheap alternative in ultrafiltration design, offer a high volumetric throughput and can also be easily cleaned (Belfort). However it is limited by the thin channels where feed solutions with suspended solids can result in partial blockage of the membrane pores (Cheryan).

Plate and Frame: This uses a membrane placed on a flat plate separated by a mesh like material. The feed is passed through the system from which permeate is separated and collected from the edge of the plate. Channel length can range from 10 – 60 cm and channel heights from 0.5 – 1 mm (Cheryan). This module provides low volume hold-up, relatively easy replacement of the membrane and the ability to feed viscous solutions because of the low channel height, unique to this particular design (Belfort).