available modules – their geometry

The individual separation appliances, designated «modules», or often «elements» in the case of spiral-wound modules, use membranes that have been designed with a view to satisfying two main objectives :

• ensuring that, at membrane level, there is an adequate circulation of liquid to be treated in order to restrict concentration polarisation phenomena (desalination membranes) and also particle deposits (clarification membranes);
• producing a compact module, i.e. one that has a maximum exchange surface area per unit of volume.

These two objectives help to reduce the cost of the modules required to produce a given volume of treated liquid.

It must be :

• easily backwashed, hydraulically flushed and chemically washed and/or disinfected or even sterilised …;
• easy to assemble/disassemble …;
• having the option to automate production lines …

Four major types of module are available on the market: tubular, hollow-fibre, plate-type and spiral-wound; however, in water treatment applications, 95% of MF or UF plants are made of «hollow fibre» modules and the same proportion of spiral-wound modules are used in NF or RO applications.