By ultra filtration – similar to micro filtration - mainly macro molecules und small particles as well as suspensions and emulsions are separated. The passages between micro filtration and ultra filtration are fluent: Membranes of a pore size between 0,1µm and a few µm are associated with micro filtration, membranes of a pore size between 0,01µm and 0,1µm are associated with ultra filtration. The working pressure of ultra filtration is 0,5 bar (approx. 7 PSI) to 10 bar (approx. 145 PSI).
The separation effect of the ultra filtration is based mainly on sieve effects, i.e. particles with a diameter bigger than the average pore size of the membrane are retained. Additionally, also effects of solubility and diffusion are of importance.
Depending on the application, various module designs are suitable. The most common designs are spiral wound modules, tubular modules as polymeric or ceramic element, plate modules, capillary modules and hollow fiber modules. These designs are distinguished from each other by the hydraulic diameter and the related specific package density.
Field of applications of ultra filtration
- Separation of particles, e.g. for conditioning of surface water or as pre-treatment of an reverse osmosis plant
- Separation of activated sludge – Membrane bio reactor (MBR)
- Pre-concentration of suspensions
- Separation of organic molecules
- Separation of endotoxins and pyrogenics or degermination for pharmaceutical applications
- Recovery of dyes at paper industries
- Degreasing bath conditioning
- Concentration of electrodeposition paint
- Concentration of water-soluble dyes and lacquers
- Conditioning of surface water