Ultrafiltration (UF) is classified as a membrane process. It is a method of water filtration in which particles are separated as the solution passes through a barrier - membrane. Membranes with a pore size of 0.1 – 0.01 µm are described as ultrafiltration. The driving force is the hydrostatic pressure difference. The inlet water is separated at the membrane into a retentate, which remains at the inlet, and a permeate product, which passes through the membrane. This is a simple physical separation where particles larger than the pore size of the membrane (suspended solids, bacteria, viruses) are retained on the membrane surface. Thus, not only filtration takes place, but also the removal of unwanted microorganisms - disinfection.
In terms of operation, ultrafiltration modules are designed as submersible modules, mostly plate and frame modules, while tubular, hollow fibre and spiral wound modules are mainly for pressure filtration. For pressure filtration, the modules can be operated in dead end or cross flow mode. In "dead end" mode, all water flows through the membrane and impurities are trapped on the membrane surface. In "cross flow" mode, raw water flows along the membrane and only the permeate is pushed through the membrane while the concentrate carries the impurities to the waste. Generally speaking, the "dead end" process is advantageous for less polluted waters and with increasing pollution it is advisable to switch to the "cross flow" mode. However, “dead end” filtration is more advantageous in terms of operating costs as less water is pumped and the system yield tends to be much higher.
Ultrafiltration is particularly suitable for the treatment of process water, as a precursor to reverse osmosis, or for the treatment of drinking water. In wastewater treatment, ultrafiltration is mainly used in membrane bioreactors.
Benefits
- Absolute barrier to suspended solids, bacteria and viruses
- Filter quality independent of raw water quality, even in the event of significant variations in water composition
- Best possible pretreatment for reverse osmosis, nanofiltration
- Removal of chlorine-resistant pathogenic organisms
- Low chemical consumption
- Low sludge production
- Compact design and smaller footprint
- Fully automatic, autonomous operation
Parameters
- Pore size 0.01-0.1 µm
- Membrane loading up to 200 LMH
- Operating pressure 0.3-5 bar
