Ultrafiltration

Ultrafiltration is used to remove floating substances, bacteria, fibres... and can also be used as pretreatment for reverse osmosis installations or for biological water treatment (MBR). The pores have an opening of approximately 0.02 µm. Given this pore size, ultrafiltration will have no influence on the ion balance.

Ultrafiltration installations can consist of 2 types: dead-end and cross-flow UF.

In case of dead-end ultrafiltration all the water is pumped through the membrane and the pollution stays on the membrane surface as a result. To remove any residues remaining on the membrane regular counter-rinsing is needed. Such an ultrafiltration can handle a pollutant load up to about 300 mg/l.

In case of a cross-flow UF, only the filtrate water will go through the membrane, while the largest part of the incoming water flow goes past the membrane and is therefore pumped over the membrane in a closed loop. Thanks to this large rinse stream, the pollution on the membrane is also transported, so no counter-rinsing is required. These installations can therefore handle larger dirt loads.

A dead-end-filtration usually has a much higher flux than a cross-flow unit. Because the cross-flow solution also requires a high circulation flow rate, this technology is less energy efficient than the dead-end technology.

On the other hand, the cross-flow solution is less sensitive than the dead-end solution.

A cross-flow solution is among others used in MBR (sludge removal in biological treatment), purification of process fluids and others.

A dead-end filtration is often used as a pretreatment for RO, to purify surface water (river water), to purify rainwater and others.

When dimensioning a UF unit, it is advisable to perform a test with a pilot unit. PCA can provide such a pilot unit and monitor and interpret the tests.

PCA can help you with these technologies, both in design and construction of the installation.