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Nanofiltration – General

Nanofiltration (“NF”) is a relatively new membrane filtration process. Similar to Ultrafiltration, separation is achieved based on “size exclusion”. A liquid is forced through a semipermeable membrane with pores in the range of 1 -10 nanometers through the application of pressure. A wide range of contaminants is retained, while water and low molecular weight solutes pass through the membrane in the permeate or filtrate. Due to the smaller pore size, NF can typically filter out much smaller particles than UF membranes; including some dissolved particles such as certain types of salts or dyes.

NF has typically been based on using flat sheet membranes. The disadvantage to flat sheet (or spirally wound) membranes is that they still require a relatively high operating pressure, often around 5 bar or more, and are more complicated to clean and maintain.

NF has applications in potable water and waste water treatment. The technology is also becoming more widely used in food processing applications such as dairy production, i.e. to concentrate liquids.

De.mem’s Nanofiltration technology: Taking Nanofiltration to the Hollow Fibre Format

De.mem has access to a new NF membrane technology which is based on a membrane in the hollow fibre format. This allows to operate the membrane under low pressure of approx. 1.5 – 2 bar. The low operating pressure results in substantial savings in power consumption, compared to the use of traditional flat sheet NF membranes or even Reverse Osmosis (RO) membranes. Furthermore, hollow fibre membranes are typically easier to operate and clean compared to flat sheet membranes.

Capital expenditure is also reduced, as the system architecture s generally much simpler i.e. there is no need for expensive components such as high pressure pumps.

The filtration process works as follows: Hollow fiber membrane bundles are placed in the inside of so-called membrane modules. The water is then pumped inside these modules. As pressure is applied, clean water passes through the pores of the selective layer of the membrane. The contaminants remain outside. The clean water then leaves the modules. In a regular and simple backflush routine, the dirt is cleaned out of the modules.

De.mem produces its hollow fibre NF membranes at its production facility in Singapore.

Worldwide Leader in Hollow Fiber Nanofiltration

Hollow-fibre NF is unique in the water treatment industry with only very few companies worldwide offering similar products. De.mem considers itself at the forefront of such and a worldwide leader in hollow-fibre Nanofiltration, or the production of hollow-fibre membranes with a tight pore size.