Nanofiltration

The design and operation of nanofiltration is very similar to that of reverse osmosis. The major difference is that the nano membrane is not as "tight" as the reverse osmosis membrane, it operates at a lower feedwater pressure and it does not remove monovalent (i.e., those with a single charge or valence of one) ions from the water as effectively as the RO membrane. While the RO membrane will typically remove 98-99% of monovalent ions such as chlorides or sodium, a nanofiltration membrane typically removes 50% to 90%, depending on the material and manufacture of the membrane. Because of its ability to effectively remove di and trivalent ions, nanofiltration is frequently used to remove hardness from water while leaving the total dissolved solids content much less affected than would RO. For this reason it has been called the "softening membrane".

Because it is a "looser membrane", nanofiltration membranes are less likely to foul or scale and require less pretreatment than RO. Sometimes it is even used as pretreatment to RO. Besides water treatment, nanofiltration is often employed in the manufacturing process for drugs, dairy products, textiles and bakeries.

The WaterProfessionals® have considerable experience in applying nanofiltration systems to solve water treatment problems.

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