More stringent water quality standards have led to an increase in demand for efficient membrane filtration technologies, like nanofiltration. Nanofiltration is sometimes used to recycle wastewater, as it offers higher flux rates and uses less energy than a reverse osmosis system.
The design and operation of nanofiltration is very similar to that of reverse osmosis, with some differences. 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 a 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". Nanofiltration is often used to filter water with low amounts of total dissolved solids, to remove organic matter and soften water.
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. Nanofiltration can be employed in a variety of water and wastewater treatment industries for the cost-effective removal of ions and organic substances.
Besides water treatment, nanofiltration is often employed in the manufacturing process for pharmacetuicals, dairy products, textiles and bakeries. The WaterProfessionals® have considerable experience in applying nanofiltration systems to solve water treatment problems.