纳米过滤器

纳米过滤的设计和运作是反渗透过滤十分相似。主要的区别在于纳米膜是没有反渗透膜那么紧，它在较低的给水压力下工作，不会删除水中的单价离子，与反渗透膜效率差不多。反渗透膜通常会去除98-99%的单价离子，如氯或钠离子，而纳米膜通常会去除50％至90％的单价离子，这取决于膜的材料和生产方法。因为纳米膜能够有效地消除三价离子，它经常用于去除水中的硬度物质，同时相比反渗透膜来说，对总的溶解固体含量的影响也不大。

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".