A membrane is a thin, semi-permeable layer of material that will only allow certain compounds to pass through it. There are many different types of membrane filters available in a wide range of pore sizes and configurations for a wide range of applications.
Desalination of salt water to produce potable water remains the primary use of membrane filtration. However, membranes can also be used for many different types of filtration applications; most of them are not related to potable water production. For example, they are used in industry to produce high purity process water or to remove contaminants from waste streams prior to discharge.
Membranes are used to remove undesirable constituents from the water. If these constituents are dissolved in the water, very tight membranes are required; if the constituents are particulates, then a looser membrane is appropriate.
- Membrane filters are used to remove microbiological contaminants. Even the loosest membrane will remove Giardia cysts and Cryptosporidium cysts. If virus removal is desired in addition to the removal of Giardia and Cryptosporidium, a slightly tighter membrane is used.
- Membrane filters are used to remove organic compounds. The nature of the compound will determine whether it can be removed by a particular level of membrane filtration.
- Membrane filters are used to remove both dissolved and particulate inorganic substances. The nature of the substance will determine the level of tightness that is required to remove it.