Nanofiltration is a filtration process in which a fluid is encouraged to pass over a membrane which acts almost like a sieve to separate out impurities. The membrane blocks impurities in the fluid, allowing only the fluid and certain monovalent ions to pass through while trapping undesirable materials on the other side. There are a number of applications for nanofiltration, ranging from purifying dairy products to processing drinking water, and a number of companies manufacture nanofiltration equipment and supplies.
In this process, a pressure differential is created between the two sides of the membrane which encourages the impure, unfiltered substance to force its way through the membrane. A variety of materials can be used to make the membrane, depending on what is being filtered out. As the fluid pushes against the membrane, particles which are too big to pass through it will bounce off. The purified fluid on the other side can be collected and further processed, released, or packaged, depending on what it is and how it is being used.
This type of filtration can be used to address pollution in water supplies, chemical spills, impurities in drinking water and other fluids humans consume, and in desalination. The development of effective desalination techniques is of interest to people in many regions of the world as water shortages are a critical problem, and the ability to provide water for drinking or irrigation from saline sources can be very valuable.
In addition to being used on an industrial scale, nanofiltration can also be employed by individuals. Drinking filters designed for use by campers who want to drink from natural water sources rather than packing water out to a campsite may be made with nanofiltration filters in place, and people can also use this type of filtration to process the drinking water in their homes, or to power a whole-house filter which is designed to remove any lingering impurities in water before it reaches home plumbing.
Only very small molecules can pass through a nanofiltration device. The filters usually have pores which are around .001 microns thick, although the thickness can vary depending on the design. Like other membrane style filters, a nanofilter will need to be periodically removed and cleaned or exchanged for a fresh filter, as the pores in the filter become clogged over time, slowing down and eventually blocking the filtration process altogether. Replacement filters are usually readily available.
