How is water made drinkable?
There are several reasons people might not receive water that meets EPA or other cleanliness standards. Pipes that supply water to homes can be old and can leak impurities, and some water treatment plants might not meet the necessary standards for water quality. Consumers can check this by asking their local plant for a report on water quality. They can also access an online database, such as the one created and maintained by the Environmental Working Group (EWG) that analyzes the quality of water in different communities. The EWG is a nonprofit that collects data related to health issues and makes them more accessible to the public.
Research conducted by the EWG shows that there are 300 contaminants present in drinking water for which the government has set no limits. In addition, the water supply for around 50 million Americans doesn’t meet the standards set by the EPA because of an excess of at least one pollutant. Statistics like these could be the reason for the growing popularity of home filtration systems.
More than 40 percent of Americans now use a personal water filtration system, according to the EPA. Home filtration systems come in several types and use many different methods. Most of the cheapest systems available are carbon filters. The carbon in these filters traps most contaminants and only lets water and minute impurities through. One of the downsides of using these systems is the users need to make sure they replace the carbon filter regularly to ensure maximum effectiveness.
http://thetartan.org/2011/10/31/scitech/htw
NSA Water Filters