Water filtration is an important part of the treatment process. A water filter removes impurities from water by means of a fine physical barrier, a chemical process or a biological process. Filters use sieving, adsorption, ion exchanges, and other processes to remove impurities. Unlike a sieve or screen, a filter can remove particles much smaller than the holes through which the water passes. Modern-day treatment plants use various types of filters, from media and screen filters to disk filters, slow or rapid sand filters, and cloth filters. There are myriad filtration options for point-of-use, or domestic, filters as well, ranging from the common GAC method, to metallic alloy filters, ceramic filters, carbon
block resin, and many others. Point-of-use filters may be as simple as a water pitcher, a refrigerator filter, or a tap filter, and they may be more complicated, as with a whole-house filtration system.
Industrial water treatment in the early 19th century relied primarily on sand filters. While there were many small-scale water filtration systems prior to 1800, Paisley, Scotland is generally acknowledged as the first city to receive filtered water for an entire town. The Paisley filter began operation in 1804 and was an early type of slow sand filter. Throughout the 1800s, hundreds of slow sand filters were constructed in the UK and on the European continent. On the American front, the first continuously operating slow sand filter was designed for the city of Albany, New York in 1897.
The first documented use of a domestic water filter is credited to Hippocrates, circa 500 BC. Because nothing was known about microorganisms or chemical contaminants (which would remain undiscovered until the 17th century), the motive for treating water was simply to make it smell and taste better. The Greek scientist Hippocrates was among the first to believe that diseases occurred as a result of the natural world, and sought to limit their effect. He also believed that if water tasted and smelled clean, it must be healthful for the body. This belief led to a cloth bag filter, called the “Hippocratic sleeve.”
Whether at a treatment plant or in a home, filtration is a necessary step towards maintaining a clean water supply. With the modern advances in filtration options, society is no longer limited to one or two options for their filtration, which leads to newer and more effective filtration discoveries. Where will our filtration options be 100 years from now? Or 1,000 years?