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Common Processes of Water Purification

Water is essential for life, so the widespread pollution of raw water sources poses a problem for everyone. Almost all drinking water requires some type of purification, whether it comes from the municipal water supply through your taps, in bottles or is purified at home. There are several processes commonly used to purify water, including ultrafiltration, carbon adsorption, disinfection and reverse osmosis. Many at-home water purification systems use a combination of these methods.

  1. Ultrafiltration

    • Ultrafiltration uses a very fine, tough and somewhat permeable membrane to filter out particles at a molecular level. The smallest molecules can slip through the membrane, but the larger particles are trapped above the membrane. Ultrafiltration removes almost all types of contaminants, including heavy metals, foreign particles and pathogens like cryptosporidium. It is an effective means of water filtration that requires the least amount of energy output. The process cannot filter out chlorine or fluoride, which some people don't want in their drinking water.

    Carbon adsorption

    • Carbon adsorption uses activated carbon, created under high temperatures to form microscope pores, to filter out contaminants. Carbon filtering works well to remove chemicals like chlorine or unpleasant tastes and smells. Some carbon filters are fine enough to filter out microorganisms, and a few are capable of removing pesticides, lead and other heavy metals, along with PCBs (polychlorinated biphenyls), a banned toxic substance that still circulates in some water sources.

    Disinfection

    • Disinfection is most often used for municipal water supplies. Chlorine-based products are most commonly used. Chlorine is effective at killing microbes and pathogens, but some people object to the taste and smell. It is also effective at disinfecting the pipes that bring water to homes. Ultraviolet radiation or ozone might also be used as a means of disinfection, but neither effectively kills microorganisms.

    Reverse Osmosis

    • Reverse osmosis utilizes a semi-permeable membrane, similarly to ultrafiltration. It is more effective, because water is forced through the membrane at a high rate of pressure to remove more and smaller particles. Reverse osmosis removes up to 99 percent of all types of contaminants, including radiated particles like plutonium. The membrane is so restrictive that it takes a while for the water to flow through, making reverse osmosis slower than other purification methods.

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