Water purification
Water purification is the process of removing contaminants from water to make it safe for various uses, particularly human consumption. This essential practice involves different techniques tailored to the specific requirements of the water's end use, as drinking water, for instance, necessitates more thorough purification compared to water used for industrial purposes. Sources of water include natural bodies like rivers and lakes, as well as underground aquifers and artificial reservoirs. Contaminants can range from natural sediments and bacteria to chemicals from agricultural and industrial activities.
Natural water purification occurs through ecosystems, where microorganisms and vegetation filter out harmful substances. For example, wetlands are highly effective at removing sediment and nutrients, thereby protecting larger water bodies from pollution. In developed countries, municipal water undergoes rigorous purification methods, including filtration and chlorination, to eliminate impurities and pathogens. Advanced techniques such as reverse osmosis and UV treatment are also used, particularly in industrial or medical settings. Additionally, individuals may use home purification systems to address specific contaminants or enhance water quality. In emergency situations, methods like boiling and chemical treatment can provide immediate purification solutions. Understanding these processes is crucial for ensuring access to clean water, a vital resource for health and well-being.
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Water purification
Water purification is the process of removing sediment, microorganisms, and other contaminants from water supply sources. Nature provides a few forms of natural water purification. Other processes are used to purify water for commercial, community, and home use. These processes may be customized to remove more or fewer contaminants, depending on the end use of the water supply. For example, drinking water requires greater purification than water used for commercial laundry purposes, while certain medical uses require even more purification.
Background
Water comes from many sources—rainwater, streams, lakes, reservoirs, underground aquifers, and more. Its various forms include liquid (water), gas (steam), and solid (ice). Water is a solvent, which means that it can dissolve many substances, such as dirt, bacteria, or chemicals. To ensure that water is safe for drinking and other uses, it is necessary to purify it.
Contaminants found in water include silt and natural materials that find their way into streams, rivers, and other bodies of water; bacteria and other microorganisms and their by-products; inorganic chemicals and their remnants from industrial, commercial, and agricultural sources, such as insecticides, processing chemicals from manufacturers, and wastewater from factories; and organic elements, such as fertilizers, animal waste, and decaying plant life.
Overview
Different ecosystems often have natural processes that contribute to the purification of water. For example, while some microorganisms in water present a health hazard, such as the parasitic organisms that cause giardia, other microorganisms help to remove contaminants. Certain microorganisms, for example, can remove both natural contaminants and contaminants from metals and chemicals.
Plant life near water sources may play a key role in natural water purification. Forests that grow along streams and lakes—called riparian forests—prevent some contaminant-laden runoff from reaching water sources. Such plants are especially important in filtering out contaminants from fertilizers used in agriculture, which can affect levels of nitrogen and phosphorus in water sources. Forestland can also minimize the impact of contaminants picked up by floodwaters by preventing some of them from being carried back to rivers, streams, or lakes.
Wetlands, or areas where soil is covered or heavily soaked with water, provide some of the best natural water purification. Because of the specialized types of plants that grow in this water-logged environment, wetlands are known to remove as much as 90 percent of sediment and nitrogen and up to 60 percent of metals from the waters that enter them. As a result, these contaminants are prevented from entering other sources that supply water.
These natural systems can be impaired by excessive runoff resulting from too much development of neighboring lands; from pollution, such as garbage or industrial waste that is dumped in or near the wetlands or forests or directly into water sources; and by excessive use or incorrect disposal of fertilizers.
In developed countries, all water from municipal water supplies that is intended for human use is purified in one of several ways. Such water may come from natural sources, such as rivers and lakes; underground aquifers (rocky or sandy areas filled with water); or reservoirs, which are artificial lakes made to store water. Water from these sources may be filtered, distilled, deionized, radiated, sanitized, or treated in other ways to remove contaminants that affect the appearance, taste, and safety of the water before it is delivered to homes and businesses for human consumption.
The first step in the purification process is usually filtration. During filtration, water passes through a series of beds and tanks containing materials that help to remove debris, such as dirt and leaves, from the water. The water also may stand in a sedimentation tank to allow heavier debris to settle to the bottom for removal.
After filtering, the water is sanitized. Water may be sanitized in several ways—for example, by heating it or sanitizing it with chemicals. The most common way is to treat it with chlorine. Chlorine is effective at killing a variety of dangerous microorganisms, including those that cause contagious diseases such as cholera and typhus.
In most cases, filtering and chlorinating are enough to sufficiently treat water for normal human consumption. In some instances, however, other purification techniques may be applied. Reverse osmosis uses special membranes and pressure to force more contaminants out of the water. Ultrafiltration uses a membrane with very fine holes to provide a greater level of filtration than standard filtering screens. Treating the water with ultraviolet light helps to break down and render harmless any organic contaminants, while ion exchange and electrodeionization (EDI) technologies use special resins to remove ions that are attracted to harmful contaminants. These specialized treatments are most often used in industrial, pharmaceutical, and medical environments.
In addition to the purification systems provided as part of municipal water systems, some people use home water purification systems. For example, a home with a private well needs its own system to remove impurities. In other cases, people simply want a system to remove contaminants that are not necessarily dangerous but are unpleasant or a nuisance. For example, some people attach water filters to faucets or main water lines or use pitchers with water filters in them to remove the chlorine taste that sometimes results from municipal water purification. Similar home systems can minimize the presence of dissolved minerals that can leave deposits on pipes, water heaters, toilets, and other devices that use or transport water. In most cases, these water filtration systems use carbon and other materials to remove the contaminants. However, some systems apply other technologies, such as deionization.
People also may be interested in personal water purification for emergency situations. For example, in an emergency situation such as a water main break, people may boil water, treat it with iodine or chlorine, or filter it to make it safe to drink. Such techniques may be employed during natural disasters or when one is in the wilderness for an extended period without access to purified water.
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