Drinking water is essential for human health and well-being, but it can also be contaminated by various types of pollutants. Some of the common contaminants that may exist in drinking water are:
- Physical,
- Chemical,
- Biological
- and radiological.
These contaminants can affect the quality, taste, odor and safety of the water, and may pose serious health risks to the consumers.
Contaminants in drinking water
Physical contaminants
Physical contaminants are substances that change the physical properties of water, such as its color, turbidity, temperature or viscosity. They can be caused by natural processes, such as soil erosion, or human activities, such as industrial discharge or agricultural runoff. Examples of physical contaminants are sediment, organic matter, algae, oil and grease.
Chemical contaminants
Chemical contaminants are elements or compounds that are either naturally occurring or man-made. They can be dissolved or suspended in water, and may have toxic, carcinogenic, mutagenic or endocrine-disrupting effects. Some examples of chemical contaminants are nitrogen, phosphorus, chlorine, fluoride, arsenic, lead, mercury, pesticides, herbicides, pharmaceuticals and personal care products.
Biological contaminants
Biological contaminants are microorganisms that can cause infections or diseases in humans or animals. They can be bacteria, viruses, protozoa, parasites or fungi. They can enter the water sources through fecal contamination from humans or animals, sewage overflow, storm water runoff or animal carcasses. Important examples of biological contaminants are Escherichia coli, Salmonella, Vibrio cholerae, hepatitis A virus, rotavirus, Giardia lamblia, Cryptosporidium parvum and Ascaris lumbricoides.
Radiological contaminants
Radiological contaminants are radioactive substances that emit ionizing radiation. They can be naturally occurring or man-made. They can cause damage to the cells and DNA of living organisms, and may increase the risk of cancer or genetic mutations. Examples of radiological contaminants are radon, uranium, cesium and plutonium.
Method to remove contaminants form water
To remove these contaminants from drinking water, various treatment techniques can be applied at different stages of the water supply system. Some of the common treatment techniques are:
– Coagulation and flocculation: This process involves adding chemicals to the water to make the suspended particles clump together and form larger particles called flocs. The flocs then settle at the bottom of the tank or are removed by filtration.
– Sedimentation: This process involves letting the water sit in a tank or a basin for a period of time to allow the heavier particles to settle at the bottom. The clear water is then drawn from the top.
– Filtration: This process involves passing the water through a porous material that traps the particles and some microorganisms. The filter material can be sand, gravel, activated carbon or membrane.
– Disinfection: This process involves adding chemicals or applying physical methods to kill or inactivate the remaining microorganisms in the water. The common disinfectants are chlorine, chloramine, ozone and ultraviolet light.
– Aeration: This process involves exposing the water to air to remove volatile organic compounds and radon gas that may be present in the water.
– Ion exchange: This process involves passing the water through a resin that exchanges ions with the dissolved contaminants. The resin can remove hardness minerals (calcium and magnesium), heavy metals (lead and mercury) and radionuclides (uranium and cesium).
– Reverse osmosis: This process involves applying high pressure to force the water through a semi-permeable membrane that rejects most of the dissolved contaminants and some microorganisms. The membrane can remove salts (sodium and chloride), nitrates, pesticides and pharmaceuticals.
Home water filter systems can also be used to improve the quality of drinking water at the point of use. Some of the common types of home water filter systems are:
(Read Also: Home water filter system)
– Pitcher filters: These are simple devices that consist of a pitcher with a filter cartridge inside. The filter cartridge can remove chlorine, bad taste and odor from tap water.
– Faucet-mounted filters: These are devices that attach to the faucet and filter the water as it flows out. The filter cartridge can remove chlorine, lead, cysts and some pesticides from tap water.
– Under-sink filters: These are devices that are installed under the sink and connect to a separate faucet on the sink. The filter cartridge can remove chlorine, lead, cysts, pesticides and pharmaceuticals from tap water.
– Countertop filters: These are devices that sit on the countertop and connect to the faucet with a hose. The filter cartridge can remove chlorine, lead, cysts, pesticides and pharmaceuticals from tap water.
– Whole-house filters: These are devices that are installed at the main water supply line and filter all the water entering the house. The filter cartridge can remove sediment, chlorine, iron and manganese from tap water.
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