Chemicals in Drinking Water

Chemicals are a major problem as far as drinking water contaminants are concerned, and many chemicals feature on the US Environmental Protection Agency's list of regulated primary drinking water contaminants, with a few chemicals listed as secondary drinking water contaminants due to aesthetic problems that they cause in drinking water. The list of chemicals that are considered drinking water contaminants is extensive, and includes both organic and inorganic chemicals. The EPA has 53 organic chemicals, 17 inorganic chemicals, and 7 chemicals that are either used as water disinfectants, or are byproducts of water disinfectants, listed as regulated primary drinking water contaminants. Chemicals are introduced into the water system at various stages: many chemicals in drinking water come from naturally occurring minerals that are introduced into the water at the source; chemicals are added to water during water treatment, where some may react with other substances present in the water to form other chemicals; and chemicals may be stripped from piping and plumbing fittings as water travels through the water distribution network.

Chemicals in the Source Water

Naturally occurring chemicals occur in source water due to leaching of minerals from rocks and soils, and the composition of these minerals in the water determines whether the water is hard or soft. Other pollutants such as arsenic, asbestos, nitrates, pesticides, industrial chemicals, and chemicals used in sewage treatment facilities can enter the source water from agricultural or urban runoff, or from being discharged into the waterway. A new area of concern is pharmaceutical contaminants that are being detected in increasing amounts both in natural water sources and in drinking water. These pharmaceutical chemicals include prescription drugs, anti-biotics, and hormones that can cause reproductive defects in fish and wildlife, and hence could potentially pose a health risk to humans, especially to an unborn fetus.

Chemicals Due to Water Treatment

Chemicals are introduced into drinking water during water treatment in order to disinfect the water and kill off disease causing microorganisms. The chemicals that enter drinking water during water treatment are referred to as disinfection by-products (or DBPs). Chlorine is the most common method of disinfection used to remove pathogenic drinking water contaminants. Chlorination results in numerous chemical by-products, including the following groups of chemical compounds: trihalomethanes, halogenated acetonitriles, chlorinated ketones, halogenated phenols, cyanogen halides and chloral hydrate. Many of these by-products have been implicated as being potentially carcinogenic, and have been linked to birth defects.

Fluoride is another chemical that is routinely added to drinking water during water treatment. Fluoride is added to drinking water due to the health benefits it offers – fluoride prevents dental caries, but if a person is exposed to excessive amounts of fluoride they can get dental fluorosis, which in its mild form makes a persons teeth discolored, but can cause weakening of tooth enamel at high exposures, and at very high exposures can cause dental fluorosis, with weakening of the bones.

Chemicals in the Distribution Network

Chemicals can leach into drinking water as the water passes through pipes and plumbing fittings. Asbestos can be leached from concrete-asbestos pipes; polyvinyl chloride can be leached from PVC pipes; polyethylene can be leached from plastic pipes; and copper, iron and lead can be leached from metal pipes. The corrosiveness of drinking water is more severe when water is soft (acidic), thus drinking water with a low pH is more likely to strip metals from pipes and fixtures as it is transported through.

Water Purification Methods to Remove Chemicals

Water purification methods for removing chemical drinking water contaminants include reverse osmosis water purification systems, distillation water purification systems, nanofiltration water purification filters, and water softeners. The water purification system that you opt for will depend on the type of chemical drinking water contaminants that you need to remove from your water. Household water purification systems can either be used at point of use (point of use systems) where treated water is delivered to a single outlet tap; or at point of entry (point of entry systems), where water entering the household is treated so that the whole house receives water that has been treated by the selected water purification system.

References

Basrur, S.V. Chemicals in Drinking Water. Toronto Public Health: Technical PDF. March, 2001. Web. 11 Dec, 2011.

Centers for Disease Control and Prevention. Drinking Water: A Guide to Drinking Water Treatment Technologies for Household Use. CDC.gov. 10 April, 2009. Web. 11 Dec, 2011.

Hooper, R. 'Top 11 Compounds in US Drinking Water.' New Scientist. 12 Jan, 2009. Web.11 Dec, 2011. http://water.epa.gov/drink/contaminants/index.cfm#Inorganic

US Environmental Protection Agency. Drinking Water Contaminants: List of Contaminants and their MCLs. EPA.gov. 30 Sept, 2011. Web. 11 Dec, 2011. http://water.epa.gov/drink/contaminants/index.cfm#Inorganic

 
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