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Chloride in Drinking Water Where can I find information about Chloride in Drinking Water?Chloride
Chloride is a major constituent of most waters. It is normally present in low concentrations in surface waters, while groundwater will
contain varying amounts of chloride depending on the surrounding geology.
Chloride is widely distributed in the environment, generally
as sodium chloride (NaCl), potassium chloride (KCl) and calcium chloride (CaCl2).
The weathering and leaching of sedimentary rocks and soils and the dissolution of salt deposits release chlorides into water.
Chloride in the form of sodium chloride and calcium chloride is used extensively for snow
and ice removal. In various other forms it has a number of commercial and industrial applications and is used in wastewater
treatment.
Chloride in Drinking Water
Chloride in drinking water is generally not harmful to human beings until high
concentrations are reached, although it may be harmful to some people suffering from heart or kidney disease. Restrictions on
chloride concentrations in drinking water are generally based on palatability requirements rather than on health. The Guidelines for
Canadian Drinking Water Quality 1989 has set the aesthetic objective for chloride in drinking water at250 mg/L.
Chloride in drinking water may impart a salty taste at concentrations as low as 100 mg/L, however,
the limit of 250 mg/L is considered the taste threshold for the average individual.
Besides imparting a salty taste, chloride can affect the taste of coffee brewed in water containing
a high concentration of chloride. Chlorides also appear to exert a significant effect on the rate of corrosion of steel and aluminum and
can therefore affect some metals used in water handling systems.
Sources
In addition to chloride entering the groundwater from leaching of sedimentary rock and salt deposits,
other sources of contamination are road salt application and storage, sewage and industrial discharges, leachate from dumps and landfills,
and saltwater intrusion.
While a sudden increase in the chloride content of a water supply may not dramatically affect the
water quality, the increase may indicate a connection with a source of contamination and the increasing chloride levels should be
investigated further.
Treatment
Treatment techniques for the removal of chloride from the drinking water include demineralization
processes such as reverse osmosis, electro dialysis, ion exchange or distillation. Another method of removing
chloride from the drinking water would be the construction or reconstruction of a water well. This frequently involves the installation
of additional casing beyond the length (depth) normally required by regulation.
This document is also available as a PDF file.
Charlottetown
Jones Building
Robison, Alan (Senior Drinking Water Technologist)
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