Drinking water quality standards

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Drinking water quality standards describes the quality parameters set for drinking water. Despite the truism that every human on this planet needs drinking water to survive and that water may contain many harmful constituents, there are no universally recognized and accepted international standards for drinking water. Even where standards do exist, and are applied, the permitted concentration of individual constituents may vary by as much as ten times from one set of standards to another.

Many developed countries specify standards to be applied in their own country. In Europe, this includes the European Drinking Water Directive and in the United States the United States Environmental Protection Agency (EPA) establishes standards as required by the Safe Drinking Water Act. For countries without a legislative or administrative framework for such standards, the World Health Organisation publishes guidelines on the standards that should be achieved. China adopted its own drinking water standard GB3838-2002 (Type II) enacted by Ministry of Environmental Protection in 2002.

Where drinking water quality standards do exist, most are expressed as guidelines or targets rather than requirements, and very few water standards have any legal basis or, are subject to enforcement. Two exceptions are the European Drinking Water Directive and the Safe Drinking Water Act in the USA, which require legal compliance with specific standards.

In Europe, this includes a requirement for member states to enact appropriate local legislation to mandate the directive in each country. Routine inspection and, where required, enforcement is enacted by means of penalties imposed by the European Commission on non-compliant nations.

Countries with guideline values as their standards include Canada, which has guideline values for a relatively small suite of parameters, New Zealand, where there is a legislative basis, but water providers have to make "best endeavours" to comply with the standards, and Australia.

Video Drinking water quality standards

Range of standards

Although drinking water standards frequently are referred to as if they are simple lists of parametric values, standards documents also specify the sampling location, sampling methods, sampling frequency, analytical methods, and laboratory accreditation AQC. In addition, a number of standards documents also require calculation to determine whether a level exceeds the standard, such as taking an average. Some standards give complex, detailed requirements for the statistical treatment of results, temporal and seasonal variations, summation of related parameters, and mathematical treatment of apparently aberrant results.

Maps Drinking water quality standards

Parametric values

(Parametric value also has a specific and different mathematical meaning)

A parametric value in this context is most commonly the concentration of a substance, e.g. 30 mg/l of Iron. It may also be a count such as 500 E. coli per litre or a statistical value such as the average concentration of copper is 2 mg/l. Many countries not only specify parametric values that may have health impacts but also specify parametric values for a range of constituents that by themselves are unlikely to have any impact on health. These include colour, turbidity, pH, and the organoleptic (aesthetic) parameters (taste and odour).

It is possible and technically acceptable to refer to the same parameter in different ways that may appear to suggest a variation in the standard required. For example, nitrite may be measured as nitrite ion or expressed as N. A standard of "Nitrite as N" set at 1.4 mg/l equals a nitrite ion concentration of 4.6 mg/l. This is an apparent difference of nearly threefold.

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Australian standards

Drinking water quality standards in Australia have been developed by the Australian Government National Health and Medical Research Council (NHMRC) in the form of the Australian Drinking Water Guidelines. These guidelines provide contaminant limits (pathogen, aesthetic, organic, inorganic, and radiological) as well as guidance on applying limits for the management of drinking water in Australian drinking water treatment and distribution.

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European Union standards

The following parametric standards are included in the Drinking Water Directive and are expected to be enforced by appropriate legislation in every country in the European Union. Simple parametric values are reproduced here, but in many cases the original directive also provides caveats and notes about many of the values given.

• Acrylamide 0.10 ?g/l
• Antimony 5.0 ?g/l
• Arsenic 10 ?g/l
• Benzene 1.0 ?g/l
• Benzo(a)pyrene 0.010 ?g/l
• Boron 1.0 mg/l
• Bromate 10 ?g/l
• Cadmium 5.0 ?g/l
• Chromium 50 ?g/l
• Copper 2.0 mg/l
• Cyanide 50 ?g/l
• 1,2-dichloroethane 3.0 ?g/l
• Epichlorohydrin 0.10 ?g/l
• Fluoride 1.5 mg/l
• Lead 10 ?g/l
• Mercury 1.0 ?g/l
• Nickel 20 ?g/l
• Nitrate 50 mg/l
• Nitrite 0.50 mg/l
• Pesticides 0.10 ?g/l
• Pesticides - Total 0.50 ?g/l
• Polycyclic aromatic hydrocarbons 0.10 ?g/l Sum of concentrations of specified compounds;
• Selenium 10 ?g/l
• Tetrachloroethene and Trichloroethene 10 ?g/l Sum of concentrations of specified parameters
• Trihalomethanes -- Total 100 ?g/l Sum of concentrations of specified compounds
• Vinyl chloride 0.50 ?g/l

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United States standards

In the USA, the federal legislation controlling drinking water quality is the Safe Drinking Water Act (SDWA) which is implemented by the EPA, mainly through state or territorial primacy agencies. States and territories must implement rules that are at least as stringent as EPA's to retain primary enforcement authority (primacy) over drinking water. Many states also apply their own state-specific standards, which may be more rigorous or include additional parameters. Standards set by the EPA in the USA are not international standards since they apply only to a single country, however, many countries look to the USA for appropriate scientific and public health guidance and may reference or adopt USA standards.

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World health Organisation Guidelines

The World Health Organisation (WHO) Guideline for Drinking-water Quality (GDWQ) include the following recommended limits on naturally occurring constituents that may have direct adverse health impact:

• Arsenic 10?g/l
• Barium 10?g/l
• Boron 2400?g/l
• Chromium 50?g/l
• Fluoride 1500?g/l
• Selenium 40?g/l
• Uranium 30?g/l

Organic species:

• Benzene 10?g/l
• Carbon tetrachloride 4?g/l
• 1,2-Dichlorobenzene 1000?g/l
• 1,4-Dichlorobenzene 300?g/l
• 1,2-Dichloroethane 30?g/l
• 1,2-Dichloroethene 50?g/l
• Dichloromethane 20?g/l
• Di(2-ethylhexyl)phthalate 8 ?g/l
• 1,4-Dioxane 50?g/l
• Edetic acid 600?g/l
• Ethylbenzene 300 ?g/l
• Hexachlorobutadiene 0.6 ?g/l
• Nitrilotriacetic acid 200?g/l
• Pentachlorophenol 9?g/l
• Styrene 20?g/l
• Tetrachloroethene 40?g/l
• Toluene 700?g/l
• Trichloroethene 20?g/l
• Xylenes 500?g/l

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Comparison of parametric values

The following table provides a comparison of a selection of parameters for concentrations listed by WHO, the European Union, EPA, and Ministry of Environmental Protection of China.

" indicates that no standard has been identified by editors of this article and ns indicates that no standard exists. ?g/l -> Micro grams per litre or 0.001 ppm, mg/L -> 1 ppm or 1000 ?g/l

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See also

• Water pollution

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References

Further reading

• CDC Water Quality and Testing
• Guidelines for drinking-water quality incorporating 1st and 2nd addenda (PDF). 1 (3rd ed.). World Health Organization. 2008. ISBN 978-92-4-154761-1. 
• European Drinking Water Directive
• EPA National Primary Drinking Water Standards
• EPA Drinking Water Regulations and Health Advisories May 1994

Source of article : Wikipedia