Drinking water quality standards

Drinking water quality standards describes the quality parameters set for drinking water.

In Europe, this includes the European Drinking Water Directive and Romanian standards as required by the law 458 / 2002, modified and completed by law 311 / 2004.

For countries without a legislative or administrative framework for such standards, the World Health Organization publishes guidelines on the standards that should be achieved.

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 United States, 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.

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 (Analitical Quality Control). 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.

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.

The following table provides a comparison of a selection of parameters for concentrations listed by the European Union, Romania and WHO.

PARAMETERS AND PARAMETRIC VALUES

Microbiological parameters

Parameter	Unit	Parametric value
		European Union	Romania	WHO
Escherichia coli (E. coli)	(number/100 ml)	0	0	0
Enterococci	(number/100 ml)	0	0	0

Chemical parameters

Parameter	Unit	Parametric value
		European Union	Romania	WHO
Acrylamide note 1)	μg/l	0.10	0.10	0.50
Antimony	μg/l	5.00		20.00
Arsenic	μg/l	10.00	10.00	10.00
Benzene	μg/l	1.00	1.00	10.00
Benzo(a)pyrene	μg/l	0.01	0.01
Boron	mg/l	1.00	1.00	0.50
Bromate note 2)	μg/l	10.00	10.00	10.00
Cadmium	μg/l	5.00	5.00	3.00
Chromium	μg/l	50.00	50.00	50.00
Copper note 3)	mg/l	2.00	0.10	2.00
Cyanide	μg/l	50.00		70.00
1,2-dichloroethane	μg/l	3.00	3.00	30.00
Epichlorohydrin note 1)	μg/l	0.10	0.10	0.40
Fluoride	mg/l	1.50	1.20	1.50
Lead note 3) and 4)	μg/l	10.00		10.00
Mercury	μg/l	1.00	1.00	6.00
Nickel note 3)	μg/l	20.00	20.00	70.00
Nitrate note 5)	mg/l	50.00	50.00	50.00
Nitrite note 5)	mg/l	0.50	0.50	3.00
Pesticides note 6) and 7)	μg/l	0.10	0.10
Pesticides – total note 6) and 8)	μg/l	0.50	0.50	0.50
Polycyclic aromatic hydrocarbons note 9)	μg/l	0.10	0.10	0.10
Selenium	μg/l	10.00	10.00	10.00
Tetrachloroethene and Trichloroethene	μg/l	10.00	10.00	10.00
Trihalomethanes – total note 10)	μg/l	100.00	100.00
Vinyl chloride	μg/l	0.50		0.30

Note 1: The parametric value refers to the residual monomer concentration in the water as calculated according to specifications of the maximum release from the corresponding polymer in contact with the water.

Note 2: Where possible, without compromising disinfection, Member States should strive for a lower value. For the water referred to in Article 6(1)(a), (b) and (d), the value must be met, at the latest, 10 calendar years after the entry into force of the Directive. The parametric value for bromate from five years after the entry into force of this Directive until 10 years after its entry into force is 25 μg/l.

Note 3: The value applies to a sample of water intended for human consumption obtained by an adequate sampling method (1) at the tap and taken so as to be representative of a weekly average value ingested by consumers. Where appropriate the sampling and monitoring methods must be applied in a harmonised fashion to be drawn up in accordance with Article 7(4). Member States must take account of the occurrence of peak levels that may cause adverse effects on human health.

Note 4: For water referred to in Article 6(1)(a), (b) and (d), the value must be met, at the latest, 15 calendar years after the entry into force of this Directive. The parametric value for lead from five years after the entry into force of this Directive until 15 years after its entry into force is 25 μg/l.

Member States must ensure that all appropriate measures are taken to reduce the concentration of lead in water intended for human consumption as much as possible during the period needed to achieve compliance with the parametric value.

When implementing the measures to achieve compliance with that value Member States must progressively give priority where lead concentrations in water intended for human consumption are highest.

Note 5: Member States must ensure that the condition that [nitrate]/50 + [nitrite]/3 # 1, the square brackets signifying the concentrations in mg/l for nitrate (NO3) and nitrite (NO2), is complied with and that the value of 0,10 mg/l for nitrites is complied with ex water treatment works.

Note 6: ‘Pesticides’ means: organic insecticides, organic herbicides, organic fungicides, organic nematocides, organic acaricides, organic algicides, organic rodenticides, organic slimicides, related products (inter alia, growth regulators) and their relevant metabolites, degradation and reaction products. Only those pesticides which are likely to be present in a given supply need be monitored.

Note 7: The parametric value applies to each individual pesticide. In the case of aldrin, dieldrin, heptachlor and heptachlor epoxide the parametric value is 0,030 μg/l.

Note 8: ‘Pesticides — Total’ means the sum of all individual pesticides detected and quantified in the monitoring procedure.

Note 9: The specified compounds are: benzo(b)fluoranthene, benzo(k)fluoranthene, benzo(ghi)perylene, indeno(1,2,3-cd)pyrene.

Note 10: Where possible, without compromising disinfection, Member States should strive for a lower value. The specified compounds are: chloroform, bromoform, dibromochloromethane, bromodichloromethane.

For the water referred to in Article 6(1)(a), (b) and (d), the value must be met, at the latest, 10 calendar years after the entry into force of this Directive. The parametric value for total THMs from five years after the entry into force of this Directive until 10 years after its entry into force is 150 μg/l.

Indicator parameters

Parameter	Unit	Parametric value
		European Union	Romania	WHO
Aluminium	μg/l	200.00	200.00	2000.00-5000.00
Ammonium	mg/l	0.50	0.50	1.50
Chloride note 1)	mg/l	250.00	250.00	200.00-300.00
Clostridium perfringens (including spores) note 2)	no./100ml	0	0	0
Colour	Acceptable to consumers and no abnormal change
Conductivity note 1)	μS cm-1 at 20 °C	2,500.00	2,500.00
Hydrogen ion concentration note 1) and 3)	pH units	>= 6.5 and <=9.5	>= 6.5 si <=9.5
Iron	μg/l	200.00	200.00
Manganese	μg/l	50.00	50.00
Odour	Acceptable to consumers and no abnormal change
Oxidisability note 4)	mg/l O2	5.00	5.00
Sulphate note 1)	mg/l	250.00	250.00
Sodium	mg/l	200.00	200.00
Taste	Acceptable to consumers and no abnormal change
Colony count 22°	No abnormal change
Coliform bacteria note 5)	no./100 ml	0	0
Total organic carbon (TOC) note 6)	No abnormal change
Turbidity note 7)	Acceptable to consumers and no abnormal change		<=5UNT

Radioactivity

Parameter	Unit	Parametric value
		European Union	Romania	WHO
Tritium	Bq/l	100.00
Total indicative dose	mSv/year	0.10

Note 1: The water should not be aggressive.

Note 2: This parameter need not be measured unless the water originates from or is influenced by surface water. In the event of non-compliance with this parametric value, the Member State concerned must investigate the supply to ensure that there is no potential danger to human health arising from the presence of pathogenic micro-organisms, e.g. cryptosporidium.

Note 3: For still water put into bottles or containers, the minimum value may be reduced to 4,5 pH units. For water put into bottles or containers which is naturally rich in or artificially enriched with carbon dioxide, the minimum value may be lower.

Note 4: This parameter need not be measured if the parameter TOC is analysed.

Note 5: For water put into bottles or containers the unit is number/250 ml.

Note 6: This parameter need not be measured for supplies of less than 10 000 m³ a day.

Note 7: In the case of surface water treatment, Member States should strive for a parametric value not exceeding 1,0 NTU (nephelometric turbidity units) in the water ex treatment works.