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Rationale - what it means and why it is an important measure
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The microbiological and chemical quality of water are of prime importance to the health of human communities. It is extremely important to ensure that water supplies are free from pathogenic bacteria and not contaminated by sewage. The chemical parameters of water quality are nitrates, fluorine, benzene and chlordane.
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How it is compiled, what data are needed
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- Microbiological quality is measured as a ratio of the number of measurements exceeding zero faecal coliforms/100 ml to the total number of measurements done;
- Chemical quality is measured as a ratio of the number of measurements exceeding WHO guidelines to the total number of measurements done;
- Population affected by violations of drinking water quality standards;
- Number days per year that WHO drinking water standards are exceeded.
These indicators should be measured annually.
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Measurements and units
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Chemical quality (%)
Microbiological quality (%)
Number of days in exceedence (days)
Population affected (number of people)
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Possible temporal and spatial format
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trend charts, graphs, maps, etc
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Reference to methodology resources
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WHO, 1997. Healthy Cities Indicators: Analysis of Data from Cities Across Europe.
OECD, 1997. Better Understanding Our Cities: The Role of Urban Indicators. EEA Indicator Set.
EC. Council Directive 98/83/EC on Drinking Water Quality. http://europa.eu.int/water/index_en.html
ICLEI, 2000. Measuring Progress, Cities 21: Pilot Project Final Report.
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Objective
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To reduce the percentage of measurements exceeding the recommended WHO guidelines.
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Targets, benchmarks, reference values
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- WHO limit values for chemical substances: nitrates (50 mg/l), fluorine (1.5 mg/l), benzene (10 ug/l) and chlordane (0.2 ug/l).
- The Drinking Water Directive (Council Directive 98/83/EC) on the quality of water intended for human consumption. Microbiological parameters are: Escherichia coli (E.coli) = 0/250 ml, Enterococci 0/250 ml, Pseudomonas aeruginosa 0/250 ml.
- National standards
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References to examples of application
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Quality of drinking water (pH, COD, nitrate etc.) in Prague: http://www.ceroi.net/reports/prague/issues/Water/state.htm
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Other comments / background
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Russian Federation, in 1995: about 22 per cent of drinking water samples did not meet chemical standards and almost 9 per cent exceeded acceptable bacteriological levels.
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