Bacteriological quality of drinking-water according to World Health Organisation (WHO)

 

Microbiological examination provides the most sensitive indication of pollution of drinking-water supplies

Organisms Guideline Value

All water intended for drinking:
E.coli or thermotolerant coliform bacteria
b, c

Treated water entering the distribution system:
E.coli or thermotolerant coliform bacteria
b

Treated water in the distribution system:
E.coli or thermotolerant coliform bacteria
b

Guideline Value

Must not be detectable in any 100 ml sample

Must not be detectable in any 100 ml sample

Must not be detectable in any 100 ml sample

a Immediate investigative action must be taken, if E. coli are detected.

b Although E. coli is the more precise indicator of faecal pollution, the count of thermotolerant coliform bacteria is an acceptable alternative. If necessary, proper confirmatory tests must be carried out. Total coliform bacteria are not acceptable indicators of the sanitary quality of water supplies, particularly in tropical areas, where many bacteria of no sanitary significance occur in almost all untreated supplies.

c It is recognized that the great majority of rural water supplies, especially in developing countries, faecal contamination is widespread. Especially under these conditions medium-term targets for the progressive improvement of water supplies should be set.

See the current guidelines on the WHO Website

 

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Billwerder Ring 10, 21035 Hamburg, Germany
Tel.:  +49 (40) 734741-0, Fax: +49 (40) 734741-10

Guideline Value

Must not be detectable in any 100 ml sample

Must not be detectable in any 100 ml sample

Must not be detectable in any 100 ml sample

Organisms Guideline Value
All water intended for drinking: E.coli or thermotolerant coliform bacteria b, c

Guideline Value
Must not be detectable in any 100 ml sample

 

Organisms Guideline Value
Treated water entering the distribution system: E.coli or thermotolerant coliform bacteria b

Guideline Value
Must not be detectable in any 100 ml sample

 

Organisms Guideline Value
Treated water in the distribution system:
E.coli or thermotolerant coliform bacteria
b

Guideline Value
Must not be detectable in any 100 ml sample