WELL Factsheet: Bacteriological testing of water

The potential for water-borne disease arises when water is polluted with faecal matter. Polluted water may contain pathogenic (disease-causing) faecal bacteria, viruses, or other micro-organisms. It would be far too complex to try and detect all of these on a routine basis, and in any case many of the pathogens may only be present in very small numbers or not at all. It is therefore normal practice to look for ‘indicator bacteria”. These are species which are always excreted in large numbers in the faeces of warm-blooded animals, whether they are healthy or sick. Their presence indicates faecal contamination; it does not prove that water-borne disease is occurring.

Produced by WEDC and the London School of Hygiene and Tropical Medicine for the Department of International Development (DFID) of the UK government (now the Foreign, Commonwealth & Development Office (FCDO)), this archive collection of WELL factsheets remains relevant. It covers topics ranging from the anaerobic treatment of municipal wastewater through to water quality and safety plans.