E. coli and coliform bacteria in private water supplies

Disease-causing microorganisms, pathogens, can be transmitted by drinking water causing acute as well as chronic disease. Waterborne pathogens include a wide range of viruses, bacteria and parasitic protozoa. Since these waterborne pathogens mainly derive from faecal contamination, microbiological drinking water quality is assessed by analysing indicator bacteria such as E. coli, normally occurring in the gut of warm blooded animals, including humans. A quantitative microbiological risk assessment was performed to estimate acceptable water quality. It showed that the probability of stomach illness is greatly increased if the contamination comes from wastewater. If the contamination comes from manure, there is a slightly increased risk of enterohaemorrhagic E. coli. This means that E. coli should not be detected in 100 ml samples to achieve water quality comparable to municipal drinking water. Note: this report is published by the Swedish Food Agency (Livsmedelsverket) as part of their Report Series (www.livsmedelsverket.se/bestall-ladda-ner-material/sok-publikationer/artiklar/2021/l-2021-nr-03-e.-coli-och-koliforma-bakterier-i-brunnsvatten)SE; PDF; Efsa.focalpoint@slv.s