The fate ofEscherichia colithrough water treatment and in distribution

Abstract

SUMMARY The removal of E. coli bacteria at each stage of water treatment is presented, showing how the filtration stages contribute most to reduction of bacterial numbers in the water. At treatment works without filtration stages, the emphasis is put on catchment management to limit contamination of the raw water and ensure that the numbers of viable E. coli in the source water remain low. Routine monitoring of the raw water provides data on seasonal trends in numbers of E. coli bacteria and allows effective management of supply. In the UK there is no evidence that E. coli grows in the water distribution system, whether in the planktonic stage or within biofilms (O'Neill et al. 1997). The detection of E. coli in the distribution system is rare and prompts a thorough investigation. Repeat samples are taken from the point which originally failed, along with a number of hydraulically linked samples including samples from hydrants. The response to the detection of E. coli is discussed. A series of experiments carried out on a pilot pipe system is briefly described and the results discussed in relation to the routine samples taken in the Thames Water Supply area.

Leaching of bioluminescentEscherichia coliO157:H7 from sheep and cattle faeces during simulated rainstorm events

“…Rain events have been shown to promote the leaching of faecal bacteria within soil environments, leading to direct contamination of the wider environment (McMath and Holt 2000; McGechan and Vinten 2003). This study has shown that raindrops readily disperse E. coli O157:H7 from both sheep and cattle faeces.…”

“…Once introduced into the environment, hydrological pathways such as overland flow and preferential flow readily facilitate the dispersal of E. coli O157:H7 and other pathogens, while leaching can lead to groundwater contamination (Chalmers et al. 2000; McMath and Holt 2000; Heinonen‐Tanski and Uusi‐Kamppa 2001; Collins and Rutherford 2004). Pathogen transport following periods of heavy rainfall is especially important in increasing the concentrations of pathogens in many watersheds (Fenlon et al.…”

“…Pathogen transport following periods of heavy rainfall is especially important in increasing the concentrations of pathogens in many watersheds (Fenlon et al. 2000; McMath and Holt 2000). This is of concern as human E. coli O157 infections have occurred as a result of groundwater contamination (Wang and Doyle 1998; Licence et al.…”