20/11/2008 (16MPN/100mL) – The Birregurra water sampling locality is a small locality servicing a population of approximately 675 people. Raw water is treated and disinfected at Birregurra Water Treatment Plant prior to entering the reticulation system. A water pumping station feeds two high level tanks that float on the system and provide pressure to the high level areas of the reticulation network.
E.coli was detected in the high level tank (number 2) during routine water quality sampling on 20 November 2008. The high level tank was immediately isolated and dosed with chlorine. Samples taken from the high level tank (number 1) at the same time were free from E.coli.
The Birregurra Water Treatment Plant, which is the last point of treatment, had no disinfection failures or treatment faults prior to or after the detection. Review of recent monitoring results from the system did not show any abnormalities. There had been negligible flows from the high level tanks; and as such, it was very unlikely that water from tank number 2 had been directly suppling customers. As a precaution, the supply main from the high level tanks to the reticulation system was scoured. Follow up sampling of the reticulation system and both high level tanks did not detect E.coli. Inspection of the high level tanks provided no evidence of contamination, i.e. from bird life etc. A direct cause of the detection could not be identified.
October 19 2011: Birregurra – E.coli
Detection of Escherichia coli in high level tank no. 2 (1 MPN/100mL). Tank was immediately isolated and disinfected. Inspection of the tank did not identify any potential contamination issues. All follow up results were clear of Escherichia coli.
Escherichia coli should not be detected in any 100 mL sample of drinking water. If detected
in drinking water, immediate action should be taken including investigation of potential
sources of faecal contamination.
“Coliforms are Gram-negative, non-spore-forming, rod-shaped bacteria that are capable of aerobic and facultative anaerobic growth in the presence of bile salts or other surface active agents with similar growth-inhibiting properties. They are found in large numbers in the faeces of humans and other warm-blooded animals, but many species also occur in the environment.
Thermotolerant coliforms are a sub-group of coliforms that are able to grow at 44.5 ± 0.2°C. E. coli is the most common thermotolerant coliform present in faeces and is regarded as the most specific indicator of recent faecal contamination because generally it is not capable of growth in the environment. In contrast, some other thermotolerant coliforms (including strains of Klebsiella, Citrobacter and Enterobacter) are able to grow in the environment and their presence is not necessarily related to faecal contamination. While tests for thermotolerant coliforms can be simpler than for E. coli, E. coli is considered a superior indicator for detecting faecal contamination…” ADWG 2011