2009 December – Ferntree Gully Reservoir (Victoria) – E.coli

Ferntree Gully Reservoir  – Victoria – E.coli
The eighth event was a detection of E. coli from a routine sample taken on 14 December 2009 at Ferntree Gully Reservoir, (one E. coli organism per 100 mL) with a free chlorine residual of 0.07 mg/L. The tank, which is located within the Belgrave locality, is supplied by Silvan Reservoir. The tank was immediately isolated, inspected and dosed to a free chlorine residual of 0.5mg/L.
All system checks were clear and the resamples taken at the reservoir and two taps within the
reticulation system were clear of E. coli. The tank was then turned back into supply.

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