2009 November – McCrae – Cook St (Victoria) – E.coli

McCrae  – Cook Street – E.coli
The seventh event was a detection of E. coli from a routine sample taken on 6 November 2009 at Cook Street Tank, McCrae, (11 E. coli organisms per 100 mL) with a free chlorine residual of 0.03 mg/L. The tank, which is located within the Dromana locality, is supplied by Cardinia Reservoir. The tank was immediately inspected, dosed with sodium hypochlorite for disinfection, and damage to bird proofing was repaired. All system checks were clear and the resamples taken at the tank and two customer sample taps fed by the tank in the downstream reticulation system were clear of E. 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