2015 November – Hurstbridge (Victoria) – E.coli

Hurstbridge (Victoria) – E.coli

On 12 November 2015, E.coli of 1 org/100ml was detected at the Hurstbridge tank within the
Mernda/Hurstbridge sampling locality. The tank was immediately disinfected with chlorine and pre and post disinfection samples were collected at the tank and five other locations within the same water sampling locality. Booster chlorination and additional ongoing sampling for Hurstbridge Reservoir was undertaken until the completion of the rectification works. All
subsequent results were clear of E.coli. Water ingress through small holes in the tank roofwas identified as a possible source of contamination. The tank was subsequently taken offline,
cleaned and repaired. Notification to customers was not required. The incident lasted for 30 hours. Remedial action on the tank was completed on 16 December 2015.


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