2009 February – Somers (Victoria) – E.coli

Somers  – (Victoria) – E.coli

The fourth E.coli detection was from a routine sample taken at Somers Tank, in the Balnarring locality, on 11 February 2009 (three organisms per 100mL) with a free chlorine residual of 0.2 mg/L. The tank is supplied by the Somers- Flinders Pipeline via Tyabb Reservoir. Secondary
disinfection occurs at Tyabb Reservoir to maintain a chlorine residual of 1.4 mg/L of water leaving the Reservoir. The tank was immediately isolated, inspected and dosed to a free chlorine residual of 0.5mg/L. Samples taken at three nearby taps within the reticulation system, and on the Somers-Flinders Pipeline on the following day, were clear of E.coli. The tank remained off-line during the winter months due to low turnover, and will be put back into the system in summer when demands on the system increase.

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