Hurstbridge – (Victoria) – E.coli
seeping into the tank following a heavy rainfall event. The tank was inspected, using a new ‘floating camera’ technique (see explanation in Section 11.6 page 27), and necessary repair was conducted to prevent this event occurring in the future. The tank was also spot dosed
and chlorine levels checked. Block flushing of the mains in the area was also conducted until chlorine residuals reached acceptable levels. E. coli was not detected in the post samples
collected at the tank and customer sampling taps. Additional tank inspection and maintenance was initiated in response to the high rate of water quality events occurring with tanks and
reservoirs (see Section 11.5 on page 27). No subsequent action was required (Yarra Water Valley Drinking Water Quality Report 2009-10)
Tank) returned E. coli detections, at 3 orgs/100 mL and 5 orgs/100 mL respectively. The tanks were spot dosed with chlorine and the mains in the area flushed. E. coli was not detected in the
post samples collected from both Nutfield and Hurstbridge tanks and customer sampling taps. No subsequent action was required. (Yarra Water Valley Drinking Water Quality Report 2009-10)
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