Emerald – (Victoria) – E.coli
On 2 May 2007, E. coli was detected in two samples (10 organisms/100mL at the high level tank and 4 organisms/100mL at a customer tap) from the Emerald water sampling locality. Extensive cleaning of the water mains was carried out and subsequent samples were clear of E. coli. Chlorine set point was also increased by 0.2 milligrams per litre to improve the microbiological
performance of the locality.
On 8 December 2007, an E. coli test result of 1 organism/100mL was reported in a sample taken at a customer tap in Emerald. Localised cleaning of water mains and chlorination of storages
in the locality were undertaken. E. coli was not detected in the subsequent additional samples collected across the locality.
On 12 February 2008, an E. coli test result of 3 organisms/100mL was reported in a sample taken from a customer tap in the Emerald water sampling locality. Further water quality testing indicated the problem was localised to this Gembrook distribution zone. In response, the tank was isolated from the distribution system, drained, inspected, cleaned and repaired. The tank was refilled and spot dosed with chlorine. E. coli was not detected in the subsequent additional samples collected across the locality.
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