Detection of E. coli – Catalina Parade, Jacobs Well
6.1.1 Incident Description: On 13 August 2018, during routine verification monitoring a positive detection of E. coli (3 MPN/100mL) was recorded at a sample tap in the Pimpama Coomera WSD. The free chlorine residual was 0.74 mg/L.
Corrective and Preventative Actions: Immediately upon notification of the positive result incident management procedures were activated. Flushing of the reticulation network was undertaken. Inspections of the supply reservoir revealed no damage or potential ingress, and investigation of the re-chlorination station located about 1km upstream indicated no problems or issue. Subsequent retests at this site and additional sampling sites in the WSD yielded negative results for 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