2016 September – Winton (Queensland) – E.coli
Incident Description: The non-compliance was a detection of E. coli from a routine sample taken on 27/09/2016 at 104 Elderslie Street. 1 cfu E. coli organisms per 100 mL was/were detected when testing was completed on the 28th September, with a disinfection residual of nil (no
disinfection used in Winton Shire Council water supply). Notification was given to Winton Shire Council on the 29th September.
Corrective and Preventative Actions: The reservoir was flushed, and shock dosed with chlorine. Further sampling of the reservoir was completed on the 4th October, testing on the 5th October with no trace of E Coli. All follow up samples were free of E. coli. Testing procedures were reviewed to detect whether the source of E.coli could have been from handling contamination. The same process was used at each of the 6 sites with no other recording of E Coli, handling was unlikely to be the cause. With only one site registering E Coli it is unlikely that it was within the reticulation system. The approach that was taken is to continue testing post
chlorine dosing to see if there were any further occurrences. The subsequent testing came back clear, no further action was taken other than to maintain water sampling and testing regime as per the DWQMP.
“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