2017 April – Mount Rowan (Victoria) – E.coli

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Mount Rowan Tank (Ballarat)

27 April 2017 Mt Rowan Tank (Ballarat system) E. coli – 100 MPN/100mL 103 connections in the pressure supply zone for the network treated water storage tank

Informed DHHS and initiated incident team response. Confirmed residual disinfection in the tank and surrounding reticulation system. Reviewed hydraulics of tank and altered operation mode to prevent discharge into the system. Resampled tank. Conducted an external and internal inspection of tank integrity by divers – including a rainwater ingress check. Some leakage around the hatch identified as the source of contamination. A full sealing program conducted on the hatch and other parts of the tank as a precaution. Spot dosed the tank with disinfectant and verified adequate residual in tank and surrounding reticulation. Resamples post corrective actions

“E.coli

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