23/11/16: Williams Rise Tank, Sunbury. E.coli, Faecal Strepococci

E.coli detection in Williams Rise Tank and network, 5 May 2016 (Sunbury)

Williams Rise Tank, 5 May 2016 (Sunbury) Issue – Routine sampling at the tank resulted in a detection of 0.5org/100ml of E.coli in the presence of 0.20mg/L total chlorine. Actions – The tank was isolated from supply and spotdosed with chlorine to return a residual of 0.42mg/L total chlorine. The freshly chlorinated water was pumped into the reticulation system via the pump station. Resampling was conducted for three consecutive days with all results clear of E.coli. The reported routine result was declared as a false positive. The tank was inspected and while some ingress at the inspection hatch may have been an issue, an error made by the external laboratory was suspected as the root cause. Outcome – In early 2016, the tank was assessed by external consultants for refurbishment and booster chlorinator to be installed in 2016/17.

E.coli detection in Williams Rise Tank and network, 23 November 2016 (Sunbury)

“Issue – During storm activity from 22-24 November 2016, the Williams Rise Tank in Sunbury experienced a small volume of rainwater intrusion. This resulted in a low-level E.coli detection (1 org/100ml), in the routine sample taken on 23 November. Resampling to verify the result was undertaken on the same day and confirmed the presence of both low-level E.coli (1 org/100ml) and Faecal Streptococci (3 orgs/100ml) – both in the tank and at one location downstream in the Williams Rise network.

The Williams Rise Tank supplies to an isolated part of the network near Sunbury, 44 properties in total. DHHS was notified on the day of the reported detection in accordance with the requirements of Section 18.

Actions – After resampling on the day of the detection, the tank and network were spot dosed with chlorine to disinfect the water supply. Sampling on the following two days verified that the tank and network had no further contamination present and minor repairs were made to the tank roof and hatch as a result of storm damage.

Outcome – The tank was reviewed as part of the Drinking Water Tank Integrity Program with appropriate work scheduled for 2017/18, based on priority.

A permanent chlorinator system was installed early 2017 to maintain adequate chlorine levels. The tank is audited yearly as part of the HACCP system.” Western Water


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