Shepherds Lane Tank, 20 August 2014 (Sunbury)

Issue – Routine sampling at the tank resulted in detection of 1org/100mL of E.coli in the presence of 0.03mg/L monochloramine and 0.05mg/L total chlorine.

Actions – The tank was isolated from supply and spot-dosed with chlorine to return a residual of 1.4 mg/L free chlorine and 1.6mg/L total chlorine. The freshly chlorinated water was pumped into the reticulation system via pump station. Resampling was conducted for three consecutive days with all results clear of E.coli. The tank was inspected and some ingress was detected at the inspection hatch, which was repaired. This ingress is believed to be the root cause of the detection. Subsequently, in July 2015, major works to the roof were undertaken as a trial of new technology to provide a substantially more effective barrier to future potential rainwater ingress. The solution involves use of advanced polymers to seal between each sheet on the roof.

Shepherds Lane Tank, 12 November 2014 (Sunbury)

Issue – Routine sampling at the tank resulted in detection of 2org/100mL of E.coli in the presence of 0.14mg/L monochloramine and 0.22mg/L total chlorine.

Actions – The tank was isolated from supply and partly drained for spot-dosing with chlorine to return a residual of 0.32mg/L monochlorine and 0.6mg/L total chlorine. The freshly chlorinated water was pumped into the reticulation system via pump station. The sample tap was disinfected and flushed, and the tank was inspected which showed no signs of entry by contaminates. Resampling was conducted for three

consecutive days with all results clear of E.coli. The root cause was believed to be rainwater ingress through the roof. Subsequently, in July 2015, major works to the roof were undertaken trialling new technology to

provide a substantially more effective barrier to future potential rainwater ingress. The solution involves use of

advanced polymers to seal between each sheet on the roof.

“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