2017 October – Mundoolun Reservoir, Mundoolun (Queensland). E.coli

Mundoolun Reservoir, Mundoolun (Qld) – E.coli

23/10/17: Mundoolun Reservoir (Queensland)  1 MPN/100mL

Incident Description

E. coli was detected in a sample collected on the 23rd January 2017 from the Mundoolun
reservoir sample tap. The E. coli result was 5 MPN/100mL with a total chlorine residual of
0.11mg/L. Re-testing confirmed E. coli present however no E. coli was present in the
surrounding area.

Corrective and Preventative Actions

Mundoolun reservoir supplying the area was isolated, inspected and dosed with liquid sodium
hypochlorite and the surrounding network flushed. Repeat testing resulted in no E. coli present.
Roof gaps found during the inspection were sealed to prevent ingress.
In consultation with Metro South Public Health Unit and DEWS, the reservoir was put back
online and surrounding areas were flushed to draw chlorine residual throughout the network.
Long term preventative actions includes manually dosing the reservoir with liquid chlorine to
maintain effective chlorine residual until an auto-dosing facility is designed via the 2017-18 FY
CAPEX program with implementation to follow.

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