2017 March – Yangan Park (Queensland) – E.coli

Incident Description: The first non-compliance was a detection of E. coli from a routine in-house sample  taken on 8 March 2017 at Yangan Park chlorine dosing shed. A follow up sample was taken on 9/3/2017 and sent to Queensland Health laboratory for testing. Additional samples were also taken from Mount Tabor Reservoirs, Yangan Reservoir, Yangan Park and Warwick Water Treatment Plant. The results from QHealth for Yangan Park were detection of three E. coli organisms per 100 mL, with a disinfection residual of 0.08mg/L; Mt Tabor Reservoir 1 were detection of two E. coli organisms per 100 mL, with a disinfection residual of 0.01mg/L
Corrective and Preventative Actions: Emptied and cleaned the reservoirs at Mount Tabor, monitored and maintained adequate chlorine residual throughout the system. Hatches in the reservoirs were replaced and screens installed at overflow pipes to prevent vermin entry. All follow up samples were free of E. coli.

Southern Downs Regional Council Drinking Water Quality Management Plan 2016-17

“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