2015 November – Oak Valley (Queensland) – E.coli

Oak Valley (Queensland): E.coli
Incident Description: Detection of E.coli (1or/100ml) in an Oak Valley house sample on 23rd November 2015. Free chlorine was 0.19mg/L and total chlorine was 0.27mg/L. pH was 6.9. The rolling average for the month was 99.9%. Four other samples in the Oak Valley area did not detect E.coli .

Corrective and Preventative Actions: There was a chlorine dosing fault during the night at the re-chlorination station at Mt Jack. This allowed a “glug” of minimally chlorinated water to enter the system. Pumps were resetand the area was flushed. All resamples came back clear of E.coli.

“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