2010/2017 – Wangaratta (Victoria) – E.coli, Turbidity, Iron

Wangaratta (Victoria) E.coli

11/11/10- < 24hr Wangaratta (Cox rd tank) E.coli :1org/100mL Investigations could not identify the source.Chlorine residuals were increased. Resample was clear.

22/03/11 Wangaratta (Omaru Rd tank) E.coli :>200orgs/mL Initial inspection of the tank could not identify a contamination source, however vigilance was escalated when resample was also positive (24/3). Despite not identifying a specific contamination source, a series of actions were undertaken (including cleaning of the tank, relocation of the sample site tap, fix flashing around roof of tank) to mitigate further contamination risk. Residual disinfection was present. Further resample was clear.

24/03/11 Wangaratta (Omaru Rd tank) E.coli : 18 orgs/100mL

“E.coli

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

Wangaratta – Victoria – Turbidity

2010/11: Wangaratta Turbidity 6.5NTU

2015/16  Wangaratta Turbidity 5.9NTU

2016/17  Wangaratta Turbidity 5.9NTU

Bushfires: In late February 2013, over 100 mm of rain fell at the head of the catchment over a short period which caused land slips and a major dirty water event. Turbidity levels of >30,000 NTU were recorded at the Bright offtake and >3,000 NTU a few days later at Wangaratta.

Chlorine-resistant pathogen reduction: Where filtration alone is used as the water treatment
process to address identified risks from Cryptosporidium and Giardia, it is essential
that filtration is optimised and consequently the target for the turbidity of water leaving
individual filters should be less than 0.2 NTU, and should not exceed 0.5 NTU at any time
Disinfection: A turbidity of less than 1 NTU is desirable at the time of disinfection with
chlorine unless a higher value can be validated in a specific context.

Aesthetic: Based on aesthetic considerations, the turbidity should not exceed 5 NTU at the
consumer’s tap.

Wangaratta –  Victoria – Iron

2015/16:  Wangaratta Iron 0.45mg/L

Based on aesthetic considerations (precipitation of iron from solution and taste),
the concentration of iron in drinking water should not exceed 0.3 mg/L.
No health-based guideline value has been set for iron.

Iron has a taste threshold of about 0.3 mg/L in water, and becomes objectionable above 3 mg/L. High iron concentrations give water an undesirable rust-brown appearance and can cause staining of laundry and plumbing fittings, fouling of ion-exchange softeners, and blockages in irrigation systems. Growths of iron bacteria, which concentrate iron, may cause taste and odour problems and lead to pipe restrictions, blockages and corrosion. ADWG 2011