2006/17 + 2020/21 – Big Hill Bendigo (Central Victoria) – E.coli, Iron, Ammonia

Big Hill Bendigo (Victoria) – E.coli
19/2/07: Big Hill (Victoria) 1org/100mL. (sample at tank outlet)
No known cause – possibly due to low chlorine residual or bird entry. All possible entry points to the tank sealed. Sodium hypochlorite added to tank (5 mg/L). Re-sampling completed showing no further E.Coli.

31/12/11 Big Hill E.coli  1/100mL

2013/14 Big Hill E.coli  1/100mL (98.1% samples no e.coli ) (1 positive)


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

Big Hill Bendigo –  Central Victoria – Iron

2016/17: Big Hill (Victoria)  – Iron 0.37mg/L (Highest level only)

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

2020/21: Big Hill Bendigo  (Victoria) – Ammonia

2020/21: Sample collected from the Big Hill treated water storage tank returned a result for ammonia exceeding the  aesthetic guideline value (0.5 mg/L) of the ADWG on one occasion. This water sampling locality is supplied from the Bendigo WTP and water is disinfected by chloramination.
One of the issues associated with the use of chloramination as a disinfection process is the potential for  nitrification to occur within distribution networks, which can contribute to an increase in ammonia in drinking  water. Therefore, the short-term spike (one sample) in the ammonia concentration observed at the Big Hill  tank could have been attributed to nitrification in the distribution network.

Based on aesthetic considerations (corrosion of copper pipes and fittings), the concentration
of ammonia (measured as ammonia) in drinking water should not exceed 0.5 mg/L.
No health-based guideline value is set for ammonia.

“…Most uncontaminated source waters have ammonia concentrations below 0.2 mg/L. High concentrations (greater than 10 mg/L) have been reported where water is contaminated with animal waste. Ammonia is unlikely to be detected in chlorinated supplies as it reacts quickly with free chlorine. Ammonia in water can result in the corrosion of copper pipes and fittings, causing copper stains on sanitary ware. It is also a food source for some microorganisms, and can support nuisance growths of bacteria and algae, often with a resultant increase in the nitrite concentration.” ADWG 2011