2007/11 + 2019: Cohuna (Victoria) – E.coli, Trichloroacetic Acid, Dichloroacetic Acid, Trihalomethanes, Turbidity, Manganese, Taste & Odour

Dec 2019 – Cohuna (Victoria)

Poor water quality in Cohuna


Coliban Water says it is experiencing poor raw water quality in Gunbower Creek – the supply source for the Cohuna Water Treatment Plant.

“Customers may notice a change to the taste and odour of the town drinking water as a result,” the company said in a statement posted to its Facebook page.

“There are no health risks associated with the town water supply. It is safe for all drinking, bathing and food preparation purposes and it continues to comply with all health-based guideline values in the Australian Drinking Water Guidelines.

“Treatment measures are in place to minimise the impact to the town drinking water supply. However, until raw water quality improves we are unable to completely remove the taste and odour impacts. We will provide residents with further updates as needed.”

Cohuna (Victoria) – E.coli

26/7/11 Cohuna E.coli  1/100mL Reticulation


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

Cohuna (Victoria) – Trichloroacetic Acid/Dichloroacetic Acid

2009/10 Cohuna (urban) Dichloroacetic Acid 0.092mg/L

2010/11 Cohuna (urban) Dichloroacetic Acid 0.13mg/L

2009/10 Cohuna (urban) Trichloroacetic Acid 0.100mg/L

2010/11 Cohuna (rural) Trichloroacetic Acid 0.22mg/L

2010/11 Cohuna (urban) Trichloroacetic Acid 0.14mg/L

(Australian Guideline Trichloroacetic Acid: 0.1mg/L)

“Chloroacetic acids are produced in drinking water as by-products of the reaction between chlorine and naturally occurring humic and fulvic acids. Concentrations reported overseas range up to 0.16mg/L and are typically about half the chloroform concentration. The chloroacetic acids are used commercially as reagents or intermediates in the preparation of a wide variety of chemicals. Monochloroacetic acid can be used as a pre-emergent herbicide, dichloroacetic acid as an ingredient in some pharmaceutical products, and trichloroacetic acid as a herbicide, soil sterilant and antiseptic.” Australian Drinking Water Guidelines – National Health and Medical Research Council…

There are no epidemiological studies of TCA carcinogenicity in humans. Most of the human health data for chlorinated acetic acids concern components of complex mixtures of water disinfectant by-products. These complex mixtures of disinfectant by-products have been associated with increased potential for bladder, rectal, and colon cancer in humans [reviewed by Boorman et al. (1999); Mills et al. (1998)].” Ref: tmp/Trichloroacetic acid (TCA) CASRN 76-03-9 IRIS US EPA.htm

Cohuna (Victoria) – Trihalomethanes

2010/11 Cohuna (rural) THM’s 0.32mg/L

2010/11 Cohuna (urban) THM’s 0.31mg/L

Trihalomethanes Australian Guideline Level 250μg/L (0.25mg/L)

The raw water at Katamatite is sourced from the Murray Valley Channel irrigation system which is managed by Goulburn Murray Water. Normal operation of this channel system involves the

shutdown over the winter period with no water available, GVW is required to fill the storages prior to the shutdown of the irrigation system and is reliant upon storage until irrigation water becomes available. At the time of the exceedance the raw water levels in the onsite storages were low due to this shutdown period and sourcing water over winter from the storage. The low raw water storage levels resulted in a higher concentration of dissolved organic matter within the storage, which increased the chlorine demand. Shortly after the exceedance GVW were able to access water in the irrigations system, improving the water quality and reducing the levels of organic matter present. All subsequent resamples were below the health limit.”

Why and how are THMs formed?
“When chlorine is added to water with organic material, such as algae, river weeds, and decaying leaves, THMs are formed. Residual chlorine molecules react with this harmless organic material to form a group of chlorinated chemical compounds, THMs. They are tasteless and odourless, but harmful and potentially toxic. The quantity of by-products formed is determined by several factors, such as the amount and type of organic material present in water, temperature, pH, chlorine dosage, contact time available for chlorine, and bromide concentration in the water. The organic matter in water mainly consists of a) humic substance, which is the organic portion of soil that remains after prolonged microbial decomposition formed by the decay of leaves, wood, and other vegetable matter; and b) fulvic acid, which is a water soluble substance of low molecular weight that is derived from humus”. US EPA

2007/11 – Cohuna (Victoria) – Turbidity

2007/8 Cohuna (rural) Turbidity 17NTU

2010/11 Cohuna (urban) Turbidity 6.7NTU

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

2007/08 – Cohuna (Victoria) – Manganese

2007/08 – Cohuna (Victoria) – Manganese 0.77mg/L

Manganese: ADWG Guidelines 0.5mg/L. ADWG Aesthetic Guideline 0.1mg/L
Manganese is found in the natural environment. Manganese in drinking water above 0.1mg/L can give water an unpleasant taste and stain plumbing fixtures