2005/12 + 2022: Gunbower (Victoria) – E.coli, Dichloroacetic Acid, Trichloroacetic Acid, Trihalomethanes, Colour

Gunbower (Victoria) – E.coli

15/11/22: • A routine sample collected from the Gunbower elevated tank and customer tap in the Gunbower WSL were positive for the presence of E. coli (tank 13 cfu/100mL, customer tap 19 cfu/100mL).
• The E. coli detection was most likely the result of contamination from a water carting supply hose.
• In response, a BWA was put in place for the town.

Corrective actions:
• The WTP tanks were booster chlorinated with hypochlorite solution.
• The elevated tank was emptied, and an inspection completed.
• A booster chlorinator trailer dosed hypochlorite solution just downstream of the elevated storage into the network.
• The raw water was assessed and was found to be back within the operational envelope for the water treatment plant, and this enabled recommencement of the operation of the WTP, eliminating the requirement to cart water.
• Water mains were flushed
• Sampling completed to confirming the drinking water was safe.
• Consulted with DH following review of sampling results information, enabling lifting of the BWA
• Communication was via media statements, SMS, social media, Vic Emergency App, Website, and some door knocking.

“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

Gunbower (Victoria) – Chloroacetic Acids

2005/6: Gunbower Dichloroacetic Acid 0.120mg/L

2010/11: Gunbower Dichloroacetic Acid 0.18mg/L

2011/12: Gunbower Dichloroacetic Acid 0.110mg/L

2005/6: Gunbower Trichloroacetic Acid 0.250mg/L

2009/10: Gunbower Trichloroacetic Acid 0.1mg/L

2010/11: Gunbower Trichloroacetic Acid 0.31mg/L

2011/12: Gunbower Trichloroacetic Acid 0.17mg/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

Gunbower (Victoria) – Trihalomethanes

2010/11 Gunbower THM’s 0.38mg/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

Gunbower (Victoria) – Colour

2011/12 Gunbower Colour 30 HU

Based on aesthetic considerations, true colour in drinking water should not exceed 15 HU.

“… Colour is generally related to organic content, and while colour derived from natural sources such as humic and fulvic acids is not a health consideration, chlorination of such water can produce a variety of chlorinated organic compounds as by-products (see Section 6.3.2 on disinfection by-products). If the colour is high at the time of disinfection, then the water should be checked for disinfection by-products. It should be noted, however, that low colour at the time of disinfection does not necessarily mean that the concentration of disinfection by-products will be low…