2017 23 August: – Katamatite (Victoria) – Trihalomethanes

Katamatite (Victoria) – Trihalomethanes

2017 23 August: Katamatite (Victoria) – Trihalomethanes 260μg/L (maximum)

Trihalomethanes Australian Guideline Level 250μg/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