2017/18: Pine Rivers North (Queensland) – Trihalomethanes, Chloroacetic Acids

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Pine Rivers North (Queensland) – Triahlomethanes

“The typical concentration of THMs in all of Unitywater’s drinking water schemes is well below 0.25mg/L. However in an isolated event, two sample results in the Pine Rivers North scheme exceeded the health guideline in March 2018. At the time, the area’s water was supplied by Seqwater’s Petrie Water Treatment Plant which was near the end of its working life. This plant was decommissioned in April 2018 and the Pine Rivers North scheme is now connected to the South East Queensland water grid meaning a repeat occurrence is very unlikely.” Unity Water 2017/18

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

Pine Rivers North (Queensland) – HAA’s

2017/18: Max Result 124 ug/L, av: 77ug/L, 95th Percentile 118ug/L

Australian Guidelines Trichloroacetic Acid 0.100mg/L, Dichloroacetic Acid 0.100mg/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…