2007/18 – Yealering (Western Australia) – Triahlomethanes, Iron, pH

Yealering –  Western Australia – Trihalomethanes

2016/17 Yealering (Western Australia) Trihalomethanes 0.270mg/L (max), 0.203mg/L (mean)

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

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

Yealering –  Western Australia – Iron

2007/08: Yealering (Western Australia)  – Iron 0.65mg/L (Highest level only)

2008/09: Yealering (Western Australia)  – Iron 0.42mg/L (max), 0.29mg/L (mean)

2016/17 Yealering (Western Australia) Iron 0.34mg/L (max), 0.21mg/L (mean)

2017/18 Yealering (Western Australia) Iron 0.34mg/L (max), 0.17mg/L (mean)

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

Yealering (Western Australia) – pH (alkaline)

Average pH: 2007 July-2008 June: 9.33 pH units

Average pH: 2008 July-2009 June: 8.82 pH units

Average pH: 2008 July-2009 June: 8.97 pH units

2010/11 Yealering (Western Australia) pH 8.91 (av)

2011/12 Yealering (Western Australia) pH 8.97 (av)

2013/14 Yealering (Western Australia) pH 8.87 (av)

2014/15 Yealering (Western Australia) pH 9.41 (av)

2015/16 Yealering (Western Australia) pH 9.15 (av)

2016/17 Yealering (Western Australia) pH 9.06 (av)

2017/18 Yealering (Western Australia) pH 8.65 (av)

Based on the need to reduce corrosion and encrustation in pipes and fittings, the pH of
drinking water should be between 6.5 and 8.5.

New concrete tanks and cement-mortar lined pipes can significantly increase pH and
a value up to 9.2 may be tolerated, provided monitoring indicates no deterioration in
microbiological quality.

pH is a measure of the hydrogen ion concentration of water. It is measured on a logarithmic scale from 0 to 14. A pH of 7 is neutral, greater than 7 is alkaline, and less than 7 is acidic.

One of the major objectives in controlling pH is to minimise corrosion and encrustation in pipes and fittings. Corrosion can be reduced by the formation of a protective layer of calcium carbonate on the inside of the pipe or fitting, and the formation of this layer is affected by pH, temperature, the availability of calcium (hardness) and carbon dioxide. If the water is too alkaline (above pH 8.5), the rapid deposition and build-up of calcium carbonate that can result may eventually block the pipe.