2013/14 – Mt Isa (Queensland) – Cyanobacteria, Lead, Trihalomethanes

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Mt Isa (Queensland) – Cyanobacteria

Exceedance of Blue Green Algae Incident Description: On 27 September 2013 the Blue Green Algae (BGA) result from Clear Water Lagoon (S12), a natural filtration storage, was 276,638 cells/ml and the toxic cell, Cylindrospermopsis raciborskii , was 144,914 cells/ml.


Mt Isa (Queensland) – Lead

2013/4: Mt Isa (Queensland) – Lead

Detection of Lead Incident Description: On 18 September 2013 a scum was sighted on the surface of the South tank (sample point S19). A sample was taken for contamination analysis. Metal analysis resulted a positive detection of lead at 0.023mg/L. The sample analysed was not part of the routine sampling and the location where the sample was taken is not representative of the monitoring plan. Another exceedance of lead was received on 03 March 2014 at South tank (S19) with result of 0.021mg/L.

Lead Australian Drinking Water Guideline 0.01mg/L

“… Lead can be present in drinking water as a result of dissolution from natural sources, or from household plumbing systems containing lead. These may include lead in pipes, or in solder used to seal joints. The amount of lead dissolved will depend on a number of factors including pH, water hardness and the standing time of the water.

Lead is the most common of the heavy metals and is mined widely throughout the world. It is used in the production of lead acid batteries, solder, alloys, cable sheathing, paint pigments, rust inhibitors, ammunition, glazes and plastic stabilisers. The organo-lead compounds tetramethyl and tetraethyl lead are used extensively as anti-knock and lubricating compounds in gasoline…

Mt Isa (Queensland) – Trihalomethanes

Incident Description: On 12 November 2013 results for Total Trihalomethanes (TTHM’s) in storage tanks: West tank (sample location S17), South tank (sample location S19) and MIM front
main (sample location S31) were 0.261mg/L, 0.326mg/L and 0.266mg/L respectively. All three
results exceeded the ADWG health guideline limit of 0.250 mg/L. Further occasions of exceedance in Total Trihalomethanes were noted on the 10 April, 12 May and 02 June 2014. The Regulator advised that the incidents were to be included in the open incident DWI-7-00030


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