2016/17 – Marian (Queensland) – Lead, Chloride

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2016/17 – Marian (Queensland) – Lead

Patricia Cct

A concentration of 0.0126 mg/L for lead was reported for a sample collected from ‘Mirani 2 – Patricia Cct’ on 5 September 2016. This result was initially flagged as exceeding the ADWG health value of 0.01 mg/L and was therefore reported as a drinking water incident. Upon review of this incident it has been identified that this concentration did not in fact exceed the guideline when comparing the result once rounded to a precision level of one significant figure (0.01
mg/L) (as per guidance stipulated in page 165 of the ADWG).

Re-analysis of the original sample returned a lead concentration of 0.0085 mg/L. The re-sample results (for a sample collected from Mirani 2 – Patricia Cct on the 12 September 2016) returned a lead result of <0.001 mg/L.

Re-analysis results confirmed the original result was not due to analytical error and was unlikely to be due to contamination of the original sub sample at the laboratory. The original and re-analysis results indicate that the sample tap may have deteriorated prior to sample collection and contributed to the high lead result in the sample.

No corrective actions were taken as there was deemed to be no risk to public health.

Alice Street

A concentration of 0.0442 mg/L for lead was reported for a sample collected from the Mirani 1 – Alice Street drinking water sample point on 11 May 2017. This result exceeds the ADWG health value of 0.01 mg/L.

Re-analysis of the original sample returned a lead concentration of 0.0415 mg/L. The re-sample results (for a sample collected from the Mirani 1 – Alice Street sample point on the 8 May 2017) returned a lead result of <0.0005 mg/L.

Re-analysis results confirmed the ADWG health guideline exceedance. It was expected the original exceedance was the result of tap degradation. Following identification of the exceedance arrangements were made to replace the sample point tap with a brass tap.

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…ADWG 2011

Marian (Queensland) – Chloride

2016/17: Marian (Queensland)  Chlorides 301.95mg/L (max), 29.77mg/L (av.)

“Chloride is present in natural waters from the dissolution of salt deposits, and contamination from effluent disposal. Sodium chloride is widely used in the production of industrial chemicals such as caustic soda, chlorine, and sodium chlorite and hypochlorite. Potassium chloride is used in the production of fertilisers.

The taste threshold of chloride in water is dependent on the associated cation but is in the range 200–300 mg/L. The chloride content of water can affect corrosion of pipes and fittings. It can also affect the solubility of metal ions.

In surface water, the concentration of chloride is usually less than 100 mg/L and frequently below 10 mg/L. Groundwater can have higher concentrations, particularly if there is salt water intrusion.

Based on aesthetic considerations, the chloride concentration in drinking water should not exceed 250 mg/L.

No health-based guideline value is proposed for chloride.” 2011 Australian Drinking Water Guidelines