A water sample mixed with high solids (4040mg/L) alongside a sample with 33mg/L.
A water sample mixed with high solids (4040mg/L) alongside a sample with 33mg/L. Graham Lancaster

Doubt cast on CSG water tests

FRESH scrutiny has cast doubt on CSG wastewater test results released earlier this week by Lock the Gate Northern Rivers.

The group released data on Wednesday from a Metgasco holding pond showing levels of heavy metals well above guidelines for drinking water and safe environmental standards.

Yet data from the sample analysis, which was tested at SCU's NATA-accredited laboratory, show an unusually high level of sediment.

It contained 4040mg/L of suspended solids, while the Metgasco sample released last week contained a more typical 33mg/L.

Australasian (ANZECC) guidelines for metal content in solids are typically 100 to 1000 times more lenient than water - and this should be taken into account in the testing regime.

The crucial disparity between the two samples highlights the common issue of sample bias, said director of the SCU Environmental Analysis Laboratory Graham Lancaster.

"In every bit of science there's bias, so sample collection is often more important than analysis results," he said.

"If you want to test sediment, you test it separately and apply the relevant environmental guidelines, which are a thousand times higher."

Mr Lancaster said results of Wilsons River water - with river sediment mixed at 4040mg/L - would be likely to give similar results as the anonymous sample.

But senior advisor to the National Toxics Network Marion Lloyd-Smith said long-term pesticide and diesel fuel usage had contaminated the Wilsons River and it should not be used as an example of a clean water system.

"The historical contamination of rivers in this area in well known - but that's not an excuse to add more," she said.

"Once you put these sorts of contaminants in the system, especially heavy metals, they don't go away."

"Regardless of how the sample looks, that water will still go to the sewerage plant, and no sewerage plant can take out heavy metals."



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