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With concerns about higher-than-normal arsenic levels in samples of Auckland and Waikato’s treated water, the government water regulator will announce the most recent test results this afternoon.
Elevated levels of the toxic heavy metal have been detected in treated water sourced from the Waikato River.
The WaterServices Authority, Taumata Arowai, told the Herald it was expecting to release the results of tests done yesterday, a spokeswoman said.
The results should provide clarity for authorities about the cause.
Waikato Regional Council environmental science manager Mike Scarsbrook said there were several possible reasons for elevated levels of arsenic in the treated water.
“It’s going to take a bit of time to dig into that. We’ll know more when we get the results from the detailed sampling taken yesterday. We’re hoping to see those results today,” Scarsbrook said.
“Then we can start to understand what might have changed.”
Scarsbrook said it was possible the higher-than-standard arsenic levels could be due to “a change in the [chemical] form” of the metal in the water.
“So, [possibly] more dissolved arsenic rather than what is bound to particles.
“We do know that at times, particularly in the summertime, we can see elevated levels of dissolved arsenic coming from sediments in the bottom of the hydro lakes and along the river.”
He explained that Waikato Regional Council tested samples of (untreated) river water, while Hamilton City Council and Watercare (in Auckland and parts of Waikato) tested samples of the water they treated.
Govt briefed, arsenic levels explained
The Government was briefed on Wednesday evening and sought assurances that water supplies are safe.
Watercare is also rejigging the way it processes water to reduce the amount of arsenic in the city’s water supply but said there was no immediate concern to public health.
Elevated readings of arsenic have been recorded in the Waikato River. Photo / Doug Sherring
Steve Taylor, head of operations at Water Services Authority Taumata Arowai (WSA), told Newstalk ZB water supplies in Auckland and Hamilton were affected.
He said there was “naturally a level of arsenic” in the river, but it had been notified levels had increased recently.
“I’m not sure what the reason for that increase is and that is affecting water supplies in Auckland and Hamilton,” he said.
He explained the maximum acceptable value for arsenic is 0.01mg a litre – an “incredibly low amount” – but there had been levels around 0.013mg, which is “marginally above the acceptable value for drinking water”.
“The level of arsenic is above what we’ve described as a maximum acceptable value, but it’s not at a level that we would suggest has a significant health effect.
”We’ve contacted the [Waikato] regional council to try and understand what is the reason for this change in source water,” he said.
Local Government Minister Simeon Brown has been briefed on the issue. Photo / Mark Mitchell
Local Government Minister Simeon Brown said he had been briefed on the issue by the WSA on Wednesday evening.
“I have asked the WSA to ensure that water suppliers in Auckland and Hamilton are taking appropriate steps, and that they communicate with their customers,” Brown said.
“The WSA is the lead agency for this issue and will be providing regular updates.”
Watercare reduces production at Waikato Water Treatment Plant
The Herald repeatedly sought comment from Watercare on Wednesday afternoon and it responded shortly before 8pm, saying it had reduced production at its Waikato Water Treatment Plant since detecting the elevated result.
Watercare chief executive Mark Bourne said the Waikato River supplies about 20% of Auckland’s drinking water.
”We treat the water at our Waikato Water Treatment Plant in Tūākau and distribute it throughout the metropolitan network.
”In most parts of Auckland, treated water from the Waikato River is blended with treated water from our dams. However, Pukekohe, Buckland, Clarks Beach/Waiau Pā, Patumahoe, Glenbrook Beach, and Drury south receive water solely sourced from the Waikato River.”
Bourne said Watercare had increased production at its major Ardmore plant, which treats water from four dams in the Hūnua Ranges.
“This extends the processing time at the plant, and we expect it to improve our ability to reduce the level of arsenic in the treated drinking water.
“We’re working closely with other agencies and will continue to share information as we learn more.”
The current minor exceedance of the standards does not present any immediate concern for public health, Watercare said.
A Waikato District Council spokesperson said Watercare operates the local water networks in the area under contract.
“Pōkeno and Tūākau are supplied by Watercare’s Waikato Water Treatment Plant. There are also treatment plants that serve the townships of Huntly, Te Kauwhata, Meremere, Taupiri and Ngāruawāhia.”
The spokesperson said samples from these plants were being tested, with results due today.
Hamilton City Council’s water supply remained safe for drinking, bathing, cleaning and cooking, following test results that showed small increases in the level of arsenic present.
What is arsenic?
The Health New Zealand Te Whatu Ora website describes arsenic as a substance found in rock, which in some situations “harms your health”.
It commonly enters the body in food and water and people can swallow small amounts every day for a long time without any obvious health effects.
