Only one of Waikato District Council’s water treatment plants recorded slightly elevated arsenic levels in treated water, test results showed today.

A sample of treated water submitted this week from the Te Kauwhata plant showed a reading of 0.0054 mg/litre, well within Drinking Water Standards for arsenic levels of 0.01mg/litre. 

A sample of treated water submitted this week from the Huntly plant showed a reading of 0.0089 mg/litre, within Drinking Water Standards for arsenic levels of 0.01mg/litre. 

Watercare Auckland also received an improved result from its plant near Tuakau, which supplies Pookeno and Tuakau.

The 0.0081 milligrams per litre result in a sample taken yesterday is also within the maximum acceptable value under the Drinking Water Standards.

But a slightly elevated reading of 0.012mg/litre was received from Ngaaruwaahia water treatment plant, and was consistent with previous test results shared by Hamilton Council (0.0115) and Watercare (from its plant near Tūākau – 0.011). 

Despite the slightly elevated reading, treated water from the Ngaaruawaahia plant remains safe to drink.

Waikato District Council Waters Manager Keith Martin said the reason why test results varied was likely due to the fact the treatment plants operate differently.  

“As of tomorrow, we will start injecting chlorine at the front end of the treatment process at the Ngaauawaahia plant as part of our operational changes to our water treatment plants to improve water quality if, or when needed, as a result of sample tests,” he said. 

“We are working very closely with regulators, the Water Services Authority - Taumata Arowai to ensure that we are responding appropriately to ensure the provision of safe drinking water to our community.” 

Watercare Waikato is currently taking daily samples for testing from all plants that draw water from the Waikato River. 

Meanwhile Hamilton City Council’s latest sampling of treated water showed the water remains safe to drink, with arsenic levels consistent with previous elevated readings. The sample showed a test result for arsenic of 0.0123 milligams per litre of treated water.

Head of operations for Water Services Authority - Taumata Arowai, Steve Taylor, says he is confident that the drinking water suppliers are responding appropriately to reduce the level of arsenic in the supply by adjusting their treatment processes. 

“We are monitoring the situation closely and will continue to work with the drinking water suppliers to ensure they are taking appropriate steps to manage and resolve the issue.”  

And National Public Health Service regional clinical director Dr William Rainger says that people who drink treated water sourced from the Waikato River do not need to be alarmed.

The limits in the New Zealand Drinking Water Standards are based on the level of risk from a lifetime of drinking the water.  

“Drinking water with slightly elevated levels for a short period of time is unlikely to impact people’s health.  

“You do not need to boil your drinking water. It is safe to drink.”  

And New Zealand Food Safety’s deputy director general Vincent Arbuckle says the levels detected are not harmful to animals.

"There is no evidence water used for animals or food production is unsafe. If there was a risk to food safety we would take appropriate action to protect consumers, including recalls." 

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