Joint media release: Waikato River water suppliers achieve compliance with arsenic standards
04 December 2024
Today, four water suppliers drawing water from the Waikato River have returned arsenic results that meet New Zealand's drinking water standards. The water suppliers are Waipā District Council, Hamilton City Council, Waikato District Council, and Watercare.
Steve Taylor, head of operations for the Water Services Authority – Taumata Arowai, expressed cautious optimism about the results: "The results have been heading in the right direction for several days and are now within the acceptable range.
“We’re pleased with how the water suppliers have been responding to the situation. It is a sign of the system working – in terms of the testing practices alerting water suppliers to an issue, and them working collaboratively to share information as it comes in," said Taylor.
He emphasised that there has been no threat to human health and the water has remained safe to drink throughout.
“All water suppliers are continuing their daily testing for the time being.”
Earlier today, Watercare gathered samples from the Waikato River and at each stage of the water treatment process. These samples will be sent to a specialist laboratory in Melbourne for analysis to confirm the species of arsenic present. The results, expected within seven to 10 days, will help determine the most effective treatment processes for its removal. This will enable the water companies to make informed decisions about tailoring existing processes and considering new ones.
Watercare will share its results with Taumata Arowai, Waikato Regional Council, and other water service providers so they can benefit from the information as well.
Meanwhile, Waikato Regional Council is considering a stepped-up water quality monitoring programme for the river over the next two years. Learn more below.
Waipā District Council update
- To be attributed to Waipā District Council
Drinking water arsenic levels get the all-clear
Levels of arsenic in drinking water from all three treatment plants in Waipā have returned to below Drinking Water Standards maximum acceptable values.
Yesterday evening’s results recorded 0.0078 and 0.0097 milligrams per litre from the two main treatment plants, down from 0.01 and 0.011 on Monday, and the original results of 0.0138 and 0.0145.
The Alpha Street plant results were 0.0078 milligrams per litre yesterday, down from 0.0117 on Monday.
The maximum acceptable standard for arsenic in New Zealand drinking water is 0.01 milligrams per litre.
Water services manager Karl Pavlovich said while the level drop is great news, the council will continue to test daily to ensure any further variation is captured.
“We’ll continue with our enhanced arsenic monitoring plan for the next few weeks and will also review our regular monitoring programme.
“We’d like to collect more data on both the source of the arsenic and how the effectiveness of our treatment can be improved,” Pavlovich said.
Waipā draws some of its water from the Waikato River, where naturally occurring arsenic levels are generated by geothermal activity and accumulated arsenic sediments within the hydro lakes along the river.
The Water Services Authority - Taumata Arowai and Health New Zealand have confirmed that drinking water with slightly elevated arsenic levels for a short period of time is unlikely to impact health. The limits in the New Zealand Drinking Water Standards are based on the level of risk from a lifetime of drinking the water.
Waikato District Council update
- To be attributed to Waikato District Council
Operational changes at Waikato District Council’s Ngaaruawaahia treatment plant have ensured arsenic levels in treated water sourced from the Waikato River are remaining within the maximum acceptable value (MAV).
This plant is the only one in the district that has recorded slightly elevated levels of arsenic in the drinking water supply during the past week.
After a test result of 0.011 mg/litre was recorded on Sunday, just above the 0.01mg/litre MAV under Drinking Water Standards, Watercare Waikato has adjusted the treatment process by introducing chlorine at the front end to optimise existing arsenic removal procedures.
This is working as test results since the change have measured 0.01mg/litre, 0.0061mg/litre and today’s result of 0.0081mg/litre.
Meanwhile, all test results from Waikato District Council’s Huntly and Te Kauwhata treatment plants have been well within the MAV, with today’s being 0.0054mg/litre and 0.0024mg/litre respectively.
Waikato District Council Waters Manager Keith Martin is pleased that operational changes at Ngaaruawaahia are showing plant improvement and a downward concentration of arsenic in the treated water.
“We have seen arsenic values fall below the MAV since Watercare Waikato made process changes over the weekend, and we will continue to monitor our plants on a daily basis.
“Our operations and maintenance contractor, Watercare Waikato, are also exploring other ways we can continue to improve the operation of the Ngaaruawaahia plant specifically and our other plants generally.
“It’s also been really useful all the different agencies coming together to share information and respond in a coordinated way, while having the reassurances of Taumata Arowai and the National Public Health Service about the safety of the treated water supplied to our communities.”
The arsenic level in treated water supplied by Watercare to residents in Tuakau and Pookeno also remains well below the MAV, with today’s result being 0.0064mg/litre.
Arsenic is a naturally occurring heavy metal found in the Waikato River. Some of it comes from the geothermal activity near Lake Taupō and other natural sources downstream.
Hamilton City Council update
- To be attributed to Hamilton City Council
Hamilton City Council testing has now shown three consecutive tests which once again meet the applicable Drinking Water Standards.
The Incident Management Team said the reporting trend is encouraging but monitoring and testing will continue.
Council’s water treatment plant specialists, with support from Watercare and an independent expert, have been responding to changes in the type of arsenic in the Waikato River. At all times Hamilton’s water remained safe to drink and for all normal use.
Watercare update
- To be attributed to Watercare chief operations officer, Mark Bourne
“Earlier today, we collected water samples from the Waikato River and at each stage of the water treatment process. These samples will be sent to a specialist laboratory in Melbourne for analysis to confirm the species of arsenic present.
“The results, which we expect to receive within seven to 10 days, will help us to determine the most effective treatment processes for removing it. They'll help us to make informed decisions in terms of tailoring existing processes and introducing new processes.
“We will share our results with Taumata Arowai, Waikato Regional Council and the other water service providers so they can benefit from the information too.
“I’d like to reassure everyone in Auckland that the water produced at the Waikato Water Treatment Plant is safe to drink. We’re testing on a daily basis and have only had one slightly elevated result on 25 November. Today’s result was 0.0064mg/l, well below the ‘maximum acceptable value' of 0.01mg/l.”
Waikato Regional Council update
- To be attributed to Waikato Regional Council
Long term arsenic study being considered for Waikato River
Waikato Regional Council is investigating the feasibility of stepping up its monitoring of the Waikato River over the next two years to improve understanding of the drivers of arsenic concentration and speciation.
The council routinely monitors water quality at 12 sites along the river, with field measurements and water samples collected monthly for testing of a wide range of physio-chemical and microbial parameters. The results are reported through the state of the environment report.
Testing of samples collected from a number of sites on the Waikato River between Lake Ōhakuri and Rangiriri last week found that total arsenic levels were within the normal long-term range.
While there had been a small increase in the amount of dissolved arsenic in the water, council scientists felt the current situation was likely due to a change to an alternative chemical form of arsenic – from arsenic (V) to arsenic (III) – which can be harder for treatment plants to remove.
Dr Mike Scarsbrook, Environmental Science Manager at Waikato Regional Council, says the council is investigating the feasibility of expanding the suite of testing on the Waikato River over the next two years.
“We believe a long-term study would enable us to gather the robust data needed to build on historical studies on arsenic in the Waikato River, including in hydro-lake sediments which are a known source of different forms of arsenic.
“It would give us a better picture of what’s happening in the river and perhaps get us to a point where we might be able to predict incidents, like the one we are experiencing, in the future.”
Dr Scarsbrook said a decision would be made on the long-term study over the coming weeks.
Meanwhile, further samples have been collected from the Waikato River over the past three days, as part of monthly monitoring, with the results to be available next week.
Current arsenic levels do not affect contact recreation activities in the Waikato River. However, people should always check the Land Air Water Aotearoa (LAWA) website for the latest Can I swim here? advice: lawa.org.nz/explore-data/waikato-region
Find out more