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Residents in one of Auckland’s oldest suburbs cannot drink water for several more years from a local aquifer due to traces of a banned chemical.

Watercare “temporarily” shut down the Onehunga water treatment plant two years ago before incoming drinking regulations.

Tests, conducted for four years before the new regulations came in in November 2022, showed levels of poly-fluorinated alkyl substances (PFAS) above the incoming maximum acceptable levels for the chemical.

PFAS are manufactured chemicals used in things like cosmetic products, non-stick cookware, and water-resistant clothing.

Research by Auckland University released this year found that the country’s drinking water is largely free of PFAS, but urged caution and regular testing of water.

A move by Environmental Protection Authority meant NZ became one of the first countries in the world to ban PFAS - dubbed “forever chemicals” - in cosmetic products from 2027 to protect people’s health and the natural environment.

Watercare chief strategy and planning manager Priyan Perera said since 2022, the council’s water company has been exploring options for treatment technologies that remove PFAS from drinking water.

He said a comprehensive upgrade of the Onehunga plant is needed to ensure it can remove PFAS, and targeting 2027 for a completion date.

“The upgraded plant will use granular-activated carbon filtration, which has proven to be successful at removing PFAS and is commonly used in places like Australia and the United States.

“It will also include a fluoridation upgrade, and UV treatment to provide additional barriers for disinfection and protozoal removal,” said Perera.

He said the $41 million project will soon progress to the design stage.

Steve Taylor, head of operations for the country’s water regulator Taumata Arowai, said Watercare is responsible for monitoring water quality and has a responsibility to ensure the drinking water they supply is safe.

He said Watercare plans to meet with Taumata Arowai to discuss the next steps before starting the process of bringing the treatment plant and water source back into service.

Watercare has temporarily closed the Onehunga water treatment plant so it can continue to consistently meet the new drinking water regulations that take effect next month. Map / Watercare

The Onehunga aquifer in Spring St is one of Auckland’s oldest water supplies which came into operation at the turn of last century.

The aquifer supplies water to Onehunga, surrounding suburbs and industrial areas, and feeds into the city’s wider network.

About 18 months before the water treatment plant was shut down, Watercare spent $2m boosting its output in response to the city’s drought in 2020.

The upgrade took it from 20 million litres a day (MLD) to 24MLD, and included new pumps and pipes to draw water from the aquifer, and new filtration units.

Since the shutdown in 2022, Onehunga and surrounding customers have been supplied with water from Watercare’s main metropolitan network containing fluoride.

Onehunga residents fought off many attempts over the years to fluoridate the local water.

In 2022, the then Director-General of Health, Sir Ashley Bloomfield, directed Watercare to fluoridate the area’s water by June this year.

Watercare said at the time, “The decision to shut down the plant simply brings that forward”.

- NZ Herald