A mobile filtration system is being installed to remove "forever chemicals" from dams that provide drinking water for tens of thousands of people.
Elevated levels of PFAS chemicals were found in untreated water flowing into the Cascade water filtration plant in the NSW Blue Mountains in September, with tests revealing quantities more than one and a half times safe levels stipulated in Australian drinking water guidelines.
The plant treats water that supplies more than 50,000 people living in the Blue Mountains.
Sydney Water will spend $3.5 million upgrading the plant with a mobile treatment system to ensure the chemicals don't enter drinking water, the NSW government announced on Tuesday.
The plant will be operational by the end of 2024 as the state works to bring drinking water supplies into line with soon-to-be-updated national guidelines.
PFAS substances are a group of more than 15,000 chemicals resistant to heat, stains, grease and water, earning the nickname "forever chemicals" due to their inability to break down.
Their use has varied widely from firefighting foam to non-stick pots and pans.
The National Health and Medical Research Council drafted new drinking water guidelines in October, reducing the benchmark for the PFOA group of chemicals from 560 to 200 nanograms per litre based on cancer-causing effects.
One nanogram is about one drop in 20 Olympic-sized swimming pools.
PFOS guidelines would fall from 70 to four nanograms per litre based on the chemicals' effects on bone marrow, while new guidelines were set for the PFHxS and PFBS groups over thyroid concerns.
The council came under fire for the guidelines, which are significantly weaker than the near-zero requirement in the United States.
Sydney Water previously conceded its Cascade plant would need a major upgrade to meet the stricter standards as current levels of a subgroup of PFOS chemicals were up to three times the proposed incoming limit.
Water Minister Rose Jackson said all drinking water that met current guidelines was safe to drink.
"It is important that communities are confident in the knowledge that they have access to safe and secure water, and this new technology will help us in those efforts," she said.
"We will continue to support our water authorities across the state to deliver the highest quality drinking water to every home and business."
The mobile plant would purify water using granular activated carbon and ion-exchange resin technology, Sydney Water managing director Roch Cheroux said.
"This initiative reinforces Sydney Water's promise to deliver safe, clean, and reliable water to all our customers," he said.
"While PFAS treatment is still an evolving field, we are leading the way with new ideas, such as this one."
