Sydney Water is Australia’s largest water utility, providing water, wastewater, recycled water and some stormwater services to more than 5.4 million people in the Greater Sydney, Blue Mountains and the Illawarra. WaterNSW operates the state’s dams, captures and stores water and supplies it to utilities like Sydney Water for filtration and distribution.
Reducing PFAS levels at Cascade Water Filtration Plant
When Per- and Polyfluoroalkyl substances (PFAS) were detected in the source raw water supplying the Cascade Water Filtration Plant (WFP) in the Blue Mountains, about two hours west of Sydney CBD, Sydney Water moved quickly to respond to community concerns.
Although the drinking water produced at Cascade WFP met the Australian Drinking Water Guidelines, Sydney Water evaluated how to reduce the slightly elevated PFAS levels in the filtered drinking water. The team aimed to ensure continued compliance with current guidelines and proposed updates expected in 2025.
Rapid deployment of a mobile PFAS treatment system
When PFAS was detected in mid-2024, WaterNSW isolated Medlow Dam and Greaves Creek Dam as a precaution and sourced raw water from Oberon Dam, which showed no PFAS detection, to supply Cascade WFP.
Although PFAS levels remained low and within drinking water guidelines, Sydney Water reconfigured the system to supply the Blue Mountains primarily from another WFP. At the same time, the team began evaluating PFAS treatment options.
Sydney Water contacted Onterris and quickly turned an initial introduction into a collaborative effort to design and deliver a mobile PFAS treatment system at Cascade WFP.
The Onterris team committed to a rapid response and launched design, procurement and fabrication of the system. Team members worked 12-hour shifts seven days a week to bring the system online. The General Manager and key Australian team members relocated full time to the project site to keep delivery on track. The team mobilized the site in late November 2024 and brought the system online in January 2025.
The project succeeded because of the people behind it. Engineers in Australia and the U.S. worked as a continuous 24-hour team, solving challenges overnight in the U.S. so teams could implement solutions on site the next day. Sydney Water provided strong technical, operational and project management support to guide design and integration with the existing WFP. Sydney Water also retained Onterris to operate the system for up to 12 months.
A trusted partner
Since coming online in January 2025, the system has treated approximately six million liters of water per day. Sydney Water continues to supply safe drinking water that meets current and proposed Australian Drinking Water Guidelines.
This project reinforces Onterris as a trusted partner and PFAS expert for water utilities across Australia. It demonstrates what happens when dedicated teams come together to solve a client’s challenge.