Thermal hydrolysis on the way for Watercare's Rosedale Wastewater Treatment Plant

Watercare is taking another important step to future proof Auckland’s wastewater system, ensuring the city can continue to grow while protecting public health and the environment.

An important upgrade to the utility’s Rosedale Wastewater Treatment Plant is a step closer, with the announcement of a new contract for technology that will significantly increase the plant’s capacity and resilience for decades to come.

Watercare has entered into a contract with Norwegian company Cambi to supply two thermal hydrolysis process systems for its Rosedale plant – a critical investment in long term planning for one of Auckland’s most essential pieces of infrastructure.

“Cambi is the preeminent supplier of thermal hydrolysis process systems globally, with a strong track record of delivering outcomes,” says Watercare programme director Rob Burchell.

“We’re excited to partner with Cambi to bring this transformative technology to our Rosedale plant.”

Wastewater treatment is an unseen but vital service that protects Auckland’s waterways, supports public health, population growth and enables housing. With demand set to rise significantly in the north of the city, Watercare is investing now to ensure the system can cope well into the future.

Thermal hydrolysis uses high temperatures and pressure to treat sludge created during the wastewater treatment process. The new $28 million system, due to be delivered in 2028, will allow Rosedale to treat more wastewater efficiently, without the need to build additional large infrastructure on site.

“We have four digesters at Rosedale. In about a decade, the wastewater flows coming to the plant will almost double when the Northern Interceptor wastewater pipeline is fully in service,” says Burchell.

“Thermal hydrolysis reduces the amount of digested solids so we won’t need to build another digester to cope with the increased flows. It reduces the solids produced by the plant and creates a pasteurised biosolid that can be used as a fertiliser.”

The technology will also increase biogas production, supporting Watercare’s efforts to reduce emissions and make better use of renewable energy produced on site.

“The increased volume of biogas will supply enough electricity to support the plant’s operation and potentially supply some electricity to the grid.

“Rosedale will be the country’s largest thermal hydrolysis facility when the systems are installed.”

The new thermal hydrolysis systems form part of a wider programme of upgrades at Rosedale, designed to support population growth, improve wastewater treatment outcomes, and reduce environmental impacts – helping ensure Auckland’s wastewater system remains reliable, resilient, and fit for the future.