Wellington’s nearly $400m sewage sludge treatment plant makes progress

The new sewage sludge treatment plant in the suburb of Moa Point in Wellington has been named Te Whare Wai Para Nuku.

Construction began in May 2023, and is expected to be completed in June 2026.

It is being built by Wellington City Council joint venture construction partners HEB and McConnell Dowell Construction.

The plant would reduce the amount of sewage sludge created through the wastewater treatment process and turn it into a safe, reusable product, Wellington City Council project director Janet Molyneux said.

“We are building, what will be, a world-class facility that is going to be a game changer for the way that sludge byproduct of wastewater treatment is handled and dealt with in one facility, and in New Zealand,” she said.

She said the facility would reduce the volume of sludge created by 80 percent, and would reduce carbon emissions by 60 percent.

Currently, more than a million litres of sludge is piped 9km across the city to the Southern Landfill, where it is dewatered, and 40 to 50 tonnes is buried.

The new facility will use thermal hydrolysis and digestion and a thermal dryer to process sludge into a safe, non-odorous and stable product.

That product will have the potential to be used productively, including as a soil conditioner and fuel for industrial heat.     

HEB water and wastewater manager and project director Peter Hodgson said the process was popular across Europe, North America and Asia.

“There are about 110 plants with advanced wastewater treatment around the world, but this is the first New Zealand,” he said.

“As far as a single site, complex wastewater job, this would be one of the biggest in the last 20 years.”

McConnell Dowell construction manager Richard Atkin said the build has been “quite challenging”.

“It’s the first of its kind in New Zealand that’s been built, and it’s got a very high seismic loading, so the structure work is quite complex,” he said.

From August, a new levy will be introduced to all ratepayers to cover the $370 million cost of Te Whare Wai Para Nuku.