News & Events

River, land, groundwater and ocean wastewater options being explored

Monday June 24 2019

Discharging treated wastewater to the Manawatū River, land, groundwater, and the ocean are among six options for managing, treating and discharging Palmerston North’s wastewater in the future.

Council today confirmed that six options will be investigated in more detail as part of its Nature Calls project, before the best practicable option is confirmed in late 2020.

Nature Calls is one of the largest projects Palmerston North City Council has undertaken, and will investigate, consult with stakeholders, and help make decisions about how Council will manage, treat and discharge wastewater in the future.

Palmerston North City Council’s Chief Infrastructure Officer, Tom Williams, said that when selecting a shortlist, Council wanted to retain a broad range of options to explore further.

“This is an important project for Palmerston North – our city’s population is growing and the value being placed on our environment is high,” Mr Williams said.

“We are investigating six options that involve discharging treated wastewater to a range of different environments, to allow us to determine the best practicable solution for our city.

“One option will discharge all treated wastewater to the Manawatū River, while five involve applying some treated wastewater to land, with the remainder being discharged to either the Manawatū River, groundwater, or the ocean,” Mr Williams said.

“We are working closely with iwi, and to recognise Māori cultural values, any discharge to the Manawatū River will first pass through a wetland or land passage system. This reinforces the importance of the earth in cleansing the treated wastewater before it enters the river.”

Earlier this year, a longlist of 26 options for how wastewater could be managed, treated and discharged was developed, and after a robust assessment and testing process six options have been selected to make up the shortlist.

The assessment process considered the impact options may have on the natural environment, public health, Māori cultural values, social and community considerations, financial implications, resilience, technology, and the ability for the city to grow and develop.

Consultation will begin in early 2020, and Council will confirm the best practicable option in late 2020. A new discharge permit will be applied for by June 2022.

Background information

The six shortlisted options are (in no particular order):

  • Discharging all of the city’s treated wastewater to the Manawatū River at the current Tōtara Road Wastewater Treatment Plant discharge point. The wastewater would be treated to a higher standard than that achieved through the current wastewater treatment plant.
  • Discharging treated wastewater to the Manawatū River at the current Tōtara Road Wastewater Treatment Plant location when the river is in high flow, and at a new discharge point south of Opiki Bridge when river flows are lower. Some wastewater would be applied to land when flows in the Manawatū River are at their lowest.
  • Applying treated wastewater to land, with discharges to the Manawatū River in exceptional circumstances.
  • Applying treated wastewater to land, with discharges to the Manawatū River when the river flow rises above intermediate levels.
  • Applying some of the city’s dry weather wastewater to land, with the remainder being discharged to groundwater via high rate infiltration (soakage) through the ground surface. Further assessment will consider whether some wastewater should be discharged to the Manawatū River when the level of groundwater is very high.
  • Discharging most of the city’s treated wastewater to the ocean, and applying some to land. This option would require a pipeline and other infrastructure to move the treated wastewater to a coastal discharge point.