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Nature Calls

We are making good progress with work on Nature Calls – Palmerston North City Council’s wastewater management project, and one of the largest projects we have ever undertaken.

Reviewing how the city best manages, treats and discharges wastewater is an extensive process. Ensuring we considered all the practicable options before narrowing the list gave us a wide range of options to assess, and we are now looking at six options in more detail, before the best practicable option is selected late next year.

What has happened already this year?

Earlier this year, a longlist of 26 options for how we manage, treat, and discharge wastewater was developed by technical experts with input from stakeholders. These options were grouped into seven categories, based on the type of environment treated wastewater would be discharged into – land application, discharge to river, combined land and river discharge, discharge to groundwater, ocean discharge, discharge to a water supply network, and discharge to air.

A robust assessment and testing process considered a number of environmental, cultural, economic and social factors, and options from each group have been selected to make up a shortlist of six options.

The shortlist

Council wanted to retain a broad range of options to develop further. The six shortlisted options involve discharging treated wastewater to a range of environments – the Manawatū River, land, groundwater, and the ocean.

Five options involve applying most of the treated wastewater to land, with the remainder being discharged to either the Manawatū River, groundwater or the ocean. These options will involve shifting where part or all of the city’s treated wastewater is discharged.

One option will discharge all treated wastewater to the Manawatū River, with the wastewater being treated to a higher standard than it is currently. To recognise Māori cultural values, all 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.

The options are (in no particular order):

  • Discharging all 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 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 when the river flow rises above intermediate levels.
  • Applying treated wastewater to land, with discharges to the Manawatū River in exceptional circumstances.
  • Applying some 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 groundwater levels are very high.
  • Discharging most treated wastewater to the ocean, and applying some to land. This would require a pipeline and other infrastructure to move the treated wastewater to a coastal discharge point.

What happens now?

During the next 12 months, Council will investigate the shortlisted options in more detail, to understand the type of treatment required for each. A consultation process will occur in early 2020, and Council will confirm the best practicable option in late 2020.

Got a specific question or would like to know more?

Read more about this project.


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