Where are we now?
A longlist of 26 options has been developed, focusing on the effects on the environment the treated wastewater will be discharged into. This is important to ensure we develop an option that works within the framework of the Resource Management Act. How the wastewater will be treated will be developed as the project progresses, depending on the final discharge location.
The 26 options can be grouped into seven categories:
- Discharge to land
- Discharge to river
- Combined land and river discharge
- Discharge to groundwater
- Ocean discharge
- Discharge to a water supply network
- Discharge to air (evaporation)
Council is working with technical experts to assess each option, and come up with a shortlist of options to explore even further.
Discharge to land
Land-based discharge involves discharging treated wastewater over a large area of land, or over a smaller land area, but with the wastewater being treated to a higher level before discharge.
Locations for doing this have not yet been explored, and some additional infrastructure would be required.
Discharge to river
This involves discharging all treated wastewater to the Manawatū River. This could be done either at the current location (Tōtara Road Wastewater Treatment Plant), at a new location south of Opiki Bridge, or the discharge could be split between these locations.
Variations of these are also being considered, with different ways of treating the wastewater depending on the river flow. In all cases, the wastewater would be treated above the treatment standards of the current wastewater treatment plant.
Combined land and river discharge
Combined land and river discharge would reduce the amount of land needed, with the remainder of the treated wastewater being discharged to the Manawatū River when it is in high flow.
The type of treatment facility required will depend on the final locations of the discharge.
Discharge to groundwater
Groundwater is naturally formed water that sits below the ground surface. High rate infiltration (soaking wastewater through the ground surface), and deep bore aquifer injection (deep below the ground surface), are both possibilities for groundwater discharge.
Depending on which areas are chosen, this may be difficult during winter when the ground is saturated from rainfall.
Ocean discharge on the west coast, or combining it with either land or river-based discharge is being looked at.
A location for this has not yet been identified, but would probably be at least 2km from the shore.
Because the wastewater would need to travel a reasonable distance before being discharged, additional storage and pipeline infrastructure would be needed.
Discharge to a water supply network
Discharging treated wastewater back into Palmerston North’s water supply network is being explored. Wastewater would be treated to an extremely high standard, and some would be discharged into the Manawatū River when wastewater flows are high.
Consideration will also be given to how the treated wastewater could be used – for example, some cities overseas use the water for industry. This type of wastewater management has not yet been implemented in New Zealand to the scale that would be needed for Palmerston North.
Discharge to air
Evaporating wastewater into the air is the final possibility.
While the main discharge would still be to the Manawatū River, evaporation could occur when river levels are very low.
Sustainability and innovation are being considered in all options
Council is also looking at ways of reducing our wastewater before it goes for treatment. This will be important as we assess what our future wastewater system might look like.
Got a specific question or would like to know more?
Phone: Customer Service 06 356 8199 (24 hours a day, seven days a week).