Participate Palmy

Option 1: All treated wastewater is discharged to the Manawatū River, with improved removal of phosphorus and nitrogen

This option is the most similar to how we currently do things, with 100% of treated wastewater from the Wastewater Treatment Plant on Tōtara Road being discharged to the Manawatū River.

Photo shows illustration of treated wastewater discharged to the river.

Under this option, there’d be a significant upgrade to our treatment plant to improve the way we treat phosphorus, a chemical found in fertilisers, food and household cleaning products.

We’d look to move away from a chemical removal process and instead use a natural biological process. This would reduce costs and could improve the process.

We’d also improve our treatment of nitrogen, which gets into wastewater from urine. These contaminants come into the wastewater system from the city’s homes and businesses. We’d also move towards a natural process for removing nitrogen.

New innovative technology which uses less energy will be considered.

We’d expect to see a decrease in biosolids, which are the remainder of solid material that comes into our treatment plant.

Both phosphorous and nitrogen are nutrients that can negatively impact freshwater plants and animals when discharged at high concentrations.

The construction and operation of this option is well understood.

What we'd need to install or build

This option would require significant upgrades to the treatment plant, and the construction of a new wetland or land passage.


  • Lifetime cost: $285 million
  • Potential rate increase per year: $310
  • Total wastewater charge per ratable unit per year: $560