Tirohanga Water Treatment Plant upgrade

Project overview

The Tirohanga water treatment plant has been upgraded to meet the requirements of the New Zealand drinking-water quality assurance rules.

In operation since mid-2025, the upgraded plant delivers numerous benefits to the Tirohanga community, including improved water quality and increased supply reliability.

The new purpose-built treatment plant includes a new chlorine contact tank and the building houses the following processes:

• New UV disinfection system
• Upgraded chlorine disinfection system
• New pH correction system to reduce water corrosivity

Significant civil enabling works were carried out as part of the upgrade, including adding pipelines to and from the new plant, while a major retaining wall was also needed.

An additional and final phase of the project will see the onsite turbine reconfigured to make use of hydropower, to reduce energy costs, with this work to be completed during 2026.