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Pines III Wastewater Treatment Plant

Rolleston, New Zealand

Project Execution Period

May 2017 – June 2018

Project Description

The Selwyn District Council’s Pines Wastewater Treatment Plant (WWTP) serves a growing population of approximately 50,000 distributed over the district’s main town of Rolleston, and several smaller towns and farms in Canterbury, south of Christchurch.

The Pines WWTP was originally completed in 2013 and comprises screening, conventional biological nutrient removal, ultraviolet disinfection and disposal by centre pivot irrigators onto adjacent land dedicated to treated wastewater disposal. It also incorporates solids treatment and handling processes comprising gravity thickening, aerobic digestion, dewatering and solar drying.

The Pines III WWTP Upgrade involves expansion of the existing plant to increase treatment capacity for the predicted population growth, and has been designed to increase the liquid stream treatment capacity and improve solids stream management.

Contract Value

NZ$7.8 million

Man-hours Planned


Scope of Work

As the principal contractor, Monadelphous is responsible for the supply of materials, plant, equipment and labour required for the construction, installation, testing and commissioning of the works, including:

  • Construction of a new bioreactor
  • Associated pumps, mixers, blower and aeration diffuser system
  • Installation of a second UV disinfection line
  • Extension of bio-solids drying facility
  • Upgrade of irrigation pump station
  • Additional site buildings
Highlights and Achievements
  • First wastewater treatment project in New Zealand, strengthening our capabilities in the New Zealand water industry