Reducing Harbour Pollutants:
Whāngārei Waste Water Treatment Plant

After 26 years successfully managing waste water treatment for Whāngārei city, the local treatment plant was in need of some maintenance and a general upgrade.

Whangarei District Council asked us to address the capacity issues of its largest wastewater treatment plant, where high inflows during heavy rain events could lead to untreated sewage flowing into adjacent wetlands. We constructed a high level bypass UV disinfection system to ensure that even in extreme events, all effluent received treatment.

Key features included:

  • detailed project management across civil, structural, mechanical and electrical works
  • requirement for a broad range of skills and experience from a multi-disciplined team
  • significant interface with the ‘live’ plant, including co-ordination of shutdowns and management of specialist subcontractors and suppliers, together with testing and commissioning works
  • a contractor design for the chambers, the UV building, civil and structural works
  • modification to existing pipework and processes within the plant and upstream of the new disinfection unit
  • project management staff engaged electrical specialists to provide vital power and communication/control to the UV system main distribution board – to activate valves, penstocks, flow meters and ancillary equipment.

These successfully completed works have doubled the disinfection treatment capacity of the existing plant. This has ensured all water flowing into the wetlands and the Whāngārei Harbour, is subject to the UV disinfection process (which destroys harmful bacteria and other pathogens).