McConnell Dowell delivered one of the most advanced WWTPs in the country

McConnell Dowell completed the upgrade of the Pukekohe Wastewater Treatment Plant for Watercare.

In Joint Venture (JV) with HEB Construction Ltd, McConnell Dowell successfully completed the Pukekohe Wastewater Treatment Plant (WWTP) Upgrade on time and within budget despite the challenges of the COVID-19 Pandemic. 

The upgrade to Watercare’s WWTP involved converting it from a batch process using Sequence Batch Reactors (SBR) to a Continuous Flow Facility, doubling the capacity of the plant. 

The project was delivered in two Separable Portions, A involved the construction of:  

  • Inlet works 
  • Activated Sludge Reactor (ASR)  
  • Membrane Bio Reactor (MBR)  
  • Return Activated Sludge (RAS) pump station 
  • Permeate tanks and chemical dosing facility 
  • Ultra-Violet (UV) disinfection system 
  • ASR electrical and MBR Buildings 
  • Interconnecting pipework and electrical works 
  • Access bridge, road works and finishings 

Separable Portion B included:  

  • Decommissioning the old system, including two SBR tanks   
  • Construction of two Activated Sludge Reactor tanks 
  • Interconnecting pipework  

The Joint Venture performed the pre-commissioning works and supported Watercare, who carried out the commissioning works. 

All the work was carefully programmed so it could be completed safely within the confines of the existing site while the plant remained fully operational.  

The team undertook extensive value engineering at the start of the project, which saved $2M for the client before construction started. During construction additional saving were identified by applying learnings from Watercare’s Biological Nutrient Removal facility at the Māngere WWTP which the JV had also delivered. 

The innovations included using large diameter Polyethylene (PE) pipework rather than the specified fibreglass (FRP) pipe and knife gate valves instead of the ones specified which saved money and helped reduce the project’s carbon footprint.  

Find out more about the

Whole of site 3 wetlands in background 

 

Contact

Daniel Patten
Daniel Patten
Engineering Manager