• Installation of Principal supplied gravity drainage decks, thickened WAS pumps, Macerator WAS pumps and digested sludge pumps
• Pipework installation (WAS feed to GDDs, TWAS feed to digester No.1 and digested sludge feed to centrifuges)
• Re-purposing of the existing Rotary Drum Thickeners (RDTs) to thicken primary sludge and modifications to the limed sludge pump station to facilitate duty/duty operation of the two existing dewatering centrifuges
• Repurposed A-Train WAS Pump Station
• New B-Train WAS Pump Station
• Existing DAF tank demolition
• Configuration and mounting of the new GDD’s, support structures, piping, access and maintenance platforms
• New GDD shelter
• Polymer dosing system modifications
• New service water supply to the GDDs
• Modifications to allow re-purposing of RDTs for primary sludge thickening, including odour control
• Electrical upgrade scope
• New switchboards
• PLC and SCADA modifications
• Major equipment interconnections
• Pre-commissioning, Wet-commissioning, Control system commissioning, Process commissioning, Performance proving trials, and Capacity proving trials

The project is being delivered under brownfield conditions, with various underground services dating back 20-30 years that may not be very reliable. Abergeldie and Unitywater are currently undertaking an extensive investigation to identify live and redundant services. The team will also use non-destructive, vacuum excavation where possible to mitigate any possible risks.

The existing STP will remain operational to minimise disruptions and continue servicing the community. There may be a few times during the works when existing areas of the STP may need to be turned off when Abergeldie and Unitywater will ensure that either a bypass is installed, or the loss of operational hours is kept to an absolute minimum to avoid any unnecessary disruptions.

Other challenges include repurposing existing equipment to treat primary sludge, which will involve rerouting pipework and recommissioning/reengineering the equipment to perform the new task.

To accommodate the towns growing population and increased capacity demand, Abergeldie and Unitywater improved the sludge thickening reliability and capacity, renewing and upgrading the ageing bio solids handling infrastructure and reducing ongoing maintenance costs.