Clifton Sewage Treatment Plant Upgrade

About the project

Pensar was engaged in the design and construction for the upgrade of the existing earthen embankment settling lagoons and Clifton STP to enable future use and capacity for growth in the area, along with utilisation for a new recycled water irrigation scheme.


Clifton, Queensland

Client & Duration

Toowoomba Regional Council
November 2021 - August 2023

Project Scope

  • Class C recycled water irrigation system, including a total of 45Ha of land irrigated by three centre pivots at >200m radius, 2 x 250kL recycled water storage tanks, irrigation pump station, chlorine analyser system
  • New mains supply and new main switchboard
  • Upgrade of existing STP main switchboard and mains supply
  • New control system for the STP with integration to the existing legacy remote SCADA package
  • Flocculant dosing system for the primary influent and sodium hypochlorite dosing system for tertiary effluent


  • Upgrading the STP while it was operational, including keeping one lagoon online for effluent storage, and one as a standby in the event of peak wet weather flows. Shutdowns of the plant were kept to a maximum of eight hours during upgrades of the site power supply and cutting in a new inlet flow meter
  • Designing the process with many unknowns including introduction of a new RO waste stream mid-project, and no historic site data on effluent quality prior to the upgrades. Pensar collaborated closely with Toowoomba Regional Council and chemical suppliers to trial several different flocculants to ensure the selection was appropriate
  • Pensar ensured dust suppression measures were in place to ensure adjacent pastures were not affected, as they were being grazed by cattle


  • Our team took a holistic review of the concept design and ‘jar testing’ to validate the process train and select the most appropriate settling aid chemical
  • Interfacing with plant operators proved both effective and successful in the integration of new assets during the commissioning and handover phases
  • Successful planning of staged works ensured that the brownfield site works had minimal impacts on existing plant operations
  • Iterations to and progressive development of the concept design resulted in optimised solutions to achieve best value effluent quality

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