ETP Post Ozone Contact Tanks - Aqua Metro Pty Ltd
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ETP Post Ozone Contact Tanks

ETP Post Ozone Contact Tanks – Design and Installation of Internal Pipe Joint Seals

Small Scale Capital Program


Melbourne Water


Eastern Treatment Plant

Key Sector

Water and Sewer

Contract Type

Design and Construction


8 Months
October 2019 to June 2020

Key Facts

  • The Eastern Treatment plant is a MWC tertiary treatment.
  • The tertiary treatment utilises ozone as an oxidising and disinfecting agent in the Post Ozone contactor (POC) tanks.
  • The POC tanks comprises of a rectangular reinforced concrete tank, approximately 8m deep, 4.5m wide, and 70m long.
  • Each POC tank contains an inlet pipe (2m diameter) and 4 ozone injector pipelines (150mm diameter) with an access hatch in the roof of the tank.


  • Intermittent detection of ozone gas leaks were observed on the external side of the POC tank. Further investigation identified the potential source of the leak from the inlet pipe flange adaptor couplings.
  • Given ozone is an extremely hazardous gas, the containment of ozone and water tightness of the Post Ozone Contactor Tanks is a mandatory requirement for the safe operation of the POC tank facility. Aqua Metro Services therefore was engaged to carry out remedial works.
  • Some other remedial works on adjacent pavement and injector pipe block-outs were also carried out simultaneously which further bolstered the containment of ozone gas.

Scope of Service

The scope of works included the following:

  • Design and installation of a flexible internal seal to the inlet pipe joint of both POC Tank 1 and POC Tank 2 (2m diameter pipelines).
  • Selection of flexible joint seals material compatible with ozone gas exposure.
  • Rehabilitate and seal the ozone injector pipework block-outs in the tank wall in both tanks.
  • Pavement mapping to determine the extent of voids under the slab.
  • Under slab grouting of voids under the concrete pavement on north side of POC tanks.
  • Maintain Class A Recycled Water (partial) treatment during the works.
  • Testing to demonstrate no ozone gas leaks from pipe coupling.
  • Submission of As Built drawings and asset information.


  • A trial installation was performed in dry condition to improve safety outcomes and delivery time for project.
  • All personnel on site were fully inducted and trained to respond to any possible leak of ozone gas.
  • Performed works with divers to eliminate risks of confined space entry, fall from heights and manual handling.

Stakeholder Engagement

  • All works were carried out in coordination with Operations team at Eastern Treatment Plant and Major Capital Delivery team to ensure partial shutdown was effectively and safely managed.
Original Construction - north end of POC Tanks detailing inlet pipes (2m dia) and injector block-outs