One of Australia’s largest water utilities, Seqwater, recently contracted Zinfra to complete three separate contracts at their Capalaba Water Treatment Plant.

The water treatment plant at Capalaba, in the suburbs between Brisbane and the Gold Coast, required upgrade work to their ageing infrastructure to ensure the quality of their water for future generations, and the safe operation of their facility.

The main challenge for Zinfra was the brownfield nature of the plant. Normal construction techniques had to be changed and shutdown methodologies developed to ensure limited impact to the day to day operation of the plant.

Zinfra Project Manager Spencer Walmsley said, “It has been great to be part of a project that increases the efficiency of the treatment plant and the water quality for the local community.”

Managing the challenges

“Developing strategies to deliver our services, while limiting impact to operations, has been at times a difficult task, but it has made the project more rewarding,” said Mr Walmsley.

In order to reduce shutdown times from over a week to just three days, and ensure Seqwater could continue to meet customer demand, temporary isolations at the inlet and outlets to the raw water pumps allowed time to install, align and pre­-commission the new pumps prior to introducing them to plant operation.

By isolating one of the two operating clarifiers and filters, a significant portion of the scope of works could be completed while the system was still operating, including the DN700 replacement interconnecting pipework to connect both clarifiers to a single filter.

Taking the filter and clarifier offline also allowed for the removal of the filter’s media and refurbishment of the internal walls and equipment within the filter prior to re­-installing the replacement filter media.

With one filter taken offline a method was also developed to allow for the installation of the new filter outlet and below ground works, including removal and replacement of the filter building to house two new UV reactors (duty/standby).

By taking a staged approach to the work, only two single shutdowns were required to allow for pipework replacement at the downstream chemical dosing chamber.

While this work was undertaken, the operational filter could temporarily maintain the magflow and ultrasonic flow meters including pH, pressure differential and turbidity to ensure water quality and the accuracy of fluoride and chlorine dosing could be monitored by the operations team.

Due to the age and various upgrades over the years, the site has an assortment of equipment and pipework within it.

One of the major challenges for Zinfra involved accessing and determining correct flange sizes, and verifying flange orientations and alignments, along with actual pipework sizes.

Many variables were found when completing this important verification process which ensured that Zinfra was able to fabricate, order and change its equipment and methodologies to suit.

Introducing innovation

Clients like Seqwater rely on service providers to bring specialised skills and knowledge to bear on their projects and operations. Zinfra has delivered a number of cost and time savings to the client through smart thinking and clever, collaborative problem solving.

During the tender process, Zinfra suggested reducing the depth of the new clear water storage tank scour line to connect two tanks together.

The design depth of the line was on average 2.5­-3 metres deep, but by reducing this depth Seqwater benefited in the form of cost savings from increased productivity, and Zinfra reduced their exposure to high risk activities posed by trenches deeper than 1.5 metres.

Zinfra also identified the proposed design alignment required the removal of a number of significant eucalyptus trees, which would need relevant local government approvals.

After investigation, Zinfra altered the design, reducing the overall length of the service from 140 metres to 115 metres and also aligned with an existing road, removing the need for tree removal.

The projects incorporated a number of chemical dosing system upgrades including alum dosing, polymer, sodium hydroxide and lime.

The upgrades, to make the plant more efficient, moved the current dosing points to new locations or through the in­-pipe static mixers, installed as part of the works.

Zinfra identified an opportunity to reduce the footprint of a new polymer dosing system that was to be installed in the old PAC dosing storage building, by providing a tank­on­tank batching system, coupled with the three off­dosing skids.

This concept change provided Seqwater with a designated area for an emerging works project, either an acid flush system for lime or an upgrade to its service water system.

Off the back of these innovative solutions, Seqwater charged Zinfra with designing a new service water system, controlled by a pressure loop for the plant, to ensure that a 3.5­-6.0 bar water pressure is maintained to service the increased demand of the polymer system, resolving some existing lime and chlorine batching and dosing issues.

Delivery of the three projects at Seqwater’s Capalaba Water Treatment Plant represented a significant opportunity for Zinfra to showcase their capability in the water treatment plant sector.

Zinfra has shown they can problem solve and work nimbly to produce cost effective, safe outcomes for their clients.

This partner content is brought to you by Zinfra. For more information, visit

Lauren brings a fresh approach to content. While she’s previously written for publications as diverse as Australian Geographic, The Border Watch and Girlfriend, she’s found her true passion in her current role as an editor in the world of energy and infrastructure trade magazines.

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