Molendinar Water Treatment Plant Upgrades

Completion Date: June 2017

Managing and maintaining ageing infrastructure is one of the most common challenges facing the utilities and infrastructure sector. In a recent multifaceted work project, operator Seqwater sought to address functionality and safety issues relating to old infrastructure at its Molendinar Water Treatment Plant (WTP).

The Molendinar WTP, built in 1983, is part of the SEQ Water Grid. It supplies drinking water to most of the Gold Coast and also supplements supplies in Logan and Brisbane when needed. The two clarifiers at Molendinar WTP are standard units that contain two main mechanical components: a rake system used to remove the clarified sludge from the bottom of the clarifier and a mixer and drive unit that assists in the flocculation system of the clarifier. The drive unit on Clarifier 1 was due for refurbishment and the rake was in poor condition and potentially in need of replacement. As a result, Seqwater requested an assessment and refurbishment of the rake and mixer mechanisms on Clarifier 1.

The drive units were able to be removed and transported to Practical Engineering’s 4,800m2 facility, incorporating workshop and hardstand alongside office space. From here, the rake and mixer drive mechanisms were inspected and refurbished before being re-established at Molendinar WTP.

In addition to this functionality issue, Seqwater pursued a solution to a Workplace Health and Safety (WHS) issue relating to the backwash and sludge storage tanks at Molendinar WTP. In order to provide a safe work environment for staff and meet current WHS standards, Seqwater was required to complete extensive safety documentation and manage operational disruptions, incurring time and financial costs to the business.

The existing infrastructure had a central bridge structure supporting the drive units for the respective mixers and a walkway allowing operators to service the drive units and clean the tank. However the walkway extended only half way along the structure forcing operators to enter the tank in order to clean the side furthest from the bridge.

Acknowledging the operational and safety costs of the existing design, Seqwater sought a walkway solution with safety handrails that would allow operators to perform cleaning and maintenance of the entire sludge storage and backwash water tanks efficiently, without the need to enter the tanks.
The Practical Engineering Utilities and Infrastructure team proposed a design that integrated the existing walkway bridge structures while allowing for egress around the drive unit and motors in order to facilitate safe access to all mechanical components.

Practical Engineering is a multidisciplinary team consisting of mechanical fitters, boilermakers, design and project managers and engineers. The company’s unique capacity to combine design, analysis, certification, drafting, project management, manufacture, installation and commissioning meant that Practical could offer Seqwater a complete end-to-end solution for both elements of this project.

All works were designed and implemented in accordance with the applicable sections of the relevant Australian Standards and Seqwater Standards and inspected, tested and commissioned by Practical’s highly qualified RPEQ and NER qualified engineers.