Sydney Water Dewatering Upgrade Programme, Australia

Improving the integrity and efficiency of Sydney Water's dewatering process

Aurecon uses digital tools to optimise standardisation of Sydney Water dewatering process.

Built in stages from the early 1900s, Sydney’s wastewater treatment plant infrastructure has evolved over the decades as the city’s population expanded. With its population anticipated to reach nearly 6.5 million by 2030 (from five million in 2017), additional pressure will be placed on wastewater treatment plants and their dewatering facilities.

Dewatering is the removal of water from solid material or soil by wet classification, centrifugation, filtration, or similar solid-liquid separation processes.

Aurecon was appointed as part of a joint venture to complete the concept and detailed designs to improve the integrity and efficiency of the dewatering facilities at eight of Sydney Water’s wastewater treatment plant sites. The plants currently treat approximately 60 000 tonnes of biosolids per annum, which is expected to increase to 85 000 tonnes annually in the next 25 years, due to population growth.

Solids generated by the sewerage treatment process are dewatered to reduce the wet volume and effectively manage the disposal costs of a hazardous material. The programme aims to improve the dryness quality by two per cent, which will reduce the total volume transported for hazardous waste disposal by between 5 000 and 6 000 tonnes per annum.

This programme secures the future of each facility to be able to effectively and safely dewater the expanding volume of biosolids due to population growth and minimise disposal costs by improving dewatering efficiency.

The challenges to overcome

A creative approach was implemented to standardise the upgrade of dewatering infrastructure at the wastewater treatment plants. Standardisation was important for the following reasons:

  • Bulk supply of proprietary plant for upgrade works
  • Simplifying storage of spare parts for the future
  • Consistency of future maintenance and operation

A standardised approach to the upgrades made good sense for the joint venture, but there were significant challenges to overcome:

  • Differing infrastructure – the dewatering infrastructure had been installed over different decades with differing equipment and installation methods
  • Site-specific layouts – each site layout is different as it was based on the land size and orientation, and the equipment it could accommodate
  • Stakeholder needs – the operators at each site had varying operating and maintenance procedures with different needs and wants for their site

The joint venture had to consider the disparate site conditions and stakeholder needs to be able to design standardised equipment, processes and construction methods.

A series of stakeholder workshops and working group forums challenged the designs and methodologies to contribute feedback to the final standardisations.

Reviews undertaken at the eight plants enabled the team to define repeatable solutions that could be common to all the sites in order to achieve the disposal cost savings and efficiencies that Sydney Water was seeking. This was accomplished using a three-step process: challenge need; challenge configuration; optimise configuration.

How innovation solved the problem

As part of the joint venture’s programme to develop the detailed design for the upgrades, digital engineering tools were used to propose systems that emphasised standardisation of methods and equipment.

The innovative application of digital engineering enabled:

  • Standardisation and modularisation across multiple sites
  • De-risking of project delivery by understanding the impact of the design on existing assets in a brownfield environment through the use of digital engineering tools
  • Enhanced 3D design reviews showing existing and new assets overlaid to obtain support from stakeholders
  • Estimation of quantities optimised from digital data
  • Reduction in the likelihood of design rework during the construction phase
  • A database of equipment specifications and layout to support operations and maintenance of the facilities in the future

To accommodate the different site sizes and orientations, laser scan surveys were taken and the data was used to generate a point cloud model. The set of data points that was collected was used to create 3D models of each site for a multitude of visualisation, rendering and customisation applications.

Technology selection

Technology selection was rationalised based on the customisation of layout and design in 3D. For example:

  • The selection of low-shear technologies for dewatering where odour had been highlighted as an issue
  • The use of sliding frame silos to reduce sludge working
  • Implementation of recuperative thickening to increase digester solids retention time
  • Conveyor selection and layout design

Physical configurations

The digital approach modelled layouts to achieve the same physical configuration of plant facilities at each site. A standard skid type approach was developed for thickening processes so that access for operation and maintenance will allow interchangeability between plants and a regional approach to maintenance.

Historically, thickening and dewatering systems have manual interventions to allow control. The upgraded dewatering facilities will have a fully automated system with standard equipment controls that tie back to a coordinated central plant control system.


3D models were used to communicate with stakeholders, many of whom don’t have a technical background. They were able to visualise and interact with the 3D models in one-to-one scaled realistic environments. Using visualisation gave clarity and meaning, allowing stakeholders to fully understand the programme and provide feedback on the design of the facilities and equipment. The visualisations helped to bring the programme to life.

The joint venture’s bespoke delivery design and methodology offers Sydney Water true value-for-money through standardisation and optimisation of upgrades for their dewatering facilities.

As Sydney faces continuing population growth, the security and efficiency of its wastewater treatment plants will become ever more important and this programme has delivered future reliability of the dewatering infrastructure at key sites in Sydney Water’s network.

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