By Kody Cook, Journalist, Pump Industry Magazine

Western Australia’s largest water resource recovery facility (WRRF), the Woodman Point WRRF, is undergoing an upgrade which is set to greatly increase the facility’s capacity and its sustainability. Here, we delve further into the upgrade and take a closer look at the pumps and equipment that support the WRRF.

Water Corporation’s Woodman Point WRRF treats wastewater generated in Perth’s largest catchment area. In an effort to ensure the facility will continue to serve the area’s rising population in the years to come, works have already begun on a $238.5 million upgrade that will see the facility’s capabilities increase from its current 78t of dry solids per day (tDS/d) sludge treatment capacity.

Additionally, the upgrade seeks to enhance the facility’s sustainability credentials, with the addition of more onsite renewable energy generation.

Preparing for the future

According to Water Corporation’s General Manager – Assets Planning and Delivery, Evan Hambleton, sludge volumes were increased significantly by converting the facility from a batch treatment process to a continuous stream treatment process through an 180ML/d upgrade that occurred in 2019.

“To maintain the existing quality of treated wastewater and to cater for future growth within the catchment area, upgrades are required to ensure sludge treatment continues to meet biosolids classification standards for beneficial reuse,” Mr Hambleton said.

“This project will increase the existing solids load capacity of 78tDS/d to 120 tDS/d, which will provide capacity until 2040 and match the capacity of the liquid stream of 180ML/d.”

Work on this latest upgrade kicked off in mid-January 2024 and Mr Hambleton said that the design is 50 per cent complete and procurement is 35 per cent complete.

“Construction work to date includes bulk earthworks and service relocation. Preliminary work on the Dissolved Air Floatation Thickeners (DAFT) has also commenced.”

How does the facility work?

Mr Hambleton explained that wastewater is pumped into Woodman Point WRRF from Munster Terminal Pump Station.

“Wastewater from the catchment collects at this station and pumps to the ‘head of the works’. The wastewater stream is generally a gravity process through screens and various stages of settlement and aeration.

“The new upgrade consists of two streams of treatment for the solids stream, the Primary Sludge Stream, and the Excess Activated Sludge (EAS) stream.

“Pumps on the Primary Sludge Stream are generally of the Progressive Cavity/Helical Rotor design. These provide a measured consistent flow. The gentle nature of the pumping method ensures more efficient sludge thickening and dewatering.”

Mr Hambleton said that pumps on the EAS stream are usually dry mounted immersible pumps or end suction centrifugal pumps up to the DAFTs.

“Up to this point, the stream has a low solids content and behaves in a similar fashion to water – beyond the DAFT pumps is similar to the primary stream and will be progressive cavity pumps.

“Pumps on the EAS stream will be pumping sludge up to 16.5 per cent dry solids content. This presents some challenges, requiring methods to reduce friction losses in-line, including the use of injection rings to create a boundary layer along the pipe wall of either reclaimed wastewater, or polymer and injection of air pockets into the line to break the sludge cake into plugs along the transfer line.

“The heart of the new process is a Thermal Hydrolysis Plant (THP) on the EAS stream which processes sludge at high temperatures, providing the added benefit of a better rheology for pumping (a thicker hydrolysed sludge behaves like a thinner conventional sludge) and boosts residence time in the downstream digesters.

“The remainder of the process is conventional thickening and dewatering technology commonly used in the water industry (DAFT, Inclined Screw Thickening and Centrifuge Dewatering).”

Image credit: Water Corporation.

Expected outcomes of the upgrade

Water Corporation said that the project will support the organisation’s target of achieving net zero emissions by 2035.

The upgrade is expected to do this by:

  • Increasing the Woodman Point WRRF’s ability to treat organic matter by 54 per cent, allowing Water Corporation to produce higher quality biosolids in a more efficient way
  • Allowing the continued recovery of solid waste which supports Water Corporation’s state-wide target of 74 per cent solid waste recovered for reuse, as stated in its Waste Recovery Strategy
  • Allowing nearly 50 per cent of the facility’s energy requirements to be produced onsite through the capture and reuse of biogas
  • Reducing greenhouse gas emissions by around 5,600t CO₂-e annually as less grid power will be needed to run the plant
  • Contributing to a reduction in greenhouse gases by decreasing flaring, which will see the plant go from 54 per cent flaring to only flaring in emergency circumstances

“Now seen as a source of valuable resources, wastewater is treated and recycled as a fit-for-purpose resource to alleviate pressure on valuable scheme water supplies. This project will ensure we continue to maintain water supply to the Kwinana Water Recycling Plant which provides 16ML/d of high-quality recycled water to customers within the Kwinana Industrial Precinct,” Mr Hambleton said.

“This is especially important in Western Australia where the impacts of the climate are placing increasing pressure on drinking water supplies.

“In 2002-23, Water Corporation recycled 20 per cent of all wastewater treated across Western Australia. Water Corporation aims to recycle up to 35 per cent of all wastewater in the metropolitan area by 2035.”

Mr Hambleton said that this project demonstrates how a growth mindset and whole-of-business support can lead to positive outcomes in recycling a waste product into multiple sustainable resources and deliver a world-class Resource Recovery Facility to create a positive legacy for the broader community.

“This project is setting a new benchmark in the recovery of sustainable resources from wastewater.”

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