Sydney currently recycles about 22 billion litres (GL) of wastewater each year. Through initiatives in the 2006 Metropolitan Water Plan, the city plans to ramp this up to produce 70 GL/a by 2015.

The Western Sydney Recycled Water Initiative is one of the measures proposed to secure Sydney’s water needs, by increasing the use of recycled water for residential, irrigation and environmental uses.

A key element of the Western Sydney Recycled Water Initiative is the Replacement Flows Project, which will see the Penrith, St Marys and Quakers Hill sewage treatment plants connected by pipes to allow treated wastewater from the three plants to be further treated at a new advanced water treatment plant at St Marys. The highly treated recycled water will be released into the Hawkesbury-Nepean River below Penrith Weir, substituting up to 18 GL/a of drinking water currently being released from Warragamba Dam into the Hawkesbury-Nepean River, with highly treated recycled water. This will conserve drinking water, whilst maintaining environmental flows.

The Deerubbin WaterFutures Consortium, consisting of United Group Infrastructure, McConnell Dowell and General Electric Betz, will work with Sydney Water to deliver this major water recycling project.

Work scope

The scope of the work will include the design, construction, operation and maintenance of a new plant and associated pipelines.

The new plant is an advanced water treatment plant, located at the existing St Marys Sewage Treatment Plant (STP) site, and will be used for the treatment of tertiary treated effluent from Quakers Hill, Penrith and St Marys STPs. The plant will produce up to 50 ML/day of highly treated recycled water using microfiltration and reverse osmosis processes. The treated water will be discharged to the Hawkesbury-Nepean River downstream of Penrith Weir and approximately 8 ML/day of concentrate (brine generated from the treatment process) will be discharged to the Northern Suburbs Ocean Outfall Sewer (NSOOS) located near Dundas. The scope of works also includes development of a storage pond at Quakers Hill STP, for the temporary storage of the concentrate.

Five pipelines will be constructed as part of the project, which include:

• A 7.6 km long 500 mm diameter pipeline, for the transfer of tertiary treated effluent from Penrith STP to the new plant, including construction of a new pump station and buffer storage within Penrith STP;
• A 12.3 km long 500 mm diameter pipeline, for the transfer of tertiary treated effluent from Quakers Hill STP to the new plant, including construction of a new pump station and buffer storage within Quakers Hill STP;
• A 7.6 km long 750 mm diameter pipeline, for the transfer of recycled water produced by the new plant to Penrith STP, including a new pump station and buffer storage within the new plant site and a new discharge structure at the effluent channel at Penrith STP;
• A 12.3 km long 375 mm diameter pipeline, for the transfer of concentrate from the new plant to Quakers Hill STP, including new pump station and buffer storage within the new plant site; and,
• Transfer of the concentrate to the NSOOS, via a combination of utilising 7 km of an existing 300 mm diameter pipeline and a 12 km long section of new 375 mm diameter pipeline, between Quakers Hill STP to Vineyard Creek at Dundas.

The scope of works also involves operation and maintenance of the new advanced water treatment plant for ten years. In addition, Sydney Water will have the option to extend the term by up to ten years.

Project progress

Since the project was awarded in August last year, the consortium team have been working to design a wide range of major components, from the pilot plant, to the sewerage treatment plant, the advanced water treatment plant and the pipelines. The pilot plant was installed at the St Mary’s STP in mid-April and commissioned in late April, demonstrating the recycled water quality that the full size plant will produce.

The pipeline route has been confirmed after considerable survey, service identification and stakeholder consultation, whose requirements have been accommodated wherever possible.

The route survey demonstrated the need for a number of trenchless crossings. The consortium plans to undertake these by horizontal directional drilling or boring, depending on local restrictions and ground conditions. These crossings traverse large arterial roads, creeks and rail easements.

Mid-April also saw the start of line pipe deliveries. The pipeline component of the works is scheduled to be complete by mid-2009 and the whole plant ready for operation by March 2010.