Western Australia Water Minister Terry Redman announced last week that the State Government would move forward with the country’s first full-scale groundwater replenishment scheme using recycled water. According to Redman, the indirect potable reuse approach could supply up to 20 percent of Perth’s potable water supply within ten years. The city currently relies on seawater desalination for nearly half of its potable water supply.
Water Corporation, the state-owned supplier of water and wastewater services in Western Australia, recently completed a three-year groundwater replenishment trial at its Beenyup Wastewater Treatment Plant (WWTP) site at Craigie, in Perth’s northern suburbs. During the test, secondary effluent from the WWTP was polished using UF, RO and UV disinfection to produce water that met Australian drinking water guidelines. The water was then recharged into the confined Leederville aquifer at a depth of 120-220m (395-720 ft), where it was evaluated using a network of 22 monitoring wells.
Mark Leathersich, the general manager of Water Corporation Acquisition Group, told WDR that the program will be rolled out in stages to meet Perth’s population growth and water supply demands. “The first stage, planned for completion in June 2016, will cost $116 million and produce 7 billion liters of recycled water per year [5 MGD]. Stage Two is now planned to begin recharging in June 2018, producing 14 billion liters of recycled water [10 MGD]. Stage Three is planned to begin recharging in June 2022, and will produce 28 billion liters of recycled water [20 MGD].”
“Water from the advanced recycling plant will be injected into the deeper aquifers of the Gnangara groundwater system, where it is anticipated to remain for decades before it is abstracted,” he said. “The recycle scheme has a projected 75 percent recovery rate, and the concentrate and backwash water will be diverted back to the Beenyup WWTP and discharged via its ocean outfall.”
The project’s procurement strategy calls for the EPC and commissioning services to be provided through a competitive alliance, and the Water Corporation will engage a third party reviewer to assist in assessing and reviewing the detailed design as proposed by the project proponents.
Leathersich said, “We anticipate issuing a request for proposals [RFP] in mid-late August with a five-week response period. The RFP will detail the project scope and timing, together with criteria to be addressed.” He noted that contractors must be prequalified under the Contractor HSE Prequalification system, and construction is anticipated to begin in 2014, following a formal environmental and health approvals process.