An Australian sewage plant this April began using treated wastewater falling down a 60-meter (m) shaft to produce its own power. The unique 4.5-MW hydroelectric plant, installed as part of a A$150 million (US$124 million) upgrade to North Head sewage treatment plant (Figure 4), is one of three new units the New South Wales government is installing in Sydney Water’s water and sewerage networks.

4. Waste waterfall. Australia’s North Head Sewage Treatment Plant started up a 4.5-MW small hydro unit that harvests power from treated wastewater falling down a 60-meter shaft. The sewage plant, located on the North Head Peninsula at the entrance to Sydney Harbour, near Manly, serves a population of over one million people and treats about 300 million liters of flow a day. Treated effluent is discharged through a deepwater ocean outfall. Courtesy: Sydney Water

The new plant was built by WorleyParsons and Energetics and is supported by the New South Wales government’s climate change fund. Along with a methane gas cogeneration unit that was also recently installed, the North Head plant now generates nearly 40% of its own power.

Sydney Water is pioneering the plant in Australia, but it isn’t the first in the world to harness hydroelectricity from a wastewater plant. U.S.-based Aquarion Water Co. has launched a program that taps excess forces inside water pipes, using technology designed by New York alternative energy company Rentricity. That company’s Flow-to-Wire system relieves excess water pressure delivered to customers at elevations lower than the water source. The inherent pressure differentials are used to spin turbines to create power.

Most recently, a 225-kW system is being developed at a Los Angeles wastewater treatment plant. That project is being closely watched, because 19% of electricity produced in California is allocated toward treating and distributing water and wastewater, the company said in a recent press release. Another 30-kW system is being designed for a municipal water agency near Pittsburgh, and Rentricity is gearing up to start construction on an energy recovery installation within the Water Treatment Facility for the City of Keene, N.H.

Meanwhile, in a concept that is closer to the Australian plant, Washington State–based Hydrovolts has devised an “in-stream” hydrokinetic turbine for sewer and wastewater systems. That company’s “Flipwing” turbine uses a cross-axis design so that power can be harnessed even from water that is not clean. Hydrovolts, which says that three wastewater treatment plants in Washington, New York, and Oregon have inquired about the turbines, claims that the potential for small and micro hydropower at wastewater treatment plants is tremendous. The company points out that in the U.S. alone, there are some 16,583 wastewater treatment plants.