Low Energy Consumption SWRO
Clean Technology 2008

Low Energy Consumption SWRO

R.L. Stover
Energy Recovery Inc., US

desalination, energy recovery device, SWRO

The 143,000 cubic meters per day seawater desalination plant in Kwinana Beach (Perth), Western Australia started up in November 2006. A year later, it remains the largest seawater reverse osmosis (SWRO) desalination plant in the Southern Hemisphere and the second largest SWRO plant in the world. Built by Suez Degrémont and Multiplex Engineering Pty Ltd., the plant supplies approximately 17% of Perth’s water supply, supplementing conventional freshwater resources which are in very short supply. The plant was designed for maximum energy efficiency and minimum greenhouse gas emissions. It operates with twelve seawater reverse osmosis (SWRO) trains in the first pass, each with a production capacity of 13,350 cubic meters per day. Six high-pressure pumps on a common manifold or “pressure center” supply a portion of the high-pressure seawater fed to the SWRO trains. The remainder of the high-pressure seawater is supplied by arrays of ERI PX-220 energy recovery devices. The plant’s hydraulic design was intended to provide for cost-effective operation over a wide range of flow and pressure conditions, thereby maximizing operational flexibility. To offset greenhouse gas emissions, the plant is entirely powered with electricity generated by a wind farm. After a year of continuous production, the Perth plant has exceeded the designer’s expectations. The energy consumption of the first pass SWRO train is approximately 2.2 kilowatt hours per cubic meter (kWh/m3). The total energy consumption for the plant is 3.2 to 3.5 kWh/m3 including intake, pretreatment, both RO passes, post-treatment, potable water pumping to a reservoir 13 km away. This is the lowest power consumption ever reported for large-scale SWRO. The author describes the design and operation of the Perth plant as a new standard for seawater desalination. The benefits of alternative processes and equipment, including foreseen technological advances, are contemplated to set expectations for further energy reduction in SWRO.