China’s mega-desalination plant experience
The gap between fresh water supply and demand is steadily widening in the People’s Republic of China, home to approximately 20% of the world’s population. Demand for water supplies continues to grow as both personal and industrial consumption surges. Underground water resources, meanwhile, are already overused and badly polluted, and the deep wells now being drilled are frequently tapping into arsenic-rich aquifers, posing safety risks to as much as 30% of the country’s population.
To help combat shortages, desalination, in the form of sea water reverse osmosis (SWRO), has become an integral part of China’s long-term water management strategy. Historically used on a small scale, desalination is now becoming more widely accepted for large-scale water production, particularly in highly populated coastal areas. In recent years, China announced plans to grow its desalination capacity to 2.2 million m3/d (581 million GPD) by 2015, and Chinese water authorities formed partnerships with global water treatment companies to construct large SWRO facilities.
So far, this initiative has resulted in the construction of the nation’s two largest SWRO plants — the Qingdao and Tianjin Dagang SWRO desalination facilities. Designed, constructed and operated by Abengoa and Hyflux, respectively, the two plants together add 200,000 m3/d (52 MGD) of installed capacity to China’s water network. Half of that comes from the Tianjin facility, which began delivering desalinated water to the northern China city’s industrial zone in July 2009. Three years later in eastern China, Qingdao’s municipal water supply began receiving a comparable amount of water from the new SWRO plant there. Both of these state-of-the-art facilities use the latest desalination technologies, including rotary-type isobaric energy recovery devices (ERD).
By considering not only initial capital expenses, but also operational and maintenance expenses, material alternatives and expected uptime of the Energy Recovery System (ERS), these plants demonstrate how sustained long-term energy efficiency can be achieved in large-scale SWRO plants. By displaying proper system design and energy recovery device (ERD) selection, both mega-plants provide an excellent model for future desalination projects in China.