Water and energy recovery: The future of wastewater in China.

China is increasing its use of non-conventional water sources - seawater desalination, surface water transfer and wastewater reuse - to meet demand. Getting and treating water from these sources generally requires more energy than is needed for local freshwater sources. This increases the cost and greenhouse gas emissions associated with water supply. It also leads us to the question: are alternative water sources necessary and, if so, which source should be preferred? Here we argue that reclaiming and reusing wastewater is often the least energy-intensive alternative source for water-scarce areas of China, particularly when energy present in wastewater is recovered during the process.