Can China reduce energy for water? A review of energy for urban water supply and wastewater treatment and suggestions for change

Energy use represents one of the main costs in water supply and wastewater treatment in China and is also a major contributor to greenhouse gas emissions. This paper has two aims. Firstly, it presents the first complete review of the growing body of literature on energy for water in urban China. Secondly, it identifies the most feasible suggestions for reducing and recovering energy in China's urban water systems based on the literature. The review finds wastewater is the area with most potential for net energy and emissions reduction. Anaerobic sludge digestion is commonly used in thousands of plants across the world, but it is applied in fewer than 3% of Chinese wastewater treatment plants. Many Chinese plants are large enough to make anaerobic digestion feasible and could potentially offset around 50% of their energy use by using the heat and power produced by burning biogas. Energy recovery can be increased through co-digestion and increasing primary sludge collection, or by using heat pumps to transfer energy in wastewater to nearby buildings. Land application of sludge can be used to significantly cut greenhouse gas emissions associated with wastewater sludge, almost all of which is currently landfilled or dumped without stabilisation in China. In water supply, minimising water leakage and increasing the efficiency of water pumping in high-rise buildings are practical ways to reduce net energy use for conventional water supply. In cases when water is scarce and cannot be transferred between provinces using gravity, wastewater reclamation combined with energy recovery is the least energy-intensive alternative water source and should be supported by strong government policy.