Trade-offs between water security and energy use: Lifecycle energy of water supply options in Paju, Korea

Despite net zero movement in Korea's water sector, comprehensive assessments of water-related energy in the region are lacking. Focusing on a water-stressed city with diversified water sourcing, this study evaluated both direct and indirect energy across the entire urban water cycle from abstraction to discharge and reclamation. By considering the energy embodied in pipelines and energy avoided from circular water use, this study compared the energy burdens and benefits of long-range piped water supply options (local supply and inter-basin import) and decentralized circular supply options (rainwater harvesting, greywater reuse, wastewater recycling, water loss reduction, water demand management). The results showed that conventional piped water supply options were still more energy-efficient than decentralized rainwater harvesting, greywater reuse, and some wastewater recycling options. In the case of Paju, advanced treatments required to provide high-quality industrial water made circular water options particularly less energy-efficient. The trade-offs between water security and energy use would be further strengthened in 2040, when the energy needs of the city's water supply increase by 27%. Expansion of the wastewater recycling would add 11% of the energy needs, whereas adoption of water-saving appliances in residential buildings decrease energy needs by 6%. For energy-efficient water management, Paju needs to consider adopting water demand management options, optimizing reclamation technologies and size, and harvesting renewable energy.