Symbiotic infrastructure systems facilitate deep decarbonization and efficient water use more than independent improvements in each type of infrastructure. Here we analyse strategies for bridging the coal power and wastewater treatment sectors in China by using sludge and reclaimed water from municipal wastewater treatment as alternative fuels and water sources for coal power generation. We develop a geodatabase covering ~2,400 coal-fired power plants and ~4,200 municipal wastewater treatment plants and conduct an integrated analysis using a customized optimization algorithm and life-cycle assessment. Such infrastructure symbiosis annually offers greenhouse gas (GHG) mitigation of 8.6 Mt CO₂ equivalent, equal to 29% and 0.28% of GHG emissions from the wastewater treatment and coal power sectors, respectively. The symbiosis annually conserves 3.0 billion m³ of freshwater, equal to 62% of freshwater consumption by the coal power sector, and provides annual cost savings of 7.5 (3.4–12) billion CNY. Hebei, Shandong, Henan, Jiangsu, Zhejiang, Anhui and Guangdong contribute ~50% of GHG mitigation and ~60% of both freshwater conservation and cost savings due to the proximity of coal power and wastewater treatment plants. Approximately 80% of carbon, water and economic benefits can be achieved via 32% and 44% of all the plant-level linkages for sludge co-combustion and water reuse, respectively. Infrastructure symbiosis provides promising opportunities for both environmental and economic benefits. Policies to boost the establishment of energy–water infrastructure symbiosis would cost-effectively facilitate the achievement of China’s climate and water targets.