Intensified coupling of regional water and energy efficiencies by wastewater treatment-coal power infrastructure symbiosis

Abstract

Inadequate coupling between interdependent and interacting water and energy systems impairs both resource efficiency and attainment of sustainable development goals. Wastewater treatment-coal power infrastructure symbiosis has proved to offer potentials for water and energy savings, and greenhouse gases (GHG) mitigations, which is crucial for integrated water-energy co-management. However, how such infrastructure symbiosis facilitates to enhance regional water and energy efficiencies and thus consolidate water-energy synergy remains unclear. Based on an integrated water-energy network, the total factor water and energy efficiencies and their historical trajectories during 2006–2023 in 30 Chinese provincial regions are examined employing super-efficient Slack-Based Measure (SBM) model, with the coupling of efficiencies evaluated. The water-energy-environmental-efficiencies co-benefits of the infrastructure symbiosis and efficiencies coupling enhancement are explored through comparing a baseline scenario and a new symbiosis scenario (incorporating enhanced coal-sludge co-combustion and water reuse). Results show a progressive improvement in regional water and energy efficiencies, with their annual average coupling degree escalating from 0.19 to 0.35, although significant regional imbalance persists. In conjunction with a reduction of 5.80 million tons of coal, 1.39 billion m³ of freshwater use, and 16.77 million tons of CO₂-equivalent, the infrastructure symbiosis can facilitate a maximum enhancement in energy efficiency as 0.30, and in water efficiency as 0.01 across regions. Outstanding enhancements in the coupling are observed in Beijing (+0.006), Shanghai (+0.002), and Zhejiang (+0.0004). This study clarifies the spatiotemporal variations in the coupling between water and energy systems as represented by the efficiencies, and provides critical evidence for designing differentiated water-energy co-management policies based on the infrastructure symbiosis.