Desalination in the Anthropocene: Technologies, Energy, Brine Management, and Pathways to Ultra-Low-Carbon Water

Abstract

Escalating water stress and coastal urbanization are accelerating the deployment of desalination, with global installed capacity exceeding tens of millions of cubic meters per day and growing rapidly in arid and semi-arid regions. This review consolidates technological fundamentals and state-of-practice across thermal processes—multistage flash and multiple-effect distillation—membrane technologies such as reverse osmosis, electrodialysis, and emerging approaches including membrane distillation and capacitive deionization. We critically examine specific energy consumption, thermodynamic limits, and practical strategies that have driven step-changes in energy efficiency, including high-pressure pump advances, energy recovery devices, staging, hybridization, and flexible operation with renewables. Brine management emerges as a central multi-objective challenge linking environment, regulation, and circular-economy opportunities; we survey dilution outfalls, crystallization, mineral recovery, and zero-liquid-discharge architectures. Using harmonized assumptions, we develop comparative performance maps and scenario figures (supplied) to visualize capacity growth, energy mix, recovery vs. feed salinity, permeate quality distributions, and technology-specific energy ranges. We conclude with design guidelines that align plant-level choices with decarbonization targets and resource constraints, highlighting research avenues in low-defect membranes, fouling-resilient pretreatment, high-salinity RO, brine valorization, and system-level controls. The review provides a transparent basis for techno-economic and environmental decision-making in the transition toward ultra-low-carbon desalination