Desalination at Scale:Technology Choices, Energy Pathways, and Circular Brine Management for Low-Carbon Water

Abstract

Growing water stress, stricter discharge regulations, and the need to decarbonize utilities are pushing desalination from a niche option to a core component of resilient water portfolios. This review synthesizes the fundamentals and current best practice of thermal desalination (MSF, MED), membrane routes (SWRO/BWRO, electrodialysis), and emerging systems (membrane distillation and electro‑sorption) through a unified lens of thermodynamic limits, practical losses, and plant-level integration. We compare specific energy consumption (SEC), recovery ratio, and permeate quality using harmonized assumptions representative of contemporary operation, emphasizing the roles of high‑efficiency pumps, isobaric energy‑recovery devices, pretreatment robustness, and flexible dispatch under renewable-rich grids. Because concentrate handling is now a dominant sustainability constraint, we map brine pathways spanning engineered marine outfalls, inland MLD/ZLD trains, and targeted valorization (salts, magnesium products, and acid/base generation), highlighting when circular options are credible versus when they add avoidable complexity. New scenario visualizations are provided to summarize (i) sector capacity growth, (ii) technology SEC ranges, (iii) energy-supply shares, (iv) the salinity–recovery trade space, (v) permeate TDS variability, and (vi) the fleet distribution of SWRO energy use. We conclude with design guidelines that connect technology selection, controls, and brine strategy to cost, reliability, and ultra‑low‑carbon targets for site-specific constraints.