Towards near-ZLD sea water brine treatment: A techno-economic study

Brine management is a growing environmental and economic challenge for desalination and allied industries. Treating brine as a resource rather than a waste aligns with circular-economy goals but requires process trains that balance efficiency, cost, and maturity. This work (i) compiles a focused literature review on MLD/ZLD pathways, (ii) applies a transparent five-criterion scoring framework to single units and hybrid trains, and (iii) based on the gathered information, proposes and simulates three brine treatment configurations in Aspen Plus to quantify energy and costs. The review/scoring identify electrodialysis (ED), brine concentrator (BC) and brine crystallizer (BCr) as the best-compromise single units; for combinations, RO–BC–BCr and RO–PRO top seawater intake, while BC–BCr (thermal baseline), and the proposed ED–BC–BCr, and a metal-recovery variant NF–ED–BC–BCr are most relevant for brine intake. Aspen simulations using Electrolyte-NRTL show high freshwater recovery (97.6–98.4%) for all three brine treatment trains. An internal heat-recovery retrofit that mildly compresses and condenses crystallizer vapour reduces thermal power an order of magnitude (e.g. ED–BC–BCr: 93.1 → 11.0 kW) with a compensating rise in compressor electricity. Economic screening based on basic engineering cost correlations finds ED–BC–BCr viable (payback ∼8 y, NPV $22.7k, IRR 11.4%), and NF–ED–BC–BCr strongly attractive when Li2CO3 is valorised (payback ∼4 y, NPV $420.7k, IRR 31.4%). The thermal baseline (BC–BCr) is not profitable under the same assumptions. While site-specific design, detailed equipment sizing, and market dynamics are required for investment-grade decisions, the results support membrane-assisted concentration plus thermal finishing as a pragmatic route to near-ZLD brine treatment with options for value-added metal recovery. For industrial decision-making, the scoring translates into a practical selection rule: when TOC/SDI and Ca2++Mg2+ are moderate and electricity is low-moderate in cost (or waste heat is available), ED–BC–BCr minimises complexity and CAPEX; where hardness/organics are high, tight ionic speciation is required, or variable feed quality is expected, NF–ED–BC–BCr better stabilises ED and extends cleaning intervals despite higher CAPEX. This guidance lets sponsors map basic feed descriptors and utility prices to a preferred train before piloting, shortening time-to-decision and reducing redesign risk.