Background Brine discharge from Europe’s water desalination plants represents a potential hazard for marine ecosystems. Brines are commonly disposed of using inland desalination plants, deep well injection, or by discharge into surface or ground water. However, the impact of these options can be greater than discharging the brine directly into the sea and can result in severe salinity problems in water sources, as well as in adjacent soils. The disposal of brine from desalination plants into water bodies conflicts with the objectives of the Water Framework Directive (2000/60/EC) and, therefore, it is necessary to implement brine management strategies that do not include its release into the environment. Objectives The main objective of the LIFE+ ZELDA project is to demonstrate technically feasible and economically sustainable methods for improving the environmental performance of desalination systems through brine management strategies that apply electrodialysis metathesis (EDM) and valuable compound recovery processes. The ultimate aim is to achieve zero liquid discharge (ZLD). The specific objectives of the project are, by order of importance: To design, construct and implement an EDM system for reducing the total volume of brine generated, and concentrating it in full-scale seawater and brackish water desalination plants; To integrate conventional separation processes into the EDM system in order to facilitate the recovery of valuable compounds from brines; To demonstrate the technical feasibility and sustainability of the proposed technology for achieving ZLD in existing seawater and brackish water desalination systems; To quantify and disseminate information on the environmental benefits and the economical impact of the new EDMZLD process in seawater and brackish water desalination systems; To promote the implementation of environmental policies and strategies for quantifying and minimising the environmental impact of desalination systems. Expected results: Key results from the ZELDA project are expected to provide: The characterisation of the novel membranes developed by FUJIFILM in terms of electrical resistance, permaselectivity, water permeation and ionic exchange capacity, as well as ion rejection and energy consumption and its impact on the overall EDM process; A versatile brine treatment system based on EDM that can be used in both seawater and brackish water desalination plants; A zero liquid discharge (ZLD) process based on valuable compound recovery strategies and adapted to treat the output streams of the EDM system in both seawater and brackish water desalination brine treatment; Data concerning the performance (type, quantity and purity of the compounds recovered) and operational costs of the ZLD process; 5 000 m3 of brine from seawater and brackish water desalination plants treated using the EDM-ZLD technology; 4 500 Kg of valuable compounds recovered from the brine treatment in a seawater desalination plant; 1 300 Kg of valuable compounds obtained from the brine treatment in a brackish water desalination plant; Data on the influence of the brine composition and operating conditions of the EDM-ZLD system on the overall sustainability of the desalination process; An increase in the water recovery capacity of the existing desalination plants.