Magnesium enrichment of desalinated water: Technologies, mechanisms, and practical considerations - a critical review

Desalinated water, while increasingly relied upon as a sustainable source of drinking water, is deficient in essential minerals, out of which the most important macronutrient is magnesium. Magnesium deficiency has been linked to cardiovascular diseases and other health risks in humans, as well as negative effects on agricultural productivity when desalinated water is used for irrigation. This review covers current technological approaches for enriching desalinated water with Mg²⁺, ranging from simple techniques such as dilution with seawater or other brines, direct chemical supplementation and dissolution of quarry dolomite, to advanced seawater-separation-based methods including ion-exchange, nanofiltration followed by diananofiltration and ultrafiltration, hybrid electrodialysis/nanofiltration, and flow-electrode capacitive deionization. Case studies from Israel and Saudi Arabia highlight practical challenges, normalized costs, and policy drivers. While no single method is universally applicable, separation-based technologies offer promising scalability and cost-effectiveness for achieving regulatory targets between 5 and 20 mg/L as Mg in the product water. A comparative analysis of operational, economic, and water quality implications is presented, together with answers to common questions and perspectives for future research and implementation.