Ferric chloride (FeCl₃) is widely used in water desalination as an effective coagulant during pre-treatment. It helps remove suspended solids, colloids, algae, and natural organic matter that can cause fouling and shorten the life of reverse osmosis (RO) membranes. By promoting the formation of larger, faster-settling flocs, ferric chloride improves water clarity, lowers the silt density index (SDI), and protects membrane performance. It also reduces color and organic content in seawater, making it an essential step in producing high-quality desalinated water. When applied at the right dose, ferric chloride enhances operational efficiency, reduces cleaning frequency, and ensures more reliable, cost-effective desalination processes.