The application of chemicals in reverse osmosis water treatment plants is vital for enhancing efficiency, preventing fouling, and ensuring the production of high-quality water. Understanding the roles of various chemicals—from antiscalants and biocides to cleaning agents—can help operators optimize their processes, reduce operational costs, and provide cleaner, safer drinking water. As technology and research continue to advance, the development of more effective and environmentally friendly chemicals is likely to enhance the sustainability of RO water treatment systems.