Discovered by the ancient Greeks and Egyptians, conventional water treatment processes have been used for thousands of years. These processes involve chemical flocculation, coagulation, clarification, and media filtration. In conventional treatments, chemicals are added to cause precipitation (where chemicals bond together to become solids). This pulls out turbidity and suspended solids. Media filtration is used to clean up the remaining solids. They still work fine for clarifying turbid water and reducing hardness and metals concentration, but as we learn more about what is in our water, our standards of treatment are becoming more stringent. Conventional processes are not absolute barriers to virus and other pathogenic organisms. They do not remove dissolved salts and are not reliable for removing organic contaminants.
Advanced water treatment (AWT) refers to processes that purify water by taking advantage of water's unique properties (physical, chemical, and colligative properties). Some of these processes use membrane materials that provide an absolute barrier to very fine particles and pathogenic microorganisms. Ultra-violet light and advanced oxidative processes that people have only harnessed in the past century are used for disinfection, oxidation and precipitation of metals, and breaking down organic contaminants. Often AWT processes are used with conventional processes to form a complete, efficient and robust treatment process.