Only pure water molecules are allowed to pass through the membrane as permeate, while other impurities are retained. RO purifiers are generally very effective in removing a wide range of contaminants including bacteria, viruses, chemicals, heavy metals, salts, and microplastics. However, the process is slow and wasteful as it removes beneficial minerals along with contaminants. https://logcla.com/blogs/495357/Water-Purifiers-How-They-Work-and-Why-You-Need-One