U.S. National Library of Medicine

1. Water Purification

   Any of several processes in which undesirable impurities in water are removed or neutralized; for example, chlorination, filtration, primary treatment, ion exchange, and distillation. It includes treatment of waste water to provide potable and hygiene water in a controlled or closed environment as well as provision of public drinking water supplies. (From McGraw-Hill Dictionary of Scientific and Technical Terms, 4th ed)