Water Purification

**Definition:** 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 WASTEWATER to provide potable and hygienic water in a controlled or closed environment as well as provision of public drinking water supplies.

**Tree numbers:** - N06.850.780.200.800.800.900.900 - N06.850.860.510.900.900