Purification of water may refer to any of the following.
Water purification, the large scale production of clean water for supply to consumer taps and industry.
Distilled water, the use of distillation to remove contaminants from water.
Portable water purification, techniques for use in emergencies or away from conventional sources of clean water.
Water filter, devices used for small scale quality improvement, often in domestic situations.
Deionized water, industrial production of ultra pure water.
Reverse osmosis, a technique for producing potable water from highly contaminated sources.
Sewage treatment, treatment of sewage to remove contaminants.