Water Purification
Water purification involves the processes used to remove undesirable contaminants, biological pollutants, and gases from water. The goal is to produce water quality suitable for specific end-uses, typically for human consumption or for industrial processes.
History
Water purification has a long history, with evidence of early attempts dating back to ancient civilizations:
- Ancient Sanskrit writings mention the use of heat and filtration to purify water.
- Hippocrates, known as the "Father of Medicine," invented the first water filter in the 5th century BC, known as the "Hippocratic sleeve," made of cloth to trap impurities.
- In the 17th century, Sir Francis Bacon observed that sea water could be desalinated by passing it through a cloth, and in 1627, he suggested that sand filtration could be used to purify water.
- The industrial revolution brought about more systematic approaches to water purification, with the first documented water treatment plant opened in Scotland in 1804 using slow sand filtration.
- By the late 19th and early 20th centuries, chlorine was introduced as a disinfectant in water treatment, significantly reducing waterborne diseases.
Methods of Water Purification
1. Physical Methods
- Filtration: This includes various filters like sand filters, activated carbon filters, and membrane filters (e.g., reverse osmosis). Filters can remove particles, bacteria, and some chemicals.
- Boiling: One of the oldest methods, boiling kills pathogens but does not remove chemical contaminants or improve the taste of water.
- Sedimentation: Allowing particles to settle out of water over time or with the addition of coagulants to help flocculation.
2. Chemical Methods
- Chlorination: Adding chlorine or chlorine compounds to water to kill bacteria and other pathogens.
- Coagulation and Flocculation: Chemicals like alum are used to clump together fine particles to facilitate sedimentation.
- Ozonation: Ozone gas is used to disinfect and oxidize contaminants, particularly effective against viruses and bacteria resistant to chlorine.
3. Biological Methods
- Slow Sand Filtration: Utilizes biological processes in the sand bed to purify water through filtration and biological degradation.
4. Advanced Techniques
- Ultraviolet (UV) Light: UV radiation can inactivate microorganisms by destroying nucleic acids and disrupting their DNA, making them incapable of reproduction.
- Distillation: Involves boiling water to produce steam, which is then condensed back into liquid form, leaving contaminants behind.
- Reverse Osmosis (RO): Uses a semi-permeable membrane to remove ions, molecules, and larger particles from drinking water.
- Electrodialysis: Uses an electric field to move ions through a membrane, typically used for desalination.
Regulations and Standards
Water purification is governed by various standards and regulations worldwide:
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