Methods Used to Purify Water

Water, that oh so essential part of life, is not always ready for human use. Water may contain minerals, chemicals, bacteria and viruses that are harmful to the human body and cause health problems. Even in ancient times, humans realized the need to purify their water. Chemical and Engineering News mentions that Hippocrates created his "sleeve" in the 5th century BC to filter water. Water purification is often mandatory after a natural disaster such as a hurricane or earthquake and is useful while camping or to ensure that your daily supply is free of contaminants.

Boiling

• Boiling is generally the most widely known way of purifying water. The boiling of water kills most of the viruses, bacteria and pathogens it contains. Boiling water does not remove lead or nitrates. The CDC advises boiling water for one minute for normal altitudes, and three minutes for "altitudes greater than 6,562 feet." Water boils at 212 degrees Fahrenheit, and at slightly lower temperatures in higher altitudes. Filter the water first if it is particularly cloudy. Boiling can be combined with other methods of water treatment.

Filtering

• Water filtration is used by individuals and water treatment plants alike. Water filters are commonly carbon or screens. All About Water notes that filtering water "is capable of removing chlorine, chlorine byproducts, and VOCs" and "the chlorine-resistant protozoa giardia and cryptosporidium." Household water filters are built in to pitchers and faucet units and can be included in the drinking water dispenser of a refrigerator. Larger filters are used by treatment plants to remove natural debris and sediment, in addition to removing chemicals and pathogens.

Chemicals

• The iodine and chlorine methods of water purification employ chemicals to destroy unwanted elements of water. Chemical water treatment methods are applied in camping and emergencies, and for treating pool, well and municipal water. Iodine tablets, crystals and liquid are available for individual use. Study the manufacturer directions on the package for correct iodine treatment of water. Iodine can cause negative health side affects. It also has an unpleasant taste, as does chlorine. Chlorine is utilized for both emergency and municipal water treatment. If needed in an emergency to treat drinking water, the laundry version of chlorine bleach (unscented) is the only safe form of this chemical to use, in two to four drops per liter or quart.

Municipal Water Treatment

• Water treatment in large quantities for municipal water supplies is typically a multi-step process handled at a water treatment plant. Charleston Water System observes that the object of municipal water treatment is "to eliminate the presence of harmful bacteria and unpleasant coloration, taste, and odor." In the industrial treatment of surface water, water is filtered for large objects, treated with chemicals including chlorine, mixed and allowed to settle to remove sediment, filtered again and finally more chemicals are added for disinfection. Groundwater treatment is more complex and characterized by the removal of bad gases and more steps of filtration.