At one time, wilderness streams were so clean that thirsty hikers didn’t hesitate to take a drink. Today, the U.S. Environmental Protection Agency reports that 90 percent of the global water supply is contaminated. In wilderness areas, an increase in human visitors has contaminated water with microscopic organisms that can cause serious illness or death.
Industrial waste also makes a significant portion of the world’s water supply unfit for consumption or even for use in agriculture, the Global Education Project notes. Industries using significant amounts of water — and often discharging contaminated wastewater back into deep aquifers — include petroleum refining, pulp and paper, chemical processing and others. The quick expansion of industry to developing nations is increasing the challenge of maintaining drinkable water.
But water quality isn’t just a modern issue. Throughout history, humans have found it necessary to take steps to purify the water they used for drinking, cooking, bathing and growing food. The history of water purification runs very deep.
Water purification in the ancient world
In ancient times, people tasted water to determine its suitability for drinking. Later, this method was found to be unreliable. Still, the efforts of ancient people to purify their drinking water led to a number of innovations that contributed to today’s purification systems, notes the American Water Works Association.
Researchers believe the quest for pure water started in prehistoric times, although Sanskrit writings and inscriptions left in tombs in ancient Egypt stand as the first solid documentation of the process. Sanskrit medical writings dating to around 2,000 B.C. mention several different processes for purifying water, including heating in the sun, filtering through gravel or sand, and boiling over fire.
The Victorian Era: Water purification and health
During the 1800s, scientists began to understand the clear and direct relationship between health and water quality. Around 1850, London officials noted a drop in deaths from cholera after installation of water treatment systems. With city officials’ new knowledge of the importance of clean drinking water, the city passed the Metropolitan Water Act in 1852 to ensure filtration of any water supplying the city.
The Industrial Revolution of the 19th century kicked off an unprecedented era in pollution of the world’s water supply, sparking the development of increasingly sophisticated purification systems.
Historical methods of purifying water
Water purification refers to the removal of unwanted or dangerous chemicals, solids, gases and biological organisms with a goal of making water suitable for a certain use. For example, water typically is purified for use as human drinking water. However, purification also can be used to produce water for chemical and industrial use, pharmacology, medicine and other areas.
A variety of methods has been used for decades to purify water to varying degrees and for different purposes. Princeton University’s Outdoor Action Program notes that heating water to higher than 160 degrees Fahrenheit kills any pathogens within 30 minutes. At 185 degrees or above, it only takes a few minutes. At water’s boiling point of 212 degrees Fahrenheit, pathogens are destroyed in less than a minute.
Chemical treatment, including the use of either iodine or chlorine tablets, also has been in use for a number of years. The Outdoor Action Program warns that chemical treatment may not be fully effective, depending on the temperature of the water to be purified.
Modern water purification
Today, several sophisticated methods exist for purifying water, including:
- Sediment filtration, which uses filters to remove large particles of dirt, sand and other materials
- Ion exchange, in which metallic elements are removed using a large tank filled with negatively charged resin beads. The process uses electromagnetic attraction to trap the metallic ions with the resin particles
- Carbon filtration, which passes water through activated carbon to remove chlorine, herbicides, pesticides and other contaminants
- Reverse osmosis, which uses differing pressure to force water through a membrane, trapping dissolved materials
- Ultraviolet light, which sterilizes water, killing any bacteria, viruses or other biological organisms
Water quality today
The United States boasts one of the world’s safest water supplies, but dangerous contamination can happen in an instant, notes National Geographic. Backed by thousands of years of history, today’s sophisticated water purification methods allow most Americans to feel confident that their water is safe to drink.