The human quest for clean, drinkable water has been going on for thousands of years, and methods of purifying water have undergone countless incarnations over this time. According to the evidence of Sanskrit writings dating to approximately 2000 B.C.E., water filtration appears to have been developed in the-Indus Valley, located in current day Pakistan and western India. The Susruta Samhita, ancient Sanskrit medical writings, include instructions on purifying water: "Impure water should be purified by being boiled over a fire, or being heated in the sun, or by dipping a heated iron into it, or it may be purified by filtration through sand and coarse gravel and then allowed to cool." Early purification methods were focused on the aesthetic qualities of water,'..such as taste and appearance, rather than hygiene.
The ancient Egyptians were also concerned with the appearance of their drinking water. As early as 1500 B.C.E. they were using alum to settle out particles clouding their drinking water. Hundreds of years later, Hippocrates invented what is known as the "Hippocrates sleeve," a cloth sack for filtering water after it had been boiled.
In the eighteenth century modern sand filtration methods were introduced, which led to water filtration in large cities. But it was not until the nineteenth century that the link between health and water quality was established. Until this point all purifying methods were still based on the notion that pure water was simply water that looked clear and tasted good. When a cholera outbreak in London in 1855 was traced to a contaminated water source, the public finally came to realize that invisible contaminants in water could cause major health problems.
