In 1804, the first water treatment facility was built in Scotland then in Paris in 1806, using a settling process to remove large residues then letting water pass through sand and charcoal filters. For a while people thought it was enough to clean their water until 1854 when a major cholera outbreak hit across London prompting the health authorities to take things more seriously; and resorted to using chlorine and ozone to treat water.
Through the years, water treatment technology continues to improve; and more and more cities were building water treatment facilities, resulting to decreased cholera and typhoid outbreaks.
In the 1940s, the desalination equipment was invented. During this time also, the U.S. Public Health Service created the first standards for drinking water which led to the approval of membrane filtration process in 1957; and in 1974 the Safe Drinking Water Act paved the way for continued improvements in water filtration and treatment.
Water testing and treatment is considered as one of the greatest public health achievements of the 20th century. In the U.S., where tap water is considered safe for drinking, its disinfection has played a critical role in improving the quality of water to make it safe for drinking.