Ancient civilizations established themselves around water sources. While the importance of

ample water quantity for drinking and other purposes was apparent to our ancestors, an understanding

of drinking water quality was not well known or documented. Although historical records have long

mentioned aesthetic problems (an unpleasant appearance, taste or smell) with regard to drinking water,

it took thousands of years for people to recognize that their senses alone were not accurate judges of

water quality.

Water treatment originally focused on improving the aesthetic qualities of drinking water. Methods to improve the taste and odor of drinking water were recorded as early as 4000 B.C. Ancient

Sanskrit and Greek writings recommended water treatment methods such

as filtering through charcoal, exposing

to sunlight, boiling, and straining.

Visible cloudiness (later termed

turbidity) was the driving force behind

the earliest water treatments, as many

source waters contained particles that

had an objectionable taste and appearance. To clarify water, the

Egyptians reportedly used the chemical alum as early as 1500 B.C. to

cause suspended particles to settle out

of water. During the 1700s, filtration

was established as an effective means

of removing particles from water, although the degree of clarity achieved was not measurable at that

time. By the early 1800s, slow sand filtration was beginning to be used regularly in Europe.

During the mid to late 1800s, scientists gained a greater understanding of the sources and effects

of drinking water contaminants, especially those that were not visible to the naked eye. In 1855,

epidemiologist Dr. John Snow proved that cholera was a waterborne disease by linking an outbreak of

illness in London to a public well that was contaminated by sewage. In the late 1880s, Louis Pasteur

demonstrated the “germ theory” of disease, which explained how microscopic organisms (microbes)

could transmit disease through media like water.

United States Office of Water EPA-816-F-00-006

Environmental Protection (4606) February 2000

Agency

The History of Drinking Water

Treatment

This fact sheet is based on information from the EPA report “25 Years of the

Safe Drinking Water Act: History and Trends.” Please refer to the full report

for details and references. You may order a copy of the report, as well as

many other EPA drinking water documents, by calling the Safe Drinking Water

Hotline at (800) 426-4791, or you may review the report online at http://

www.epa.gov/safewater/sdwa25/sdwa.html

Civilizations have always formed around water supplies.
During the late nineteenth and early twentieth centuries, concerns regarding drinking water

quality continued to focus mostly on disease-causing microbes (pathogens) in public water supplies.

Scientists discovered that turbidity was not only an aesthetic problem; particles in source water, such as

fecal matter, could harbor pathogens. As a result, the design of most drinking water treatment systems

built in the U.S. during the early 1900s was driven by the need to reduce turbidity, thereby removing

microbial contaminants that were causing typhoid, dysentery, and cholera epidemics. To reduce turbidity, some water systems in U.S. cities (such as Philadelphia) began to use slow sand filtration.

While filtration was a fairly effective treatment method for reducing turbidity, it was disinfectants

like chlorine that played the largest role in reducing the number of waterborne disease outbreaks in the

early 1900s. In 1908, chlorine was used for the first time as a primary disinfectant of drinking water in

Jersey City, New Jersey. The use of other disinfectants such as ozone also began in Europe around this

time, but were not employed in the U.S. until several decades later.

Federal regulation of drinking

water quality began in 1914, when

the U.S. Public Health Service set

standards for the bacteriological

quality of drinking water. The

standards applied only to water

systems which provided drinking

water to interstate carriers like ships

and trains, and only applied to

contaminants capable of causing

contagious disease. The Public

Health Service revised and expanded these standards in 1925,

1946, and 1962. The 1962 standards, regulating 28 substances,

were the most comprehensive

federal drinking water standards in existence before the Safe Drinking Water Act of 1974. With minor

modifications, all 50 states adopted the Public Health Service standards either as regulations or as

guidelines for all of the public water systems in their jurisdiction.

By the late 1960s it became apparent that the aesthetic problems, pathogens, and chemicals

identified by the Public Health Service were not the only drinking water quality concerns. Industrial and

agricultural advances and the creation of new man-made chemicals also had negative impacts on the

environment and public health. Many of these new chemicals were finding their way into water supplies

through factory discharges, street and farm field runoff, and leaking underground storage and disposal

tanks. Although treatment techniques such as aeration, flocculation, and granular activated carbon

adsorption (for removal of organic contaminants) existed at the time, they were either underutilized by

water systems or ineffective at removing some new contaminants.

Health concerns spurred the federal government to conduct several studies on the nation’s

drinking water supply. One of the most telling was a water system survey conducted by the Public

Health Service in 1969 which showed that only 60 percent of the systems surveyed delivered water that

met all the Public Health Service standards. Over half of the treatment facilities surveyed had major

deficiencies involving disinfection, clarification, or pressure in the distribution system (the pipes that carry

Many water treatment plants filter their water.
water from the treatment plant to buildings), or combinations of these deficiencies. Small systems,

especially those with fewer than 500 customers, had the most deficiencies. A study in 1972 found 36

chemicals in treated water taken from treatment plants that drew water from the Mississippi River in

Louisiana. As a result of these and other studies, new legislative proposals for a federal safe drinking

water law were introduced and debated in Congress in 1973.

Chemical contamination of water supplies was only one of many environmental and health issues

that gained the attention of Congress and the public in the early 1970s. This increased awareness

eventually led to the passage of several federal environmental and health laws, one of which was the

Safe Drinking Water Act of 1974. That law, with significant amendments in 1986 and 1996, is administered today by the U.S. Environmental Protection Agency’s Office of Ground Water and Drinking

Water (EPA) and its partners.

Since the passage of the

original Safe Drinking Water Act, the

number of water systems applying

some type of treatment to their water

has increased. According to several

EPA surveys, from 1976 to 1995,

the percentage of small and medium

community water systems (systems

serving people year-round) that treat

their water has steadily increased.

For example, in 1976 only 33

percent of systems serving fewer than

100 people provided treatment. By

1995, that number had risen to 69

percent.

Since their establishment in the early 1900s, most large urban systems have always provided

some treatment, as they draw their water from surface sources (rivers, lakes, and reservoirs) which are

more susceptible to pollution. Larger systems also have the customer base to provide the funds needed

to install and improve treatment equipment. Because distribution systems have extended to serve a

growing population (as people have moved from concentrated urban areas to more suburban areas),

additional disinfection has been required to keep water safe until it is delivered to all customers.

Today, filtration and chlorination remain effective treatment techniques for protecting U.S. water

supplies from harmful microbes, although additional advances in disinfection have been made over the

years. In the 1970s and 1980s, improvements were made in membrane development for reverse

osmosis filtration and other treatment techniques such as ozonation. Some treatment advancements have

been driven by the discovery of chlorine-resistant pathogens in drinking water that can cause illnesses

like hepatitis, gastroenteritis, Legionnaire’s Disease, and cryptosporidiosis. Other advancements

resulted from the need to remove more and more chemicals found in sources of drinking water.

 According to a 1995 EPA survey, approximately 64 percent of community ground water and

surface water systems disinfect their water with chlorine. Almost all of the remaining surface water

systems, and some of the remaining ground water systems, use another type of disinfectant, such as

ozone or chloramine.

Percentage of Community Water Systems Providing Treatment, by 

Population Served

0%

10%

20%

30%

40%

50%

60%

70%

80%

90%

100%

1976 1982 1986 1995

0-100 served

101-500 served

501-1000 served

1001-1000 served

3301-10000 served
A Typical Water Treatment Plant

Many of the treatment techniques used today by drinking water plants include methods that

have been used for hundreds and even thousands of years (see the diagram below). However, newer

treatment techniques (e.g., reverse osmosis and granular activated carbon) are also being employed by

some modern drinking water plants.

Recently, the Centers for Disease Control and Prevention and the National Academy of Engineering named water treatment as one of the most significant public health advancements of the 20th

Century. Moreover, the number of treatment techniques, and combinations of techniques, developed is

expected to increase with time as more complex contaminants are discovered and regulated. It is also

expected that the number of systems employing these techniques will increase due to the recent creation

of a multi-billion dollar state revolving loan fund that will help water systems, especially those serving

small and disadvantaged communities, upgrade or install new treatment facilities.