United States
Environmental Protection
Agency
Office of Water
(4606)
EPA-816-F-00-006
February 2000
SEPA 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
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. Meth-
ods to improve the taste and odor of drinking water were recorded as early as 4000 B.C. Ancient
Sanskrit and Greek writings recom-
mended 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 obj ectienable taste and ap-
pearance. To clarify water, the
Egyptians reportedly used the chemi-
cal 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.
Civilizations have always formed around water supplies.
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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 causingtyphoid, dysentery, and cholera epidemics. To reduce turbid-
ity, 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. PublicHealth 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 ex-
panded these standards in 1925,
1946, and 1962. The 1962 stan-
dards, regulating 28 substances,
were the most comprehensive
federal drinking water standards in existence before the SafeDrinking Water Act of 1974. Withminor
modifications, all 50 states adopted the Public Health Service standards either as regulations or as
guidelines for all of the public water systems in theirjurisdiction.
By thelate 1960s itbecame apparent thatthe aesthetic problems, pathogens, andchemicals
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 maj or
deficiencies involving disinfection, clarification, or pressure in the distributi on sy stem (thepipes that carry
Many water treatment plants filter their water.
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water from the treatment plantto buildings), or combinations ofthese deficiencies. Small systems,
especially those with fewer than 500 customers, had the most deficiencies. A study in 1972 found 3 6
chemicals in treated water taken from treatment plants that drew water from the Missi ssippi River in
Louisiana. As a result ofthese 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 adminis-
tered 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 peopl e 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 treatmenttechniques for protecting U. S. water
supplies from harmful microbes, although additional advances in disinfection havebeen made over the
years. In the 1970s and 1980s, improvements were made in membrane development for reverse
osmosis filtration and other treatmenttechniques such as ozonation. Some treatment advancements have
been driven by the discovery of chlorine-resi stant pathogens in drinking water that can cause illnesses
like hepatitis, gastroenteritis, Legionnaire'sDisease, andcryptosporidiosis. 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 V\Mer Systems Providing Treatment, by
Population Served
inn%
90%
80%
70%
60%
50%
40%
30%
20%
10%
^
ir^^ -"•
% /
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• — "™ — "
• — ^~^__
^^^
1976 1982 1986 1995
-»- 0-1 00 served
-•-101 -500 served
501 -1000 served
1001 -1000 served
-*- 3301 -10000 served
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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 alsobeing employed by
some modern drinking water plants.
Recently, the Centers for Disease Control and Prevent on and the National Academy of Engi-
neering named water treatment as one of the most significant public health advancements of the 20th
Century. Moreover, the number of treatmenttechniques, 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 newtreatment facilities.
Follow a drop of water from the source through the
treatment process. Water may be treated differently
in different communities
depending on the quality
of the water which enters
the plant. Ground water is
located underground and
typically requires
less treatment than
water from lakes,
rivers, and streams.
Coagulation removes dirt and other particles in water. Alum and other chemicals
are added to water to form tiny sticky particles called "floe" that attract dirt
particles. The combined weight of the dirt and floe cause it to sink.
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Disinfection: A small amount of chlorine is
added or some other disinfection method
is used to kill any bacteria or microorganism |
that may be in the water.
Filtration:
The water passes
through filters,
some made of Layers
of sand, gravel, and
charcoal that help
remove even
smaller particles.
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