Design Your Own Underwater ROV - International Technology and ...

With minor modifications, all 50 U.S states adopted the
Public Health Service standards either as regulations or
as guidelines for all of the public water systems in their
jurisdictions. However, the aesthetic problems, pathogens,
and chemicals identified by the Public Health Service in
the late 1960s were not the only drinking water quality
concerns, since industrial and agricultural advances and
the creation of new man-made chemicals also had negative
impacts on the environment and public health.
The main sources of drinking water are often polluted by
industrial and municipal chemicals (Gevod et al., 2003).
While filtration was a fairly effective treatment method for
reducing turbidity, disinfectants such as chlorine 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. Even though water treatment plants
reduce the concentrations of harmful chemicals in waters
to a safe level, the use of chlorine results in the formation
of disinfectant by-products, which have been proved to be
strongly carcinogenic (Gevod et al., 2003). The use of other
disinfectants such as ozone also began in Europe around
this time, but was not employed in the U.S. until several
decades later.
Even though the new chemicals were effective for water
treatment, many others 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
existed at the time, they were either underutilized by water
systems or ineffective at removing some new contaminants.
Several studies conducted by the Public Health Service
in 1969, and later in 1972, showed that only 60% of the
systems surveyed delivered water that met all the Public
Health Service standards, and 36 chemicals were found
in treated water taken from treatment plants. Over half of
the treatment facilities surveyed had major deficiencies
involving disinfection.
The combination of health issues and 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. This 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 local partners
(EPA, 1996). 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 (EPA, 1995).
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 twentieth century (NAE, 2007). 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. Filtration was recognized quite
early in recorded technological history as a unique process
for improving the clarity of water (Montgomery, 2005). As
summarized by Baker (1949), the earliest recorded reference
to the use of filters for water treatment occurred about 3000
years ago in India. The first attempt at filtering a municipal
supply in the United States occurred in Richmond, Virginia,
in 1832 under the direction of Albert Stein (Baker, 1949).
According to a 1995 EPA survey, approximately 64 percent
of community ground water and surface water systems
disinfect their water with chlorine (EPA, 1995). The
economy and effectiveness of chlorine in killing waterborne
organisms has made water chlorination a tremendous
public health success worldwide. Most studies have shown
positive associations between chlorinated drinking water
and colorectal and bladder cancer. This has been attributed
to trihalomethanes (THMs), a carcinogenic organic
halogenated byproduct of water chlorination (Reuber,
1979). Many of the treatment techniques used today by
drinking water plants include methods that have been
used for hundreds and even thousands of years; however,
newer treatment techniques (e.g., reverse osmosis and
granular activated carbon) are also being employed by
some modern drinking water plants. Military units must
have the capability to transport or produce large qualities
of water for personnel use (Photo 2). Emergency and public
disaster units must also have similar capabilities. In the
1970s and 1980s, improvements were made in membrane
development for reverse-osmosis filtration and other
treatment techniques such as ozonation. Ozone is used in
many drinking water plants for the oxidation of organic
micro pollutants and manganese as well as for disinfection
(Staehelln & Holgne, 1982).
Water Treatment Process
The process of water treatment starts from the initial point
at which water is pumped into a container from its source.
To avoid adding contaminants to the water, this physical
infrastructure must be made from appropriate materials
12 • The Technology Teacher • April 2009