Did
you know?
Reverse osmosis is the finest water filtration method known. This process will
allow the removal of particles as small as ions from a solution. It is used
to purify water and remove salts and other impurities in order to improve the
color, taste or properties of the fluid. R.O. uses a membrane that is semi-permeable,
allowing the fluid that is being purified to pass through it, while rejecting
other ions and contaminants from passing. This technology uses a process
known as crossflow to allow the r.o. membrane to continually clean itself. This
is the reason of why an r.o. element can last many years before clogging or
need replacement. This
water purification process requires a driving force to push the fluid through
the membrane, and the most common force is household water pressure or pressure
from a booster pump. The higher the pressure, the larger the driving force and
efficiency.
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What
is the role of microbes in water quality?
Many
U.S. citizens believe that thanks to our advanced technology and enlightened
public policy we can consume without risk the food and water that are
readily available to most of us, as citizens of a rich and privileged
country. Some of those who subscribe to this buoyant and comforting attitude,
however, may have lately experienced second thoughts. Because of various
recent and widely reported incidents, many people are feeling concern
about the quality and safety of our food and water.
This
is not surprising; some of these incidents have resulted in serious, widespread
sickness, even death. For example, several incidents were reported of
people becoming sick from eating undercooked beef at fast food restaurants.
In other incidents, more than 70 people became sick and one died in late
1996 from drinking Odwalla apple juice, a brand sold at health food stores,
and last year lettuce from a small producer sickened at least 61 people
in the U.S. Northeast. The latter two incidents were related to a strain
of E. coli bacteria. Water too has raised public health concerns.
Microbial
pathogens or contaminants in drinking water are being blamed for various
gastrointestinal illnesses that have occurred in different parts of the
country. U.S. citizens, in the unlikely event they had even given much
thought to contaminated drinking water, would have considered it a condition
out of the past or one associated with developing countries. Now waterborne
sickness from microbial contaminants, some with strange and unlikely sounding
names-e.g., Cryptosporidium, Giardia, Legionella and Norwalk virus-has
become a seemingly modern concern even for people living in the United
States.
Estimates
project from seven to about 30 million Americans each year develop a gastrointestinal
illness, possibly from drinking contaminated water. EPA also provides
a wide range of figures when estimating the nation's annual medical and
lost productivity costs due to waterborne illnesses, from $3 billion to
$22 billion. Of much greater concern are the deaths related to microbial
contaminants in drinking water.
The
Centers for Disease Control and Prevention estimates 900 to 1,000 people
die each year from microbial illnesses from U.S. drinking water. Other
estimates run as high as 1,200 deaths. Although difficult to pin down,
such figures indicate the existence of a serious problem.
Microbial
Contaminants in History
Microorganisms
are present everywhere in our environment, in soil, air, food and water.
Also called microbes, microorganisms are living organisms, generally observable
only through a microscope. Our exposure to them causes harmless microbial
flora to establish in our bodies, although some microbes are pathogens
and can cause diseases. These diseases are considered waterborne if the
pathogens are transmitted by water, to infect humans or animals that ingest
the contaminated water. Diseases transmitted by water are primarily those
found in the intestinal discharges of humans or animals The presence of
microbial contaminants in drinking water has plagued humans throughout
history.
In
fact, outbreaks of cholera, typhoid fever and dysentery are recurring
themes in early U.S. history. For example, in 1850 and 1851, an especially
aggressive outbreak of cholera occurred in Sonora, an area that included
Tucson at that time. More than 1,000 people died in northwestern Sonora,
while in Tucson the 122 deaths that occurred in 1851 far exceeded the
number of recorded births that year that were 19. Due to microbial pathogens,
a harsh reality confronted those seeking gold and glory in the hills of
California. "Diarrhea," reported a doctor in Sacramento, "was so general
during the fall and winter months and degenerated so frequently into a
chronic and fatal malady that it has been popularly regarded as the disease
of California...."
Waterborne
microbial pathogens cause a whole range of diarrheal diseases. The hazards
of fecal contamination and the principles of basic sanitation were recognized
early. The occurrence of such outbreaks alerted people to the hazards
of drinking contaminated water and prompted investigations into ways to
prevent the occurrence of waterborne illnesses. Public health officials
eventually achieved success in controlling the more common forms of waterborne
diseases, at least in the United States and other developed countries.
Progress
was due to the adoption of public health measures as well as the implementation
of important water treatment techniques, such as filtration, disinfection
and sewage treatment. Some believed the battle, if not won, was at least
under control.
Emerging
Contaminants
Waterborne
microbial contaminants, however, have attracted renewed attention, both
within the scientific community and among the public. Once thought to
be under control, they are now referred to as the "emerging drinking water
contaminants." What in fact is emerging is an expanded awareness of the
presence of previously undetected microbial contaminants in drinking water
and their effects on human health.
Also
emerging is the field of environmental microbiology, as new microbial
pathogens are being discovered and research is underway to develop improved
methods for detecting and treating microbials in drinking water. Microsporidia
is an example of an emerging pathogen that is attracting attention. Potentially
waterborne, this pathogen is recognized as causing disease among AIDS
patients, although healthy persons also may be susceptible to microsporidia.
Because
of its small size, microsporidia may survive filtration, and studies thus
far indicate that the pathogen will be fairly resistant to many drinking
water disinfectants. With more research and the development of improved
detection methods, researchers will be able to better determine the occurrence
of microsporidia, both in humans and the environment.
Some
researchers believe this microorganism may eventually need to be monitored
and controlled in drinking water supplies. H. pylori is another emerging
pathogen. Common among people exposed to poor hygienic conditions from
childhood, H. pylori also has been found, although much less frequently,
among the socioeconomic advantaged. Its source is not known, but water
is thought to be a likely route of transmission. H. pylori causes inflammation
of the stomach and seems to be a factor in the development of duodenal
ulcers. It also is thought to play a causal role in the chain of events
leading to gastric cancer. The occurrence of H. pylori ranges from less
than one percent of the population of industrialized nations to three
to eight percent in developing countries. Researchers continue to study
this pathogen.
These
and other microbial contaminants are increasingly attracting the concern
of public health authorities as well as an interdisciplinary array of
experts in such fields as microbiology, engineering, epidemiology and
risk assessment.
Where
Do They Come From?
Waterborne
diseases result from drinking fecal contaminated water. To explain the
presence of microbial contaminants in drinking water is to describe a
circuitous route, from a human or animal source back to a human or animal
via drinking water. Microbial contaminants follow a fecal-oral route.
Bacteria, viruses, and protozoa are the microorganism groups containing
pathogens of primary concern in the study of waterborne disease.
Human
sources account for viruses, while both animal and human waste contribute
protozoa to water. For example, cattle are considered the source of much
Cryptosporidium, and Giardia is often traced to beavers. Both Cryptosporidium
and Giardia are protozoa. Each day the average human excretes about 38
grams of urea, mostly urine, and 20 grams of solids in feces. The excreta
contains billions of microbes. These microbes cannot only survive, but
also multiply in water and are made up of a wide range of organisms, including
pathogenic microbes, which even healthy people excrete.
Others
who have a disease or who are carriers of a disease-producing microorganism
are a more obvious source of waterborne infections. Estimates indicate
that about five percent of those who have contacted an enteric or intestinal
disease remain life-long carriers, even after having recovered from the
disease. That these intestinal microbial contaminants can infect a drinking
water source may at first seem puzzling, especially to citizens of a country
that prides itself on its public health standards.
Yet
through natural flow or accident, various types of water can interconnect
and flow together. For example, storm water runoff from residential, rural
and urban areas can carry waste material from domestic pets and wildlife,
to collect in surface waters and even enter groundwater. Through accident
or equipment failure, sewage, a rich source of microbial contamination,
might come into contact with drinking water.
Also,
defective on-site wastewater disposal or septic systems in rural and other
residential areas can contribute large numbers of coliforms and other
bacteria to both surface water and groundwater. These contaminants occur
widely and are not limited to areas inhabited by humans. A deer or other
wildlife feeding by a clear-flowing, pristine stream in an untrammeled
forested area is an appealing image. This hardy specimen of wildlife,
however, can contribute contaminants to the stream to infect a downstream
hiker enjoying a sip of spring water direct from the source. Cattle also
add contaminants to water in isolated areas. Cattle graze many backcountry
areas and drink from streams that then flow to other areas or into other
water sources. Fecal contamination can occur in indirect and seemingly
unlikely ways. Authorities suspect the contamination of Odwalla apple
juice was caused when the processing plant pressed a decayed apple that
had fallen to the ground and came into contact with feces, possibly from
a deer. This sickened 70 people and resulted in one death.
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