Chemistry Reference
In-Depth Information
What's Going On?
The effectiveness of different forms of water purification largely
depends on the type of contaminants found in the water. Boiling kills
microorganisms and may help to precipitate some solid contaminants.
Distillation, or boiling and condensing the water vapor, is more effective
at purifying water, but it is not very convenient because it takes more
time and requires specialized equipment. Filtration can remove sediment
and make water more clear. If the filter contains activated carbon, it can
help to remove ions and metal contaminants as well. Chlorine bleach and
iodine can be used to kill microorganisms in water and help to neutralize
and precipitate chemicals, but the treated water must sit for a period
of time before it can be consumed. Techniques such as adding bleach
and iodine are more effective when combined with filtration to remove
any particles that settle out. Additionally, some people find the taste of
treated water undesirable.
Connections
Some of the most dangerous contaminants of water are parasitic
protozoans, one-celled organisms that are capable of movement during
some stage of their life cycle. Because these organisms are unicellular,
they cannot be seen with the naked eye, so it is impossible to tell if a
sample of water is contaminated simply by looking at it. In fact, many
protozoans exist in clear streams and fast-moving water that some
individuals might assume to be safe. Most protozoans are so small that
they cannot be removed by simple filtration, but they can be removed by
chemical treatment or boiling.
Some parasitic protozoa found in water are
Giardia
,
Entamoeba,
and
Cryptosporidium
.
Giardia
(see Figure 3) is the most common cause
of extreme vomiting and diarrhea among hikers and campers in the
wilderness.
Entamoeba
can cause amoebic dysentery, also known as
“Montezuma's revenge” or “travelers diarrhea.” This organism is more
common in nonindustrialized countries and most often affects tourists
and travelers to those areas who consume the water.
Cryptosporidium
is not as well-known as the other protozoans, but has been known to
contaminate municipal water sources in industrialized areas, causing
diarrhea and intestinal problems for consumers.
