Donetsk University of Economics and trade named
Tugan-Baranovsky
What is in our drinking
water?
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Drinking water, like every other substance, contains small amounts of
bacteria. Most of these bacteria are common ones and they are generally not
harmful. Chlorine is usually added to drinking water to prevent bacterial
growth while the water streams through pipelines. This is why drinking water
also contains minimal amounts of chlorine. |
Where does drinking water come from?
Drinking water can come from different resources. For one, it can be pumped
from the ground through wells. This groundwater is than purified, so that it
will contain no more contaminants and is suited to drink. Drinking water can
also be prepared directly from surface water resources, such as rivers, lakes
and streams. Usually surface water has to undergo many more purification steps than groundwater to become suited to drink.
Preparing drinking water out of surface water is much more expensive due to
this. Still 66% of all people are served by a water system that uses surface
water.
Part of our drinking water is pumped from the ground, usually under sand dunes.
In sand dunes water can also be infiltrated. As it sinks into the ground
through the dunes it is naturally purified. This costs much less money than the
purification of surface water. Part of our drinking water originates from dune
water.
How is drinking water purified?
Treating water to make it suitable to drink is much like wastewater
treatment. In areas that depend on surface water it is usually stored in a
reservoir for several days, in order to improve clarity and taste by allowing
more oxygen from the air to dissolve in it and allowing suspended matter to
settle out. The water is then pumped to a purification plant through pipelines,
where it is treated, so that is will meet government treatment standards.
Usually the water runs through sand filters first and sometimes through
activated charcoal, before it is disinfected. Disinfection can be done by
bacteria or by means of adding substances to remove contaminants from the
water. The number of purification steps that are taken depend on the quality of
the water that enters the purification plant. In areas with very pure sources
of groundwater little treatment is needed.
There are several problems that can endanger the quality of drinking water.
A number of these problems are summed up here.
Someone can detect coliform bacteria in drinking water. Coliform bacteria
are a group of microrganisms that are normally found in the intestinal tract of
humans and other warm-blooded animals, and in surface water. When these
organisms are detected in drinking water this suggests contamination from a
subsurface source such as barnyard run-off. The presence of these bacteria
indicates that disease-causing microrganisms, known as pathogens, may enter the
drinking water supply in the same way if one does not take preventive action.
Drinking water should be free from coliform.
Yeasts and viruses can also endanger the quality of drinking water. They
are microbial contaminants that are usually found in surface water. Examples
are Giardia and Cryptosporidium. Giardia is a single cell organism that causes
gastrointestinal symptoms. Cryptosporidium is a parasite that is considered to
be one of the most significant causes of diarrhoeal disease in humans. In
individuals with a normal immune system the disease lasts for several days
causing diarrhoea, vomiting, stomach cramps and fever. People with weakened
immune systems can suffer from far worse symptoms, caused by cryptosporidium,
such as cholera-like illnesses.
Nitrate in drinking water can cause cyanosis, a reduction of the oxygen
carrying capacity of the blood. This is particularly dangerous to infants under
six months of age.
Lead can enter the water supply as it leaches from copper pipelines. As the
water streams through the pipes, small amounts of lead will dissolve in the
water, so that it becomes contaminated. Lead is a toxic substance that can be
quickly absorbed in the human systems, particularly those of small children. It
causes lead poisoning.
Legionella is a bacterium that grows rapidly when water is maintained at a
temperature between 30 and 40 degrees for a longer period of time. This
bacterium can be inhaled when water evaporates as it enters the human body with
aerosols. The bacteria can cause a sort of flue, known as Pontiac fever, but it
can also cause the more serious deathly illness known as legionellosis.
How is drinking water quality protected?
All countries have their own legal drinking water standards. These
prescribe which substances can be in drinking water and what the maximum
amounts of these substances are. The standards are called maximum contaminant
levels. They are formulated for any contaminant that may have adverse effects
on human health and each company that prepares drinking water has to follow
them up. If water will be purified to make it suitable to drink it will be
tested for a number of dangerous pollutants, in order to establish the present
concentrations. After that, one can determine how much of the contaminants have
to be removed and if necessary purification steps can be progressed.
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Many people worry about getting sick from tap water, because of articles
on the news and in the papers, for instance about Legionella outbreaks. They
may either drink bottled water or install expensive water purification systems as a result of this. However, studies have
indicated that many of these consumers are being ripped off due to the expenses
of bottled water and in some cases they may end up drinking water that is
dirtier then they can get from their taps. To be safe, consumers that buy
bottled water should determine wheather the company that supplies them with
water belongs to the International Bottled Water Association (IBWA) and lives
up to the testing requirements of drinking water. The IBWA sends inspectors
to its companies annually, to ensure that a plant produces safe drinking
water. |