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Freshwater Pollution
Objectives- identify sources of freshwater pollution, describe effects of freshwater pollution and explain
ways of cleaning pollution in freshwater up
Anything that can change the color, taste and smell or that has a negative effect on water or the
living things that depend on it is called water pollution. As you can tell by the definition, many things
can cause freshwater pollution. Pollution can come from human activities and natural sources and
affect surface water, ground water as well as precipitation.
In the past, human waste was a major source of water pollution. Before sewage treatment,
human waste would end up in water that could eventually be used as drinking water by people farther
downstream. The disease Cholera was caused by human waste and killed thousands. Parts of the
world such as areas in China still have open trench sewers. The sewage flows through… well open
trenches along streets. If you watch TV shows such as Survivorman, you notice that they will rarely drink
from natural sources of water, except where it comes directly from the ground. This is due to animal
waste in water. Animal waste has bacteria that can pollute water.
Factories and mines can cause water pollution also. The chemicals used in the manufacturing of
the goods produced or by products of the manufacturing can pollute water. Though not much of a
problem anymore, many factories would dump water from the plant directly in to lakes or rivers. This
was the case for factories along the Wabash River. Factories can also release sulfur dioxide and nitrogen
oxide when coal or oil is burned. These two molecules combine with water in the water in the
atmosphere forming acid rain. Acid rain can turn lakes acidic killing fish. It can also harm land plants,
and eat away stone of buildings and statues. The exhaust from vehicles can also form acid rain. Believe
it or not, hot water can be a pollutant. Industries that use water to cool off the plant return warm water
to the lake they get the water from. Two problems can happen. One is that some fish cannot survive in
warm water. Second, warm water can cause an increase in the growth of algae. This is not a major
problem until the algae die. Then the decomposers that break down the algae use oxygen that fish
need. Also warm water holds less oxygen than cold water, making it difficult for fish to survive.
Agriculture activities can pollute water. The fertilizers which help plants grow also help aquatic
plants grow (remember the algae problem in the previous paragraph). Pesticides that may be used can
also get into water harming small aquatic organisms that form the base of the food chain. Farm
chemicals can enter water in runoff after heavy rains. One chemical commonly used on fields is
nitrogen which is found in many fertilizers. Rural communities that obtain water from streams may
have high nitrogen levels in the water. High nitrogen levels in drinking water can affect infants causing
blue baby syndrome. Nitrates (a form of nitrogen) reduce the ability of blood to carry oxygen. Minor
symptoms are diarrhea, vomiting and a lack of energy. In more severe cases, the child’s skin may begin
to take on a bluish tint and they may have trouble breathing.
Runoff can also carry various chemicals from roads and cause water pollution. Oil, gasoline and
road salt can carried off by water and become part of the surface water or ground water. Boats can
obviously leave oil on the surface of lakes.
Water pollution can be placed in two categories, point source and nonpoint source. When a
specific source of pollution can be identified, the location is called a point source. When the pollution
comes from a large area, it is considered to come from a nonpoint source.
Freshwater pollution can be cleaned up by both natural and artificial means. The roots of some
water plants are capable of filtering water particles from water. Other aquatic plants such as duck weed
and hyacinths can absorb some chemicals. Bacteria in the water can help to break down waste.
Wetlands can help to clean up water pollution. They contain the plants and bacteria necessary to do
this. As water flows into an aquifer through sand and rock, much of the pollution from natural sources
can be removed.
One of the best ways to reduce freshwater pollution is to keep from polluting water in the first
place. Disposing of household chemicals in the correct manner and avoiding overuse of lawn chemicals
will help. Farmers often leave strips of grass along field edges which can serve several functions
including helping to filter pollutants before the water reaches a lake or stream.
A method of determining the cleanliness of lakes and streams is by studying the number and
variety of fish and macroinvertabrates. The cleaner the water, the greater the number and diversity of
the macroinvertabrates. What everybody calls a “buffalo gnat” is actually a black fly. These are
extremely common in northern climates where clean, clear water is common. They have become
increasingly common around here in the last couple of years. What this means is that these nasty bugs
are due to our unpolluted freshwater!
Questions:
1. What is some nonpoint sources of pollution listed in the reading?
2. What are some point sources of pollution listed in the reading?
3. What are some reasons water in the northern United States and Canada may be cleaner than the
water in our area?
Go to the website below and answer the questions.
http://www.terrehautecleanwater.com/CSO/home2.html
1. What type of sewer system does Terre Haute have?
2. What problem exists with Terre Haute’s sewer system?
3. How does Terre Haute plan to deal with storm runoff?
Research questionsWhat is an allowable amount of nitrogen in drinking water?
http://www2.epa.gov/uswaters