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Water Pollution

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Water Pollution - Lesson Summary

All living organisms need water to survive; 60%-70% of the human body is made up of water. It is also vital for animals and plants.

According to the World Health Organization, every year about 3.4 million people in the world die due to diseases caused by contaminated water. The diseases are caused by parasites, bacterial infection and other microscopic pathogens that contaminate the water.

Ground water is a natural source of pure water even though pollutants reach ground water through different paths like seepage and agricultural run-off, and contaminate it.

Pollutants get added to water at two places point sources and non-point sources.

Point sources are the easily identifiable sources of pollution, such as municipal and industrial discharge pipes.

Non-point sources are not easily identifiable such as agricultural run-off from farms, acid rain and storm-water drainage from streets and parking lots, etc.

These sources add pollutants like pathogens, organic wastes and chemicals to water.

Pathogens are the most harmful water pollutants. They include disease-causing micro-organisms like bacteria and viruses.

Another major cause of water pollution is chemical pollutants like heavy metals, fertilizers, pesticides and some harmful elements.

Heavy metals such as cadmium, mercury and nickel are water soluble, and the human body cannot excrete such metals, damages the kidneys, the central nervous system and the liver.

In addition to inorganic chemicals, organic chemicals like petroleum products, pesticides and industrial chemicals also add to water pollution.

Petroleum products like oil do not dissolve in water and pollute water sources.

Pesticides get mixed in water from sprays or from soil and pollute water.

Bacteria that decompose bio-degradable detergents grow rapidly on it.

These bacteria reduce the oxygen in water and cause a threat to other aquatic life.

On the other hand, fertilizers contain phosphates that increase algae growth in water.

Algae cover the surface of water, blocking sunlight and depleting oxygen in the water.

The reduction of oxygen concentration in water causes the death of many aquatic organisms.

This process of rapid plant growth in water and the depletion of oxygen causing the death of animals results in a disfunctioning ecosystem, called eutrophication.

Drinking water usually gets contaminated by lead that comes from water pipes.

Excessive concentration of lead can cause damage to the kidney, liver and reproductive system.


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