water pollution, sources of water pollution, effects of water pollution - tu

8/14/2019 Water Pollution, Sources of Water Pollution, Effects of Water Pollution - Tu

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Water pollution is a major problem associated with the developing countries. It severely affects the lives of

people. There is an entire village in Karnataka that has been affected by excess of fluoride in the ground

water. It causes deformities of the bone. In order to effectively control the pollution, the causes or the

sources must be identified and understood.

Sources

Sewage that includes organic matter, animal and human excreta-one of the major pollutants of water in

the urban and rural areas is the sewage. The sewage most often contains the organic matter that

encourages the growth of microorganisms. These organisms besides spreading diseases also consume

the oxygen present in water. This is called oxygen depletion. The aquatic organisms like the fish cannot

then survive in such waters. This creates an imbalance in the aquatic ecosystems.

Industries

The industries are mostly situated along the riverbanks for easy availability of water and also disposal of

the wastes. But these wastes include various acids, alkalis, dyes and other chemicals. They change the

pH of water. There are also detergents that create a mass of white foam in the river waters. All these

chemicals are quite harmful or even fatally toxic to fish and other aquatic populations.

The industrial wastes include toxic metals like lead, mercury, cadmium, etc, and other chemicals like the

fluorides, ammonia, etc.

Certain industries such as power plants, refineries, nuclear reactors release a lot of hot water from their

cooling plants. This hot water is let into the water bodies without the temperature being reduced. This

results in heating up of the water and thereby killing the aquatic life. The oxygen content of water also

becomes less due to increase in the temperature. This is called thermal pollution.



Agriculture

Modern methods of agriculture have resulted in use of fertilisers and pesticides to increase the yield of the

crops. Most of them are synthetic and chemicals-based. They are collectively called agro-chemicals.

These chemicals enter into the water bodies with the rain water flow and the ground water by seepage.

The chemicals remain in the environment for a long time and can enter the food chain. They cause a

number of problems in the animals.

Oil

Oil spill is a major problem in the oceans and seas. The oil tankers and offshore petroleum refineries

cause oil leakage into the waters. This pollutes the waters. Oil floats on the water surface and prevents

the atmospheric oxygen from mixing in the water. The oil enters the body of the organisms. It also coats

the body of the aquatic animals and birds which may also kill them.

Pollutant Source/Cause Effect

Sewage that includes domestic

wastes, hospital wastes, excreta, etc.

Sewarage of rural and

urban areas.

Oxygen depletion Spread of

diseases/ epidemics

Metals-Mercury Industnal wastes

Minamata disease (resulted from

the contaminated waters of the

Minamata bay in Japan in 1953) -

causes numbness of limbs, lips

and tongue, blurred vision,

deafness and mental

derangement.



Lead Industrial wastes

Absorbed into blood and affects

PBCs, liver, kidney, bone, brain

and the penpheral nervous

system. Lead poisoning can even

lead to coma.

CadmiumCadmium industnes,

fertilisers

Deposited in organs like the

kidney, pancreas, liver, intestinal

mucosa, etc. Cadmium poisoning

causes headache, vomiting,

bronchial pneumonia, kidney

necrosis, etc.

Arsenic Fertilisers

Arsenic poisoning causes renal

failure and death, It can cause

nerve disorder, kidney and liver

disorders, muscular atrophy, etc.

Agrochemicals like DDT Pesticides

Accumulates in the bodies of

fishes, birds, mammals including

man. Adversely affects the

nervous system, fertility. Causes

thinning of egg shells in birds.

Effects of Water Pollution

Eutro hication



Water bodies are being constantly polluted by dumping of sewage which includes organic matter and by

the runoff from the agricultural fields that contains fertilisers. Pollutants like sewage, organic wastes and

fertilisers contain good amount of inorganic nutrients like nitrates and phosphates.

These nutrients enrich the water promoting the growth of algae. The water turns green. This is called

algal bloom. Rich algal growth leads to great increase in the number of the decomposers. All these life

forms-decomposers, algae, other plants, fishes and other aquatic animals, use the oxygen in the water for

respiration. This causes great demand for oxygen and results in depletion of oxygen.

Pollution is measured by knowing the biological oxygen demand (BOD). Low BOD means little pollution

and high BOD means higher pollution.

Eutrophication also results in overgrowth of plants like Eicchornia that covers the entire surface of water.

This reduces the light reaching the lower layers in water.

Thus, enrichment of water with inorganic nutrients like nitrates and phosphates is called eutrophication.

BiomagnificationThere are many pollutants like the DDT that are not bio-degradable. These accumulate in the organisms

and cause serious health problems. The contamination of water with these pollutants results in their entry

into the microscopic plants and animals. These organisms are fed upon by higher aquatic life like the fish.

The fish in turn are fed upon by the land animals including man.

Thus, the pollutant reaches the body of man. At each step in the food chain, the contaminant increases in

quantity. This is because a fish feeds on large quantity of smaller plants and man eats fish. These

contaminants like DDT remain in the fats and are not degraded in the body. Over the years the amount of

DDT increases in the body. This is called biomagnification.



Bio-magnification

Pollutants like DDT also reach the human body through milk if the cattle are exposed to DDT sprayed

grass or contaminated water. This causes serious blood and nervous disorders in man and other animals.

Epidemics

Pollution of water by organic wastes is a major cause for occurrence of epidemics like cholera,

gastroenteritis in India. The microorganisms causing these diseases enter the water bodies through the

organic wastes and then into the bodies of healthy persons causing diseases. In fact, a good indication of

pollution of water is the presence of bacteria E. coli that lives in the human intestines.

Acid Rain

As discussed under air pollution, acid rain occurs due to the pollution of atmosphere and the pollutants

coming down get mixed with water during rain. These waters also run into the water bodies where they

cause a lot of damage due to the presence of acids. They cause change in pH of water and damage the

aquatic life.

water pollution, sources of water pollution, effects of water pollution - tu

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