EFFECTS OF WATER POLLUTION..

Water pollution has number of effects. The effects could be classified as

• effects on ecosystem

• effects on animal health

• effects on human health

Effects on Ecosystem

1) Besides inorganic nutrient input, with the inflow of waste water, decomposition of organic wastes, plant nutrients such as nitrates and phosphates takes place. This promotes the growth of oxygen consuming algae (algal bloom), especially the blue-green algae. The growth of oxygen consuming algae, which deoxygenates water killing fish and other animals is referred to as eutrophication.

2) Addition of oxygen not sufficient to support life.

3) Addition of non-degradable broad-spectrum pesticides, which cause mass destruction of agnatic life.

4) Addition of oil destroys life by reducing oxygen and catching fine, destroying ecosystem.

Biological oxygen demand or BOD stands for the amount of oxygen regained by the microorganism of polluted water to complete the decomposition of organic matter present in the water. The term is usually used to know the amount of oxygen consumed. Higher in the amount of oxygen consumed, higher is the degree of organic pollutants. BOD is expressed in milligrams of O₂ per litre of water. A weak organic waste has a BOD less then 1500 mg/ litre, a strong one has higher than this. A survey of the river Yamuna recorded BOD of 2000 at Delhi, 9000 at Mathura and 12,000 at Agra.

• Shifts in biodiversity of animals and plants in polluted ecosystem.

• Imbalance in host - parasite relations in the ecosystem and changes in food - webs and food chains.

• Imbalances in microbial population and effects due to such imbalances.

• Depositions of deleterious chemicals in soil leading to loss of soil fertility.
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Effects on Animal Health

• Large scale death of aquatic and terrestrial animals

• Reduced reproduction rate

• Increased incidence of diseases

• Imbalances created in secondary food chains

• Accumulation of bioaccumulative and non-biodegradable pollutants in animal bodies.

• Some organochlorine pesticides (like DDT, BHC, Endrin) are known for bioaccumulative and biomagnifiable characters.

Bioaccumulation

It is a concept wherein pesticides are not subjected to disintegration and excretion from animal/human body.

Bio magnification

Due to bioaccumulative characters, these pollutants pass through the food chain and food web. While passing through the organisms, the concentration of pollutants gets increased. This is called bio magnifications. For e.g., 0.5 ppm DDT in grasses gets magnified to 2ppm in sheep. It may be magnified to 10 ppm in human beings who eat such polluted mutton.

Some organochlorine pesticides cause health hazards like impotence, cancerous tumors beyond a threshold limit of accumulation.

Effects on Human Health

• Increased incidence of tumours, ulcers due to nitrate pollution.

• Increased incidence of skin disorders due to contact with pollutants.

• Increased incidence of constipation, diarrhea and infections to intestine.

• Dangerous effects on growing foetus in pregnant women.

• Concentration of pollutants due to bioaccumulative pesticides. through secondary and tertiary food chain in case of non - vegetarians.

• Still births, abortions and birth of deformed children.

• 'Blue baby' disease caused by methane globinemia - which results in asphyxia (reduced O₂ supply).

• Reduced activity of immune system.

• Loss of memory power and reduced mental sharpness.

• Water borne diseases like jaundice, hepatitis, gasteroenteritis will be more prevalent due to water pollution.

• Reduced bone development and muscular development.

• Reduced male fertility.

• Shifts in physiological cycles of human body.

Improvement of Water Quality

Water pollution cannot be altogether checked, but measures can be taken to reduce it.

These one as follows: 

a) Primary treatment

In this method mechanical screening and sedimentation of un-dissolved solids in raw sewage is done. But it fails to remove any dissolved substance from water.

b) Secondary treatment

Sewage treated in primary treatment is brought in contact with oxygen and aerobic micro-organisms. They break down the organic matter into harmless materials as CO₂ and H₂O. Further, chlorination is done to reduce the bacteria. It may be further treated to tertiary level zero measures are adopted for secondary treatment. They are (i) Trickling filter method (ii) Activated sludge process.

i) Trickling filter method

In this case sewage water passes through a thick bed of gravel stones so that bacteria consume most of the organic matter.

ii) Activated sludge process

Here the sewage water is pumped into an aeration tank. The tank contains sludge consisting of bacteria and algae. The bacteria is able to decompose most of the organic matter and algae produces oxygen to promote the growth of these decomposers.

c) Advanced water treatment or temporary treatment

Finally in the third step, salts like nitrates and phosphates are removed by precipitation technique.

Reverse osmosis

By this technique sewage water can he converted into fairly clean drinking water.