Sample Passage with questions and answers

Read the passage below and answer the questions that follow based on your understanding of the passage:

Water pollution refers to any change in natural waters that may impair further use of water, caused by the introduction of organic or inorganic substances or by a change in the temperature of water. Waste water emanate from the following sources: Municipal waste water, Industrial waste water, Agricultural runoff, Storm water and urban runoff.

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During recent years such chemical pollution of water bodies has increased many fold and people, who are responsible for human health have become increasingly concerned about water pollution. Eutrophication is the enrichment of water by nutrients from natural or man-made sources. Of all the nutrients, nitrogen I and phosphorus are most often considered as key nutrients responsible for promotion of growth of algae land other plants resulting in anoxic condition.


Pesticides used in agriculture reach natural or man-made water bodies and cause disruption to one or more physiological functions of aquatic organisms by interfering with the production of necessary biochemical e.g., D.D.T. which consists of aromatic ring, mimic the effects of estrogen in aquatic animals such as fish, where the reproduction is disturbed. As such non biodegradable pesticides accumulate in the body of aquatic organisms through the process of biomagnification. Along with agricultural runoff many toxic chemicals reach water bodies through industrial effluents.

The structure of a molecule is the key to its biodegradability. In general polymers with mixed I backbone linkage (carbon-oxygen or carbon-nitrogen) show greater susceptibility to hydrolysis, than I carbon-carbon backbone polymers. Polymers with aromatic components or branched region tend to be more resistant to attack by microorganisms than straight chain aliphatic compounds.

Most common system practised for control of water pollution is the use of waste water treatment I plants, based on the physical, chemical and biological treatment steps generally known as preliminary, primary, secondary and tertiary treatments. It must be remembered that the steps of treatment and type of treatment will depend upon the constituents and their concentrations in the effluent and final usage of water.

1. Why did the quality of water deteriorated due to human activities


Ans. Detergents are of recent origin, used as cleansing agents and derived from surfactants (10-30%), builder (15%) and other ingredients. Household detergents contain several pollutants which severely affect the water bodies. They contain surface active agents and contribute to phosphates of Sodium (Na), sodium silicates, sodium sulphates etc. the most important disadvantage of detergents is the environmental pollution caused by the factory refuse discharged of nearby water sources.

2. Why the protection of human health has become a problem?

Ans. Environmental pollution likes global warming – temperature changes may have an impact on several categories of diseases including cardiovascular, cardiovascular and respiratory diseases. High temperature overloads the thermo regulating system of the body.

The UV radiation affects the immune system of the skin and hence these might be an increased number of cases of skin cancer Due to severe environmental pollution has become a problem for the protection of human health.


3. Justify the statement “Pesticides are useful and at the same time harmful to the ecosystem.”

Ans. India is predominantly an agricultural country. In India almost 50% of the potential of food grains production is lost annually due to insect/pests, pathogen etc. Pesticide plays an important role for control of pests in agriculture and public health programmes. India at present is the largest manufacturer as well as consumer of pesticide chemical in Southern Asia.

Pesticide possesses potential health hazard not only to livestock and human beings but also to aquatic flora and fauna. The biomagnification and bioaccumulation of the pesticide in food chain of fishes of serious concern

The pesticides are most widely used to protect the standing crops from pest and to increase the yields of crops. However, they cause major harm to aquatic fauna via agricultural run-off and this has resulted in major ecological problems.

4. What determines biodegradability of a chemical?

Ans. Decomposition of chemical and organic material by micro-organisms is known as biodegradation. Biodegradation term is applied especially to detergents and insecticides, which vary widely in this respect. For ecological reasons, a high degree of Biodegradation is desirable to minimize adverse environmental effect of such material, phosphate compounds a chlorinated hydrocarbons, such as DDT are not biodegradable and so their use is restricted. Biodegradable plastic containers have been developed to get rid of solid waste problem.

5. How polluted water is treated for safe disposal?

Ans. Public water supply, especially from surface water, often involves the chemical treatment methods surface raw water is generally purified by slow sand or rapid sand filters. Brief description about the application of coagulation, sedimentation and filtration is dealt in primary and secondary treatment process.

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