Tag: effects of water pollution

Questions Related to effects of water pollution

A water body has high BOD indicating that water is

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Being contaminated with sewage

  2. Being aerated

  3. Receiving minerals

  4. Atrophic

Show answer
Correct Option: A
Explanation:

Biological Oxygen Demand indicates the increase in presence of organic matter in the water body. High BOD indicates the great amount of organic matter. The dissolved oxygen in water is consumed by bacteria to decompose the organic matter of sewage or other discharges thereby depleting the oxygen of the water body. The decrease in oxygen can kill the aquatic life in water body.

Hence, the correct answer is 'Being contaminated with sewage'.

BOD is measure of.

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Industrial waste being poured in water body

  2. Extent of pollution with organic compounds

  3. CO combined with haemoglobin

  4. $O _2$ required by green plants during night

Show answer
Correct Option: B
Explanation:

The microorganisms in polluted bodies use dissolved oxygen to metabolise organic matter in polluted waters. This is called biochemicalical oxygen demand. The more organic matter in sewage and polluted bodies, greater the BOD and hence less oxygen is left availble tor higher animals like fishes.

Which is the correct ascending arrangement of BOD of sewage(S) distillery effluent(DE), paper mill effluent(PE) and sugar mill effluent(SE)?

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. SE$<$PE$<$S$<$DE

  2. PE$<$S$<$SE$<$DE

  3. S$<$DE$<$PE$<$SE

  4. SE$<$S<$PE$<$DE

Show answer
Correct Option: B
Explanation:
  • BOD is the Biological Oxygen Demand that is created when there is an excessive quantity of the organic matter in the water body and its decomposition is initiated by the decomposing bacteria. More the amount of organic waste, the higher will be the BOD and so more will be pollution in the water body. 
  • This causes an extreme reduction in the dissolved oxygen and suffocates the aquatic animals. 
  • Distillery effluent is rich in organic waste left from alcoholic fermentation and it has the highest BOD. 
Sugar mill effluent follows the distillery effluent in the concentration of organic content. The sewage water contains the excreta and detergents mixed with it. 
  • Papermill effluent has the lowest concentration of the organic mass.

Hence, the correct answer is 'PE< S< SE< DE'.

Arrange according to ascending order of BOD.
(a) Highly polluted pond water
(b) Unpolluted pond water
(c) Distilled water

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. b-c-a

  2. c-b-a

  3. c-a-b

  4. a-c-b

Show answer
Correct Option: B
Explanation:

The concentration of the organic waste and its subsequent decomposition determines the BOD of the water. If the organic concentration is high, there will be high BOD because more dissolved oxygen will be used to breakdown the organic mass by the bacteria. So, high BOD marks high pollution. Distilled water has no content of the organic substances as it has been treated and filtered. Unpolluted water pond will not have polluted source of organic mass but the existing organisms die and their dead bodies contribute to a little raised BOD. Highly polluted water will show a very high value of BOD as it will take a lot of dissolved oxygen to breakdown the organic mass in water body. So, distilled water is least polluted, followed by unpolluted pond water and then highly polluted pond water.

Hence, the correct answer is 'c - b - a'.

A large quantity of urban sewage is drained to a nearby river. Which among the given conditions would happen after mixing of sewage into the river?
(i) BOD of receiving water body increases.
(ii) DO of receiving water body decreases.
(iii) It will not cause mortality among fishes and other aquatic creatures.
(iv) It will lead to nutrient enrichment of receiving water body.

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. i, ii and iii

  2. i, ii and iv

  3. ii and iii

  4. iii and iv

Show answer
Correct Option: B
Explanation:

A large quantity of urban sewage will have a large amount of organic and inorganic material. Due to this, the decomposition of the organic mass will initiate the use of dissolved oxygen and so, the DO of receiving water body decreases. This will cause increase in the biological oxygen demand (BOD) by the decomposing bacteria. As the DO decreases, the aquatic animals will suffocate and die. Also, the inorganic nutrients, as well as the decomposed nutrients, will cause lush growth of algae, causing algal bloom over the surface of the water, which will further decrease the DO by not allowing the mixing of atmospheric oxygen.

Hence, the correct answer is 'i, ii, iv'

Polluting strength of sewage is characterised by its

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. BOD

  2. Ozone content

  3. Nitrogen content

  4. Eutrophication

Show answer
Correct Option: A
Explanation:

The BOD test measures the amount of dissolved oxygen in the water that is used up due to the breakdown of organic pollutants, such as sewage, in a certain number of days. Raw sewage has a BOD of forty to 150 milligrams per litre, whereas drinking water has a BOD of less than 0.5 milligrams per litre. The BOD indicates the content of oxygen needed to decompose organic compounds in wastewater by bacteria.

So the correct answer is 'BOD'.

Relation between DO and BOD is that they

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Are directly proportional

  2. Are inversely proportional

  3. Are not related

  4. Always remain equal to each other

Show answer
Correct Option: B
Explanation:

Biological Oxygen Demand (BOD) is a measure of the oxygen used by microorganisms to decompose this waste. This results in a high BOD level. When BOD levels are high, dissolved oxygen levels decrease because the oxygen that is available in the water is being consumed by the bacteria.

So the correct answer is 'Are inversely proportional'.

A river/ lake with an inflow of domestic sewage rich in organic waste may result in

biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. Death of fish due to lack of oxygen

  2. Drying of the river/lake very soon due to algal bloom

  3. Increase population of aquatic food web organisms

  4. An increased production of fish due to biodegradable nutrients

Show answer
Correct Option: A
Explanation:

A river with an inflow of domestic sewage rich in organic waste will reduce the dissolved oxygen (DO). The organic waste will increase biological oxygen demand of the river thus depleting the O2 content and may result in the death of fish due to lack of oxygen.

So the correct answer is 'Death of fish due to lack of oxygen'.