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

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

  1. Drying of the lake very soon due to algal bloom.

  2. An increased production of fish due to lot of nutrients.

  3. Death of fish due to lack of oxygen.

  4. Increased population of aquatic food web organisms.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Domestic sewage leads to organic loading or occurrence of excess organic matter inside water. Its putrefaction decreases dissolved oxygen. Blue green algae present in the bloom also release toxins. Both toxicity and decreased oxygen level kill aquatic animals. Anaerobic putrefaction produces pollutants like methane, hydrogen sulphide, and ammonia. They kill the bloom forming plants as well. The water body comes to have foul smell, brown colouration, bad taste and oil.

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

Bio-indicators are used for

  1. Oxygen demand

  2. Air pollution

  3. Mineral present

  4. All of the above
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Bioindicators are organisms, which have a special requirement for some specific mineral or abiotic factor or show some specific response to a particular abiotic factor. Thus, they are good indicators of environmental health. Oxygen demand, presence of minerals, occurrence of petroleum products, radioactive minerals and pollution etc. are some of the responses that can be detected using bioindicators. Lichens are very sensitive to air pollution specially due to sulphur oxides and do not grow in areas having high sulphur dioxide pollution. It is a very commonly used bio-indicator.

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

Increase of BOD in water leads to

  1. Increase in the dissolved O$ _{2}$ concentration.
  2. Decrease in the dissolved O$ _{2}$ concentration.
  3. Maintenance of dissolved O$ _{2}$ concentration at the same level.
  4. No effect on dissolved O$ _{2}$ concentration.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction. Explosive multiplication of alga leads to algal bloom. These conditions result in decrease in dissolved oxygen in water. Both toxicity due to algal toxins and decreased levels of dissolved oxygen kill aquatic animals.

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

What will be the effect of addition of organic material on water?

  1. COD remain unaffected

  2. BOD remain unaffected

  3. Increases BOD

  4. Reduces BOD
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Decomposition of organic matter by microbes requires oxygen. Degree of organic impurity of water is measured in terms of 'Biological Oxygen Demand' or BOD. BOD is the oxygen in milligrams required by microorganisms to metabolise organic wastes. When more organic matter are added to water, the BOD of the water will increase.

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

When domestic sewage mixes with river water

  1. Small animals like rats will die after drinking river water.

  2. The increased microbial activity releases micro nutrients such as iron.

  3. The increased microbial activity uses up dissolved oxygen.

  4. The river water is still suitable for drinking as impurities are only about 0.1%.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Organic loading is occurrence of excess organic matter inside water due to sewage disposal and eutrophication. This leads to an increase in biological oxygen demand (BOD) for putrefaction by microorganisms. Also explosive multiplication of blue green alga leads to algal bloom. These conditions result in decrease in dissolved oxygen in water. Both toxicity due to algal toxins and decreased levels of dissolved oxygen kill aquatic animals.

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

Measuring 'Biochemical Oxygen Demand' is used for

  1. Estimating the amount of organic matter in sewage water.

  2. Working out the efficiency of oil driven automobile engines.

  3. Measuring the activity of Saccharomyces cerevisiae in producing curd on a commercial scale.

  4. Working out the efficiency of R.B.Cs. about their capacity to carry oxygen.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Degree of pollution or impurities in water due to organic matter is measured in terms of 'Biological Oxygen Demand' or BOD. Biological oxygen demand or BOD is the oxygen in milligrams required for five days in one litre of water at 20 degree centigrades for the microorganisms to metabolise organic waste. 

Low pollution level is indicated by below 1500 mg/lit, medium pollution level is indicated by 1500 to 4000 mg/lit and high organic pollution level is indicated by above 4000 mg/lit.

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

Which of the option shows following examples in ascending order in terms of BOD?
(i) Distilled water (ii) Tap water(iii) Sewage wastes drained in river

  1. ii- i- iii

  2. i- ii- iii

  3. iii- i- ii

  4. iii- ii- i
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

BOD is the oxygen required by microorganisms to metabolise organic wastes in the water. Biological treatment of wastewater will reduce the organic impurities or an organic load of polluted water, thus curtail the level of BOD. The greater the content of organic waste in the water greater will be the BOD. Organic waste will be maximum in the sewage waste. Hence it will have the highest BOD. Thus the correct answer is option B.

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

Study the lists and find the correct match.

I II
(a) BOD (i) Treatment of sewage
(b) KVIC (ii) Measure of organic matter in water
(c) LAB (iii) Biological methods for controlling plant diseases
(d) STPS (iv) Increases vitamin B$ _{12}$
(v) Production of biogas

  1. a-iv, b-iii, c-ii, d-v

  2. a-v, b-ii, c-iii, d-i

  3. a-ii, b-i, c-iv, d-v

  4. a-ii, b-v, c-iv, d-i
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

BOD-Biological oxygen demand is the measure of organic matter in water

KVIC-Khadi and Village Industries Commission helps in production of biogas
LAB-Lactic acid bacteria in milk help in increasing vit B12 .
STPS-Sewagw treatment plants are used for treatment of sewage.
Correct answer-D

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

Limit of BOD prescribed by Central Pollution Control Board for the discharge of industrial and municipal waste waters into natural surface waters, is -

  1. < 3.0 ppm

  2. <10 ppm

  3. < 100 ppm

  4. < 30 ppm
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

BOD is Biological oxygen demand. It is the total amount of oxygen required by the microorganisms present in a water body to break down the organic matter. If BOD is more, it means that there is abundance of microorganisms in that water body and hence it is polluted with organic matter.

Water with BOD level 1 - 2 ppm is considered to be good water, if the BOD is 3 - 9, then the water is considered to be slightly polluted, and if the water has BOD more than 100 ppm, then the water is greatly polluted.
The Central Pollution Control Board has prescribed the limit of BOD for the discharge of industrial and municipal waste in order to regulate the water pollution and for efficient water treatment, and it is <10 ppm.

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

Drained sewage has B.O.D.

  1. More than that of water

  2. Less than that of water

  3. Equal to that of water

  4. None of the above
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

BOD refers to the biological oxygen demand by the microbes to decompose the organic matter present in the water body. The drained sewage is rich in organic waste that will be decomposed by the bacteria. So, the drained sewage will be deficient in oxygen than the normal water. The oxygen demanded by the microbes will be higher in sewage water.

Hence, the correct answer is 'More than that of water'.