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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

In the polluted water, the values of

  1. C.O.D. slightly higher than B.O.D.

  2. C.O.D. much higher than B.O.D.

  3. B.O.D. slightly higher than C.O.D.

  4. B.O.D. much higher than C.O.D.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Chemical Oxygen Demand (COD) measures the total amount of oxygen required to chemically oxidize all organic matter, whereas BOD only measures biodegradable organic matter. Therefore, COD is almost always higher than BOD.

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

When huge amount of CO$ _2$ is dumped into a river, the BOD will

  1. Increase

  2. Slightly decrease

  3. Remain unchanged

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

Biological Oxygen Demand is a measurement of the amount of dissolved oxygen that is used by aerobic microorganisms when decomposing organic matter in water.  It is expressed in milligrams of oxygen consumed per liter of the sample during 5 days of incubation at 20°C and is used to determine the degree of organic pollution of water. Hence when a huge amount of carbon dioxide is added BOD will not be affected. Thus, the correct answer is option C.

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

A rapid growth of photosynthetic algae in water develops 'bloom'. How would it affect the environment of water?

  1. The environment becomes comfortable for all forms of life.
  2. O$ _2$ level is decreased or BOD becomes high.
  3. O$ _2$ level of water is increased.

  4. Fish production is increased.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Algal blooms lead to excessive organic matter. As this matter decomposes, aerobic bacteria consume dissolved oxygen, leading to a decrease in O2 levels and an increase in BOD, which harms aquatic life.

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

For how long and at what temperature an experiment is run to determine the value of BOD of a water body? 

  1. $10^oC$ for 10 days
  2. $20^oC$ for 5 days
  3. $20^oC$ for 2 days
  4. $5^oC$ for 20 days
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

BOD or biochemical oxygen demand is the amount of dissolved oxygen which is required by the aerobic organisms during the decomposition of organic matter. The BOD is measured at a specific temperature and specific period of time. BOD value is represented in the form of oxygen which is consumed per litre of the sample used for testing. The sample is tested before and after 5 days of incubation at 20 °C. The value describes the amount of organic material present in the contaminated or waste water. 

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

Which of the following enhances B.O.D. of water ?

  1. Sugar mill effluents

  2. Algae

  3. Sand

  4. Moss
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation
B.O.D. or Biochemical oxygen demand is the amount of dissolved oxygen which is required by the aerobic organisms during the decomposition of organic matter. It is measured at a specific temperature and specific period of time. The wastes from the sugar mill effluents are directly poured into the water bodies which enhances the demand of required oxygen to completely oxidize the organic compounds to carbon dioxide which leads to overall increase in biochemical oxygen demand.
Thus, the correct answer is option A.
Multiple choice biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

The measurement of rate of oxygen utilisation by a unit volume of water over a period of time is to measure.

  1. Biochemical oxygen demand

  2. Biosynthetic path

  3. Biogas generation

  4. Fermentation
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

BOD or Biochemical oxygen demand is the amount of dissolved oxygen which is required by the aerobic organisms during the decomposition of organic matter. The BOD is measured at a specific temperature and specific period of time. BOD value is represented in the form of oxygen which is consumed per litre of the sample used for testing. The sample is tested before and after 5 days of incubation at 20 °C. The value describes the amount of organic material present in the contaminated or waste water. 

Thus, the correct answer is option A. 

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

Water pollution can be identified by testing its

  1. PH level

  2. Biological Oxygen Demand (BOD)

  3. Both a and b

  4. None of these
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Water pollution can be identified by testing its PH level and Biological Oxygen Demand (BOD)  Water pollution is the contamination of water bodies (e.g. lakes, rivers, oceans, aquifers and groundwater). This form of environmental degradation occurs when pollutants are directly or indirectly discharged into water bodies without adequate treatment to remove harmful compounds. Acid rains, dumping of chemicals into the water by individuals, industries, and communities.; steam from coal mine drainage etc affect the pH of the water in its reservoir. Thus by testing the pH of water, on the scale from 1 to 14, the pollution in water can be identified.  Biochemical oxygen demand is a measure of the quantity of oxygen used by microorganisms (e.g., aerobic bacteria)  in the oxidation of organic matter. This value varies with the amount of pollution in water hence pollution can be determined by BOD.

So, the correct answer is 'Both a and b'.

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

Biochemical Oxygen Demand (BOD) in a river water

  1. Remains unchanged when algal bloom occurs.

  2. Has no relationship with concentration of oxygen in the water.

  3. Gives a measure of salmonella in the water.

  4. Increases when sewage gets mixed with river water.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Sewage is waste water having food residue, animal and human excreta, detergent, discharges from industrial and commercial establishments. Degree of impurity of water due to organic matter is measured in terms of BOD or biochemical oxygen demand. BOD is the oxygen in milligrams required for 5 days in one litre of water at 20 degree centigrade for the micro organisms to metabolise organic wastes. If the water, is polluted with sewage and other organic wastes, the BOD will increase.

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

BOD stands for

  1. Biological organism death

  2. Biochemical organic matter decay

  3. Biotic oxidation demand

  4. Biochemical oxygen demand
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Biochemical Oxygen Demand (BOD) is the oxygen in milligrams required  for 5 days in one litre of water at 20 degree centigrade for the micro organisms to metabolise organic wastes present in water.

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

Which of the following does not occur when the sewage is discharged into water?

  1. Increase in $O _2$

  2. Cyanophycean blooms occur
  3. Depletion of $O _2$ layers

  4. Eutrophication
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Decomposition of organic matter by microbes requires oxygen. Degree of impurity of water due to organic matter is measured in terms of Biochemical oxygen demand or (BOD). 

BOD is the oxygen required by microorganisms to completely metabolise organic wastes present in water. 
When untreated sewage is directly discharged into water bodies, it is called organic loading. Organic loading is one source for increased nutrient concentration in water bodies (or eutrophication). It results in increase in BOD and explosive multiplication of blue green alga, called as algal bloom. Algal bloom and increased consumption of oxygen by sewage metabolising microorganisms results in decrease in level of dissolved oxygen in water.