Tag: human influences on the environment

Questions Related to human influences on the environment

BOD level in fresh water should not exceed beyond

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

  1. $5$ ppm

  2. $10$ ppm

  3. $25$ ppm

  4. $50$ ppm

Show answer
Correct Option: A
Explanation:
BOD or Biochemical Oxygen Demand is the amount of oxygen required to decompose organic matter present in one litre of polluted water.
More the value of BOD,more will be the amount of organic matter in the water. Hence, a high BOD value means heavily polluted water.
Water with BOD value of 1-2 ppm is considered clean. 
In freshwater, BOD value should not exceed 5 ppm as the dissolved oxygen will be used up in the decomposition of organic matter and will not be available for the survival of aquatic organisms which will lead to their death.
So, the correct answer is '5 ppm'. 

When domestic sewage mixes with river water, __________

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

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

  2. The increased microbial activity released micronutrients 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 $0.1\%$

Show answer
Correct Option: C
Explanation:

Domestic sewage contains large amounts of organic matter. When domestic sewage mixes with river water, organic matter will content will increase in the river. This will lead to increase in BOD or Biochemical Oxygen Demand. 

BOD is the amount of oxygen required by bacteria to decompose organic matter in one litre of polluted water.
If the water is more polluted, more will be the BOD because more will be the organic matter present in it and hence, more oxygen will be required to decompose it.
Hence, the dissolved oxygen will be used up by the bacteria to decompose the organic matter.
So, the correct answer is 'The increased microbial activity uses up dissolved oxygen'.

Match and find the correct option.

I II III
(a) BOD (i) Supernatant as effluent (p) Useful aerobic microbes 
(b) Flocs (ii) Measure of organic matter (q) All settled solids
(c) Primary sludge (iii) Masses of bacteria associated with fungi (r) Methane hydrogen sulphide carbon dioxide
(d) Biogas (iv) Anaerobic sludge digester (s) Polluting water has more BOD
biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

  1. a-ii-s, b-iii-p, c-i-q, d-iv-r

  2. a-ii-p, b-i-r, c-iv-q, d-iii-s

  3. a-i-s, b-iii-q, c-iv-p, d-ii-r

  4. a-iv-r, b-ii-s, c-iii-p, d-i-q

Show answer
Correct Option: A
Explanation:

(a)BOD - (ii)Measure of organic matter-(s)Polluting water has more BOD-Biochemical Oxygen Demand is the amount of dissolved oxygen needed by aerobic microbes to break down organic material present in a given water sample at certain temperature over a specific time period. Polluting water has more organic matter thus required more oxygen for the breakdown. Hence polluting water has more BOD.

(b)Flocs- (iii)Masses of bacteria associated with fungi -(p)Useful aerobic microbes-Flocs are the masses of bacteria associated with fungi. Flocs are helpful in increasing the decomposition rate and are put in the aeration tank while the secondary sewage treatment process is in effect
(c)Primary sludge-(i)Supernatant as effluent-(q)All settled solids-Primary sludge includes settleable solids removed during primary treatment in primary clarifiers.
(d)Biogas-(iv)Anaerobic sludge digester-(r)Methane, hydrogen sulfide, carbon dioxide-Biogas is the mixture of gases(Methane, hydrogen sulfide, carbon dioxide)- produced by the breakdown of organic matter in the absence of oxygen(I.e from anaerobic sludge digesters).

Water above the dissolved $O _2$ content may be considered uncontaminated.

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

  1. $0.8$ mg/l

  2. $0.008$ mg/l

  3. $8.0$ mg/l

  4. 8 $\mu$g/l

Show answer
Correct Option: C
Explanation:
The microorganisms in water decompose organic matter using dissolved oxygen. More the amount of dissolved oxygen in the water, more is its purity and vice versa. Water below 5mg/l is considered contamined and water above 8mg/l is considered as uncontaminated.

So, the correct answer is "8.0mg/l".

Water pollination is best assessed by determining.

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

  1. DO and BOD

  2. BOD and turbidity

  3. Do and acidity

  4. BOD and alkalinity

Show answer
Correct Option: A
Explanation:

 D.O. is the dissolved gaseous form of oxygen that is essential for respiration of fish and other aquatic organisms. Wastewater from sewage treatment plants often contains organic materials that are decomposed by microorganisms. The amount of oxygen consumed by these organisms in breaking down the waste is known as the biochemical oxygen demand or BOD. BOD directly affects the amount of dissolved oxygen in rivers and streams. The greater the BOD, the more rapidly oxygen is depleted in the stream, thus reducing the oxygen available to higher forms of aquatic life. Pollution, therefore, increases the BOD of a water body. So, the water pollution status of a water body can be assessed by studying the dissolved oxygen (DO) and biological oxygen demand (BOD) of the water body. So, the correct option is 'DO and BOD'.

Two bottles were half filled with water from Ganga ('P') and Kaveri ('Q') and kept under identical airtight conditions for 5 days. The oxygen was determined to be 2% in bottle ('P') and 10% in bottle ('Q'). What could because of this indifference?

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

  1. Ganga is more polluted than Kaveri

  2. Both the rivers are equally polluted

  3. Kaveri is more polluted than Ganga

  4. Kaveri has more minerals than Ganga

Show answer
Correct Option: A
Explanation:
Biochemical oxygen demand or BOD is the amount of dissolved oxygen needed by the aerobic bacteria present in water in a given amount of time. Given that 'P' has 2% oxygen and 'Q' has 10% oxygen dissolved after 5 days in an airtight condition. So, one can conclude that the aerobic bacteria present in 'P' is more than 'Q' as BOD of 'P' is much more than 'Q'. So Ganga is more polluted than Kaveri.    

Consider the following statements regarding the ecosystem which helps in reducing the level of pollution in the atmosphere.
$1$. Ecosystems and ecological processes play an important role in maintenance of gaseous composition of the atmosphere, breakdown of wastes and removal of pollutants.
$2$. Some ecosystems, especially wetlands have the ability to breaking down and absorb pollutants.
$3$. Natural and artificial wetlands are being used to filter effluents to remove nutrients, heavy metals, suspended solids; reduce the BOD (Biological Oxygen Demand) and destroy harmful micro-organisms.
Which of the statements given is/are correct?

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

  1. $1$ only

  2. $1$ and $2$

  3. $2$ and $3$

  4. All of the above

Show answer
Correct Option: D
Explanation:
Ecosystems and ecological processes play an important role in the maintenance of gaseous composition of the atmosphere, breakdown of wastes and removal of pollutants.  Some ecosystems, especially wetlands have the ability to breaking down and absorb pollutants. Constructed wetlands are a sanitation technology that has not typically been designed for pathogen removal, but instead, have been designed to remove other water quality constituents such as suspended solids, organic matter (BOD/COD) and nutrients (nitrogen and phosphorus). Thus, all of these statements are true.

So the correct option is 'All of the above'.

Multiple Choice Questions
BOD in river water

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

  1. Remains unchanged when algal bloom occurs

  2. Increases when sewage gets mixed up with river water

  3. Has no relationship with concentration of oxygen in water

  4. Give a measure for Salmonella in water.

Show answer
Correct Option: B
Explanation:

Biochemical Oxygen Demand or BOD is the amount of dissolved oxygen needed by aerobic microbes to break down organic matter present in a particular water sample at a certain temperature over a specified period of time. Value of BOD increases, given that the organic matter content is high in the water sample. Sewage is rich in organic residues thus it increases BOD of river water upon mixing.

So, the correct answer is option B, increases when sewage gets mixed up with river water.

Multiple Choice Questions
BOD is a measure of

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

  1. Industrial wastes passed into water bodies

  2. amount of carbon monoxide combined with haemogloblin

  3. extent of pollution with organic matter

  4. amount of oxygen required by plants during night.

Show answer
Correct Option: C
Explanation:

BOD or Biochemical Oxygen Demand measures the degree of impurity of a water body or sample due to organic matter. BOD is the amount of dissolved oxygen needed by aerobic microbes to breakdown the organic matter present in the water body.

So, the correct answer is extend of pollution with organic matter.

Disposal of sewage and industrial effluents into water bodies, resulting in contamination of

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

  1. Soil

  2. Water

  3. Air

  4. Atmosphere

Show answer
Correct Option: B