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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 a sewage plant, BOD is indicated as high. After sometime it shows a decrease then

  1. There is increase in bacterial growth but decrease in oxygen.

  2. There is decrease in bacterial growth but increase in oxygen.

  3. There is increase in bacterial growth but increase in oxygen.

  4. There is decrease in bacterial growth but decrease in oxygen.
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. BOD can be used as a gauge of the effectiveness of wastewater treatment plants. It is listed as a conventional pollutant in the U.S. Clean Water Act.

Higher the BOD, more is the pollution.
Thus, if BOD had reduced, it shows decrease in bacterial growth which consumes the oxygen present and ensures increase in oxygen level.
Therefore, 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

When domestic sewage mixes with river water 

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

  2. The increased microbial activity release 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

Domestic sewage primarily contains biodegradable organic matter, which readily decomposes by bacteria and other microorganisms, which can multiply using these organic substances as substrates and hence, utilise some of the components of sewage. It is possible to estimate the amount of biodegradable organic matter in sewage water by measuring biochemical oxygen demand (BOD). Microorganisms involved in biodegradation of organic matter in the receiving water body consume a lot of oxygen, and as a result there is a sharp decline in dissolved oxygen downstream from the point of sewage discharge. This causes mortality of fish and other aquatic creatures. 

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

High BOD indicates

  1. Highly polluted $H _2O$
  2. Less pollution in $H _2O$

  3. Less sewage

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

Biological oxygen demand (BOD) is the rate at which microorganisms in water take up oxygen. A high BOD indicates two things - there is a high level of microorganisms in the water and there is a high content of organic material in the water that is broken down by the organisms. This is an indication of organic pollution.

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

BOD (biological oxygen demand) is

  1. Amount of oxygen consumed by microorganisms for decaying organic matter per unit volume of water

  2. Amount of CO consumed by microorganisms per unit of sewage water

  3. Amount of oxygen required by aquatic plants for survival

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

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. Biochemical oxygen demand is the amount of oxygen required for microbial metabolism of organic compounds in water.

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

Which one of the following statement is true?

  1. The greater the BOD of waste water, more is its polluting potential.

  2. The greater the BOD of waste water, less is its polluting potential.

  3. The lesser the BOD of waste water, more is its polluting potential.

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

BOD(Biochemical Oxygen Demand) which is defined as amount of dissolved oxygen needed by aerobic biological organisms to break down organic material present in a given water sample at certain temperature over a specific time period. Therefore, the greater the BOD of waste water, more is its polluting potential. 

Therefore, 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

Biological Oxygen Demand (BOD) is a measure of 

  1. Industrial wastes poured into water bodies

  2. Extent to which water is polluted with organic compound

  3. Amount of carbon monoxide inseparably combined with haemoglobin

  4. Amount of oxygen needed by green plants during night
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biochemical oxygen demand (BOD) is the amount of dissolved oxygen needed by aerobic biological organisms in a body of water to break down organic material present in a given water sample at certain temperature over a specific time period. It is used as a measure of the degree of water pollution. 

Therefore, 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

At DO below $4$ mg/$l$, water at normal temperature is considered as

  1. Heavily polluted

  2. Moderately polluted

  3. Little polluted

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

Dissolved oxygen (DO) refers to the amount of oxygen dissolved in the water. It depends on the following factors:

1. Temperature- colder the temperature, more will be the DO.
2. Pressure- greater the pressure, more will be the DO.
3. Salinity- lower the salinity, more will be the DO.
The levels of DO below 5mg/l is considered to be hazardous to the aquatic lives. At normal temperature, any water body showing less DO than 5mg/l will be highly polluted.
Hence, the correct answer is 'Heavily Polluted'

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

Fish die in water bodies polluted by sewage due to

  1. Pathogens

  2. Clogging of gills by silt

  3. Reduction in oxygen

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

 Oxygen enters the water through diffusion and water has the highest potential to hold oxygen. The high temperature, untreated sewage having biotoxins, hazardous waste can reduce the oxygen to an alarming level leading to the hypoxia in fishes, whereafter enduring at the maximum level they die resultantly. This occurs because the untreated sewage is rich in organic matter and microbes utilize the dissolved oxygen for the decomposition called biological oxygen demand (BOD). The more the value of BOD, the lesser will be the oxygen in the water.

Hence, the correct answer is 'Reduction in oxygen'.

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

Phosphate pollution is caused by _______.

  1. Weathering of phosphate rocks only

  2. Agriculture fertilizers

  3. Phosphate rocks and sewage

  4. Sewage and agricultural fertilizers
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Phosphate pollution in the water is directly related to the release of the untreated sewage and agriculture fertilizers into the water body. This results in excessive algal bloom that forms a thick layer on the surface of the water and prevents the sunlight and oxygen from getting into the water. As a result, the underlying aquatic animals and plants suffocate and die. When this algal bloom dies, it further enhances the eutrophication process, greatly decreasing the dissolved oxygen in the water.

Hence, the correct answer is 'Sewage and agricultural fertilizers'.

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

B.O.D. is connected with

  1. Organic matter

  2. Microbes

  3. Microbes and organic matter

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

BOD refers to the biological oxygen demand by the microbes to decompose the organic matter present in the water body. Oxygen enters the water through diffusion and water has the highest potential to hold oxygen. The high temperature, untreated sewage having biotoxins, hazardous waste can reduce the oxygen to an alarming level leading to the hypoxia in fishes, whereafter enduring at the maximum level they die resultantly. This occurs because the untreated sewage is rich in organic matter and microbes utilize the dissolved oxygen for the decomposition.

So, the correct answer is 'Microbes and organic matter'