Environmental Studies · General Awareness

Water Quality and Pollution

1,263 Questions

Water Quality and Pollution examines the sources, mechanisms, and impacts of contaminants in aquatic ecosystems. It covers crucial environmental concepts like eutrophication, biochemical oxygen demand, and thermal pollution. This subject frequently appears in general science and environmental studies sections of various examinations.

Eutrophication CausesThermal Pollution EffectsBiochemical Oxygen DemandSynthetic Fertilizer ImpactsWastewater SourcesAquatic Ecosystem Toxicity

Water Quality and Pollution Questions

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

BOD of wastewater is amount of

  1. total organic matter

  2. biodegradable organic matter

  3. oxygen evolution

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

biological oxygen demand is the amount of Oxygen required by aerobic micro-organisms for the breakdown of organic matter present in waste water or polluted water.

So, the correct answer is 'oxygen consumption'

Multiple choice biology natural resources and agriculture effects of water pollution effect of water pollution water pollution and its control

Measurement of the rate of oxygen consumption in unit volume of water over a period of time is done to find out

  1. Biogas generation

  2. Biological oxygen demand

  3. Biosynthetic pathways

  4. Fermentation
Reveal answer Fill a bubble to check yourself
B 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 'Biological Oxygen Demand (BOD)'. BOD is the oxygen in milligrams required for 5 days in 1 litre of water at 20 degree centigrades for the microorganisms to metabolise organic wastes.

Multiple choice biology natural resources and agriculture 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 compounds.

  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

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.

Multiple choice biology natural resources and agriculture effects of water pollution effect of water pollution water pollution and its control

Huge quantity of sewage is dumped in a river. The BOD will.

  1. Increase

  2. Decrease

  3. Slightly decrease

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

A huge quantity of sewage increases Organic matter in the river water.

The oxygen demand by bacteria to degrade the organic matter increases.
The biological oxygen demand increases.
So, the correct option is 'Increase'.

Multiple choice biology natural resources and agriculture effects of water pollution effect of water pollution water pollution and its control

Biochemical oxygen demand measures

  1. Industrial pollution

  2. Air pollution

  3. Dissolved oxygen required for decomposers

  4. Pollution capacity of effluents
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation
Biochemical oxygen demand or BOD is the amount of oxygen required 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.
So, BOD measures the amount of dissolved oxygen required for decomposers to decompose the organic matter in the water.
So, the correct answer is 'Dissolved oxygen required for decomposers'.
Multiple choice biology natural resources and agriculture effects of water pollution effect of water pollution water pollution and its control

Multiple Choice Questions
Biochemical oxygen demand may not be good index for water bodies receiving effluents from.

  1. Sugar industry

  2. Domestic sewage

  3. Dairy industry

  4. Petroleum industry
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Biochemical Oxygen Demand or BOD is the amount of dissolved oxygen in a water body, required by microorganisms for the aerobic breakdown of organic matter in the water. Petroleum waste consists of inorganic constituents that also may cut off the oxygen supply into the water body thus BOD may not be a good index for water receiving effluents containing it.

So, the correct option is 'petroleum industry'.

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

If a water body have high amount of DDT it's 'Biochemical Oxygen Demand' (B.O.D.) will

  1. Decrease

  2. Not affected

  3. Increase

  4. First decrease than increase
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Biological Oxygen Demand (BOD) is one of the most common measures of pollutant organic material in water. BOD indicates the amount of putrescible organic matter present in water. Therefore, a low BOD is an indicator of good quality water, while a high BOD indicates polluted water. When BOD levels are high, dissolved oxygen (DO) levels decrease because the oxygen that is available in the water is being consumed by the bacteria. Since less dissolved oxygen is available in the water, fish and other aquatic organisms may not survive.


So, the correct option is 'Increase'.

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

The enhanced growth of water hyacinth in lakes can be due to

  1. Disposal of solid wastes in water bodies

  2. Availability of more nutrients to the flora of a water ecosystem

  3. Discharge of sewage into water bodies

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

Water hyacinth (Eichhornia crassipes) also known as Bengal terror is waterweed often blamed for choking water bodies and creating problems for aquatic plants and animal due to less availability of oxygen. It mainly grows where organic nutrient is present in large amount. Level of the nutrient increase due to use of pesticide, weedicides, of discharge of sewage into the water bodies. 

So, the correct option is 'all of the above'.

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

BOD of lake becomes high by :-

  1. Vehicles

  2. Wind mill

  3. Smoke and ammonia

  4. Detergents
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation
BOD or biological oxygen demand is the amount of water needed by aerobic organisms to break down the organic substances (waste substances) present in a water body. Detergents reduce the amount of oxygen in a water body. This may result in an increase in the BOD. It may also result in an increase in eutrophication in the water bodies. Vehicles, wind mill, and smoke and ammonia on the other hand act mostly as air pollutants and are responsible for air pollution.
So, the correct answer is 'Detergents'.
Multiple choice biology human influences on the environment effects of water pollution effect of water pollution water pollution and its control

If the river water is polluted with domestic sewage and garbage, it leads to the depletion of 

  1. CO$ _2$

  2. CO
  3. O$ _2$

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

A lake rich in domestic sewage and garbage nutrients will leads to eutrophication. Eutrophication is when the environment becomes enriched with nutrients. This can be a problem in aquatic habitats such as lakes as it can cause algal blooms and other aquatic plants. Following this, overcrowding occurs and plants compete for sunlight, space and oxygen. It deoxygenate the water enough to kill the fish and other animals. 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

If BOD of river is high, it means that the river 

  1. Is not polluted

  2. Is very polluted

  3. Does not have green plants

  4. Get least amount of light
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biochemical oxygen demand is a measure of how much dissolved oxygen is being consumed as microbes break down organic matter. A high demand, therefore, can indicate that levels of dissolved oxygen are falling, with potentially dangerous implications for the river's biodiversity. High biochemical oxygen demand can be caused by: high levels of organic pollution, caused usually by poorly treated waste water; high nitrate levels, which trigger high plant growth. Both result in higher amounts of organic matter in the river. When this matter decays, the microbiological activity uses up the oxygen.

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 compounds

  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 is a measure of how much dissolved oxygen is being consumed as microbes break down organic matter. A high demand, therefore, can indicate that levels of dissolved oxygen are falling, with potentially dangerous implications for the river's biodiversity. High biochemical oxygen demand can be caused by high levels of organic pollution, caused usually by poorly treated wastewater; high nitrate levels, which trigger high plant growth. 

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' (BOD) is a method used for  

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

  2. Measuring the activity of Saccharomyces cervisae in producing curd on a commercial scale.

  3. Working out the efficiency of RBCs, about their capacity to carry oxygen.

  4. Working out the efficiency of oil driven automobile engines.
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Biochemical oxygen demand (BOD) is the amount of oxygen, expressed in mg/L or parts per million (ppm), that bacteria take from water, when they oxidize organic matter. 

Bacteria in water live and multiply when organic matter is available for food and oxygen is available for oxidation. About one-third of the food bacteria consumed becomes the solid organic cell material of the organisms. The other two-thirds is oxidized to carbon dioxide and water by the biochemical action of the bacteria on the oxygen dissolved in the water. Micro-organisms 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

BOD is

  1. The-amount of $O _2$ utilised by organisms in water
  2. The amount of $O _2 $ utilised by micro organisms for decomposition
  3. The total amount of $O _2 $ present in water

  4. All of the above
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. 

Micro-organisms 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.