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

What is/are the impact(s) of thermal pollution on water bodies?

  1. Alteration in reproduction patterns of fishes
  2. Killing of fish near the discharge source
  3. Increase in the ability of water to hold dissolved oxygen

  1. Both 1 and 2

  2. Both 2 and 3

  3. Only 2

  4. Only 3
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The discharge of heated water into a waterway often causes ecological imbalance, sometimes resulting in major fish kills near the discharge source. The increased temperature accelerates chemo-biological processes and decreases the ability of water to hold dissolved oxygen. Thermal changes affect the aquatic system by limiting or changing the type of fish and aquatic biota that is able to grow or reproduce in the waters.

Multiple choice

Consider the following facts:

  1. Elements like nitrogen and phosphorus are essential for aquatic habitat.
  2. Excess of nitrogen and phosphorus leads to faster ageing of water bodies.

Which of the above is/are true?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Although essential to the aquatic habitat, nutrients such as nitrogen and phosphorus may also cause over fertilisation and accelerate the natural ageing process (eutrophication) of lakes. This acceleration in turn produces an overgrowth of aquatic vegetation, massive algal blooms and an overall shift in the biologic community from low productivity with many diverse species to high productivity with large numbers of a few species of a less desirable nature.

Multiple choice

Consider the following facts:

  1. Stock pollutants are those, the emission of which falls short of the absorptive capacity of nature.
  2. Organic pollution in waterways can be transformed into less harmful inorganic matter by bacteria in the waterways.

Which of the above is/are true?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

The absorptive capacity refers to the environment's ability to absorb waste products. If emissions exceed the absorptive capacity of the system, they will accumulate in the environment and cause damage. A stock pollutant is a pollutant for which the environment has little or no absorptive capacity.

Multiple choice

Consider the following facts:

  1. Hypoxia is a condition of aquatic habitats which is encouraged as a result of pollution and eutrophication.
  2. In Hypoxic water, concentration of dissolved oxygen shoots up exponentially.

Which of the above is/are true?

  1. Only 1

  2. Only 2

  3. Both 1 and 2

  4. Neither 1 nor 2
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Hypoxia refers to low oxygen conditions. Oxygen depletion is a phenomenon that occurs in aquatic environments as dissolved oxygen (DO; molecular oxygen dissolved in the water) becomes reduced in concentration to a point where it becomes detrimental to aquatic organisms living in the system. Oxygen depletion can result from a number of natural factors, but is most often a concern as a consequence of pollution and eutrophication in which plant nutrients enter a river, lake or ocean, and phytoplankton blooms are encouraged. While phytoplankton, through photosynthesis, will raise DO saturation during daylight hours, the dense population of a bloom reduces DO saturation during the night by respiration.

Multiple choice

Dobson units are used to measure the

  1. increase in nutrient concentration in unit volume of a water body

  2. intensity of noise source

  3. reduction in column ozone

  4. size of toxins accumulated in living organisms
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The Dobson unit (DU) is a unit of measurement of the columnar density of a trace gas in the Earth's atmosphere. It originated and continues to be widely used as a measure of total-column ozone, which is dominated by ozone in the stratospheric ozone layer.

Multiple choice

DDT spraying in ponds is harmful because it

  1. increases the pH of water

  2. reduces the oxygen content in water

  3. stabilizes CO2 in water

  4. gets accumulated along the food chain
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

DDT spraying in ponds is harmful because it gets accumulated along the food chain.

Multiple choice

Which of the following statements is NOT correct for algae?

  1. They are usually green in colour.

  2. They are chlorophyll containing microorganisms.

  3. They are autotrophs.

  4. They transport water through xylem vessels.

  5. Excessive growth of algae in a water body leads to eutrophication.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

 Algae are simple microorganisms which do not possess complex tissues like xylem or phloem.

Multiple choice

What is water trickling?

Water pollution can be defined as an undesirable change in the physical, chemical and biological characteristics of water that will be harmful to humans, animals or plant life and productivity. It is customary to consider the treatment of polluted water in three phases- Primary treatment, Secondary treatment and Tertiary or advanced treatment.

  1. In this method, the waste water is mechanically stirred in a tank in presence of increased oxygen with help of electronic pump.

  2. It is carried out by a biological system where microorganisms decompose organic matter.

  3. In this method, different chemical components like phosphate, nitrogen, ammonia, poly-electrolytes, etc. are removed in treatment plants.

  4. In this process, the waste water is passed over stones or racks of plastic surface.

  5. In this process, waste water is passed through a series of wire-meshes of decreasing size.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Trickling of water does the process of passing waste water over stones or racks of plastic surface by gravity that creates an aerated surface resemble the rapid in the natural stream. In presence of oxygen, bacteria degrade organic matter and role of detritus feeding invertebrates in such microbial digestive system is a great importance.

Multiple choice

Which of the following actually brings about the change in pH of water?

The water pollutants are as follows:
1. Suspended impurities like sand, mud, clay and organic matter.
2. Dissolve gasses like CO2, NH3, N2, H2S. 
3. Dissolve minerals like Ca2+, Na+ and Mg2+ salts. 
4. Dissolved chemicals, pesticides, domestic wastes, etc.
5. Micro-organisms of pathogenic or non-pathogenic nature like bacteria, virus, protozoa, etc.
6. Isotopes or radiologically activated substances.

  1. Landslide and earthquake

  2. Volcanic eruption, dead and decay in organic matter

  3. Decay in plants and animals in swamp deep ponds or lakes

  4. Domestic sewage

  5. Mining activities
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Volcanic eruption, dead and decay in organic matter causes changes of pH in water and may be acidic. Presence of dissolved gasses beyond their normal concentration affect physical characteristics of water and is harmful for aquatic life.

Multiple choice

Which of the following is the best example of environmental remediation?

  1. A species of trout becomes extinct in an eutrophic lake.

  2. The annual volume of sewage flowing into a stream is decreased by one half.

  3. The height of a factory smokestack is increased.

  4. PCB-consuming bacteria are sprayed on an area that has soil contaminated with PCBs.
Reveal answer Fill a bubble to check yourself
D Correct answer
Explanation

Generally, remediation means providing a remedy, so environmental remediation deals with the removal of pollution or contaminants from environmental media, such as soil, groundwater, sediment, or surface water for the general protection of human health and the environment or from a brownfield site intended for redevelopment. 

Multiple choice

An increase in the concentration of a substance that occurs in a food chain is called

  1. bioaccumulation

  2. biomagnification

  3. bioconcentration

  4. eutrophication
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Biomagnification, also known as bioamplification or biological magnification, is the increase in concentration of a substance that occurs in a food chain. It occurs as a consequence of: • Persistence (can't be broken down by environmental processes) • Food chain energetics • Low (or nonexistent) rate of internal degradation/excretion of the substance (often due to water-insolubility)

Multiple choice

What is indicated by the high presence of coliform count in water?

  1. Decreased BOD.

  2. Sulphur contamination.

  3. Contamination by human wastes.

  4. Lead contamination.

  5. Hydrocarbon contamination.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

The presence of fecal coliform bacteria in aquatic environments indicates that the water has been contaminated with the fecal material of man or other animals.

Multiple choice

In the water bodies, due to eutrophication _______________.

  1. biological oxygen demand (BOD) increases

  2. water becomes less harmful

  3. biological oxygen demand (BOD) decreases

  4. algae are destroyed

  5. biological oxygen demand (BOD) remains constant
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Due to eutrophication the BOD (biological oxygen demand) increases.

Multiple choice

Which phenomena cause algal bloom?

  1. Salinization

  2. Eutrophication

  3. Biomagnification

  4. Global warming

  5. Ozone depletion
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Eutrophication is characterized by excessive plant and algal growth due to the increased availability of one or more limiting growth factors needed for photosynthesis such as sunlight, carbon dioxide and nutrient fertilizers. This can be a problem in marine habitats such as lakes, as it can cause algal blooms.