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 general knowledge

What minerals are found in the run-off from agricultural land and treated and untreated sewage effluents, which are highly responsible for eutrophication of water bodies?

  1. Phosphorous and carbon

  2. Nitrogen and phosphorus

  3. Potassium and arsenic

  4. Iron and manganese
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

Eutrophication is the excessive enrichment of water bodies with nutrients, leading to algal blooms and oxygen depletion. The primary nutrients responsible are nitrogen and phosphorus, which enter waterways through agricultural runoff (fertilizers) and sewage effluents. While carbon is not typically a limiting factor for eutrophication, potassium, arsenic, iron, and manganese are not the key drivers of this process.

Multiple choice general knowledge

Aquaculture is the controlled cultivation and harvesting of freshwater or marine aquatic species of plants and animals. Name an area along the Indian coast, where aquaculture and prawn culture activities are a major source of coastal pollution as well as a threat to the endangered sea turtles.

  1. East Coast, especially Orissa

  2. Maharashtra

  3. Kerala

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

Orissa (now Odisha) on the East Coast of India is globally recognized as a major nesting site for endangered olive ridley sea turtles. The region's coastline hosts mass nesting sites called arribadas. However, extensive aquaculture and prawn farming activities have destroyed mangrove habitats and created coastal pollution that threatens these turtles and their nesting grounds. Maharashtra and Kerala have aquaculture but are not the primary turtle nesting areas.

Multiple choice general knowledge

Of the following indications of the health of a water body, which is the most widely accepted means of measuring how polluting an effuent is?

  1. COD (chemical oxygen demand)

  2. BOD (biological oxygen demand)

  3. Chloroform content

  4. non of the above
Reveal answer Fill a bubble to check yourself
B Correct answer
Explanation

BOD (Biological Oxygen Demand) is the most widely accepted indicator of water pollution because it measures the amount of oxygen required by microorganisms to decompose organic matter in water. High BOD indicates severe organic pollution that can deplete dissolved oxygen and harm aquatic life. COD measures chemical oxidization but is less representative of natural conditions. Chloroform content is not a standard pollution indicator.

Multiple choice general knowledge

A healthy freshwater fish is placed in saltwater. The expected consequence of this would be that

  1. the fish becomes dehydrated and dies

  2. the fish becomes bloated and dies

  3. the fish suffers from fungal or bacterial disease and dies

  4. ther is no observable effect on the fish provided there is sufficient food
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Freshwater fish are hypotonic to their environment, meaning their body fluids have lower salt concentration than the surrounding water. In saltwater, water rapidly leaves their cells through osmosis to balance salt concentrations, causing severe dehydration and death. The fish does not become bloated - that would happen if a saltwater fish were placed in freshwater.

Multiple choice general knowledge

What is "Cycling" in aquarium terms?

  1. Growth of bacterial in the intial few weeks after aquarium setup

  2. Periodically cleaning the aquarium

  3. Changing the fish often

  4. Changing the water often
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Option A is correct. In aquarium terminology, 'cycling' refers to establishing the nitrogen cycle - the growth of beneficial bacteria (nitrosomonas and nitrobacter) in the filter during the initial weeks after setup. These bacteria convert toxic ammonia to nitrite and then to less harmful nitrate.

Multiple choice general knowledge

Eutrophication of water bodies resulting to killing of fishes is mainly due to

  1. Non-availability of food

  2. Non-availability of light

  3. Non-availability of oxygen

  4. Non-availability of essential minerals
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Eutrophication is caused by excess nutrients (nitrogen, phosphorus) entering water bodies, leading to algal blooms. When algae die and decompose, oxygen is consumed, creating hypoxic or anoxic conditions. Fish die from oxygen deprivation, not from lack of food, light, or minerals.

Multiple choice general knowledge

When neighborhood residents noticed a large number of dead fish in a local creek, they traced the problem to a nearby gas station. It turned out that a tank of antifreeze had developed a leak. This is an example of..

  1. Point pollution

  2. Nonpoint pollution

  3. Thermal pollution

  4. Ground water pollution
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

The antifreeze leak from the gas station's storage tank is point source pollution because it originates from a single, identifiable location. Point sources have specific discharge points like pipes, tanks, or ditches, making them traceable to their origin and easier to regulate than diffuse pollution sources.

Multiple choice general knowledge

Some communities banned detergents containing high levels of phosphates because...

  1. phosphates cause chemical reactions that raise the temperature of river and lake water, disrupting ecosystems.

  2. phosphates are not efficient cleansers.

  3. excessive phosphates in lakes may begin a process that causes fish to suffocate and die.

  4. phosphates kill algae and disrupt normal food webs in lakes.
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Phosphates act as fertilizers in water bodies, causing excessive algae growth (eutrophication). When algae die and decompose, bacteria consume oxygen during decomposition, depleting dissolved oxygen levels. This oxygen depletion causes fish to suffocate and die, not the phosphates directly killing algae.

Multiple choice general knowledge

What SPECIFC effect of eutraphication causes large numbers of fish to be killed?

  1. Increased levels of phospates

  2. Increased amounts of bacteria

  3. Decreased levels of dissolved oxygen

  4. Increased amounts of algae
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Eutrophication causes excessive algal growth. When these algae die and decompose, bacteria consume large amounts of dissolved oxygen. This oxygen depletion creates hypoxic conditions that suffocate fish, causing large-scale fish kills. While algae blooms and bacterial increases are part of the process, the direct killer is oxygen depletion.

Multiple choice

Which of the following statements is/are false?

a. Foul-smelling gases are given off due to the decomposition of waste organic matter present in sewage by anaerobic bacteria. b. Open drains are breeding places for mosquitoes and flies that cause diseases. c. Aquatic animals die due to lack of hydrogen that is used by microorganisms decomposing the organic matter.

  1. Only a

  2. Both a and b

  3. Only b

  4. Both b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
E Correct answer
Explanation

This is the correct option as this statement is false. Aquatic animals die due to lack of oxygen that is used by microorganisms decomposing the organic matter.

Multiple choice

Which of the following statements is/are false?

a. Discharge of treated sewer in the water bodies is the main cause of water pollution. b. In sedimentation tanks, the floating materials like oil and grease are removed by a skimmer. c. The water obtained after scraping and skimming is called clarified water.

  1. Only a

  2. Both a and b

  3. Only b

  4. Both b and c

  5. Only c
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

This is the correct option as this statement is false. Discharge of untreated sewer in the water bodies is the main cause of water pollution.

Multiple choice

Why are eucalyptus trees planted around a sewage pond?

(a) They absorb the surplus waste water. (b) They neutralise the foul smell. (c) They hide the dirty pond. (d) They release good amount of pure water vapour.

  1. Only (a) and (d)

  2. Only (b) and (c)

  3. Only (a) and (b)

  4. Only (c) and (d)

  5. All of these
Reveal answer Fill a bubble to check yourself
A Correct answer
Explanation

Yes, it is correct, as eucalyptus trees absorb the surplus waste water very quickly. They also release pure water vapour into the atmosphere.

Multiple choice

____________ act as natural cleaning agents in the water bodies.

  1. Algae

  2. Viruses and yeast

  3. Aerobic bacteria

  4. Insects and flies
Reveal answer Fill a bubble to check yourself
C Correct answer
Explanation

Aerobic bacteria act as natural cleaning agents in water bodies by consuming organic pollutants and breaking them down into simpler, less harmful compounds. They require oxygen to function and are essential for maintaining water quality in natural ecosystems and wastewater treatment systems.