Environmental Science MCQ Quiz - Objective Question with Answer for Environmental Science - Download Free PDF

The correct answer is 'It does not measure the oxygen-consuming potential of dissolved organic compounds such as acetate.'

Key Points

• Chemical Oxygen Demand (COD):
  • Chemical Oxygen Demand (COD) is a measure of the total amount of oxygen required to chemically oxidize organic and inorganic matter in water.
  • It is a vital parameter for assessing water quality, especially in wastewater treatment, as it helps determine the pollution load in water.
  • COD is widely used because it provides a quick and approximate measure of the organic pollution in water compared to other tests like Biochemical Oxygen Demand (BOD).
• Limitation of COD:
  • While COD can measure the oxygen-consuming potential of a wide range of organic compounds, it does not effectively measure certain dissolved organic compounds, such as acetate.
  • This limitation arises because some simpler organic compounds may not be completely oxidized during the COD test, leading to an underestimation of the oxygen demand.
  • Thus, the COD test may not provide a comprehensive representation of all oxygen-demanding substances in the sample.

Additional Information

• Why the other options are incorrect:
  • It does not measure the oxygen-consuming potential of organic compounds:
    • This statement is incorrect because COD is specifically designed to measure the oxygen-consuming potential of organic compounds in water. It is a widely used parameter for quantifying the organic load in wastewater and other water samples.
  • It measures only inorganic nutrients:
    • This is incorrect because COD measures the oxygen demand caused by both organic and inorganic substances. However, its primary focus is on organic matter present in the water.
  • It is not suitable for industrial wastewater analysis:
    • This statement is incorrect because COD is extensively used in industrial wastewater analysis. It is a standard test for evaluating the pollution level and treatment needs of industrial effluents.
• Importance of COD in Water Quality Testing:
  • COD is faster and less time-intensive compared to BOD testing, making it a preferred choice for rapid assessments.
  • It is widely used in the design and monitoring of wastewater treatment plants.
  • However, since COD does not distinguish between biodegradable and non-biodegradable organic matter, it is often used in conjunction with other tests like BOD for a more comprehensive analysis.

The correct answer is 'The settling of particles that clump together to form larger aggregates'

Key Points

• Flocculent Settling:
  • Flocculent settling refers to the process where fine particles in suspension come together (or "flocculate") to form larger, heavier aggregates known as flocs.
  • Once these flocs are formed, they settle more easily under the influence of gravity compared to individual particles.
  • This phenomenon occurs due to physical and chemical interactions between particles, including van der Waals forces and the presence of coagulants or flocculants in water.
  • Flocculent settling is commonly observed in water treatment processes, where chemicals are added to promote flocculation and enhance the removal of suspended solids.
  • This process is vital for achieving clarity in water and wastewater treatment and is a key step in sedimentation tanks.

Additional Information

• Explanation of Incorrect Options:
  • The ability of small particles to settle quickly under gravity:
    • This describes discrete particle settling, where individual particles settle independently without any interaction with other particles.
    • Unlike flocculent settling, this process does not involve the formation of aggregates or flocs.
    • Discrete particle settling typically occurs in systems with non-cohesive particles or low concentrations of suspended solids.
  • The ability of particles to remain suspended in water without settling:
    • This describes suspension or colloidal stability, where particles remain dispersed in a liquid and resist settling due to their small size and forces like Brownian motion or electrostatic repulsion.
    • Flocculent settling is the opposite of this phenomenon, as it involves particles aggregating and settling.
  • The settling of solid particles in a concentrated layer at the bottom of a container:
    • This describes compression settling, where settled particles form a dense layer at the bottom due to compaction under their own weight.
    • Compression settling is typically observed in high-concentration sludges or sediments, not in the flocculation process.
• Significance of Flocculent Settling:
  • Flocculent settling is important in water treatment for removing turbidity, organic matter, and other suspended impurities efficiently.
  • It is also used in industrial processes, including mining and food production, to separate solids from liquids.
  • Proper control of flocculation conditions, such as pH, chemical dosage, and mixing, is critical for optimizing this process.

The correct answer is 'Viscous settling'

Key Points

• Viscous settling:
  • Viscous settling is not recognized as a type of settling process in wastewater treatment. The settling processes in wastewater treatment are primarily categorized based on the behavior and characteristics of particles during sedimentation.
  • Viscosity does play a role in fluid dynamics and may influence the settling rate of particles, but it is not defined as a specific settling type within wastewater treatment processes.
  • The standard settling processes include discrete, flocculent, compression, and hindered settling, which are differentiated based on particle interactions and sedimentation conditions.

Additional Information

• Discrete settling:
  • Occurs when individual particles settle independently without significant interaction with other particles.
  • This type of settling is observed in dilute suspensions where particles do not form aggregates.
  • It is commonly applied in primary treatment processes where larger particles or grit settle out.
• Flocculent settling:
  • Involves the aggregation of particles into flocs due to chemical or biological interactions.
  • As flocs grow larger, their settling rate increases compared to individual particles.
  • This type of settling is typical in secondary treatment processes, such as activated sludge systems, where floc formation enhances sedimentation.
• Compression settling:
  • Occurs when particles settle under the weight of a dense layer of sludge at the bottom of the tank.
  • This process is observed in thickened sludge layers where particles are compacted under pressure.
  • Compression settling is important in sludge management and dewatering processes.
• Hindered settling:
  • Hindered settling happens when particles settle in close proximity, and their movement is restricted due to interference from neighboring particles.
  • It occurs in suspensions with higher concentrations of solids, often observed in secondary clarifiers.
  • The collective behavior of particles in hindered settling results in slower sedimentation rates compared to discrete settling.

The correct answer is 'To remove suspended solids using gravity'

Key Points

• Primary Purpose of Sedimentation:
  • Sedimentation is a physical process used in wastewater treatment to remove suspended solids from water through the action of gravity.
  • It involves allowing the wastewater to sit in a sedimentation tank or basin, where heavier particles settle at the bottom as sludge, leaving the water clearer.
  • This process is an essential step in both primary and secondary treatment stages, helping reduce the load on subsequent treatment processes.
  • Sedimentation improves the overall quality of wastewater by removing insoluble impurities, making it easier to treat chemically or biologically in later stages.

Additional Information

• Why Other Options Are Incorrect:
  • To increase the oxygen demand in water:
    • This is incorrect because increasing oxygen demand is not a goal of wastewater treatment; rather, the process aims to reduce oxygen demand to prevent depletion of oxygen in natural water bodies.
    • High oxygen demand, measured as Biological Oxygen Demand (BOD) or Chemical Oxygen Demand (COD), indicates pollution and is reduced through treatment processes like aeration or biological degradation.
  • To disinfect wastewater:
    • Disinfection is a separate process that usually occurs after sedimentation, often involving the use of chlorine, UV radiation, or ozone to kill harmful microorganisms.
    • Sedimentation primarily targets the removal of suspended solids, not pathogens or bacteria.
  • To increase the chemical oxygen demand of the wastewater:
    • This is incorrect as the treatment processes aim to decrease the chemical oxygen demand (COD), which represents the amount of organic pollutants in the water.
    • Sedimentation indirectly helps reduce COD by removing particulate organic matter that could otherwise contribute to higher COD levels.

• Additional Role of Sedimentation in Wastewater Treatment:
  • Sedimentation also aids in the removal of grit, sand, and other heavy particles that could damage equipment in later treatment stages.
  • The sludge collected at the bottom of sedimentation tanks is further processed through digestion or dewatering to minimize environmental impact.
  • While sedimentation is effective for larger particles, finer particles or dissolved impurities require additional processes like filtration or coagulation.

The correct answer is 'COD measures the oxygen-consuming potential of both organic and inorganic compounds, while BOD specifically measures organic matter.'

Key Points

• Chemical Oxygen Demand (COD):
  • COD is a measure of the total oxygen required to oxidize all organic and inorganic compounds in a water sample.
  • It provides a quick estimate of the pollution level in water, including both biodegradable and non-biodegradable substances.
  • The test involves using a strong oxidizing agent (e.g., potassium dichromate) to break down substances in a controlled environment, and the amount of oxygen consumed is recorded.
• Biochemical Oxygen Demand (BOD):
  • BOD measures the amount of oxygen required by microorganisms to decompose organic matter in water under aerobic conditions over a specific period (usually 5 days at 20°C).
  • It indicates the level of biodegradable organic pollution in a water sample.
  • BOD is a slower process compared to COD, as it depends on microbial activity for the breakdown of organic matter.
• Key difference: COD includes the oxygen demand of both organic and inorganic substances, while BOD focuses only on the oxygen demand from biodegradable organic matter.

The correct answer is tidal.Key Points

• Tidal energy is the correct answer for utilising in the Gulf of Khambhat, the Gulf of Kutch and Sundarbans region in India.
• Tidal energy is generated by the gravitational forces of the moon and the sun on the earth's water bodies.
• The Gulf of Khambhat and the Gulf of Kutch are known for their strong tidal currents, making them ideal locations for tidal energy projects.
• The Sundarbans region, located in the delta of the Ganges, Brahmaputra and Meghna rivers, has a vast network of tidal creeks and channels which can be used to generate tidal energy.

Additional Information

• The most advanced and developed renewable energy source is wind energy.
  • By harnessing the kinetic energy created by air currents, it uses wind to create electricity. 
• The energy present in a system that determines its temperature is referred to as thermal energy.
  • Thermal energy flows as heat.
• Any energy produced by the sun is referred to as solar energy.
  • Nuclear fusion occurs in the sun and produces solar energy.

The correct answer is Sun.Key Points

• The ultimate source of energy for all living organisms is the sun.
• The sun provides energy to plants through the process of photosynthesis.
• Animals then consume plants (or other animals that have consumed plants) to obtain energy.
• This energy is then used for various processes such as growth, reproduction, and movement.
• Without the sun, life on Earth would not be possible.​

Additional Information

• Soil: While soil does provide nutrients and water to plants, it is not the ultimate source of energy for living organisms.
• Water: Water is essential for life, but it is not a direct source of energy.
• Air: While oxygen is required for respiration, it is not the ultimate source of energy.

The correct answer is Methane.

Key Points

• Biogas is primarily composed of methane gas, which is the major component of biogas.
• Methane gas makes up about 50-75% of biogas, while the remaining 25-50% is made up of carbon dioxide, water vapor, and trace amounts of other gases.
• Biogas is a gaseous renewable energy source.
• Anaerobic digestion using methanogens or anaerobic organisms in a bioreactor, biodigester, or anaerobic digester produces biogas.
• The main components of the gas are methane (CH₄) and carbon dioxide (CO₂), with trace amounts of moisture, siloxanes, and hydrogen sulfide (H₂S).

Additional Information

• Compressed natural gas:
  • CNG is a fossil fuel that is primarily composed of methane gas.
  • CNG is commonly used as a fuel for vehicles and is produced from natural gas reserves.
• Hydrogen gas:
  • It is a colorless, odorless, tasteless, and highly flammable gas.
  • It is commonly used in fuel cells to generate electricity.
• Liquefied petroleum gas:
  • It is a mixture of propane and butane gases.
  • It is commonly used as a fuel for heating and cooking.

The correct answer is Leadership in Energy and Environment Design.  

 Key Points

• LEED (Leadership in Energy and Environmental Design) is an ecology-oriented building certification program run under the auspices of the U.S. Green Building Council (USGBC).
• LEED concentrates its efforts on improving performance across five key areas of environmental and human health: energy efficiency, indoor environmental quality, materials selection, sustainable site development and water savings.
• LEED has special rating systems that apply to all kinds of structures, including schools, retail and healthcare facilities.
• Rating systems are available for new construction and major renovations as well as existing buildings. 

Therefore, the correct answer is Leadership in Energy and Environment Design.

The correct answer is Our Common Future.

Key Points

• The Brundtland Commission was created by the United Nations to suggest measures to protect the human environment and natural resources and prevent the deterioration of economic and social development.
• It is formally called World Commission on Environment and Development.
• Its report was titled as "Our Common Future".
• It was released in 1987.
• The Brundtland Commission’s characterization of ‘sustainable development’ is the development that meets the needs of the present without compromising the ability of future generations to meet their own needs.

The correct answer is Norman Myers.

Key PointsBiodiversity Hotspots:

• Biodiversity hotspots are regions with high species richness and a high degree of endemism. 
• The British biologist Norman Myers coined the term “biodiversity hotspot” in 1988 as a biogeographic region characterized both by exceptional levels of plant endemism and by serious levels of habitat loss.
• Conservation International (CI) adopted Myers’ hotspots and in 1996, the organization made the decision to undertake a reassessment of the hotspots concept. 
• In 1999, CI identified 25 biodiversity hotspots in the book “Hotspots: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions”.
• In 2005 CI published an updated titled “Hotspots Revisited: Earth’s Biologically Richest and Most Endangered Terrestrial Ecoregions”.
• The 35 biodiversity hotspots cover 2.3% of the Earth’s land surface, yet more than 50% of the world’s plant species and 42% of all terrestrial vertebrate species are endemic to these areas.

Biodiversity hotspots in India:

• Himalaya: Includes the entire Indian Himalayan region (and that falls in Pakistan, Tibet, Nepal, Bhutan, China, and Myanmar).
• Indo-Burma: Includes entire North-eastern India, except Assam and Andaman group of Islands (and Myanmar, Thailand, Vietnam, Laos, Cambodia, and southern China).
• Western Ghats and Sri Lanka: Includes the entire Western Ghats (and Sri Lanka).
• Sundalands: Includes the Nicobar group of Islands, Indonesia, Malaysia, Singapore, Brunei, and Philippines.

The correct answer is apex.Key Points

• The ecological pyramid is a graphical representation of the flow of energy and matter in an ecosystem, with different trophic levels arranged in a pyramid shape.
• The base of the ecological pyramid represents the primary producers, such as plants, which convert sunlight into organic matter through photosynthesis.
• As we move up the pyramid, each level represents organisms that consume the lower level, such as herbivores, carnivores, and top predators.
• Therefore, the base of the ecological pyramid is usually broad, as it supports a large number of organisms at the primary level, and it narrows towards the apex, which represents the top predator or the highest trophic level.
• Option 3, "apex," is the correct answer, as it correctly describes the narrowing of the ecological pyramid towards the top predator or the highest trophic level.

Additional Information

• Option 1, "bottom," is incorrect, as it refers to the base of the pyramid, which is broad and supports a large number of organisms.
• Option 2, "center," is incorrect, as there is no central point in the ecological pyramid, and the trophic levels are arranged in a hierarchical order.
• Option 4, "sides," is incorrect, as it does not describe the shape or structure of the ecological pyramid, which is a pyramid shape with a broad base and a narrow apex.
• The ecological pyramid is an important tool for understanding the flow of energy and matter in an ecosystem and the interdependence of different species.
• It helps us to understand the impact of human activities on the environment and the need for conservation and sustainable use of natural resources.

Concept-

Different factors such as distance from the shore, penetration of light, depth of water, plant and animal species, etc. determine the following zones found in the pond ecosystem:

• Littoral zone: It is the zone closer to the shore. It contains shallow water and allows easy penetration of light. Rooted plant species occupy it. Animal species include reeds, crawfish, snails, insects, etc.
• Limnetic zone: The limnetic zone refers to the open water of the pond with an effective penetration of light. This zone is dominated by phytoplankton. Animal species mainly include small fishes and insects.
• Profundal zone: The region of a pond below the limnetic zone is called a profound zone with no effective light penetration. Some amphibians and small turtles occupy it.
• Benthic zone: The bottom zone of a pond is benthic and is occupied by a community of decomposers. The decomposers are called benthos.

The correct answer is Montreal Protocol.

 Key Points

Montreal Protocol:

• The Montreal Protocol on Substances that Deplete the Ozone Layer (the Montreal Protocol) is an international agreement made in 1987.
• It was proposed to control the emission of ozone-depleting gases like CFCs and other ozone-depleting chemicals.  
• The Montreal Protocol is signed by 197 countries.
• It is the first treaty in the history of the United Nations to achieve universal ratification.
• It is considered by many the most successful environmental global action.
• It sits under the Vienna Convention for the Protection of the Ozone Layer (the Vienna Convention).
• It was designed to stop the production and import of ozone-depleting substances and reduce their concentration.
• It targets 96 ozone-depleting chemicals in thousands of applications across more than 240 industrial sectors.

Thus, Montreal protocol aims to phase out hydrofluorocarbons.

Additional Information

Explanation:

Chromatography Techniques: 

• It is the biophysical technique that is used to separate, identify and purify the components of a mixture for both qualitative and quantitative analysis.
• This method involves the analyte that combines within a liquid or gaseous mobile phase pumped through the stationary phase. 

Gel filtration chromatography:

• It separates the proteins based on molecular size or weight differences.
• The microporous packing material made of gel is used to separate the molecules pumped through it where the small-sized molecules access the interior of the pores partly or wholly. 

Ion exchange chromatography:

• It separates the molecules based on their affinity to ion exchangers between the target ions present in the sample solution. Two types include cationic and anionic exchangers can be used.

Thin layer chromatography:

• The liquid mobile phase is run through the flat surface of the finely divided solid/liquid stationary phase to separate the individual components in the mixture.
• This technique is mostly used for non-volatile or low-volatility compounds.

Adsorption/Column chromatography:

• The separation is done through the solid stationary phase (Silica gel or Alumina) and the liquid mobile phase single or mixture solvent.
• The separation is mainly due to the adsorption force that existed to hold the molecules based on the interaction with the adsorbate at different rates.

Hence, option 4 is the correct answer.