Q.1 What is the primary purpose of a landfill liner in solid waste management?
To increase the capacity of the landfill
To prevent leachate from contaminating groundwater
To accelerate waste decomposition
To attract waste-eating insects
Explanation - A liner, typically made of clay or synthetic material, acts as a barrier that stops leachate – liquid that has percolated through waste – from reaching the underlying soil and groundwater.
Correct answer is: To prevent leachate from contaminating groundwater
Q.2 Which microorganism is commonly used for the bioremediation of oil‑spilled soils?
Pseudomonas aeruginosa
Escherichia coli
Bacillus subtilis
Streptococcus pneumoniae
Explanation - Pseudomonas species have enzymes capable of degrading hydrocarbons, making them effective agents for cleaning up petroleum contamination.
Correct answer is: Pseudomonas aeruginosa
Q.3 In the context of solid waste, what does the term “biodegradable” refer to?
Materials that can be burned for energy
Materials that decompose naturally by microorganisms
Materials that are recyclable
Materials that are inert and never change
Explanation - Biodegradable waste is broken down by bacteria, fungi, or other organisms into simpler compounds such as CO₂, water, and biomass.
Correct answer is: Materials that decompose naturally by microorganisms
Q.4 Which of the following is a common indicator of successful composting?
High temperature (>70 °C) for at least 3 days
Presence of foul odor
Visible large pieces of plastic
Moisture content above 80 %
Explanation - Thermophilic temperatures ensure rapid microbial activity and kill most pathogens and weed seeds, indicating effective composting.
Correct answer is: High temperature (>70 °C) for at least 3 days
Q.5 What type of waste is classified as “hazardous”?
Glass bottles
Food scraps
Lead‑based batteries
Paper cartons
Explanation - Hazardous waste contains substances that are toxic, flammable, corrosive, or reactive, such as heavy metals found in lead‑acid batteries.
Correct answer is: Lead‑based batteries
Q.6 Which process converts organic solid waste into biogas?
Incineration
Anaerobic digestion
Mechanical shredding
Landfilling
Explanation - Anaerobic digestion breaks down organic material in the absence of oxygen, producing methane‑rich biogas that can be used for energy.
Correct answer is: Anaerobic digestion
Q.7 In electrical engineering, which parameter is most directly affected by the moisture content of soil used as an insulating medium?
Capacitance
Resistance
Inductance
Magnetic permeability
Explanation - Higher moisture lowers the resistivity of soil, thereby decreasing its resistance and potentially increasing leakage currents.
Correct answer is: Resistance
Q.8 Which of the following metals is most likely to be removed from wastewater by biosorption using dead fungal biomass?
Sodium (Na⁺)
Calcium (Ca²⁺)
Copper (Cu²⁺)
Nitrogen (N₂)
Explanation - Fungal cell walls have functional groups (e.g., carboxyl, hydroxyl) that bind heavy metals like copper efficiently.
Correct answer is: Copper (Cu²⁺)
Q.9 What does the term “leachate” describe in a landfill context?
Gas produced by decomposing waste
Liquid that percolates through waste, carrying dissolved substances
Solid debris left after compaction
Fire‑resistant coating applied to landfill surfaces
Explanation - Leachate is the contaminated water that drains from a landfill and can contain organic and inorganic pollutants.
Correct answer is: Liquid that percolates through waste, carrying dissolved substances
Q.10 Which of the following is a primary advantage of using bio‑remediation over chemical treatment for soil contamination?
Instant removal of pollutants
Lower cost and minimal secondary pollution
Requires no monitoring
Works only on metallic contaminants
Explanation - Bioremediation utilizes natural processes, often costing less and generating fewer harmful by‑products compared with aggressive chemical methods.
Correct answer is: Lower cost and minimal secondary pollution
Q.11 In a typical municipal solid waste (MSW) management hierarchy, which option ranks highest in terms of waste minimization?
Incineration
Landfilling
Recycling
Source reduction
Explanation - Source reduction (or waste prevention) addresses waste at its origin, eliminating the need for downstream handling.
Correct answer is: Source reduction
Q.12 Which electrical parameter would you monitor to assess the performance of a microbial fuel cell used for waste treatment?
Voltage output
Capacitive reactance
Magnetic flux density
Insulation resistance
Explanation - Microbial fuel cells generate electrical energy from microbial metabolism, and voltage (or power) is a direct measure of their performance.
Correct answer is: Voltage output
Q.13 What is the main environmental concern associated with open burning of solid waste?
Generation of renewable energy
Emission of toxic gases like dioxins and furans
Increase in soil fertility
Reduction of landfill space
Explanation - Open burning releases hazardous pollutants, including dioxins, furans, and particulate matter, which pose serious health risks.
Correct answer is: Emission of toxic gases like dioxins and furans
Q.14 Which of the following is NOT a typical component of a leachate treatment system?
Aerated lagoon
Reverse osmosis membrane
Biological treatment tank
Magnetic separator
Explanation - Magnetic separators are used for ferrous material removal, not for treating dissolved contaminants in leachate.
Correct answer is: Magnetic separator
Q.15 In the context of solid waste, the term “organic fraction” refers to:
Plastics and synthetic polymers
Metals and alloys
Biodegradable materials like food and yard waste
Glass and ceramics
Explanation - The organic fraction includes all waste that can be biologically decomposed, such as food scraps, paper, and garden residues.
Correct answer is: Biodegradable materials like food and yard waste
Q.16 Which bioremediation technique involves the use of plant roots to stabilize contaminants?
Phytoremediation
Mycoremediation
Bioaugmentation
Vapor extraction
Explanation - Phytoremediation uses plants to absorb, accumulate, or detoxify pollutants in soil and water.
Correct answer is: Phytoremediation
Q.17 What is the primary function of a gas collection system in a sanitary landfill?
To capture methane for energy recovery
To increase landfill temperature
To prevent rainwater infiltration
To compact waste more tightly
Explanation - Collected landfill gas, mainly methane, can be flared or used in generators to produce electricity, reducing greenhouse gas emissions.
Correct answer is: To capture methane for energy recovery
Q.18 Which of the following heavy metals is most readily immobilized by adding lime to contaminated soil?
Mercury (Hg)
Arsenic (As)
Lead (Pb)
Cadmium (Cd)
Explanation - Lime raises pH, causing lead to precipitate as lead hydroxide or carbonate, reducing its bioavailability.
Correct answer is: Lead (Pb)
Q.19 In an anaerobic digester, the primary microbial group responsible for converting volatile fatty acids to methane is:
Acidogenic bacteria
Methanogenic archaea
Aerobic fungi
Nitrifying bacteria
Explanation - Methanogens convert acetate and hydrogen/carbon dioxide into methane, the final step in anaerobic digestion.
Correct answer is: Methanogenic archaea
Q.20 Which of the following best describes the term “bioreactor” in waste treatment?
A device that burns waste at high temperature
A closed system that facilitates controlled biological degradation of waste
A machine that sorts recyclables mechanically
A container for storing hazardous chemicals
Explanation - Bioreactors provide optimal conditions (temperature, pH, nutrients) for microbes to degrade waste efficiently.
Correct answer is: A closed system that facilitates controlled biological degradation of waste
Q.21 What is the main advantage of using a dual‑layer (clay‑geosynthetic) landfill liner over a single‑layer liner?
It reduces construction cost
It provides redundancy, decreasing the risk of leachate leakage
It increases the landfill’s capacity
It eliminates the need for leachate collection
Explanation - A dual‑layer system ensures that if one layer fails, the second layer still protects groundwater.
Correct answer is: It provides redundancy, decreasing the risk of leachate leakage
Q.22 Which parameter is most important for assessing the aerobic composting process?
pH level
Carbon to nitrogen (C/N) ratio
Electrical conductivity
Magnetic susceptibility
Explanation - An optimal C/N ratio (around 25‑30:1) ensures balanced microbial activity and efficient decomposition.
Correct answer is: Carbon to nitrogen (C/N) ratio
Q.23 Which type of solid waste is most suitable for conversion to bio‑ethanol?
Paper and cardboard
Food waste rich in sugars and starches
Metal scrap
Glass bottles
Explanation - Fermentable carbohydrates in food waste can be converted to ethanol by yeast or bacterial fermentation.
Correct answer is: Food waste rich in sugars and starches
Q.24 What does the term “bioavailability” refer to in environmental biotechnology?
The amount of biomass that can be harvested
The extent to which a contaminant is accessible to organisms for uptake
The speed of microbial growth in a bioreactor
The number of species present in a sample
Explanation - Bioavailability determines how easily a pollutant can be absorbed, metabolized, or transformed by living organisms.
Correct answer is: The extent to which a contaminant is accessible to organisms for uptake
Q.25 Which of the following is a common indicator of landfill gas composition?
Methane concentration around 50‑60 %
Oxygen concentration above 20 %
High levels of carbon monoxide
Absence of carbon dioxide
Explanation - Typical landfill gas contains 50‑60 % methane, 40‑50 % carbon dioxide, and trace amounts of other gases.
Correct answer is: Methane concentration around 50‑60 %
Q.26 In solid waste management, the term “WEEE” stands for:
Waste Electrical and Electronic Equipment
Water, Energy, and Emission Estimation
Wood, Earth, and Eco-friendly Elements
Waste Energy Extraction Engine
Explanation - WEEE refers to discarded electronic devices, which require special handling due to hazardous components.
Correct answer is: Waste Electrical and Electronic Equipment
Q.27 Which factor most strongly influences the rate of biodegradation in a landfill?
Depth of waste
Moisture content
Color of waste
Time of day
Explanation - Adequate moisture is essential for microbial activity; too little or too much can inhibit degradation.
Correct answer is: Moisture content
Q.28 What is the purpose of a “capping” layer on a closed landfill?
To provide a surface for recreational use
To prevent water infiltration and limit gas emission
To increase the waste volume
To enhance microbial activity
Explanation - Capping seals the landfill, reducing leachate formation and controlling the release of gases.
Correct answer is: To prevent water infiltration and limit gas emission
Q.29 Which of the following processes is used to remove heavy metals from contaminated soil by converting them into less soluble forms?
Phytostabilization
Thermal desorption
Incineration
Aerobic composting
Explanation - Plants immobilize metals in the root zone, reducing their mobility and bioavailability.
Correct answer is: Phytostabilization
Q.30 In a bioremediation project, what does the term “bioaugmentation” refer to?
Adding nutrients to stimulate indigenous microbes
Increasing temperature to speed up reactions
Introducing specialized microorganisms to enhance degradation
Removing microbes from the environment
Explanation - Bioaugmentation involves inoculating a site with cultured strains that have the desired degradative capabilities.
Correct answer is: Introducing specialized microorganisms to enhance degradation
Q.31 Which of the following is a common by‑product of the aerobic composting process?
Methane
Hydrogen sulfide
Carbon dioxide
Sulfuric acid
Explanation - Aerobic decomposition releases CO₂ as organic matter is oxidized by oxygen‑using microbes.
Correct answer is: Carbon dioxide
Q.32 What does the term “Zero Waste” aim to achieve?
Eliminate all waste generation through redesign and reuse
Burn all waste in incinerators
Send all waste to landfills
Export waste to other countries
Explanation - Zero Waste focuses on redesigning systems to prevent waste, encouraging reuse, recycling, and composting.
Correct answer is: Eliminate all waste generation through redesign and reuse
Q.33 Which type of sensor would be most useful for monitoring methane levels in a landfill gas collection system?
Photoelectric sensor
Catalytic bead sensor
Infrared (NDIR) sensor
Thermocouple
Explanation - NDIR sensors detect methane based on its characteristic infrared absorption wavelengths, providing accurate measurements.
Correct answer is: Infrared (NDIR) sensor
Q.34 Which of the following is an example of a renewable energy source that can be generated from solid waste?
Solar panels
Biogas from anaerobic digestion
Hydroelectric power
Geothermal energy
Explanation - Organic waste broken down anaerobically produces methane-rich biogas, which can be used for electricity or heat.
Correct answer is: Biogas from anaerobic digestion
Q.35 In the context of electrical safety for waste‑handling equipment, what does the term ‘IP rating’ indicate?
The power output of the device
The level of protection against dust and water ingress
The insulation resistance of the wires
The efficiency of the motor
Explanation - IP (Ingress Protection) rating classifies how well an enclosure guards against solid particles and liquids.
Correct answer is: The level of protection against dust and water ingress
Q.36 Which microbial process is primarily responsible for the breakdown of cellulose in compost?
Nitrification
Methanogenesis
Cellulolysis
Denitrification
Explanation - Cellulolytic microorganisms produce enzymes that hydrolyze cellulose into simpler sugars.
Correct answer is: Cellulolysis
Q.37 What is the typical pH range of mature compost?
2.5 – 3.5
4.0 – 5.0
6.0 – 8.0
9.0 – 10.0
Explanation - Mature compost is usually neutral to slightly alkaline, supporting diverse microbial populations.
Correct answer is: 6.0 – 8.0
Q.38 Which of the following is NOT a typical method for reducing the volume of municipal solid waste?
Mechanical shredding
Incineration
Landfilling
Composting
Explanation - Landfilling stores waste without reducing its volume; the other methods physically or biologically reduce waste size.
Correct answer is: Landfilling
Q.39 In bioremediation, what does the term ‘catabolic pathway’ refer to?
A sequence of reactions that builds complex molecules
A series of reactions that break down pollutants into simpler compounds
The genetic material of microbes
The process of photosynthesis in algae
Explanation - Catabolism involves the degradation of substances, providing energy and reducing contaminant toxicity.
Correct answer is: A series of reactions that break down pollutants into simpler compounds
Q.40 Which of the following is a major greenhouse gas emitted from untreated organic waste in landfills?
Nitrogen (N₂)
Ozone (O₃)
Methane (CH₄)
Sulfur dioxide (SO₂)
Explanation - Anaerobic decomposition of organic matter generates methane, a potent greenhouse gas.
Correct answer is: Methane (CH₄)
Q.41 Which of the following is a key advantage of using an electro‑kinetic remediation method for soil contaminated with heavy metals?
It works only on organic pollutants
It requires high temperatures
It can mobilize metals without excavating soil
It eliminates all contaminants instantly
Explanation - Electro‑kinetic treatment applies an electric field to move charged particles, allowing in‑situ removal of metals.
Correct answer is: It can mobilize metals without excavating soil
Q.42 What is the main function of a “settling pond” in a wastewater treatment plant serving a solid waste processing facility?
To increase the temperature of the water
To allow suspended solids to settle before further treatment
To convert sewage into drinking water
To generate electricity
Explanation - Settling ponds (or clarifiers) provide quiescent conditions where particles can settle out by gravity.
Correct answer is: To allow suspended solids to settle before further treatment
Q.43 Which type of waste is most suitable for treatment by the “thermal desorption” technique?
Organic food waste
Metallic scrap
Contaminated soils with volatile organic compounds (VOCs)
Glass bottles
Explanation - Thermal desorption heats soil to vaporize VOCs, which are then captured, leaving the soil cleaned.
Correct answer is: Contaminated soils with volatile organic compounds (VOCs)
Q.44 In the context of waste‑to‑energy, what does the term “combined heat and power (CHP)” mean?
Generating electricity and usable heat from the same fuel source
Producing only electricity from waste
Generating heat without electricity
Storing waste in underground chambers
Explanation - CHP systems capture both electrical and thermal energy from waste combustion, improving overall efficiency.
Correct answer is: Generating electricity and usable heat from the same fuel source
Q.45 Which of the following is a typical indicator that a landfill is nearing the end of its operational life?
Increasing leachate production
Decreasing gas generation
Stable waste height for several years
All of the above
Explanation - As biodegradable material is exhausted, methane production declines, signaling that the landfill is nearing closure.
Correct answer is: Decreasing gas generation
Q.46 What is the main reason for adding bulking agents (e.g., wood chips) to a compost pile?
To increase the carbon content only
To improve aeration and prevent compaction
To lower the temperature
To add nutrients for plants
Explanation - Bulking agents create pore space, allowing oxygen to penetrate and supporting aerobic microbes.
Correct answer is: To improve aeration and prevent compaction
Q.47 Which of the following best describes the term “bioventing”?
Injecting nutrients into soil to promote plant growth
Using oxygen‑rich air to stimulate aerobic biodegradation of soil contaminants
Removing gases from a landfill by vacuum
Burning waste in a high‑temperature furnace
Explanation - Bioventing supplies air to the subsurface, enhancing aerobic microbial activity that degrades organic pollutants.
Correct answer is: Using oxygen‑rich air to stimulate aerobic biodegradation of soil contaminants
Q.48 Which parameter is most directly related to the electrical conductivity of a leachate sample?
Temperature
Total dissolved solids (TDS)
pH level
Methane concentration
Explanation - Higher concentrations of dissolved ions increase the solution’s ability to conduct electricity.
Correct answer is: Total dissolved solids (TDS)
Q.49 What is the main environmental concern of improper e‑waste disposal?
Release of heavy metals and persistent organic pollutants
Increase in soil fertility
Production of compost
Generation of renewable energy
Explanation - E‑waste contains toxic substances such as lead, mercury, and brominated flame retardants that can leach into the environment.
Correct answer is: Release of heavy metals and persistent organic pollutants
Q.50 Which of the following processes can be used to treat sludge generated from wastewater treatment plants that handle solid waste effluent?
Anaerobic digestion
Mechanical shredding
Incineration
All of the above
Explanation - Sludge can be digested anaerobically for biogas, shredded to reduce volume, or incinerated for energy recovery.
Correct answer is: All of the above
Q.51 In a landfill gas recovery system, what is the purpose of a “flare”?
To increase methane concentration
To combust excess gas safely, converting it to CO₂ and water
To capture methane for electricity generation
To cool the gas
Explanation - Flares burn off surplus landfill gas, reducing the greenhouse impact of unutilized methane.
Correct answer is: To combust excess gas safely, converting it to CO₂ and water
Q.52 Which type of plant is most commonly used in phytoremediation to extract heavy metals from contaminated soils?
Willow (Salix spp.)
Sunflower (Helianthus annuus)
Poplar (Populus spp.)
Alfalfa (Medicago sativa)
Explanation - Sunflowers are hyperaccumulators capable of taking up significant amounts of metals like lead and cadmium.
Correct answer is: Sunflower (Helianthus annuus)
Q.53 What does the term “biological oxygen demand (BOD)” measure in waste water from solid waste treatment?
The amount of oxygen needed to oxidize organic matter over 5 days
The amount of nitrogen present
The pH of the water
The concentration of heavy metals
Explanation - BOD indicates the potential for organic pollution to deplete dissolved oxygen in receiving waters.
Correct answer is: The amount of oxygen needed to oxidize organic matter over 5 days
Q.54 Which of the following is a common use for the ash produced by incinerating municipal solid waste?
As a fertilizer for crops
As a construction aggregate
As a fuel for boilers
As a food additive
Explanation - Incineration ash, after proper treatment, can be incorporated into concrete or road base materials.
Correct answer is: As a construction aggregate
Q.55 Which of the following best describes an “engineered landfill”?
A landfill built on a hill without liners
A landfill equipped with liners, leachate collection, and gas capture systems
A landfill that only accepts inert waste
A landfill that is open to the environment
Explanation - Engineered landfills incorporate multiple engineering controls to protect the environment.
Correct answer is: A landfill equipped with liners, leachate collection, and gas capture systems
Q.56 In the context of solid waste, what does the acronym “MSW” stand for?
Metallic Solid Waste
Municipal Solid Waste
Microbial Soil Water
Mechanical Sludge Waste
Explanation - MSW refers to the everyday waste generated by households, businesses, and institutions in a municipality.
Correct answer is: Municipal Solid Waste
Q.57 Which of the following is the most effective method for reducing the amount of plastic waste entering the environment?
Incineration
Mechanical recycling
Landfilling
Open dumping
Explanation - Recycling plastic reduces the need for virgin material and keeps plastic out of landfills and oceans.
Correct answer is: Mechanical recycling
Q.58 What is the primary purpose of a “bio‑filter” in a waste‑treatment facility?
To filter solid particles from air
To remove odors and volatile organic compounds using microorganisms
To increase temperature of exhaust gases
To convert methane into carbon monoxide
Explanation - Bio‑filters employ microbial films that degrade odorous compounds as gases pass through a porous medium.
Correct answer is: To remove odors and volatile organic compounds using microorganisms
Q.59 Which of the following soil amendments can enhance the microbial degradation of petroleum hydrocarbons?
Sodium chloride
Sodium nitrate
Calcium carbonate
Silica sand
Explanation - Nitrate provides an alternative electron acceptor, stimulating microbial activity in the presence of hydrocarbons.
Correct answer is: Sodium nitrate
Q.60 Which of the following is a major advantage of using a “dry” anaerobic digester for solid waste over a “wet” digester?
Higher methane production per unit mass
Lower capital cost and simpler operation
Faster digestion time
Ability to treat high‑strength wastewater
Explanation - Dry digesters handle higher solids content, need less water, and are generally less expensive to build.
Correct answer is: Lower capital cost and simpler operation
Q.61 In solid waste management, the term “source separation” means:
Separating waste at the landfill
Sorting waste at the point of generation into different streams
Mixing all waste types together
Incinerating waste before collection
Explanation - Source separation facilitates recycling, composting, and reduces contamination of waste streams.
Correct answer is: Sorting waste at the point of generation into different streams
Q.62 Which of the following gases is typically NOT a component of landfill gas?
Methane (CH₄)
Carbon Dioxide (CO₂)
Hydrogen Sulfide (H₂S)
Ozone (O₃)
Explanation - Ozone is a secondary pollutant formed in the atmosphere, not a direct product of landfill decomposition.
Correct answer is: Ozone (O₃)
Q.63 What does the term “bio‑leaching” refer to in the context of waste management?
Using microbes to extract metals from electronic waste
Leaching water from compost piles
Burning waste to produce leachate
Adding acids to neutralize leachate
Explanation - Bio‑leaching employs microorganisms that produce acids or other agents to solubilize metals for recovery.
Correct answer is: Using microbes to extract metals from electronic waste
Q.64 Which of the following is the most appropriate method to assess the biodegradability of a new polymer intended for single‑use packaging?
Thermogravimetric analysis
Biodegradation test in composting conditions (e.g., ASTM D6400)
Electrical conductivity measurement
Hardness test
Explanation - Standardized compostability tests evaluate the rate and extent of polymer breakdown under controlled composting.
Correct answer is: Biodegradation test in composting conditions (e.g., ASTM D6400)
Q.65 Which of the following best explains why “methane capture” from landfills is considered a climate‑change mitigation strategy?
Methane has a global warming potential ~28–36 times greater than CO₂ over 100 years
Methane is inert and does not affect climate
Methane is a harmless gas
Methane reduces soil fertility
Explanation - Capturing methane prevents its release into the atmosphere, reducing the overall greenhouse effect.
Correct answer is: Methane has a global warming potential ~28–36 times greater than CO₂ over 100 years
Q.66 Which of the following is a typical indicator that a compost pile is too dry?
Strong ammonia odor
Rapid temperature rise above 70 °C
Low moisture and poor temperature increase
Excessive leachate formation
Explanation - Insufficient moisture limits microbial activity, resulting in low temperature rise and slow decomposition.
Correct answer is: Low moisture and poor temperature increase
Q.67 In electrical engineering, what does the term “ground resistance” refer to?
Resistance of a circuit to alternating current
Resistance between a grounding electrode and earth
Resistance of a transformer coil
Resistance of a battery
Explanation - Ground resistance measures how effectively a grounding system can dissipate fault currents into the earth.
Correct answer is: Resistance between a grounding electrode and earth
Q.68 Which of the following processes is primarily used to convert plastic waste into fuel via thermal cracking?
Pyrolysis
Fermentation
Hydrolysis
Electrolysis
Explanation - Pyrolysis heats plastic in the absence of oxygen, breaking it into liquid hydrocarbons, gases, and char.
Correct answer is: Pyrolysis
Q.69 What is the main function of a “stormwater detention basin” near a landfill site?
To store waste material
To temporarily hold runoff and reduce peak flow to the landfill
To generate electricity
To incinerate leachate
Explanation - Detention basins control the rate of stormwater entering the landfill, reducing erosion and leachate generation.
Correct answer is: To temporarily hold runoff and reduce peak flow to the landfill
Q.70 Which microbial group is primarily responsible for nitrification in aerobic composting systems?
Methanogens
Ammonia‑oxidizing bacteria (AOB)
Sulfate‑reducing bacteria
Fungal hyphae
Explanation - AOB oxidize ammonia to nitrite, the first step of nitrification, under aerobic conditions.
Correct answer is: Ammonia‑oxidizing bacteria (AOB)
Q.71 Which of the following best defines “sustainability” in the context of solid waste management?
Managing waste only through landfilling
Balancing environmental protection, economic viability, and social acceptance
Increasing the amount of waste generated each year
Eliminating all recycling programs
Explanation - Sustainability seeks solutions that meet present needs without compromising future generations, integrating the three pillars.
Correct answer is: Balancing environmental protection, economic viability, and social acceptance
Q.72 What does the term “bio‑catalyst” refer to in the context of waste treatment?
A metal alloy used to break down waste
An enzyme or whole organism that speeds up a biochemical reaction
A high‑temperature furnace
A mechanical shredder
Explanation - Biocatalysts accelerate degradation or transformation of pollutants without being consumed.
Correct answer is: An enzyme or whole organism that speeds up a biochemical reaction
Q.73 Which of the following is a common indicator that a landfill gas collection system is operating efficiently?
High pressure in the gas lines
Low methane concentration in the collected gas
Steady increase in landfill temperature
Reduced surface odors around the landfill
Explanation - Effective gas capture removes odorous gases, reducing smell and indicating good system performance.
Correct answer is: Reduced surface odors around the landfill
Q.74 What is the main benefit of using “electro‑flocculation” for treating leachate?
It adds nutrients to the leachate
It removes suspended particles and some metals without chemicals
It heats the leachate to high temperatures
It converts leachate into solid waste
Explanation - Electro‑flocculation induces particle aggregation using electric fields, facilitating removal by sedimentation.
Correct answer is: It removes suspended particles and some metals without chemicals
Q.75 Which of the following is a key factor in determining the design life of a municipal landfill?
The color of the waste
Projected waste generation rate
Number of nearby schools
Altitude of the site
Explanation - Estimating how much waste will be placed determines the landfill’s size and lifespan.
Correct answer is: Projected waste generation rate
Q.76 In the context of bioremediation, what does the acronym “PAH” stand for?
Polyacrylate Hydrogel
Polycyclic Aromatic Hydrocarbon
Photovoltaic Alkaline Heater
Potassium Ammonium Hydroxide
Explanation - PAHs are a group of organic pollutants with multiple aromatic rings, often targeted in bioremediation.
Correct answer is: Polycyclic Aromatic Hydrocarbon
Q.77 Which of the following is a common method for stabilizing organic waste before landfilling?
Pre‑aeration
Mechanical compaction
Pre‑drying
All of the above
Explanation - Aeration reduces odor, compaction reduces volume, and drying lowers leachate production, all contributing to waste stabilization.
Correct answer is: All of the above
Q.78 Which of the following gases is typically removed from landfill gas before it can be used in a natural‑gas pipeline?
Carbon dioxide
Methane
Nitrogen
Oxygen
Explanation - CO₂ dilutes methane; removal raises the calorific value to meet pipeline specifications.
Correct answer is: Carbon dioxide
Q.79 What is the primary reason that biodegradable plastics are preferred over conventional plastics for compostable applications?
They are cheaper to produce
They break down into harmless substances under composting conditions
They have higher tensile strength
They do not require any waste management
Explanation - Biodegradable plastics can be mineralized by microbes, leaving no persistent residues.
Correct answer is: They break down into harmless substances under composting conditions
Q.80 In a waste‑to‑energy plant, what is the purpose of a “feed‑stock pre‑processor”?
To burn the waste directly
To shred, dry, and homogenize waste for efficient combustion
To store waste for decades
To filter exhaust gases
Explanation - Pre‑processing ensures uniform fuel characteristics, improving combustion efficiency and emissions control.
Correct answer is: To shred, dry, and homogenize waste for efficient combustion
Q.81 Which of the following is a typical indicator of successful phytoremediation at a contaminated site?
Decrease in metal concentration in plant tissues over time
Increase in visible weeds
Rise in soil pH to >12
No change in contaminant levels
Explanation - Effective phytoremediation shows reduced contaminant levels in both plant tissue (if harvested) and the soil.
Correct answer is: Decrease in metal concentration in plant tissues over time
Q.82 What is the main environmental advantage of using a “dry tomb” landfill design compared to a traditional wet landfill?
Higher methane production
Reduced leachate generation due to minimal water infiltration
Faster decomposition of waste
Lower construction costs
Explanation - Dry tomb landfills limit water entry, thus minimizing leachate formation and associated contamination risk.
Correct answer is: Reduced leachate generation due to minimal water infiltration
Q.83 Which of the following parameters is most critical when designing an aerobic composting system for municipal solid waste?
Oxygen diffusion rate
Magnetic field strength
Electrical voltage
Acidic pH
Explanation - Adequate oxygen supply is essential for aerobic microbes to decompose organic matter efficiently.
Correct answer is: Oxygen diffusion rate
Q.84 In electrical terms, what does “ground fault current” refer to in a waste‑handling facility?
Current flowing through a normal circuit
Current that flows through an unintended path to ground, often due to insulation failure
Current used to power lighting
Current generated by solar panels
Explanation - Ground fault currents can cause equipment damage and safety hazards; they must be detected and cleared promptly.
Correct answer is: Current that flows through an unintended path to ground, often due to insulation failure
Q.85 Which of the following is a common indicator that a landfill has become anaerobically stabilized?
Rapid temperature increase above 70 °C
Consistently low methane production
High levels of dissolved oxygen in leachate
Strong odor of hydrogen sulfide
Explanation - As biodegradable material is exhausted, methane generation declines, indicating stabilization.
Correct answer is: Consistently low methane production
Q.86 What does the term “biodegradation rate constant (k)” represent in kinetic studies of waste decomposition?
The amount of waste produced per day
The speed at which a substance is broken down by microorganisms
The electrical conductivity of soil
The temperature of the compost pile
Explanation - The rate constant k quantifies how quickly a contaminant or organic matter is degraded under given conditions.
Correct answer is: The speed at which a substance is broken down by microorganisms
Q.87 Which of the following waste streams is most suitable for treatment by “thermal desorption”?
Organic kitchen waste
Soil contaminated with polycyclic aromatic hydrocarbons (PAHs)
Glass bottles
Paper and cardboard
Explanation - Thermal desorption heats soil to volatilize PAHs, allowing their capture while leaving the soil largely intact.
Correct answer is: Soil contaminated with polycyclic aromatic hydrocarbons (PAHs)
Q.88 Which of the following is a common reason for the failure of a landfill gas collection system?
Over‑pressurization of the gas collection wells
Excessive moisture in the waste mass
Inadequate sealing of the landfill cap
All of the above
Explanation - Pressurization, moisture, and cap integrity all influence gas migration and collection efficiency.
Correct answer is: All of the above
Q.89 What does the acronym “BOD5” denote in wastewater analysis?
Biological oxygen demand measured over 5 days
Base of density at 5 °C
Bacterial oxygen diffusion at 5 µm
Biosolids oxidation degree 5
Explanation - BOD5 is a standard test indicating the amount of dissolved oxygen required for microbial decomposition of organic matter over five days.
Correct answer is: Biological oxygen demand measured over 5 days
Q.90 Which of the following is the most suitable technique for monitoring the pH of leachate in real time?
Colorimetric test strips
Electrode‑based pH probe with data logger
Visual inspection
Temperature sensor
Explanation - An electronic pH probe provides continuous, accurate measurements and can be linked to a data acquisition system.
Correct answer is: Electrode‑based pH probe with data logger
Q.91 Which of the following is a primary goal of “circular economy” principles applied to solid waste?
Maximizing waste disposal in landfills
Keeping resources in use for as long as possible through reuse and recycling
Increasing the production of single‑use items
Eliminating all forms of waste treatment
Explanation - Circular economy seeks to close material loops, reducing the need for virgin resources and waste generation.
Correct answer is: Keeping resources in use for as long as possible through reuse and recycling
Q.92 Which of the following best describes the term “bio‑adsorption”?
Removal of pollutants by physical adsorption onto dead biomass
Combustion of waste to produce energy
Mechanical shredding of solid waste
Chemical oxidation of metals
Explanation - Bio‑adsorption uses the surface properties of dead microbial cells or plant material to bind contaminants.
Correct answer is: Removal of pollutants by physical adsorption onto dead biomass
Q.93 Which of the following is the most common method for estimating the volume of municipal solid waste generated per capita per day?
Survey of household waste bins
Satellite imaging
Electrical load analysis
Water consumption measurement
Explanation - Direct waste audits and surveys provide reliable per‑capita generation rates for planning.
Correct answer is: Survey of household waste bins
Q.94 In bioremediation, the addition of a carbon source such as glucose is intended to:
Inhibit microbial activity
Provide energy for microbes to degrade pollutants
Raise the pH of the soil
Increase the temperature of the site
Explanation - A supplemental carbon source fuels microbial metabolism, enhancing the breakdown of target contaminants.
Correct answer is: Provide energy for microbes to degrade pollutants
Q.95 Which of the following is the most important factor when selecting a plant species for phytoremediation of a site contaminated with cadmium?
Fast growth rate
High leaf area index
Ability to hyperaccumulate cadmium in harvestable tissues
Resistance to drought
Explanation - Hyperaccumulators concentrate the metal in above‑ground parts that can be harvested and removed.
Correct answer is: Ability to hyperaccumulate cadmium in harvestable tissues
Q.96 What is the main purpose of a “leachate recirculation” system in a landfill?
To increase the amount of methane produced
To enhance waste decomposition by maintaining moisture
To reduce the height of the waste pile
To capture landfill gas
Explanation - Recirculating leachate re‑hydrates the waste, promoting microbial activity and faster stabilization.
Correct answer is: To enhance waste decomposition by maintaining moisture
Q.97 Which of the following is a typical characteristic of an “open dumping” site?
Engineered liners
Systematic waste segregation
Lack of containment and environmental controls
Gas collection system
Explanation - Open dumps have no engineered measures, leading to uncontrolled leachate and gas emissions.
Correct answer is: Lack of containment and environmental controls
Q.98 In a waste‑to‑energy plant, what is the function of a “scrubber” in the flue‑gas treatment train?
To increase the temperature of the gas
To remove acidic gases such as SO₂ and HCl
To add moisture to the gas
To compress the gas for storage
Explanation - Scrubbers use liquid sprays to absorb harmful acidic components from the combustion gases.
Correct answer is: To remove acidic gases such as SO₂ and HCl
Q.99 Which of the following is a primary advantage of using “bio‑electrochemical systems” (BES) for solid waste treatment?
They require high temperatures
They can simultaneously treat waste and generate electricity
They produce large amounts of solid residues
They need no microbial activity
Explanation - BES, such as microbial fuel cells, convert chemical energy from waste into electrical energy while degrading contaminants.
Correct answer is: They can simultaneously treat waste and generate electricity
Q.100 What does the term “organic loading rate (OLR)” refer to in an anaerobic digester treating solid waste?
The amount of organic material fed per unit volume per day
The temperature of the digester
The electrical power consumption of the digester
The height of the waste pile
Explanation - OLR is expressed as kg VS (volatile solids) m⁻³ day⁻¹ and determines digester performance and stability.
Correct answer is: The amount of organic material fed per unit volume per day
Q.101 Which of the following best describes the purpose of a “gas‑to‑energy” project at a landfill?
To store landfill gas for later use
To convert captured methane into usable electricity or heat
To increase the production of leachate
To prevent any gas from escaping the site
Explanation - Gas‑to‑energy systems harness the calorific value of methane for power generation, reducing greenhouse gas emissions.
Correct answer is: To convert captured methane into usable electricity or heat
Q.102 Which of the following is an example of “source reduction” in solid waste management?
Encouraging the use of reusable shopping bags
Installing more landfills
Increasing the number of incinerators
Exporting waste to other countries
Explanation - Source reduction aims to decrease waste generation at its origin, such as using reusable items instead of disposables.
Correct answer is: Encouraging the use of reusable shopping bags
Q.103 What is the main environmental benefit of using “compostable packaging” over traditional plastic packaging?
It never produces any waste
It decomposes into carbon dioxide, water, and biomass, reducing landfill burden
It requires no energy to produce
It is always cheaper
Explanation - Compostable materials are designed to break down biologically, returning nutrients to the soil and minimizing long‑term waste.
Correct answer is: It decomposes into carbon dioxide, water, and biomass, reducing landfill burden
Q.104 Which of the following is a key indicator that a compost pile has reached the “maturation” stage?
Strong ammonia odor
Dark, crumbly appearance with earthy smell
High temperature (>70 °C)
Presence of large, unbroken food pieces
Explanation - Mature compost is stable, has a uniform texture, and lacks unpleasant odors, indicating completion of decomposition.
Correct answer is: Dark, crumbly appearance with earthy smell
Q.105 Which of the following methods is most effective for reducing the emission of volatile organic compounds (VOCs) from a waste‑handling facility?
Installing a carbon filter system
Increasing the temperature of the waste
Using open‑air storage
Adding more waste
Explanation - Activated carbon adsorbs VOCs from exhaust gases, reducing atmospheric release.
Correct answer is: Installing a carbon filter system