Free Environmental Engineering MCQs with Answers
80 Environmental Engineering MCQs from Civil Engineering, each with the correct answer and a written explanation of why it is correct. Free and unlimited, with no account needed.
Environmental engineering examines water supply, water quality, treatment processes, wastewater collection and treatment, solid waste management, air pollution and public health protection. It covers sedimentation, coagulation, filtration, disinfection, biological treatment and disposal methods, while distinguishing drinking-water treatment from sewage treatment and BOD from COD.
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80 questions · page 3 of 4
- A. Neutralize acidity produced during alum reaction
- B. Increase the dissolved oxygen concentration
- C. Prevent all microbial growth in water
- D. Convert suspended solids into dissolved salts
Explanation: Alum hydrolysis produces acidity, so alkalinity helps maintain a suitable pH and supports formation of aluminium hydroxide flocs.
Correct answer: Neutralize acidity produced during alum reaction- A. Coarse grit and large floating debris
- B. Taste, odour and dissolved organic compounds
- C. Water hardness caused by calcium ions
- D. Settleable mineral particles in raw water
Explanation: Activated carbon adsorbs many dissolved organic substances that cause taste, odour and colour.
Correct answer: Taste, odour and dissolved organic compounds- A. Domestic sewage from household plumbing fixtures
- B. Stormwater through roof gutters and street inlets
- C. Groundwater through cracks and defective joints
- D. Industrial wastewater discharged through approved connections
Explanation: Infiltration is groundwater entering a sewer through cracks, joints or other defects below the groundwater level.
Correct answer: Groundwater through cracks and defective joints- A. The concentration of dissolved salts in sludge
- B. The chlorine demand of treated wastewater
- C. The oxygen content of return sludge
- D. The settling characteristics of activated sludge
Explanation: Sludge volume index relates the settled sludge volume to the mass of suspended solids and indicates how well activated sludge settles.
Correct answer: The settling characteristics of activated sludge- A. Bacteria and algae under natural conditions
- B. Coarse screens and mechanical compressors
- C. Chlorine and activated carbon particles
- D. Sand grains and pressure-driven membranes
Explanation: Oxidation ponds use bacteria to decompose organic matter, while algae provide oxygen through photosynthesis in the pond system.
Correct answer: Bacteria and algae under natural conditions- A. Converts all waste into harmless drinking water
- B. Greatly reduces waste volume through controlled combustion
- C. Eliminates the need to control air emissions
- D. Produces compost without requiring biodegradable material
Explanation: Controlled combustion can substantially reduce the volume of municipal solid waste and may also recover energy.
Correct answer: Greatly reduces waste volume through controlled combustion- A. Thermal stratification caused by heated effluent
- B. Desalination and reduced electrical conductivity
- C. Eutrophication and excessive algal growth
- D. Immediate removal of dissolved oxygen by filtration
Explanation: Nitrogen and phosphorus are nutrients that can stimulate excessive algal and aquatic plant growth.
Correct answer: Eutrophication and excessive algal growth- A. Sulfuric acid aerosol formed in the atmosphere
- B. Ozone formed by reactions in sunlight
- C. Peroxyacetyl nitrate formed in photochemical smog
- D. Sulfur dioxide emitted directly from fuel combustion
Explanation: A primary pollutant is released directly from a source, and sulfur dioxide is emitted during combustion of sulfur containing fuels.
Correct answer: Sulfur dioxide emitted directly from fuel combustion- A. Provides little persistent residual in the distribution system
- B. Cannot inactivate bacteria under any operating condition
- C. Always increases the hardness of treated water
- D. Requires suspended solids to remain in the water
Explanation: Ozone is a strong disinfectant, but it decomposes relatively quickly and therefore provides little lasting protection in distribution…
Correct answer: Provides little persistent residual in the distribution system- A. Dissolved oxygen molecules in the tank water
- B. Suspended microbial solids in the aerated mixture
- C. Settleable grit collected before biological treatment
- D. Chlorine compounds remaining after disinfection
Explanation: Mixed liquor suspended solids are the suspended solids present in the aeration tank, including the microbial flocs responsible for…
Correct answer: Suspended microbial solids in the aerated mixture- A. Pathogenic microorganisms
- B. Dissolved mineral salts
- C. Large floating and suspended debris
- D. Fine colloidal particles
Explanation: Bar screens physically intercept large materials such as sticks, rags and plastics before later treatment units.
Correct answer: Large floating and suspended debris- A. Chlorine comparator
- B. pH meter
- C. BOD incubator
- D. Nephelometer
Explanation: A nephelometer measures turbidity by detecting light scattered by suspended particles in water.
Correct answer: Nephelometer- A. Reverse osmosis
- B. Rapid sand filtration
- C. Microfiltration
- D. Plain sedimentation
Explanation: Reverse osmosis uses pressure to force water through a semipermeable membrane while retaining many dissolved salts.
Correct answer: Reverse osmosis- A. Storage for treated wastewater
- B. Access for inspection and cleaning
- C. Additional biological treatment
- D. Removal of dissolved oxygen
Explanation: Manholes provide access at changes in sewer direction, slope, size and junctions so that inspection and cleaning can be carried out.
Correct answer: Access for inspection and cleaning- A. The concentration of dissolved oxygen in rivers
- B. The need for household water meters
- C. Stormwater entering the sewage-treatment plant
- D. The production of water-treatment chemicals
Explanation: Separate systems carry sanitary sewage and stormwater through different pipes, so rainfall produces less hydraulic loading at a…
Correct answer: Stormwater entering the sewage-treatment plant- A. Dissolved sodium chloride
- B. Large floating objects
- C. Coarse mineral grit
- D. Biodegradable organic matter
Explanation: Secondary treatment uses microorganisms to convert biodegradable organic matter into more stable products, followed by separation of…
Correct answer: Biodegradable organic matter- A. Contaminated liquid draining through waste
- B. Methane collected from decomposing waste
- C. Ash remaining after waste combustion
- D. Stormwater flowing over an unused site
Explanation: Leachate forms when water passes through waste and dissolves or carries contaminants with it.
Correct answer: Contaminated liquid draining through waste- A. Dissolved salts from wastewater
- B. Particulate matter from gas streams
- C. Nitrogen gas from combustion air
- D. Noise from industrial machinery
Explanation: A baghouse passes polluted gas through fabric bags that trap particulate matter on their surfaces.
Correct answer: Particulate matter from gas streams- A. Coarse soil particles
- B. Dissolved calcium ions
- C. Volatile organic compounds
- D. Water-treatment alum
Explanation: Sunlight drives reactions between nitrogen oxides and volatile organic compounds, producing ozone and other oxidants associated with…
Correct answer: Volatile organic compounds- A. Plain sedimentation
- B. Coarse screening
- C. Grit removal
- D. Granular activated carbon adsorption
Explanation: Granular activated carbon removes many organic compounds by adsorption onto its highly porous surface, improving taste and odour.
Correct answer: Granular activated carbon adsorption