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Environmental Engineering B
Professional Exam Preparation
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Question 1. Which of the following best describes a steady-state material balance for a continuous stirred-tank reactor (CSTR)? A) Accumulation = 0 B) Accumulation = In – Out C) Accumulation = Reaction rate only D) Accumulation = In – Out + Generation Answer: A Explanation: In steady-state, the accumulation term in the mass balance is zero; thus inflow equals outflow plus any generation/consumption. Question 2. In an energy balance, which term represents heat transfer by radiation between two surfaces? A) Q_cond B) Q_conv C) Q_rad D) Q_work Answer: C Explanation: Q_rad denotes radiative heat transfer, governed by the Stefan-Boltzmann law, distinct from conduction (Q_cond) and convection (Q_conv). Question 3. The Arrhenius equation relates reaction rate constant k to temperature T. Which factor increases k exponentially? A) Activation energy (Ea) B) Pre-exponential factor (A)
Environmental Engineering B
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C) Decrease in temperature D) Increase in Ea Answer: B Explanation: The pre-exponential factor A multiplies the exponential term; a larger A directly raises k, while higher Ea reduces k. Question 4. For a weak acid HA in water, the expression for its acid dissociation constant Ka is: A) [H⁺][A⁻]/[HA] B) [HA]/([H⁺][A⁻]) C) [HA]·[H⁺]·[A⁻] D) [H⁺]²/[HA] Answer: A Explanation: Ka = ([H⁺][A⁻])/[HA] by definition of equilibrium for HA ⇌ H⁺
- A⁻. Question 5. Which of the following gases follows Henry’s Law most closely at low concentrations? A) O₂ in water at 25 °C B) CO₂ in seawater at 4 °C C) N₂ in water at 0 °C D) H₂S in water at 35 °C Answer: A
Environmental Engineering B
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Question 8. Which microbial metabolism produces methane as a final product? A) Aerobic respiration B) Fermentation C) Nitrification D) Anaerobic digestion Answer: D Explanation: Anaerobic digestion (methanogenesis) converts organic matter to CH₄ and CO₂ under oxygen-free conditions. Question 9. The LD₅₀ of a pesticide is 50 mg kg⁻¹. Which statement is true? A) 50 % of exposed organisms will die at any dose. B) 50 % of exposed organisms will die at 50 mg kg⁻¹. C) No organisms die below 50 mg kg⁻¹. D) All organisms die above 50 mg kg⁻¹. Answer: B Explanation: LD₅₀ is the dose lethal to 50 % of a test population. Question 10. In a river, the Streeter-Phelps model predicts a DO sag point downstream of a pollutant load. Which parameter primarily determines the distance to the sag point? A) Reaeration coefficient (k₂) B) Deoxygenation rate (k₁) C, BOD₅ of the influent
Environmental Engineering B
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D) River flow velocity Answer: B Explanation: The deoxygenation rate k₁ controls how rapidly BOD consumes DO, affecting the location of the minimum DO (sag). Question 11. Which of the following is a primary source of atmospheric CO₂? A) Volcanic eruptions B) Fossil-fuel combustion C) Oceanic outgassing D) Biomass decay in forests Answer: B Explanation: Anthropogenic CO₂ emissions are dominated by fossil-fuel burning. Question 12. A Gaussian plume model predicts ground-level concentration C at distance x downwind from a point source. Which factor does NOT appear in the standard equation? A) Wind speed (u) B) Stack height (H) C) Atmospheric stability class D) River discharge (Q) Answer: D Explanation: River discharge is irrelevant to atmospheric plume dispersion.
Environmental Engineering B
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D) Sodium bisulfate Answer: C Explanation: Alum (Al₂(SO₄)₃) hydrolyzes to form Al(OH)₃ flocs for particle removal. Question 16. In a rapid sand filter, the primary mechanism for particle removal is: A) Chemical oxidation B) Physical straining and adsorption C) Biological degradation D) Membrane filtration Answer: B Explanation: Rapid sand filters rely on straining, sedimentation, and adsorption to capture particles. Question 17. Which disinfectant produces the by-product trihalomethanes (THMs) when reacting with natural organic matter? A) Chlorine dioxide B) Ozone C) Chlorine (Cl₂) D) UV light Answer: C Explanation: Free chlorine reacts with humic substances to form THMs.
Environmental Engineering B
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Question 18. An activated sludge system is operating at an MLSS of 3000 mg L⁻¹. If the influent BOD₅ is 200 mg L⁻¹ and the effluent BOD₅ is 20 mg L⁻¹, what is the removal efficiency? A) 85 % B) 90 % C) 95 % D) 99 % Answer: C Explanation: Removal = (200-20)/200 = 0.90 = 90 %; actually answer B. (Corrected) So answer B. Question 19. Which of the following is a common advanced oxidation process (AOP) for tertiary wastewater treatment? A) Chlorination B) Ozonation followed by UV C) Aerobic digestion D) Coagulation-flocculation Answer: B Explanation: O₃/UV generates hydroxyl radicals that oxidize refractory organics. Question 20. In nitrogen removal, the process that converts ammonia (NH₃) to nitrate (NO₃⁻) is called: A) Nitrification B) Denitrification
Environmental Engineering B
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Question 23. A baghouse removes particles primarily by: A) Centrifugal force B) Inertial impaction on fabric filters C) Electrostatic attraction D) Chemical reaction Answer: B Explanation: Fabric filters trap particles via interception and impaction. Question 24. In a wet scrubber, the removal efficiency for soluble gases is governed by: A) Particle size distribution B) Henry’s law constant and liquid-to-gas ratio C) Electrostatic charge of droplets D) Stack temperature only Answer: B Explanation: Soluble gas absorption depends on solubility (Henry’s law) and contact area (liquid-to-gas ratio). Question 25. Which type of landfill liner system provides the highest hydraulic conductivity barrier? A) Compacted clay liner (CCL) B) Geosynthetic clay liner (GCL) C) Double-liner composite (CCL + geomembrane) D) No liner (uncontrolled)
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Answer: C Explanation: A composite liner combines low-permeability clay with a geomembrane for superior containment. Question 26. The RCRA “cradle-to-grave” system tracks hazardous waste from generation to: A) Recycling only B) Landfill disposal only C) Final disposal, including incineration, landfilling, or treatment D) Transportation only Answer: C Explanation: RCRA requires tracking hazardous waste through all stages to final disposal. Question 27. Which of the following is a primary driver for eutrophication in lakes? A) High dissolved oxygen levels B) Excess phosphorus loading C) Low temperature D) High salinity Answer: B Explanation: Phosphorus is the limiting nutrient; excess loads cause algal blooms and eutrophication.
Environmental Engineering B
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Answer: C Explanation: NPDES is the permitting program for point-source discharges. Question 31. Which of the following is NOT a typical component of a human health risk assessment? A) Hazard identification B) Dose-response assessment C) Exposure assessment D) Economic cost-benefit analysis Answer: D Explanation: Economic analysis is not part of the risk assessment steps. Question 32. The EPA’s Toxic Release Inventory (TRI) primarily tracks: A) Air emissions from power plants B) Releases of listed toxic chemicals by industrial facilities C) Agricultural pesticide usage D) Municipal solid waste generation Answer: B Explanation: TRI requires reporting of toxic chemical releases by certain industries. Question 33. Which of the following best describes the concept of “bioaccumulation”?
Environmental Engineering B
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A) Transfer of a substance from soil to water B) Uptake of a chemical by an organism faster than it can be metabolized or excreted C) Degradation of a pollutant by microbes D) Dilution of a pollutant in the atmosphere Answer: B Explanation: Bioaccumulation is the buildup of substances in an organism’s tissues. Question 34. In a membrane filtration system, the term “flux” refers to: A) Pressure drop across the membrane B) Volume of permeate per unit area per unit time C) Concentration of solutes in the feed D) Membrane pore size Answer: B Explanation: Flux (L m⁻² h⁻¹) measures permeate flow per membrane area. Question 35. Which of the following is the most effective method for removing dissolved gases such as CO₂ from water? A) Sedimentation B) Aeration (stripping) C) Filtration D) Chlorination Answer: B
Environmental Engineering B
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B) Adsorption onto media C) Biofilm oxidation on the filter media D) Sedimentation of solids Answer: C Explanation: Trickling filters rely on a biofilm that oxidizes organic matter as wastewater flows over the media. Question 39. Which of the following statements about ozone (O₃) as a disinfectant is correct? A) It leaves no residual disinfectant after treatment. B) It produces chlorinated by-products. C) It is ineffective against viruses. D) It can be generated only by electrical discharge. Answer: A Explanation: O₃ decomposes to O₂, leaving no residual; it is a strong oxidant effective against many pathogens. Question 40. The “Kinetic” model for landfill gas generation uses which parameter to describe the rate of methane production? A) First-order decay constant (k) B) Hydraulic conductivity (K) C) Landfill volume (V) D) Leachate recirculation rate Answer: A
Environmental Engineering B
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Explanation: The first-order kinetic model uses a decay constant to predict methane generation over time. Question 41. Which of the following is the most common method for determining total suspended solids (TSS) in water? A) Gravimetric analysis after filtration B) Spectrophotometric measurement at 254 nm C) Conductivity probe D) pH meter Answer: A Explanation: TSS is measured by filtering a known volume, drying, and weighing the retained solids. Question 42. In the context of the Clean Air Act, “NAAQS” stands for: A) National Ambient Air Quality Standards B) New Airborne Aerosol Quantification System C) National Acidic Air Quality Survey D) Non-Attainment Area Quota System Answer: A Explanation: NAAQS are health-based standards for criteria pollutants. Question 43. The “pH” of a solution is defined as: A) The negative logarithm of the hydrogen ion concentration B) The logarithm of the hydroxide ion concentration
Environmental Engineering B
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Question 46. Which of the following contaminants is classified as a PFAS (per- and poly-fluoroalkyl substance)? A) Bisphenol A B) Perfluorooctanoic acid (PFOA) C) DDT D) Atrazine Answer: B Explanation: PFOA is a well-known PFAS with strong carbon-fluorine bonds. Question 47. In the context of groundwater remediation, “pump-and-treat” systems primarily rely on: A) In-situ chemical oxidation B) Extraction of contaminated groundwater followed by surface treatment C) Bioremediation via injected microbes D) Permeable reactive barriers Answer: B Explanation: Pump-and-treat removes groundwater, treats it above ground, and re-injects or discharges the clean water. Question 48. Which of the following best describes the “critical load” concept in air quality management? A) The maximum allowable emission from a single source B) The threshold concentration at which a pollutant causes immediate death
Environmental Engineering B
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C) The level of pollutant deposition that ecosystems can tolerate without adverse effects D) The minimum concentration needed for atmospheric chemistry to occur Answer: C Explanation: Critical load is the deposition amount an ecosystem can sustain without damage. Question 49. The “oxidation-reduction potential” (ORP) of water is measured in: A) Milligrams per liter (mg/L) B) Millivolts (mV) C) Degrees Celsius (°C) D) Pascals (Pa) Answer: B Explanation: ORP is expressed in millivolts, indicating the tendency of water to gain or lose electrons. Question 50. Which of the following is the primary purpose of a “sulfur dioxide (SO₂) scrubber” in flue-gas treatment? A) To oxidize SO₂ to SO₃ B) To absorb SO₂ into a liquid phase for removal C) To catalytically convert SO₂ to elemental sulfur D) To filter particulate matter only Answer: B
