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Engineering ExamSprint Handbook
Question 1. Which of the following statements correctly defines an open system in environmental engineering? A) No mass or energy crosses the system boundary. B) Only energy crosses the boundary, not mass. C) Both mass and energy can cross the boundary. D) Mass crosses the boundary, but energy does not. Answer: C Explanation: An open system allows exchange of both mass and energy with its surroundings, unlike closed (energy only) or isolated (neither) systems. Question 2. In the general balance equation, Accumulation = Input – Output + Generation – Consumption, which term represents a non-conservative pollutant that decays over time? A) Input B) Output C) Generation D) Consumption Answer: D Explanation: Consumption accounts for removal of a pollutant through decay or reaction, characteristic of non-conservative substances. Question 3. For a steady-state process, which of the following is true? A) Accumulation term is positive. B) Accumulation term is negative. C) Accumulation term is zero. D) Accumulation term can be any value. Answer: C
Engineering ExamSprint Handbook
Explanation: At steady state, the amount stored in the system does not change, so accumulation = 0. Question 4. Which of the following is a conservative pollutant? A) Radioactive iodine B) Sodium chloride (salt) C) Methane undergoing oxidation D) Hydrogen sulfide that volatilizes Answer: B Explanation: Salt does not undergo chemical transformation in the environment, making it conservative. Question 5. The stoichiometric coefficient of O₂ in the complete combustion of methane (CH₄) is: A) 1 B) 2 C) 3 D) 4 Answer: D Explanation: CH₄ + 2O₂ → CO₂ + 2H₂O; the coefficient for O₂ is 2, but the balanced equation is CH₄ + 2O₂, so the answer is B. (Correction: the correct coefficient is 2; therefore the answer should be B.) Question 6. Which principle explains the shift in equilibrium when the concentration of a reactant is increased? A) Le Chatelier’s principle B) Hess’s law
Engineering ExamSprint Handbook
A) 5.8 days B) 23.1 days C) 0.69 days D) 33.3 days Answer: A Explanation: t½ = ln(2)/k = 0.693/0.03 ≈ 23.1 days. (Correction: the correct half-life is 23.1 days, so answer B.) Question 10. Which of the following water quality parameters is a biological indicator? A) Turbidity B. Color C. Total coliforms D. Temperature Answer: C Explanation: Total coliforms indicate microbial contamination, a biological aspect of water quality. Question 11. The most appropriate method to remove suspended solids larger than 10 μm from raw water is: A) Reverse osmosis B) Coagulation-flocculation followed by sedimentation C) Ultraviolet disinfection D) Activated carbon adsorption Answer: B Explanation: Coagulation-flocculation aggregates fine particles, and sedimentation removes the resulting flocs efficiently.
Engineering ExamSprint Handbook
Question 12. Stokes’ Law is applicable for calculating settling velocity when the particle Reynolds number is: A) > 1000 B) 100– C) 1– D) < 1 Answer: D Explanation: Stokes’ Law assumes laminar flow around the particle, valid for Re < 1. Question 13. In rapid sand filtration, the primary removal mechanism for particles < 0.2 μm is: A) Sedimentation B) Mechanical straining C) Adsorption and interception D) Biological degradation Answer: C Explanation: Small particles are removed by physical-chemical interactions such as adsorption onto the sand grains and interception. Question 14. The Chick-Watson law for disinfection can be expressed as: A) N/N₀ = e^(−kCt) B) N/N₀ = 1 − kCt C) N/N₀ = kCt D) N/N₀ = e^(kCt) Answer: A
Engineering ExamSprint Handbook
D) Mass of volatile solids only Answer: A Explanation: MLSS includes both organic (biomass) and inorganic suspended solids present in the aeration basin. Question 18. The stoichiometric ratio of BOD to COD for typical municipal wastewater is approximately: A) 0. B) 0. C) 0. D) 1. Answer: C Explanation: COD measures total oxidizable material; typical BOD/COD ratio for domestic wastewater is around 0.6. Question 19. Nitrification in wastewater treatment is an aerobic process that converts: A) NH₄⁺ → NO₂⁻ → NO₃⁻ B) NO₃⁻ → NO₂⁻ → NH₄⁺ C) NH₃ → N₂ → NO₃⁻ D) NO₂⁻ → N₂O → N₂ Answer: A Explanation: Nitrifying bacteria first oxidize ammonia to nitrite, then nitrite to nitrate. Question 20. Denitrification is typically carried out under which condition? A) High dissolved oxygen
Engineering ExamSprint Handbook
B) Anoxic (oxygen-free) conditions C) Aerobic, high temperature D) Light exposure Answer: B Explanation: Denitrifying bacteria use nitrate as an electron acceptor in the absence of dissolved oxygen. Question 21. Which pollutant is classified as a “criteria pollutant” by the U.S. EPA? A) Benzene B) DDT C) O₃ (ground-level ozone) D) PCBs Answer: C Explanation: Ground-level ozone is one of the six EPA criteria pollutants. Question 22. The photochemical formation of ground-level ozone mainly involves which precursor gases? A) CO and SO₂ B) NOₓ and VOCs C) NH₃ and CH₄ D) Pb and Hg Answer: B Explanation: NOₓ (NO and NO₂) and volatile organic compounds (VOCs) react under sunlight to produce ozone.
Engineering ExamSprint Handbook
Question 26. Which of the following is NOT a component of the waste hierarchy? A) Reduce B) Incinerate C) Reuse D) Recycle Answer: B Explanation: Incineration is a disposal option, not a preferred step in the hierarchy (which prioritizes reduction, reuse, recycling, recovery, then disposal). Question 27. In a sanitary landfill, the primary purpose of a geomembrane liner is to: A) Provide structural support for waste placement B) Prevent leachate migration into groundwater C) Capture landfill gas for energy use D) Accelerate waste decomposition Answer: B Explanation: Geomembrane liners act as an impermeable barrier to isolate leachate. Question 28. The RCRA regulation primarily addresses: A) Air emissions from factories B) Water quality standards for rivers C) Management of hazardous waste from “cradle-to-grave” D) Noise pollution in urban areas Answer: C Explanation: The Resource Conservation and Recovery Act (RCRA) governs the entire lifecycle of hazardous waste.
Engineering ExamSprint Handbook
Question 29. The incremental lifetime cancer risk (ILCR) is calculated by multiplying the chronic daily intake (CDI) by: A) The reference dose (RfD) B) The cancer slope factor (CSF) C) The tolerable daily intake (TDI) D) The acceptable daily intake (ADI) Answer: B Explanation: ILCR = CDI × CSF; CSF quantifies cancer potency. Question 30. Which greenhouse gas has the highest global warming potential (GWP) over a 100-year horizon? A) CO₂ B) CH₄ C) N₂O D) SF₆ Answer: D Explanation: Sulfur hexafluoride (SF₆) has a GWP ≈ 23,500, far exceeding the others. Question 31. In a life-cycle assessment (LCA), the “use phase” refers to: A) Extraction of raw materials B) Manufacturing of the product C) Operation and maintenance of the product D) End-of-life disposal Answer: C
Engineering ExamSprint Handbook
C) K = ([A][B])/([C][D])
D) K = ([C][D])/([A][B])
Answer: B Explanation: K_eq = (activities of products)ⁿ/(activities of reactants)ⁿ. Question 35. The pH of a solution containing 0.01 M HCl is approximately: A) 2 B) 4 C) 7 D) 12 Answer: A Explanation: Strong acid fully dissociates; pH = –log(0.01) = 2. Question 36. In a first-order decay of a pollutant with half-life of 10 days, the concentration after 30 days will be: A) 12.5 % of the initial B) 25 % of the initial C) 50 % of the initial D) 75 % of the initial Answer: A Explanation: After each half-life, concentration halves. After 3 half-lives (30 days) → (½)³ = 0.125 = 12.5 %. Question 37. Which of the following best describes the role of alum (Al₂(SO₄)₃) in water treatment? A) Disinfectant
Engineering ExamSprint Handbook
B) Coagulant that neutralizes particle charge C) pH buffer D) Flocculant polymer Answer: B Explanation: Alum provides Al³⁺ ions that neutralize negative surface charges, facilitating coagulation. Question 38. The term “turbidity” in water quality is measured in: A) mg/L B) NTU (nephelometric turbidity units) C) ppm D) mSv/h Answer: B Explanation: Turbidity quantifies light scattering by suspended particles, expressed in NTU. Question 39. The rate expression for a zero-order reaction is: A) r = k[A] B) r = k[A]² C) r = k (independent of concentration) D) r = k/ [A] Answer: C Explanation: Zero-order rate is constant, not dependent on reactant concentration. Question 40. Which of the following is a secondary pollutant? A) SO₂ emitted from a power plant
Engineering ExamSprint Handbook
Question 43. The term “ultimate BOD (L₀)” represents: A) BOD measured after 5 days B) The total amount of biodegradable organic matter that will be consumed over infinite time C) BOD after 30 days D) BOD after oxygen saturation has been reached Answer: B Explanation: L₀ is the theoretical maximum BOD if the substrate were allowed to degrade completely. Question 44. In a wastewater treatment plant, the “solids retention time (SRT)” influences: A) Hydraulic loading rate only B) The concentration of dissolved gases C) The growth of slow-growing microorganisms such as nitrifiers D) The temperature of the effluent Answer: C Explanation: Longer SRTs retain biomass longer, favoring slow-growing species like nitrifiers. Question 45. Which of the following is a common indicator of eutrophication in a lake? A) High dissolved oxygen throughout the water column B) Clear water with low nutrient concentrations C) Algal blooms and low dissolved oxygen in bottom waters D) High pH (> 9) with low conductivity Answer: C
Engineering ExamSprint Handbook
Explanation: Excess nutrients stimulate algal growth; subsequent decay depletes oxygen, especially near the bottom. Question 46. The term “adsorption isotherm” most commonly refers to which model? A) Michaelis-Menten B) Arrhenius equation C) Freundlich or Langmuir isotherm D) Henry’s law Answer: C Explanation: Freundlich and Langmuir equations describe how solutes adsorb onto solid surfaces at equilibrium. Question 47. Which of the following gases has the highest solubility in water at 25 °C? A) O₂ B) N₂ C) CO₂ D) CH₄ Answer: C Explanation: CO₂ is about 25-times more soluble than O₂ in water at 25 °C. Question 48. In a landfill gas collection system, the primary component of the gas that can be used for energy recovery is: A) Carbon monoxide B) Methane C) Hydrogen sulfide
Engineering ExamSprint Handbook
C) CDI × CSF
D) ILCR / RfD Answer: A Explanation: HQ = Chronic Daily Intake ÷ Reference Dose; values > 1 indicate potential concern. Question 52. Which of the following processes is most effective for removing dissolved inorganic nitrogen (ammonia) from wastewater? A) Primary sedimentation B) Chemical precipitation with lime C) Nitrification-denitrification D) Membrane ultrafiltration Answer: C Explanation: Biological nitrification converts ammonia to nitrate; denitrification reduces nitrate to nitrogen gas. Question 53. In a packed-bed column used for air pollution control, the term “mass transfer zone” (MTZ) refers to: A) The region where adsorption equilibrium is achieved instantly B) The length of the bed where most solute transfer occurs C) The inlet section where flow is turbulent D) The outlet section where gas exits unchanged Answer: B Explanation: MTZ is the portion of the bed where concentration gradients drive mass transfer. Question 54. The “Henry’s law constant” for a gas describes:
Engineering ExamSprint Handbook
A) The ratio of its solubility in water to its partial pressure in the gas phase B) The rate of its chemical reaction in water C) Its diffusion coefficient in air D) Its equilibrium constant for acid-base reactions Answer: A Explanation: Henry’s law relates dissolved concentration to gas-phase partial pressure. Question 55. Which of the following is a common method for treating PFAS-contaminated groundwater? A) Conventional chlorination B) Granular activated carbon adsorption C) Biological nitrification D) Simple aeration Answer: B Explanation: Granular activated carbon can adsorb many PFAS compounds, though treatment is challenging. Question 56. The “ozone depletion potential” (ODP) is a metric for: A) Global warming potential of gases B) Ability of a substance to destroy stratospheric ozone C) Toxicity to aquatic life D) Persistence in soil Answer: B Explanation: ODP quantifies the relative impact of a substance on ozone layer depletion.
