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Engineering ExamSprint Handbook
Question 1. Which term best describes the principle that “mass cannot be created or destroyed” in an environmental system? A) Dalton’s Law B) Law of Conservation of Mass C) Henry’s Law D) Fick’s First Law Answer: B Explanation: The Law of Conservation of Mass states that mass entering a system must equal mass leaving plus any accumulation; it is the foundation of mass balances in environmental engineering. Question 2. In a steady‑state control volume, which term in the mass balance equation becomes zero? A) Input B) Output C) Accumulation D) Reaction Answer: C Explanation: At steady state, the accumulation of mass within the control volume is zero because the mass entering equals the mass leaving plus any net reaction. Question 3. For a pollutant that undergoes first‑order decay, the concentration after time t is given by C = C₀e^‑kt. What does the constant k represent? A) Initial concentration B) Decay rate constant C) Equilibrium constant D) Mass transfer coefficient
Engineering ExamSprint Handbook
Answer: B Explanation: In a first‑order kinetic expression, k is the decay (or reaction) rate constant governing how quickly the pollutant concentration decreases over time. Question 4. Which of the following is a conservative pollutant in surface water? A) BOD₅ B) Nitrate C) Dissolved oxygen D) Pathogenic bacteria Answer: B Explanation: Nitrate does not undergo significant chemical transformation or degradation in water, making it a conservative tracer; BOD₅, DO, and bacteria are non‑conservative. Question 5. The first law of thermodynamics applied to a wastewater treatment plant primarily ensures which of the following? A) Conservation of entropy B) Conservation of energy C) Conservation of mass D) Conservation of momentum Answer: B Explanation: The first law states that energy cannot be created or destroyed; in treatment plants, it is used to balance heat and work inputs and outputs. Question 6. The second law of thermodynamics is most relevant to which environmental engineering process? A) Mass balance of solids B) Heat transfer in a cooling tower
Engineering ExamSprint Handbook
A) Reaeration of oxygen from the atmosphere B) Consumption of oxygen by biochemical oxygen demand (BOD) C) Photolytic production of oxygen D. Oxidation of ammonia to nitrate Answer: B Explanation: k_d describes the rate at which BOD consumes dissolved oxygen, leading to deoxygenation. Question 10. The ultimate BOD (L₀) in the BOD equation BOD_t = L₀(1 – e⁻ᵏᵗ) represents: A) BOD measured after 5 days B) BOD that would be exerted if the water were incubated indefinitely C) Initial dissolved oxygen concentration D. Maximum reaeration rate Answer: B Explanation: L₀ is the total amount of oxygen that would be consumed if the sample were allowed to decompose completely. Question 11. Which of the following is a zero‑order reaction in water treatment? A) Chlorine decay in a well‑mixed tank B. Nitrification in an activated sludge system at low substrate concentration C. Hydrolysis of a pesticide under constant temperature D. Adsorption onto activated carbon when the surface is saturated Answer: D Explanation: When the adsorbent surface is saturated, the rate of adsorption becomes independent of concentration, exhibiting zero‑order kinetics.
Engineering ExamSprint Handbook
Question 12. Stokes’ Law is used to calculate: A) Turbulent shear stress in a pipe B) Settling velocity of small spherical particles in a fluid C) Diffusion coefficient of gases in air D. Heat transfer coefficient in a condenser Answer: B Explanation: Stokes’ Law relates particle size, fluid viscosity, and density difference to the terminal settling velocity of small spheres. Question 13. In coagulation, the primary purpose of adding alum (Al₂(SO₄)₃) is to: A) Increase pH to alkaline levels B) Provide a source of chlorine for disinfection C) Neutralize negative surface charges on colloids D. Promote biological growth Answer: C Explanation: Alum hydrolyzes to form positively charged species that neutralize the negative charges on suspended particles, facilitating floc formation. Question 14. The kinetic expression for disinfection by chlorine following Chick’s Law is: N = N₀e⁻kCt Which variable represents the disinfectant concentration? A) N B) N₀ C) k D. C Answer: D
Engineering ExamSprint Handbook
D. High temperature (>30 °C) Answer: C Explanation: Denitrifying bacteria use nitrate as an electron acceptor in the absence of dissolved oxygen. Question 18. Reverse osmosis membranes reject solutes primarily based on: A) Chemical reaction with the membrane surface B) Size exclusion and solution‑diffusion mechanisms C. Electrostatic attraction D. Biological degradation Answer: B Explanation: RO membranes separate water from solutes through size exclusion (pore size) and solution‑diffusion, where solutes cannot pass the dense polymer matrix. Question 19. Which parameter is most important for predicting the removal efficiency of a particulate control device such as a cyclone? A) Particle density B) Gas temperature C) Particle aerodynamic diameter D. Gas viscosity Answer: C Explanation: The aerodynamic diameter determines the particle’s inertia and its ability to be separated in a cyclone. Question 20. The dry adiabatic lapse rate (DALR) is approximately: A) 3 °C/km
Engineering ExamSprint Handbook
B) 6.5 °C/km C. 9.8 °C/km D. 12 °C/km Answer: C Explanation: DALR = 9.8 °C per kilometer for unsaturated air rising adiabatically. Question 21. A temperature inversion in the atmosphere most likely leads to: A) Enhanced vertical mixing B) Dispersion of pollutants aloft C. Trapping of pollutants near the ground D. Increased cloud formation Answer: C Explanation: Inversions create a stable layer that suppresses vertical mixing, causing pollutants to accumulate near the surface. Question 22. In the Gaussian plume model, the term σ_y represents: A) Standard deviation of concentration in the vertical direction B) Standard deviation of concentration in the cross‑wind (horizontal) direction C. Wind speed at stack height D. Stack exit temperature Answer: B Explanation: σ_y is the lateral dispersion parameter describing spread perpendicular to the wind direction. Question 23. The primary pollutant removed by an electrostatic precipitator (ESP) is: A) Gaseous SO₂
Engineering ExamSprint Handbook
Question 26. Which of the following is the most appropriate engineering control for reducing emissions of volatile organic compounds (VOCs) from a paint shop? A) Cyclone separator B) Thermal oxidizer C. Electrostatic precipitator D. Baghouse filter Answer: B Explanation: Thermal oxidizers combust VOCs at high temperature, converting them to CO₂ and water. Question 27. The primary purpose of a leachate collection system in a sanitary landfill is to: A) Generate electricity B) Prevent groundwater contamination C. Increase landfill gas production D. Accelerate waste decomposition Answer: B Explanation: Leachate collection captures contaminated liquid that percolates through waste, preventing it from reaching groundwater. Question 28. In the waste hierarchy, which option is considered the most preferred method of waste management? A) Landfilling B) Energy recovery C. Recycling D. Source reduction Answer: D
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Explanation: Source reduction (preventing waste generation) is the most preferred, followed by recycling, energy recovery, and disposal. Question 29. The Resource Conservation and Recovery Act (RCRA) primarily governs: A) Air emissions from factories B) Hazardous waste generation, transport, and disposal C. Water quality standards for streams D. Noise pollution limits Answer: B Explanation: RCRA establishes a “cradle‑to‑grave” framework for managing hazardous waste. Question 30. The Comprehensive Environmental Response, Compensation, and Liability Act (CERCLA) is commonly known as: A) The Clean Air Act B. The Superfund law C. The Safe Drinking Water Act D. The National Environmental Policy Act Answer: B Explanation: CERCLA, enacted in 1980, creates the Superfund program for cleaning up uncontrolled hazardous waste sites. Question 31. The LD₅₀ value of a chemical is defined as: A) The dose that causes death in 5 % of a test population B. The dose that causes death in 50 % of a test population C. The dose that causes a 5 % reduction in weight gain D. The dose that causes a 50 % reduction in enzyme activity
Engineering ExamSprint Handbook
C. Bacillus subtilis D. Staphylococcus aureus Answer: A Explanation: E. coli is widely used as an indicator of fecal contamination because it is present in large numbers in the intestines of warm‑blooded animals. Question 35. The term “BOD₅” denotes: A) The ultimate oxygen demand after infinite time B. The oxygen demand measured after 5 minutes C. The oxygen demand measured after 5 days at 20 °C D. The biochemical oxygen demand after 5 hours Answer: C Explanation: BOD₅ is the amount of dissolved oxygen consumed by microorganisms in a water sample over five days at 20 °C. Question 36. In water treatment, the term “softening” refers to the removal of: A) Dissolved organic carbon B. Calcium and magnesium ions C. Suspended solids D. Chlorine residuals Answer: B Explanation: Softening reduces hardness by precipitating calcium and magnesium as carbonate or sulfate salts. Question 37. Which of the following processes is most effective for removing dissolved ammonia from an industrial effluent?
Engineering ExamSprint Handbook
A) Primary sedimentation B. Ion exchange with zeolite C. Coagulation‑flocculation D. UV disinfection Answer: B Explanation: Zeolite ion exchange selectively removes ammonium ions from water. Question 38. The term “hydraulic retention time (HRT)” in a reactor is defined as: A) Volume of the reactor divided by influent flow rate B. Volume of the reactor multiplied by the influent flow rate C. Inlet concentration divided by outlet concentration D. Reaction rate constant multiplied by residence time Answer: A Explanation: HRT = reactor volume / influent flow rate; it indicates the average time a fluid element spends in the reactor. Question 39. In a continuous stirred‑tank reactor (CSTR), the steady‑state concentration of a reactant undergoing a first‑order reaction is given by: C = C₀/(1 + k·θ) What does θ represent? A) Reaction rate constant B. Hydraulic retention time C. Inlet concentration D. Temperature correction factor Answer: B
Engineering ExamSprint Handbook
Answer: C Explanation: Critical load is the maximum deposition or concentration an ecosystem can sustain without damage. Question 43. The “wet deposition” of atmospheric pollutants primarily occurs via: A) Rain, snow, or fog scavenging soluble gases and particles B. Direct emission from smokestacks C. Diffusion of gases into the soil D. Absorption onto vegetation surfaces Answer: A Explanation: Wet deposition involves precipitation removing soluble gases and particulate matter from the atmosphere. Question 44. Which of the following is the most common method for measuring particulate matter (PM₂.₅) concentration in the field? A) Gravimetric filter method B. UV‑Vis spectroscopy C. Conductivity probe D. Gas chromatography Answer: A Explanation: The gravimetric method collects particles on a filter and weighs the mass gain to determine PM₂.₅ concentration. Question 45. In the context of landfill gas, the primary components are: A) Methane and carbon dioxide B. Hydrogen sulfide and ammonia
Engineering ExamSprint Handbook
C. Sulfur dioxide and nitrogen oxides D. Ozone and volatile organic compounds Answer: A Explanation: Landfill gas is typically ~50 % methane and ~50 % carbon dioxide, with trace amounts of other gases. Question 46. The term “biogas” most accurately describes a mixture produced by: A) Thermal cracking of petroleum B. Anaerobic digestion of organic waste C. Photolysis of water vapor D. Electrolysis of seawater Answer: B Explanation: Biogas (mainly CH₄ and CO₂) is generated during anaerobic digestion of organic matter. Question 47. Which of the following is a primary advantage of using membrane bioreactors (MBRs) over conventional activated sludge systems? A) Lower capital cost B. Higher sludge age without loss of performance C. Ability to treat high‑temperature wastewaters D. Reduced need for aeration Answer: B Explanation: MBRs retain biomass longer, allowing higher sludge ages and improved treatment efficiency, albeit at higher cost. Question 48. In water distribution systems, “head loss” is primarily caused by:
Engineering ExamSprint Handbook
Question 51. In a batch reactor, the time required to achieve 90 % conversion for a first‑order reaction is given by: t₉₀ = (ln 10)/k. What does “ln 10” represent in this expression? A) Natural logarithm of the reaction order B. Natural logarithm of the conversion ratio (1‑0.9) C. Natural logarithm of the initial concentration D. Natural logarithm of the reactor volume Answer: B Explanation: ln 10 = – ln(0.1) corresponds to the logarithmic term for 90 % conversion (C/C₀ = 0.1). Question 52. Which of the following best describes “adsorption isotherm” in water treatment? A) Relationship between temperature and solubility B. Relationship between adsorbate concentration in solution and on the adsorbent at equilibrium C. Relationship between pressure and gas volume D. Relationship between flow rate and pressure drop Answer: B Explanation: An adsorption isotherm (e.g., Langmuir, Freundlich) relates equilibrium concentrations of solute in the liquid phase and on the solid phase. Question 53. The “Hazen–Williams equation” is used to estimate: A) Heat transfer coefficient in cooling towers B. Friction loss in water pipes
Engineering ExamSprint Handbook
C. Diffusion coefficient of gases in soil D. Settling velocity of particles Answer: B Explanation: The Hazen–Williams formula predicts head loss due to friction in water distribution pipelines. Question 54. In the context of groundwater flow, Darcy’s law states that the specific discharge (q) is proportional to: A) Hydraulic conductivity multiplied by hydraulic gradient B. Porosity divided by permeability C. Viscosity divided by pressure gradient D. Temperature gradient only Answer: A Explanation: q = K · i, where K is hydraulic conductivity and i is the hydraulic gradient. Question 55. The term “aquifer vulnerability” is most directly quantified by which index? A) Hilsenhoff Index B. DRASTIC index C. BOD₅/DO ratio D. Schmidt number Answer: B Explanation: DRASTIC evaluates aquifer susceptibility to contamination based on seven hydrogeologic parameters. Question 56. The “Reed–Solomon” method is used in environmental engineering for: A) Designing water distribution networks
