Principles and Practice of Engineering Exam (PE) Environmental Engineering (PE Environmental) Syllabus

Environmental Engineering (PE Environmental) syllabus — full chapter and topic list

Expand any chapter to see its topics and sub-topics. This is the whole examinable outline for Environmental Engineering (PE Environmental) in Principles and Practice of Engineering Exam (PE), not a summary of it.

1. 1

   Water and Wastewater Engineering

   3 topics

   • Water Treatment
     • Coagulation, flocculation, and sedimentation
     • Filtration and disinfection
     • Softening and membrane processes
   • Wastewater Treatment
     • Primary and secondary treatment
     • Activated sludge and nutrient removal
     • Sludge handling and biosolids
   • Collection and Distribution
     • Pipe network hydraulics
     • Pumping and storage
2. 2

   Air Quality and Emissions

   3 topics

   • Air Pollutants
     • Criteria pollutants and sources
     • Emission factors and inventories
   • Control Technologies
     • Particulate control devices
     • Gaseous pollutant control
   • Dispersion and Regulation
     • Atmospheric dispersion modeling
     • Clean Air Act and permitting
3. 3

   Solid and Hazardous Waste

   3 topics

   • Solid Waste Management
     • Collection, recycling, and diversion
     • Landfill design and leachate
   • Hazardous Waste
     • RCRA and CERCLA frameworks
     • Site remediation technologies
   • Groundwater and Soil
     • Contaminant transport
     • Remediation design
4. 4

   Environmental Science and Regulation

   3 topics

   • Environmental Chemistry and Microbiology
     • Reaction kinetics and mass balance
     • Pathogens and indicator organisms
   • Risk Assessment
     • Exposure and dose-response
     • Risk characterization
   • Regulatory Framework
     • Clean Water Act and NPDES
     • Safe Drinking Water Act

Environmental Engineering (PE Environmental) flashcards for Principles and Practice of Engineering Exam (PE)

24 of 72 cards from the Environmental Engineering (PE Environmental) deck — real questions with worked answers.

1. In drinking water treatment, what is the purpose of coagulation, and which chemical is the most common coagulant?

   Coagulation destabilizes suspended colloidal particles by neutralizing their negative surface charges so they can aggregate. The most common coagulant is aluminum sulfate (alum), $\ce{Al2(SO4)3 \cdot 14H2O}$; ferric chloride $\ce{FeCl3}$ is also widely used.

2. Write the reaction of alum with natural alkalinity (bicarbonate) during coagulation.

   $$\ce{Al2(SO4)3 \cdot 14H2O + 3Ca(HCO3)2 -> 2Al(OH)3(s) + 3CaSO4 + 6CO2 + 14H2O}$$ The $\ce{Al(OH)3}$ floc sweeps out colloids; alkalinity is consumed.

3. State the overflow rate (surface loading rate) formula for a sedimentation basin and what it represents.

   $$v_o = \frac{Q}{A_s}$$ where $Q$ is flow rate and $A_s$ is the surface (plan) area. Particles with settling velocity $v_s \geq v_o$ are completely removed, independent of basin depth (ideal Type I settling).

4. What is the Stokes' law expression for the terminal settling velocity of a discrete spherical particle in laminar flow?

   $$v_s = \frac{g(\rho_p - \rho_w)d^{2}}{18\mu}$$ where $d$ is particle diameter, $\rho_p$ and $\rho_w$ are particle and water densities, $\mu$ is dynamic viscosity. Valid for Reynolds number $Re < 1$.

5. Define hydraulic detention (residence) time for a basin and give its formula.

   It is the average time water remains in a tank: $$\theta = \frac{V}{Q}$$ where $V$ is tank volume and $Q$ is the volumetric flow rate.

6. In disinfection, what does the CT concept represent and how is it calculated?

   CT is the disinfectant concentration $C$ (mg/L) multiplied by contact time $T$ (min): $$CT = C \times T$$ A required CT value (from regulatory tables) ensures a target log inactivation of pathogens such as Giardia or viruses.

7. What is breakpoint chlorination and what occurs at the breakpoint?

   As chlorine is added to water containing ammonia, it forms chloramines (combined chlorine), which then are oxidized/destroyed. At the breakpoint, all ammonia and chloramines are consumed and further chlorine addition produces free available chlorine residual ($\ce{HOCl}$/$\ce{OCl-}$).

8. Give the hypochlorous acid dissociation equilibrium and explain why disinfection is more effective at low pH.

   $$\ce{HOCl <=> H+ + OCl-}, \quad pK_a \approx 7.5$$ $\ce{HOCl}$ is a far stronger disinfectant than $\ce{OCl-}$. At lower pH the equilibrium shifts toward $\ce{HOCl}$, increasing disinfection efficiency.

9. What is the langelier saturation index (LSI) and what do positive vs negative values indicate?

   $$LSI = pH - pH_s$$ where $pH_s$ is the pH at calcium carbonate saturation. $LSI > 0$: water is scale-forming (supersaturated, $\ce{CaCO3}$ deposits). $LSI < 0$: water is corrosive (undersaturated). $LSI = 0$: chemically stable.

10. In lime-soda ash softening, which chemicals remove carbonate (temporary) and noncarbonate (permanent) hardness?

    Lime $\ce{Ca(OH)2}$ removes carbonate hardness by precipitating $\ce{CaCO3}$ and $\ce{Mg(OH)2}$. Soda ash $\ce{Na2CO3}$ is added to remove noncarbonate hardness by supplying carbonate to precipitate $\ce{CaCO3}$.

11. How is total hardness conventionally expressed, and what is the conversion of an ion concentration to that basis?

    Hardness is expressed as $\ce{CaCO3}$ equivalent (mg/L as $\ce{CaCO3}$). Convert each multivalent cation: $$\text{mg/L as }\ce{CaCO3} = (\text{mg/L of ion}) \times \frac{50}{\text{equivalent weight of ion}}$$ where 50 is the equivalent weight of $\ce{CaCO3}$.

12. Classify water hardness ranges (as $\ce{CaCO3}$): soft, moderately hard, hard, very hard.

    Soft: $0\text{–}75$ mg/L; Moderately hard: $75\text{–}150$ mg/L; Hard: $150\text{–}300$ mg/L; Very hard: $> 300$ mg/L (all as $\ce{CaCO3}$).

13. Define BOD and give the first-order equation for BOD exerted over time.

    Biochemical Oxygen Demand is the oxygen consumed by microbes degrading organic matter. $$BOD_t = L_0\left(1 - e^{-k_d t}\right)$$ where $L_0$ is the ultimate BOD, $k_d$ the deoxygenation rate constant (base $e$), and $t$ time.

14. What is the difference between $BOD_5$, ultimate BOD ($L_0$/$BOD_u$), and COD?

    $BOD_5$ is oxygen demand over 5 days. Ultimate BOD ($L_0$) is the total demand to fully oxidize biodegradable organics ($t \to \infty$). COD is the oxygen equivalent of organics oxidized by a strong chemical oxidant; $COD \geq BOD_u \geq BOD_5$ because COD also oxidizes non-biodegradable matter.

15. Convert a base-10 BOD rate constant $k$ to the natural-log (base $e$) rate constant $k_d$.

    $$k_d = k \times \ln(10) = 2.303\,k$$ Used to switch between $BOD_t = L_0(1 - 10^{-kt})$ and $BOD_t = L_0(1 - e^{-k_d t})$.

16. Define solids retention time (SRT / mean cell residence time) in the activated sludge process.

    $$\theta_c = \frac{V X}{Q_w X_w + Q_e X_e}$$ where $VX$ is mass of MLSS in the aeration tank, $Q_w X_w$ is solids wasted, and $Q_e X_e$ is solids lost in the effluent. It is the average time biomass stays in the system.

17. What is the food-to-microorganism (F/M) ratio in activated sludge and its formula?

    $$\frac{F}{M} = \frac{Q \cdot S_0}{V \cdot X}$$ where $Q$ is influent flow, $S_0$ influent BOD, $V$ aeration tank volume, and $X$ the MLVSS concentration. It indicates loading rate (kg BOD per kg biomass per day).

18. Define the sludge volume index (SVI) and explain what high values indicate.

    $$SVI = \frac{(\text{settled sludge volume, mL/L after 30 min}) \times 1000}{\text{MLSS, mg/L}}$$ Units mL/g. $SVI < 100$ indicates good settling; $SVI > 150$ indicates poor settling/bulking sludge (often filamentous bacteria).

19. List the conventional stages of wastewater treatment (preliminary through tertiary) and their main targets.

    Preliminary: screening and grit removal. Primary: sedimentation of settleable solids (removes ~30% BOD, 60% TSS). Secondary: biological removal of dissolved/colloidal organics (BOD). Tertiary/advanced: nutrient (N, P) removal, filtration, and disinfection.

20. What are nitrification and denitrification, including the overall reactions?

    Nitrification (aerobic, autotrophic) oxidizes ammonia to nitrate: $$\ce{NH4+ + 2O2 -> NO3- + 2H+ + H2O}$$ Denitrification (anoxic, heterotrophic) reduces nitrate to nitrogen gas: $$\ce{2NO3- + organic C -> N2 ^ + CO2 + H2O + OH-}$$

21. Name the two phases of anaerobic digestion and the principal end product gas.

    Phase 1: acidogenesis/acetogenesis (acid-forming bacteria convert organics to volatile fatty acids). Phase 2: methanogenesis (methanogens convert acetate/$\ce{H2}$ to gas). Biogas is roughly $60\text{–}70\%$ $\ce{CH4}$ and $30\text{–}40\%$ $\ce{CO2}$.

22. Write the Hazen–Williams equation for head loss in a pressurized pipe (US units).

    $$h_f = \frac{10.44\, L\, Q^{1.85}}{C^{1.85}\, D^{4.87}}$$ where $h_f$ is head loss (ft), $L$ pipe length (ft), $Q$ flow (gpm), $C$ the Hazen–Williams roughness coefficient, and $D$ diameter (in).

23. Write the Darcy–Weisbach equation for friction head loss in a pipe.

    $$h_f = f\frac{L}{D}\frac{v^{2}}{2g}$$ where $f$ is the Darcy friction factor, $L$ length, $D$ diameter, $v$ mean velocity, and $g$ gravitational acceleration.

24. State Manning's equation for open-channel (gravity sewer) flow in US units.

    $$v = \frac{1.49}{n}R^{2/3}S^{1/2}$$ where $v$ is velocity (ft/s), $n$ Manning's roughness, $R$ the hydraulic radius (area/wetted perimeter), and $S$ the channel slope. Flow $Q = vA$.

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