CE 020: Introduction to Civil and Environmental Engineering - Exam #3 Review Notes

Exam 3 Study Tips

• Review study guides, focusing on main topics and key memorization points.
• Take breaks during review.
• Pay attention to learning objectives; revisit areas where objectives haven't been met.
• Create flash cards for important glossary terms.
• Review in-class Jeopardy and practice independently.
• Review past exams and quizzes, paying attention to previously missed questions.
• Practice example, homework, quiz, and textbook problems.
• Rewatch the water treatment video to reinforce understanding of the processes.
• Familiarize yourself with the FE equation sheets.
• Exam #3 will be comprehensive, emphasizing new material since Exam #2 (chapters 6-8).
• Chapters 9-11 are potential bonus points and will not be on the exam.

Chapter 6: Environmental Risk

• Risk is a function of hazard and exposure.
• Hazard vs. toxicity distinction.
• Toxic Release Inventory (TRI).
• Three ways of human contact: ingestion, inhalation, skin/dermal.
• Hazardous waste and classification basis.
• Toxicity types: carcinogenic and non-carcinogenic.

6.1 Risk and the Engineer Objectives

• Define risk and strategies to minimize/eliminate it.
• Summarize hazard types.
• Know the difference between hazard, toxicity, and risk.

Risk Equation

• Risk = Hazard \times Exposure
• Hazard =
• Exposure

6.2 Risk Perception

• Distinguish between voluntary and involuntary risk.
• Risk perception vs actual hazards, examples (terrorist attack, plane crash, electrosmog, heat, cancer, car accident)

Chapter 6: Environmental Risk Continued

• Median Lethal Dose (LD50).
• Median Lethal Concentration (LC50).
• Acute vs. chronic toxicity.
• Susceptible populations and examples.
• Synergistic toxicity.

Fig_6-5

• Illustrates the relationship between the concentration of a test chemical and its effect or response (e.g., mortality).
• EC50 or LC50 is the concentration at which 50% of the population exhibits the effect.

6.3 Hazardous Waste and Toxic Chemicals

• Objectives:
  • Summarize hazard types and their impacts.
  • Difference between hazard, toxicity, and risk
  • Utilize the Toxic Release Inventory (TRI).

Exposure Pathways:

• Ingestion (eating and/or drinking).
• Inhalation (breathing).
• Dermal (skin) contact.

Toxicity vs. Hazard

• Toxicity: The ability of a substance to produce an adverse effect in a biologic system(s).
• Hazard: The potential that a substance will cause an adverse effect in a given situation or environment.

Toxicology: Toxicity VS. Hazard VS. Risk

• Toxicity: Degree to which a substance can harm an exposed organism.
• Hazard: Potential for a substance to cause harm (toxicity + dose).
• Risk: Measurement or estimate of hazard.

6.4 Ethics and Risk

• Objective:
  • Define susceptible populations in relation to risk assessment and the role of engineers in protecting them.

Susceptible Populations:

• Sensitive segments of a population (juvenile, elderly, ill, pregnant women, babies/embryonic).
• More susceptible to adverse effects from chemical exposure.

Chapter 6: Environmental Risk Continued

• Risk Assessment and four steps.
• Epidemiology.
• Dose.
• Potency factor/slope factor.
• No Observable Adverse Effect Level (NOAEL).
• Reference Dose (RfD).
• Reference Concentration (RfC).

6.3.2 Toxicity- Non-carcinogenic

• Different types of non-carcinogenic effects.
  • Less serious: Reversible, Not debilitating, Not life-threatening
  • More serious: Irreversible, Debilitating, Life-threatening

6.5 Risk Assessment Objectives

• Define the four components of a risk assessment.
• Distinguish between chemical concentration, exposure, and dose.
• Calculate the acceptable risk associated with exposure to a carcinogenic and noncarcinogenic chemical for various and multiple exposure pathways.

Risk Assessment Components (MEMORIZE)

• Hazard assessment
• Dose-response assessment
• Exposure assessment
• Risk characterization

Table / 6.11

• Explanation of Weight of Evidence Descriptors
  • Carcinogenic to humans
  • Likely to be carcinogenic to humans
  • Suggestive evidence of carcinogenic potential
  • Inadequate information to assess carcinogenic potential
  • Not likely to be carcinogenic to humans

Linear Dose-Response Curve

• Probability of contracting cancer (risk) vs. Dose (mg/kg-day).
• Slope factor A_x is slope factor with units of \frac{mg}{kg-day}

Dose-Response Curve

• Probability of adverse health effect (risk) vs. Dose (mg/kg-day)
• Reference dose (RfD)
• No observable adverse effect level (NOAEL)

6.5.2 Dose-Response Assessment

• Dose: the amount of a chemical received by a subject.
• Dose= \frac{mass \ of \ chemical}{body \ weight \times exposure \ time}
• Units-mg/(kg-day)
• Dose= \frac{c \times Q}{weight}
• C= concentration (mg/L)
• Q= “flow rate” into an organism (adults drink 2 L/day)
• Weight- kilograms

Table 6-12

• Components that go into an exposure assessment
  • Questions answered during the Exposure Assessment
    • What are the important sources of chemicals?
    • What are the pathways and routes of exposure?
    • What amount of the chemical are people exposed to?
    • How often are people exposed?
    • What segments of society are more at risk?

Table / 6.14

• On exam, know how to use
• Land Uses and Examples of Exposure Assessment Associated with Each Use
  • Residential
  • Industrial
  • Commercial

6.5.4 Risk Characterization

• Takes into account the other 3 steps
• Performed differently for carcinogens and non-carcinogens
• Acceptable level of risk: 1 chance in a million (10^{-6})
• Unacceptable risk: 1 in 1,000 (10^{-3})
• State and federal regulations: 10^{-4} – 10^{-6}
• Risk characterization used to determine allowable concentrations of a chemical in air, water, or soil for an acceptable risk

6.5.4 Risk Characterization

• Carcinogens
  • Risk= dose \times risk \ per \ unit \ dose= unitless
  • Dose= mg/(kg-day)
  • Risk/unit dose= unitless/dose= unitless/(mg/(kg-day)= kg-day/mg

Acceptable Concentration Equation:

• Acceptable concentration= acceptable riskBWAT / (SFIREF*ED)
• AT- average time (days)
• EF- Exposure Frequency (days/year)
• ED- Exposure Duration (years)
• BW- Body weight (kg)
• IR- Ingestion rate (e.g. 2L water/day)
• SF- Slope Factor (mg/kg-day)^{-1}
• Acceptable concentration= mg/L=ppm

Non-Carcinogens

• HQ-Hazard quotient- acceptable risk from exposure to a non carcinogenic chemical.
• HQ= \frac{average \ daily \ dose}{ RfD}
• HQs are less than or equal to 1
• HQ=1 → average daily dose = RfD (the safe dose)

Reference Dose (RfD)

• RfD- daily oral dose exposure to human that is likely without appreciable risk
• RfD= \frac{NOAEL}{UF}
• UF- uncertainty factor (10-1,000)
  • rats→humans
  • children

Acceptable Concentration Equation:

• Acceptable concentration= (HQRfDBW) / IR
• HQ- Hazard quotient (unitless)
• RfD- Reference dose (mg/kg-day)
• BW- Body weight (kg)
• IR- Ingestion rate (e.g. 2L water/day)

Environmental Justice

• Certain segments of society that are socially, economically disadvantaged may be burdened with a greater amount of environmental risk.

Waste Management Hierarchy

• Source reduction
• Recycling
• Treatment
• Disposal

Chapter 7 Water: Quantity and Quality

• Hydrology.
• Hydrologic cycle.
• Water resources engineering.
• Point and non-point source pollutants.
• Clean Water Act.
• National Pollutant Discharge Elimination System (NPDES).
• Total Maximum Daily Load (TMDL).

7.1 Introduction to Water Resources and Water Quality

• Objectives:
  • Describe the components of the hydrologic cycle
  • Distinguish between point and nonpoint sources of pollutants
  • Explain the major components of the Clean Water Act

The Hydrologic Cycle

• Units of water transfer are 10^{12} m^3/year

Point and Non-Point Sources of Pollution

• Point Sources: Wastewater treatment plant, Factory
• Nonpoint Sources: Suburban development, City streets, Rural homes, Cropland, Animal feedlot

Clean Water Act- 1972

• Formerly Federal Water Pollution Control Act 1948 with lots of amendments
• Established the basic structure for regulating pollutant discharges into the waters of the United States.
• Gave EPA the authority to implement pollution control programs such as setting wastewater standards for industry.
• Maintained existing requirements to set water quality standards for all contaminants in surface waters.
• Made it unlawful for any person to discharge any pollutant from a point source into navigable waters, unless a permit was obtained under its provisions.
• Funded the construction of sewage treatment plants under the construction grants program.
• Recognized the need for planning to address the critical problems posed by nonpoint source pollution.

Chapter 7: Water Quantity and Quality

• Unconfined and confined aquifers
• Watershed

7.2 Surface Water, Groundwater, Watersheds

• Objectives:
  • Understand the major components of groundwater systems
  • Delineate a watershed and estimate runoff

Aquifer

• Underground soil or rock through which groundwater travels

Confined and Unconfined Aquifers

• Unconfined aquifers: Water has infiltrated from the surface and saturated the subsurface material. A pump will be required to lift the water to the surface.
• Confined aquifers : Has a layer of rock or a confining layer of clay above and below it that are not very permeable to water. Natural pressure in the confined layer can thus exist may be enough to push water in a well to the surface.

Aquifers Diagram

• Illustrates various aquifer types (confined, unconfined, perched), water table, recharge area, and artesian well.

Groundwater Flow

• Shows groundwater flow in different geological formations, including sand and gravel aquifers and fractured bedrock.

Watersheds:

• Watershed- the land area that drains to a point of concern.
• Lakes and rivers have watersheds.
• Drainage due to gravity

Chapter 7: Water Quantity and Quality

• Rational Method
• Estimating pollutant loadings
• Water footprint
• Primary user of water in the world (agriculture)

Land Cover and Runoff

• Illustrates how different land covers (natural ground cover, suburban development, 35%-50% impervious surface, 75%-100% impervious surface) affect evapotranspiration, runoff, shallow infiltration, and deep infiltration.

7.2.3 The Rational Method

• Q = (cj) i Aj
• Q = peak run off flow rate (ft^3/s)
• Cj = particular runoff coefficient for a land use L dimensionless [0-1]
• i- rainfall intensity (in/h)
• Aj - area w/in the water Sheel (acres)

Table/7.2

• Typical Runoff Coefficients and Percent Impervious Area Values for Various Land Uses

Estimating Pollutant Loading

• L= \sum Ai C{e,i}
• L-annual loading of pollutant (mass/year)
• A_i- surface area of land use type i (acres)
• C_{e,i}- export coefficient for the pollutant for land use

Table/7.3

• Given on exam
• Typical Values for Pollutant Export Coefficients from Runoff (pounds/acre/year)

Chapter 7 Sections

• Sections covered: 7.4, 7.7
• Sections not covered in depth but glossary terms still fair game: 7.5, 7.6, 7.8-7.12

7.3 Water Availability

• Objective:
  • Identify the major quantities and sources of freshwater
  • Identify the major users of water and percent use

Water Distribution

• Total water on Earth:
  • 97% Saline water (oceans)
  • 3% Fresh water
• Fresh water:
  • 68.7% Icecaps and Glaciers
  • 30.1% Ground Water
  • 0.9% Other
  • 0.3% Surface Water

7.4 Water Usage

• Objectives:
  • Identify the major users of water and percent use
  • Empathize with the global population that live in areas not equally served by global water and sanitation

7.7.2 Oxygen Saturation

• DO{sat} = KH * P_{O2}
• DO{sat} = saturation DO concentration \frac{moles \ O2}{L}
  • Usually convert to \frac{mg \ O_2}{L} using molecular weight (32 g O2/mole)
• K_H = 1.36*10^{-3} \frac{moles}{L-atm} at \ 20\degree C (Henry’s Constant)
• P_{O2} = 0.21 \ atm

7.7.3 Oxygen Deficit

• D = DO{sat} - DO{act}
• D= Oxygen Deficit \frac{mg \ O_2}{L}
• DO{sat} = saturation DO concentration \frac{mg \ O2}{L}
• DO{act} = ambient or measured dissolved-oxygen concentration \frac{mg \ O2}{L}

7.7 River Water Quality

• Dissolved Oxygen

Chapter 8 Water Treatment

• Purpose of water treatment- provide potable water that is palatable
• 8.2 Characteristics of Untreated Water
• Physical characteristics
• Safe Drinking Water Act (SDWA)

Chapter 8 Objectives

• Understand the importance and purpose of water treatment
• List characteristics of untreated water
• Describe a standard water treatment process

8.1 Objectives

• Awareness of the United Nation’s (UN) Sustainable Development Goal (SDG) 6 and how it is related to water treatment

The Purpose of Water Treatment

• The Purpose of water treatment is to provide potable water that is palatable.
• Potable water- healthy for human consumption, free of harmful microorganisms and organic and inorganic compounds
• Palatable water- water that is aesthetically acceptable to drink (Free from turbidity, color, odor, and objectionable taste)
• Water that is palatable may not be safe
• Water that is not palatable may be safe.

8.2 Characteristics of Untreated Water

• Objectives
  • List the major contaminants in and characteristics in untreated water

Table / 8.2

• Concentration of Major Constituents Found in Water
  • Major inorganic constituents
  • Minor inorganic constituents
  • Naturally occurring organic compounds
  • Anthropogenic organic constituents
  • Living organisms

Table/8.3

• Physical Characteristics of Natural Water
  • Turbidity
  • Particles
  • Color
  • Taste and odor
  • Temperature

Water Treatment Plant Diagram

• Illustrates the steps involved in a conventional surface water treatment plant, including screening, coagulation, flocculation, sedimentation, filtration, and disinfection.

Determination of Settling Velocity of Particles Using Stokes' and Newton's Laws

• Stokes' law
  • Us = \frac{g(\rhop - \rho)d^2}{18 \mu}
  • g is the acceleration due to gravity (m/s^2); \rho_p is the density of the particle (kg/m^3); ; \rho is the density of the liquid (kg/m^3); d is the particle diameter (m); and μ is the dynamic viscosity of the liquid (N-s/m^2)
    • Applicable for spherical particles when the Reynolds number < 1 (laminar flow).
• Newton's law
  • Us = \sqrt{\frac{4g (\rhop - \rho)dp}{3Ca \rho}}
  • g is the acceleration due to gravity (m/s^2); \rho_p is the density of the particle (kg/m^3); \rho is the density of the liquid (kg/m^3); Ca is the drag coefficient.
    • Applicable for particles when the Reynolds number 1 (transition and turbulent flow).

ideal settling basin: plan view. Removal only depends on surface area.