CIVL 270: Introduction to
Environmental Engineering
Lecture 7:
Human Population and Growth
Dr. Ashraf Aly Hassan
Department of Civil and Environmental Engineering
Early Human History
• During the earliest parts of human history, our
population survived as hunter‐gatherers.
• The population during this time was low;
estimated to be in the thousands.
– Like other species,
population size was
limited by
environmental
resistance factors, such
as competition for food
and water, predators,
and disease.
2
• At some point, estimated to be about 130,000
years ago, Homo sapiens migrated out of
Africa into what would become the fertile
crescent.
3
• The fertile crescent, as a “bridge”
between Africa and Eurasia, had
an unusually high amount of
biodiversity.
• The eight “founder crops,”
including wild ancestors to
modern flax, wheat, barley,
and lentils, grew here.
• The ancestor species of
four out of the five modern
domesticated livestock animals
were native to here.
Founder crops (flax, three cereals and
four pulses)
4
• The presence of two major river systems
also stimulated the invention of irrigation.
• This period is known as
the Agricultural Revolution
and marked the first point
where humans moved from
a nomadic lifestyle to
settling in towns and
villages.
– Instead of hunting and gathering, humans
began growing and raising their own food
supply.
5
• Agriculture gave humans a greater degree of
control over their food supply. As a result, the
population began to grow.
6
The Middle Ages
• The human population grew at a steady rate,
reaching about 800 million by 1800 A.D.
• Some density‐dependent limiting factors were
still in place.
– Famines
•
•
•
•
Western Europe, 400‐800 A.D.
Mayan Civilization, 800‐1000 A.D.
Little Ice Age, 17th century
Great Potato Famine (Ireland), 1845‐1847
– Disease
• Malaria (10,000 B.C.‐present), cause of about half of all
human deaths
• Black Plague (14th century), Eliminated 1/3 of Europe’s
population.
7
The Industrial Revolution
• The industrial revolution began a multitude of new
technologies and innovations.
–
–
–
–
–
Electricity
The steam engine
Water treatment
Antibiotics
Vaccines
• The overall impact was a massive drop in infant
mortality – the death rate in newborns.
• This led to an increase in overall average life
expectancy.
– Pre‐industrial life expectancy in Britain was 25‐40 years.
– Current life expectancy worldwide is 67 years.
8
• Industrialized farming, water treatment, and
modern medicine removed many density‐
dependent limiting factors.
• The human population began to grow
exponentially.
9
HUMAN DEMOGRAPHY
• Demographics
populations.
is
the
study
of
human
– Includes comparing statistics such as births,
deaths, gender, race, and economic status.
• Developing countries have populations that
tend to be poorer, younger, and are growing
much more rapidly.
• Developed countries are wealthy, old, and
tend to have decreasing population sizes.
10
– Developing countries contain 80% of the world’s
population, and will account for 90% of its projected
growth.
11
• Comparing developed and developing countries
requires the use of these demographic variables:
– Life expectancy, or how long an average newborn will
live in a society.
• Most affected by infant mortality rate.
– Total fertility rate, the average number of children a
woman will have in her lifetime.
• A fertility rate above replacement level, 2.1, will generally
result in a growing population.
• Below replacement level results in a shrinking population.
– Gross domestic product (GDP) per capita is a
measurement of standard of living.
• Total value of all goods and services produced in a country
per person.
12
• Life expectancy (and infant mortality) are highly
correlated with GDP, up to about $4000/year.
13
Migration
• The movement of individuals between areas can
have a major impact on population change.
• Emigration is when people move out of an area.
– More likely to occur in developing countries.
• Immigration is when
people move into an
area.
– More likely to occur
in developed countries.
14
• In some developed countries, immigration
offsets or delays the normal population
decline.
• The United States total fertility rate in 2011
was 1.89, below replacement level.
– The overall immigration was over 11 million.
– The population growth rate was 0.7%.
• Japan had a fertility rate of 1.39 in 2011.
– The overall immigration was just over 200,000.
– Their population growth rate is ‐0.2%.
15
Objective:
Develop and use various mathematical models to
predict population.
Why?
• Population growth is needed for design
purposes.
• Population growth plays a role in economic
growth.
• We cannot expect to make accurate predictions
of the future! What if scenarios!
Population Growth Models
1. Exponential Growth
•Discrete growth
•Continuous compounding
2. Logistic Growth
3. Using Life Tables
Can you please solve the
population doubling time (td)?
Example 3.3 (page 91)
It took about 300 years for the world’s population to
increase from 0.5 billion to 4 billion. If we assume
exponential growth at a constant rate over that period
of time, what would that growth rate be? Do this
example first with a calculator and then with the rule of
thumb.
𝑵𝒕
𝑵𝒐 𝒆𝒓𝒕
𝑵𝒕 /𝑵𝒐
𝒆𝒓𝒕 => ln(𝑵𝒕 /𝑵𝒐 ) = rt => r = (1/t) ln (𝑵𝒕 /𝑵𝒐 )
r = (1/t) ln (𝑵𝒕 /𝑵𝒐 ) = (1/300) ln(4/0.5) = 0.00693 = 0.693% = 0.7%
Rule of Thumb: Consider three doubling times (0.5 to 1 billion), (1 to 2
billion) and (2 to 4 billion) in three consecutive 100 years.
Doubling time, Td = 70/r%;
r% = 70/100 = 0.7%
Definition
• Crude Birth Rate, b (no. live births per 1000 in a
year)
• Total Fertility Rate, TFR (average children per
woman)
• Replacement Level Fertility (TFR at which 1 girl
per 1 woman)
• Crude Death Rate, d (no. deaths per 1000 in a
year)
• Infant Mortality Rate (no. of infant deaths (less
than 1 year) per 1000 live births in a year)
• Rate of natural increase, r (r = b – d)
Population Pyramids or
Population Age Structure
• When studying the demographics of a single
country, two of the most important factors to
examine are gender and age distribution.
• These variables are graphed as population
pyramids, and can provide valuable insight
into a country.
27
• What is the overall shape of the graph?
• Is there a dominant age group or groups?
• What proportion of the 0‐4 age group survives into the
elderly (60+) age groups?
• Are the male and female sides roughly equal?
28
Demographic Transition Model
• Countries will typically pass through a series
of stages as they industrialize and transition
from developing to developed countries.
• During the pre‐industrial stage, food
shortages, malnutrition, poor sanitation, and
lack of access to modern medicine keep death
rates high.
– All regions of the world were in this stage up until
the industrial revolution.
29
Demographic Transition
30
• During the early transition stage, access to food
and medicine improve, leading to a rapid drop in
death rates.
– Birth rates remain high, as family size is tied to cultural
norms and religious beliefs.
• Population size begins to increase exponentially.
31
• During the late transition stage, efforts are made to
reduce birth rate.
– Birth control and family planning education gain greater
acceptance.
– Women play a greater role in family planning.
• The population continues to increase, but more slowly.
32
• During the industrial stage, birth rates have
fallen back into balance with death rates.
– Total fertility rate is close to replacement level.
• The population stabilizes.
33
• During the post‐industrial stage, birth rates
continue to fall due to antinatalist pressures
– Total fertility rate is below replacement level.
• The population size decreases.
34
Population Growth : Opposing Factors
• Pronatalist pressures increase the likeliness of individuals
within a population to have more children.
–
–
–
–
–
Source of pleasure, pride, comfort.
Source of support for elderly parents.
Aid in supporting family income.
Counteracting high child mortality rates.
Social status – importance of having a son.
• Most antinatalist pressures involve women.
– Higher education and personal freedom.
– More opportunities to earn a salary.
– Higher socioeconomic status.
35
CIVL 270: Introduction to Environmental
Engineering
Lecture 8: Water Resources, Pollution
and Treatment ‐ 1
Dr. Ashraf Aly Hassan
Department of Civil and Environmental Engineering
“When the well is dry, we learn the worth of water.”
‐ Benjamin Franklin
2
Hydrologic Cycle
• The hydrologic cycle describes the mechanisms by
which water moves throughout the Earth.
– Heat from the sun
causes water to
evaporate from
rivers, lakes,
oceans, or the soil.
– Plant roots extract
water from the soil
and release some of
it into the
atmosphere through
their leaves, a process
called transpiration.
Barron Gorge National Park, Cairns, Australia.
3
• As the evaporated water moves up into the
atmosphere, it loses heat and condenses into
clouds.
• The water then returns to the Earth as
precipitation; rain, snow, or ice.
– Some of that water will form
runoff, moving towards lower
elevations and collecting
into another body of surface
water.
– The rest of the water soaks
into the soil, a process called
infiltration.
4
• At any given time, only
about 3% of the world’s
water supply is
freshwater. The rest is
in the oceans (saline
water).
• The majority of
freshwater is frozen
(79%) within land ice
(glaciers).
• Another 20% is
underground
(groundwater).
• Only 1% of freshwater is
available at the surface
(surface water).
5
Hydrologic Cycle
Water Usage
• Water use is measured in two ways:
– Water withdrawal measures the total amount
diverted or withdrawn from a source.
• Example: Coolant water withdrawn by a power plant,
then returned to the river.
– Water consumption measures water permanently
removed from a source.
• Example: Water is sprayed on crops for irrigation, then
evaporates or transpires into the atmosphere.
8
• Agriculture makes up the majority of both water
withdrawal and consumption.
10
Countries experiencing water scarcity tend to be in
highly populated and dry regions.
Water Supply in UAE
•
•
•
•
•
Average rainfall is about 100 mm/yr.
No reliable surface water resources.
Low groundwater recharge rate.
Very high evaporation rate (2000‐3000 mm/yr).
UAE current water demand is 7 times its renewable
water resources.
• Second largest producer of desalinated water in GCC.
(500 Mm3/year)
• The average water consumption in the UAE is about
570 Liter/capita/day.
• Highest per capita domestic consumption rate within
GCC which reaches 300 Liter/cap/day.
Water Pollution
• Thermal Pollution (p.190)
Causes a drop in the dissolved oxygen due to higher metabolic rate
and lower DO solubility at higher temperature.
• Solids/Salts (p.188)
•
•
•
All naturally occurring water has some amount of salt in it.
Could be suspended (causing turbidity) or dissolved (causing
salinity).
Total dissolved solids (TDS) in water is the sum of all cations and
anions present expressed in mg/L.
• Heavy Metals (p.190)
• Cations with specific gravity >4 or 5.
• Examples: Hg, Pb, Cd, Cr, Co, Fe, Mn, Zn, etc.
• Most heavy metals are toxic at low levels.
• Some are useful as nutrients at low level but toxic
at high level.
•Oxygen Demanding Waste (p.185)
• DO is a measure of water quality
• Substance that oxidized (by bacteria) in water (most
organics).
• Cause a drop in the dissolved oxygen (threat to
aquatic life)
• Several measures of Oxygen demand
• COD: chemical oxygen demand
• BOD: biochemical oxygen demand
Nutrients (p.186)
• Include N, P, S, C, Ca, K, Fe, etc.
• They are pollutants if allow algal growth (drop of DO)
Pesticides (p.191)
• Chemicals that kill organisms that humans consider
undesirable
• Classification based on intended use: insecticides,
herbicides, fungicides, etc.
• Classification based on chemical structure: organochloroines
(ex. DDT), organophosphate, and carbamates.
Volatile Organic Compounds (VOCs) (p.193)
• Chlorinated compound, perchloroethylene (PCE),
tetrachloroethylene (TCE), dichloroethylene (DCE), vinyl
chloride, trichloroacetic acid (TCA)
• Aromatic hydrocarbons, BTEX
Biochemical Oxygen Demand (BOD) (p.199)
BOD: The amount of O2 needed by the microorganisms
to oxidize organic wastes. Measured in mg/L of waste
water.
BOD5: Amount of oxygen consumed in first 5 days per
liter of solution.
Water Pollution
• Water pollution is the addition of any
substance that degrades, or lowers the quality
of the water for living organisms.
27
• Excess nutrient
pollution causes
eutrophication,
or an overgrowth
of algae.
28
• Algae blooms caused by eutrophication block
sunlight from reaching underwater plants.
– As the plants die, the dissolved oxygen (DO) levels
of the water decline.
– A decline in dissolved oxygen causes the suffocation
of large organisms, like fish.
A boat moving through
a 2011 algae bloom in
Lake Erie.
Photo by Peter Essick,
National Geographic.
29
• Dissolved oxygen levels can also drop with the
amount of oxygen consumed by bacterial
decomposers in the water, called biological oxygen
demand (BOD), suddenly increases.
– This tends to happen from an influx of food such as raw
sewage or dead algae.
30
Types of Water Pollution
• Fertilizer runoff is an example of nonpoint
source pollution, because it does not come
from a single discharge location.
• Raw sewage discharged
from a large pipe would
be an example of point
source pollution.
31
• Nonpoint sources of pollution can enter a body
of water from anywhere across its watershed –
the area of land over which all rain and other
water sources drain into it.
The Mississippi River watershed.
Source: nature‐education.org
32
Ocean Pollution
• The majority of pollution in the ocean falls
into two categories:
– Oil
– Petroleum‐based plastics
33
• The biggest sources of oil in the ocean include:
– Natural seeps from oil deposits at the ocean floor.
– Runoff from land, including leaking cars and improper
disposal of used motor oil.
• This is the largest source.
– Discharge from ships.
– Spills from offshore drilling.
– Spills from oil tanker accidents.
• Oil penetrates the fur
and feathers of animals,
destroying the natural
insulation.
– Oil also directly
damages the tissues
of fish and other
aquatic organisms.
34
Oil Spills
• Although oil spills from rigs and tanker ships
are not the biggest source of oil in the ocean,
they have the most severe effects in the
immediate area.
• One of the worst spills to ever affect North
America was the Exxon Valdez in 1989.
35
Deepwater Horizon
• The worst oil spill by volume occurred in 2010
when an oil rig in the Gulf of Mexico
experienced a blowout.
– The drilled well at the bottom of the sea gushed
nearly 5 million barrels of oil into the sea over a
period of four months.
36
Plastic
• A study by the Environmental Investigation
Agency revealed that whales in the ocean were
ingesting large amounts of plastic and fishing
gear.
• A gray whale stranded near Seattle was found to
have the following in its stomach:
–
–
–
–
Duct tape
Surgical gloves
Golf ball
More than 20 plastic bags
37
CIVL 270: Introduction to Environmental
Engineering
Lecture 9: Water Resources, Pollution and
Treatment ‐ 2
Dr. Ashraf Aly Hassan
Department of Civil and Environmental Engineering
1
Accessing Groundwater
• Groundwater is located in a region of soil called
the zone of saturation, where all of the spaces
between soil particles are filled with water.
– The top of this region is called the water table.
2
Objectives
•
•
•
•
•
•
What is groundwater?
Why is it important?
How fast groundwater moves?
How contaminants reach groundwater?
How contaminants move in groundwater?
What are the processes of water treatment?
3
• Aquifers are underground regions of soil or
porous rock that are saturated with water.
– If the aquifer is physically separated from the
groundwater, it is called a confined aquifer.
• Regions where the water can infiltrate the soil
and reach the aquifer are called recharge zones.
4
Aquifer Systems
• Confined aquifer: is an aquifer that is confined
between two confining layers (water kept
under pressure)
• Unconfined aquifer: is an aquifer in which the
water table forms the upper boundary; it is
also called water‐table aquifer
5
Porosity
The amount of water that can be
stored in a saturated aquifer
depends on the Porosity of the
soil and rock that makes up the
aquifer.
6
Porosity
7
Types of Porosity
• Primary ‐water in pores between grains.
• Secondary ‐groundwater in fractures,
voids
• Effective porosity: porosity available for
fluid flow, “connected pores”.
• Disconnected or “dead‐end” pores.
8
9
Specific Yield, Sy
• Storage term for unconfined aquifers
• Volume of water that can be drained from an
unconfined aquifer per unit area per unit
decline of water table is called specific yield
(effective porosity)
• Solve example 5.10 p.233
10
11
How groundwater moves ‐ Hydraulic Gradient
12
13
14
How groundwater moves ‐ Hydraulic
Conductivity, K
• At which a fluid is transmitted through a
porous material
• The most important groundwater
measurement!!
• Depends on the fluid density, viscosity,
and material permeability.
15
16
17
18
Heterogeneity and Anisotropy
Hydraulic Conductivity (K)
of
The formation is
• Homogeneous: when K is
independent of position
K(x,y,z) = constant
• Isotropic: when K is independent of
direction Kx=Ky=Kz=constant
19
Heterogeneity and Anisotropy of
Hydraulic Conductivity
20
How fast does groundwater flow?
• Depends on hydraulic conductivity (K),
• Depends on available potential energy to drive
the fluid flow,
• Movement from high to low energy.
21
Overconsumption
• Excessive water withdrawal can cause a
lowering of the water table, called a cone of
depression.
– This may cause nearby, shallower wells to run dry.
22
• Wells located near the ocean can experience
saltwater intrusion as the ocean water mixes
with the groundwater.
23
• Excessive groundwater
consumption can also
lead to subsidence, a
compression and
sinking of the zone of
saturation.
– The San Joaquin valley
in California has
experienced
subsidence of up to 28
feet.
24
25
Water and Wastewater Treatment Processes
26
27
28
29
Water Treatment Processes
30
Chemical Coagulation‐Flocculation
Removes suspended particulate and colloidal
substances from water, including microorganisms.
Coagulation:
• Typically, add alum (aluminum sulfate) or ferric
chloride or sulfate to the water with rapid mixing and
controlled pH conditions
• Insoluble aluminum or ferric hydroxide and aluminum
or iron hydroxo complexes form
• These complexes entrap and adsorb suspended
particulate and colloidal material.
32
Coagulation‐Flocculation, Continued
Flocculation:
• Slow mixing (flocculation) that provides for a period
of time to promote the aggregation and growth of
the insoluble particles (flocs).
• The particles collide, stick together and grow larger
• The resulting large floc particles are subsequently
removed by gravity sedimentation (or direct
filtration)
• Smaller floc particles are too small to settle and are
removed by filtration
Granular Media Filtration
• Used to remove suspended particles (turbidity) incl.
microbes.
• Historically, two types of granular media filters:
Slow sand filters: uniform bed of sand;
– low flow rate <0.1 GPM/ft2 [gallon per minute per ft2]
– biological process: 1‐2 cm “slime” layer (schmutzdecke)
Rapid sand filters: 1, 2 or 3 layers of sand/other media;
– >1 GPM/ft2
– physical‐chemical process; depth filtration
Water Softening
• ”Hard" Water: contains excessive amounts of calcium
and magnesium ions
– iron and manganese can also contribute to hardness.
• Hardness ions are removed by adding lime (CaO) and
sometimes soda ash (Na2CO3) to precipitate them as
carbonates, hydroxides and oxides.
• This process, called softening, is basically a type of
coagulation‐flocculation process.
37
Disinfection of Microbes
Disinfection is the essential barrier to prevention and control of
waterborne microbial transmission and waterborne disease.
• Free chlorine: HOCl (hypochlorous) acid and OCl‐ (hypochlorite
ion)
• Ozone, O3 , strong oxidant; provides no residual (too volatile and
reactive)
• Chlorine dioxide, ClO2,, string oxidant but not very stable
residual
‐ Concerns due to health risks of chemical disinfectants and
their by‐products (DBPs), especially free chlorine and its
DBPs
• UV radiation
39
40
Wastewater Treatment
• Human sewage is a waste product that is
unavoidable, but it can be treated to minimize
environmental impacts.
• Screening removes any trash or large objects
that may have entered the sewage stream.
41
Wastewater Treatment
• Primary treatment holds the sewage in a large
containment vessel.
– Heavy solids that sink to the bottom are removed as
sludge.
– May also be aerated to remove as much of the smell
as possible.
• The sludge that is
leftover from these
treatments is
decomposed with
bacteria or
composted.
42
• Secondary treatment adds bacteria
decompose the dissolved organic matter.
to
– The bacteria must then be killed once the process is
complete. This is usually done with chlorine.
• Tertiary treatment is any additional treatment,
such as the removal of nitrates and phosphates.
43
Sewer Overflow
• Sewage treatment plants have a limited
amount of water that can be processed at any
given time.
• If a flood, snow melt, or other excess water
event occurs, raw sewage may be dumped
directly into the nearby water body.
44
45
46
CIVL 270: Introduction to Environmental
Engineering
Lecture 10: Solid Waste Management
Dr. Ashraf Aly Hassan
Department of Civil and Environmental Engineering
Municipal solid waste (MSW), commonly known as trash or
garbage (US), refuse or rubbish (UK) is a waste type consisting
of everyday items that are discarded by the public.
Consists of everyday items we use and then throw away, such as
product packaging, grass clippings, furniture, clothing, bottles,
food scraps, newspapers, appliances, paint, and batteries. This
comes from our homes, schools, hospitals, and businesses.
"Garbage" can also refer specifically to food waste, as in a
garbage disposal; the two are sometimes collected separately.
Solid Waste cannot be eliminated, but can be
reduced through:
• Elimination of excess packaging and
disposable items
• Reduce, Reuse and Recycle of materials (3Rs)
• Use waste materials as an energy source
Read Pollution Prevention Act of 1990… p. 555
Objectives
• Articulate the role of civil/environmental
engineers in protecting public health from the
hazard of generated solid waste
• Determine the size of a sanitary landfill.
• Determine the size of vehicles collecting
municipal solid waste.
Municipal Solid Waste (MSW)
•
•
•
•
•
•
Paper Wastes
Yard Wastes
Glasses
Metal
Plastic
Food Wastes
The UAE has one of the world's highest levels
of domestic waste. Per capita household
waste has reached an average annual 730
kilos in Abu Dhabi and 725 kilos in Dubai. In
the US the average is 710 kilos, in Australia 690
kilos and in the UK 300 kilos. Additional refuse
comes from street litter, gardens and from the
waste dumped in the sea and on beaches. This
has imposed a heavy burden on the
municipalities. The problem is only partly
solved by converting organic waste into
agricultural fertilizer. Some waste such as
paper, glass and tin cans is being recycled
Which company in Al Ain works in solid waste
management?:
http://lavajet.ae/Services.aspx
Sources and Types of Solid Wastes
Source
Typical facilities,
activities, locations where
wastes are generated
Types of solid wastes
Residential
Single and multifamily
dwellings
Food wastes, paper, cardboard, plastics,
textiles, leather, yard wastes, wood,
glass, metals, ashes, special wastes
(e.g., bulky items, consumer
electronics, white goods, batteries, oil,
tires), and household hazardous wastes
Industrial
Light and heavy
manufacturing, fabrication,
construction sites, power
and chemical plants
Industrial process waste, scrap
materials, etc. Non - industrial waste
including food wastes, construction and
demolition wastes, rubbish, ashes ,
hazardous wastes, ashes, special wastes
Sources and Types of Solid Wastes
Source
Typical facilities,
activities, locations where
wastes are generated
Types of solid wastes
Commercial
Stores, hotels, restaurants,
markets, office buildings,
etc.
Paper, cardboard, plastics, wood, food
wastes, glass, metals, special wastes,
hazardous wastes
Institutional
Schools, hospitals, prisons,
government centers
Same as commercial
Construction and Demolition New construction sites,
Wood, steel, concrete, dirt, etc.
road repair, renovation
sites, demolition of
buildings, broken pavement
Sources and Types of Solid Wastes
Typical
activities,
Types(Cont’d)
of solid wastes
TableSource
1: Sources and Types
offacilities,
Solid Wastes
within a Community
locations where wastes are
generated
Municipal
Services (excluding
treatment facilities)
Street cleaning, landscaping,
parks, beaches, other
recreational areas, water and
wastewater treatment plants
Street sweepings; landscape and tree
trimmings; general wastes from parks,
beaches, and other recreational areas;
sludge
Agricultural
Field and row crops, orchards,
vineyards, dairies, feedlots,
farms, etc.
Spoiled food wastes, agricultural wastes,
rubbish, hazardous waste.
Nature of Municipal Solid Waste
• Organic (Combustible)
• Inorganic (non-combustible)
• Putrescible (putrescible solid waste contains organic matter capable
of being decomposed by microorganisms)
• Recyclable
• Hazardous
• Infectious
The residential and commercial portion makes up
about 50 to 75 percent of total MSW generated in a
community
 The actual percentage distribution will depend on
– The extent of construction and demolition
activities
– The extent of the municipal services provided
– The types of water and wastewater treatment
process that are used
Typical Physical Composition of Residential MSW
Composition
of Solid Waste
The percentage
distribution
values
components in MSW vary with
 Location
 Season
 Economic conditions
 Population
 Social behavior
 Climate
 Market for waste materials
 Other factor
for
the
Collection and Transfer of MSW (p. 636)
Please solve the Example 9.6
(Vehicle sizing), p 640
Landfills (p. 669)
Classifications of Landfills (three classes)
• Class I (secure): Hazardous waste
• Class II (monofills): particular type of waste
• Class III (sanitary): MSW landfills
• Landfills construction and operation
CIVL 270: Introduction to
Environmental Engineering
Lecture 11: Risk Assessment
Dr. Ashraf Aly Hassan
Department of Civil and Environmental Engineering
Objective
Develop the ability to calculate the risk associated
with the exposure to levels of contaminants and
establish acceptable exposure limits based on a pre‐
set risk limit.
Why? To be able to answer these questions
• How clean is clean?
• How can air and water quality standards be set?
• When do we terminate cleanup activities at a site?
• Achieving no risk would cost infinite amount of
money!
Equal Risk (one in a million risk) = 1/1000000 = 10‐6