Water use and pollution
Water Location
• Earth is the only planet known to contain
water. Past or present.
• Water = Life
• Water is a necessary substance for every life
process.
• Water controls where most people live.
• Water quantity is a constant in our world.
There is always the same amount, it just
changes locations.
Conservation of Mass
• We can not make new water.
• It changes from one form to
another or from one thing to
another.
Water Balance in the Hydrological Cycle
Water Location
• 99% of world’s water is in Oceans and Ice caps.
– Undrinkable
• .6% of the water is in the ground
– Some is drinkable, but hard to get and must be cleaned
• .4 % of the water is in lakes, streams, rivers, and
seas.
– Most is drinkable, but must be cleaned
Water: A Vital Resource
Water in Atmosphere
• There is always water in the atmosphere. One estimate of
the volume of water in the atmosphere at any one time is
about 3,100 mi3 or 12,900 km3. That may sound like a lot,
but it is only about 0.001 % of the total Earth's water
volume of about 332,500,000 mi3 (1,385,000,000 km3).
• If all of the water in the atmosphere rained down at once, it
would only cover the ground to a depth of 2.5 centimeters,
about 1 inch.
The Water Cycle
Source of Energy
Once
again, we
see that the
sun is the
main
source to
make the
water cycle
happen.
Condensation
Water vapor (gas)
from evaporation
starts to stick
together to make
larger water
drops. This forms
clouds.
Condensation is
the opposite of
evaporation.
Global Precipitation
Transpiration
Ground Water
• This is water found in porous
rock layers and in soils below
the earth’s surface.
• Ground water close to the
surface is important to plan
life. Plants use the water, then
release it back into the
atmosphere during
transpiration.
• When ground water is used, it
takes time to refill.
well
Soil
Unsaturated Rock
Water Table
Saturated Rock
(Aquifer)
Capillary
Water
Saturated
Water
Unconfined Aquifer Recharge Area
Evaporation and transpiration
Precipitation
Confined
Recharge
Area
Evaporation
Runoff
Flowing
artesian
well
Infiltration
Water
table
Recharge
Unconfined
Aquifer
Infiltration
Stream Well
requiring a
pump
Lake
Fig. 14-3, p. 308
WITHDRAWING GROUNDWATER TO
INCREASE SUPPLIES
• Most aquifers are renewable resources unless
water is removed faster than it is replenished or if
they are contaminated.
• Groundwater depletion is a growing problem
mostly from irrigation.
– At least one-fourth of the farms in India are being
irrigated from overpumped aquifers.
Groundwater Depletion:
A Growing Problem
 Areas of
greatest aquifer
depletion from
groundwater
overdraft in the
continental U.S.
Figure 14-8
Aquifer Exploitation
• Ground water use
exceeds aquifer recharge
• Many remaining aquifers
are heavily polluted
• The Ogallala, the world’s
largest aquifer, is most of
the purple area in the
center
Groundwater Pumping in Saudi
Arabia (1986 – 2004)
• Irrigation systems from the nonrenewable
aquifer appear as green dots. Brown dots are
wells that have gone dry.
Figure 14-9
Other Effects of Groundwater
Overpumping
• Groundwater
overpumping can
cause land to sink,
and contaminate
freshwater aquifers
near coastal areas
with saltwater.
Figure 14-11
Watershed
• This is the surrounding land that drains rain
and snow into a body of water.
• This important because certain areas get their
water from these watershed areas. Anything
that happens in that area efects their water.
Trinity River Watershed
Colorado River Basin
• These are dams &
reservoirs that feed from
the Colorado River all
the way to San Diego,
LA, Palm Springs,
Phoenix & Mexico. So
far has worked because
they haven’t withdrawn
their full allocations.
Human Impacts on the Water Cycle
• Changing the surface of the Earth
• Climate change - Floods, droughts
• Atmospheric pollution
• Overdrawing water supplies
• Water Diversions – dikes, levees, dams,
aqueducts
• Water Pollution
• Impermeable surfaces
Human Impacts on the Hydrological
Cycle
Regional Usage of Water
Trends in Population and Freshwater
Withdrawals, U.S.
Consequences of Overdrawing
Groundwater
• Falling water tables
• Diminishing surface
waters (wetlands)
• Land subsidence
• Saltwater intrusion
Case Study:
• 17 western states by
2025 could face intense
conflict over scarce
water needed for urban
growth, irrigation,
recreation and wildlife.
Figure 14-5
Stress on the World’s River Basins
• About 41% of the world’s population lives in river
basins that do not have enough freshwater.
Water Pollution
• What is pollution?
• Why does water get so polluted so easily?
• What characteristic makes it such a good
dissolver (solvent)?
Water
• Water is a covalent compound (
share electrons).
• The bond between Hydrogen and
Oxygen is a polar covalent bond.
• The oxygen is partially negative.
• The hydrogen is partially positive.
• WHY?! Oxygen is more
electronegative than Hydrogen!
The process of dissolving
• STEP 1: Solvent is attracted
to the solute.
• STEP 2: Solvent particles
surround the solute particles
and pull them into solution.
• Why are they attracted to
each other???
• Because they are polar.
Opposites attract.
Groundwater Moves – Usually Slowly
Water Monitoring
The process of testing water samples.
Drinking Water Standards
Gives the “acceptable”
level of the pollutant in
drinking water
• How is water quality measured?
• The presence of contaminants and the characteristics
of water are used to indicate the quality of water.
These water quality indicators can be categorized as:
• Biological: bacteria, algae
• Physical: temperature, turbidity and clarity, color,
salinity, suspended solids, dissolved solids
• Chemical: pH, dissolved oxygen, biological oxygen
demand, nutrients (including nitrogen and
phosphorus), organic and inorganic compounds
(including toxicants)
• Aesthetic: odors, taints, color, floating matter
• Radioactive: alpha, beta and gamma radiation
emitters.
EPA – Clean Water Act
• Growing public awareness and concern for controlling water
pollution led to enactment of the Clean Water Act. The Act
established the basic structure for regulating discharges of
pollutants into the waters of the United States. It gave EPA the
authority to implement pollution control programs such as
setting wastewater standards for industry. The Clean Water Act
also continued requirements to set water quality standards for
all contaminants in surface waters. The Act 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. It also funded the construction of sewage treatment
plants under the construction grants program and recognized
the need for planning to address the critical problems posed by
nonpoint source pollution.
Using Laws to Protect Drinking Water
• While most developed countries have drinking
water quality standards and laws, most
developing countries do not.
• The U.S Safe Drinking Water Act requires the
EPA to establish national drinking water
standards (maximum contaminant levels) for
any pollutant that may have adverse effects
on human health.
Primary Standards
Secondary Standards
• health based
• enforced (public
systems)
• examples:
– coliform bacteria:
<1/100 ml
– nitrate: 45 mg/L
– PCE: 5 µg/L
– atrazine: 3 µg/L
– Arsenic 10 ppb
• cause taste, odor,
stains, etc.
• examples:
– iron, manganese, pH,
yellow, sour
Water Pollution Types
•
•
•
•
•
Pathogens
Organic wastes
Chemical
Sediments
Nutrients
Types of Pollutants
• Factors that determine the severity of a pollutant’s
effects: chemical nature, concentration, and
persistence.
• Pollutants are classified based on their persistence:
–
–
–
–
Degradable pollutants
Biodegradable pollutants
Slowly degradable pollutants
Nondegradable pollutants
Chemical Pollutants
• Inorganic chemicals
–Heavy metals, acids, road salts
• Organic chemicals
–Petroleum, pesticides, detergents
Organic Wastes
• Dissolved oxygen (DO) in the water is depleted
during decomposition of organic wastes.
• Water quality test
– Biochemical oxygen demand (BOD):
measure of the amount of organic material.
Pathogens Carried by Sewage
• Disease-causing agents (Table 17.1)
• Safety measures
– Purification of public water supply
– Sanitary collection/treatment of sewage
– Sanitary practices when processing food
Pollutants in Raw Wastewater
• 99.9% water to 0.1%
waste
• Pollutants in sewage are:
– Debris and grit
– Particulate organic
material
– Colloidal and dissolved
organic material
– Dissolved inorganic
material
• Sewer pic
Water Quality
•
•
•
•
pH – about 6-7
DO – Oxygen means healthy water
Dissolved chemical concentration
Clarity
• Test chemically or use indicator species
Using Laws to Protect Drinking Water
• The U.N. estimates that 5.6 million Americans drink
water that does not meet EPA standards.
• 1 in 5 Americans drinks water from a treatment
plant that violated one or more safety standard.
• Industry pressures to weaken the Safe Drinking Act:
– Eliminate national tests and public notification of
violations.
– Allow rights to pollute if provider cannot afford to
comply.
What is allowed and how much?
Where do they come from?
Water Pollution: Point and Nonpoint
Sources
How do we make this drinkable? This
isn’t chocolate milk.
Indicator
species
Fig. 21-4, p. 497
Controlling Nonpoint Sources
• Difficult to address runoff pollutants
– Urban
– Agricultural fields
– Deforested woodlands
– Overgrazed pastures
Agriculture
Coliform bacteria
Fertilizer Pesticides
Erosion
New Housing Development
coliform bacteria
erosion
nitrate
sediment
quantity
Organic Chemicals Industrial Activity
Thermal Pollution
Heavy Metals
Deep or Surface Mining
low pH
metals
sulfate
quantity
Sediments
diversions
Gas or Oil Wells
metals
brine water
hydrocarbons
quantity
Acid Mine Drainage
Water treatment plants
Removing Pollutants from Sewage:
Primary Treatment: Physical Process – screens and
grit tanks to remove large floating objects
Secondary Treatment: Biological Process – anaerobic
bacteria to remove biodegradable waste
Advanced or tertiary sewage treatment:
Uses series of chemical and physical processes to
remove specific pollutants left (especially nitrates
and phosphates). Water is chlorinated to remove
coloration and to kill disease-carrying bacteria and
some viruses (disinfect).
Effluent
Municipal Water Use
and Treatment
Dust Particles
Particles of dried sludge carry
viruses and harmful bacteria
that can be inhaled, infect cuts
or enter homes.
Odors
Odors may cause illness or
indicate presence of harmful gases.
BUFFER
ZONE
Sludge
Groundwater
Contamination
Harmful chemicals
and pathogens
may leach into
groundwater
and shallow wells.
Exposure
Children may walk or
play in fertilized fields.
Livestock Poisoning
Cows may die after grazing
on sludge-treated fields.
Surface Runoff
Harmful chemicals
and pathogens may
pollute nearby
streams,lakes, ponds,
and wetlands.
Fig. 21-17, p. 513
Reducing Water Pollution through
Sewage Treatment
• Natural and artificial wetlands and other
ecological systems can be used to treat sewage.(
Bioremediation)
– California created a 65 hectare wetland near
Humboldt Bay that acts as a natural wastewater
treatment plant for the town of 16,000 people.
• The project cost less than half of the estimated price of a
conventional treatment plant.
Affects of pollution on natural
water sources.
Effects of Plant Nutrients:
Too Much of a Good Thing
• Plant nutrients from a lake’s environment affect
the types and numbers of organisms it can
support.
– Oligotrophic (poorly nourished) lake: Usually newly
formed lake with small supply of plant nutrient
input.
– Mesotrophic – moderate levels
– Eutrophic (well nourished) lake: Over time,
sediment, organic material, and inorganic nutrients
wash into lakes causing excessive plant growth.
Natural and Cultural Eutrophication
• Natural eutrophication
– aquatic succession
– occurs over several hundreds of years
– Natural erosion / runoff
• Cultural eutrophication
– driven by human activities
– occurs rapidly
Effects of Plant Nutrients on Lakes:
Too Much of a Good Thing
• Plant nutrients from a lake’s environment affect
the types and numbers of organisms it can
support.
Figure 6-16
Eutrophic or Oligotrophic?
•
•
•
•
•
•
Low bacteria decomposition
Benthic plants
Warm water
High nutrient concentration
BOD
High sediments
Dead Zones
• The dead zone is caused by excess nitrogen and phosphorous that is
washed into the Gulf from the Mississippi River. These nutrients
ignite huge algae and phytoplankton blooms. As the blooms die,
they drop to the ocean floor and decompose, using up the oxygen of
the deeper water. The stratification of the water that occurs during
the summer in the Gulf prevents the deepest water from becoming
reoxygenated. As a direct result, oxygen levels fall below 2 parts per
million, a level that most marine life cannot survive, including all
commercial fish, crab and shrimp species. The dead zone is now one
of the largest hypoxic zones of water in the world.
Dead Zone due to Mississippi River
Dead Zone in the Gulf of Mexico
Man made disasters
• Man is destroying the world’s water supply by
dumping, spilling, or “accidentally” polluting
our water sources.
Exxon Valdez Spill
1989
Up to 750,000 barrels
Deep Water
Horizon
• The federal task force’s
estimate of the amount
of oil released stood at
4.9 million barrels. (42
gallons/barrel)
• Spewing something like
an Exxon Valdez spill in
Alaska every 4 days.
• The federal task force’s
estimate of the amount
of oil released stood at
4.9 million barrels.
– (42 gallons/barrel)