Transcript Water pollution - Manhasset Schools

Chapter 21
Water Pollution
Chapter Overview Questions
 What
pollutes water, where do these
pollutants come from, and what effects do
they have?
 What are the major water pollution problems
in streams and lakes?
 What causes groundwater pollution, and how
can it be prevented?
 What are the major water pollution problems
affecting oceans?
Chapter Overview Questions (cont’d)
 How
can we prevent and reduce surface
water pollution?
 How safe is drinking water, and how can it be
made safer?
Core Case Study: Using Nature to
Purify Sewage
 Ecological
wastewater
purification by a living
machine.

Uses the sun and a series
of tanks containing plants,
snails, zooplankton,
crayfish, and fish (that
can be eaten or sold for
bait).
Figure 21-1
WATER POLLUTION: SOURCES,
TYPES, AND EFFECTS
 Water
pollution is any chemical, biological,
or physical change in water quality that has a
harmful effect on living organisms or makes
water unsuitable for desired uses.


Point source: specific location (drain pipes,
ditches, sewer lines).
Nonpoint source: cannot be traced to a single
site of discharge (atmospheric deposition,
agricultural / industrial / residential runoff)
Table 21-2, p. 495
Water Pollution Sources
Water Quality Testing
Determining
amount of specific
pollutants or
compounds in the
water to gauge
water safety
Major Water Pollutants
and Their Effects

A fecal coliform
bacteria test is used to
indicate the likely
presence of diseasecausing bacteria in
water.
 E. Coli bacteria
 Indicates animal waste
Figure 21-2
Fecal Coliform Rates
 Measured
per 100 mL of water
CFU = colony forming units
 POTABLE
(drinkable)- 0
 Swimming - <200
 Boating/Fishing- <1000
DO (dissolved oxygen)
 HIGH
levels = good for aquatic organisms
 LOW levels = aerobic bacteria breaking down
waste (lower DO = higher bacteria)
Biological Oxygen Demand (BOD)
 The
amount of oxygen consumed
(demanded) by microorganisms that
decompose organic material

Aerobic bacteria
HIGH BOD = Low DO
LOW quality water
Major Water Pollutants
and Their Effects
 Water
quality and dissolved oxygen (DO)
content in parts per million (ppm) at 20°C.

Only a few fish species can survive in water less
than 4ppm at 20°C.
Figure 21-3
Water
Quality
DO (ppm) at 20°C
Good
8–9
Slightly
polluted
6.7–8
Moderately
polluted
Heavily
polluted
Gravely
polluted
4.5–6.7
Below 4.5
Below 4
Fig. 21-3, p. 496
Plant nutrients
Nitrates/Phosphates
-Human activity can increase these levels
- This leads to…..
“cultural eutrophication”
Nitrogen- 5 ppm = good
20 ppm = poor
Phosphorous- 2 ppm= good
pH Levels
7= Neutral
6-8 = Good
pH can decrease due to:
-acid rain
Caused by?
Turbidity
Measure of how clear the water is:
Low = clear water
High = less transparent, murky
-Measured using a turbidity column
POLLUTION OF FRESHWATER
STREAMS
 Flowing
streams can recover from a
moderate level of degradable water pollutants
if they are not overloaded and their flows are
not reduced.

In a flowing stream, the breakdown of degradable
wastes by bacteria depletes DO and creates and
oxygen sag curve.
• This reduces or eliminates populations of organisms
with high oxygen requirements.
Water Pollution Problems in Streams
 Dilution
and decay of degradable, oxygendemanding wastes and heat in a stream.
Figure 21-4
“Oxygen Sag Curve”
POLLUTION OF FRESHWATER
STREAMS
 Most
developed countries have sharply
reduced point-source pollution but toxic
chemicals and pollution from nonpoint
sources are still a problem.
 Stream
pollution from discharges of
untreated sewage and industrial wastes is
a major problem in developing countries.
Global Outlook: Stream Pollution in
Developing Countries
 Water
in many of
central China's rivers
are greenish black
from uncontrolled
pollution by
thousands of
factories.
Figure 21-5
Case Study: India’s Ganges River:
Religion, Poverty, and Health
 Religious
beliefs, cultural traditions, poverty,
and a large population interact to cause
severe pollution of the Ganges River in India.


Very little of the sewage is treated.
Hindu believe in cremating the dead to free the
soul and throwing the ashes in the holy Ganges.
• Some are too poor to afford the wood to fully cremate.
• Decomposing bodies promote disease and depletes
DO.
Case Study: India’s Ganges River:
Religion, Poverty, and Health
 Daily,
more than 1
million Hindus in
India bathe, drink
from, or carry out
religious ceremonies
in the highly polluted
Ganges River.
Figure 21-6
POLLUTION OF
FRESHWATER LAKES
 Dilution
of pollutants in lakes is less effective
than in most streams because most lake
water is not mixed well and has little flow.


Lakes and reservoirs are often stratified and
undergo little mixing.
Low flow makes them susceptible to runoff.
Cultural Eutrophication
 Eutrophication:
the natural nutrient
enrichment of a shallow lake, estuary or slow
moving stream, mostly from runoff of plant
nutrients from the surrounding land.
 Cultural eutrophication: human activities
accelerate the input of plant nutrients (mostly
nitrate- and phosphate-containing effluents)
to a lake.

85% of large lakes near major population centers
in the U.S. have some degree of cultural
eutrophication.
POLLUTION OF GROUNDWATER
 Groundwater
can become contaminated with
a variety of chemicals because it cannot
effectively cleanse itself and dilute and
disperse pollutants.

The drinking water for about half of the U.S.
population and 95% of those in rural areas
comes from groundwater.
Polluted air
Pesticides
and fertilizers
Coal strip
mine runoff
Hazardous
waste
injection
well
Deicing
road salt
Buried gasoline
and solvent tanks
Gasoline station
Pumping
well
Waste lagoon
Water
pumping well
Cesspool,
septic tank
Sewer
Leakage
from
faulty
casing
Landfill
Accidental
spills
Discharge
Confined
aquifer
Groundwater
flow
Fig. 21-7, p. 501
POLLUTION OF GROUNDWATER
 It
can take hundreds to thousand of years for
contaminated groundwater to cleanse itself of
degradable wastes.


Nondegradable wastes (toxic lead, arsenic,
flouride) are there permanently!!!!!
Slowly degradable wastes (such as DDT) are
there for decades.
Leaking
tank
Water
table
Groundwater
flow
Free gasoline
dissolves in
Gasoline
leakage plume groundwater
(dissolved
(liquid phase)
phase)
Migrating
vapor phase
Contaminant plume moves
with the groundwater
Water well
Fig. 21-8, p. 502
POLLUTION OF GROUNDWATER
 Leaks
from a number of sources have
contaminated groundwater in parts of the
world.


According the the EPA, one or more organic
chemicals contaminate about 45% of
municipal groundwater supplies.
By 2003, the EPA had completed the cleanup of
297,000 of 436,000 underground tanks leaking
gasoline, diesel fuel, home heating oil, or toxic
solvents.
Contamination plume
 Concentration
greatest near the
source
 Diluted as distance
increases
 Contaminants move
WITH the direction
of water
Case Study: Arsenic in Groundwater a Natural Threat
 Toxic Arsenic
(As) can naturally occur at
high levels in soil and rocks.
 Drilling into aquifers can release As into
drinking water supplies.
 According to WHO, more than 112 million
people are drinking water with As levels 5100 times the 10 ppb standard.

Mostly in Bangladesh, China, and West Bengal,
India.
Solutions
Groundwater Pollution
Prevention
Find substitutes for
toxic chemicals
Keep toxic
chemicals out of
the environment
Install monitoring
wells near landfills
and underground
tanks
Require leak detectors
on underground tanks
Ban hazardous
waste disposal
in landfills and
injection wells
Store harmful liquids in
aboveground tanks with leak
detection and collection
systems
Cleanup
Pump to surface,
clean, and return
to aquifer (very
expensive)
Inject
microorganisms
to clean up
contamination
(less expensive
but still costly)
Pump
nanoparticles of
inorganic
compounds to
remove pollutants
(may be the
cheapest, easiest,
and most effective
method but is still
being developed)
Fig. 21-9, p. 504
OCEAN POLLUTION
 Oceans,
if they are not overloaded, can
disperse and break down large quantities of
degradable pollutants.
 Pollution of coastal waters near heavily
populated areas is a serious problem.


About 40% of the world’s population lives near on
or near the coast.
The EPA has classified 4 of 5 estuaries as
threatened or impaired.
Industry
Nitrogen oxides
from autos and
smokestacks,
toxic chemicals,
and heavy metals
in effluents flow
into bays and
estuaries.
Cities
Toxic metals
and oil from
streets and
parking lots
pollute
waters;
Urban sprawl
Bacteria and
viruses from
sewers and septic
tanks contaminate
shellfish beds
Construction sites
Sediments are washed into
waterways, choking fish and
plants, clouding waters, and
blocking sunlight.
Farms
Runoff of pesticides, manure, and
fertilizers adds toxins and excess
nitrogen and phosphorus.
Closed
shellfish beds
Closed
beach
Toxic sediments
Chemicals and toxic
metals contaminate
shellfish beds, kill
spawning fish, and
accumulate in the
tissues of bottom
feeders.
Oxygen-depleted
zone
Oxygen-depleted zone
Sedimentation and algae
overgrowth reduce sunlight,
kill beneficial sea grasses, use
up oxygen, and degrade habitat.
Red tides
Excess nitrogen causes
explosive growth of
toxicmicroscopic algae,
poisoning fish and
marine mammals.
Healthy zone
Clear, oxygen-rich
waters promote growth
of plankton and sea grasses,
and support Fig.
fish.21-10, p. 505
Urban Run-off
 Garbage
(plastics) accumulate
in marine bodies
 Photodegradable: break down
into pellets in the presence of
sunlight, helps reduce litter
 Bioaccumulation:
stored in a
living thing
 Biomagnification: increased
concentration up the food chain
https://www.youtube.com/watch?v=f7dF7Tchi3Y
OCEAN POLLUTION
 Harmful
algal blooms (HAB) are caused by
explosive growth of harmful algae from
sewage and agricultural runoff.
 “Dead Zone”
Figure 21-11
Oxygen Depletion in the Northern
Gulf of Mexico
 A large
zone of
oxygendepleted water
forms for half of
the year in the
Gulf of Mexico
as a result of
HAB.
Figure 21-A
Missouri River
Mississippi
River Basin
Ohio River
Mississippi River
MS
LA
TX
LOUISIANA
Mississippi
River
Depleted oxygen
Gulf of Mexico
Gulf of Mexico
Fig. 21-A, p. 507
Case Study: The Chesapeake Bay –
An Estuary in Trouble
 Pollutants
from six
states contaminate
the shallow
estuary, but
cooperative efforts
have reduced
some of the
pollution inputs.
Figure 21-12
OCEAN OIL POLLUTION
 Most
ocean oil pollution comes from human
activities on land.


Studies have shown it takes about 3 years for
many forms of marine life to recover from large
amounts of crude oil (oil directly from ground).
Recovery from exposure to refined oil (fuel oil,
gasoline, etc…) can take 10-20 years for marine
life to recover.
OCEAN OIL POLLUTION
 Tanker
accidents
and blowouts at
offshore drilling
rigs can be
extremely
devastating to
marine life
(especially diving
birds, left).
Figure 21-13
Exxon-Valdez
 1989-
Oil tanker that leaked 250,000 barrels
of oil into Prince William Sound in Alaska

Slow recovery process
BP Oil Spill
 2010
drilling –
pipe explosion
 Gulf of Mexico
 WORST oil spill in
history
 11 Dead
 134 million gallons
spilled
 Offshore
Arguments For/Against Offshore
drilling?
Solutions
Coastal Water Pollution
Prevention
Reduce input of toxic pollutants
Cleanup
Improve oil-spill cleanup
capabilities
Separate sewage and storm lines
Ban dumping of wastes and
sewage by maritime and cruise
ships in coastal waters
Ban ocean dumping of sludge and
hazardous dredged material
Sprinkle nanoparticles over an
oil or sewage spill to dissolve
the oil or sewage without
creating harmful by-products
(still under development)
Protect sensitive areas from
development, oil drilling, and
oil shipping
Require at least secondary
treatment of coastal sewage
Regulate coastal development
Recycle used oil
Use wetlands, solar-aquatic,
or other methods to treat sewage
Require double hulls for oil tankers
Fig. 21-14, p. 509
PREVENTING AND REDUCING
SURFACE WATER POLLUTION
key to reducing nonpoint pollution – most
of it from agriculture – is to prevent it from
reaching bodies of water.
 The

Farmers can reduce runoff by planting buffers
and locating feedlots away from steeply sloped
land, flood zones, and surface water.
How Would You Vote?
 Should
we greatly increase efforts to reduce
water pollution from nonpoint sources even
though this could be quite costly?


a. No. Most farmers and ranchers can't afford
more regulations.
b. Yes. Nonpoint source water pollution is a
serious environmental and human health threat.
PREVENTING AND REDUCING
SURFACE WATER POLLUTION
 Most
developed countries use laws to set
water pollution standards, but such laws
rarely exist in developing countries.


The U.S. Clean Water Act sets standards for
allowed levels of key water pollutants and
requires polluters to get permits.
EPA is experimenting with a discharge trading
policy similar to that for air pollution control.
Reducing Water Pollution through
Sewage Treatment
 Septic
tanks and various levels of sewage
treatment can reduce point-source water
pollution.
Figure 21-15
Manhole cover
(for cleanout)
Septic tank
Gas
Distribution box
Scum
Wastewater
Sludge
Drain field
(gravel or
crushed stone)
Vent pipe
Perforated pipe
Fig. 21-15, p. 510
Cesspool
Reducing Water Pollution through
Sewage Treatment
 Raw
sewage reaching a municipal sewage
treatment plant typically undergoes:


Primary sewage treatment: a physical process
that uses screens and a grit tank to remove large
floating objects and allows settling.
Secondary sewage treatment: a biological
process in which aerobic bacteria remove as
much as 90% of dissolved and biodegradable,
oxygen demanding organic wastes.
“Sludge”
 All
the leftover contaminants removed from
H2O



Ex: Bacteria, chemicals, heavy metals
Can leach intro groundwater
Stored in landfills
Reducing Water Pollution through
Sewage Treatment
 Primary
and Secondary sewage treatment.
Figure 21-16
Primary
Secondary
Bar screen Grit chamber Settling tank
Aeration tank
Settling tank
Chlorine
disinfection tank
To river,
lake,
or ocean
Sludge
Raw sewage
from sewers
Activated sludge
(kills bacteria)
Air pump
Sludge
digester
Sludge drying bed
Disposed of
in landfill or
ocean or
applied to
cropland,
pasture, or
rangeland
Fig. 21-16, p. 511
Reducing Water Pollution through
Sewage Treatment
 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).
Reducing Water Pollution through
Sewage Treatment
 Sewage
sludge can be used as a soil
conditioner but this can cause health
problems if it contains infectious bacteria and
toxic chemicals.
 Preventing toxic chemicals from reaching
sewage treatment plants would eliminate
such chemicals from the sludge and water
discharged from such plants.
Reducing Water Pollution through
Sewage Treatment
 Natural
and artificial wetlands and other
ecological systems can be used to treat
sewage.

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.
Reducing Water Pollution through
Sewage Treatment
 Water
pollution laws have significantly
improved water quality in many U.S. streams
and lakes but there is a long way to go.
 Some want to strengthen the U.S. Clean
Water Act (CWA) to prevent rather than
focusing on end-of-the-pipe removal.
 Many farmers and developers see the CWA
as limiting their rights as property owners to
fill in wetlands.
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.
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.
Solutions
Water Pollution
• Prevent groundwater contamination
• Reduce nonpoint runoff
• Reuse treated wastewater for irrigation
• Find substitutes for toxic pollutants
• Work with nature to treat sewage
• Practice four R's of resource use (refuse,
reduce, recycle, reuse)
• Reduce air pollution
• Reduce poverty
• Reduce birth rates
Fig. 21-18, p. 517
What Can You Do?
Water Pollution
• Fertilize garden and yard plants with manure or
compost instead of commercial inorganic fertilizer.
• Minimize your use of pesticides.
• Do not apply fertilizer or pesticides near a body of water.
• Grow or buy organic foods.
• Do not drink bottled water unless tests show that your
tap water is contaminated. Merely refill and reuse
plastic bottles with tap water.
• Compost your food wastes.
• Do not use water fresheners in toilets.
• Do not flush unwanted medicines down the toilet.
• Do not pour pesticides, paints, solvents, oil, antifreeze,
or other products containing harmful chemicals down
the drain or onto the ground.
Fig. 21-19, p. 517