Download Water pollution

Chapter 21
Water Pollution
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)
Major Water Pollutants
and Their Effects
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
Major Sources of Water Pollution
 Agriculture
 Sediment
 Fertilizers, pesticides
 Animal wastes
 Salinization of soil from over irrigation
 Industry
 NOx and SOx
 Mining
 Suspended Particulate Matter (dust, ash)
 SOx
Mining pollution: arsenic,
mercury, sulfuric acid
Coliform bacteria
 Fecal coliform is found in
the intestines and colon
of animals and humans.
 Enters streams through
run-off
 Drinking can cause
dehydration and diarrhea
POLLUTION OF FRESHWATER
STREAMS
 Flowing streams can recover from a moderate level of
degradable (animal wastes and other Organic-based
pollutants) 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 (because oxygen is used in decomposition process) and creates
an oxygen sag curve.
 DO is directly related to water quality
Water Pollution Problems in Streams
 Dilution and decay of degradable, oxygen-demanding wastes
and heat in a stream.
Figure 21-4
Indicator species
 Used to determine health
of water
 Include many species
 Mussels (filter feeders)
 Trout
 Macro invertebrates
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.
 Why?
 How have damming and diversions affected pollution of streams and
rivers?
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
Ganges River in India
• Religious beliefs
• Cultural rituals
• Large population size
Cuyahoga River in Ohio
 Why did this river catch on fire?
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.
 Various human activities can overload lakes with plant
nutrients, which decrease DO and kill some aquatic species.
 Fertilizers, pesticides, oil and gas leaks/spills, heavy metal leaching
(Hg, Pb, Se)
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 phosphatecontaining effluents) to a lake.
 Primarily from animal wastes, fertilizers, run-off from
lawns and golf courses, atmospheric deposition, mining,
pesticides, and sediment
Blooms from eutrophication
 Algae (red, yellow,
brown), cyanobateria,
water hyacinth,
duckweed
 Lower DO (during
decomposition), reduce
light needed for
photosynthesis by
phytoplanktonkill fish
 Waterborne and
airborne toxins kill fish,
poison seafood, kills
birds, reduces tourism
Reduce and Prevent eutrophication
Clean-Up
 Remove excess weeds
 Pump air in
 Herbicides and algicides to
control plant growth
Prevention
 Waste water treatment,
 Reduce runoff with soil
conservation
 Ban phosphates in detergents
Great Lakes and pollution
 http://www.youtube.com/watch?v=QtNH0E4XSdQ
POLLUTION OF GROUNDWATER
 Reasons why ground water cannot cleanse
itself and dilute and disperse pollutants.




Flows slowly
Low DO concentration
Less bacteria (lower decomposition)
Lower temperature so reactions to cleanse slowed
down.
 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.
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.
 What are the most affected coastal areas?
Estuaries
Coral Reefs
Mangrove
forests
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
Oxygen Depletion in the Northern
Gulf of Mexico
 A large zone of
oxygen-depleted water
forms for half of the
year in the Gulf of
Mexico as a result of
HAB.
 Prevention:
 Use less fertilizer
 Reduce N-inputs
 Plant forests and
grasses
 Restore wetlands
 Lower NOx emissions
Figure 21-A
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.
 BP oil spill
 Exxon Valdez oil spill in Alaska
 http://www.youtube.com/watch?v=DPgIfT5mGVc&feature=fvst
How do oil spills affect aquatic life?




Kill fish and other aquatic life in larval stage
Coats bird wings with oil drown
Smother bottom dwellers (oysters, mussels, crabs)
Kills coral by covering it
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
 The key to reducing nonpoint pollution – most of it from
agriculture – is to prevent it from reaching bodies of water.
 Farmers can reduce runoff by planting buffers and locating
feedlots away from steeply sloped land, flood zones, and surface
water, keeping land covered so it lowers erosions, reduce fertilizer
use and pesticide use.
Laws to KNOW!
 Clean Water Act (1972) regulates discharges of pollutants
into water, sets water quality standards for contaminates in
surface water
 Water Quality Act (1987) set standards for water quality
 Ocean Dumping Act (1972) dumping of sewage sludge and
industrial waste is prohibited. Radiological, chemical and
biological warfare agents and high-level radioactive wastes are
prohibited.
 Safe Drinking Water Act (1974) sets minimum standards and
regulates public drinking water.
 Convention of the Prevention of Marine Pollution by Dumping
of Waste and other Matter- control ocean pollution
 EPA is experimenting with a discharge trading policy
like Air Pollution
Reducing Water Pollution through
Sewage Treatment
 Septic tanks and various levels of sewage treatment can reduce
point-source water pollution if installed and maintained
properly.
Figure 21-15
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.
Reducing Water Pollution through
Sewage Treatment
 Primary and Secondary sewage treatment.
Figure 21-16
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 diseasecarrying 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.
 Sewage sludge is often dumped into landfills or in the deep
ocean.
 Preventing toxic chemicals from reaching sewage treatment
plants would eliminate such chemicals from the sludge and
water discharged from such plants.
What is a composting toilet?
 http://www.youtube.com/watch?v=chDcTwR5DtM
Reducing Water Pollution through
Natural Processes
 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.
 http://www.youtube.com/watch?v=MR7Wj-b2kL8
DRINKING WATER QUALITY
 Centralized water treatment plants and watershed
protection can provide safe drinking water for city
dwellers in developed countries.
 Exposing water to heat and the sun’s UV rays for 3
hours can kill infectious microbes.
 Bolivia and watershed protection:
 http://www.youtube.com/watch?v=BLWV9H8jAfQ
Is Bottled Water the Answer?
 Some bottled water is not as pure as tap water and
costs much more.
 Filters can collect microbes and harm more than it helps
if not changed properly.
 1.4 million metric tons of plastic bottles are thrown
away.
 Fossil fuels are used to make plastic bottles.
 The oil used to produce plastic bottles in the U.S. each
year would fuel 100,000 cars.
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