Groundwater by huangyinggok

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									ENVIRONMENTAL SCIENCE 13e



          CHAPTER 11:
          Water Resources and
          Water Pollution
          Water video questions
•   How much fresh water on earth?
•   How much in rivers, lakes, and streams?
•   How much is used for growing food?
•   How much water needed to produced a pound of beef?
    – A cup of coffee?
• In US how much water is used for flushing toilet?
• How much water does the average American use per
  day?
• How many people today lack access to clean, safe
  water supply?
• http://www.youtube.com/watch?v=Fvk
  zjt3b-dU
• http://www.youtube.com/watch?v=2p
  XuAw1bSQo
Core Case Study: The Colorado
         River Story
• 1400 miles through 7 states
• 14 dams and reservoirs
• Electricity for 30 million people
• Water for 15% of U.S. crops and
  livestock
• Water for desert cities
• Very little water reaches the Gulf of
  California
             5 major problems
• Colorado river basin includes some of driest lands in US
  and Mexico
• For its size river has only modest flows
• Legal pacts signed in 1922 and 1944 allocated more
  water for human use in US and Mexico than the river can
  supply (even when no drought) and allocated no water
  for environmental purposes)
• Since 1960 river has rarely flowed fully to Gulf of
  California because of reduced water flow (dams),
  increased water withdrawals, and prolonged drought
• Major Pollution
• Reference p. 242
Fig. 11-1, p. 238
Fig. 11-2, p. 238
• http://earthobservatory.nasa.gov/IOTD/vie
  w.php?id=1288
    11-1 Will We Have Enough
         Usable Water?
• Concept 11-1A We are using available
  freshwater unsustainably by wasting it,
  polluting it, and charging too little for this
  irreplaceable natural resource.
• Concept 11-1B One of every six people
  does not have sufficient access to clean
  water, and this situation will almost
  certainly get worse.
  Importance and Availability of
           Water (1)
• Earth as a watery world – saltwater covers about
  71% of the earth’s surface
• Water is one of our most poorly managed
  resources
• Water access is a global health issue
   – 3900 children under 5 die every day from
     waterborne disease
• Water is an economic issue because it is vital for
  reducing poverty and producing food and energy
  Importance and Availability of
           Water (2)
• National and global security issue because of
  increasing tensions within and between nations
  over access to limited water resources
• Environmental issue because excessive
  withdrawal of water from rivers and aquifers
  results in dropping water tables, lower river
  flows, shrinking lakes, and losses of wetlands
• Freshwater availability – 0.024%
   – Groundwater
   – Lakes
   – Rivers
   – Streams
Fig. 11-3, p. 240
                       Groundwater
                    important terms to know
• Groundwater:         water that sinks into the soil and is stored
  in slowly flowing and slowly renewed underground reservoirs
  called aquifers
• Zone of saturation: area where all available pores in
  soil and rock are filled by water
• Water table: upper surface of the zone of saturation
• Aquifers: porous, water saturated layers of sand, gravel, or
  bedrock that can yield an economically significant amount of
  water
• Natural recharge:              natural replenishment of an aquifer by
  precipitation that percolates downward through soil and rock

• Lateral recharge:            recharge occurring from the side by rivers
  and streams
• http://www.eoearth.org/article/Aquifer
              Surface Water
•   Surface runoff
•   Watershed (drainage) basin
•   Reliable runoff – 1/3 of total
•   Runoff use (worldwide)
    – Domestic – 10%
    – Agriculture – 70%
    – Industrial – 20%
Case Study: Freshwater Resources
     in the United States (1)
• Uneven distribution
• Contamination by agriculture and
  industry
• Eastern U.S.
• Western U.S.
• Groundwater withdrawal: ~50% of
  total use
• Drought: prolonged period in which precipitation is at
  least 70% lower and evaporation is higher than normal in an
  area that is normally not dry
Case Study: Freshwater Resources
     in the United States (2)
• Arid and semiarid West:
   – 85% of water to irrigate thirsty crops
   – Water hot spots
   – Southwest: “permanent drying” by 2050
• Water tables dropping
• 36 states to face water shortages by
  2013 (drought, rising temps, pop growth, urban sprawl, and
  excessive use and waste of water)
Fig. 11-4, p. 241
Water hotspots in 17 Western states that, by 2025, could face intense conflicts over
scarce water needed for urban growth, irrigation, recreation, and wildlife. Some analysts
suggest that this is a map of places not to live in the forseeable future.
                 Washington
                                                              North
                                          Montana             Dakota
                Oregon
                               Idaho                          South
                                            Wyoming           Dakota

                       Nevada                                  Nebraska

                                     Utah                           Kansas
                                                Colorado

                 California                                        Oklahoma

                                Arizona        New
                                               Mexico
                                                               Texas

               Highly likely conflict potential
               Substantial conflict potential
               Moderate conflict potential
               Unmet rural water needs
                                                                                            Fig. 11-5, p. 242
       Freshwater Shortages
• Causes of water scarcity
  – Dry climate
  – Drought
  – Too many people
  – Wasting water
• 2050: 60 countries will face water stress
• 1 of 7 people – no regular access to clean
  water
• Potential international conflicts over water
Stress on the world’s major river basins, based on a comparison of the amount of water
available with the amount used by humans.




                                                                           Fig. 11-6, p. 243
   11-2 How Can We Increase
        Water Supplies?
• Concept 11-2A Groundwater used to
  supply cities and grow food is being
  pumped from aquifers in some areas
  faster than it is renewed by precipitation.
• Concept 11-2B Using dams, reservoirs,
  and transport systems to provide water to
  arid regions has increased water supplies
  in some areas, but has disrupted
  ecosystems and displaced people.
  11-2 How Can We Increase
       Water Supplies?
• Concept 11-2C We can convert salty
  ocean water to freshwater, but the
  cost is high, and the resulting salty
  brine must be disposed of without
  harming aquatic or terrestrial
  ecosystems.
Increasing Freshwater Supplies
•   Withdrawing groundwater
•   Dams and reservoirs
•   Transporting surface water
•   Desalination
•   Water conservation
                           Trade-Offs
               Withdrawing Groundwater
Advantages                          Disadvantages
Useful for drinking and             Aquifer depletion from
irrigation                          overpumping


                                    Sinking of land (subsidence)
Available year-round                from overpumping


Exists almost everywhere            Aquifers polluted for
                                    decades or centuries


Renewable if not                    Saltwater intrusion into
overpumped or                       drinking water supplies near
contaminated                        coastal areas

                                    Reduced water flows into
No evaporation losses               surface waters


                                    Increased cost and
Cheaper to extract than             contamination from deeper
most surface waters                 wells

                                                                   Fig. 11-7, p. 244
    Groundwater Withdrawal
• Most aquifers are renewable
• U.S. groundwater withdrawn 4X faster
  then it’s replenished
• Ogallala aquifer
• California’s Central Valley and
  agriculture
Areas of greatest aquifer depletion from groundwater overdraft in the continental
United States. Aquifer depletion in also high in Hawaii and Puerto Rico (not shown).




Groundwater
Overdrafts:
     High
      Moderate
      Minor or none
                                                                           Fig. 11-8, p. 244
                               Solutions
                   Groundwater Depletion
Prevention                                 Control
Waste less water                           Raise price of water to
                                           discourage waste



Subsidize water conservation               Tax water pumped from
                                           wells near surface waters



Limit number of wells                      Set and enforce minimum
                                           stream flow levels



Do not grow water-intensive                Divert surface water in wet
crops in dry areas                         years to recharge aquifers


                                                               Fig. 11-9, p. 245
      Science Focus: Are Deep
        Aquifers the Answer?
•    Could have enough water to supply
     billions of people for centuries
•    Concerns
    1. Nonrenewable
    2. Geological and ecological impacts of
       pumping them is unknown
    3. No treaties to govern water rights
    4. Costs unknown and could be high
Provides             Flooded land
irrigation water     destroys forests
above and            or cropland and
below dam            displaces peopl



                     Large losses o
                     water through
                     evaporation
Provides water
for drinking
                     Deprives
                     downstream
                     cropland and
Reservoir useful     estuaries of
for recreation       nutrient-rich si
and fishing



                     Risk of failure
Can produce          and devastatin
cheap electricity    downstream
(hydropower)         flooding


Reduces
downstream           Disrpupts
flooding             migration and
                     spawning of
                     some fish
                    Fig. 11-10, p. 246
     Overtapped Colorado River Basin

• Only small amount reaches Gulf of
  California
  – Threatened species
• Climate change will likely decrease flows
• Less water in Southwest
  – Political and legal battles
• Silt behind dams not reaching delta and will
  eventually fill up reservoirs
                              30                  Hoover Dam
                                                  completed (1935)
Flow (billion cubic meters)




                              25


                              20


                              15                                     Glen Canyon
                                                                     Dam completed
                                                                     (1963)
                              10


                              5


                              0
                                   1910   1920   1930 1940 1950      1960 1970 1980   1990 2000
                                                                 Year
                                                                                         Fig. 11-11, p. 247
     California Water Project
• Dams, pumps, aqueducts
• Southern California would otherwise
  be desert
• Climate change will reduce water
  availability in California
• People in southern California may
  have to move
• Groundwater already being depleted
                  CALIFORNIA
                        Shasta Lake    NEVADA
                                                            UTAH
Sacramento              Oroville Dam and
River                      Reservoir
                        Feather
North Bay                       Lake Tahoe
                        River
Aqueduct
                        Sacramento
      San Francisco


                       Sa
South Bay                                    Hoover Dam

                          n
                         Jo
Aqueduct                         Fresno     and Reservoir

                          aq
     San Luis Dam                            (Lake Mead)
                               uin
                                                                   Colorado
     and Reservoir                        Los Angeles              River
                                Va         Aqueduct
California Aqueduct              lle
                                     y                        ARIZONA
                                          Colorado River
               Santa Barbara                Aqueduct        Central Arizona
                      Los Angeles                              Project

                                           Salton Sea   Phoenix
                              San Diego

                                                                  Tucson

                                                              MEXICO
                                                                           Fig. 11-12, p. 247
       Aral Sea Disaster (1)
• Large-scale water transfers in dry
  central Asia
• Water loss and salinity increase
• Wetland destruction and wildlife
• Fish extinctions hurt fishing industry
         Aral Sea Disaster (2)
•   Wind-blown salt
•   Water pollution
•   Climatic changes
•   Restoration efforts
     1976                                            2006




Satellite photos show the sea in 1976 and in 2006.



                                                                Stepped Art
                                                            Fig. 11-13, p. 248
              Aral Sea

• http://www.youtube.com/watch?v=9HfkZX
  LRYu8
• http://www.youtube.com/watch?v=Z0Pi61
  SyVSM&feature=fvwrel
    Removing Salt from Seawater
•   Desalination
•   Distillation
•   Reverse osmosis
•   13,000 plants in 125 countries
       Major Problems with
          Desalination
• High cost
• Death of marine organisms
• Large quantity of brine wastes
 11-3 How Can We Use Water
      More Sustainably?
• Concept 11-3 We can use water
  more sustainably by cutting water
  waste, raising water prices, slowing
  population growth, and protecting
 aquifers, forests, and other
 ecosystems that store and
 release water.
   Reducing Water Waste (1)
• Benefits of water conservation
• Worldwide – 65-70% loss
  – Evaporation, leaks
  – Can be reduced to 15%
• Increase the cost of water use
  – End subsidies for wasteful water use
  – Provide subsidies for efficient water use
   Reducing Water Waste (2)
• Improve irrigation efficiency
  – Center pivot
  – Low-pressure sprinkler
  – Precision sprinklers
  – Drip irrigation
• Use less in homes and businesses
                                                                              Center pivot
                                                                     (efficiency 80% with low-pressure
                                                Drip irrigation       sprinkler and 90–95% with LEPA
                                              (efficiency 90–95%)                 sprinkler)

              Gravity flow                 Above- or below-ground         Water usually pumped from
(efficiency 60% and 80% with surge valves) pipes or tubes deliver water   underground and sprayed
                                           to individual plant roots.     from mobile boom with
    Water usually comes from an                                           sprinklers.      Stepped Art
    aqueduct system or a nearby river.
                                                                                        Fig. 11-14, p. 251
Fig. 11-16, p. 252
                Solutions
      Sustainable Water Use
Waste less water and subsidize
water conservation

Do not deplete aquifers

Preserve water quality

Protect forests, wetlands,
mountain glaciers, watersheds,
and other natural systems that
store and release water

Get agreements among regions
and countries sharing surface
water resources

Raise water prices

Slow population growth
                                 Fig. 11-17, p. 253
Fig. 11-18, p. 253
 11-4 How Can We Reduce the
      Threat of Flooding?
• Concept 11-4 We can lessen the
  threat of flooding by protecting more
  wetlands and natural vegetation in
  watersheds and by not building in
  areas subject to frequent flooding.
     Benefits of Floodplains
• Highly productive wetlands
• Provide natural flood and erosion
  control
• Maintain high water quality
• Recharge groundwater
• Fertile soils
• Nearby rivers for use and recreation
• Flatlands for urbanization and farming
                 Floods
•   Deposit rich soils on floodplains
•   Deadly and destructive
•   Human activities worsen floods
•   Failing dams and water diversion
•   Hurricane Katrina and the Gulf Coast
•   Climate change will increase coastal
    flooding
                                                   Tree plantation
  Diverse
  ecological
                       Evapotranspiration                  Roads             Evapotranspiration decreases
  habitat
                            Trees reduce soil              destabilize        Overgrazing accelerates soil
                            erosion from heavy             hillsides          erosion by water and wind
                            rain and wind                                           Winds remove
                                    Agricultural                                    fragile topsoil
                                    land                                                 Agricultural
                                                                                         land is flooded
                                                                                         and silted up
                                             Gullies and
Tree roots
                                             landslides
stabilize soil
                                      Heavy rain erodes topsoil
       Vegetation releases water                           Silt from erosion fills    Rapid runoff
       slowly and reduces flooding                         rivers and reservoirs      causes flooding




    Forested Hillside                                      After Deforestation
                                                                                                Stepped Art
                                                                                            Fig. 11-19, p. 254
   Case Study: Floodplains of
         Bangladesh
• Dense population on coastal
  floodplain
• Moderate floods maintain fertile soil
• Increased frequency of large floods
• Development in the Himalayan
  foothills
• Destruction of coastal wetlands
                              Solutions
                Reducing Flood Damage
Prevention                                Control
Preserve forests on                       Straighten and deepen
watersheds                                streams (channelization)


Preserve and restore
wetlands in floodplains


                                          Build levees or floodwalls
Tax development on
                                          along streams
floodplains


Use floodplains primarily
for recharging aquifers,
sustainable agriculture and
forestry                                  Build dams


                                                              Fig. 11-20, p. 256
  11-5 How Can We Deal with
       Water Pollution?
• Concept 11-5A Streams can cleanse
  themselves of many pollutants if we do not
  overload them or reduce their flows.
• Concept 11-5B Reducing water pollution
  requires preventing it, working with nature
  in treating sewage, cutting resource use
  and waste, reducing poverty, and slowing
  population growth.
     Water Pollution Sources
• Point sources
  – Discharge at specific locations
  – Easier to identify, monitor, regulate
• Nonpoint sources
  – Broad, diffuse areas
  – Runoff of chemicals and sediment
  – Agriculture
  – Control is difficult and expensive
Table 11-1, p. 257
           Stream Pollution
•   Natural recovery processes
•   Oxygen sag curve
•   Effective regulations in the U.S.
•   Problems in developing countries
Dilution and decay of degradable, oxygen-demanding wastes (or heated water) in a stream, showing the oxygen
sag curve (blue) and the curve of oxygen demand (red)


                                          Point source




                                                                                                     an water
                                                                                          N ormal cle t, perch,
                                                                         t, Pollutant-           s(Trou
                                                     n t- F ish absen e tolerant fishes organism      , stonefly
                                                                                                                 )
                                    rganisms Polluta shes fungi, sludg      (carp, gar)  ba ss,mayfly
                         an water o        tolerant fi         worms,                                         8 ppm
       Types of
               Normal cle perch, bass,
                   (Tro ut,                   (carp, gar)      ba cteria
      organism
                s                nefly)                                 ic)
                     mayfly, sto                             (anaerob

                 8 ppm
       Dissolved
        oxygen
         (ppm)

                l                                                                                      Zone
       Biologica                                                                               Clean
        oxygen                                                                         y
                                                                                Recover
        demand                                                             ne
                                                                  eptic Zo        Zone
                                                      po sition S
                                                Decom
                                    one             Zone
                          Clean Z




                                                                                                    Fig. 11-21, p. 258
Highly polluted river in China.




                                  Fig. 11-22, p. 259
  Individuals Matter: John Beal p. 258

• Restored Hamm Creek in Washington State
• Persuaded companies to stop polluting the
  creek, hauled out many truckloads of trash,
  began 15 yr project of planting thousands of
  trees along streams banks, also restored natural
  waterfalls and salmon spawning beds
• Outstanding example of Stewardship based on
  the idea that “All sustainability is local”
• http://www.youtube.com/watch?v=5smNWchqo6
  o
             Lake Pollution
• Dilution less effective than with streams
  – Stratification
  – Low flow
• Lakes are more vulnerable than
  streams
• Eutrophication – natural aging process
• Oligotrophic
     Cultural Eutrophication
• Nitrate- and phosphate-containing effluents
• Dense colonies of plants, algae,
  cyanobacteria
• Can lead to die-off of fish and other
  animals
• Prevent by limiting phosphate and nitrate
  use
• Lakes can be cleaned, and can recover
      Groundwater Pollution (1)
•   Pollution sources
•   Slow flow, dilution, dispersion
•   Low dissolved oxygen
•   Fewer bacteria
•   Cooler temperatures
    Groundwater Pollution (2)
• Long time scale for natural cleansing
  – Degradable wastes – organic matter
  – Slowly degradable wastes – DDT
  – Nondegradable wastes – lead, arsenic
                                                     Polluted air




                                                 Pesticides                                               Hazardous
                                                 and fertilizers                                               waste
                                                                                                            injection
                    Deicing
Coal strip                                                                                                       well
                    road salt                                                Buried gasoline
mine runoff
                                                                             and solvent
                                                                             tanks
                                                                                            Cesspool,
              Pumping                                       Gasoline                        septic tank
              well                                          station
                                                          Water
                  Waste lagoon                            pumping well
                                                                               Sewer
                                                      Landfill

                                Accidental                                                                Leakage
                                spills                                                                    from faulty
                                                                                                          casing

                                                                      ifer
                                                                                                 Discharge
                                                                r aqu
                                                             ate                       Confined
                                                        hw
                                                    fres
                                              ned                  ifer                aquifer
                                      co   nfi             r   aqu            Groundwater
                                   Un                  ate
                                                re  shw                       flow
                                          e  df
                                      nfin
                                   Co


                                                                                                     Fig. 11-23, p. 260
Extent of Groundwater Pollution
•   Global scale – not much known
•   Monitoring is very expensive
•   Underground fuel tank leakage
•   Arsenic
•   Protecting groundwater – prevention
    is best and least expensive
                              Solutions
                    Groundwater Pollution
Prevention                                Cleanup
Find substitutes for toxic                Pump to surface, clean,
chemicals                                 and return to aquifer
                                          (very expensive)
Keep toxic chemicals out of
the environment

Install monitoring wells near
landfills and underground
                                          Inject microorganisms to
tanks
                                          clean up contamination
                                          (less expensive but still
Require leak detectors on
                                          costly)
underground tanks

Ban hazardous waste disposal
in landfills and injection wells

Store harmful liquids in                  Pump nanoparticles of
aboveground tanks with leak               inorganic compounds to
detection and collection                  remove pollutants (still
systems                                   being developed)

                                                                      Fig. 11-24, p. 261
      Purifying Drinking Water
• Developed countries
  – Reservoir storage
  – Purification plant
• Developing countries without purification plants
  – Clear plastic bottle in sun, with black side
  – http://www.grilink.org/sunwater.htm

  – LifeStraw
The Lifestraw, designed by Torben Vestergaard Frandsen
http://www.youtube.com/watch?feature=fvwp&NR=1&v=fZwe5B8FaoU




                                                               Fig. 11-25, p. 263
Science Focus: Is Bottled Water
         the Answer?
• 500-1000 times the cost of tap water
  – Americans spent $15 billion in 2007
• About 1/4 is ordinary tap water
• About 40% of bottled water
  contaminated
• Water testing standards lower than
  for tap water
• Environment: energy use, pollution
           Bottled Water
• http://www.mnn.com/food/healthy-
  eating-recipes/stories/5-reasons-not-
  to-drink-bottled-water#
           Ocean Pollution
• Coastal areas – highly productive
  ecosystems
  – Occupied by 40% of population
  – Coastal populations will double by 2050
  – About 80% marine pollution originates on land
• Ocean dumping controversies
• Algal blooms
• Oxygen-depleted zones
Industry              Cities                 Urban sprawl
Nitrogen oxides       Toxic metals and       Bacteria and viruses from
from autos and        oil from streets and   sewers and septic tanks
smokestacks,          parking lots pollute   contaminate shellfish beds     Construction sites
toxic chemicals,      waters; sewage         and close beaches; runoff of   Sediments are washed into
and heavy metals in   adds nitrogen and      fertilizer from lawns adds     waterways, choking fish and plants,
effluents flow into   phosphorus.            nitrogen and phosphorus.       clouding waters, and blocking sunlight.
bays and estuaries.
                                                                                          Farms
                                                                                          Runoff of pesticides, manure, and
                                                                                          fertilizers adds toxins and excess
                                                                                          nitrogen and phosphorus.


                                                                                                    Red tides
                                                                Closed                              Excess nitrogen causes
                                                                shellfish beds                      explosive growth of toxic
                                                                                                    microscopic algae,
                                       Closed                                                       poisoning fish and
                                       beach                                                        marine mammals.
                                                    Oxygen-depleted
                                                    zone




Toxic sediments
Chemicals and toxic metals
contaminate shellfish beds,
kill spawning fish, and
accumulate in the tissues
of bottom feeders.


                                                       Oxygen-depleted zone                       Healthy zone
                                                       Sedimentation and algae                    Clear, oxygen-rich
                                                       overgrowth reduce sunlight,                waters promote growth
                                                       kill beneficial sea grasses, use           of plankton and sea
                                                       up oxygen, and degrade habitat.            grasses,and support fish.
                                                                                                                Fig. 11-26, p. 263
     Pacific Garbage Patch
• http://www.youtube.com/watch?v=SQ
  h898IcOgM&feature=related
 Science Focus: Oxygen Depletion
  in the Northern Gulf of Mexico
• Mouth of Mississippi River in spring
  and summer
• Suffocates fish, crab, shrimp
• Cultural eutrophication
• Caused by fertilizer use in Mississippi
  watershed
• Need less and more intelligent use of
  fertilizers
• Need better flood control
A large zone of oxygen-depleted water forms each year during the spring and summer in the Gulf of
Mexico as a result of oxygen-depleting algal blooms. Evidence indicates that it is created mostly by
huge inputs of nitrate plant nutrients from farms, cities, factories, and sewage treatment plants in the
vast Mississippi River basin.
                                                                        Missouri River



                                             Mississippi
                                             River Basin


                                                                                      Ohio River

                                                                                  Mississippi River




                                                     Depleted oxygen




Stepped Art                                                                              Fig. 11-A, p. 265
  Case Study: Ocean Pollution
           from Oil
• Crude and refined petroleum
• Tanker accidents – Exxon Valdez
• Urban and industrial runoff is largest
  source
Effects of Oil Pollution on Ocean
           Ecosystems
• Volatile organic hydrocarbons
  – Kill larvae
  – Destroy natural insulation and buoyancy
    of birds and mammals
• Heavy oil
  – Sinks and kills bottom organisms
  – Coral reefs die
     Gulf of Mexico Oil Spill
• http://www.youtube.com/watch?v=8U
  ax5FRWnvs&feature=related
       Oil Cleanup Methods
• Current methods recover no more
  than 15%
• Prevention is most effective method
  – Control runoff
  – Double-hull tankers
                             Solutions
                   Coastal Water Pollution
Prevention                           Cleanup
Reduce input of toxic                Improve oil-spill cleanup
pollutants                           capabilities

Separate sewage and
storm lines

                                     Use nanoparticles on
Ban dumping of wastes
                                     sewage and oil spills to
and sewage by ships in
                                     dissolve the oil or sewage
coastal waters
                                     (still under development)

Ban ocean dumping of
sludge and hazardous
dredged material                     Require secondary
                                     treatment of coastal
                                     sewage
Regulate coastal
development, oil drilling,
and oil shipping
                                     Use wetlands, solar-aquatic,
Require double hulls for             or other methods to treat
oil tankers                          sewage

                                                                    Fig. 11-27, p. 264
  Preventing Nonpoint Source
          Pollution (1)
• Mostly agricultural waste
• Use vegetation to reduce soil erosion
• Reduce fertilizer use
  Preventing Nonpoint Source
          Pollution (2)
• Use plant buffer zones around fields
  and animal feedlots
• Keep feedlots away from slopes,
  surface water, and flood zones
• Integrated pest management
• Organic farming methods
Laws for Reducing Point Source
           Pollution
• Clean Water Act
• Water Quality Act
• Discharge trading controversies
  – Cap-and-trade of pollutants
Case Study: Reducing Water Pollution
   from Point Sources in the U.S.
• Impressive achievements since 1972 law
• Bad news – 2006 survey
  – 45% of lakes and 40% of streams too polluted
    for fishing and swimming
  – Runoff polluting 7 of 10 rivers
  – Fish caught in 1/4 of waterways unsafe to eat
• Gasoline storage tanks: tens of thousands
  leaking
  Sewage Treatment Systems
• Rural and suburban areas – septic
  tanks
• Urban areas – wastewater treatment
  plants
  – Primary sewage treatment – physical
    process
  – Secondary sewage treatment –
    biological process
  – Chlorination – bleaching and disinfection
   Primary and secondary sewage treatment.
                 Primary                                        Secondary

                                                                               Chlorine
 Bar screen Grit chamber   Settling tank   Aeration tank      Settling tank    disinfection tank




                                                                                              To river,
                                                                                              lake,
                               Sludge                                                         or ocean
Raw sewage                                        Activated sludge            (kills bacteria)
from sewers

                                              Air pump



                                           Sludge digester                     Disposed of in
                                                                               landfill or ocean or
                                                                               applied to cropland,
                                                                               pasture, or rangeland


                                                                Sludge drying bed




                                                                                         Fig. 11-28, p. 268
 Improving Sewage Treatment
• Systems that exclude hazardous and
  toxic chemicals
• Require businesses to remove
  harmful chemicals before sewage
  sent to treatment plant
• Reduce or eliminate use of toxic
  chemicals
• Composting toilet systems
• Wetland-based sewage treatment
   Science Focus: Treating
Sewage by Working with Nature
• Living machines
• Tanks with increasingly complex
  organisms
• Artificially created wetlands
• Scientific principles of sustainability
Fig. 11-29, p. 269
Fig. 11-30, p. 269
   Three Big Ideas from This
         Chapter - #1
One of the world’s major environmental
 problems is the growing shortages of
 freshwater in parts of the world.
   Three Big Ideas from This
         Chapter - #2
We can use water more sustainably by
 cutting water waste, raising water
 prices, slowing population growth,
 and protecting aquifers, forests, and
 other ecosystems that store and
 release water.
   Three Big Ideas from This
         Chapter - #3
Reducing water pollution requires
 preventing it, working with nature in
 treating sewage, cutting resource use
 and waste, reducing poverty, and
 slowing population growth.

								
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