APES-Ch.22-WaterPollutionPPT by wanghonghx


									 Chapter 22

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
                  Uses the sun and a series
                   of tanks containing plants,
                   snails, zooplankton,
                   crayfish, and fish (that
                   can be eaten or sold for
 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

           A  fecal coliform
             bacteria test is used
             to indicate the likely
             presence of
             bacteria in water.
           Major Water Pollutants
             and Their Effects

 Waterquality 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.
 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

        and decay of degradable, oxygen-
 Dilution
  demanding wastes and heat in a stream.
 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
 Case Study: India’s Ganges River:
   Religion, Poverty, and Health
 Religiousbeliefs, 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
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.
             POLLUTION OF
 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.
            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
 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

                          and fertilizers
                  Deicing                                                              well
Coal strip        road salt                                 Buried gasoline
mine runoff                                                 and solvent tanks
              Pumping                         Gasoline station          Cesspool,
              well                                                      septic tank
                Waste lagoon                 pumping well
                                            Landfill                               Leakage
                          Accidental                                               faulty
                          spills                                                   casing

 Itcan 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.


       flow    Free gasoline
Gasoline       dissolves in
leakage plume groundwater
(liquid phase) (dissolved      Migrating
               phase)          vapor phase
                Contaminant plume moves      Water well
                with the groundwater
 Leaks from a number of sources have
 contaminated groundwater in parts of the
     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
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 5-
  100 times the 10 ppb standard.
     Mostly in Bangladesh, China, and West Bengal,
              Groundwater Pollution
  Prevention                       Cleanup

Find substitutes for               Pump to surface,
toxic chemicals                    clean, and return
                                   to aquifer (very
Keep toxic                         expensive)
chemicals out of
the environment
Install monitoring                 microorganisms
wells near landfills               to clean up
and underground                    contamination
tanks                              (less expensive
Require leak detectors             but still costly)
on underground tanks
Ban hazardous                      nanoparticles of
waste disposal                     inorganic
in landfills and                   compounds to
injection wells                    remove pollutants
                                   (may be the
Store harmful liquids in           cheapest, easiest,
aboveground tanks with leak        and most effective
detection and collection           method but is still
systems                            being developed)
             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               Cities          Urban sprawl
Nitrogen oxides        Toxic metals    Bacteria and              Construction sites
from autos and         and oil from    viruses from              Sediments are washed into
smokestacks,           streets and     sewers and septic         waterways, choking fish and
toxic chemicals,       parking lots    tanks contaminate         plants, clouding waters, and
and heavy metals       pollute         shellfish beds            blocking sunlight.
in effluents flow      waters;
into 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
                                                                                  toxicmicroscopic algae,
                                  Closed                                          poisoning fish and
                                  beach                                           marine mammals.

Toxic sediments
Chemicals and toxic
metals contaminate
shellfish beds, kill
spawning fish, and
accumulate in the
tissues of bottom
                                           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 grasses,
                                           up oxygen, and degrade habitat.                 fish.
                                                                              and support Fig. 21-10, p. 505

 Harmfulalgal blooms (HAB) are caused by
 explosive growth of harmful algae from
 sewage and agricultural runoff.
Oxygen Depletion in the Northern
        Gulf of Mexico
                    A  large zone of
                      depleted water
                      forms for half of
                      the year in the
                      Gulf of Mexico
                      as a result of
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.
 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.
            Tanker  accidents
            and blowouts at
            offshore drilling
            rigs can be
            devastating to
            marine life
            (especially diving
            birds, left).
                            Coastal Water Pollution
                    Prevention                Cleanup
Reduce input of toxic pollutants              Improve oil-spill cleanup
Separate sewage and storm lines

Ban dumping of wastes and
sewage by maritime and cruise                 Sprinkle nanoparticles over an
ships in coastal waters                       oil or sewage spill to dissolve
                                              the oil or sewage without
Ban ocean dumping of sludge and               creating harmful by-products
hazardous dredged material                    (still under development)

Protect sensitive areas from
development, oil drilling, and                Require at least secondary
oil shipping                                  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
 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.
            How Would You Vote?

 Shouldwe 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.
 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 fro
      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
  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.
               Primary                                    Secondary

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

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

                                        Air pump

                                                                             Disposed of
                                                                             in landfill or
                                                                             ocean or
                                                                             applied to
                                                    Sludge drying bed        cropland,
                                                                             pasture, or
  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.
Dust Particles                      Odors
Particles of dried sludge           Odors may cause illness or
carry viruses and harmful           indicate presence of harmful gases.
bacteria that can be
inhaled, infect cuts or enter

                                   BUFFER           Exposure
                                     ZONE           Children may walk or
                                                    play in fertilized fields.

                                                    Livestock Poisoning
                                Sludge              Cows may die after grazing
                                                    on sludge-treated fields.
Harmful chemicals               Surface Runoff
and pathogens                   Harmful chemicals
may leach into                  and pathogens may
groundwater                     pollute nearby
and shallow wells.              streams,lakes, ponds,
                                and wetlands.
           How Would You Vote?

 Shouldwe ban the discharge of toxic
 chemicals into pipes leading to sewage
 treatment plants?
     a. No. Many small businesses and manufacturers
      can't afford tougher regulations.
     b. Yes. Dangerous wastes are still being
      released into sewage treatment plants.
  Reducing Water Pollution through
        Sewage Treatment
 Naturaland artificial wetlands and other
 ecological systems can be used to treat
     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.
            How Would You Vote?

 Should the U.S. Clean Water Act be
     a. No. Many farmers, ranchers and small
      businesses can't afford additional regulations.
     b. Yes. It will further reduce pollution and protect
      the environment and human health.
 Centralized  water treatment plants and
  watershed protection can provide safe
  drinking water for city dwellers in developed
 Simpler and cheaper ways can be used to
  purify drinking water for developing countries.
     Exposing water to heat and the sun’s UV rays for
      3 hours can kill infectious microbes.
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
     Allow rights to pollute if provider cannot afford to
            How Would You Vote?

 Should the U.S. Safe Drinking Water Act be
     a. No. Rural people, small businesses and
      manufacturers can't afford more regulations.
     b. Yes. Strengthening the Act would protect the
      environment and the health of millions of people.
      Is Bottled Water the Answer?
 Some bottled water is not as pure as tap
 water and costs much more.
    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.
            How Would You Vote?

 Should pollution standards be established for
 bottled water?
     a. No. Competition within the free market and the
      media would better solve the problems.
     b. Yes. Too many bottled waters contain bacteria
      and other dangerous contaminants.

            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
                    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.

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