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water pollution WATER POLLUTION Chapter

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     Chapter 21
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
• How can we prevent and reduce
  surface water pollution?
• How safe is drinking water, and how
  can it be made safer?
• 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 sources of water pollution:
  – Agriculture
     • Sediment, fertilizer, pesticides, bacteria
  – Industries
     • Organic and inorganic chemicals
  – Mining
     • Eroded sediments and runoff of toxic chemicals
Types of Pollutants
• Disease-causing agents (infectious
  – Pathogens that cause disease
  – Ex. bacteria, viruses, protozoa, and
    parasitic worms
  – Source: human and animal wastes
Major Water Pollution Problems

• Exposure to infectious diseases
• Not having sufficient water for sanitation
Table 21-2, p. 495
Major Water Pollutants
and Their Effects

               • A fecal coliform
                 bacteria test is
                 used to indicate
                 the likely
                 presence of
                 bacteria in water.

                              Figure 21-2
Types of Pollutants

-Oxygen-demanding wastes
 - Organic wastes that can be decomposed by
   aerobic bacteria
 - Degrade water quality by depleting water of
   dissolved oxygen; reduction in aquatic
 - Source: animal waste, feedlots, etc.
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
Types of Pollutants cont.

• Water -soluble inorganic chemicals,
  – Examples are acids, salts, and
    compounds of toxic metals (lead and
  – Affected water is unfit to drink and is
    harmful to aquatic life.
  – Damages nervous system, liver, kidneys,
    skin cancer.
Types of Pollutants cont.
• Inorganic Plant Nutrients
  – Examples include water-soluble nitrates and
  – Causes overgrowth of algae which leads to
    the depletion of dissolved oxygen and the
    death of fish
  – Sources- runoff from fertilizers, manure
Types of Pollutants cont.

• Organic chemicals
• Examples include gasoline, oil,
  plastics, pesticides, cleaning solvents,
  detergents, medicines
• Threaten human and aquatic life;
  impacts nervous system. Can cause
  cancer in humans.
Types of Pollutants cont.

• Sediment/ Suspended Matter
 – Biggest class
 – Examples include insoluble particles
   of soil and other solids released by
 – Sediments cloud water and disrupt
   aquatic food webs.
Types of Pollutants cont.
• Thermal pollution
  – Caused by the heat absorbed by the water
    used to cool nuclear power plants. This
    water is returned to natural environment
  – Lowers dissolved oxygen levels
  – Causes an abrupt change in temperature-
    thermal shock.
Types of Pollutants cont.

• Genetic pollution
  – Occurs when a nonnative species is
    introduced into an aquatic system
  – Examples include salmon escaping
    from fish farms, and zebra mussels
    infiltrating the Great Lakes.

• 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
                • Water in many of
                 central China's
                 rivers are
                 greenish black
                 from uncontrolled
                 pollution by
                 thousands of
                              Figure 21-5
• 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

• Dilution and decay of degradable,
 oxygen-demanding wastes and heat in
 a stream.                      Figure 21-4
 What is BOD?
• Biological Oxygen
 Demand (BOD) is the      BOD      Water Quality
 amount of dissolved
                          1-2        Very Good
 oxygen needed by
 aerobic decomposers      3-5        Moderate
 to break down the        6-9      Fairly Polluted
 organic materials in a   10+      Very Polluted
 certain volume of
 water over a 5-day
 incubation period at
 20°C (68°F)
BOD Effects on Water

All streams have some capability to degrade organic waste.
Problems occur when stream is overloaded with biochemical
oxygen-demanding waste.
Detecting Pollutants
• Chemical Analysis- used to determine the
    presence and concentrations of most water
•   Living Organisms- used as an indicator
    species to monitor water pollution. Ex.
    Filter-feeding mussels, Mayflies
•   Computer Models- used to find complex
    inputs and interactions that couldn’t be
    determined through chemical or biological
• It can take hundreds to thousand of
 years for contaminated groundwater to
 cleanse itself of degradable wastes.
  – Nondegradable wastes (toxic lead, arsenic,
    fluoride) 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                      Fig. 21-8, p. 502
• 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.
Case Study: Arsenic in
Groundwater - a Natural
• 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
  – Mostly in Bangladesh, China, and West
          Case Study: W&G Wells
          Woburn, Massachusetts

• Movie- “Civil Action” based on this.
• Involved the contamination of the wells
  G & H were two municipal wells
  developed in 1964 and 1967 to
  supplement the water supply of the
  City of Woburn.
• Groundwater was contaminated with
  VOCs, heavy metals (copper,
  chromium, lead, mercury, arsenic), etc.
Case Study: W&G Wells

• 1979, city police discovered drums of
  industrial waste.
• Responsible party: industrial
  properties operated by W.R. Grace.
  Eventually settled for $18 million.
• Cancers (lung, leukemia) occurred in
• Designated as a SUPERFUND SITE
  and estimated cleanup cost is $25.7
                             Groundwater Pollution

                    Prevention                       Cleanup

Find substitutes for toxic                     Pump to surface, clean,
chemicals                                      and return to aquifer
Keep toxic chemicals out of the                (very expensive)
Install monitoring wells near
landfills and underground tanks                Inject microorganisms to clean
                                               up contamination (less
Require leak detectors on                      expensive but still costly)
underground tanks
Ban hazardous waste disposal                   Pump nanoparticles of
in landfills and injection wells               inorganic compounds to
                                               remove pollutants (may be the
Store harmful liquids in                       cheapest, easiest, and most
aboveground tanks with leak                    effective method but is still
detection and collection systems               being developed)
• Dilution of pollutants in lakes is less
  effective than in most streams because most
  lake water is not mixed well and has little
  – 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
  – 85% of large lakes near major population
                                       Nitrogen compounds
                                        produced by cars
                                           and factories
           Discharge of untreated
              municipal sewage
         (nitrates and phosphates)

                                                                    Natural runoff
                                      Discharge of                  (nitrates and
                                        detergents                  phosphates)
                                      ( phosphates)                                   Inorganic fertilizer runoff
                                                                                     (nitrates and phosphates)
                                                                                            Manure runoff
                                                                                            from feedlots
   Discharge of treated                                                                (nitrates, phosphates,
    municipal sewage                                                                          ammonia)
(primary and secondary
        treatment:                                                                        Runoff from streets,
nitrates and phosphates)                         Lake ecosystem                         lawns, and construction
                                                nutrient overload                          lots (nitrates and
                                                and breakdown of                             phosphates)
                                                 chemical cycling
       Dissolving of                                                                       Runoff and erosion
      nitrogen oxides                                                                       (from cultivation,
(from internal combustion                                                                 mining, construction,
   engines and furnaces)                                                                   and poor land use)

                                     Lake Pollution

• Contain ~95% of all fresh surface
  water in the U.S.
• Pollution: nonpoint and point sources
• 1960s: cultural eutrophication- Lake
  Erie hit the hardest- it’s the
• Since 1970s some improvements in all
  Great Lakes due to upgraded
  wastewater treatment plants, bans on

                     Nipigon Bay
                 Thunder Bay          Jackfish Bay

        Silver Bay
                                                     St. Mary’s R.                                 St. Lawrence R.
                                                                       Spanish R.
St. Louis R.
                               MICHIGAN                                      Penetary Bay

               WISCONSIN                                                            Sturgeon Bay

                                              MICHIGAN            Saginaw
                                                        Saginaw R.
                                                                    Bay Grand R.            Niagara Falls NEW        YORK
MINNESOTA                                                  System                           Niagara R.
                                                       St. Clair R. Thames R.             Buffalo R.
                                                      Detroit R.
                                                      Rouge R.
                                                      Raisin R.                Ashtabula R.
    IOWA                                               Maumee R.             Cuyahoga R. PENNSYLVANIA
                                                                           Rocky R.
                                                                  Black R.
                                           INDIANA                   OHIO

                         Great Lakes drainage basin
                         Most polluted areas, according to the Great Lakes Water Quality Board
                         “Hot spots” of toxic concentrations in water and sediments
                         Eutrophic areas
                                                 "Crying Indian" PSA

Harmful algae on the shore
of Catawaba Island, Ohio.
(Credit: Image courtesy of NOAA)

                                   Eutrophication of Lake Erie
Preventing Lake Pollution
• Advanced waste        • Land –use control to
    treatment               reduce nutrient
•   Bans or limits on       runoff
    phosphates in       •   Bans on certain
    household               pesticides
•   Soil conservation
Lake Cleanup Methods
• Dredging bottom       • Pumping air through
    sediments               lakes and reservoirs
•   Removing excess         to avoid oxygen
    weeds                   depletion
•   Controlling         •   Remove excess
    undesirable plant       nutrient buildup
    growth with
    herbicides and
Pollution by Heat
• Thermal Shock- large inputs of heated
    water from one or more plants using the
    same lake or slow moving stream lower
    dissolved oxygen content by decreasing the
    solubility of oxygen in water
•   Thermal Shock- the effect of sharp changes
    in water temperature.
•   Thermal Enrichment- beneficial effects in an
    aquatic ecosystem from a rise in water
Controlling Thermal Pollution
 • Using/wasting less
 •   Limiting the amount
     of heated water
     discharged into a
     body of water
 •   Returning the heated
     waster some distance
     away from the shore
 •   Transferring the heat
     from the water to the
     atmosphere by means
     of cooling towers
 •   Discharge the heated

• 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
  – 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.
Pollutants in the Ocean
• Dredge Spoils-
  – Materials scraped from the bottoms of harbors
    and streams to maintain shipping channels.
  – They are often contaminated with high levels of
    toxic substances that have settled out of the
  – Still dumped legally in many countries by barges
    and ships.
• Sewage Sludge
  – A gooey, mud-like, mixture of toxic chemicals,
    infectious agents, and settled solids removed
    from wastewater at sewage treatment plants.
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

• Harmful algal blooms (HAB) are
 caused by explosive growth of
 harmful algae from sewage and
 agricultural runoff.              Figure 21-11
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.
                    This is called
                    the “Dead 21-A
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
                             Figure 21-12
Has anything been done?
• 50 countries with at least 80% of the
  world’s merchant fleet have agreed not
  to dump sewage and garbage at sea,
  but this agreement is difficult to
  enforce and is often violated
• London Dumping Convention of 1972-
  100 countries agreed not to dump
  highly toxic pollutants and high-level
  radioactive wastes in the open sea
  beyond the boundaries of their national

• 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
              drilling rigs
              can be
              devastating to
              marine life
              diving birds, 21-13
Oil and the Ocean cont.
• The effects of oil on ocean ecosystems
  depend on a number of factors: type of
  oil, amount released, distance of
  release from shore, time of year,
  weather conditions, average water
  temperature, and ocean currents.
• Spills can result in the death of
  numerous aquatic organisms.
Cleaning Up Oil Spills

• Mechanical Methods:
  – Floating booms to contain the oil spills or
    keep it from reaching sensitive areas
  – Skimmer boats to vacuum up some of the
    oil into collection barges
  – Absorbent pads or large feather-filled
    pillows to soak up oil on beaches or in
    shallow water.
Cleaning Up Oil Spills cont.

• Chemical Methods:
  – Coagulating agents to cause floating
    oil to clump together for easier
    pickup or sink to the bottom where it
    will do less harm
  – Dispersing agents to break up oil
Cleaning Up Oil Spills cont.

• Fire can burn off floating oil, but this
  method causes more harm than good
  (air pollution).
• Natural Action:
  – Wind and waves will mix oil with water
  – Bacteria will biodegrade some of the oil
  Gulf Oil Spill

                                   Burning off surface oil

Deepwater Horizon rig in flames,
last April.                                                  Seabird caught in the oil slick
                                                             on a beach on Louisiana's
                                                             East Grand Terre Island
         Graphic shows efforts to reduce effects of oil spill
Oil Pollution Act
• It has strengthened the government’s ability to prevent and
    respond to catastrophic oil spills.
•   It provides the money and resources necessary to respond to
    oil spills. A trust fund financed by a tax on oil is available to
    clean up spills when the responsible party is incapable or
    unwilling to do so (the largest source of income for the fund
    is from the 5-cents-per-barrel tax on imported and domestic
•   Requires oil storage facilities and vessels to submit to the
    federal government plans detailing how they will respond to
    large discharges.
•   The OPA also requires the development of Area Contingency
    Plans to prepare and plan for oil spill response on a regional
•   The Oil Pollution Act caused a major restructuring of the oil
                            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
                                                                   Fig. 21-14, p. 509
The Clean Water Act
• Reduces direct pollutant discharges into
•   Finances municipal wastewater treatment
•   Manages polluted runoff
    – Goal is to restore and maintain the chemical, physical, and
      biological integrity of the nation's waters
• Originally focused on regulating discharges from
    point source facilities and not non-point sources
The Clean Water Act
• Starting in the late 1980s, efforts to address polluted
    runoff have increased significantly.
•   Evolution of CWA programs has also included shift from
    a program-by-program, source-by-source, pollutant-by-
    pollutant approach to more holistic watershed-based
•   Emphasis now on protecting healthy waters and
    restoring impaired ones.

• The key to reducing nonpoint pollution
 – most of it from agriculture – is to
 prevent it from reaching bodies of
  – Farmers can reduce runoff by planting
    buffers and locating feedlots away from
    steeply sloped land, flood zones, and
    surface water.
The Nitrogen Cycle:
Bacteria in Action

          ml                                         Figure 3-29
Reducing Water Pollution
through Sewage Treatment

 • Septic tanks and various levels of
  sewage treatment can reduce point-
  source water pollution.         Figure 21-15
Reducing Water Pollution
Through Sewage Treatment
• Raw sewage reaching a municipal
 sewage treatment plant typically
  – 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
Wastewater Treatment Plants
• Wastewater entering a plant is ~99.94
  percent water, only 0.06 percent of the
  wastewater is suspended solid
• Facility uses a multi-stage process to
  process the wastewater.
• Goal is to reduce or remove organic
  matter, solids, nutrients, disease-
  causing organisms and other pollutants
  from wastewater.
Municipal Sewage Treatment
• Primary: physically
 separates large solids from
 the waste stream
  – Metal grating: removes large
  – Moving screen: filters out
    smaller items
  – Grit tank: allows sand and             Bar Screen
    sediment to settle
  – Primary sedimentation tank:    Bar Screen: The Movie
    about half the suspended
    organic solids settle out as
Municipal Sewage Treatment
• Secondary Treatment: biological
 degradation of dissolved organic
  – Aeration tank: waste aerobically
    decomposed by bacteria
  – Water flows from top of the tank and
    sludge is removed from the bottom
  – Sludge is disposed in sanitary landfill
  – Effluent treated with chlorine, UV light, or
    ozone to kill harmful bacteria before being
    released to a nearby waterway
Reducing Water Pollution
through Sewage Treatment

• Advanced or tertiary sewage
  – Uses series of chemical and physical
    processes to remove specific pollutants
    left (especially nitrates and phosphates).
  – Tertiary Wastewater Treatment
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

• Primary and Secondary sewage
 treatment. Wichita Falls Waste Water Facility
                                                 Figure 21-16
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.

                                                                              Fig. 21-17, p. 513
• Centralized water treatment plants and
  watershed protection can provide safe
  drinking water for city dwellers in
  developed countries.
• Simpler and cheaper ways can be used
  to purify drinking water for developing
  – Exposing water to heat and the sun’s UV
    rays for 3 hours can kill infectious
Using Laws to Protect
Drinking Water
• While most developed countries have
  drinking water quality standards and
  laws, most developing countries do
• 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 standards.
• 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.
Clean Water Act
• Purpose is to restore and maintain chemical,
    physical and biological integrity of the
    nation’s waters
•   Regulates everything from urban runoff and
    municipal sewage treatment to wetland
•   Requires discharge permits and best
    practicable control technology (BPT)
•   Sets national goal of best available,
    economically achievable technology for
    toxic substances and zero discharge for 126
    priority toxic pollutants

            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

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