Environmental Science: Toward a Sustainable Future Richard T. Wright

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Environmental Science Toward a
Sustainable Future Richard T. Wright
Chapter 17

• Water Pollution and Its Prevention

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Water Pollution and Its Prevention

• Chapter Sections
• 17.1 Water pollution
• 17.2 Eutrophication
• 17.3 Sewage management and treatment
• 17.4 Public policy

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Pollution

• Pollution the presence of a substance in the
  environment that because of its chemical
  composition or quantity prevents the functioning
  of natural processes and produces undesirable
  environmental and health effects. EPA

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17.1 Water Pollution

• Key Section Topics
• Pollution essentials
• Water pollution sources, types, criteria

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Pollution is an outcome of otherwise worthy human
endeavors.
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17.1 Water Pollution

• General strategy
• Identify the material causing the pollution--the
  undesirable change
• Identify the sources of the pollutants
• Develop and implement pollution control
  strategies to prevent the pollutants from
  entering the environment
• Develop and implement alternative means of
  meeting the need that do not produce the
  pollution by-productin other words, avoid the
  pollution altogether

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17.1 Pollution Categories

• Air
• Particulates
• Acid-forming compounds
• Photochemical smog
• CO2
• CFCs

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17.1 Pollution Categories

• Water and land
• Nutrient oversupply
• Solid wastes
• Toxic chemicals
• Pesticides/herbicides
• Nuclear waste

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17.1 Water Pollution Source
Point Sources are easier to identify, monitor,
and regulate. Ex. discharge from factories,
sewage systems, power plants
Nonpoint Sources are poorly defined and scattered
over broad areas. Ex. agricultural runoff,
storm-water drainage, air pollution washed to
earth
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17.1 Water Pollution Types

• Pathogens
• Organic Wastes
• Chemical
• Sediments
• Nutrients

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17.1 Pathogens Carried by Sewage

• Disease-causing agents (Table 17.1)
• Safety measures
• Purification and disinfection of public water
  supply with chlorine or other agents
• Sanitary collection and treatment of sewage
  wastes
• Sanitary practices when processing food
• Public education in personal and domestic hygiene
  practices

Cholera outbreak in Bangladesh Even after
symptoms of disease disappear, an infected person
or animal may still harbor the pathogen and act
as a carrier of disease.
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17.1 Pathogens Carried by Sewage

• Sanitation Good Medicine
• Good health is primarily a result of the
  prevention of disease through public-health
  measures
• Millennium Development Goal- to reduce by ½ the
  proportion of people without sustainable access
  to safe drinking water

There's virtually no sanitation system here in
Kabul, Afghanistan 2007
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17.1 Pathogens Carried by Sewage

• 2002 Johannesburg World Summit- to halve, by the
  year 2015, the proportion of people who do not
  have access to basic sanitation
• Over 1 billion people do not have access to sage
  drinking water
• 2 ½ billion people live in areas of poor or no
  sewage collection or treatment
• 3 million deaths (children under 5 years) each
  year traced to waterborne diseases

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17.1 Organic Wastes

• Dissolved oxygen (DO) in the water is
  depleted during decomposition of organic wastes.
  (human and animal wastes, leaves, grass
  clippings, trash)
• As bacteria and detritus feeders decompose
  organic matter in water, they consume oxygen gas
  dissolved in the water
• The amount of oxygen that water can hold in
  solution is severely limited
• DO in air 200,000 ppm
• DO in unpolluted cold water- 10 ppm
• DO in unpolluted warm water is even less
• Consider how low DO would be in polluted water (lt
  2-3 ppm fish, shellfish die)

Low Dissolved OxygenAlso called (LDO) or (DO),
refers to the volume of oxygen that is contained
in water. Oxygen enters the water by
photosynthesis of aquatic biota and by the
transfer of oxygen across the air-water
interface. When the oxygen level in the water
drops too low, the fish suffocate.
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17.1 Organic Wastes

• Water quality tests
• Biochemical oxygen demand (BOD) measure of the
  amount of organic material in water and how much
  oxygen is required to break it down.
• High BOD likely oxygen depletion
• Typical BOD value for raw sewage is 250 ppm
• DO of 10 ppm will be depleted if a moderate
  amount of sewage is added

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17.1 Testing Water for Sewage
Fecal Coliform Test

• A filter disk is placed in the filter apparatus
• A sample of water being tested in drawn through
  the filter and any bacteria present are entrapped
  on the disk.
• The disk is placed I a petri dish on a special
  medium that supports the growth of bacteria.
  Gives a special color to fecal E. coli bacteria.
  Incubated. Form colonies.
• E. coli bacteria, indicating sewage
  contamination, are seen as colonies with a
  metallic green sheen.

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17.1 Chemical Pollutants

• Water soluble inorganic chemicals
• Heavy metals (lead, mercury, nickel, cadmium)
• Acids from mine drainage (sulfuric and nitric
  acid)
• Road salts (sodium and calcium chlorides)

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17.1 Chemical Pollutants

• Organic chemicals
• petroleum (from oil spills and parking lot
  runoff)
• pesticides (from aerial spraying or farm runoff)
• detergents/cleaning solvents/PCBs

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17.1 Effect of Sediments on Stream Ecology

• Loss of hiding/resting places for small fish
• Attached aquatic organisms scoured from the rocks
  and sand
• Poor light penetration
• clay and humus are carried in suspension
• makes water muddy
• Clogging of animals gills and feeding structures

The Mexican axolotl salamander with external
gills.
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a) The ecosystem of a stream that is not
subjected to a large sediment bed load. b) The
changes that occur with large sediment
inputs. c) Platte River, Ne The sandbars
constitute bed load they shift and move with
high water, preventing reestablishment of aquatic
vegetation.
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17.1 Nutrients

• Organic nutrients
• Phosphorus and Nitrogen
• Stimulate undesirable plant growth in bodies of
  water
• Point sources- sewage outfalls
• Nonpoint sources- agricultural runoff, golf
  courses, storm drains

According to a Colorado University study,
nutrient run-off from farms and ranches is
driving frog infections and deformities.
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17.1 Water Quality Standards

• EPA has established the National Recommended
  Water Quality Criteria
• 158 chemical/substance pollutants
• Recommends concentrations for freshwater,
  saltwater, and human consumption
• Values given for CMC- criteria maximum
  concentration beyond which environmental impacts
  are expected
• Safe Drinking Water Act

Arsenic contamination CMC 340 ppb (ug/L) CCC 150
ppb (ug/L) in freshwater Drinking water MCL was
50 ppb (ug/L) (cancer rate 1 in 100)---now down
to 10 ppb (ug/L)
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17.2 Eutrophication

• Key Section Topics
• Different kinds of aquatic plants
• The impact of nutrient enrichment
• Combating eutrophication

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17.2 Different Kinds of Aquatic Plants

• Benthic plants (deep rooted)
• 2 kinds
• Emergent vegetation
• Grow with lower parts in water/upper parts
  emerging from the water
• Submerged aquatic vegetation (SAV)
• Grow totally under water
• Need clear water to allow photosynthesis
• Obtain mineral nutrients from bottom sediments

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17.2 Different Kinds of Aquatic Plants

• Phytoplankton
• Absorb nutrients directly from the water
• Low nutrients phytoplankton populations remain
  low
• High nutrients phytoplankton populations
  explode (bloom)

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17.2 Different Kinds of Aquatic Plants

• Phytoplankton

• Diatoms
• (unicellular)

Green (unicellular)
Blue-green bacteria (unicellular) Cyanobacteria

• Green (filamentous)

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17.2 The Impacts of Nutrient Enrichment

• Oligotrophic
• Nutrient-poor water Light penetrates deeply
• Watershed holds High DO
• nutrients well

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17.2 The Impacts of Nutrient Enrichment

• Eutrophic
• Nutrient-rich water Turbid water
• Heavy detritus Low DO

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17.2 Eutrophication

• As nutrients are added from pollution, an
  oligotrophic condition rapidly becomes eutrophic.

Oligotrophic
Eutrophic
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17.2 Eutrophic or Oligotrophic?

• 1. High dissolved O2
• 2. Deep light penetration
• 3. High phytoplankton
• 4. Turbid waters
• 5. High species diversity
• 6. Good recreational qualities

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17.2 Eutrophic or Oligotrophic?

• 7. High detritus decomposition
• 8. Low bacteria decomposition
• 9. Benthic plants
• 10. Warm water
• 11. High nutrient concentration
• 12. Low BOD
• 13. High sediments

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17.2 Eutrophic or Oligotrophic?

• 1. High dissolved O2 O
• 2. Deep light penetration O
• 3. High phytoplankton E
• 4. Turbid waters E
• 5. High species diversity O
• 6. Good recreational qualities O

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17.2 Eutrophic or Oligotrophic?

• 7. High detritus decomposition E
• 8. Low bacteria decomposition O
• 9. Benthic plants O
• 10. Warm water E
• 11. High nutrient concentration E
• 12. Low BOD O
• 13. High sediments E

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17.2 Natural and Cultural Eutrophication

• Natural eutrophication
• aquatic succession
• occurs over several hundreds of years

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17.2 Natural and Cultural Eutrophication

• Cultural eutrophication
• driven by human activities
• occurs rapidly

Runoff of N and P into stream. Oklahoma
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17.2 Combating Eutrophication

• Attack the symptoms
• Chemical treatment with herbicides
• Copper sulfate and diquat control phytoplanktons
• Fluridone, glyphosate, 2,4-D control emergent
  vegetation
• Can kill fish and aquatic animals
• Only cosmetic
• Artificial aeration
• High-pressure air pumps
• -bubbles dissolve directly into water
• Speeds up breakdown of detritus
• Improves water quality

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17.2 Combating Eutrophication

• Harvesting aquatic weeds
• Use commercial mechanical harvesters
• Hand removal
• Limited effect-roots left and plants grow back
  quickly
• Drawing water down
• Kills rooted aquatic plants along shoreline

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17.2 Combating Eutrophication

• Getting at root cause
• Reducing nutrients and sediments
• Phosphorus (phosphate PO4 3- )
• Ban on phosphate detergents
• Nitrogen (nitrate NO3 or ammonium NH4 )
• Controlling point sources
• Discharges from sewage-treatment plants
• National Pollutant Discharge Elimination System
  (NPDES ) must issue permit
• Controlling nonpoint sources
• Addressed in the 1987 Clean Water Act regulates
  Total Maximum Daily Loads of pollutants (TMDL)

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17.2 Controlling Nonpoint Sources

• Difficult to address runoff pollutants
• Urban
• Agricultural fields
• Deforested woodlands
• Overgrazed pastures

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17.2 Controlling Nonpoint Sources

• Best Management Practices (BMP) Table 17-2
• Agriculture
• Construction
• Urban

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17.2 Collecting Pond for Dairy-Barn Washings
(BMP)
Eutrophication can be avoided by collecting the
flushings in ponds from which both the water and
the nutrients may be recycled.
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17.3 Sewage Management and Treatment

• Key Section Topics
• Development of sewage collection and treatment
  systems
• The pollutants in raw sewage
• Removing the pollutants from sewage
• Treatment of sludge
• Alternative treatment systems

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17.3 Development of Sewage Collection and
Treatment Systems

• Before the late 1800s, human excrement was
  disposed of by using the outdoor privy
• In the late 1800s, Louis Pasteur showed that
  sewage-borne bacteria were responsible for many
  diseases
• Storm drains for collecting runoff from
  precipitation were already in use
• Sewers were tapped into storm drains to receive
  all the wastewater from sinks, tubs, and
  toiletseven through 1970s, all discharged
  directly into waterways
• Now we try to separate storm drains from sanitary
  sewers (CWA 1972)

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17.3 Pollutants in Raw Sewage

• Raw sewage (all wastewater) is approx. 1,000
  parts water for every 1 part waste ?99.9 water
  to 0.1 waste
• US daily raw sewage output 150-200
  gal/person/day
• Pollutants in sewage are
• Debris (trash) and grit (sand, gravel)
• Particulate organic material (fecal matter, food
  wastes, toilet paper)
• Colloidal and dissolved organic material
  (bacteria, urine, soap, detergent)
• Dissolved inorganic material (nitrogen,
  phosphorus)

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17.3 Removing Pollutants from Sewage
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17.3 Removing Pollutants from Sewage

• Preliminary Treatment (Removal of Debris and
  Grit)
• Screening out of debris with bar screen/burned in
  incinerator
• Settling of grit/taken to landfill
• Primary Treatment (Removal of Particulate Organic
  Material)
• Water flows through large tanks called primary
  clarifiers
• Particulate organic material settles to
  bottom/removed
• Fatty, oily materials skimmed from surface
• All materials removed ?raw sludge

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17.3 Removing Pollutants from Sewage

• Secondary Treatment (Removal of Colloidal and
  Dissolved Organic Material)
• Biological Treatment- uses natural decomposers
  and detritus feeders
• Feed on colloidal and dissolved organic material
• Aeration of water
• Trickling-filter system
• Water is sprinkled onto fist-sized
  rocks/percolates through rocks
• Organic matter is absorbed and digested by
  decomposers and detritus feeders and it trickles
  by

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17.3 Removing Pollutants from Sewage

• Aeration of water
• Activated-sludge system
• Water enters large tank/churned
• Activated-sludge added (detritus feeding
  organisms)
• Sent to secondary clarifier tank/organisms floc
  into clumps/settle out
• Organic material is oxidized to form carbon
  dioxide, water, and mineral nutrients that remain
  in the water solution

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17.3 Removing Pollutants from Sewage

• Biological Nutrient Removal-BNR (Dissolved
  Inorganic Material)

• Activated sludge Put into aeration tank with 3
  zones
• Zone 1 ? Bacteria added to organic matter ?
  Produce NH4
• Zone 3 ? Conversion of NH4 to NO3 ? Recycled to
  Zone 2
• Zone 2 ? NO3 converted to N gas and released
  (Denitrification)
• Zone 3 ? PO4 taken up by bacteria and released
  with excess sludge

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17.3 Removing Pollutants from Sewage

• Alternate Plan instead of BNR
• Pass effluent through a filter of lime
• Phosphate precipitates out as insoluble calcium
  phosphate
• OR treat with ferric chloride to produce ferric
  phosphate
• OR treat with an organic polymer which gives rise
  to floc
• Final Cleansing and Disinfection
• Final treatment with chlorine gas (harmful to
  animals) or Clorox (safer)
• Also used is Ozone gas which kills microorganisms
  and breaks down to form oxygen gas
  (expensive/explosive)
• Newest ? pass effluent through UV lights

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17.3 Sludge Treatment

• Still left with the Raw Sludge? particulate
  organic matter that settled out/floated to the
  surface during primary sewage treatment
• 97-98 water
• Contains pathogens
• Biologically hazardous
• Potentially organic fertilizer
• Treated 3 ways
• Anaerobic digestion
• Composting
• Pasteurization

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17.3 Sludge Treatment

• Treated 3 ways
• Anaerobic digestion- put into airtight tanks
  (sludge digesters) with anaerobic bacteria
• Produce carbon dioxide, water, and methane
  (Biogas)
• After 4-6 weeks, a nutrient-rich humuslike
  material is formed (Biosolid) or treated
  sludge/excellent organic fertilizer
• Dewatered to form a semi-solid sludge
  cake/disinfected/used as fertilizer
• Composting
• Raw sludge is mixed with wood chips to absorb
  water
• Decomposes to form humuslike material/treatment
  for soil
• Pasteurization
• Raw sludge is dewatered/dried in
  ovens/pasteurized with hear/sold as fertilizer
  (Milwaukee Beer IndustryMilorganite)

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Treatment of Sludge
Methane Humus
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17.3 Dewatering Treated Sludge
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17.3 Alternative Treatment Systems

• Many rural and suburban areas lie outside reach
  of municipal system and rely on
• Individual septic systems
• Wastewater flows into tank/organic material
  settles to bottom
• Acts as primary clarifier/waste flows into drain
  field /percolates into soil/digested by bacteria
• Wastewater effluent irrigation
• Ok if used to residential lawns/golf courses
• Bad if used on croplands/parasites/diseases
• Bad if put into waterways/eutrophication
• Reconstructed wetland systems
• Beaumont, TX/Orlando, Fla
• The waterless toilet

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17.3 Septic Tank Treatment

• Aerobic digestion of solids in septic tank
• Flow of liquids into drain field for evaporation,
  infiltration, or irrigation

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17.4 Public Policy

• What was the legislative milestone in protecting
  natural waters and water supplies for each of the
  acts listed in Table 17-3?
• Clean Water Act of 1972
• Required permits for all point-source discharges
  of pollutants
• Provided cities with billions of to build
  treatment plants
• Reauthorization long overdue/many problems

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End of Chapter 17