Transcript WFSC 420 Lesson 11

Environmental
Science: Toward a
Sustainable Future
Chapter
17
Richard
T. Wright
Water Pollution and Its
Prevention
Adams
PPT by Clark E.
Water Pollution and Its
Prevention
• Water pollution
• Eutrophication
• Sewage management and
treatment
• Public policy
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.”
Water Pollution
• Pollution essentials
• Water pollution: sources, types,
criteria
Pollution Categories
• Air
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Particulates
Acid-forming compounds
Photochemical smog
CO2
CFCs
Pollution Categories
• Water and land
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Nutrient oversupply
Solid wastes
Toxic chemicals
Pesticides/herbicides
Nuclear waste
Water Pollution Types
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Pathogens
Organic Wastes
Chemical
Sediments
Nutrients
Pathogens Carried by
Sewage
• Disease-causing agents (Table
17.1)
• Safety measures
• Purification of public water supply
• Sanitary collection/treatment of
sewage
• Sanitary practices when
processing food
Organic Wastes
• Dissolved oxygen (DO) in the
water is depleted during
decomposition of organic
wastes.
• Water quality test
• Biochemical oxygen demand
(BOD): measure of the
amount of organic material.
Testing Water for
Sewage
Fecal Coliform Test
Chemical Pollutants
• Inorganic chemicals
• Heavy metals, acids, road
salts
• Organic chemicals
• Petroleum, pesticides,
detergents
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
Eutrophication
• Different kinds of aquatic plants
• The impact of nutrient
enrichment
• Combating eutrophication
Different Kinds of
Aquatic Plants
• Benthic plants
• Emergent vegetation
• Submerged aquatic vegetation
(SAV)
Different Kinds of
Aquatic Plants
• Phytoplankton
• Green filamentous and single
cell
• Blue-green single cell
• Diatoms single cell
The Impacts of Nutrient
Enrichment
• Oligotrophic: nutrient-poor
water
• Eutrophic: nutrient-rich water
What kind of plants would dominate in
oligotrophic vs. eutrophic conditions?
Eutrophication
Oligotrophic
Eutrophic
• As nutrients
are added from
pollution, an
oligotrophic
condition
rapidly
becomes
eutrophic.
Eutrophic or
Oligotrophic?
• High dissolved O2
• Deep light penetration
• High phytoplankton
Eutrophic or
Oligotrophic?
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Turbid waters
High species diversity
Good recreational qualities
High detritus decomposition
Eutrophic or
Oligotrophic?
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Low bacteria decomposition
Benthic plants
Warm water
High nutrient concentration
BOD
High sediments
Natural and Cultural
Eutrophication
• Natural eutrophication
• aquatic succession
• occurs over several hundreds of
years
• Cultural eutrophication
• driven by human activities
• occurs rapidly
Combating
Eutrophication
• Attack the symptoms
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Chemical treatment
Aeration
Harvesting aquatic weeds
Drawing water down
Combating
Eutrophication
• Getting at root cause
• Controlling point sources
• Controlling nonpoint sources
Controlling Point
Sources
• Ban phosphate detergents
• Sewage-treatment
improvements
Controlling Nonpoint
Sources
• Difficult to address runoff
pollutants
• Urban
• Agricultural fields
• Deforested woodlands
• Overgrazed pastures
Controlling Nonpoint
Sources
• Best Management Practices
(BMP): Table 17-2
• Agriculture
• Construction
• Urban
Sewage Management
and Treatment
• Development of sewage
collection and treatment
systems
• The pollutants in raw sewage
• Removing the pollutants from
sewage
• Treatment of sludge
• Alternative treatment systems
Development of Sewage
Collection and Treatment
Systems
• Storm drains for collecting
runoff from precipitation
• Sanitary sewers to receive all
the wastewater from sinks,
tubs, and toilets
Development of Sewage
Collection and Treatment
Systems
• Through the 1970s sewage was
discharged directly into
waterways
• Clean Water Act of 1972
Pollutants in Raw
Sewage
• 99.9% water to 0.1% waste
• Pollutants in sewage are:
• Debris and grit
• Particulate organic material
• Colloidal and dissolved organic
material
• Dissolved inorganic material
Removing Pollutants from
Sewage: Match
Technology
Technologywith Function
Function
Bar Screen
Grit Screen
Particulate
organics
Dissolved organics
Primary Treatment Dissolved
inorganics
Secondary
Treatment
Large or small
debris
Trickling Filters for
Secondary Treatment
Trickling Filters for
Secondary Treatment
Biological Nutrient
Removal
• Activated sludge: 3 zones
• Conversion of NH4 to NO3
• NO3 converted to N gas and
released
• PO4 taken up by bacteria and
released with excess sludge
Sludge Treatment
• Anaerobic digestion
• Composting
• Pasteurization
Treatment of Sludge
Methane
Humus
Alternative Treatment
Systems
• Individual septic systems
• Wastewater effluent irrigation
• Reconstructed wetland systems
• Beaumont, TX
• The waterless toilet
Septic Tank Treatment
• Aerobic
digestion of
solids in septic
tank
• Flow of liquids
into drain field
for evaporation,
infiltration, or
irrigation
Public Policy
• What was the legislative
milestone in protecting natural
waters and water supplies for
each of the acts listed in Table
17-3?
End of Chapter 17