Environmental Sciences: Towards a Sustainable Future Chapter 17

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Environmental Sciences Towards a Sustainable
Future Chapter 17

• Water Pollution and Prevention

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Water Pollutants and Trying to Copy Natures
Water Filters

• Major sources of water pollution
• Eutrophication causes and cures
• Human sewage management a pollutant of amount
  and type.

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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.

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Pollution Categories

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

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Pollution Categories

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

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Point and Nonpoint Sources of Pollution
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Types of Water Pollutants

• Pathogens
• Organic Wastes
• Chemical
• Sediments
• Nutrients

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Pathogens

• Disease-causing agents (Table 18.1)
• Safety measures
• purification of public water supply
• sanitary collection/treatment of sewage
• sanitary practices when processing food

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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.

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Chemical Pollutants

• Inorganic chemicals
• Heavy metals, acids, road salts
• Organic chemicals
• Petroleum, pesticides, detergents

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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

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Aquatic Plant Life

• Benthic plants
• Emergent vegetation
• Submerged aquatic vegetation (SAVs)
• Phytoplankton
• Green filamentous and single cell
• Bluegreen single cell
• Diatoms single cell

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Nutrient Enrichment

• Oligotrophic nutrient-poor water
• Eutrophic nutrient-rich water

What kind of plants would dominate in
oligotrophic and eutrophic conditions?
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Eutrophication

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

Oligotrophic
Eutrophic
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Eutrophic or Oligotrophic?

• High dissolved O2
• Deep light penetration
• High phytoplankton

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Eutrophic or Oligotrophic?

• Turbid waters
• High species diversity
• Good recreational qualities
• High detritus decomposition

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Eutrophic or Oligotrophic?

• Low bacteria decomposition
• Benthic plants
• Warm water
• High nutrient concentration
• BOD
• High sediments

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Natural Vs. Cultural Eutrophication

• Natural eutrophication
• aquatic succession
• occurs over several hundreds of years
• Cultural eutrophication
• driven by human activities
• occurs rapidly

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Combating Eutrophication

• Attack the symptoms
• Chemical treatment
• Aeration
• Harvesting aquatic weeds
• Drawing water down

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Combating Eutrophication

• Getting at root cause
• Controlling point sources
• Controlling nonpoint sources

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Controlling Point Sources

• Ban phosphate detergents
• Sewage-treatment improvements

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Controlling Nonpoint Sources

• Difficult to address runoff pollutants
• Urban
• Agricultural fields
• Deforested woodlands
• Overgrazed pastures
• Best Management Practices (BMP)

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Collecting Ponds
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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

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Match Technology With Removal Function
Technology Removal Function
Bar Screen Particulate organics
Grit Screen Dissolved organics
Primary Treatment Dissolved inorganics
Secondary Treatment Large or small debris
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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

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Biological Nutrient Removal
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Sludge Treatment

• Anaerobic digestion
• Composting
• Pasteurization

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Alternative Treatment Systems

• Individual septic systems
• Wastewater effluent irrigation
• Reconstructed wetland systems
• Beaumont, TX
• The waterless toilet

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Septic Tank Treatment

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