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Environmental Science: Toward a Sustainable Future Richard T. Wright

Environmental Science: Toward a Sustainable Future Richard T. Wright. Chapter 17. Water Pollution and Its Prevention PPT by Clark E. Adams. Water Pollution and Its Prevention. Water pollution Eutrophication Sewage management and treatment Public policy. Pollution.

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Environmental Science: Toward a Sustainable Future Richard T. Wright

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  1. Environmental Science: Toward a Sustainable FutureRichard T. Wright Chapter 17 Water Pollution and Its Prevention PPT by Clark E. Adams

  2. Water Pollution and Its Prevention • Water pollution • Eutrophication • Sewage management and treatment • Public policy

  3. 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.”

  4. Water Pollution • Pollution essentials • Water pollution: sources, types, criteria

  5. Pollution Categories • Air • Particulates • Acid-forming compounds • Photochemical smog • CO2 • CFCs

  6. Pollution Categories • Water and land • Nutrient oversupply • Solid wastes • Toxic chemicals • Pesticides/herbicides • Nuclear waste

  7. Water Pollution Types • Pathogens • Organic Wastes • Chemical • Sediments • Nutrients

  8. 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

  9. 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.

  10. Testing Water for Sewage Fecal Coliform Test

  11. Chemical Pollutants • Inorganic chemicals • Heavy metals, acids, road salts • Organic chemicals • Petroleum, pesticides, detergents

  12. 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

  13. Eutrophication • Different kinds of aquatic plants • The impact of nutrient enrichment • Combating eutrophication

  14. Different Kinds of Aquatic Plants • Benthic plants • Emergent vegetation • Submerged aquatic vegetation (SAV)

  15. Different Kinds of Aquatic Plants • Phytoplankton • Green filamentous and single cell • Blue-green single cell • Diatoms single cell

  16. The Impacts of Nutrient Enrichment • Oligotrophic: nutrient-poor water • Eutrophic: nutrient-rich water What kind of plants would dominate in oligotrophic vs. eutrophic conditions?

  17. Eutrophication • As nutrients are added from pollution, an oligotrophic condition rapidly becomes eutrophic. Oligotrophic Eutrophic

  18. Eutrophic or Oligotrophic? • High dissolved O2 • Deep light penetration • High phytoplankton

  19. Eutrophic or Oligotrophic? • Turbid waters • High species diversity • Good recreational qualities • High detritus decomposition

  20. Eutrophic or Oligotrophic? • Low bacteria decomposition • Benthic plants • Warm water • High nutrient concentration • BOD • High sediments

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

  22. Combating Eutrophication • Attack the symptoms • Chemical treatment • Aeration • Harvesting aquatic weeds • Drawing water down

  23. Combating Eutrophication • Getting at root cause • Controlling point sources • Controlling nonpoint sources

  24. Controlling Point Sources • Ban phosphate detergents • Sewage-treatment improvements

  25. Controlling Nonpoint Sources • Difficult to address runoff pollutants • Urban • Agricultural fields • Deforested woodlands • Overgrazed pastures

  26. Controlling Nonpoint Sources • Best Management Practices (BMP): Table 17-2 • Agriculture • Construction • Urban

  27. 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

  28. 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

  29. Development of Sewage Collection and Treatment Systems • Through the 1970s sewage was discharged directly into waterways • Clean Water Act of 1972

  30. 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

  31. Removing Pollutants from Sewage: Match Technology with Function

  32. Trickling Filters for Secondary Treatment

  33. Trickling Filters for Secondary Treatment

  34. 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

  35. Sludge Treatment • Anaerobic digestion • Composting • Pasteurization

  36. Treatment of Sludge Methane Humus

  37. Alternative Treatment Systems • Individual septic systems • Wastewater effluent irrigation • Reconstructed wetland systems • Beaumont, TX • The waterless toilet

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

  39. Public Policy • What was the legislative milestone in protecting natural waters and water supplies for each of the acts listed in Table 17-3?

  40. End of Chapter 17

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