Environmental Science: Toward a Sustainable Future Richard T. Wright

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

10. 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.

11. Testing Water for Sewage Fecal Coliform Test

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

13. 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

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

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

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

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

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

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

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

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

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

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

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

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

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

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

28. 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

29. 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

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

31. 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

32. Removing Pollutants from Sewage: Match Technology with Function

33. Trickling Filters for Secondary Treatment

34. Trickling Filters for Secondary Treatment

35. 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

36. Sludge Treatment • Anaerobic digestion • Composting • Pasteurization

37. Treatment of Sludge Methane Humus

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

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

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

41. End of Chapter 17