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

2. Water Pollution and Its Prevention: Objectives • 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

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

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

8. Water Pollution Source

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

10. 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

12. 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.

13. Testing Water for Sewage Fecal Coliform Test

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

15. 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

17. Eutrophication: Objectives • Different kinds of aquatic plants • The impact of nutrient enrichment • Combating eutrophication

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

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

21. The Impacts of Nutrient Enrichment • Oligotrophic: nutrient-poor water • Eutrophic: nutrient-rich water

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

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

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

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

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

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

29. Collecting Pond for Dairy-Barn Washings

30. 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

31. 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

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

33. 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

35. Trickling Filters for Secondary Treatment

36. Biological Nutrient Removal • Activated sludge • Conversion of NH4 to NO3 • NO3 converted to N gas and released • PO4 taken up by bacteria and released with excess sludge

38. Sludge Treatment • Anaerobic digestion • Composting • Pasteurization

39. Treatment of Sludge Methane Humus

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

41. Dewatering Treated Sludge

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

43. End of Chapter 17