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Environmental Science: Toward a Sustainable Future Richard T. Wright

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Presentation on theme: "Environmental Science: Toward a Sustainable Future Richard T. Wright"— Presentation transcript:

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

2 Water Pollution and Its Prevention
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

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
Bar Screen Particulate organics Grit Screen Dissolved organics Primary Treatment Dissolved inorganics Secondary Treatment Large or small debris

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

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