Environmental Science Toward a Sustainable Future Richard T

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 n n Water pollution Eutrophication Sewage management and treatment Public policy

Pollution n 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. ”

Water Pollution n n Pollution essentials Water pollution: sources, types, criteria

Pollution Categories n Air q q q Particulates Acid-forming compounds Photochemical smog CO 2 CFCs

Pollution Categories n Water and land q q q Nutrient oversupply Solid wastes Toxic chemicals Pesticides/herbicides Nuclear waste

Water Pollution Source

Water Pollution Types n n n Pathogens Organic Wastes Chemical Sediments Nutrients

Pathogens Carried by Sewage n n Disease-causing agents (Table 17. 1) Safety measures q q q Purification of public water supply Sanitary collection/treatment of sewage Sanitary practices when processing food

Organic Wastes n n Dissolved oxygen (DO) in the water is depleted during decomposition of organic wastes. Water quality test q Biochemical oxygen demand (BOD): measure of the amount of organic material.

Testing Water for Sewage Fecal Coliform Test

Chemical Pollutants n n Inorganic chemicals q Heavy metals, acids, road salts Organic chemicals q Petroleum, pesticides, detergents

Effect of Sediments on Stream Ecology n n n Loss of hiding/resting places for small fish Attached aquatic organisms scoured from the rocks and sand Poor light penetration

Eutrophication n Different kinds of aquatic plants The impact of nutrient enrichment Combating eutrophication

Different Kinds of Aquatic Plants n Benthic plants Emergent vegetation q Submerged aquatic vegetation (SAV) q

Different Kinds of Aquatic Plants n Phytoplankton Green filamentous and single cell q Blue-green single cell q Diatoms single cell q

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

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

Eutrophic or Oligotrophic? n n n High dissolved O 2 Deep light penetration High phytoplankton

Eutrophic or Oligotrophic? n n Turbid waters High species diversity Good recreational qualities High detritus decomposition

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

Natural and Cultural Eutrophication n Natural eutrophication q q n aquatic succession occurs over several hundreds of years Cultural eutrophication q q driven by human activities occurs rapidly

Combating Eutrophication n Attack the symptoms q q Chemical treatment Aeration Harvesting aquatic weeds Drawing water down

Combating Eutrophication n Getting at root cause q q Controlling point sources Controlling nonpoint sources

Controlling Point Sources n n Ban phosphate detergents Sewage-treatment improvements

Controlling Nonpoint Sources n Difficult to address runoff pollutants Urban q Agricultural fields q Deforested woodlands q Overgrazed pastures q

Controlling Nonpoint Sources n Best Management Practices (BMP): Table 17 -2 Agriculture q Construction q Urban q

Collecting Pond for Dairy-Barn Washings

Sewage Management and Treatment n n n Development of sewage collection and treatment systems The pollutants in raw sewage Removing the pollutants from sewage Treatment of sludge Alternative treatment systems

Development of Sewage Collection and Treatment Systems n n Storm drains for collecting runoff from precipitation Sanitary sewers to receive all the wastewater from sinks, tubs, and toilets

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

Pollutants in Raw Sewage n n 99. 9% water to 0. 1% waste Pollutants in sewage are: q q Debris and grit Particulate organic material Colloidal and dissolved organic material Dissolved inorganic material

Removing Pollutants from Sewage: Match Technology with Function Technology Function Bar Screen Particulate organics Grit Screen Dissolved organics Primary Treatment Dissolved inorganics Secondary Treatment Large or small debris

Trickling Filters for Secondary Treatment

Trickling Filters for Secondary Treatment

Biological Nutrient Removal n n Activated sludge: 3 zones Conversion of NH 4 to NO 3 converted to N gas and released PO 4 taken up by bacteria and released with excess sludge

Sludge Treatment n n n Anaerobic digestion Composting Pasteurization

Treatment of Sludge Methane Humus

Alternative Treatment Systems n n n Individual septic systems Wastewater effluent irrigation Reconstructed wetland systems q n Beaumont, TX The waterless toilet

Dewatering Treated Sludge

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

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

End of Chapter 17