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Urban Water Quality

Urban Water Quality. Water Quality. Pollution - any departure from “purity” What is “purity”? Characteristics of water Is drinking water “pure”?. Water Quality.

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Urban Water Quality

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  1. Urban Water Quality

  2. Water Quality • Pollution - any departure from “purity” • What is “purity”? • Characteristics of water • Is drinking water “pure”?

  3. Water Quality • Pure Water - in the context of water pollution, a state of water in which no substance is present in sufficient concentration to prevent the water from being used for the purposes thought of as “normal”

  4. Water Quality • “Normal” uses of water? • Recreation • Public water supply • Aquatic habitats • Agriculture • Industry

  5. Water Quality • Water Pollutant - any substance that prevents the “normal” use of water • “Normal” implies a value judgement and depends on the particular use

  6. Water Quality • Water Quality - the physical and chemical characteristics of water • Unrelated to the particular use in that no value judgement is assigned

  7. Water Quality - Classification of Water Pollutants • Signs of water pollution? • Bad tasting drinking water • Masses of aquatic weeds • Disgusting odors • Decreasing fish populations • Floating oil and raw sewage

  8. Water Quality - Classification of Water Pollutants • Classification of water pollutants • Oxygen-demanding wastes (ODW) • Pathogenic organisms • Plant nutrients • Synthetic organic compounds (SOCs) • Oil • Sediments • Heat

  9. Water Quality - Classification of Water Pollutants • Oxygen-Demanding Wastes (ODW) • Dissolved Oxygen • Aquatic organisms require oxygen for cellular respiration • Dissolved oxygen (DO) is often a limiting factor for survival of aquatic organisms

  10. Water Quality - Classification of Water Pollutants • ODW • Dissolved Oxygen • Factors that control DO levels: • Water temperature • Elevation above sea level • Degree of turbulence • Stream channel geometry • Density of aquatic plants

  11. Water Quality - Classification of Water Pollutants • ODW • Dissolved Oxygen • Water Temperature • DO decreases with increasing water temperature • Elevation Above Sea Level • DO decreases with increasing elevation

  12. Water Quality - Classification of Water Pollutants • ODW • Dissolved Oxygen • Turbulence • DO increases with increasing turbulence caused by waterfalls, rapids, etc • Stream Channel Geometry • Wide,shallow channel has greater DO than narrow, deep channel

  13. Water Quality - Classification of Water Pollutants • ODW • Organic substances that cause depletion or removal of DO • Food source for aquatic bacteria • DO is removed as bacteria feed on ODW

  14. Water Quality - Classification of Water Pollutants • ODW • Sources of ODW • Sewage • Paper mills • Food processing • Slaughterhouses

  15. Water Quality - Classification of Water Pollutants • ODW • Biochemical Oxygen Demand- the amount of dissolved oxygen that bacteria require to decompose ODW in a given volume of water

  16. Water Quality - Classification of Water Pollutants • ODW • Biochemical Oxygen Demand (BOD) • Measurement • 5-day test • Incubation at 20 degrees C • BOD = DO (day 0) - DO (day 5)

  17. Water Quality - Classification of Water Pollutants • ODW • Biochemical Oxygen Demand (BOD) • Characteristic BOD Levels • Untreated Sewage 100-400 mg/L • Feedlots 100-10,000 mg/L • Pure Water 1 mg/L

  18. Water Quality - Classification of Water Pollutants • ODW • Environmental Impacts of low DO • Disappearance of plant and animal life • Shift from aerobic to anaerobic conditions • “Oxygen Sag”

  19. Water Quality - Classification of Water Pollutants • Pathogenic Organisms • Types of pathogens: • Viruses • Bacteria • Protozoa (unicellular) • Parasitic worms

  20. Water Quality - Classification of Water Pollutants • Pathogenic Organisms • Diseases caused by water-borne pathogens: • Amoebic Dysentery • Bacterial Dysentery • Typhoid fever • Cholera • Hepatitis • Schistosomiasis

  21. Water Quality - Classification of Water Pollutants • Pathogenic Organisms • Sources of body wastes: • Malfunctioning septic tanks, cesspools • Untreated sewage • Waste discharges from boats and ships • Meat processing plants • Swimmers and hikers

  22. Water Quality - Classification of Water Pollutants • Pathogenic Organisms • Testing for pathogenic organisms • Coliform bacteria • Live in large intestines of warm-blooded animals (even Uncle Monty) and absorb nutrients from their surroundings

  23. Water Quality - Classification of Water Pollutants • Plant Nutrients • Plants require 15-20 nutrients for growth: • Carbon • Nitrogen • Phosphorus • Potassium • Sulfur

  24. Water Quality - Classification of Water Pollutants • Plant Nutrients • Nitrogen and phosphorus are limiting nutrients for plant growth • Eutrophication - the natural enrichment of water with plant nutrients

  25. Water Quality - Classification of Water Pollutants • Plant Nutrients • Eutrophic Ecosystem - ecosystems that are relatively high in fertility and biological productivity • Oligotrophic Ecosystem - ecosystems that are relatively low in fertility and biological productivity

  26. Water Quality - Classification of Water Pollutants • Plant Nutrients • Cultural Eutrophication - accelerated eutrophication caused by human activities

  27. Water Quality - Classification of Water Pollutants • Plant Nutrients • Signs and effects of cultural eutrophication: • Dense growth of rooted plants • Increased growth of blue-green algae • Increased populations of trash fish • Foamy layers on surface of water

  28. Water Quality - Classification of Water Pollutants • Plant Nutrients • Sources of nutrients responsible for cultural cultural eutrophication: • Domestic Sewage • Urban Runoff • Industrial Sources • Agricultural Sources

  29. Water Quality - Classification of Water Pollutants • Plant Nutrients • Management practices to minimize cultural eutrophication: • Two types of water pollution sources in a watershed: • Point Source • Non-Point Source Pollution

  30. Water Quality - Classification of Water Pollutants • Plant Nutrients • Management practices to minimize cultural eutrophication: • Nutrient management • Determine point and nonpoint sources of nutrients and the size of each source • On-site treatment of nutrients • Rate and timing of nutrient application

  31. Water Quality - Classification of Water Pollutants • Synthetic Organic Compounds (SOCs) • Examples: • Fuels • Plastics • Pesticides • Fertilizers • Food additives • Pharmaceuticals

  32. Water Quality - Classification of Water Pollutants • Synthetic Organic Compounds (SOCs) • Pesticides • Environmental Impacts • Bioaccumulation • Interference with reproduction • Birth Defects • Reduced biodiversity and productivity • Tumors and convulsions

  33. Water Quality - Classification of Water Pollutants • Synthetic Organic Compounds (SOCs) • Oil (Hydrocarbons) • Sources • Impervious surfaces • Oil leaks • Auto emissions • Improper disposal of waste oil

  34. Water Quality - Classification of Water Pollutants • Synthetic Organic Compounds (SOCs) • Oil (Hydrocarbons) • Environmental Impacts • Degrade appearance of water surfaces • Limit air exchange between atmosphere and water • Lowered DO levels • Increased BOD • Impair habitat • Reduced biodiversity • Death

  35. Water Quality - Classification of Water Pollutants • Sediment • Most common of the nonpoint source pollutants • Sediment load in waterways increases with increasing urbanization and landuse intensity

  36. Water Quality - Classification of Water Pollutants • Sediment • Factors controlling sediment loss: • Chemical and physical characteristics of the soil • Slope steepness • Type and density of vegetation cover • Rainfall

  37. Water Quality - Classification of Water Pollutants • Sediment • Environmental Impacts • Filling of channels and harbors with sediment • Decreased biodiversity of aquatic animals • Increased turbidity

  38. Water Quality - Classification of Water Pollutants • Heat (Thermal Pollution) • Sources • Cooling water in industrial processes • Natural heating by sunlight • Environmental Impacts • Decreased DO • Increased rates of chemical reactions • False temperature cues to aquatic life • Death to aquatic organisms

  39. Water Quality - Classification of Water Pollutants • Heat (Thermal Pollution) • Environmental Impacts • Decreased DO • “Thermal Blanket” • Warm water is less dense than cold water • Warm layer forms “blanket” over cooler, more dense water • Warm water cannot dissolve as much atmospheric oxygen as cooler water • Rate of exchange of oxygen between warm water and cooler water is very slow • Cooler water is “atmospherically unreplenished” • Death to aquatic organisms

  40. Water Quality - Classification of Water Pollutants • Heat (Thermal Pollution) • Environmental Impacts • Increased rates of chemical reactions • The rate of any chemical reactions approximately doubles with every 10C increase in temperature • In thermally polluted waters, fish require more DO because of increased respiration rates • Increased respiration occurs in response to higher water temperature

  41. Water Quality - Classification of Water Pollutants • Heat (Thermal Pollution) • Environmental Impacts • False temperature cues given to aquatic life • Fish spawn and migrate in response to temperature cues • Optimum temperature range for fish species

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