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GECH 119 Water Quality

GECH 119 Water Quality. Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University. Water Quality Chapter Objectives. Properties of Water Water as a Solvent Water Treatment Water Pollution Wastewater Treatment. Water. Earth contains large quantities of water

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GECH 119 Water Quality

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  1. GECH 119Water Quality Dr. Ralph C. Gatrone Department of Chemistry and Physics Virginia State University

  2. Water QualityChapter Objectives • Properties of Water • Water as a Solvent • Water Treatment • Water Pollution • Wastewater Treatment

  3. Water • Earth contains large quantities of water • Life cannot exist without water • Large amounts of undrinkable water exist • Life cannot exist without water.

  4. Death due to Deprivation • No Food – death occurs in 3 weeks • No water – death occurs in 3 days • No air – death occurs in 3 minutes

  5. Water Loss Symptoms • < 5% (.5 to 2.5 qts) • thirsty, lethargic, irritable, weak, lost appetite, higher pulse • 6-10% (3 to 5 qts) • dizzy, headache, dry mouth, tingle in hands or feet, slurred speech, lack of coordination, trouble breathing, blurry vision • 11-15% (3.5 to 8 qts) • delirious, tongue swells, convulsions, hearing, vision, and feeling fail, skin shrivels, death

  6. DehydrationA Short Path to Death • If you sit in the sun when its about 100 degrees, you lose about 1 quart of sweat each hour!

  7. Water Cycle

  8. Key Terms in Water Cycle • Hydrologic cycle – water cycle • Water table – upper boundary of zone saturated with water • Groundwater – water beneath surface • Surface water – water in streams, rivers, and lakes • Aquifer – water bearing layer of soil • Subsides – soil compresses as water is removed

  9. Properties of Water • Small molecule • 2 Hydrogen atoms + 1 Oxygen atom • Liquid at room temperature • Most other small molecules are gases at room temperature • Density in solid state < liquid state • Most materials are more dense in solid state • Ice floats • Allows life to exist in liquid state beneath ice

  10. Properties of Water • Melting point = 0 oC • Boiling point = 100 oC • Water • only molecule on Earth • exists as a solid, • liquid, and • gas at ambient pressures and temperatures.

  11. Observations • Water in summer is cooler than surrounding air • Water in winter is warmer than surrounding air • Why? • Property called: Specific Heat

  12. Specific Heat • Sun warms water in lake • It takes a long time • to heat a large amount of water • Winter air cools water in lake • It takes a long time • to cool a large amount of water • Temperature of water changes more slowly than the temperature of the air.

  13. Specific Heat • Specific heat • amount of heat needed to raise the temperature of 1 gram of a substance (water) by 1 degree. • Value for water is • 4.184J per gram per degree • Physical constant: specific heat of water

  14. Specific Heat • Water 4.184 J/g o • Al: 0.88 J/g o • Cu: 0.38 J/g o • Nitrogen: 1.63 J/g o

  15. Specific Heat of Water • Higher than most other substances • More heat needed to raise its temperature • Heat capacity = specific heat X mass • Specific heat does not change (physical constant) • Heat capacity changes with the amount of water present

  16. Practical Application • Al has lower specific heat than water • Heat an Al pot • Pot gets very hot very fast • Pot transfers heat to water rapidly • Most of the heat used gets into the water.

  17. Consequence • Spain is approximately same northern location as New York City • Spain is generally considered a warm climate • New York is not considered a warm climate • Europe would be much colder • Warmed by ocean water currents

  18. Water as a Solvent • Review Section 7 • Solvent – liquid used to dissolve something • Dissolve – process of material dispersing evenly in a solvent • Solute – material being dissolved • Solvent is present in larger amounts • Solution is a homogeneous mixture

  19. Water as a Solvent • Difficult to contain very pure water • Container dissolves in water • Water is no longer very pure • Small polar molecules dissolve best • Some molecules (non-polar) are insoluble. • Principle: like dissolves like • Amount of solute that dissolves determined by solutes solubility • Maximum amount of solute dissolved – solution is saturated

  20. Solutes • Gases • Carbon dioxide, oxygen, and nitrogen dissolve in water • Solubility isn’t very high • Sufficient for life • Higher solubility observed in cold water • Salts (ionic solutes) • NaCl, baking soda, cream of tartar dissolve in water • Ocean water has NaCl • Blood has NaCl • Salts that dissolve in water are called electrolytes • Conduct electricity • Lime and gypsum are not very soluble (nearly insoluble)

  21. Municipal Water Supplies • Water supplies • Wells, rivers, lakes, ocean • Different treatment problems • Treatment • Destroy pathogenic bacteria • Typhoid and cholera regular epidemics • Killing thousands • 1908 Jersey City, NJ, added chlorine to water • Kills pathogenic bacteria, algae, and viruses

  22. Water Treatment • Potable water is safe for drinking • In US potable water is used • Drinking • Cooking • Flushing toilets • Cleaning • Not true of most of the world

  23. The Process of Making Water Potable • Destroy pathogenic bacteria • Typhoid and cholera regular epidemics • Killing thousands • 1908 Jersey City, NJ, added chlorine to water • Kills pathogenic bacteria, algae, and viruses

  24. Municipal Water Treatment • Chlorine – safety concerns • Ozone • O3 formed from oxygen • Removes objectionable metal ions (Fe, Mn) • Chlorine still used if water is stored • Filtration • Removes solid materials • Sedimentation • Add Aluminum sulfate and calcium hydroxide • Form a gelatinous precipitate that gathers small particulate materials • Entraps microorganisms as well • Distillation and ion exchange are rarely used - expense

  25. Desalinization • Majority of world’s water is in oceans • Brackish groundwater (slightly salty) • Remove salt • Primary source of fresh water in • California, North Africa, Middle East, and Caribbean

  26. Desalinization • Distillation • Vaporizing water then condensing • 60% of desalinized water • Energy intensive process • Reverse Osmosis

  27. Reverse Osmosis • Osmosis – flow of water from region of low salt concentration into region of high salt concentration • Semipermeable membrane is used • Permits small water molecules to pass through

  28. Osmosis

  29. Reverse Osmosis

  30. Water Pollution • Because of the water cycle any pollutant put in water doesn’t simply stay there • Pollution is incorporated in the cycle • Puts pollutants in and out of other cycles • Including living organisms

  31. Not a Recent Problem • 1855 Michael Faraday reported • Thames River was brown in color and smelled very bad. • Largely due to human and horse bodily waste materials • Cholera and typhoid microorganisms were carried in water supplies

  32. What is water pollution? • Clean Water Act (1972) • Pollution is the man-made or man-induced alteration of the chemical, physical, biological, and radiological integrity of water. • Polluted water might be safe for some uses. • Water can be polluted by animal activity.

  33. Sources of Pollution • Point Sources –concentrated at a specific location • Diffuse Sources – comes from more broad region or area • Indirect Pathways – pollution of the soil, ground water, and waterways • Atmospheric Sources – acid rain (next chapter)

  34. Water Pollution

  35. Water Pollution

  36. Water Pollution

  37. Water Pollution

  38. Water Pollution

  39. Water Pollution

  40. Water Pollution?

  41. Water • Water isn’t used just for drinking • Water isn’t used just for cooking • Water is used for waste elimination • Where does the waste go? • Past – into the water cycle • Today – waste water must be treated

  42. Wastewater Treatment • Designed to remove human waste • Three Step Process • Primary • Secondary • Tertiary

  43. Primary Treatment • Removal of floating or suspended solids • Skimmed off surface, then • Passed through fine screens • May add Al ions (flocculent) • May add chlorine to convert • H2S into SO4-2 (odorless) • 30% of pollutants have been removed

  44. Secondary Treatment • Bacteria are added • Metabolize organic materials into CO2 • About 70% of organics are converted • Urea is converted into CO2 + ammonia • Ammonia is converted into nitrate • Sludge settles out • 85 – 95% of pollutants have been removed • Can be reintroduced to environment

  45. Tertiary Treatment • Addition of Ca(OH)2 • Precipitates phosphate ion • Raises pH • Further reduces the amount of ammonia • Sometimes chlorine is added – reduce odor • Water is safe for reentry to environment

  46. Water Treatment • In 2006 there were 1.8 million deaths due waterborne illness because of poor sanitation in developing nations.

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