Water Purification and Treatment

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Water Purification and Treatment
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Introduction

• 1. Where did we used to get our water from
  before the last part of the 1800s?
• Local ponds, wells and rainwater holding tanks
• 2. How was wastewater and human waste disposed
  of?
• Dry wells, pits lined with broken stone, or just
  dumped on the ground
• Human waste would be thrown into holes or
  receptacles lined with brick or stone

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Introduction

• 3. What subsequently resulted from this method?
• Waterborne diseases increased
• 4. What happened to solve this?
• Filtration and chlorination of municipal water
  supplies soon began

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Introduction

• 5. What problem still was not solved until
  midway through this century?
• How to clean the municipal sewage of a community

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Natural Water Purification

• 6. Describe how water purifies itself?
• Water cycle Evaporation, Condensation,
  Precipitation
• 7. What used to be the purest form of water on
  earth? Why is the word used an important verb
  in our world today?
• Raindrops and snowflakes, Nature and humans
  release harmful gases into the air. Making it
  less pure than it was in earlier times

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Natural Water Purification

• 8. Describe what happens when the water or
  snowflake strikes the earth
• Organic substances deposited by living things
  becomes dissolved in water

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Natural Water Purification

• 9. Summarize natural purification in three
  points
• 1. Evaporation followed by condensation, nearly
  removes all dissolved substances
• 2. Bacteria converts dissolved organic
  contaminants to a few simple compounds
• 3. Filtration through sand and gravel removes
  almost all the suspended matter

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Natural Water Purification

• 10. What is wrong with allowing nature to purify
  our water?
• If water is acidic, it could add substances to
  the water as it flows through gravel instead of
  taking it away
• 11. What is hard water?
• Water with excess Ca, Mg, and Fe(III) ions, it
  does not lather well

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Municipal Water Purification

• 11. How often is our water cleaned? Why?
• Twice, once before we use it and once after we
  use it
• 12. What is the pre-cleaning called and where
  does it take place?
• Water treatment-Municipal Filtration and
  Treatment Plant

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Municipal Water Purification

• 13. Sketch Fig 1.31. List and describe the
  different steps to water treatment?

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1. Screening-metal screen prevents fish, sticks,
   soda cans, and other large objects from entering
   the plant
2. Pre-chlorination-chlorine is added to kill
   disease causing bacteria
3. Flocculation Alum(Aluminum sulfate) and
   lime(Calcium hydroxide) are added to remove
   clays. This clears up the water
4. Settling the alum/clay and lime/clay and other
   solids settle out to the bottom

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• Sand filtration any suspended solid that did
  not settle out is removed here
• Post Chlorination amount is adjusted so that
  there is just enough to keep it germ free
• Optional Further Treatment
• Aeration-sprayed into air to remove odor and
  improve taste
• pH Adjustment CaO is added to make water less
  acidic
• Fluoridation 1ppm of Fluoride ion may be added
  to reduce tooth decay , osteoporosis, and
  hardening of the arteries

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Chlorine in our water

• 14. What is the most common additive used and for
  what reason?
• chlorine
• 15. Where else is chlorination used?
• Laundry Bleach, and as Calcium hypochlorite
  pellets for you pool-Shock it

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Chlorine in our Water

• 16. What are the three possible methods of
  chlorinating our water?
• omit
• 17. What form does chlorine take in water?
• HOCl

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Chlorine in our Water

• 18. Read ChemQuandary, Answer questions 1 and 2
• 19. Read Chemistry at work on page 82.
• a. What are aquifers?
• b. How is aquifer water purified in Sanibel
  Island?
• c. Why does Sanibel Island contain so much fresh
  water in storage?

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Natural Water Purification

• 20. What is hard water?
• Water that contains Fe3, Ca2, and Mg2 ions
• 21. What does it mean when we try to soften
  water?
• Process of removing the Hard water ions

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Hard Water and Water Softening

• 22. What is the difference between the mineral
  content of surface water and ground water?
• Ground water has higher concentrations of
  Fe(III), Ca, and Mg than surface water

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23. What is Tennessee like when it comes to
water hardness?
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Hard Water and Water Softening

• 23. What household problem are caused by hard
  water?
• Interferes with the cleaning action of soaps
• Hard water ions combines with soap to form a
  sticky scum
• 24. How can you get rid of hydrogen carbonate
  ions in water?
• Boiling the water-Ca ions combine with hydrogen
  carbonate

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Soap Scum
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Hard Water and Water Softening

• 25. Name some problems associated with this
  boiling to get rid of the ions?
• Forms a scale in tea kettles and household hot
  water heaters
• Same stuff found in marbles and limestone and it
  acts like a thermal insulator
• Partially blocks the heat flow and makes it hard
  for the water to be heated
• Stops up water pipes

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• 26. What is another way to soften water?
• Adding washing soda or sodium bicarbonate to the
  water
• Other common softeners are borax, trisodium
  phosphate, and Calgon

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Hard Water and Water Softening

• 27. What are the problems with the detergents
  made today?
• Some cannot be broken down by bacteria and formed
  foamy suds in our streams
• Some also had a lot of phosphate which caused
  bacteria to grow quickly and choke out many of
  our waterways
• 28. What can you do if you live in a hard water
  area?
• Attach a water softener to your home plumbing

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Hard Water and Water Softening

• 29. How does a water softener work?
• Water flows through a large tank containing an
  ion exchange resin
• This resin is made up of tiny little beads that
  attract positive ions. They are initially filled
  with sodium ions
• The Ca and Mg ions replaces the Na in the resin
• Na ion goes into the water, it is safe

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Hard Water and Water Softening

• 30. Eventually, what happens to water softener?
  What can you do to fix it?
• Fills with hard water ions and must be
  regenerated
• Allows concentrated salt water, the Na ions
  replace the hard water ions again

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Hard Water and Water Softening

• 31. If you do not live in an area that uses
  water softeners in their homes, how does your
  water become softened?
• At the treatment plant

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Municipal Water Purification

• 32. Where does post-use cleaning take place?
• Sewage Treatment Plant

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Municipal Water Purification

• 33. What is the major goal of wastewater
  treatment?
• Prevent bacteria and viruses which are found in
  human waste from infecting the public
• 34. What other undesirable materials does this
  water contain?
• Garbage disposal scraps, organic solvents, waste
  from homes, businesses, and industry

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Lab 4 Water Softening

• You are going to explore several ways of
  softening water
• 1. What three ways of softening water are we
  going to use?
• A. Sand filtration
• B. Treatment with Calgon
• C. Treatment with an ion exchange resin

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• 2. What is Calgon?
• Sodium hexametaphosphate(Na6P6O18)
• 3. How does it work?
• Sticks to hard water ions and makes them become
  large anions that can be washed away with water

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• 4. What does Calgon also contain?
• Sodium carbonate
• 5. What is another name for sodium carbonate?
• Washing soda
• 6. How does it work?
• The carbonate part of it reacts with Ca2 ions
  and precipitates them out

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• 7. What equation can be used to describe the way
  that washing soda softens water?
• Ca2(aq) CO3-2(aq) --gt CaCO3(s)
• 8. What is ion exchange resin?
• Tiny little spheres that have cracks in it which
  attract hard water ions, when the hard water ions
  get in they cannot get out, they are like tiny
  little hard ion mousetraps

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• 9. What are the two tests that we are going to
  perform in this lab?
• We are going to take hard water and filter it,
  filter it with sand, filter it with Calgon, and
  filter it with an ion exchange
• We are then going to test the result with
• 1. Sodium carbonate
• 2. Soap

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The Four Water softening methods
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• Something in the water obviously killed the fish
  in the Snake River and yet none of the most
  common causes of water contamination has been the
  culprit
• Tests have verified that the water is perfectly
  safe for human and animal use and contains enough
  O2 to support water life
• What is the answer? Tomorrow you will find out!