1. Water Purification and Treatment
Unit 1 – Section D
Water Purification and Treatment

2. HW – 1
Read and take notes on Unit 1 sections D.1 & D.2. The section starts on pg 86 D.3 write out and answer questions.

3. D.1 Natural Water Purification (aka Purifying through the hydrological cycle)
Evaporation, followed by condensation removes nearly all dissolved substances
Bacterial actions convert organic contaminants into a few simple compounds
Filtration through sand & gravel remove suspended materials

4. D.1 Natural Water Purification (continued)
Pure rainwater is the best natural supply of clean water

5. D.2 Municipal Water Purification
Screening
Coagulent added (alum)
Flocculation removing suspended particles
Settling
Sand filtration
Chlorination
Optional depending on water quality:
Aeration
pH adjustment
Fluoridation

6. D.3 Water Purification Natural Water Cycle Municipal Treatment
Similarities
Sand filtration
Differences
Bacterial action
Chlorination

7. D.3 Water Purification (continued)
Remember the natural cycle can be overwhelmed by over demand

8. HW - 2
Read and take notes D.4 & D.5

9. D.4 Chlorination of Water
Chlorination greatly helps reduce the risk of many diseases and illnesses.

10. D.4 Chlorination of Water (continued)
How do we chlorinate water?
Cl2 is bubbled through H2O
A water solution of NaOCl - sodium hypochlorite, (household bleach) is added to water
Ca(OCl)2 - Calcium hypochlorite is dissolved in water (commonly used in swimming pools)

11. D.4 Chlorination of Water (continued)
Some chlorine is good, too much presents new chemical risks.
Cl reacts with organics to produce THMc
(trihalomenthanes)
A common THM is  chloroform
CHCl3

12. D.5 Chlorination and THMs
How to deal with THMs? 1) Pass treatment-water plant through charcoal filter. Disadvantages: expensive to install and operate

13. D.5 Chlorination and THMs (continued)
2 ) Eliminate chlorine and use ozone (O3) or ultraviolet light to disinfect. Disadvantages: does not protect water once it leaves treatment plant

14. D.5 Chlorination and THMs (continued)
3 ) Eliminate prechlorination add only once after filtering. Disadvantages: still promotes THMs (lesser extent) and decreased chlorination can allow bacterial growth

15. HW – 3
Pre-read D.6 Bottled Water vs. Tap Water we will be doing this in class.
Working with a partner answer the questions on pg. 92

16. D.6 Bottled Water vs. Tap Water
Bottled water is
Tap water is
•More consistent in taste •More convenient
•stringently regulated •Readily available •costs less

17. In class
Working with a partner answer the questions on pg. 92 17

18. HW – 4
Pre-read and take notes on D.7 AND just like it looks on pg 94, create a data table as shown. This should be done in a word document.

19. D.7 Water Softening
Water hardness is not addressed at municipal treatment plants. Water containing an excess of dissolved calcium (Ca2+), magnesium (Mg2+) or iron (III) (Fe3+) ions is known as hard water.

20. D.7 Water Softening (continued)
River water usually contains low levels of calcium (Ca2+), magnesium (Mg2+) or iron (III) (Fe3+) ions , however as it flows over limestone, chalk and other minerals that contain them it gains higher concentrations.

21. D.7 Water Softening (continued)
One method of water softening is ion exchange , passing the water through tiny insoluble, porous beads capable of attracting and building cations.

22. HW – 5
Read and take notes on D.8 Water & Water Softening

23. D.8 Water & Water Softening
Hard water causes common household problems:
Interferes with actions of soap
Scale may form as a result of heating

24. D.8 Water & Water Softening (continued)
Most cleaning products today contain detergent rather than soap.

25. D.8 Water & Water Softening (continued)
If you live in a hard-water region, your home plumbing may include a water-softener on you home plumbing.
Hardness Magnitude
Grains Per Gallon (GPG)
Soft Water
gpg
Moderately Hard Water
gpg
Hard Water
gpg
Very Hard Water
gpg
Extremely Hard Water
> 10.5 gpg

26. Connecting the Concepts
Due by end of class
Q.s 20, 22 & 23* on pg. 103
* Reference pg. 628 assume adult, age 50-70