Blog Homework 11

ISDS #1-9, 18-22

1. Hydrologic cycle - 

2. Natural water purification

1. Evaporation, followed by condensation: removes nearly all dissolved substances

2. Bacterial action: converts dissolved organic contaminants into a few simple compounds

3. Filtration through sand and gravel: removes nearly all suspended matter

3. The properties of aluminum hydroxide are related to the process of flocculation. Flocculation traps the suspended particles and moves them to the bottom.

4. Calcium oxide can be added in the final steps of municipal water treatment in order to neutralize such acidic water; raising the pH to a proper level.

5. Fluoride is an ingredient in toothpaste that can be added to municipal water supplies in the last stage of water treatment in a process called fluoridation, reducing tooth decay. About 1 ppm of fluoride ion is added.

6. An advantage of consuming chlorinated drinking water compared to untreated water is that chlorine is able to kill disease-producing microorganisms.

7. A disadvantage to using chlorination in water treatment is that chlorine in water reacts with organic compounds produced by decomposing animal and plant matter to form substances that can be harmful to human health.

8. Water from a clear mountain stream may require chlorination to make it safe for drinking because the water could possibly contain harmful bacteria and heavy metal ions which are very unsafe to drink.

9. Two alternatives to the use of chlorination in municipal water treatment are charcoal filtration and the use of ozone.

18. If water evaporation suddenly stopped, the Earth's hydrologic cycle would not be able to happen because there would be no substance to condense, and nothing to precipitate or end up back as cleaner water.

19. The hydrologic cycle would not be able to occur either if water could not be represented as a solid, liquid, and a gas. 

20. The EPA limits the concentration of THMs to 80 ppb instead of requiring their total elimination from municipal water supplies because THM is chloroform, a substance known to cause cancer.

21. The steps in the foul water lab are similar to the natural purification of water because they both transform water into a purer state using techniques including charcoal adsorption, sand filtration, and distillation.

22. If you drink 2 L of water per day, at 1 ppm fluoride, you would contain how many grams of fluoride in:

a. One day: 1 ppm

b. One week: 7 ppm

c. One year: 365 ppm