1SDS 1-9, 18-22

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Evaporation: changing from the liquid state to gaseous state.
Precipitation: moisture falling from the atmosphere as rain, snow, sleet, or hail
Run off: water from the mountains rushing downstream

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

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

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

3. The properties of aluminum hydroxide is related to the process of fluctuation because aluminum hydroxide traps and removes the suspended particles, a process called flocculation.

4. Calcium oxide is sometimes added in the final steps of municipal water treatment to remove suspended particles.

5. As much as 1 ppm of flu ride ion may be added in the fluoridation process because the fluoride ions can reduce tooth decay.

6. The advantages of chlorinated drinking water compared to untreated water is that chlorinated water is much safer because chlorine kills disease-producing microorganisms.

7. The disadvantage of using chlorination in water treatment is that under some conditions, chlorine in water can react with organic compounds produced by decomposing animal and plant matter to form substances that, if in sufficiently high concentrations, 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 contain harmful bacteria and heavy metal ions that could be harmful to drink, so chlorine is needed to kill disease-producing microorganisms.

9. Two alternatives to the use of chlorination in municipal water treatment are: 

    Charcoal filters: activated charcoal can remove most organic compounds from water including THMs.

    Sand filtration: Removes big redundant material from the water.

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