HW #11

ISDS #1-9

1.

2.   1) Evaporation, followed by condensation, which removes almost all dissolved substances including heavy metals. 2) Bacterial action converts dissolved organic contaminants into a few simple compounds.  3) Filtration through sand and gravel in the ground that removes almost all suspended material.

3. Flocculation is the process in which an insoluble material is suspended in or precipitated from a solution. It is used in water purification.

4. Calcium Oxideis a basic substance, so it may be added to neutralize acidic water. 

5. About 1 ppm of fluoride is added to water in order to reduce tooth decay. 

6. Chlorinated drinking water is tremendous. Adding chlorine to water has helped save many lives by killing bacteria and controlling water borne diseases. It also kills disease-producing microorganisms in water. Untreated water is more likely to give off water borne disease due to its presence of certain bacteria.

7. Yes because sometimes the chlorine in water can react with organic compounds to form substances that, if in sufficiently high concentrations, can be harmful to human health.

8. This is required to make it safe for drinking because the stream might have bacteria or different substances that are not safe. 

9. Using an activated charcoal filter or using ozone or ultraviolet light to disinfect the water. 

18. If evaporation stopped there would be no condensation and precipitation. This would cause the recycling of water to end, therefore depriving living creatures of clean water and starving plants of water due to the absence of rain. 

19. If this were not true the hydrologic cycle would not include steps like evaporation, which consists of water in the gaseous state or precipitation which takes place when water is in the liquid form. The cycle would not exist without these three water states.

20. The EPA only limits the concentration of THMs because of the alternatives, which can eliminate THM health risks. 

21. The natural purification of water is similar to distillation. When water passes gravel, sand, and rock, suspended mater are filtered out which is similar what we did in the foul water lab.

22.  a) 1 ppm fluoride     b) 7 ppm fluoride     c) 365 ppm fluoride