Pg 102 #1-9, 18-22
1. Make a diagram of the hydrologic cycle and label all processes.
2. List three major processes that occur in the natural water purification and, for each, identify the contaminants that the process removes.
a. SAND AND GRAVEL FILTRATION: pure rainwater seeps through the ground and encounters bacteria. If it is exposed long enough, all of the organic contaminants and suspended matter would be removed.
b. EVAPORATION: leaves behind minerals and other dissolved substances.
c. BACTERIAL ACTION: converts dissolved organic contaminants into a few simple compounds.
3. How are the properties of aluminum hydroxide related to the process of flocculation?
a. The properties of aluminum hydroxide are related to the process of flocculation because it is a stick, jellylike material that traps and removes the suspended particles, a process called flocculation. Operators then allow the aluminum hydroxide and other solids remaining in the water to settle to the tank bottom. They remove any suspended materials that do not settle out by filtering the water through the sand.
4. Why is calcium oxide (CaO) sometimes added in the final steps of municipal water treatment?
a. Calcium oxide is sometimes added in the final steps of municipal water treatment to neutralize acidic water, thus raising its pH to a proper level.
5. Fluoride, an ingredient in many types of toothpaste, is sometimes added to municipal water supplies in the last stage of water treatment. How much fluoride is added and what is its purpose?
a. 1 ppm of fluoride is added to the water in a process called fluoridation because the fluoride ions can reduce tooth decay.
6. What are the advantages of chlorinated drinking water compared to untreated water?
a. The advantage of chlorinated drinking water compared to untreated water is that chlorinated water is free from disease-producing microorganisms because the chlorine kills the organisms.
7. Is there a disadvantage to using chlorination in water treatment?
a. There is a disadvantage to using chlorination. It is that trihalomethanes (THMs) can develop. A common one is called chloroform, which is a carcinogen, and is known to cause cancer.
8. Water from a clear mountain stream may require chlorination to make it safe for drinking. Explain.
a. The water may require chlorination in order to remove any bacteria or other harmful microorganisms because if not dealt with in the correct way, the bacteria could remain in the water and be very dangerous for humans, no matter how much cleaner the water looks.
9. List two alternatives to the use of chlorination in municipal water treatment.
a. CHARCOAL FILTER: activated charcoal can remove most organic compounds from water, including THMs.
b. OZONE OR ULTRAVIOLET LIGHT: this can completely eliminate chlorine to disinfect the water.
18. Explain what would happen to the Earth’s hydrologic cycle if water evaporation suddenly stopped.
a. If water evaporation suddenly stopped, the hydrologic cycle would be interrupted and water purity would be diminished and more expensive. Within evaporation the water gets purified and falls down as precipitation as pure water. Once the water hits the ground it then becomes impure again, but is easily purified because less bacteria and other microorganisms are within the water.
19. One unique characteristic of water is that it is present in all three physical states (solid, liquid, gas) in the range of temperatures found on Earth. How would the hydrologic cycle be different if this were not true?
a. The hydrologic cycle would be different if this were not true because purification would not be possible through evaporation gas were not available. If liquid water were not available, there would be no human race. If the solid state of gas were not available, the land masses would all be underwater.
20. Why does the EPA limit the concentration of THMs to 80 ppb instead of requiring their total elimination from municipal water supplies?
a. The possible health risks involved.
21. Compare how the various processes used in the foul-water investigation (page 10) are similar to the steps in the natural purification of water.
a. They are similar because sand and gravel filtration helps filter out any solid or suspended materials in the foul water lab, similar to in the natural cycle. Similarly, the charcoal filtration was like having the water purified through rocks that contain dissolved minerals.
22. Some physicians recommend consuming about 2 L of water daily. Municipal supplies may contain up to 1 ppm fluoride. Assume that you drink 2 L of water per day. At 1ppm fluoride, how many grams of fluoride ion would you consume in:
a. One day: 2 ppm fluoride
b. One week: 14 ppm fluoride
c. One year: 730 ppm fluoride
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