Homework #2 week three

1. On paper
2. Three major processes that occur in natural water purification:
1. Evaporation- evaporation is due to the heat from the sun’s rays that hit bodies of water. Evaporation acts like distillation because after the water evaporates the heavy metals and other the water leaves behind undesirable particles; the particles have higher evaporation points than water does.
2. Bacterial action- bacterial action converts dissolved organic contaminants into a few simple compounds that are not harmful.
3. Filtration- filtration through sand and gravel filters most suspended particles as well as the bacteria that clean the water.
3. Aluminum hydroxide is related to the process of flocculation because the sticky property of the substance adsorbs unwanted particles and sinks to the bottom of the water tanks as sludge, which then allows the top layer of cleaner water to be taken and filtered again through sand.
4. Calcium oxide is sometimes added in the final step of municipal water treatment because it needs to neutralize the pH of water that may have turned to acidic. Acidic water deteriorates the pipes, which then allows Copper and Cadmium into the water making it unsafe to drink.
5. Fluoride is added to some water in the final stage of the purification process in order to reduce tooth decay; however, only 1ppm of fluoride maybe be present in water (F^-).
6. Some benefits of chlorinated drinking water:
1. Chlorinated drinking water is protected from bacterial infestations even after it leaves the plant.
2. Chlorinated drinking water helps prevent many illnesses that could be extremely harmful to humans and other organisms.
7. A disadvantage to using chlorination in water treatement is that sometimes Cl in water reacts with natural organisms that are produced by decomposing mammal or plant matter to produce trihalomethanes (THMs); one well-known THM is called chloroform and it is a carcinogenic to humans.
8. Water from a clear mountain stream still needs to be processed because either it may contain small particles of human waste or it may contain substances in water that may have been added as the slightly acidic water ran through water with soluble substances like magnesium.
9. Two alternitaves of water chlorination are using ozone or UV light.
10. If Earth’s hydrologic cycle would not exist if water evaporation suddenly stopped because there would be no way for clouds to accumulate and without cloud formation there would be no rain; therefore, without evaporation the world would not have a replenishing source of fresh water.
11. If water could not be present in all three stages (gas, liquid, and solid) with normal Earth temperatures the hydrologic cycle would not be even relatively similar to the cycle Earth now possesses; without evaporation of water molecules the hydrologic cycle would not be able to perform its function.
12. The EPA limits the concentration of THMs to 80ppb instead of requiring their total elimination because there is no way to acquire their total elimination from the water without discontinuing the use of chlorine; therefore, until we find alternate ways of purifying water THMs will always be present.
13. Some steps from the water purification lab that are similar to steps in the natural purification include:
1. Sand filtration- sand filtration, though used for the foul-water lab, is also a natural way to filter big particles out of water.
2. Distillation- The distillation apperatice evaporates water in order to separate out the unwanted particles that were too small to filter out. Natural evaporation does the same thing and then condenses the water into clouds.
14.  Assume that you drink 2 L of water per day. At 1 ppm fluoride, how many grams of fluoride ion would you consume in
1. One day- 1gF/1,000,000,000 x 2L/1 day x 1,000mg/1g x 1 day = 2mg F
2. One week- 14 milligrams of fluoride per week
3. One year- 730 milligrams of fluoride per week