Unit 5- Water for Life
Question 1
How can you purify your water when you are hiking? Name two or three possibilities. Compare these methods in terms of cost and effectiveness. Are any of these methods similar to those used to purify municipal water supplies? Explain.
Boiling water before drinking is one of the most reliable ways to purify drinking water. The basic rule is to make sure you bring the water to a rolling boil for 1 minute at lower altitudes and 3 minutes at altitudes above 2000 meters. Boiling will eliminate bacteria, protozoa, and even viruses. The downside is you’ll use up your cooking fuel and will need to wait for the water to cool down.
Chemical purification methods weigh almost nothing and are small enough to keep in your first-aid kit so you always have a way to purify water on the trail. Traditionally hikers used iodine tablets, but iodine wasn’t able to eliminate Cryptosporidium and also left the water yellow and tasting weird. Today hikers prefer Chlorine Dioxide Tablets, which purify water with a highly active form of oxygen as they dissolve. The downside is needing to wait 30 minutes for the tablets to effectively neutralize Giardia and up to 4 hours when Cryptosporidium is a concern.
Ultraviolet purifiers neutralize bacteria, protozoa, and viruses with UV rays. Fill a 32 ounce Nalgene water bottle and stir with the ultraviolet purifier for 90 seconds to have purified water. A prefilter is used for murky water and extra batteries should be carried.
Boiling is said to be the convenient and effective method while ultraviolet purifiers is the most costly method.
Chemical purification would be similar to how we purify our water in Singapore, using disinfectants like the chlorine tablets such as using ozone or chlorine to get rid of bacteria and viruses.
Source: https://www.outsideonline.com/2011516/top-5-water-filtration-systems-market
Question 2
Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.
The two most common desalination techniques are distillation and reverse osmosis. Both of these require energy to remove salts from seawater or brackish water, and thus inherently are expensive. If a less expensive option is available (such as hauling fresh water from a distance), then the less expensive option is used.
Furthermore, it contributes to greenhouse gases as the process of removing salt from water is consequential to the environment and results in air pollution.
Question 3
Water quality in a chemical engineering building on campus was continuously monitored because testing indicated water from drinking fountains in the building had dissolved lead levels above those established by NEA.
a. What is the likely major source of the lead in the drinking water?
The likely source of lead is from solder in the pipe joints or from lead pipes themselves.
b. Do the research activities carried out in this chemistry building account for the elevated lead levels found in the drinking water? Explain.
Research activities should not contribute to lead in the drinking water, assuming that any lead compounds are disposed of using prescribed methods. Although many undergraduate chemistry experiments used to use lead, most now have been redesigned to avoid it and other toxic metal ions completely.
Question 4
Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar compounds? Explain.
Only water-soluble vitamins are polar compounds, while fat-soluble vitamins are mostly non-polar compounds. Fat-soluble vitamins are mostly non-polar due to the fatty acid chains and they only have a small polar region. Polar water-soluble vitamins form hydrogen bonds with water molecules and thus can dissolve in water, while fat soluble vitamins do not.
