Application Exercise 5: Water for life

  1. How can you purify your water when you are hiking? Name two or three possibilities. What are the relative costs and effectiveness of these alternatives? Are any of the methods similar to those used to purify municipal water supplies? Explain.

    Several options exist for purifying water while hiking. The traditional method is to boil it. Boiling kills many microorganisms that may make you sick, but requires time and will not remove chemical contamination. Boiling also requires time, fuel, and may release soot and CO to the environment.

    Another method of water purification is with iodine. It is easy and effective in twenty minutes, but iodine should not be used long-term., In addition, pregnant women and people with thyroid conditions should avoid purification with iodine. While iodine renders water bacteriologically safe, it doesn’t remove chemical contaminants. Many people dislike the taste of iodine-treated water.

    ktc39-twp-114

    Lastly, filtering cleans water mechanically. Travel water filters are good microfiltration unit that can remove: “harmful cocci, bacteria, protozoa, fungi, cysts, and parasites are totally removed, including the chemically resistant infectious agents of Giardia, the amoebic and shigella dysenteries, and those causing typhoid, cholera bilharzia and a long list of other dangerous diseases.” Filtration has the advantage over other methods mentioned above as it does not require chemicals. However, filters are the most expensive option out of the rest but a good filter pumps out good water in a few minutes and is reusable.

    2. Explain why desalination techniques, despite proven technological effectiveness, are not used more widely to produce potable drinking water.

    desalination

    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.

    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. Does the chemical research carried out in this chemistry building account for the elevated lead levels found in the drinking water? Why or why not?
    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.

    4. Some vitamins are water-soluble, whereas others are fat-soluble. Would you expect either or both to be polar molecules? Explain.

    Only water-soluble vitamins would be expected to be polar molecules. Though a fat-soluble vitamin will often have individual polar bonds or small regions of the molecule, overall this is out-weighed by non-polar sections. Polar covalent bonds attract to water through hydrogen bonding and may allow the molecules to dissolve in water, while non-polar covalent bonds favour interactions with the non-polar chains in lipids.