So, part of living in Italy involves many purchases of
bottled water, specifically the kinds that are purified and chilled water.
Nothing is better in this ridiculous heat than the ability to drink nice, cold
water (even at 500 mL).
So, the actual inspiration for this blog was that while I
was riding the train from Pisa and while I was waiting for my laundry at the Laundromat,
I was also reading “The Hunger Games”. Now, while reading this book, I was
definitely expecting the main character, Katniss, to try to find water after
being dropped into a wilderness environment and forced to fend for herself. But
there is one thing I forgot (or maybe took for granted?) and that is that the
water needs to be purified. She uses iodine, a simple way to destroy any
offensive bacterial agents, as her weapon of choice against any water
contaminants. Thinking about this, I looked at the water bottle I was drinking,
and thought back to the fridge water I so take for granted when I am at home.
Then, I realized that I actually had a pretty great inspiration for a blog
post. How is water filtered?
Having family in India, I have visited the subcontinent
several times. One rule is universal: don’t drink the tap water. It is not a
good idea. It will give you diarrhea and a host of other bad things can erupt.
This is simply because of all the microorganisms that undoubtedly exist in the
water. When we visit my grandmother in India, the only water we are allowed to
drink is bottled water or water that has been boiled to the point that all
contaminants have been killed. Makes sense.
However, this raises an interesting question for me. How
does the bottled water I buy in Italy retain its fresh taste by being filtered?
How does the water I drink in the fridge at home? These questions linger, and I
plan on studying the chemistry of filtering potable water.
Studying about it, apparently the main thing of water
filters involves pores. Basically, there are pores (roughly a micron, or 1/1000
of a millimeter, big) and most things such as bacteria, protozoa, and the like
are caught by the pores, while water is allowed to freely flow through. This is
why sometimes water filters can be very slow moving, while other times they can
be very fast.
However, there is some very cool chemistry that can be used
to filter water for human consumption. Look at a water bottle in America and
most all of them have been filtered through a process known as reverse osmosis.
This basically means that, using a semipermeable membrane and some simple
equilibrium chemistry (including Le Chatelier’s principle), the osmotic
pressure on both sides of a membrane is equalized. Using pressure, reverse
osmosis can occur, instead of equilibrating the pressure of both sides, the
added pressure essentially forces clean water to the other side of a
semi-permeable membrane. Adding a stress to the system causes a change in
concentration. Not a perfect example of equilibrium rules, but the basic
underlying principle holds true.
However, if you are hiking in the woods, chemistry can also
be your friend. Take, for instance, the iodine example I gave above. Assuming
you don’t have a thyroid problem or an iodine allergy, that would be totally acceptable,
and Katniss was smart to do so (even though I didn’t even think of purifying
the water). In a pinch, chlorine will do, even though that’s more for pools and
drinking chlorinated water regularly is definitely not good for you. Treat the
water for 30 minutes or so, strain it if need be, make sure the water is warm
as possible (cold water is harder to treat, and should be allowed to sit for
longer), and do something about the taste of iodine or, worse, chlorine. These
are both elements that will kill the pathogens in the water and allow us to use
chemistry for our biological functionality. (There’s a reason Italians drink
wine, it’s tradition: back in the day, they didn’t have this fancy chemistry.
What they did have: ethanol. Alcohol kills bacteria. Simple.)
Hopefully, if you are in the Hunger Games, just need some
clean water, or are just curious about the water that you drink and how it is
filtered, you have learned something from this blog post. Water is a
universally important biological necessity, and having clean water is
important. This is why so many filtration methods exist. Taste is also
important, which is why we have things to add to water, and why Italians seem
to prefer bottled water from the less-pleasant-tasting tap water. Something we
take for granted every day is something we can now understand much better:
having potable, clean water. And isn’t that just a little bit cool?
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