So in an albeit minor effort to improve upon our collective communication with non-scientists, I decided to start a new recurring column on this blog entitled “Family Ties.” Maybe named after the American 1980’s sitcom of the same name, I’m giving various members of my family a chance to ask any sort of environmental/energy/nature type question they want, and I’ll do my best to answer it as clearly as possible.

First up, of course, is my mom. Here’s her question:

“Why can’t we drink sea water without desaltification/purification?”

Dear Mom,
The short answer is: Because you’ll get dehydrated!

But it’s a great question. It’s easy to see that water is an increasingly valuable resource even if we aren’t regularly reminded of it in our daily lives and/or water bills. With 6 billion people on the planet, and roughly double that expected within the century, we’re going to need a lot of water for all those people and all the crops/animals they’ll eat. As it is, roughly 1 out of every 6 people (i.e. 1 billion people) lack access to clean water. It’s almost certainly going to get worse.

Unfortunately, there’s not an easy fix. Less that 1% of all water on Earth is found in places that we can extract it for drinking/food use i.e. in groundwater and lakes/rivers. As you might imagine, the overwhelming majority of Earth’s water is in the oceans. If we could drink ocean water, we’d have a virtually limitless supply of water—certainly enough to sustain as many people that can fit on Earth, right? Well, that’s much easier said than done.

If you were to take several big swigs of ocean water, your body wouldn’t like it at all. Although we do need some salt to survive, too much of it actually dehydrates us. I am fairly certain this dehydration occurs because blood cells release water in an attempt to dilute high concentrations of salt. Beyond that, I’m not exactly sure what else is going on, but I’d bet it has something to do with your kidneys’ ability to function properly when there’s that much salt.

There are efforts, however, to make it so we can drink seawater. Distillation is a very old method for driving off the salt from water (also known as desalination), but reverse osmosis is more efficient and can generate much more freshwater. Reverse osmosis essentially uses high pressure to push water through membranes that filter out the salt. Unfortunately, it’s still a very expensive and energy-intensive process. There are also a lot of environmental concerns with already existing desalination plants. However, there is a lot of research nowadays directed towards improving reverse osmosis, but it’s still not a viable means for meeting the global water demand, now or in the future… and those people in the photo above really don’t like it.

Anyway, thanks Mom for thinking of a good question, and start thinking Dad, because you’re next on my list!

Other resources on the web:
Here’s a great website from the National Academy of Sciences that highlights some of the global concerns about drinking water:
http://www.drinking-water.org