Yep. You heard me: Nov. 19 is World Toilet Day. Brought to you by the Water Supply and Sanitation Collaborative Council and the World Toilet Toilet Organization (and supported by Domestos, a Unilever cleaning brand), the day reminds those of us with nice warm bathrooms and healthy sanitation that it ain't that way for all of us.

Like, say, the 2.5 billion people who lack a clean toilet. Remember the outhouse scene in "Slumdog Millionaire"? That's all over the world.

It's a staggering number, considering that when in 2007 the British Medical Journal asked its readers to name the most important medical milestone since 1840, they chose modern sanitation -- which defeated things like, say, antibiotics or anesthesia or vaccines. And yet 2.5 billion people still don't have it.

So it's worth reminding ourselves that even an enormous problem like 2.5 billion people who need sanitation does not always require an enormous solution. Small steps help.

As an example (hat tip to the excellent Matt Shipman), consider Tate Rogers, graduate student at N.C. State University, who applied technology no more complex than the Archimedes screw to the age-old problem of what to do once the pit latrine is full.

Tate grew up on a farm and says he spent a couple days thinking before he came up with his idea, which won a $100,000 grant from the Bill and Melinda Gates Foundation before Tate even entered grad school. Tate's invention requires little more than a gasoline engine, some PVC pipe, and an auger. Here's Tate on some of the thing's advantages:

"The prototype has produced flow rates up to 13 gallons per minute. It costs less than $750 to produce and we estimate the cost per pit latrine emptied to be less than $5 compared to $30-$80 for current technologies."

That's not building a $2 trillion sewer system or requiring an entire grid's worth of power supply. That's getting the nasty stuff up and away from the house to where it can be reused or treated. Saving the lives of families.

For five bucks.

Big problems. Small, cheap solutions. Yay engineers. Yay science. Yay Tate Rogers and his ilk for getting to work.

P.S. Fun facts to know and tell: many wastewater treatment plants still use Archimedes screw to move water to the plant headworks, after which the stuff flows downhill. Don't mess with what works.