A few weeks ago, I came across this idea for a low-cost vehicle that also serves as a water filtration apparatus. It's really genius!
The Aquaduct is a pedal-powered concept vehicle that transports,
filters, and stores water for the developing world. The functional model
was designed and constructed over a three-week period for the Innovate
or Die contest hosted by Specialized Bicycles, Google, and Goodby,
Silverstein and Partners.
As the rider pedals, a pump attached to the pedal crank draws water from a large holding tank, through a carbon filter, to a smaller, clean
tank. A clutch engages and disengages the drive belt from the pedal
crank, enabling the rider to filter the water while traveling or while
stationary. The clean tank is removable and closed for
contamination-free home storage and use.
Also, be sure to check out this page: http://www.ideo.com/work/featured/aquaduct
What I love about this idea is that it doesn't try to solve the problem with a band-aid solution. The inventors are not saying "Let's get everyone clean water directly". That would be unsustainable, so instead they recognized that there will always be water that is not fit for consumption (as long as there is water left on the planet...). So they developed a way for people to transform that water for their needs as their need arises.
It's no play pump, and of course if the source of water was closer it would be better. But instead of waiting for all the different elements to align (infrastructure, government backing, technical expertise to drill wells, etc.), they have taken the problem as it is and found an immediate solution for it.