Pure water is always a need for everybody!
It´s quite possible to purify water through muscular power and bikes.
The first project is AQuaduct 4
More info here: https://www.ideo.com/work/aquaduct
Another successful project is Cycloclean:
And also a pedal power used on water filtering
More info here: http://www.worldwidewater.biz/pedal-powered-water-bike/