This winner of the Innovate or Die competition filters water through pedal power:

A peristaltic pump attached to the pedal crank draws water from a large tank, through a carbon filter, to a smaller clean tank. The clean tank is removable and closed for contamination-free home storage and use. A clutch engages and disengages the drive belt from the pedal crank, enabling the rider to filter the water while traveling or while stationary.

Aquaduct pedal-powered water transport and filtration – [via] Link.