Non-profit organization OHorizons recently created an innovative BioSand Filter that can deliver clean water at 1/10th of the cost of traditional methods. The filter hinges upon an open-source Wood Mold that can be easily built by anyone using the construction manual, which is available for free online.
Phi Beta Iota: Marcin Jacubowski has done more than anyone to demonstrate that Open Source Everything Engineering (OSEE) yields solutions at 10% to 25% the cost of industrial era proprietary solutions, with the savings applicable across the lifetime of the solution, not only at purchase point. It merits comment that it is official US Government policy to enable fracking, agriculture, and other industrial practices to poison the groundwater. No amount of filtering can make up for an insanely criminal government policy schema.