I've considered building one, but i have no funds for personal projects. I'm pretty tired of the expense and wastefulness of water filters.
Fire me it's an energy issue because after the water is filtered, it would need to be turned into steam to remove the heavier materials. The distillation process would probably kill viruses and bacteria, but it could always be followed up with strong UV lighting just in case.
I've wondered if solar panels would produce enough power but i don't know.