In the same vein of the compost bin, perhaps a device that can either filter the water using perhaps charcoal and sand, or sweetening the water using honey and wine? perhaps a formula of original water quality x3, + quality of built device, + quality of charcoal + quality of sand / 6, and again along the lines of the compost bin, would take time to produce the finished product,. The formula above would not create outrageously high quality, but would give a moderate boost.
critques?