Bio-sand filter: Slow sand filtration with a living biological layer at the surface; effective and needs no electricity, but requires a maturation period and careful maintenance
Ceramic candle filter (silver-impregnated): Silver-impregnated ceramic candle or pot filter (e.g. the Filtron design developed with Potters for Peace) removing particulates and the large majority of bacte
Reverse osmosis (RO) filtration: Semi-permeable membrane forces water through under pressure, rejecting dissolved solids, salts, and contaminants (PFAS, nitrates, heavy metals) that filtration