Water filtration media called GreensandPlus Water Filtration is used to eliminate hydrogen sulfide, iron, and manganese from water. It is an enhanced form of the conventional greensand, glauconite, a naturally occurring mineral that has long been used to cleanse water. One gas that can give water a rotten egg scent is hydrogen sulfide. Hydrogen sulfide in water can be oxidized and eliminated with the use of Greensand Plus.