Many substances are found in groundwater, mostly in very low concentrations. The goal is to remove them to very low residual concentrations. This is often a home game for ion exchangers! The only prerequisite is that a good selective solution is feasible, as complete desalination to remove a few toxic substances is not economical. It is precisely in such selectively demanding processes that ion exchangers often come out on top. It is amazing for which contaminants ion exchangers perform well.