A reverse osmosis system removes dissolved solids like arsenic and flouride throught the RO membrane. An RO system also includes sediment and carbon filtration for a broad spectrum of reduction. The carbon filters in an RO system remove chlorine and bad taste and odors, and the sediment filter removes dirt and debris. An RO system also removes salt, VOC's, herbicides and pesticides, and many other contaminants.
A reverse osmosis system is one of the most extensive methods of filtration. It removes 98% of dissolved solids, whick makes it healthier to drink. A water distiller is the only other drinking water system that also reduces TDS, but it's less efficient than an RO system.