b'Potable Water SystemFIGURE 2. Typical potable water system using groundwater and surface waterSurface water sources, such as lakes, rivers, andwaste from animal feedlots, and nitrogen-based streams, often require more treatment (as describedfertilizers. High levels of nitrate in drinking water are above) than groundwater because they containassociated with adverse health eects in humans more sediment and pollutants. Groundwater isand livestock; nitrates also adversely aect sh and typically a cleaner water source because the soil actssurface waters. Uranium is a radioactive element as a natural lter that removes bacteria, viruses, and(radionuclide) that occurs naturally in rock, soil, chemicals from the water as it percolates downward,and water, often in low concentrations. Long-term though groundwater is by no means immuneexposure to elevated levels of uranium in drinking from contamination. Naturally occurring and man- water can result in kidney damage. Arsenic is a made contaminants are requiring many suppliersnaturally occurring element found in the earths to install additional treatment methods to meetcrust, rocks, soil, water, air, plants, and animals; it is federal and state requirements. Basic treatment ofalso used industrially as a wood preservative and in groundwater typically consists of adding chlorine forthe manufacture of pesticideds, paints, dyes, drugs, disinfection and polyphosphates to sequester iron andmetals, soaps, and semiconductors. Health eects manganese. Additional, advanced treatments may alsoof arsenic vary depending on the person, level of include aeration, lime softening, ion exchange (IX),exposure, and the amount of time exposed, though electrodialysis reversal (EDR) or reverse osmosis (RO).5 drinking water with high levels of arsenic over a long period may cause lung, bladder, skin, or liver cancer, In Idaho, the three most common groundwaterin addition to other non-cancer health eects. These contaminates include nitrate, arsenic, and uranium.contaminants are typically treated with reverse Nitrate is a nitrogen-containing compound that canosmosis, distillation, ion exchange systems, and enter the water supply from septic sewer systems,carbon block lters.6Water 131'