Recent detection of perchlorate in several surface waters and ground water wells used to supply drinking water has created an unforeseen water contamination crisis in the many Western states in the United States and problems are likely to emerge at other sites where perchlorate is used. In March of 1997, the California Department of Health Services (CDHS) developed a method that reduced the detection limit of perchlorate from 400 ppb to 4 ppb. Based on EPA work, they established a provisional action level of 18 ppb for drinking water. Perchlorate is a health concern due to its interference with iodine in the production of hormones in the thyroid. Subsequent monitoring of 232 groundwater wells by the CDHS indicated perchlorate was in 69 wells (30%) and at concentrations above the action level in 20 wells (9%) (AWWARF 1997). Perchlorate concentrations in surface and groundwater range from detectable to 0.37%, and endanger the extensive use of Colorado River water in the western states. Samples taken from the Las Vegas Wash, which feeds Lake Mead and then the Colorado River, contained 1,500 to 1,680 ppb (Urbansky 1998). The Los Angeles Metropolitan Water District measured 8 ppb in water at its intake in Lake Mead, and the Southern Nevada Water Authority found 11 ppb in its tap water.

Perchlorate contamination arises from the generation and disposal of ammonium perchlorate (AP), a highly energetic compound produced for use in solid rocket propellant. It is extremely soluble and stable in water, and is not easily removed from water. It was the consensus of a team of experts that met at a special workshop on perchlorate that "at this time there is no proven removal process available at the low concentrations being found in drinking water" (AWWARF, 1997). Typical water treatment technologies such as ion exchange, air stripping, carbon adsorption and advanced oxidation, have so far not been shown to be economical for treating perchlorate, which is extemely stable in water and does not adsorb well to activated carbon. Despite its use in rocket propellant, perchlorate is stable in water even under highly reducing conditions. For example, merely lowering the Eh of the water to the range below -200 mV does not produce abiotic perchlorate reduction (Bliven 1996).