Fluidized bed bioreactor treatment of perchlorate-laden groundwater to potable standards

erchlorate is a highly soluble salt anion that can negatively affect the ability of the human thyroid to adequately uptake iodide (Greer et al, 2002; Wolf, 1998). Since early 1997, perchlorate analytical techniques have significantly improved. As a result, drinking water testing performed throughout the United States has uncovered perchlorate contamination in several regions of the country at levels at or below 1 μg/L (USEPA, 2004). The majority of the perchlorate contamination in groundwater aquifers is believed to be attributable to historical disposal practices by the aerospace and ordinance industries, the military, and chemical manufacturers. Perchlorate salts have been used in the US defense and space programs for several decades as primary oxidants in the solid propellants that power rocket motors, rocket boosters, and missiles. In past disposal practices, solid perchlorate-containing fuels were often burned in opendetonation areas, and aqueous processing waters or wastewaters were released to surface soils or discharged into evaporation ponds. Given past disposal practices and the mobility of the anion, numerous drinking water aquifers throughout the United States have been contaminated with perchlorate (USEPA, 2004). No federal drinking water maximum contaminant level (MCL) has been established for perchlorate. However, several states have set their own advisory levels, e.g., 1 μg/L in Maryland and New Mexico, 5 μg/L in New York, 14 μg/L in Arizona, and 18 μg/L in Nevada (Hatzinger, 2005). In July 2006, Massachusetts became the first state to set an MCL of 2 μg/L (MDEP, 2006). California followed in 2007 with the establishment of an MCL of 6 μg/L (CDPH, 2007). In the absence of federal regulation, these states chose to take a proactive approach to remove from service any drinking water well in which these advisory levels or MCLs are exceeded. In many cases, this water must be replaced with other outside sources (i.e., bottled water, imported surface water) at substantially higher costs to the residents in the area. Alternative cost-effective perchlorate remediation technologies are needed to help put these wells back in service. BY TODD S. WEBSTER,