MICROBIAL-MEDIATED REDUCTION OF PERCHLORATE IN GROUNDWATER

Perchlorate has been widely used as a propellant in solid rocket fuel, and has recently been identified as a contaminant in both groundwater and surface waters, Perchlorate is recognized by the U.S. Environment al Protection Agency (USEPA) as a potential health risk, and the State of California has set a drinking water action level of 18 mu g L-1. I ncidents of groundwater contamination have been associated with indust rial sites in California and Nevada that have been involved in the man ufacturing or testing of solid rocket propellants, Microorganisms have been shown to be capable of reducing perchlorate (Cl O-4(-)) chloride (Cl-) and oxy-gen, thus transforming perchlorate into innocuous end-p roducts. Bioreactor processes for the remediation of perchlorate conta minated wastewater have previously been established. However, these sy stems were optimized for perchlorate concentrations in the grams per l iter range, while groundwater contamination can be a million-fold lowe r but still exceed the water quality action level. This literature rev iew will focus on microbial-mediated perchlorate reduction, and discus s issues of importance to the remediation of perchlorate-contaminated groundwater.