Treatment of groundwater contaminated with low levels of military munitions

The site of interest is a military base that was established in the late 1800s. In its early history this facility was used as a powder depot to fill projectiles with miximite (a propellant). Since World War I, this facility was used to produce artillery ammunition, bombs, high explosives, pyrotechnics and other ordinances. Weapons production at this facility has ceased, but as a result of the past activities at this facility, contaminants are migrating into the groundwater. One source of drinking water for this installation is a screened well in a stratified-drift aquifer system at a depth of 75-85 feet below land surface. In the 1980s sampling of this well revealed low level contamination of trichloroethylene (TCE), RDX and HMX. TCE levels exceeded drinking water standards and an air stripping column was installed to remove the TCE. RDX and HMX, concentrations were below drinking water standards. Health Advisory (HA) levels for RDX and HMX were published by the U.S. Environmental Protection Agency (USEPA) in November 1988. The lifetime HA levels are 2 ppb and 400 ppb for RDX and HMX, respectively (McLellan et al. 1988a, and McLellan et al. 1988b). It is expected that continuous withdrawals from this well will increase RDX and HMX concentrations. In addition, it is believed that future USEPA regulations will adapt the HA as a drinking water standard. This study was initiated in an effort to have an appropriate cost effective technology ready to meet any such standard. RDX and HMX RDX and HMX are military explosives. RDX (Hexahydro-l,3,5-trinitro-l,3,5-triazine) is a code name for Research Department Explosive. This explosive is described as a white crystalline solid with about 1.3 times the explosive power of trinitrotoluene (TNT). RDX is classified as a EPA Group C compound: Possible Human Carcinogen (McLellan et. al. 1988a). HMX (Octahydro-1, 3, 5, 7- tetranitro-l, 3, 5, 7-tetrazocine) is a code name for High Melting Explosive. This explosive is described as a colorless crystalline solid with about 1.3 times the explosive power of TNT. HMX is classified as a EPA Group D compound: Not Classified as to Human Carcinogenicity (McLellan et. al. 1988b). Objective of Investigation The objective of this investigation was to determine the feasibility of using granular activated carbon (GAC) and UV/Oxidation (UV/OX) to remove low levels of RDX from a drinking water source. The target treatment level in this investigation was to reduce RDX to less than 1 ppb in the treated water. Historical Treatment of HMX and RDX Until recently, the main concern for the treatment of HMX and RDX was associated with solid waste or wastewater from processing and manufacturing facilities. GAC is the primary treatment used for these wastes and has been known to be effective in removing HMX and RDX to limits which permit discharge. One recently conducted isotherm study by Hinshaw (Hinshaw et. al. 1987), investigated the treatment of synthetic and actual ''pink water'' (wastewater containing explosive) at HMX and RDX concentration levels around 5 ppm and 20 ppm, respectively