Field Demonstration of a Surfactant-Enhanced Soil Slurry Bioreactor Technology for the Remediation of Explosives-Contaminated Soil

Biological treatment of explosives- contaminated soil is currently of interest to the U.S. Department of Defense. Composting is a fully implemented technology capable of removing explosives from soil cost-effectively. The biological and chemical reactions occurring during composting remove 2,4,6-trinitrotoluene TNT, octahydro- 1 ,3,5,7-tetranitro- 1 ,3,5,7-tetrazocine HMX, and hexahydro- l,3,5-trinitro-l,3,5-triazine RDX, leaving no intermediates. Over the past several years, various groups have examined the use of soil slurry reactors to degrade explosives in soil. Several years of laboratory study have culminated in a pilot demonstration at the Joliet Army Ammunition Plant JAAP, Joliet, Illinois. Laboratory and field studies Manning et al., 1995 have demonstrated that TNT, HMX, and RDX can be biologically degraded with molasses as a cosubstrate. Waterways Experiment Station has conducted experiments examining the impact of surfactants on enhancing the degradation of explosives in a slurry reactor. These studies have been encouraging in batch reactor situations. The laboratory studies examined many different surfactants and determined that polysorbate 80 Tween 80 is the most cost-effective. In addition, Tween 80 can be purchased commercially as a food-grade compound, eliminating regulatory concerns. The laboratory studies also investigated the different concentrations of surfactant in the reactor. The operating conditions were periods of aerobic conditions with measurable dissolved oxygen, followed by periods of anoxic conditions with no measurable dissolved oxygen but significant concentrations of nitrate, nitrite, and sulfate. The laboratory studies led to the development of a pilot-scale system to investigate the performance of soil slurry reactors with surfactant enhancement under field conditions. The pilot study at JAAP ran for almost six months. This was an extension of a previous pilot study conducted at JAAP. For this work,