Field demonstration of in-situ bioremediation of RDX and HMX using molasses

Abstract

A nine-month, in-situ bioremediation study was conducted at Mākua Military Reservation on O'ahu, Hawaiʻi (USA) to evaluate the potential of molasses to enhance biodegradation of explosives (RDX and HMX) contaminated soil below the root zone. Molasses/water mixture (1:40 dilution) and clean water was applied to treatment plot and control plot, respectively in seven successive flood irrigation events. The change in concentration of explosives over time in lysimeter collected pore water samples was measured to determine treatment effectiveness. The mean concentrations of RDX from the two test plots differed very highly significant (p < 0.001) and degradation was most prevalent at depths from 5 to 13.5 ft. HMX was also degraded but only at a depth of 5 ft. The molasses/water mixture had a similar infiltration rate to that of water and was able to reach the deepest sensor (31 ft) within 5 days of application. Molasses was consumed within the top 13.5 feet of soil and greater molasses concentrations and/or more frequent flooding events may be required to treat deeper contamination. Use of the bioremediation method described herein could prevent explosives residuals from migrating to ground water and off-site.