Molasses enhanced phyto and bioremediation treatability study of explosives contaminated Hawaiian soils

Abstract

h i g h l i g h t sNatural degradation of RDX is very slow and its release into the environment is a concern. Molasses enhances biodegradation of RDX and complete degradation occurred within few weeks. Low molasses dose of 1:40 (molasses to water ratio) was as effective as the higher dose (1:20). The combination of Guinea Grass (Panicum maximum) and molasses did not improve RDX degradation. Addition of molasses to soil in army training ranges can prevent migration of RDX to groundwater and off-site. a r t i c l e i n f o The energetics in the soil were royal demolition explosive (RDX) and high-melting explosive (HMX). Among the 6 treatments employed in this study, enhanced removal of RDX was observed from treatments that received molasses and went to completion. The RDX degradation rates in treatments with molasses diluted 1:20 and 1:40 were comparable suggesting that the lower dose worked as well as the higher dose. Treatments without molasses degraded RDX slowly and residuals remained after 15 weeks. The bacterial densities in molasses-treated units were much greater than those without molasses. Phytoremediation alone seems to have little effect on RDX disappearance. For HMX, neither bioremediation nor phytoremediation was found to be useful in reducing the concentration within the experimental period. The concentrations of nitrogen and phosphorous in the soil did not change significantly during the experiment, however, a slight increase in soil pH was observed in all treatments. The study showed that irrigating with diluted molasses is effective at enhancing RDX degradation mainly in the root zone and just below it. The long term sustainability of active training ranges can be enhanced by bioremediation using molasses treatments to prevent RDX deposited by on-going operations from migrating through the soil to groundwater and off-site.

Right on target: using plants and microbes to remediate explosives

“…But few studies have yet investigated the effect of amendments for phytoremediation on explosives. A laboratory study (Lamichhane et al 2012) showed that the application of molasses to open burn/detonation areas enabled Guinea Grass (Panicum maximum) to remediate RDX, with plant and microbial communities fully remediating soil contaminated with 1.3 mg/kg RDX within the 15-week study. These promising results show that amendments can help remediation, but experiments are needed to understand the longevity of amendment-induced effects.…”

Alkaline hydrolysis of hexahydro-1,3,5-trinitro-1,3,5-triazine: M06-2X investigation

“…For example, alkaline hydrolysis may play an active role in the in situ natural attenuation of RDX in coastal seawaters (Hoffsommer and Rosen, 1973;Monteil-Rivera et al, 2008). Various technologies, such as treatment with iron metal (Wanaratna et al, 2006), chemical reduction using buffered sodium hydrosulfite (Luo et al, 2012), phytoremediation (Lamichhane et al, 2012;Panz and Miksch, 2012), photolysis (Hawari et al, 2002), adsorption by activated carbon (Wujcik et al, 1992), in situ bioremediation (Waisner et al, 2002), hydrolysis under different conditions (Hoffsommer et al, 1977;Croce and Okamoto, 1979;Heilmann et al, 1996;Balakrishnan et al, 2003;Hwang et al, 2004Hwang et al, , 2006Davis et al, 2007;Larson et al, 2008;Gent et al, 2010), and electrochemical decomposition (Gent et al, 2010) have been investigated as possible methods to treat RDX-contaminated water and soil for safe removal of nitramine from the environment.…”

Improved TNT detoxification by starch addition in a nitrogen-fixing Methylophilus-dominant aerobic microbial consortium

“…For mixed culture conditions, however, simple carbon sources may not be effective in stimulating the growth of a target group of degradative bacteria because simple carbon compounds are mainly consumed by copiotrophic non-degradative bacteria rather than by relatively slow-growing degraders [22,27,28]. To maintain the diversity and activity of microbial degradation in consortia or mixed cultures, it is practical and cost-effective to use slow-releasing complex carbon sources, such as molasses and starch [17,22,29,30]. In previous TNT degradation studies, the addition of molasses improved the rate of aerobic TNT degradation but not TNT detoxification, exhibiting the accumulation of potentially toxic TNT degradation intermediates [3,23,[31][32][33].…”