Alkaline hydrolysis of explosives
VanEngelen, Catherine Elizabeth
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In the United States, ammunitions testing and manufacturing facilities must transform unused explosives into non-hazardous materials for disposal. 2,4,6- trinitrotoluene (TNT) is an explosive that has been found as a soil and groundwater contaminant at numerous ammunitions testing sites. Unused quantities of nitrocellulose (NC), another explosive, have also been accumulating at ammunitions manufacturing facilities. Transformation of both TNT and NC to non-explosive compounds has been studied using either chemical or biological approaches, each with limited success. With respect to TNT, the use of alkaline hydrolysis (degradation at high pH) as a chemical treatment had been tested at room temperature (20°C) under conditions where the hydroxide concentration exceeded that of TNT (pH > 10). These high hydroxide conditions were not directly amenable to biological treatment of the hydrolysis products. This study found that alkaline hydrolysis was effective for complete degradation of TNT at elevated temperatures (60°C and 80°C) when the concentration of TNT was less than the hydroxide concentration (pH 9 and 10). The resulting solution, or hydrolysate, contained no TNT. This hydrolysate was used as the carbon and nitrogen source for an aerobic bacterial enrichment from the Bozeman wastewater treatment plant. With respect to NC, the back-log of accumulated NC necessitates a degradation method that will process high NC concentrations (200g/L). Alkaline hydrolysis at 60°C was used with very high hydroxide concentrations to rapidly degrade high concentrations of NC, producing high nitrate and nitrite concentrations. The NC hydrolysate was neutralized and spiked into a denitrifying culture which was able to reduce both nitrate and nitrite. The goal of this work was to develop a dual component chemical-biological system for complete degradation of the explosives TNT and NC, which was achieved using alkaline hydrolysis as the chemical component and bacterial wastewater treatment enrichments as the biological component.