Biological treatment of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX), and the hydrolysates of RDX and HMX

Biological treatment of 2,4,6-trinitrotoluene (TNT), hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX), and octahydro-1,3,5,7-tetranitro-1,3,5,7-tetrazocine (HMX) was investigated in anaerobic systems for comparison with RDX and HMX treatment in activated sludge (AS) systems following hydrolysis. The AS systems (0.74% total solids) denitrified 17 and 19 additions of RDX and HMX hydrolysate waste, respectively, over 24 days. The AS reactors required 8 hours (RDX hydrolysate) and 5 hours (HMX hydrolysate) to remove 95.5% and 93.9% of hydrolysate nitrite (500 ppm).; Anaerobic treatment of TNT, RDX, and HMX was investigated using biochemical methane potential (BMP) and high anaerobic solids assays (HAS) with and without TNT acclimation.; Anaerobic sludge was generated from reactors charged with waste activated sludge and horse manure (3:2 ratio based on dried solids). Reactors were maintained at 35 C, had a hydraulic residence time of 24 weeks and were fed Purina Dog Chow at a rate of 0.85 g/L/day.; Total gas generation data from BMP assays indicated no sludge acclimation effect within the TNT, HMX and control treatments. A decrease in gas production rates was noted for RDX treatments of TNT acclimated sludge solids (P = 0.026).; Lower total gas yields were observed in TNT treatments when compared to control treatments (P < 0.001). Raw RDX and HMX hydrolysate treatments resulted in lower gas evolution rates compared to control treatments (P < 0.0001). Activated sludge pretreatment of RDX and HMX hydrolysates eliminated these differences.; The TNT acclimation of sludge solids increased TNT transformation rates in HAS assays (P < 0.001). Acclimated systems required 30 minutes to transform 59 ppm TNT versus 43 ppm in non-acclimated systems. Additionally, acclimated systems removed aminodinitrotoluene byproducts in 120 minutes versus 960 minutes for the non-acclimated systems.; No sludge effect was noted for RDX and HMX treatments. The RDX treated reactors (100 ppm dose) transformed 81.8 ppm RDX in 960 minutes. The HMX treated reactors (100 ppm dose) transformed 69.4 ppm HMX in 5760 minutes. Comparison of AS to HAS systems indicated a greater treatment potential for RDX (18 times) and HMX hydrolysates (140 times) in the AS systems with hydrolysis.