Biodegradation of sulfur mustard hydrolysate in the sequencing batch reactor

The United States Army is currently examining chemical neutralization followed by biodegradation for disposal of the chemical warfare agent sulfur mustard. The acidic hydrolysis of sulfur mustard (“mustard gas”, 2,2′-dichlorodiethyl sulfide), yields a detoxified and biodegradable product typically containing from 80 to 95% thiodiglycol. The hydrolyzed product was typically amended with 1,450 mg/L of ammonium chloride (NH4Cl), 280 mg/L of potassium phosphate monobasic (KH2PO4), and mineral salts and fed to aerobic Sequencing Batch Reactors (SBRs). The SBRs were operated with 3-5 hour aerated Fill, 17-18 hour React, 1 hour Settle and 1 hour Draw periods. The efficiency of carbon removal was greater than 90% and the effluent was non-toxic as determined by aquatic toxicity tests.