2-STAGE BIOTRANSFORMATION OF 2,4,6-TRINITROTOLUENE UNDER NITROGEN-RICH AND NITROGEN-LIMITING CONDITIONS

An anaerobic fluidized-bed granular activated carbon bioreactor in ser ies with an activated-sludge reactor was used to treat a wastewater co ntaining 100 mg/L 2,4,6-trinitrotoluene (TNT). The performance of the system was evaluated under both nitrogen-rich and nitrogen-limiting co nditions. When 18 mg/L ammonia-nitrogen was supplied to the system, th e mixed anaerobic culture completely transformed the TNT to unknown pr oducts. Effluent ammonia-nitrogen routinely was more than 21 mg/L, and nitrite was also detected in the anaerobic reactor effluent, possibly indicating two distinct methods of nitrogen removal from the ring. Th e effluent from this reactor was treated further in an activated-sludg e system. A significant fraction of the TNT transfer mation products w as oxidized in the aerobic stage, resulting in recovery of 82% of infl uent TNT-nitrogen and at least 73% TNT-carbon mineralization in the sy stem. When the anaerobic reactor received only TNT as a nitrogen sourc e, anaerobic reactor effluent ammonia levels remained above 3 mg/L, bu t nitrite was not detected. The resulting TNT biotransformation produc ts could not be completely identified, but they did persist in the fin al effluent. The inability of the activated sludge to effect further t ransformation of some of these compounds was quantified as a substanti al reduction in inorganic nitrogen recovery. Only 55% of influent TNT- nitrogen was recovered in the system during the nitrogen-limited opera tion.