Sequencing Batch Reactor Biodegradation of Hydrolyzed Sarin as Sole Carbon Source

The chemical nerve agent sarin (o-isopropyl methylphosphonofluoridate) was hydrolyzed at 7.18 weight percent in aqueous sodium hydroxide yielding primarily o-isopropyl methylphosphonic acid (IMPA). This hydrolysate was diluted and fed as sole carbon source to activated sludge in an aerobic sequencing batch reactor. Feed chemical oxygen demand (COD) concentrations ranged from approximately 2500 mg/L (initial) to 5000 mg/L (final). The reactor was operated essentially on a 15-day hydraulic residence time. Overall COD removal efficiency was 86.2% and the IMPA in the feed was converted to methylphosphonic acid. MICROTOX® and Daphnia magna aquatic toxicity testing showed the effluent to be of very low toxicity to aquatic test organisms. The final MPA product was effectively absorbed by Phoslock?, which is a lanthanide modified clay.