BACKGROUND: This study investigated the performance of anaerobic mesophilic granular sludge for the degradation of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX). Batch tests were conducted to investigate the effects of different supplements on the RDX degradation ability of anaerobic granular sludge, as well as the contributions of both physicochemical and biological processes involved in RDX removal from aqueous solution. RESULTS: Anaerobic granular sludge exhibited good performance in treating RDX as the sole substrate. Biodegradation was the main mechanism responsible for RDX removal. Ammonium had no significant promoting effect on the degradation process. The presence of glucose was found to enhance the degradation of RDX by anaerobic granular sludge, while the addition of sulfate and nitrate had adverse effects on the reductive transformation of RDX. CONCLUSIONS: Anaerobic granular sludge is capable of removing RDX from aqueous solution with high efficiency. This study showed good prospects for high-rate anaerobic processes in the treatment of munition wastewater. The results can be used for the design and optimization of high rate anaerobic systems for the elimination of RDX. (C) 2010 Society of Chemical Industry