Treatment of hexahydro-1,3,5-trinitro-1,3,5-triazine (RDX) wastewater by combined process of electrocatalytic reaction and anoxic-oxic (A/O) activated sludge process was investigated. The degradation intermediates of RDX during the synergistic system of electrochemical reduction and electrochemical oxidation were analyzed by tandem mass spectrometry (MS/MS), and a pathway for electrocatalytic degradation of RDX was proposed. In order to remove RDX from the wastewater, an electrochemical system using TiO2-NTs/SnO2-Sb anode was applied to the pretreatment process. The effect of the operating parameters on the electrochemical process performance was studied. The electrocatalytic process removed 39.2% of COD and 97.5% of RDX, and increased biodegradability index from 0.18 to 0.51, which resulted in a great improvement in the biodegradability. The start-up and operation period for the anoxic-oxic activated sludge process were also investigated. As a conclusion, the toxic and refractory organic pollutants were effectively removed in the electrochemical pretreatment and this combined process was successfully employed. (C) 2011 Elsevier B.V All rights reserved.