The removal of a commercial solution of 2,4-D, U46D (R), was carried out by coupling an electrochemical oxidation and a biological process involving activated sludge. The similar electrochemical behavior of 2,4-D and U46D (R) highlighted their oxidation around 1.6 V/SCE and the feasibility of an electrochemical pretreatment. It was based on a home-made flow cell involving bare graphite felt electrode. To propose a consistent mechanism for 2,4-D oxidation, the indirect determination of (OH)-O-center dot has been performed and the absence of radicals formation during 2,4-D electrolysis was confirmed. Consequently, the proposed pretreatment can be considered as a 'direct' electrochemical process instead of an advanced electrochemical oxidation process. The impact of the flow rate on the pretreatment showed that 3 mL min(-1) was a good compromise between the pretreatment time and the electrolysis efficiency, since it led to an almost total degradation of the pollutant while its mineralization remained limited. At this flow rate and for 500 mg L-1 of 2,4-D, the energy cost was estimated at 5 kW h M-3. The biodegradability of U46D (R) solution was not significantly modified after electrolysis, most likely due to the presence of dimethylamine salt in U46D (R). Owing to the significant BOD5/COD ratio measured, a biological treatment of the commercial U46D (R) solution was however considered. The electrochemical pretreatment shortened the duration of the biodegradation. For non-pretreated U46D (R) (100 mg L-1 2,4-D), mineralization remained limited until 6 days of culture (33.7% DOC removal), and total removal of the DOC was observed after 8 days. For pretreated U46D (R), 63.7% decrease until the fifth day of culture was observed but total mineralization was not reached at the end of culture (72.1%). An overall mineralization yield during the coupled process of 82.1% was therefore reached. The presence of refractory compounds generated during the electrochemical pretreatment in small concentration was therefore shown. (C) 2014 Elsevier B.V. All rights reserved.