Alachlor dechlorination prior to an electro-Fenton process: Influence on the biodegradability of the treated solution

•91% of alachlor mineralization after 3 h in Electro-Fenton (EF) optimized conditions.•OH radicals responsible for 63% of mineralization, no influence of Cl atom.•Similar mechanisms for alachlor and deschloroalachlor radical oxidation.•No biodegradation of alachlor and deschloroalachlor by fresh activated sludge.•Better BDO5 enhance for ER-EF mainly due to the absence of chlorinated compounds.