Electrochemical oxidation of methyl orange, malachite green and 2,4-dinitrophenol were performed in the presence of varying concentrations of inorganic anions and oxidizing agents. Methyl orange oxidation was positively affected by carbonate (<300 mg L-1), H2PO4- (100-500 mg L-1), H2O2 (<300 mg L-1) and S2O82- (>400 mg L-1). Carbonate (>400 mg L-1), bicarbonate (100-500 mg L-1), nitrate (>300 mg L-1) and H2O2 (> 400 mg L-1) inhibited the COD removal efficiency of methyl orange. Electrochemical oxidation of malachite green was inhibited by carbonate (100-500 mg L-1), bicarbonate (100-500 mg L-1), nitrate (>400 mg L-1) and H2PO4- (>400 mg L-1), whereas nitrate (<300 mg L-1), H2PO4- (<300 mg L-1), H2O2 (<400 mg L-1) and S2O82- (100-500 mg L-1) increased the COD removal efficiency. The COD removal efficiency of 2,4-dinitrophenol was inhibited by bicarbonate (100-500 mg L-1), nitrate (<300 mg L-1) and H2O2 (500 mg L-1). A positive effect on the COD removal efficiency of 2,4-dinitrophenol was obtained in the presence of H2PO4- (100-500 mg L-1), H2O2 (<400 mg L-1) and S2O82- (100-500 mg L-1). The degradation of 2,4-dinitrophenol was unaffected by the presence of carbonate. Addition of sulphate had no effect on the COD removal efficiency of all the three contaminants. (C) 2015 Elsevier B.V. All rights reserved.