This study was done to evaluate the degradation and mineralization of formaldehyde (approximate to 8000 mg/L) in an electro-Fenton process (EFP) in combination with biodegradation. In the first step, the influence of several important parameters including solution pH, current density. H2O2 concentration, and reaction time were tested on the efficiency of the EFP in degradation and mineralization of formaldehyde in a concentrated solution. The optimum pH and current density was found to be around 10 and 8.5 mA/cm(2), respectively. The formaldehyde degradation in the EFP increased with an increased H2O2 concentration. Under optimum pH and current density, the complete degradation and 51% mineralization of formaldehyde was attained in the EFP using a H2O2 concentration of 10 mM/min at a short reaction time of 6 min. The biodegradation of the effluent of EFP under optimum conditions (complete formaldehyde removal) was also tested. The results demonstrated that the concentration of the EFP effluent could be efficiently reduced in the bioreactor to below 50 mg/L after a biodegradation time of 16 d. Accordingly, results showed that EFP was a very efficient process for degradation and mineralization of a high concentration of formaldehyde so that its effluent could be efficiently post-treated with a biological process. (C) 2012 Elsevier B.V. All rights reserved.