Removal of tetracycline hydrochloride from water based on direct anodic oxidation (Pb/PbO2 electrode) coupled to activated sludge culture

The removal of tetracycline hydrochloride by an electrochemical oxidation on Pb/PbO2 electrode and the feasibility of coupling anodic oxidation-activated sludge culture were examined. The effect of the operating parameters showed that tetracycline hydrochloride (TC) degradation was enhanced for increasing current density and decreasing dye concentrations. The operating parameters were then optimized through a central composite design (CCD). After performing a screening of the various factors, response surface analysis led to the following optimal conditions for the abatement of the dissolved organic carbon (DOC): 26 degrees C, 25 mA cm(-2), 100 mg L-1 and 720 rpm for the temperature, the current density, the initial antibiotic concentration and the agitation speed, respectively. Under these conditions, 86.7% of the dissolved organic carbon was removed. To ensure a significant residual organic content for activated sludge culture after electrochemical pre-treatment, the biodegradability test and the biological treatment were performed on a solution electrolyzed at 40 degrees C, 13.75 mA cm(-2), 100 mg L-1 and 720 rpm, according to the total removal of tetracycline observed while 36.7% of the dissolved organic carbon (DOC) remained after electrolysis. The BOD5/COD ratio increased substantially from 0.028 initially to 0.41 after 5 h of electrochemical pre-treatment, namely slightly above the limit of biodegradability (0.4). A biological treatment was therefore performed aerobically in a mineral medium using 0.5 g L-1 of activated sludge for 30 days, leading to an overall decrease of 76% of the dissolved organic carbon (DOC) by means of the combined electrochemical pre-treatment and a biological treatment. (C) 2013 Elsevier B.V. All rights reserved.