Phenolic wastewaters treatment by electrocoagulation process using Zn anode

Abstract Electrocoagulation using a Zn anode was applied for the first time to remove the organic load of a liquid effluent. Different operating conditions (pH, current density, distance between electrodes, nature of electrolyte and kind of cathode) were tested with synthetic phenolic wastewater, in order to optimise the process. Both the medium pH and the type of electrolyte that were used greatly affected the efficiency of the system, followed by the influence of the current density and the cathode material, in a lesser extent. The effect of the distance between electrodes was quite negligible. Furthermore, a sequence of fed-batch trials involving the electrodes reuse showed almost constant activity during the operation time. The optimum operating conditions achieved were initial pH of the effluent equal to 3.2, current density of 250 A/m 2 , distance between electrodes of 1.0 cm and 1.5 g/L of NaCl. Moreover, the Zn anode/stainless steel cathode pair revealed the most interesting results. These parameters led to 84.2% and 40.3% of total phenolic (TPh) content and chemical oxygen demand (COD) removal, respectively. In addition, the depuration of a filtered real olive mill effluent without NaCl addition achieved the abatement of up to 72.3% of TPh and 20.9% of COD. An energy consumption of 40 kW h/m 3 and 34 kW h/m 3 was observed for the treatment of the simulated and the real wastewater, respectively. Furthermore, the ecological impact of the treated effluent was detected by bio-luminescence techniques. This study shows the potentiality of the electrocoagulation process as a pre-treatment of other methods, namely the electrochemical oxidation, to ensure the legal limits values of the wastewater to be discharged into the aquatic environment regarding their organic load.