A consecutive electrocoagulation and electro-oxidation treatment for pulp and paper mill wastewater

In this work, electrocoagulation (EC), electro-oxidation (EOx), consecutive electrocoagulation electro-oxidation (EC&EOx) and combined electrocoagulation electro-oxidation (EC/EOx) treatment methods were executed for the pulp and paper mill wastewater. The performances of the methods were compared in terms of pollutant removal and energy consumption amounts. Batch electro-reactor was used with Al and Fe electrodes for EC stage and graphite electrodes for EOx stage. The initial process conditions were electrical conductivity in 2.10 mS/cm, pH in 5.82, temperature in 20 degrees C and constant current intensity in 1.22 A. The highest removal of turbidity, color and chemical oxygen demand (COD) was obtained as 99%, 100% and 90% respectively for both EC&EOx and EC/EOx processes with the utilization of Al electrodes. Although EC&EOx method was found to be more energy efficient with 26.23% less energy consumption than EC/EOx method, usage of a single reactor for EC/EOx technique has been considered as a more feasible method for treatment because of the initial investment cost and ease of application. Effects of initial pH, electrical conductivity, temperature and current intensity on pollutant removal and energy consumption by means of EC/EOx technique were also investigated and optimal operational parameters were determined as 6, 5 mS/cm, 20 degrees C and 1A respectively.