Integrating electrochemical oxidation with anaerobic treatment of pulp mill wastewater to enhance organics removal

To meet environmental restrictions and reduce pollution in water bodies, more efficient wastewater treatment methods are required in biorefineries in the future. Meanwhile, to promote the bioeconomy, sustainable treatment methods, such as anaerobic treatment producing biogas, are needed. In this study, a novel integration of anaerobic treatment and electrochemical oxidation was applied to enhance the biological degradation of organic matter in thermomechanical pulping wastewater with simultaneous methane production. First, the wastewater was anaerobically treated in batch experiments with a soluble chemical oxygen demand (sCOD) removal of 49% ± 9% and a methane yield of 162 ± 16 mL-CH 4 /g-sCOD fed . The anaerobic effluent was further treated with electrochemical oxidation at different current densities and treatment times (3–15 mA/cm 2 for 0.3–4 h) to enhance the anaerobic biodegradability of the effluent. Finally, the electrochemical oxidation effluent was treated anaerobically to increase the total methane production and organic matter removal. Effluent from electrochemical oxidation, especially at higher current densities (10 and 15 mA/cm 2 ), inhibited methane production, likely due to the inhibitory intermediates produced during electrochemical oxidation. Finally, the optimized integrated process increased the overall organic matter removal of up to 93%. As this is one of the first research studies considering the integration of anaerobic treatment and electrochemical oxidation for treating real wastewater from the pulp and paper industry, the results of this study provide valuable information on how to improve organic matter removal during anaerobic treatment of bioindustry wastewater by integrating electrochemical oxidation into the process.