Continuous electrocoagulation with aluminum electrodes: An efficient method for pollutant reduction in paper mill wastewater and sludge analysis

Electrochemical reactors play a vital role in scaling up wastewater treatment processes, with efficiency influenced by electrode material, reactor geometry, flow dynamics, power supply, and operational mode. This study investigated the continuous electrocoagulation treatment of paper mill wastewater using a reactor equipped with four aluminum electrodes. The effects of flow rate (0.1–0.6 L/min) and retention time on pollutant removal efficiency were examined. Effluent was continuously fed into the reactor via a peristaltic pump, ensuring controlled inflow and uniform distribution for optimal treatment conditions. Experimental results demonstrated that 80% removal of total dissolved solids, total organic carbon, chemical oxygen demand, and color was achieved under optimal conditions: a pH value of 5.0, a conductivity of 7.59 mS/cm, an electrode gap of 1.38 cm, a current density of 10.72 mA/cm2, a retention time of 120 min, and a flow rate of 0.1 L/min. The sludge generated during treatment was characterized using scanning electron microscopy, energy dispersive X-ray spectroscopy, X-ray diffraction, and Fourier transform infrared spectroscopy to assess its composition and potential for reuse or safe disposal. Additionally, the pollutant removal mechanism using aluminum electrodes was elucidated. This study provides a novel contribution by exploring a continuous-flow electrocoagulation system for pulp and paper mill wastewater treatment, an area with limited prior research, and by integrating detailed sludge characterization to evaluate treatment performance and resource recovery potential. These results underscore the effectiveness of continuous electrocoagulation for treating paper mill effluents, advancing sustainable wastewater management practices.