Optimization of electrocoagulation parameters for enhanced wastewater treatment

Abstract

This thesis presents a comprehensive experimental and statistical investigation into the optimisation of electrocoagulation (EC) parameters for the treatment of slaughterhouse wastewater. A full-factorial response surface methodology (RSM) design with four levels each of hydraulic retention time (HRT) and current density was employed to systematically analyse their effects on pollutant removal efficiency and energy consumption. A total of sixteen experimental runs were performed, with key response variables including chemical oxygen demand (COD), turbidity, colour, E. coli (as an indicator of microbial contamination), electrical conductivity, and power usage. The experimental data were fitted to second-order polynomial models, which successfully captured the relationships between operating conditions and treatment performance. Statistical analysis revealed that both linear and quadratic terms of HRT and current density were significant predictors (p < 0.05) for all major removal indicators, with R² values exceeding 0.90. This confirmed the robustness of the models and their capacity to describe system behaviour within the tested range. The highest removal efficiencies were obtained under conditions that balanced sufficient treatment time with adequate coagulant production, while also considering energy input. Confirmatory experiments validated the model predictions, reinforcing the reliability of the proposed equations. Additionally, observed shifts in pH from near neutral (~6.8) to mildly alkaline (~9.0) supported the electrochemical mechanisms involved, including hydroxide ion generation and enhanced microbial inactivation. Importantly, actual aluminium dissolution rates exceeded theoretical values predicted by Faraday's law, suggesting possible contributions from mechanical erosion or parasitic reactions. Power consumption varied notably depending on the electrical wiring setup, indicating a clear opportunity for system optimisation through circuit redesign. The study concludes that optimal EC performance requires a balanced application of electrical and hydraulic inputs. It recommends further exploration of vertical flow reactor designs, alternative wiring configurations to reduce power draw, and integration of continuous sludge removal systems to maintain effective treatment volume.