On the performance of electrocoagulation treatment of high-loaded gray water: kinetic modeling and parameters optimization via response surface methodology

Abstract

This study explores the electrocoagulation (EC) treatment of high-loaded gray water (HLGW), with the goal of optimizing operating parameters such as current densities (C_d) and EC time. Moreover, the research examines the kinetics involved in the removal of COD, color, and turbidity from HLGW. Various HLGW samples were treated at different current densities over a 90-min EC period. Kinetic analysis shows that COD removal follows a second-order model, while turbidity and color removal adhere to a pseudo-first-order model, with parameters dependent on C_d. The findings indicate that pollutant removal improves with longer EC treatment times and higher C_d values. At lower C_d levels, removal efficiencies for COD and color are relatively low, even with a 90-min EC treatment. However, at a higher C_d (20 mA/cm²), there is a substantial increase in removal efficiency, with 85% removal for both COD and color within the same duration. Turbidity is completely removed when the C_d is set to 10 mA/cm² after 45 min of EC treatment. These results highlight that achieving high pollutant removal from HLGW requires high energy consumption. As a result, combining EC with other processes, either as a pre-treatment or post-treatment step, may address the challenges faced by standalone EC systems. Using response surface methodology (RSM), optimal operating conditions were determined, achieving pollutant removals of 76.4% for COD, 80.5% for color, and 98.5% for turbidity, with a minimum energy consumption of 5.07 kWh/m³ at an EC time of 44 min and a C_d of 15.5 mA/cm².