Multiphysics CFD analysis of gas-liquid-coagulant interactions in a continuous-flow electrocoagulation reactor for industrial laundry wastewater treatment

Continuous-flow electrocoagulation (EC) is a promising technique for treating industrial laundry wastewater, but the coupled roles of hydrodynamics, hydrogen evolution, and coagulant transport remain insufficiently understood. This study develops a coupled computational fluid dynamics (CFD) model to analyze liquid flow, gas generation, and the transport of an equivalent aluminum-based coagulant species in a continuous-flow EC reactor. The model combines a multiphase mixture approach with species transport to examine how bubble-induced mixing modifies local flow structure and coagulant dispersion under representative operating conditions. Results show that including the gas phase suppresses low-velocity regions, improves coagulant distribution, and enlarges the effective reaction zone compared with single-phase predictions. Model predictions were evaluated against residence time distribution (RTD) data and bulk treatment indicators, showing agreement within 8% for mean residence time and consistency with COD removal above 80% and turbidity removal above 90%. An extended sensitivity analysis indicated that the reactor-scale conclusions are most sensitive to gas generation intensity, hydraulic loading, and electrode spacing. These findings provide preliminary reactor-scale insight into gas–liquid–coagulant interactions and continuous EC reactor behavior, although the model should be interpreted within its simplified physicochemical scope and as a basis for further validation and optimization studies. • Coupled CFD models flow, gas evolution, and coagulant transport. • Gas phase suppresses low-velocity zones in continuous EC reactors. • Bubble-induced mixing enhances coagulant dispersion in the reactor. • RTD prediction matches experimental results within an 8% margin of mean residence time. • Sensitivity emphasizes the roles of gas production and electrode spacing.