The successful application of bio-electrocatalyzed system (BES) to wastewater treatment inevitably depends on the improvement of performance and the reduction of costs at a scale-up level. One efficient way to achieve these goals is to couple BES with traditional anaerobic processes to industrial wastewater treatment. Here we developed a hybrid anaerobic system built-in with electrode modules (HAR-BES, 30 L) as an inexpensive but high-performance process for azo dye containing wastewater treatment. HAR-BES showed faster start-up, 10% higher azo dye decolorization efficiency, and 20% higher COD removal efficiency than an anaerobic reactor (AR) without electrode modules. Microbial community analysis showed functional diversity in electrode biofilm and sludge samples. Geobacter and Syntrophus, which would account for electrode respiration and reduction of azo dye, respectively, were dominant in electrode biofilms. Tracer experiments and modeling of residence time distribution indicated that the fluid pattern in HAR-BES was close to plug flow. Simulation of computational fluid dynamics showed faster water velocity near electrode modules and better sludge expansion in HAR-BES than AR. This study proved that HAR-BES improved anaerobic wastewater treatment comprehensively through the analysis of chemicals, microbial community, and modeling of fluid pattern.