Removal performance and mechanism for a three-dimensional electrode system treating biochemical effluent of a wastewater treatment plant

With the increasingly strict discharge requirements, it is urgent for wastewater treatment plants (WWTPs) to find an efficient and feasible technology for advanced treatment. A three-dimensional (3D) electrode system was used to treat the real biochemical effluent of a WWTP collecting industrial and domestic wastewater in the present study. The 3D electrode system had the best performance at a current density of 2 mA/cm² and an electrode distance of 3 cm. The kinetic analysis showed that the organic pollutant degradation conformed to pseudo-first-order kinetics. The COD removal of the 3D electrode system was more than twice that of the two-dimensional (2D) electrode system, and the energy consumption was 46.56% less than that of the 2D electrode system. By measuring the adsorption capacity and the electrocatalytic ability of the system to produce strong oxidizing species, it was demonstrated that granular activated carbon (GAC) had the synergy of adsorption and electrochemical oxidation, and ·OH playing the dominant role in oxidizing pollutants. At the same time, the organic contaminants adsorbed on GAC could be degraded. Finally, the adsorption-electrochemical oxidation mechanism was proposed. The above results highlighted that the 3D electrode system was a promising alternative method in the application of advanced treatment for WWTPs.