Optimizing the formation of aerobic granular sludge and enhanced pollutant removal efficiency in a constant current variable voltage electric field.

Aerobic granular sludge (AGS) disintegration occurs during long-term operation, decreasing particle settling performance and deteriorating the pollutant removal effect. Therefore, this experiment proposes an electric field synergistic AGS construction to improve the strength of particles and the efficiency of nitrogen and phosphorus removal. The study revealed that under the influence of an electric field, iron ions dissolved from the iron electrode and phosphate formed mineral nuclei inside the particles, which effectively increased the average size of the particles and increased the protein content of extracellular polymeric substances (EPS). The experimental results demonstrated that including Fe–C electrodes in the electric field group increased the TN removal rate to 86.65%, surpassing the rates observed in the blank without an electric field and C–C electrode electric field groups by factors of 1.13 and 1.11, respectively. Under the electric field, AGS enriched some functional microorganisms for denitrogenation, thus improving total nitrogen removal efficiency. Furthermore, the phosphorus removal efficiency in the electric field group featuring Fe–C electrodes exhibited a notable enhancement, reaching 90.16%. This improvement was 1.71 and 1.62 times that of blank without an electric field and C–C electrode electric field groups, respectively. The phosphorus removal efficacy of electrode-released iron is distinct from that of exogenous ferrous sulfate, with the former demonstrating superior activity and pronounced phosphorus removal capabilities. Therefore, this study comprehensively revealed AGS construction mechanism and pollutant removal efficacy under the electric field's synergistic effect. [Display omitted] • Dissolved iron ions from the iron electrode form Ca 2 Fe 2 O 5 with phosphorus increasing the strength of AGS. • The electric field stimulated the secretion of EPS and accelerated the AGS granulation process. • The electric field enhances the removal of nitrogen and phosphorus by AGS. • The electric field enriched some bacteria with synchronous nitrification denitrification. [ABSTRACT FROM AUTHOR]