Effective removal of metformin from wastewater through biological treatment technology has been a challenging issue. Enhancing electron transfer was demonstrated to be an effective measure to improve the removal of refractory pollutants from wastewater. In this study, the effects of a microbial electrolysis cell (MEC) in strengthening an adsorption-biological coupling reactor during the drying period in treating metformin wastewater were investigated, along with its microbial community and metabolism. Compared to without a MEC, the removal rates of chemical oxygen demand (COD), total phosphorus (TP), ammonia-nitrogen, and metformin all increased with the increase of voltage
at 1.0 V, their removal rates were 77.26 %-91.45 %, 59.22 %-75.85 %, 79.52 %-91.56 %, and 57.45 %-70.15 % respectively. The main dominant bacteria in the two groups were Pseudomonadota (28.14 %-75.72 % and 13.51 %-84.79 %, respectively) and Actinobacteria (16.27 %-67.10 % and 6.11 %-84.27 %). The MEC increased the relative abundance of glycolytic glucokinase and pyruvate kinase genes. In nitrogen metabolism, dissimilar nitrate reduction was strengthened. In addition, the relative abundance of the functional genes involved in phosphate translocation, electron transport-linked phosphorylation, and phosphate metabolism were all increased after voltage addition, which promoted microbial activity and increased the TP removal rate.