Integration of membrane bioreactor with a weak electric field: Mitigating membrane fouling and improving effluent quality targeting low energy consumption

The electrical assisted MBR (EMBR) has been employed to improve the water quality and solve the fouling problem. However, advanced material-based electrodes or high operation voltage bring difficulties for the practical application of EMBR. Herein, a weak electric field generated by titanium electrodes was employed to establish an EMBR and the fouling mechanism was investigated in detail. The results showed that introduction of a weak electric field at voltage of 0.1 V/cm and current density of 7 μA/cm² efficiently decreased the extracellular polymeric substances (EPS) content by over 40 % as such extended the service time of MBR by more than 20 %. Specifically, the weak electric field reduced the relative abundance of Bacteroidetes, known for secreting proteinaceous EPS, by 38.61 %, and increased relative abundance of Patescibacteria with EPS decomposition by 6.73 times, thus effectively reducing the EPS concentration. Further KEGG pathway analysis revealed that electric field accelerated enzymatic reactions and promoted microbial metabolism of carbohydrate and amino acid. Furthermore, this weak field reduced the sludge deposition on membrane by increase of the electrostatic repulsion and the irreversible fouling was mediated. According to the composition of the fouling layer, a corresponding cleaning scheme was applied. This EMBR consistently produced high-quality effluent in all cycles, with 99.31 % COD, 98.73 % NH₄⁺-N, 85.87 % TP and 92.66 % TN removals. In conclusion, the weak electric field endow EMBR exceptional anti-fouling ability and superior effluent quality under lower energy consumption.