Mitigation of irreversible membrane biofouling by CNTs-PVDF conductive composite membrane

Biofouling has been one of the major challenges impacting the long-term stable operation of ultrafiltration processes. Irreversible biofouling is considerably more harmful than reversible biofouling. Conductive membrane, as a new technology to effectively mitigate membrane fouling, lack research of controlling irreversible biofouling. In this study, a carbon nanotube-polyvinylidene fluoride (CNTs-PVDF) conductive composite membrane was prepared using a two-step phase inversion method. The mitigation of irreversible biofouling by the conductive membrane was investigated during filtration of live and dead bacteria solutions. The results indicated that conductive membranes effectively mitigated the irreversible biofouling caused by both live and dead bacteria solutions. However, the conductive membrane's mitigation effect on irreversible biofouling caused by the live bacteria solution is significantly better than that of the dead bacteria solution. After the six-cycle filtration-backwashing experiments, compared with the condition without electricity applied, the irreversible biofouling growth rate of the conductive membrane decreased by 34.9 % for the live bacteria solution and 20.1 % for the dead bacteria solution, respectively. Additionally, the irreversible resistance decreased by 68.8 % for the live bacteria solution and 39.8 % for the dead bacteria solution. Furthermore, enhanced backwashing of the conductive membrane when used as an anode is more beneficial for controlling membrane biofouling than when it is a cathode. After backwashing at a voltage of 20 V for 1 min, the membrane flux recovery rate is 93 %. Almost all bacteria on the membrane are removed, and a very small number of residual bacteria have been killed.