Highly-Efficient Approach for Cleaning and Regenerating the Fouled Micro-Filtration Membrane of Membrane Bioreactors: Role of Enzyme and Restoration Mechanism

Abstract

Membrane fouling constitutes a significant impediment to the extensive implementation of membrane bioreactor (MBR) technology. The purpose of this work focuses on proposing a highly-efficient approach for cleaning and regenerating the fouled membrane of MBRs and revealing the corresponding mechanism. The proposed approach comprises three successive steps including physical, enzymatic, and chemical cleaning, with the results verifying the feasibility in effectively restoring the function of fouled membranes. By using two types of fouled membrane with different stored time, it was found that the compositions of foulants exhibited distinct variation, but they were mainly adsorbed and deposited on the membrane surface. Following cleaning and regenerating, the permeate flux of the membrane samples were all increased, but the samples with longer stored time showed more obvious improvement in increasing the permeate flux. As the cleaning process progresses, the porosity and pore diameters of the membranes incrementally enlarged, and moreover, the cleaning approach did not impact the membranes' thermal stability and mechanical qualities. The restoration mechanism was clarified, which indicated that, during the enzymatic cleaning step, amylase specifically recognized the foulants, eliminating them accurately and effectively, and also verified the key role of enzyme in diminishing the refractory foulants. This study has presented an eco-friendly and effective cleaning strategy that enhances the service life of membranes in MBRs, thereby advancing the development of sustainable membrane-based wastewater treatment technology.

Keywords: Regeneration of fouled membrane, Membrane fouling, Enzymatic cleaning, membrane bioreactor, Restoration mechanism.