Mitigation of fouling in membrane bioreactor using the integration of electrical field and nano chitosan adsorbent

Abstract

The application of membrane bioreactors (MBRs) has emerged as an impressive solution to water scarcity. One of the main obstacles for MBR application is membrane fouling. This work studied the effect of the novel simultaneous application of electric field and positively-charged nano chitosan on membrane fouling. Four MBRs of 1 (control bioreactor), 2 (control bioreactor + electric filed), 3 (control bioreactor + nano chitosan) and 4 (control bioreactor + electric filed + nano chitosan) were evaluated. The results indicated that the concurrent use of voltage and nano chitosan better reduced the membrane fouling, decreased flux decline, and enhanced recovery ratios and membrane bioreactor performance index by nearly 43 % and 84 %, respectively. Meanwhile, the contents of soluble microbial products (SMP) and extracellular polymeric substances (EPS) were reduced from MBR1 to MBR4, respectively. Reduced zeta potential and increased particle sizes led to the change in the cake layer and fouling mitigation from MBR1 to MBR4, as observed through scanning electron microscope (SEM) images. Excitation-emission matrix (EEM) analysis showed that humic acid was adsorbed by both electro-coagulants and nano adsorbents, resulting in a substantial (approximately 97 %) reduction in membrane pore fouling for MBR4. The combination of electrocoagulation, electro-oxidation, and electrophoresis processes, along with adsorption by positively charged nano chitosan, effectively mitigated membrane fouling. The cathode induced a negative charge on sludge particles, subsequently facilitating their adsorption by the positively charged nano chitosan adsorbents. The results demonstrated that combining electric field and nano chitosan effectively suppresses membrane fouling, with relevance for forthcoming technological advancements.