Roles of Fe3O4 and PANI coated membranes for fouling mitigation in membrane bioreactor: Long-term treatment performance and fouling mechanisms

Abstract

This study investigates the role of nanoparticles-coated membranes in membrane bioreactors (MBR) for wastewater treatment, focusing on treatment efficiency and fouling behaviors. In this study, PANI, Fe₃O₄ and Fe₃O₄@PANI were coated onto flat-sheet PVDF membranes via a simple dip-coating method. The modified membranes demonstrated COD removal rates of 93.8–95.9 % (PANI/PVDF), 93.1–95.1 % (Fe₃O₄/PVDF), and 88.9–95.2 % (Fe₃O₄@PANI/PVDF) were comparable to the pristine PVDF membrane (91.2–95.1 %), with similar ammonia and phosphorus removals over 250 days of operation. Fouling behavior analysis revealed that while the pristine PVDF membrane's fouling rate increased by 1.43 times as operated flux increased (1.60 kPa d⁻¹ at 15 LMH to 2.29 kPa d⁻¹ at 20 LMH), whereas the modified membranes exhibited only slight increases, less than 1.3 times. Surface roughness measurements showed that PANI/PVDF (R_a = 381.7 nm), Fe₃O₄/PVDF (R_a = 335 nm), and Fe₃O₄@PANI/PVDF (R_a = 377.1 nm) had reduced fouling susceptibility compared to pristine PVDF (R_a = 473.5 nm), indicating reduced extracellular polymeric substance (EPS) and soluble microbial product (SMP) deposition. These findings highlight the potential of nanoparticle-modified membranes to support elevated fluxes with minimal impact on treatment performance and fouling resistance, offering promising implications for prolonged and stable MBR operation.