Investigating organic fouling of ultrafiltration membranes using RP-HPLC fractionated SMP from an AnMBR and advanced QCM-D and LSPR analysis

Abstract

Anaerobic membrane bioreactors (AnMBRs) have emerged as an appealing technology for wastewater treatment. However, organic fouling, particularly by soluble microbial products (SMP), presents a major challenge to their operation. The characteristics of the organic fractions comprising SMP affect the degree and reversibility of membrane fouling. However, fractionating SMP to identify the components most responsible for fouling remains difficult. Advanced methods are required to investigate the interactions between organic matter and membranes. This study presents a robust method for fractionating SMP using reverse-phase high-performance liquid chromatography with a semi-preparative C4 reverse-phase column and a highly sensitive approach for investigating interactions between the membrane and organic matter using localized surface plasmon resonance (LSPR) analysis. Following optimization of the proposed method, the effect of each organic fraction on membrane fouling was investigated through ultrafiltration tests and by quartz crystal microbalance with dissipation monitoring (QCM-D) and LSPR analysis. The SMP was separated into five fractions that differed mainly in hydrophilicity and thus each affected fouling differently. However, the original SMP mixture collected from an AnMBR caused the most severe fouling and exhibited the highest accumulation on the QCM-D and LSPR membrane-mimetic sensors. This result is attributed to synergistic fouling and adsorption effects. The LSPR dry mass adsorption correlated most strongly with the ultrafiltration membrane fouling results. Combining LSPR analysis, which measures dry mass accumulation, with QCM-D, which measures hydration and viscoelasticity, enables the comprehensive assessment of fouling potential and fouling evolution over time.