Influence of hydrophobic/hydrophilic fractions of extracellular organic matters of Microcystis aeruginosa on ultrafiltration membrane fouling

Abstract

Fouling is a major obstacle to maintain the efficiency of ultrafiltration-based drinking water treatment process. Algal extracellular organic matters (EOMs) are currently considered as one of the major sources of membrane fouling. The objective of this study was to investigate the influence of different hydrophobic/hydrophilic fractions of EOM extracted from Microcystis aeruginosa on ultrafiltration membrane fouling at lab scale. The experimental data indicated that EOM exhibited similar flux decline trends on polyethersulfone (PES) and regenerated cellulose (RC) membranes but caused greater irreversible fouling on PES membrane than RC membrane due to its hydrophobic property. It was also observed that charged hydrophilic (CHPI) and neutral hydrophilic (NHPI) fractions caused greater flux decline over hydrophobic (HPO) and transphilic (TPI) fractions. For PES membrane, the order of the irreversible fouling potentials for the four fractions was HPO>TPI>CHPI>NHPI, while the irreversible fouling potentials of RC membrane were tiny and could be ignored. Fluorescence excitation–emission matrix (EEM) spectra and Fourier transform infrared (FTIR) spectra suggested that protein-like, polysaccharide-like and humic-like substances were the major components responsible for membrane fouling. The results also indicated that the irreversible fouling increased as the pH decreased. The addition of calcium to feed solutions led to more severe flux decline and irreversible fouling.