Fate and UF fouling behavior of algal extracellular and intracellular organic matter under the influence of copper ions

Abstract

Copper ion plays an important role in the outbreak of algal blooms. The aim of this research was to investigate the fate and fouling behavior of algal extracellular organic matter (EOM) and intracellular organic matter (IOM) under different copper concentrations during ultrafiltration (UF). Under the lowest copper concentration of 0.01 μmol/L, both the EOM and IOM caused the largest decrease in filtration flux, followed by EOM under high copper concentrations of 0.3 μmol/L and 0.1 μmol/L; less membrane fouling was induced by IOM under a copper concentration of 0.3 μmol/L than under a copper concentration of 0.1 μmol/L. More reversible fouling (Rre) was induced by EOM/IOM at the lowest copper concentration of 0.01 μmol/L than under the other two copper concentrations, whereas more membrane fouling was induced by EOM than by IOM under the different copper concentrations. Fluorescence excitation-emission matrices-parallel factor analysis (PARAFAC) indicated that fouling by the protein-like components in EOM was more irreversible under 0.01 μmol/L copper than under 0.1 μmol/L and 0.3 μmol/L copper. However, the fouling by this component was more reversible in the IOM solutions than in the EOM solutions. The amount of macromolecular biopolymers was highly correlated with the total and reversible membrane fouling during the EOM/IOM filtration, whereas a weaker correlation (r2) between the humic-like organics and membrane fouling was determined by Pearson's correlation matrix analysis. High-performance size exclusion chromatography (HPSEC) combined with peak-fitting prediction was suggested to be more suitable for membrane fouling implication in algal water treatment.