Influence of the characteristics of soluble algal organic matter released from Microcystis aeruginosa on the fouling of a ceramic microfiltration membrane

Abstract

The influence of the characteristics of soluble algal organic matter (AOM) on the fouling of a 7-channel tubular ceramic microfiltration membrane (ZrO2–TiO2, 0.1μm) was investigated at lab scale. The AOM (3mg DOC/L) extracted from a Microcystis aeruginosa culture at three phases of growth (10, 20 and 35 days) all caused severe flux decline, and its fouling potential increased with increasing growth time. Size exclusion chromatography, fluorescence excitation–emission matrix spectra and organic matter fractionation showed that the high MW biopolymers were the major component determining the severity of the AOM fouling of the ceramic membrane. For the AOM at stationary phase (35 days), 0.45 and 1μm pre-filtration gave greater flux decline and hydraulically irreversible fouling than 5μm pre-filtration due to the denser foulant layer formed and greater amounts of small organic molecules entering membrane pores. However, the non-pre-filtered AOM (with algal cells) caused the greatest flux decline which was likely due to the presence of the high fouling potential cell surface organic matter. The addition of calcium to the feed solutions led to a marked improvement in flux and reduction in membrane irreversible fouling due to the lower fouling potential of the AOM-calcium complexes formed.