Fouling of extracellular algal organic matter during ultrafiltration: The influence of iron and the fouling mechanism

Abstract

In this study, membrane fouling and the mechanism of algal extracellular organic matter (EOM) due to various trace heavy metals (iron) during ultrafiltration (UF) was investigated in detail. In both early and late exponential growth phases, the results indicated that the membrane fouling caused by EOM at low iron concentrations in this study was more severe than that at high and normal iron concentrations. Low iron concentrations produced the highest total (R) and reversible fouling resistance (Rre), of which Rre was higher, followed by membrane resistance (Rm), and irreversible fouling resistance (Rir). The analysis of EOM characteristics indicated that low iron in this study stimulated the growth of algae beyond high and normal iron concentrations, including increases in chlorophyll a; protein (tryptophan-like and tyrosine-like organic matter) content; and macro, medium and small molecular organic matters. Humic-like organics were more synthesized under high iron concentrations. Analyses of membrane fouling behavior illustrated that cake formation was the major fouling mechanism for the three iron concentrations, and it accounted for a greater proportion of fouling in the low iron concentration than in the other two iron concentrations; cake resistance played a more critical role in the late exponential growth phase than in the primary exponential phase.