Characteristics of algogenic organic matter generated under different nutrient conditions and subsequent impact on microfiltration membrane fouling

Abstract

This work investigated the characteristics of algogenic organic matter (AOM) that was produced by blue-green algae grown under different nitrogen to phosphorus ratios (1N:1P, 1N:2P, 1N:10P, 2N:1P). Subsequently, the potential for AOM microfiltration (MF) membrane fouling under these scenarios was evaluated. The results showed that algae grew differently under various N/P ratios. Microcystis aeruginosa in 1N:10P and 1N:2P grew much better than those in 1N:1P. When constant phosphorous concentrations were maintained, no obvious effect was observed on the accumulation of algal intracellular organic matter. The amount of AOM released from M. aeruginosa was also affected by the N/P. AOM fraction analysis showed that the neutral hydrophilic fraction (N-HPI) was the main component of AOM; with lower N/P ratios, the proportion of hydrophilic AOM increased. Moreover, molecular weight (MW) distribution discrepancies existed among different AOMs. MF membrane fouling by AOM may also be influenced by N/P variations. AOM at 1N:10P exerted the strongest impact on membrane fouling, followed sequentially by 1N:2P, 1N:1P and 2N:1P. According to the analysis of the excitation–emission matrices (EEMs) and the MW distribution of membrane filtration, the membrane fouling potential of AOM seemed to be mainly associated with polysaccharide-like or protein-like substances of large MW.