Abstract

The influence of the interaction between aquatic humic substances and the algal organic matter (AOM) derived from Microcystis aeruginosa on the fouling of a ceramic microfiltration (MF) membrane was studied. AOM alone resulted in a significantly greater flux decline compared with Suwannee River humic acid (HA), and fulvic acid (FA). The mixture of AOM with HA and FA exhibited a similar flux pattern as the AOM alone in the single-cycle filtration tests, indicating the flux decline may be predominantly controlled by the AOM in the early filtration cycles. The mixtures resulted in a marked increase in irreversible fouling resistance compared with all individual feed solutions. An increase in zeta potential was observed for the mixtures (becoming more negatively charged), which was in accordance with the increased reversible fouling resistance resulting from enhanced electrostatic repulsion between the organic compounds and the negatively-charged ceramic membrane. Dynamic light scattering (DLS) and size exclusion chromatography analyses showed an apparent increase in molecular size for the AOM-humics mixtures, and some UV-absorbing molecules in the humics appeared to participate in the formation of larger aggregates with the AOM, which led to greater extent of pore plugging and hence resulted in higher irreversible fouling resistance.

Highlights

  • Ceramic membranes are used increasingly in water and wastewater treatment due to their inherent advantages over conventional polymeric membranes such as narrow and well-defined pore size distribution, high surface hydrophilicity, and good mechanical and chemical stability [1]

  • algal organic matter (AOM) alone gave a significantly greater flux decline compared with the other organic compounds, with approximately 60% of flux decline obtained at the end of the single cycle filtration (Figure 1a)

  • The flux decline pattern for the AOM derived from M. aeruginosa and its mixtures with humic substance was comparable in the single-cycle filtration tests, the mixtures of AOM and humic substances resulted in a reduction in reversible membrane fouling and a marked increase in irreversible fouling compared with AOM alone

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Summary

Introduction

Ceramic membranes are used increasingly in water and wastewater treatment due to their inherent advantages over conventional polymeric membranes such as narrow and well-defined pore size distribution, high surface hydrophilicity, and good mechanical and chemical stability [1]. Membrane fouling due to the presence of naturally-occurring aquatic organic matter in source waters is a major challenge in the application/operation of both conventional polymeric and ceramic membranes [3,4]. Aquatic natural organic matter (NOM) is ubiquitous in natural water bodies, and can be classified as being of autochthonous and allochthonous origin [8]. Humic substances, such as humic (HA) and Membranes 2018, 8, 7; doi:10.3390/membranes8010007 www.mdpi.com/journal/membranes

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