Understanding the fouling of a ceramic microfiltration membrane caused by algal organic matter released from Microcystis aeruginosa

• Role of AOM components in the fouling of a ceramic MF membrane was investigated.
• Majority of the severe flux decline was attributed to membrane outer fouling layer.
• The outer layer was formed primarily due to very high MW hydrophobic compounds.
• The outer layer could be removed easily by using tangential flow flush.
• Irreversible fouling layer was dominated by high and low MW hydrophilic compounds.

Algal organic matter (AOM) released from Microcystis aeruginosa has high potential to cause fouling of water treatment membranes. The role of AOM components in the fouling of a commercial tubular ceramic microfiltration (MF) membrane (ZrO2–TiO2, 0.1 µm) was investigated. The organic matter extracted from the three operationally-defined fouling layers (i.e., outer, middle and inner layer detached from the membrane using cross-flow flush, backwash and chemical cleaning, respectively) was characterised to gain an understanding of the fouling mechanism. The majority of the flux decline in the MF of the AOM solution was attributed to the large amount of organic matter (51% of total DOC of feed, primarily very high molecular weight (MW) hydrophobic molecules) deposited on the ceramic membrane surface to form a thick and dense outer layer. The middle layer contained a very small amount of organics (3%), mainly very high MW hydrophilic molecules, and contributed very little to the flux decline. The inner layer (22% of total DOC), which was responsible for the hydraulically irreversible fouling, was dominated by the high and low MW hydrophilic compounds. These molecules reached the membrane inner pores due to their hydrophilic nature, leading to pore restriction by adsorptive fouling.