Effect of feedwater pre-treatment using UV/H2O2 for mitigating the fouling of a ceramic MF membrane caused by soluble algal organic matter

Soluble algal organic matter (AOM) resulting from cyanobacterial blooms can cause severe fouling for water treatment membranes as it contains a large proportion of high molecular weight (MW) organics such as biopolymers and humic-like substances. UV/H2O2 advanced oxidation of feedwater containing AOM derived from Microcystis aeruginosa was investigated as a means of mitigating the fouling of a ceramic microfiltration (MF) membrane and degrading the algal toxin microcystin-LR. The result was compared with the pre-treatment using coagulation with ACH. UV/H2O2 treatment and coagulation achieved a marked and comparable reduction in total fouling resistance, however coagulation led to considerably lower irreversible fouling. The significant reduction in membrane fouling by the pre-treatments was attributed to the effective breakdown/removal of the very high MW biopolymers (≥20,000Da) and high MW organic substances (~10,000Da) in the AOM. UV/H2O2 treatment resulted in the generation of lower MW substances due to partial oxidation of the large molecules, and consequently greater irreversible membrane fouling compared with coagulation. Microcystin-LR was completely inactivated by UV/H2O2, whereas coagulation was ineffective for removing it.