Cyanobacterium removal and control of algal organic matter (AOM) release by UV/H₂O₂ pre-oxidation enhanced Fe(II)...

Harmful algal blooms in source water are a worldwide issue for drinking water production and safety. UV/H₂O₂, a pre-oxidation process, was firstly applied to enhance Fe(II) coagulation for the removal of Microcystis aeruginosa [M. aeruginosa, 2.0 (±0.5) × 10⁶ cell/mL] in bench scale. It significantly improved both algae cells removal and algal organic matter (AOM) control, compared with UV irradiation alone (254 nm UVC, 5.4 mJ/cm²). About 94.7% of algae cells were removed after 5 min UV/H₂O₂ pre-treatment with H₂O₂ dose 375 μmol/L, FeSO₄ coagulation (dose 125 μmol/L). It was also certified that low residue Fe level and AOM control was simultaneously achieved due to low dose of Fe(II) to settle down the cells as well as the AOM. The result of L₉(3)⁴ orthogonal experiment demonstrated that H₂O₂ and FeSO₄ dose was significantly influenced the algae removal. UV/H₂O₂ induced an increase of intracellular reactive oxidant species (ROS) and a decrease in zeta potential, which might contribute to the algae removal. The total microcystins (MCs) concentration was 1.5 μg/L after UV/H₂O₂ pre-oxidation, however, it could be removed simultaneously with the algae cells and AOM. This study suggested a novel application of UV/H₂O₂-Fe(II) process to promote algae removal and simultaneously control AOM release in source waters, which is a green and promising technology without secondary pollution.