Mechanistic insight into peracetic acid-enhanced coagulation for algae-laden water treatment

In this study, the mechanism of enhanced coagulation was elucidated by oxidizing various components of the algae-laden water with a moderate oxidant, peroxyacetic acid (PAA), based on the optimization of the contents and species of coagulants and oxidants. It was shown that the combination of PAA (10 mg/L) and polymeric aluminosilicate iron (PSAF) (12 mg/L) was the optimal strategy for the treatment of algae-laden water due to its high removal rate of algae and the generation of larger flocs. Moreover, the synergistic and individual oxidation test of algae-laden water proved the moderate oxidation mechanism of PAA to enhance coagulation and algae removal through two pathways: the degradation of dissolved extracellular organic matter (dEOM) and the shedding of bound extracellular organic matter (bEOM) from the algae surface, which led to the aggregation and sedimentation of algae cells. Algae cells did not cause visible rupture and intracellular organic matter release in the presence of PAA and were not considered to be an unfavorable factor for PAA-enhanced coagulation treatment. In general, PAA enhanced the zeta potential of the algae-laden water, degraded humic acids, polysaccharides, proteins, and other organic matter, thus easier to remove the algae cells and pollutants through the coagulation process. This study provides a new insight for the mechanism of oxidation-enhanced coagulation technology.