The effectiveness of bisulfite-activated permanganate technology to enhance the coagulation efficiency of Microcystis aeruginosa

The effects of bisulfite-activated permanganate technology (PM/BS) as a pre-oxidation process on enhancing Microcystis aeruginosa (M. aeruginosa) removal by post coagulation were investigated. The results demonstrated that pretreatment with PM/BS process effectively promoted the algae removal by coagulation with Al₂(SO₄)₃ as the coagulant and this phenomenon was more obvious with the increase of water hardness. Compared to the sole coagulation, PM/BS pre-oxidation combing with coagulation could neutralize the zeta potential of algal cells effectively, decrease the algal cell size, and lead to the formation of more compact flocs due to the in-situ generated MnO₂. The effect of oxidant dosages on algal organic matter (AOM) was also studied and no obvious release of macromolecular substances was observed with the dosage of KMnO₄ increasing from 3.0 mg/L to 7.0 mg/L, suggesting the integrity of algal cells at a high KMnO₄ dosage. Moreover, PM/BS pre-oxidation could lead to the decrease of most analyzed disinfection by-products (DBPs) at a Al₂(SO₄)₃ dosage of 40.0 mg/L. The algae removal efficiency was also significantly enhanced by PM/BS pre-oxidation in the test using real algae-laden water. This study indicated that PM/BS process might be a potential assistant technology for algae removal by subsequent coagulation.