Removal of Microcystis aeruginosa and its extracellular organic matters by using covalently bonded coagulant: An alternative choice in enhanced coagulation for algae-polluted water treatment

High coagulants dosage, Al or Fe residual, unstable flocs, and extracellular organic materials (EOM) released from cells cannot be avoided by using traditional Al or Fe based coagulants in algae removal. Thus, a novel covalently bonded coagulant poly aluminum ferrous chloride/cationic polyacrylamide (CAFM) was developed. The algae and EOM removal performance and mechanisms were investigated in current research. Al and Fe residual, cell integrity, and compactness of flocs were analyzed after coagulation. Furthermore, the disinfection by-products formation potential (DBPFP) and economics was also figured out to confirm the advantage of using CAFM. Results showed that 95.01% of turbidity and 99.3% of OD686 were effectively removed by using CAFM at 6 mg/L. Moreover, lower breakage probability of algae cells and denser flocs were realized by using CAFM compared to common used Al or Fe coagulants. In addition, lower Al and Fe residual and lower DBPFP were confimed in CAFM coagulation. DFT (Density functional theory) and ESP (Electrostatic Potential) results showed CAFM could combine bEOM (bonded extracellular organic matter) and dEOM (dissolved extracellular organic matter) through H-bond from Al atom in the covalent bond. Due to the introduction of various functional groups of different coagulants, charge neutralization and adsorption ability contributed to treating algae-containing water.