Iron-Based Technology Coupling Moderate Preoxidation with Hybrid Coagulation for Highly Effective Removal and Moderate Growth Inhibition of Oscillatoria in Drinking Water Treatment Plants

A novel technology coupling moderate preoxidation and hybrid coagulation was invented to solve the issues caused by Oscillatoria in drinking water treatment plants (DWTPs). In this technology K2FeO4 can reduce the electronic repulsion between Oscillatoria filaments without cells’ lysis and thereby make them tend to aggregate into flocs. After preoxidation in-situ Fe(III) reduced from Fe(VI) will form a highly efficient hybrid coagulant through addition of a low dose of chitosan quaternary ammonium salt (HTCC). This process can remove most of the algal cells and metabolites in Oscillatoria-laden water and alleviate filter blockages. After treatment, 93.0% of algal cells can be removed and the DOC, turbidity and CYN can be respectively decreased from 15.3 mg/L to 5.8 mg/L, from 5.76 NTU to 1.48 NTU, and from 22 mg/L to 4.55 mg/L. During sludge storage, the effects of the moderate oxidation of Fe(VI) and the anti-algal activity of HTCC can consistently control the proliferation of Oscillatoria and the increase of algal metabolites, thereby reducing the difficulty of sludge treatment and making the reuse of sludge water more feasible. In a nutshell, the new technology is suitable for DWTPs when Oscillatoria blooms break out in source water.