Fe2+ activating sodium percarbonate (SPC) to enhance removal of Microcystis aeruginosa and microcystins with pre-oxidation and in situ coagulation

Abstract

The frequent occurrence of cyanobacterial blooms has become a concern for drinking water safety. Common pre-oxidation, which was widely considered to enhance the followed coagulation, can cause the rupture of algae cell, leading to the undesirable release of intracellular organic matter. In this study, the Fe²⁺ activating sodium percarbonate (SPC/Fe²⁺) process for pre-oxidation and in situ coagulation was proved to effectively remove Microcystis aeruginosa without damaging cell integrity at optimal combined doses of SPC (0.2 mM) and Fe²⁺ (0.2 mM). Moreover, the SPC/Fe²⁺ process can not only control the release of MCs, but also reduce extracellular MCs from 5.22 μg/L to 1.50 μg/L, due to their moderate oxidation. Meanwhile, the SPC/Fe²⁺ treatment produces low levels of residual Fe after settling. During sludge ageing, owing to oxidation damage on cells arising from the SPC/Fe²⁺ treatment, cells continually suffered severe damage and lysed on day 4, leading to large release of intracellular organic matter and MCs, correspondingly. As a result, it is worth noting that the M. aeruginosa cells in stored sludge should be treated or disposed of early. These findings support the development of a green and cost-effective technology to handle cyanobacteria-containing water based on SPC/Fe²⁺ for ensuring water quality.

Keywords: Cell integrity; Microcystins; Microcystis aeruginosa; Sludge storage; Sodium percarbonate (SPC)/Fe(2+).