Comparison and optimization of different methods for Microcystis aeruginosa’s harvesting and the role of zeta potential on its efficiency

This study has compared the harvesting efficiency of four flocculation methods, namely, induced by pH, FeCl3, AlCl3 and chitosan. No changes were observed on M. aeruginosa cells. Flocculation assays performed at pH 3 and 4 have shown the best harvesting efficiency among the pH-induced tests, reaching values above 90% after 8 h. The adjustment of zeta potential (ZP) to values comprised between − 6.7 and − 20.7 mV enhanced significantly the settling rates using flocculant agents, being FeCl3 the best example where increments up to 88% of harvesting efficiency were obtained. Although all the four methods tested have presented harvesting efficiencies above 91% within the first 8 h after the optimization process, the highest performance was obtained using 3.75 mg L−1 of FeCl3, which allowed reaching 92% in 4 h.