Microalgae harvesting by flotation using natural saponin and chitosan

•Biosurfactant (saponin) and chitosan were used in microalgae harvesting.•Very effective separation for microalgae cells, polysaccharide, and protein.•The process can be applied in the integrated microalgae-based biorefinery. This study aims to investigate the harvesting of microalgae by dispersed air flotation (DiAF) using natural biosurfactant saponin as the collector and chitosan as the flocculant. Two types of microalgae, Chlorella vulgaris and Scenedesmus obliquus, were used in this study. It was observed that saponin was a good frother, but not an effective collector when used alone for flotation separation of algae. However, with the pre-flocculation of 5mg/L of chitosan, separation efficiency of >93% microalgae cells was found at 20mg/L of saponin. Removal efficiency of >54.4% and >73.0% was found for polysaccharide and protein, respectively at 20mg/L of saponin and chitosan each. Experimental results show that DiAF using saponin and chitosan is effective for separation of microalgae, and algogenic organic matter (AOM). It can potentially be applied in the integrated microalgae-based biorefinery.