3.2.2 Size distribution of microbubble and Microcystis
When the microbubbles adhere to Microcystis , the size distribution of microbubble-algae aggregates is shown in Fig.5. The particle size of microbubbles in the microbubble-algae complex was in the range of 10~170 μm, and the size ofMicrocystis was in the range of 10~400 μm. Among them, the proportion of microbubbles with a particle size of 70~125 μm is as high as 87%, and 85% ofMicrocystis are concentrated in 50~200 μm. In the size-frequency distribution curve of adhered Microcystis (Fig. 5(b)A), the peak frequency of Microcystis appeared at 100 μm (8.5%), that is, Microcystis in the range of 90~100 μm accounted for 8.5% of the totalMicrocystis . In the particle size distribution curve of microbubbles (total microbubbles) adhering to Microcystis (Fig. 5(b)B), the peak frequency of microbubble size appeared at 90 μm (12.0%), that is, microbubbles with particle size between 80~90 μm accounted for 12.0% of the total microbubbles. In the particle size distribution of microbubbles generated under this working condition (see Fig. 5(b)C), 45.8% of the microbubbles were distributed between 40 and 60 μm, and the proportion of microbubbles adhering to Microcystis (80~90 μm) was less than 1%. The frequency distribution peak of the particle size of the adhered microbubbles is like that of the microalgae. It was reported that morphology of algae including shape and size also have impacts on the performance of flotation process when considering the bubble-cell attachment, in addition, spherical (Microcystis ) and oval (Chlamydomonas ) configures had greater flotation efficiencies than filamentous shape (Phormidium ) (Bui et al., 2015).