3.3 Effects of the microbubble flotation parameters on
microalgae harvest performance
The performance of microbubble air flotation on Microcystisharvesting under different working conditions is shown in Fig.7(A). The
concentration of Chla was 844 mg/m3 before air
flotation, and the concentration of Chla decreased significantly after
microbubble air flotation. Among them, the lowest Chla concentration
after flotation in condition 5 was 308 mg/ m3, and the
highest Chla concentration after flotation in condition 1 was 532
mg/m3. The recovery rate of Microcystis by
microbubble air flotation under different working conditions was sorted
from high to low as follows: working condition 5 (63.5%) >
working condition 4 (52%) > working condition 2 (50%)
> working condition 3 (41%) > working
condition 1 (37%). According to the content of 3.2.1, the distribution
peak of Microcystis is 90~100 μm, and the
adhesion rate is the largest when the particle size of microbubbles is
equal to the size of Microcystis . The proportion of bubbles with
a particle size greater than 80 μm produced by condition 5 is the
largest, and its algae harvesting efficiency is the highest. The
proportion of bubbles with a particle size of more than 80 μm produced
by condition 1 is the smallest, and its algae collection rate is the
lowest. The proportion of bubbles with a particle size of more than 80
μm produced by condition 3 is greater than that of condition 2, but its
algae collection efficiency is 9% lower than that of condition 2, which
may be caused by the floating of multiple large bubbles observed during
the experiment. Because the fast-floating speed of large bubbles
disturbed the adhesion of microbubbles to the algae, or caused the
desorption of the microbubble-microcystin aggregates that have adhered,
thereby reducing the algae collection rate. In the process of harvesting
algae by microbubble air flotation, the rate of algae harvesting depends
not only on the adhesion of microbubbles to algae, but also on the
influence of water flow environment.