In order to improve microalgal biomass recovery, coagulation–flocculation
was tested with two natural cationic flocculants, Ecotan and
Tanfloc. During the experimental period, microalgal biomass turbidity
varied from 277 to 573 NTU. However, for each jar test, the same biomass
(with the sameturbidity)was usedwith both flocculants. Biomass
recovery ranged from 91.8 to 99.4% and from 51.6 to 93.3% with Ecotan
and Tanfloc, respectively (Table 2). The optimal dose (boldfaced in
Table 2) was based on the lowest concentration of flocculant ensuring
over 90% biomass recovery. Regarding Ecotan, 91.8% of microalgal biomasswas
removed with a concentration of 10mg/L. In contrast, a higher
Tanfloc concentration (50 mg/L) obtained a similar efficiency 90.2%.
Note that flocculation efficiency depends on biomass concentration
[25], for this reason tests with both flocculants were carried out using
the same microalgal biomass concentration (2.8 g TS/L corresponding
to 0.8 g VS/L). Although validation under full-scale conditions is needed,
this study underlines the high biomass recovery potential of both flocculants
(N90%). Upon full-scale validation, an optimal dose adjustment
would be needed. Indeed, doses lower than 10 mg/L may be sufficient
due to the successful results obtained with a flocculant dose of
10 mg/L in this study