Performance of different flocculants for harvesting Chlorella vulgaris by dissolved air flotation and sedimentation

This study systematically evaluated the performance of dissolved air flotation and sedimentation for harvesting Chlorella vulgaris using eight different flocculants. Significant variation was observed in both the maximum harvesting efficiency and the minimum effective flocculant dose across different flocculant-process combinations. Among the tested flocculants, pyridinium modified cellulose nanocrystals achieved the highest harvesting efficiency of 99 % in both dissolved air flotation and sedimentation, while chitosan required the lowest minimum flocculant dose (∼2 mg·g⁻¹) to induce flocculation. The impact of floc size formed during the flocculation step on harvesting performance was also investigated, revealing that large flocs significantly favored sedimentation-based microalgae harvesting. A preliminary cost analysis highlighted the importance of integrating economic considerations into the selection of both flocculant and harvesting method. The findings suggest that optimal flocculant and process selection should be based not only on harvesting efficiency but also on cost-effectiveness for microalgal biomass recovery.