Methods coagulation/flocculation and flocculation with ballast agent for effective harvesting of microalgae

The effects of coagulant (FeCl3·6H2O), various flocculants based on polyacrylamide (PAA), polyethylenoxide (PEO) and flocculated biomass as ballast agent, dosage and sedimental time on flocculation efficiency of harvesting Chlorella vulgaris GKV1 cultivated in a laboratory were investigated. The results of this work indicated that the flocculation efficiency achieved about 90% after 5 min of sedimentation when adding of coagulant and flocculant mixture (FeCl3 50 mg/l + PEO based Sibfloc-718 7.5 mg/l) or flocculant with ballast agent (Sibfloc-718 7.5 mg/l + 10% flocculated biomass). PAA and PEO showed good flocculation efficiency at dosage of 0.025 and 0.015 g/l, respectively without pH adjustment. Finally, the most suitable flocculation method was discussed in this paper.