The effects of coagulant (FeCl36H2O), 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.