Résumé
The flocculation efficiency of microalgae Chlorella vulgaris for subsequent harvesting wasinvestigated using single flocculants of inorganic salts, synthetic polymer, chitosan anddual flocculants of inorganic salts and chitosan. Synthetic polymer (FlopamTM) couldachieve over 90% optical density removal (OD680removal) at a low flocculant dose (20to 40 mg polymer per litre of algal suspension) through the bridging mechanism andcharge neutralisation. Inorganic salts (i.e. ferric chloride and aluminium sulphate) andchitosan individually resulted in low flocculation efficiency (<90%) despite high dose(i.e. 160 to 200 mg per litre of algal suspension). The dual flocculation combiningferric chloride or aluminium sulphate with chitosan induced synergistic effects, resultingin >80% flocculation efficiency, significantly higher than the sum of each individualflocculation. The improvement in flocculation efficiency was 57 and 24% respectivelyfor ferric chloride/chitosan and aluminium sulphate/chitosan. Charge neutralisation ofmicroalgal cells by ferric chloride or aluminium sulphate combined with bridging bychitosan produced the synergy.