Efficient flocculation of microalgae for biomass production using cationic starch

In order to make algal biomass a suitable feedstock for fuel and bioproducts, a practical means of dewatering and concentrating the algal cells must be devised. An effective algal dewatering scheme will most likely utilize flocculation as an initial concentrating step. Cationic starch could prove to be an effective flocculant for economical production of uncontaminated microalgal biomass. This investigation seeks to ascertain whether or not cationic starch is an effective flocculant for the freshwater green alga Scenedesmus dimorphus. Evidence from extensive flocculation tests showed cationic starch to be effective at low dosages, approximately 0.08 g cationic starch to g algal biomass, for both growth phase and stationary phase S. dimorphus. Algal cell restabilization occurred at lower starch concentrations in the growth phase than in the stationary phase. The tests also indicated that flocculation was effective with degrees of cationic substitution from 0.14 to 0.64 with no significant change in flocculation efficiency over that range.