Study of Parameters Effective on Flocculation of Chlorella sp. Microalgae with Alum

Microalgae that can grow in seawater are considered as a source for biodiesel. Still, the low concentration and small size of microalgae cells are the main challenges in separation of biomass for biodiesel production. Among different commercial techniques for separation and dewatering, flocculation is considered the most efficient one. In this study, a full factorial design was used for studying the effect of cell concentration, pH and flocculant dosage on efficiency of Chlorella sp. flocculation with alum. The results have shown that flocculant dosage and interaction between pH and flocculant dosage are the most effective parameters in this regard. It was observed that the highest amount of flocculation efficiency per unit of coagulant consumed (7.05 g of DW cell per g of Alum) was obtained at cell density of OD550=3, pH=6, and coagulant amount of 200 mg L-1. Increase in pH amount led to increase in consumption of flocculant and increase in cell concertation led to decrease in flocculant consumption.