Microalgal biomass can be a potential source of proteins, carbohydrates, and lipids, and has received substantial attention in research for bioenergy production. The key steps for production of biofuel from microalgae are cultivation under optimum conditions for high biomass productivity and recovery of the generated biomass. Harvesting of microalgal cells from extremely dilute medium makes recovery technically difficult, contributing to 20-30% of the total biomass production cost; it is therefore a critical factor in the feasibility of large-scale process. A novel method for harvesting microalgal biomass using acid mine drainage (AMD) as flocculant was devised and studied. Two doses (5 and 10%) of AMD (a natural sources of metal ions) were applied to 0.5 and 1.0 g/L of two different microalgal strains Scenedesmus obliquus and Chlorella vulgaris at pH 7 and 9. High concentration of metal ions in AMD enhanced the coagulation/flocculation of microalgal biomass. Most of the microalgal biomass recovery occurred within 10 and 20 min for S. obliquus and C. vulgaris, respectively. For both microalgae, 10% dose of AMD showed higher flocculation efficiency than 5% dose at both cell density (0.5 and 1.0 g/L) in all tested conditions. The highest flocculation efficiency at pH 9 for S. obliquus and C. vulgaris was 85 and 92%, respectively. Microscopic examination indicated that the microalgal floc was well-formed and compressed. The present investigation demonstrated that AMD could be a valuable candidate for recovery of microalgal biomass making the harvesting process cost effective.

Acid mine drainage: A novel flocculant for the recovery of microalgal biomass

248th National Meeting (2014)

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