Microalgae filtration

The microalgae are cultured in bioreactors under solar or artiflcial light in the presence of carbon dioxide and salts. The bioreactors may be closed systems made of polyethylene sleeves rather than open pools. Optimal conditions for pigment production are low to medium light intensity and medium temperatures (20 to 30°C). Pigment extraction is achieved by cell breakage, extraction into water or buffered solution, and centrifugation to separate out the filtrate. The filtrate may then be partly purified and sterilized by microfiltration and spray dried or lyophilized. 

Filtration operated under pressure or vacuum is feasible for harvesting large microalgae (>70 pm) such as Coelastrum. To recover the smaller microalgae (<30 pm), membrane-based microfiltration and ultrafiltration may be applied, but they are more expensive. 

Similar to filtration, gravity sedimentation is also suitable for recovering the large microalgae. This method is usually considered as the first plan in algal wastewater treatment systems because of the large volumes treated and the low value of the biomass obtained. ... 

Vandanjon, L., Rossignol, N., Jaouen, P., Robert, J.M., and Quemeneiu, F. (1999) Effects of shear on two microalgae species. Contribution of pumps and valves in tangential flow filtration systems. Biotechnoi Bioeng., 63,1-9. 

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