Abstract
The low energy and investment separation of microalgae from water has become an important issue with the increasing interest for this biomass. The present work is a contribution to the assessment of flotation under vacuum using a vacuum gaslift in different conditions. The harvesting efficiency (HE) and the concentration factor (CF) of the vacuum gaslift increased from around 50 % when airflow rate was reduced from 20 to 10 L min -1 . Reduced bubble size also multiplied HE and CF 10 times either by the use of specific micro bubble diffusers or by an increase of water salinity from <1 ‰ to 40 ‰. HE and CF were slightly affected by the initial concentration of microalgae in the culture. The reduction of the harvest volume extracted in one hour from 100 to 1 L allowed increasing the CF from 10 to 130 but meanwhile decreasing HE from 56 to 8 %. An optimized vacuum gaslift could harvest microalgae below 0.2 kWh kg -1 DW which allowed reducing harvesting energetic costs from 10 to 100 times compare to classical processes. The vacuum gaslift appeared as an efficient and economic method to harvest microalgae and open interesting development perspectives in particularly for dewatering biomass cultivated in saline waters.