Microalgae concentration by foam fractionation

Abstract

A technique using foam fractionation has been investigated for concentrating marine microalgae Chaetoceros sp., a unicellular diatom, from mass cultures. Foam fractionation is a water treatment technology that is useful in removing dissolved and suspended solids from water. The removal of dissolved and suspended solids is accomplished by bubbling air, or some other gas, through water to concentrate the dissolved and suspended solids in a foam which is then removed from the water. The amount of biosurfactant, which was produced by microalgae, was found to be the major factor affecting microalgae removal by foam fractionation. A logarithmic relationship between biosurfactant activity in the microalgae culture and algae removal efficiency by foam fractionation was found. A two step microalgae harvesting technique was developed which used foam fractionation as the first step to concentrate microalgae from fairly diluted microalgae cultures into foam condensates and used centrifugation as the second step to produce a thick algae paste. The natural occurring biosurfactant was reused in this two step microalgae harvesting technique. More than fifty percent of microalgae removal efficiency was achieved during the experiments.