BACKGROUND: Predatory flagellates and ciliates are two common bio-contaminants which frequently cause biomass losses in Chlorella mass culture. Efficient and targeted ways are required to control these contaminations in Chlorella mass cultivation aiming for biofuel production especially.

RESULTS: Five surfactants were tested for its ability to control bio-contaminations in Chlorella culture. All fve surfactants were able to eliminate the contaminants at a proper concentration. Particularly the minimal efective concentrations of sodium dodecyl benzene sulfonate (SDBS) to completely eliminate Poterioochromonas sp. and Hemiurosomoida sp. were 8 and 10 mg L？1 , respectively, yet the photosynthesis and viability of Chlorella was not signifcantly afected. These results were further validated in Chlorella mass cultures in 5, 20, and 200 m2 raceway ponds.

CONCLUSIONS: A chemical method using 10 mg L？1 SDBS as pesticide to control predatory fagellate or ciliate contamination in Chlorella mass culture was proposed. The method helps for a sustained microalgae biomass production and utilization, especially for biofuel production.