Ethidium Bromide (EtBr) is an organic compound used in molecular biology investigations. EtBr ability of intercalating in the DNA molecule makes it a toxic substance. The objective was to evaluate the phycoremediation potentials of Chlorella vulgaris, Desmodesmus subspicatus and Raphidocelis subcapitata tested separately and in a mixture (Mix) for EtBr removal from the aqueous medium. Experiments were conducted using an initial algae biomass of 106 cell/mL, exposed to 500 µg/L of EtBr. The removal efficiency (µg EtBr L-1) after 3 h in each treatment were: Mix (72.8 µg.L-1) >D. subspicatus (48.4 µg.L-1) >R. subcapitata (24.6 µg.L-1) >C. vulgaris (19.9 µg.L-1). However, when EtBr mass reduction per microalgae density is considered (ng.algae-1), the efficiency ranking changes to: D. subspicatus (1.9 × 10-5 ng.algae-1) >C. vulgaris (1.4 × 10-5 ng.algae-1) >Mix (9.8 × 10-6 ng.algae-1) >R. subcapitata (2.8 × 10-6 ng.algae-1). The results suggest that initial algal population density is a determinant factor for efficient EtBr removal by microalgae species in short term treatments. In order to obtain 100% of EtBr removal, it should be necessary 1010, 1010 and 1011 algae.mL-1 of C. vulgaris, D. subspicatus and R. subcapitata, respectively. The results strongly suggest phycoremediation can be explored as an alternative method for EtBr removal.
Keywords: Algal biomass; ethidium bromide; laboratory effluent; microalgae density; phycoremediation; tertiary effluent treatment.