Removal of metronidazole from aqueous media by C. vulgaris

Schematic diagram of MDZ removal in Chlorella vulgaris culture. [Display omitted] •Metronidazole is efficiently removed during algal treatment.•Metronidazole is removed via sorption onto the biomass.•Metronidazole showed toxicity to C. vulgaris at stationary phase of life cycle.•The removal efficiency of C. vulgaris decreased with increase of antibiotic. This current study investigated the removal of metronidazole from aqueous media by C. vulgaris. Two different initial sizes of inoculum (0.05 and 0.5 g L−1) were tested for a wide concentration range of metronidazole (1–50 μM). The effect of metronidazole concentrations on biomass production was studied for 20 days. The exopolymeric substances (EPS) were quantified and correlated with the removal of antibiotics from aqueous media. Specifically, MDZ stimulated the production of EPS in C. vulgaris, which played the major role in the adsorption of this antibiotic. Also, metronidazole significantly influenced the zeta potential of C. vulgaris in the test cultures, indicating a change in surface characteristics. This decrease in surface negative charge caused auto-flocculation phenomena at a stationary phase. Chronic and acute toxicity experiments showed that metronidazole was harmful to C. vulgaris at stationary phase. Results from this study would advance our knowledge on the treatment of metronidazole-contaminated waters with C. vulgaris as a green technology-oriented process.