Microalgae growth with a high concentration of emerging pollutants and phytotoxicity evaluation of cultivation wastewater

This work aimed to evaluate the influence of different mixtures of emerging pollutants (EPs) (paracetamol, acetylsalicylic acid, caffeine, fluoxetine and diazepam) in the growth of Scenedesmus obliquus, Chlorella homo-sphaera and Spirulina platensis. The cells growth test was carried out for 20 days, and the mixture of EPs was incorporated in the specific medium for each microalgae. Phytotoxicity tests were performed based on the germination index of lettuce and cucumber seeds using the wastewater from microalgae cultures (S. obliquus and S. platensis) without biomass. S. obliquus was able to grow in all mixtures of EPs. On the other hand, S. platensis presented cell death in EPs mixtures containing paracetamol. Both seeds germinated in S. obliquus supernatant with a germination index (GI) of 42.07% when acetylsalicylic acid and caffeine were added. In the absence of EPs, GI was 61.49%. The supernatant from S. platensis presented toxicological effects on seeds germination, with no germination for lettuce seeds. On cucumber seeds, the supernatant of S. platensis cultivated without EPs or acetylsalicylic acid and caffeine showed a GI of 7.13% and 4.27%, respectively, showing a negative effect of the culture medium of Spirulina on this parameter. Therefore, it is possible to use microalgae to EPs bioremediation and use the supernatant to further applications if the correct microalgae strain is chosen. S. obliquus showed the ability to grow when EPs were incorporated into the medium, besides reducing the phytotoxicological effects of the supernatant on the germination of seeds.