Biorremediação com microalgas acoplada ao tratamento terciário para efluentes contendo antibióticos

Abstract

The increase in the use of antibiotics and their inadequate disposal are responsible for increasing the process of bacterial resistance in aquatic environments. Current sewage treatment plants (STP) were not designed to remove drugs that, in most cases, remain unchanged after passing through biological processes. Advanced oxidative processes, ozonation, ultraviolet lamp reactors and activated carbon adsorption are examples of technologies available for the removal of these pollutants, but they are expensive and often unsustainable, in addition to not being used by most STP. Microalgae culture offers an interesting option for the tertiary treatment of wastewater, as they have the ability to accumulate nutrients, remove emerging contaminants, in addition to producing potentially valuable biomass. This work aimed to evaluate the efficiency of removal of the antibiotics sulfamethoxazole (SMX) and trimethoprim (TMP), using bench-scale photobioreactors through the cultivation of the microalgae Monoraphidium contortum. Six different cultures were carried out in order to evaluate the maximum cell concentration reached (Xm), biomass productivity (Px), nitrogen consumption capacity and removal efficiency of the selected antibiotics. Four cultures were carried out in Bold medium (standard culture, with SMX, with TMP, and with SMX and TMP together) and two cultures in synthetic effluent (standard culture and with SMX), with pH and cell growth parameters daily monitored. Cultivation in synthetic effluent resulted in a lower Xm value, compared to cultivation in Bold medium, where there is a higher concentration of nutrients and, due to this insufficient growth in synthetic effluent, the removal assays were performed in Bold medium. The removals for the experiments carried out in Bold medium were equal to 42.3% (SMX), 28.6% (TMP) and, in simultaneous addition of antibiotics, 27.6% and 7.0% (TMP and SMX, respectively). For the run carried out in the synthetic effluent, there was no removal of sulfamethoxazole. Removals of more than 90% of the total nitrogen concentration were found for cultures carried out in Bold medium, with or without the presence of antibiotics. The evaluation of biomass revealed that the species M. contortum stands out as a promising option for obtaining lipids, which are suitable for the production of biodiesel. Therefore, the cultivation of microalgae in this study demonstrates potential for the bioremediation of effluents by reducing the concentration of micropollutants and nutrients in the cultivation medium, in addition to producing potentially valuable biomass. This strategy is interesting since the diversity of these microorganisms is abundant and their use is sustainable.