The potential of native microalgae consortia to remove pharmaceutical compounds present in treated wastewater

Wastewater treatment plants play a key role in the release of pharmaceuticals and other contaminants into the aquatic environment, causing negative effects on the ecosystems of receiving water bodies. This work aimed to assess the removal efficiency of real loads of these contaminants by wastewater-native microalgae consortia acting on treated wastewater previously subjected to secondary treatment. Wastewater sampling and removal efficiency experiments were conducted over 1 year at three different sampling points. Nineteen pharmaceutical compounds of different drug classes (stimulants, anticonvulsants, antidepressants, antibiotics, β-blockers, lipid regulators, and nonsteroidal anti-inflammatory drugs/analgesics), as well as one herbicide/algicide (Diuron) were detected and quantified. Native blooming microalgae consortia were grown in treated wastewaters, and their potential to remove these compounds was quantified. The removal efficiency of these compounds by native microalgae consortia was variable, ranging from almost no removal for Clofibric acid or Ketoprofen to near complete removal for Fluoxetine, Venlafaxine, Atenolol or Diuron. These variations were influenced not only by the molecular nature of the compounds but also by the microbial composition variability of the microalgae consortia, especially among the prokaryotes present. Overall, microalgae consortia successfully removed between 40 % and 83 % of the total detected compounds, preventing a significant part of these from entering the aquatic environment, contributing to enhance treated wastewater quality. Significant biomass growth was observed, reaching dry-weight concentrations up to 2.6 g.L^-1, indicative of good capacity of the grown consortia to deal with the toxicity effects of the pollutants. In addition to what is now reported, microalgae treatment also removes other pollutants, such as nutrients, metals or microplastic particles, constituting a versatile tertiary treatment for polishing treated wastewaters. These findings demonstrate the potential of native microalgae consortia-based systems to improve wastewater treatment processes, mitigating the environmental impact of pharmaceutical compounds while producing potentially useful biomass.