A sustainable approach by using microalgae to minimize the eutrophication process of Mar Menor lagoon

Highlights: • Bioremediation of sewage by autochthonous mixotrophic consortia grown in photobioreactors. • The four mixotrophic consortia decreased the contaminant burden of the El Albujón wastewater. • Consortium 1 was effective for removing emerging contaminants (100%, with 78.50% for adenosine). • Consortium 1 significantly removed nitrates (89.90%) and phosphates (99.70%). • The contents of carbohydrates, lipids and proteins from the biomass of consortium 1 were 30.51%, 28.09% and 13.59%, respectively. The present study evaluates the removal capacity of microalgae photobioreactors of environmental pollutants present in wastewater from the dry riverbed El Albujón, as a way to minimize the eutrophication process of the Mar Menor. Particularly, the capacity of four autochthonous microalgae consortia collected from different locations of the salty lagoon to remove emerging contaminants (simazine, atrazine, terbuthylazine, adenosine and ibuprofen), nitrates, and phosphates, was evaluated. Among the four microalgae consortia, consortium 1 was the best in terms of biomass productivity (0.11 g L⁻¹ d⁻¹) and specific growth rate (0.14 d⁻¹), providing 100% removal of emerging contaminants (simazine, atrazine, terbuthylazine, adenosine and ibuprofen), and a maximal reduction and consumption of macronutrients, especially nitrates and phosphates, reaching levels below 28 mg L⁻¹, that is, a decrease of 89.90 and 99.70% of nitrates and phosphates, respectively. Therefore, this consortium (Monoraphidium sp., Desmodesmus subspicatus, Nannochloris sp.) could be selected as a green filter for successful large-scale applications. This study is the first one that combines the successful removal of herbicides, ibuprofen and adenosine as emerging contaminants, and nitrate removal.