Effect of cultivation conditions on β-estradiol removal in laboratory and pilot-plant photobioreactors by an algal-bacterial consortium treating urban wastewater

The use of microalgal consortia for urban wastewater treatment is an increasing trend, as it allows simultaneous nutrient removal and biomass production. Emerging contaminants proposed for the list of priority substances such as the hormone 17β-estradiol are commonly found in urban wastewater, and their removal using algal monocultures has been accomplished. Due to the inherent potential of algae-based systems, this study aimed to assess the capability of native photobioreactor biomass to remove 17β-estradiol under indoor and outdoor conditions. At the same time, the microbial community changes in regular and bioaugmented operations with Scenedesmus were assessed. The results show that almost complete removal (>93.75%) of the hormone 17β-estradiol can be attained in the system under favourable seasonal conditions, although these conditions greatly influence biomass concentrations and microbial diversity. Even under the harsh conditions of low temperatures and solar irradiation, the established consortium removed more than 50% of the pollutant in 24 h. While species from genus Chlorella were stable during the entire operation, the microbial diversity analysis revealed that assorted and evenly distributed populations stimulate the removal rates. Bioaugmentation assays proved that the input of additional biomass results in higher overall removal and decreases the yield per mg of biomass