Introduction: Bisphenols are released into wastewater during decomposition of plastic products, therefore effective wastewater treatment is the key to reducing bisphenol emissions into the environment. An alternative to conventional biological treatment plants are algae technologies, which support sustainable development and have the ability to remove various pollutants from wastewater. Purpose: We wanted to determine the effect of a bisphenol mixture on Chlorella vulgaris growth under autotrophic and mixotrophic conditions, as well as the efficiency of bisphenol removal by algae in monoculture and coculture with bacteria. We also wanted to increase algal biomass by establishing cocultures with bacteria and achieve greater efficiency of bisphenol removal from the aqueous medium. Methods: The experiments were conducted in laboratory algal bioreactors. The growth of microalgae was evaluated on the basis of changes in the concentration of chlorophyll a, which was extracted from algal cells. Bacteria were isolated from the activated sludge of the wastewater treatment plant Ajdovščina and the algal pond using the method of smearing the samples in a zig-zag pattern on solid agar. We established cocultures with different ratios of algal and bacterial cell counts. The analysis of the efficiency of bisphenol removal by gas chromatography–mass spectrometry was carried out for us by the Jožef Stefan Institute. A mixture of 17 bisphenols was used in the experiments, the concentration of each being 1 µg/L. Results: There was no statistically significant effect of bisphenols on chlorophyll a formation in microalgae cells. C. vulgaris did not achieve higher chlorophill a concentrations in coculture with bacteria comparing to monoculture. The growth rate of algae in cocultures was most likely influenced by glucose in the growth medium (mixotrophic metabolism) rather than the positive influence of bacteria. Statistically significant differences in bisphenol removal efficiency between different C. vulgaris cultivation methods were noticed in 9 bisphenols. Among these, microalgae were the most effective in monoculture under mixotrophic conditions. The efficiency of bisphenol removal by algae was more related to the logKow value of individual bisphenols than to the method of algal cultivation (i.e. monoculture, coculture, type of metabolism). Discussion and conclusion: The results show that bisphenols do not inhibit the growth of C. vulgaris at concentrations typical of municipal wastewater and that microalgae have the potential to remove bisphenols from the aqueous medium. This shows the relevance of this research, so it could be extended to applied research in the future.
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