Removal processes and estrogenic activity of bisphenol—A and triclosan using microalgae

Abstract

This study aimed to evaluate the effect of microalgal photoautotrophic treatment on estrogenic activity (EA) and removal process of two emerging contaminants (ECs), bisphenol-A (BPA) and triclosan (TCS), in synthetic wastewater (SWW). The concentration used for BPA (17 mg/L) and TCS (325 μg/L) is the median effective concentration (EC₅₀). Two conditions were evaluated, using a microalgae inoculum of ≈300 and ≈500 mg TSS/L (Total Suspended Solids per liter). For BPA, biodegradation was found to be the removal process contributing to the highest percentage removal, reaching >40 % for both initial microalgae inoculum (≈300 and ≈500 mg TSS/L). For TCS, the highest removal process was photodegradation, with >28 % (sum of direct and indirect removal). However, for TCS it was observed that for TSS ≈ 500 mg/L TSS, sorption (adsorption and absorption) increased by ≈17 % with respect to that determined for TSS ≈ 300 mg/L. Microalgae photoautotrophic treatment, using ≈500 mg TSS/L, resulted in a reduction of EA for TCS (by 33 %); but a 1.13-fold increase of EA for BPA. No EA effect of BPA and TCS was observed at ≈300 mg TSS/L. Both treatments resulted in a removal of >95 % of BPA and ≈86 % of TCS. For direct photodegradation, removals of both BPA and TCS were quantified as 3.8 % and 14.4 %, respectively. However, an increase in EA was observed for both ECs (1.79-fold for BPA and 1.23-fold for TCS). Indirect photodegradation resulted in removals of 26.2 % and 14.1 %, respectively. Additionally, EA showed a 2.4-fold increase for BPA, whilst a 17.99 % decrease was observed for TCS. In conclusion, no linear correlation was observed between EA and EC removals. Microalgae photoautotrophic treatment resulted in high removal efficiencies of TCS and BPA, as well as a decreased EA of TCS.