## 3 Results and Discussions
### EDC Removal
When analysing E removal, similar degradation values to those obtained for BPA (by 20%) were observed under abiotic conditions (O and LO experiments) during the first three days, as depicted in Figure 3f. However, abiotic degradation became more significant from day 4 to 7. As shown in Figure S1 (Supplementary Material), light was not a substantial factor in E removal. BP and E were the only compounds that exhibited abiotic degradation, so the potential synergistic effects between these pollutants were studied. For this purpose, the LO experiments were conducted without BP or E, keeping the operating conditions and the rest of the ECDs. The results indicated that E did not undergo abiotic degradation under the LO conditions without BP (Supplementary Material, Figure S2b). However, BP exhibited a similar degradation trend in the culture media with or without E, with the degradation rate being even higher in the presence of E at day 7 (95% compared to 60%, respectively) (Supplementary Material, Figure S2a). These findings suggest a positive synergistic effect on the degradation of BP and E when both compounds are present in the mixture. On the other hand, when _C. vulgaris_ was included, a dramatic increase in removal efficiency was observed from day 4 to day 7, achieving a reduction in E of 83% within 7 days (Figure 3f). Conversely, the presence of _Scenedesmus_ sp. did not increase the percentage of E removed (70% in 7 days) compared to the O experiments (63%), although it was higher than in the LO experiments (40%). During their growth, microalgae produce algal extracellular organic matter (AEOM) primarily consisting of biopolymers such as polysaccharides and proteinaceous substances. AEOM plays a significant role in promoting the photochemical generation of short-lived radicals, including excited triplet-state dissolved organic matter (\({}^{\text{(}}\)DOM\({}^{\text{\text{\textregistered}}}\)), singlet oxygen (\({}^{\text{(}}\)O\({}_{2}\)), and hydroxyl radicals (-OH). These radicals contribute to the degradation of pollutants such as E [81]. Studies have indicated that _C. vulgaris_ produces more AEOM than _Scenedesmus quadrica_, potentially enhancing the photocatalytic degradation of E [82]. Notably, the high removal efficiencies of E achieved by _C. vulgaris_ between days 4 and 7 (Figure 3f) align with its exponential growth phase observed in Figure 1a. This phase is characterised by rapid metabolic activity and increased AEOM release [81]. The differences in AEOM release could explain the variation in the final E removal between _C. vulgaris_ and _Scenedesmus_ sp. These removal results are aligned with previous research. For instance, a 79% reduction in E concentration was reported using _Haematococcus pluvialis, Selenestrum capricornutum_, and _Scenedesmus quadrica_ individually over 10 days [83]. Additionally, an overall E removal of 91% with _S. obliquus_ and 52% with _C. vulgaris_ in 5 days was demonstrated [84]. In that same study, _Scenedesmus_ achieved a higher removal efficiency compared to _C. vulgaris_, which contrasts our findings. This dis crepancy could be attributed to differences in cultivation methods and in the composition of the synthetic wastewater used. For instance, this other study employed a continuous cultivation mode, where reactors were fed daily, providing a more stable environment and consistent nutrient supply, potentially enhancing the performance of _Scenedesmus_ over _C. vulgaris._  
Finally, the final removal percentages obtained for both microalgae after 7 days are presented in Table 1 and compared with the previous literature. As explained previously, comparing these results with others reported in the literature is difficult due to the considerable influence of culture conditions, such as the presence of aeration and the composition of the culture media. Regarding parabens, complete removal was achieved for both microalgae. These removal percentages are within the range described by other authors.