StemRegenin 1 Concerning the effect of different factors on
Concerning the effect of different factors on biodegradation kinetics of the investigated compounds, except for CBTR that was biodegraded faster when StemRegenin 1 with higher SRT was used, no effect was observed for the other compounds (Fig. 1, Table 3: Experiments A, E), indicating that (a) microorganisms capable of degrading these compounds are present in both activated sludge systems, independently of the SRT used and (b) slow-growing bacteria were not playing a significant role on biodegradation of target compounds. These results indicate that biodegradation of these compounds can be expected in all nitrifying conventional and extended aeration activated sludge systems. Further experiments should be conducted at lower SRTs (<8 d) in order to investigate the existence of a critical SRT below which BTRs and OHBTH biodegradation might not occur. Comparison of Experiments A and B showed that the existence of anoxic conditions accelerated biodegradation of CBTR and OHBTH, while no significant difference was observed for the other compounds (Fig. 2, Table 3). No competitive substrate inhibition or catabolic repression of target compounds biodegradation was noticed in the experiments with easily degradable organic substrate (Experiments C, D). On the contrary, the addition of organic substrate resulted in decreased half-life values of BTR (under aerobic and anoxic conditions), CBTR (under aerobic conditions) and OHBTH (under aerobic conditions). It should be mentioned that this acceleration of target compounds biodegradation cannot be explained by the slight biomass increase in experiments with additional organic substrate, as for these compounds a similar trend was also observed in the TSS normalized biodegradation rate coefficients kbiokbio (Table 3). Based on the above, it seems that the increase of biomass in organic-substrate amended batch reactors consisted of bacteria that could also degrade the investigated compounds. Having in mind that (a) the low concentrations of micropollutants added in these experiments (μg L−1) cannot support an significant growth of specified degrading bacteria and (b) no lag phase was noticed in degradation experiments (Fig. 2); it therefore seems that biodegradation of target compounds occurs due to co-metabolic phenomena by microorganisms utilizing a wide range of carbon sources. The aerobic co-metabolic biotransformation of BTR due to hydroxylation of the aromatic benzene ring and methylation of the triazole ring was recently shown by Huntscha et al. (2014).