Impact of perfluorooctanoic acid on treatment wastewater by a tandem AnSBR-ASBR system: Performance, microbial community and metabolism pathway

Insights into the Responses of the Partial Denitrification Process to Elevated Perfluorooctanoic Acid Stress: Performance, EPS Characteristic and Microbial Community

“…This result indicated a substantial increase in tryptophan protein-like, humic acid-like, and aromatic protein II-like substances, confirming the increase in PN content in EPS. This was also consistent in a previous study showing that the production of tryptophan protein-like, humic acid-like [27,42], and aromatic protein II-like [43] substances were promoted under PFOA stress. Moreover, under long-term PFOA stress, all three peaks eventually showed a blue shift.…”

“…The above results suggested that PFOA played a crucial role in shaping PD sludge microbial compositions, and the effect of PFOA on community compositions was concentration-dependent. This was in agreement with previous studies that showed PFOA induced significant changes in microbial communities after long-term exposure [27,34]. The microbial community structure at the phylum level under different PFOA concentrations is shown in Figure 6a.…”

“…This was in line with a previous report [37], which showed that a high removal efficiency of PFOA was achieved initially due to the adsorption of the sludge, while the PFOA removal efficiency gradually decreased with extended experimentation. Additionally, our results indicated that the main PFOA removal pathway was biosorption, which was also supported by previous studies demonstrating that PFOA removal in wastewater treatment systems mainly depend on the adsorption of activated sludge [22,27]. In phase VII with 20 mg/L PFOA addition, the effluent PFOA concentrations were higher than those of the influent, which was probably due to the desorption of PFOA from the sludge.…”

“…Intriguingly, high PFOA concentrations (2-20 mg/L) showed a slight effect on NTR (Table S1). Similarly, Yu et al [34] and Cao et al [27] demonstrated that <20 mg/L PFOA showed minor influence on both nitrification and denitrification, which indicated a safe PFOA exposure concentration for a nitrogen removal system. Overall, our results showed that nitrite accumulation was significantly influenced by PFOS, while nitrate reduction was slightly impacted.…”

“…The environmentally relevant levels of PFOA were 0.1-1 mg/L [22]. To investigate the effect of a high concentration of PFOA exposure on the PD process, 0.1-20 mg/L PFOA was set in our study according to previous studies [27]. The SBR was operated for nearly 180 days, and the whole period was divided into seven phases depending on the PFOA concentrations, i.e., phase I (days 0-25, 0 mg-PFOA/L), phase II (days 26-50, 0.1 mg-PFOA/L), phase III (days 51-75, 0.5 mg-PFOA/L), phase IV (days 76-100, 2 mg-PFOA/L), phase V (days 101-125, 5 mg-PFOA/L), phase VI (days 126-150, 10 mg-PFOA/L), and phase VII (days 151-175, 20 mg-PFOA/L).…”