Next Article in Journal
Influence of Solar Photovoltaic System on the Concentration and Environmental Risks of Heavy Metals in Subsidence Pond Water from Coal Mining Area: A Case Study from Huainan Subsidence Pond
Previous Article in Journal
The Adsorptive Removal of Bengal Rose by Artichoke Leaves: Optimization by Full Factorials Design
Previous Article in Special Issue
Removal of Per- and Polyfluoroalkyl Substances by Electron Beam and Plasma Irradiation: A Mini-Review
Font Type:
Arial Georgia Verdana
Font Size:
Aa Aa Aa
Line Spacing:
Column Width:

Insight into the Impacts and Removal Pathways of Perfluorooctanoic Acid (PFOA) in Anaerobic Digestion

College of the Environment & Ecology, Xiamen University, South Xiang’an Road, Xiang’an District, Xiamen 361102, China
School of Environmental Science and Engineering, Suzhou University of Science and Technology, Suzhou 215009, China
Key Laboratory of the Ministry of Education for Coastal and Wetland Ecosystem, Xiamen University, Xiamen 361102, China
Fujian Key Laboratory of Coastal Pollution Prevention and Control (CPPC), College of Environment and Ecology, Xiamen University, Xiamen 361102, China
Author to whom correspondence should be addressed.
Water 2022, 14(14), 2255;
Submission received: 11 June 2022 / Revised: 13 July 2022 / Accepted: 15 July 2022 / Published: 18 July 2022
(This article belongs to the Special Issue Removal of PFAS from Water)


Perfluorooctanoic acid (PFOA) that accumulates in wastewater and excess sludge interact with the anaerobes and deteriorate the energy recovery and pollutants removal performance in the anaerobic digestion (AD) system. However, the interaction between PFOA and microbial metabolism in the AD systems remains unclear. This study aimed to clarify the effects and mechanism of PFOA on the AD process as well as the removal pathways of PFOA in an AD system. The results showed that the methane recovery efficiency was inhibited by 7.6–19.7% with the increased PFOA concentration of 0.5–3.0 mg/L, and the specific methanogenesis activity (SMA) was inhibited by 8.6–22.3%. The electron transfer system (ETS) was inhibited by 22.1–37.3% in the PFOA-containing groups. However, extracellular polymeric substance (EPS) gradually increased due to the toxicity of PFOA, and the ratio of protein to polysaccharide shows an upward trend, which led to the formation of sludge aggregates and resistance to the toxic of PFOA. The PFOA mass balance analysis indicated that 64.2–71.6% of PFOA was removed in the AD system, and sludge adsorption was the main removal pathway, accounting for 36.1–61.2% of the removed PFOA. In addition, the anaerobes are proposed to have the potential to reduce PFOA through biochemical degradation since 10.4–28.2% of PFOA was missing in the AD system. This study provides a significant reference for the treatment of high-strength PFOA-containing wastes.

Graphical Abstract

1. Introduction

Perfluorinated compounds (PFCs) have been widely used as synthetic substances since the middle of the 19th century and they play a major role in industry, energy, and manufacturing [1]. PFCs synthetic products mainly include surfactants, paints, surface hydrophobic agents, textiles, and so on [2,3]. According to the survey results, the most common perfluorinated compounds in wastewater discharge in China include perfluorooctanoic acid (PFOA), perfluorooctane sulfonic acid (PFOS), and perfluorobutane sulfonic acid (PFBS). The concentration of PFBS in wastewater in a WWTP of Wuhan city, Hubei Province, reaches 1400 ng/L [4]. The highest PFOA content in Shanghai, Dalian, Guangzhou, and other urban sewage treatment plants is more than 6000 ng/L, far higher than that of the United States (9–24 ng/L), Japan (6.6–142.1 ng/L), and other developed countries [5]. PFOA is one of the most harmful organic pollutants because of its physiological toxicity and carcinogenicity [6,7,8]. Updated research results have shown that PFOA has been found in both human and animal bodies, and has irreversible toxic effects on mammalian organs. In one study, PFOA was found to lower blood sugar and increase insulin in mice [9]. PFOA (15–288 ng/L) has also been found in human breast milk [10]. Zhang et al. (2021) found that the concentration of PFOA in drinking water sources ranges from 12–128 ng/L after the investigation of water sources of The Yangtze River in China [11]. In addition, the daily intake of PFOA for adults and children will be 0.54 and 0.82 (ng/kg bw/day), respectively [12]. There is no doubt that this is a great harm to the human body. The world’s largest PFC manufacturer, 3M of the United States, stopped the production of PFOS in 2003 because of the potential threat to the environment and living organisms [13].
As a persistent organic pollutant, PFOA causes damage to the atmosphere, soil, and water [14]. The fluoride ion in PFOA has high electronegativity, replacing the C–H bond to form a highly stable C–F bond, with a bond energy of up to 485 kJ/mol, and is extremely difficult to break down [15]. Therefore, PFOA has strong stability and is not easy to degrade. The refractory characteristics of PFOA have led to continuous enrichment in excess sludge, with the highest concentration of 4.78 mg/kg detected in the residual dry sludge of sewage treatment plants in central and eastern China, which affects the reuse and recovery of sludge [16]. The anaerobic digestion (AD) treatment technology with the characteristics of less sludge production and high organic matter removal and resource recovery attracts much attention [17]. However, anaerobic bacteria are easily inhibited by heavy metals, antibiotics, and other substances, and hinder the AD process [18,19]. Similarly, PFOA is highly toxic and can reduce microbial activity to a certain extent. Previous studies found that microbial abundance in activated sludge decreased under PFOA exposure [20]. Meanwhile, PFOA was found to inhibit transcription, amino acid transport, and metabolism of microorganisms [21]. In a 40-day semi-continuous experiment, the presence of PFOA significantly reduced the COD removal rate in the AD process [22]. Microbial community analysis showed that the diversity of microbial community decreased in the PFOA-containing groups, and the relative abundance of Proteobacteria decreased by 5.59%, thus reducing the ability of sludge to degrade organic matter. Wang et al. (2021) found that the presence of PFOA had a negative impact on acidification and methane production; 3–60 ug/g TS of PFOA reduced the methane production by 11.1–19.2% [23]. PFOA inhibited acidification and methanation process by reducing the relative abundance of acid-producing and methanogenic bacteria.
At present, many studies have been carried out on how to remove PFOA from wastewater. Yang et al. (2020) confirmed that PFOA removal by aerobic granular sludge was mainly by adsorption. The removal rate was 32.0–36.4%, but no aerobic biodegradation was observed [24]. Previous studies have suggested that there is no conclusive evidence that PFOA can be degraded under aerobic conditions [25]. In contrast, Huang et al. (2022) found that anaerobic bacteria could degrade PFOA and the removal rate of AD system reached 63% [26]. Meester et al. (2004) compared the aerobic and anaerobic biodegradation of PFOA, with the conclusion that the aerobic process almost did not degrade, and the anaerobic process almost completely removed PFOA [27]. In summary, the AD process can effectively remove PFOA, but the interaction between AD and PFOA still needs to be further studied.
This study evaluated the effect of PFOA on AD metabolism by analyzing the effects of different concentrations of PFOA on volatile fatty acid (VFAs), methane production, electron transfer system (ETS), and extracellular polymeric substances (EPS). By measuring the change in PFOA content in sludge and mixed liquid, the removal pathways of PFOA were analyzed. Furthermore, it provides technical reference and scientific basis for the application of the AD process in the treatment of PFOA-enriched wastes.

2. Materials and Methods

2.1. Substrate and Inoculum

The anaerobic digestion sludge (ADS) used in this study was taken from the continuous operational AnMBR reactor, and the initial sludge concentrations were 17.1 g/L (total solid, TS) and 10.9 g/L (volatile solid, VS). The chemical oxygen demand (COD) concentration was controlled to be 2500 ± 20 mg/L with glucose as the carbon source, and the optimal element ratio was approximately C:N:P = 100:5:1. No PFOA was found in the original ADS. The PFOA of analytical pure grade used in the study was purchased from Sigma-Aldrich (Saint Louis, MO, USA). PFOA reserve solution with a concentration of 0.012 g/L was prepared and stored in a 4 °C refrigerator for later use.

2.2. The Batch Test Design and Operation

A serum bottle with a total volume of 120 mL and a working volume of 100 mL was used as the AD reaction system (ADS 70 mL and substrate 30 mL). To simulate the enrichment of PFOA in different scenarios, six PFOA concentration gradients (0.0, 0.5, 1.0, 1.5, 2.0, and 3.0 mg/L) were set. The initial pH was adjusted to 7.0 ± 0.1 with 1 mol/L HCl or NaOH to eliminate the influence of pH on the experiment. After completion of each serum bottle unit, the samples were aerated with 98% nitrogen for 5 min to create an anaerobic environment.

2.3. Determination Indexes and Analysis Methods

TS, VS, total COD (TCOD), and soluble COD (SCOD) were determined according to the standard methods [28]. During the entire experiment, gas production was measured daily, and a gas chromatograph (Panna A60, JiangSu, China) was used to analyze the gas components. After centrifugation and dilution (10,000 rpm, 5 min), the VFAs produced in the reaction were determined by gas chromatography (Panna, A91 Plus, Shanghai, China). The electron transport capacity of the anaerobic sludge ETS was determined by the method of Maurines-Carboneill et al. (1998) [29]. The EPS extraction method was derived from Deng et al. (2014) [30], and polysaccharides (PN) and proteins (PS) were measured by a visible light spectrophotometer (Hach-DR3900, Loveland, CO, USA) to characterize the changes in EPS. The extraction and determination of PFOA were carried out by Wang et al. (2022), and the concentration of PFOA in water samples and sludge was accurately determined by adding an internal standard (50 ng/L PFOA) [31].

2.4. Data Analysis Method

The cumulative methane production in the reaction process based on methane-producing potential energy was fitted with the Gomperz model, and the fitting formula was based on Li et al. (2022) [32], as shown in Equation (1).
P   = P 0 · exp exp R max · e P 0 · t 0   t + 1
where P is the actual methane production, mL; P0 is the maximum methane production, mL; Rmax is the maximum rate of methane production, mL/d; T0 is the methane-producing delay time, d; T is methanogenesis duration, d; and e is the natural log.
The calculation formula of the AD specific methanogenic activity (SMA) is shown in Equation (2).
S M A = P CH 4 VS 0
where SMA is the specific methanogenic activity of AD, mL/g·VSS; PCH4 is the cumulative methane production of each reactor with a concentration gradient of PFOA, mL; and VS0 is the initial VS of sludge, g.
In this study, a logistic model was used to fit the inhibition rate of PFOA on methane production [33]. The calculation of the methane production inhibition rate is shown in Equation (3).
q I = P 0   P e P 0
where qI is the inhibition rate of PFOA on AD methane production at each gradient level, %; P0 is the actual methane production of the blank group, mL; and Pe is the methane production of each experimental group, mL.
Langmuir and Freundlich thermodynamic adsorption models were used to fit the process of AD sludge adsorption of PFOA, as shown in Equations (4) and (5) [34].
Langmuir   model :   C e q e = 1 q m b + C e q m  
Freundlich   model :   l n q e = lnK F + 1 n lnC e
where Ce represents the concentration when adsorption reaches dynamic equilibrium, mg/L; Qe stands for equilibrium adsorption capacity, mg/L; Qm represents the maximum adsorption capacity of sludge, mg/g; KF and b are two model constants; and 1/n is the heterogeneity factor.
The degradation rate of PFOA is calculated with Equation (6).
E P F O A = PF 0   PF S   PF W PF 0  
where EPFOA is the degradation rate of PFOA, %; PF0 is the content of PFOA in each reactor, mg; PFS is the content of PFOA in sludge, mg; and PFW is the content of PFOA in supernatant, mg.
Since glucose is the only carbon source for COD and there is no hydrolysis process in glucose conversion, only acidification and methanation process efficiency are discussed in this study. The acidification efficiency and methanation efficiency of the reaction process are shown in Equations (7) and (8).
E A c i d = COD VFAs   COD CH 4 COD 0
E C H 4 = P CH 4 P
where EAcid and ECH4 are the acidification efficiency and methanation efficiency, respectively, %; CODVFAs and CODCH4 are the corresponding values of VFA content and methane production in each stage, mg/L. COD0 is the initial total COD in the reactor, mg/L. PCH4 and P are the actual methane production and theoretical methane production, mL.

3. Results and Discussion

3.1. Effects of PFOA on Energy Recovery

As shown in Figure 1I, the AD system was rapidly and continuously inhibited by PFOA. Comparing the methane production in the blank group, the methane production in the PFOA group decreased by 7.6%, 14.3%, 15.5%, 18.6%, and 19.7%, respectively. Under the stress of PFOA concentration gradient (0.5, 1.0, 1.5, 2.0, and 3.0 mg/L), as shown in Figure 1II, with the increase in PFOA concentration, the inhibition effect on methanogenesis gradually increased, but the inhibition rate of methane production gradually approached the maximum value of 20% based on the fitting results of logistic model. Therefore, the AD system in the PFOA exposure condition has a certain tolerance to PFOA. From the actual methane-producing rate data in Figure 1III, the SMA of the PFOA group at a concentration of 3.0 mg/L decreased by 7.8 mL/d·gVSS, and the inhibition rate reached 22.3% compared with the blank group. The fitting results of the logistic model indicated that the inhibition rate of methane production in PFOA groups had the same trend as that of SMA. The results showed that PFOA in the system reduced the methane-producing capacity of sludge and the potential load capacity of the reactor. At the same time, AD can withstand high concentration of PFOA and has a certain tolerance to the toxicity of PFOA, which will not lead to system collapse.
Acidogens in the AD system degrade organic matter into propionic acid, butyric acid, acetic acid, and other organic acids, and methanogens further degrade acetic acid to methane [35]. Therefore, the determination of the content of various organic acids in the process of AD, combined with methane production, can be applied to explain the changes in acidogenesis and methanogenesis rate of the reaction system. The concentration of VFAs during the reaction is shown in Figure 2I. On the first day of reaction, the concentration of VFAs in PFOA groups was slightly lower than that in the blank group, indicating that the acidification rate of the AD process decreased under PFOA stress. From the second day of the experiment, the VFA concentration in the blank group was lower, indicating that the utilization rate of VFAs in the blank group was faster and the methane-producing efficiency was higher. In addition, it was found that the acidification efficiency (Figure 2II) and methanation efficiency (Figure 2III) in the PFOA groups were always lower than those in the blank group, and the trend was relatively stable. On the first day of the experiment, the acidification efficiency of the PFOA groups was only 3.39–4.52% lower than that of the blank group. During the entire process, the methanation efficiency and cumulative methane production trend were similar, but the methanation efficiency was 21% lower than that of the blank group at the highest PFOA level of 3.0 mg/L. Jiao et al. (2022) also demonstrated that PFOA inhibited the acidification and methanation stages of AD and had no significant effect on the hydrolysis stage [36]. These results indicated that the stress of PFOA affected the acidification and methanogenesis stages, and reduced the energy recovery efficiency.

3.2. Process and Performance of PFOA Removal in AD

The concentration of PFOA in the supernatant decreased rapidly in a short time and reached the lowest value within 24 h in all the groups (Figure 3I). In previous studies, it was found that the removal rate of PFOA in wastewater by aerobic activated sludge is 32–36.4%, and the main method of removal is the adsorption of PFOA by sludge. In order to explain the reasons for the decrease of PFOA concentration in the reactors, Langmuir and Freundlich thermodynamic adsorption models were used in this research to fit the adsorption process. As shown in Table 1, the fitting correlation coefficient of the Freundlich model (R2 > 0.97) was higher than that of the Langmuir model (R2 > 0.67). The results indicated that the decrease in PFOA concentration was mainly caused by the multimolecular layer physical adsorption, and the fitting curves of PFOA absorbed by sludge within 24 h are shown in Figure 3II. The fitting results of the Freundlich model also showed that the saturated adsorption capacity of sludge to PFOA in each reactor (0.5, 1.0, 1.5, 2.0, and 3.0 mg/L PFOA) was 38.52, 84.89, 122.16, 161.83, and 239.52 ug/g·VSS. It is also found in Figure 3I that along with the AD reaction, PFOA adsorbed by sludge was desorbed again, increasing the concentration of PFOA in the supernatant. The results can be explained by the dynamic balance of adsorption and desorption in the AD system [37]. The adsorption process of PFOA by sludge can be divided into two stages. According to various physical and biochemical interactions of PFOA in the AD system, its removal pathways can be divided into two stages, as shown in Figure 3II. Stage 1 is the main process of rapid adsorption of PFOA by sludge within 24 h, and stage 2 is the sludge adsorption and desorption process. Some studies have shown that the enrichment of PFOA in sludge is related to temperature, pH, and hydrophilicity of the adsorbent. Among them, the pH of the solution changes the surface charge by affecting the functional groups in the sludge, zeta point position, and other factors and then affects the adsorption efficiency. In the study of Zhou et al. (2010), the adsorption capacity of activated sludge decreased with the pH increase of the solution. When the pH increased from 3 to 9.5, the adsorption capacity of PFOA decreased from 85% to 42% [38]. In this study, as shown in Figure 2I, VFAs were continuously degraded as the reaction progressed, and the pH in the system gradually recovered. Therefore, it can be speculated that the main reason for PFOA desorption can be attributed to the recovery of pH, so that the adsorbed PFOA was released again.
At the end of the reaction, the PFOA mass balance in the AD systems was analyzed, and the content of PFOA in solid and liquid phases of the system is shown in Figure 4. The results show that with the increase of PFOA concentration, the total removal rate of PFOA from the liquid phase did not fluctuate much, basically within the range of 60–70%. However, the mass balance results indicated that except for the PFOA in supernatant and sludge, 10.4–28.2% of PFOA disappeared from the AD process. It is reasonable to speculate that the AD process has a certain biodegradation of PFOA. To illustrate the performance of each concentration gradient of PFOA in the AD systems, the content and proportion of PFOA in each stage of the AD system are listed in Table 2. When the concentration of PFOA is 0.5 mg/L, the content of PFOA in the sludge phase is 0.31 mg/L, accounting for 61.2% of PFOA removal. However, at 3 mg/L, although the content of PFOA in sludge reaches 1.08 mg/L, the proportion of the total PFOA is only 36.1%. Combined with Figure 4 and Table 2, it was found that the higher the concentration of PFOA in the system, the stronger the biodegradation effect of AD system for PFOA. Therefore, the experimental results further illustrate the removal pathways of the AD system for different PFOA concentrations, that is, when the PFOA concentration is low, the removal pathway is mainly realized by adsorption, while when the PFOA concentration is high, the removal mainly depends on the combined action of biodegradation and sludge adsorption. Cao et al. (2022) showed that the average PFOA removal rate of anaerobic granular sludge was 52–55%, which was mainly caused by adsorption. However, it was found that PFOA could be degraded to C7F15 by acid decarboxylation [22]. Shahasavari et al. (2021) described the possible pathways of PFOA biodegradation [39]. The degradation process mainly involves p450 enzyme, benzoyl-CoA reductase (BCR), and other key enzymes that can promote PFOA degradation and release F from the C–F bond. Tiedt et al. (2017) showed that enzymatic defluorination represented by enyl-CoA hydrase can effectively solve the problem of high stability of C–F, and thus degrades PFOA [40]. Of course, the process and mechanism of AD degradation of PFOA need to be further confirmed by subsequent experiments.

3.3. Inhibition Mechanism of Anaerobic Digestion under PFOA Exposure

As mentioned previously, PFOA is toxic to microorganisms. In the AD system, to resist environmental toxicity, anaerobes secrete more EPS as a barrier to protect themselves from damage [41]. Furthermore, studies have shown that the ratio of PN/PS in EPS reflects the surface charge and hydrophilicity of sludge in the system [42]. In this study, the higher the concentration of PFOA exposed in the AD system, the more upwards the trend of PN/PS, indicating that anaerobic microorganisms further formed aggregates to resist the toxicity of the external environment [43]. The EPS content of each group after the experiment was measured, as shown in Figure 5. The ratio of PN/PS in PFOA groups increased from 4.93 to 6.95, which was increased by 14.67–45.82%. The results showed that proteins secreted by EPS played a leading role in the anti-toxicity of PFOA. The PN content in the EPS of the PFOA groups increased compared with that of the blank group, and it increased with increasing PFOA concentration. Proteins secreted by microbial cells promote sludge flocculation and agglomeration, and limit the conversion of organic matter to methane, resulting in further inhibition [44]. Therefore, PFOA inhibits AD methanogenesis not only through inhibiting microbial activity, but also through multiple effects of sludge toxic stress response. In addition, EPS in the AD system can effectively improve the adsorption capacity of microorganisms, promote the formation of microbial aggregates, and further improve the resilience of the AD system [45].
In the AD system, interspecific electron transfer from the acidogens to the methanogens is necessary for methane production. Under toxic environmental conditions, the response of microorganisms in the electron transfer process fluctuates greatly, which directly affects the methane production. At the end of the experiment, the ETS of sludge mixture was measured; as shown in Figure 6, the ETS of the blank group was 386.36 mg/(g·h). The PFOA groups were suppressed by a gradient of 22.06–37.38%, showing an overall downwards trend, and the results showed that PFOA had a direct negative effect on the interspecific electron transfer in the AD system. The electronic transfer is the basic process for organic matter degradation in AD. The decrease of ETS indicated that the electronic transfer ability between bacteria decreased under the stress of PFOA, thus inhibiting the growth of microorganisms [46]. The experimental results corresponded to the inhibition of methane recovery efficiency by PFOA, which mutually confirmed the inhibition of PFOA on sludge activity.

4. Conclusions

The effects of PFOA on energy recovery efficiency and microbial activity in an AD system as well as the removal process and mechanisms of PFOA were discussed in this study. The results showed that PFOA had a negative effect on the AD process. The maximum inhibition rate of PFOA on methane production was approximately 20%, indicating that AD has a certain tolerance to PFOA. At the same time, SMA of sludge under high concentration of PFOA was inhibited by 22.3%, EPS showed anti-toxic reaction, and ETS decreased by 22.06% to 37.38%. Therefore, the presence of PFOA will inhibit the activity of anaerobic bacteria and reduce energy recovery efficiency. During the AD treatment, approximately 64.2–71.6% of PFOA was removed. Sludge adsorption was the main pathway for PFOA removal. Meanwhile, 10.4–28.2% PFOA was missing in AD systems, probably due to biodegradation. PFOA has high biological resistance, and physical and biochemical removal of PFOA requires additional economic input. Combined with the advantages of AD energy recovery, rational use of AD to remove PFOA will be a good choice.

Author Contributions

Conceptualization, Y.Z.; methodology, H.X., Y.C. and Y.W.; validation, Y.Z., W.C. and Z.K.; investigation, H.X., Y.C. and Y.W.; data curation, H.X.; writing—original draft preparation, H.X., Y.C. and Y.W.; writing—review and editing, Y.Z.; visualization, H.X.; supervision, Y.Z., W.C. and Z.K.; project administration, Y.Z.; funding acquisition, Y.Z. All authors have read and agreed to the published version of the manuscript.


This research was funded by the National Key R&D Program of China (2017YFE0127300), the Fundamental Research Funds for the Central Universities (20720200112), and the Science Foundation of Fujian Province (2020J01046).

Institutional Review Board Statement

Not applicable.

Informed Consent Statement

Not applicable.

Data Availability Statement

The data sets supporting the results of this article are freely available upon request to the corresponding author.


We thank the key laboratory of ministry of education for coastal and wetland ecosystems for supporting this work. We are also grateful to all the reviewers for their useful comments and suggestions.

Conflicts of Interest

The authors declare no conflict of interest.


  1. Cui, D.N.; Li, X.R.; Quinete, N. Occurrence, fate, sources and toxicity of PFAS: What we know so far in Florida and major gaps. Trends Anal. Chem. 2020, 130, 115976. [Google Scholar] [CrossRef]
  2. Dauchy, X.; Boiteux, V.; Bach, C.; Colin, A.; Hemard, J.; Rosin, C.; Munoz, J.F. Mass flows and fate of per- and polyfluoroalkyl substances (PFASs) in the wastewater treat ment Plant of a fluorochemical manufacturing facility. Sci. Total Environ. 2017, 576, 549–558. [Google Scholar] [CrossRef] [PubMed]
  3. Lehmler, H.-J. Synthesis of environmentally relevant fluorinated surfactants—A review. Chemosphere 2005, 58, 1471–1496. [Google Scholar] [CrossRef] [PubMed]
  4. Liu, Z.; Lu, Y.; Wang, P.; Wang, T.; Liu, S.; Johnson, A.C.; Sweetman, A.J.; Baninla, Y. Pollution pathways and release estimation of perfluorooctane sulfonate (PFOS) and perfluorooctanoic acid (PFOA) in central and eastern China. Sci. Total Environ. 2017, 580, 1247–1256. [Google Scholar] [CrossRef] [Green Version]
  5. Lu, Y.; Gao, J.; Nguyen, H.T.; Vijayasarathy, S.; Du, P.; Li, X.; Yao, H.; Mueller, J.F.; Thai, P.K. Occurrence of per- and polyfluoroalkyl substances (PFASs) in wastewater of major cities across China in 2014 and 2016. Chemosphere 2021, 279, 130590. [Google Scholar] [CrossRef]
  6. Kudo, N.; Ashima, Y.K. Toxicity and toxicokinetics of perfluorooctanoic acid in humans and animals. Toxicol. Sci. 2003, 28, 49–57. [Google Scholar] [CrossRef] [Green Version]
  7. National Toxicology Program. Toxicology and Carcinogenesis Studies of Perfluorooctanoic Acid Administered in Feed to Sprague Dawley (Hsd: Sprague Dawley SD) Rats. Res. Triangle Park 2020, 598, NTP-TR-598. [Google Scholar]
  8. Field, J.A.; Seow, J. Properties, occurrence, and fate of fluorotelomer sulfonates. Crit. Rev. Environ. Sci. Technol. 2017, 47, 643–691. [Google Scholar] [CrossRef]
  9. Wu, X.; Xie, G.; Xu, X.; Wu, W.; Yang, B. Adverse bioeffect of perfluorooctanoic acid on liver metabolic function in mice. Environ. Sci. Pollut. Res. 2018, 25, 4787–4793. [Google Scholar] [CrossRef]
  10. Barbarossa, A.; Masetti, R.; Gazzotti, T.; Zama, D.; Astolfi, A.; Veyrand, B.; Pession, A.; Pagliuca, G. Perfluoroalkyl substances in human milk: A first survey in Italy. Environ. Int. 2013, 51, 27–30. [Google Scholar] [CrossRef]
  11. Zhang, Y.; Zhou, Y.; Zhang, A.; Li, J.; Yu, J.; Dou, Y.; He, J.; Kong, D. Perfluoroalkyl substances in drinking water sources along the Yangtze River in Jiangsu Province, China: Human health and ecological risk assessment. Ecotoxicol. Environ. Saf. 2021, 218, 112289. [Google Scholar] [CrossRef] [PubMed]
  12. Li, N.; Ying, G.-G.; Hong, H.; Deng, W.-J. Perfluoroalkyl substances in the urine and hair of preschool children, airborne particles in kindergartens, and drinking water in Hong Kong. Environ. Pollut. 2021, 270, 116219. [Google Scholar] [CrossRef] [PubMed]
  13. Olsen, G.W.; Mair, D.C.; Church, T.R.; Ellefson, M.E.; Reagen, W.K.; Boyd, T.M.; Herron, R.M.; Medhdizadehkashi, Z.; Nobiletti, J.B.; Rios, J.A.; et al. Decline in Perfluorooctanesulfonate and Other Polyfluoroalkyl Chemicals in American Red Cross Adult Blood Donors, 2000—2006. Environ. Sci. Technol. 2008, 42, 4989–4995. [Google Scholar] [CrossRef] [PubMed] [Green Version]
  14. Shang, E.; Li, Y.; Niu, J.; Li, S.; Zhang, G.; Wang, X. Photocatalytic degradation of perfluorooctanoic acid over Pb-BiFeO3/rGo catalyst: Kinetics and mechanism. Chemosphere 2018, 211, 34–43. [Google Scholar] [CrossRef]
  15. Lenka, S.P.; Kah, M.; Padhye, L.P. A review of the occurrence, transformation, and removal of poly- and perfluoroalkyl substances (PFAS) in wastewater treatment plants. Water Res. 2021, 199, 117187. [Google Scholar] [CrossRef]
  16. Jiang, J.; Zhang, Y.; Li, K.; Wang, Q.; Gong, C.; Li, M. Volatile fatty acids production from food waste: Effects of pH, temperature, and organic loading rate. Bioresour. Technol. 2013, 143, 525–530. [Google Scholar] [CrossRef]
  17. Rajagopal, R.; Saady, N.M.C.; Torrijos, M.; Thanikal, J.V.; Hung, Y.T. Sustainable Agro-Food Industrial Wastewater Treatment Using High Rate Anaerobic Process. Water 2013, 5, 292–311. [Google Scholar] [CrossRef] [Green Version]
  18. Mudhoo, A.; Kumar, S. Effects of heavy metals as stress factors on anaerobic digestion processes and biogas production from biomass. Int. J. Environ. Sci. Technol. 2013, 10, 1383–1398. [Google Scholar] [CrossRef] [Green Version]
  19. Xiao, L.; Wang, Y.; Lichtfouse, E.; Li, Z.; Kumar, P.S.; Liu, J.; Feng, D.; Yang, Q.; Liu, F. Effect of Antibiotics on the Microbial Efficiency of Anaerobic Digestion of Wastewater: A Review. Front. Microbiol. 2021, 11, 611613. [Google Scholar] [CrossRef]
  20. Ji, J.; Peng, L.; Redina, M.M.; Gao, T.; Khan, A.; Liu, P.; Li, X. Perfluorooctane sulfonate decreases the performance of a sequencing batch reactor system and changes the sludge microbial community. Chemosphere 2021, 279, 130596. [Google Scholar] [CrossRef]
  21. Cai, Y.; Wang, Q.; Zhou, B.; Yuan, R.; Wang, F.; Chen, Z.; Chen, H. A review of responses of terrestrial organisms to perfluorinated compounds. Sci. Total Environ. 2021, 793, 148565. [Google Scholar] [CrossRef] [PubMed]
  22. Cao, L.; Liao, Y.; Su, C.; Tang, L.; Qi, Z.; Wei, L.; Wu, J.; Gao, S. Effects of PFOA on the physicochemical properties of anaerobic granular sludge: Performance evaluation, microbial community and metagenomic analysis. J. Environ. Manag. 2022, 313, 114936. [Google Scholar] [CrossRef] [PubMed]
  23. Wang, C.; Wu, L.; Zhang, Y.-T.; Wei, W.; Ni, B.-J. Unravelling the impacts of perfluorooctanoic acid on anaerobic sludge digestion process. Sci. Total Environ. 2021, 796, 149057. [Google Scholar] [CrossRef]
  24. Yang, G.; Zhang, N.; Yang, J.; Fu, Q.; Wang, Y.; Wang, D.; Tang, L.; Xia, J.; Liu, X.; Li, X.; et al. Interaction between perfluorooctanoic acid and aerobic granular sludge. Water Res. 2020, 169, 115249. [Google Scholar] [CrossRef] [PubMed]
  25. Trojanowicz, M.; Bojanowska-Czajka, A.; Bartosiewicz, I.; Kulisa, K. Advanced Oxidation/Reduction Processes treatment for aqueous perfluorooctanoate (PFOA) and perfluorooctanesulfonate (PFOS)—A review of recent advances. Chem. Eng. J. 2018, 336, 170–190. [Google Scholar] [CrossRef]
  26. Huang, D.; Xu, R.; Sun, X.; Li, Y.; Xiao, E.; Xu, Z.; Wang, Q.; Gao, P.; Yang, Z.; Lin, H.; et al. Effects of perfluorooctanoic acid (PFOA) on activated sludge microbial community under aerobic and anaerobic conditions. Environ. Sci. Pollut. Res. 2022, 286, 314. [Google Scholar] [CrossRef]
  27. Meesters, R.J.W.; Schröder, H.F. Perfluorooctane sulfonate—A quite mobile anionic anthropogenic surfactant, ubiquitously found in the environment. Water Sci. Technol. 2004, 5, 235–242. [Google Scholar] [CrossRef]
  28. APHA (American Public Health Association). Standard Methods for the Examination of Water and Wastewater; APHA (American Public Health Association): Washington, DC, USA, 1998. [Google Scholar]
  29. Maurines-Carboneill, C.; Pernelle, J.J.; Morin, L.; Sachon, G.; Leblon, G. Relevance of the INT response as an indicator of ETS activity in monitoring heterotrophic aerobic bacterial populations in activated sludges. Water Res. 1998, 32, 1213–1221. [Google Scholar] [CrossRef]
  30. Deng, L.; Guo, W.; Ngo, H.H.; Zhang, J.; Liang, S.; Xia, S.; Zhang, Z.; Li, J. A comparison study on membrane fouling in a sponge-submerged membrane bioreactor and a conventional membrane bioreactor. Bioresour. Technol. 2014, 165, 69–74. [Google Scholar] [CrossRef]
  31. Wang, C.; Lu, Y.; Sun, B.; Zhang, M.; Mao, R.; Li, X.; Song, S.; Zhao, J.; Yu, M.; Shi, Y.; et al. Biomanipulation impacts on per-and polyfluoroalkyl substances accumulation and trophic transfer in an eutrophic lake. Environ. Int. 2022, 160, 107057. [Google Scholar] [CrossRef]
  32. Li, Q.; Liu, Y.; Gao, W.; Wang, G.; Dzakpasu, M.; Li, Y.Y.; Chen, R. New insights into the mechanisms underlying biochar-assisted sustained high-efficient co-digestion: Reducing thermodynamic constraints and enhancing extracellular electron transfer flux. Sci. Total Environ. 2022, 811, 151416. [Google Scholar] [CrossRef] [PubMed]
  33. Martín, M.; Fernández, R.; Gutiérrez, M.; Siles, J. Thermophilic anaerobic digestion of pre-treated orange peel: Modelling of methane production. Process Saf. Environ. Prot. 2018, 117, 245–253. [Google Scholar] [CrossRef]
  34. Liu, J.; Jiang, J.; Aihemaiti, A.; Meng, Y.; Yang, M.; Xu, Y.; Gao, Y.; Zou, Q.; Chen, X. Removal of phosphate from aqueous solution using MgO-modified magnetic biochar derived from anaerobic digestion residue. J. Environ. Manag. 2019, 250, 109438. [Google Scholar] [CrossRef]
  35. Mulders, M.; Estevez-Alonso, A.; Stouten, G.R. Volatile fatty acid product spectrum as a function of the solids retention time in an anaerobic granular sludge process. J. Environ. Eng. 2020, 146, 04020091. [Google Scholar] [CrossRef]
  36. Jiao, Y.; Zou, M.; Yang, X.; Tsang, Y.F.; Chen, H. Perfluorooctanoic acid triggers oxidative stress in anaerobic digestion of sewage sludge. J. Hazard. Mater. 2022, 424, 127418. [Google Scholar] [CrossRef] [PubMed]
  37. Singh, N.; Basu, S.; Balakrishnan, M. Comprehensive treatment scheme for distillery wastewater targeting recovery of water, antioxidant compounds and biogas. J. Water Process Eng. 2020, 38, 101663. [Google Scholar] [CrossRef]
  38. Zhou, Q.; Deng, S.; Zhang, Q.; Fan, Q.; Huang, J.; Yu, G. Sorption of perfluorooctane sulfonate and perfluorooctanoate on activated sludge. Chemosphere 2010, 81, 453–458. [Google Scholar] [CrossRef]
  39. Shahsavari, E.; Rouch, D.; Khudur, L.S.; Thomas, D.; Aburto-Medina, A.; Ball, A.S. Challenges and Current Status of the Biological Treatment of PFAS—Contaminated Soils. Microbiol. Physiol. Metab. 2021, 8, 602040. [Google Scholar] [CrossRef]
  40. Tiedt, O.; Mergelsberg, M.; Eisenreich, W.; Boll, M. Promiscuous Defluorinating Enoyl-CoA Hydratases/Hydrolases Allow for Complete Anaerobic Degradation of 2-Fluorobenzoate. Microbiol. Physiol. Metab. 2017, 8, 2579. [Google Scholar] [CrossRef] [Green Version]
  41. Liu, J.; Yang, Q.; Wang, D.; Li, X.; Zhong, Y.; Li, X.; Deng, Y.; Wang, L.; Yi, K.; Zeng, G. Enhanced dewaterability of waste activated sludge by Fe(II)—activated peroxymonosulfate oxidation. Bioresour. Technol. 2016, 206, 134–140. [Google Scholar] [CrossRef]
  42. Xu, J.; Yu, H.Q.; Li, X.Y. Probing the contribution of extracellular polymeric substance fractions to activated-sludge bioflocculation using particle image velocimetry in combination with extended DLVO analysis. Chem. Eng. J. 2016, 303, 627–635. [Google Scholar] [CrossRef]
  43. Deng, S.; Wang, L.; Su, H. Role and influence of extracellular polymeric substances on the preparation of aerobic granular sludge. J. Environ. Manag. 2016, 173, 49–54. [Google Scholar] [CrossRef] [PubMed]
  44. Guo, J.; Kang, Y. Characterization of sulfate-reducing bacteria anaerobic granular sludge and granulometric analysis with grey relation. Korean J. Chem. Eng. 2018, 35, 1829–1835. [Google Scholar] [CrossRef]
  45. Lu, S.; Li, X.; Xi, Y.; Liu, H.; Zhang, Z.; Huang, Y.; Xie, T.; Liu, Y.; Quan, B.; Zhang, C.; et al. Insight the roles of loosely-bound and tightly-bound extracellular polymeric substances on Cu2+, Zn2+ and Pb2+ biosorption process with Desulfovibrio vulgaris. J. Colloid Interface Sci. 2021, 596, 408–419. [Google Scholar] [CrossRef] [PubMed]
  46. Qin, R.; Lin, X.; Chen, Z.; Su, C.; Zhu, F.; Yang, W.; Chen, Z.; Lu, P. Evaluation of characteristics and microbial community of anaerobic granular sludge under microplastics and aromatic carboxylic acids exposure. Sci. Total Environ. 2021, 792, 148361. [Google Scholar] [CrossRef] [PubMed]
Figure 1. Cumulative methane production of AD under different levels of PFOA stress (I), fitting curve of energy recovery from inhibited AD under different concentrations of PFOA (II), and fitting curve of sludge activity variation under PFOA stress (III).
Figure 1. Cumulative methane production of AD under different levels of PFOA stress (I), fitting curve of energy recovery from inhibited AD under different concentrations of PFOA (II), and fitting curve of sludge activity variation under PFOA stress (III).
Water 14 02255 g001
Figure 2. Changes of VFAs content in the reaction process (I), anaerobic digestion acidification efficiency (II), and methanogenesis efficiency (III) under PFOA exposure.
Figure 2. Changes of VFAs content in the reaction process (I), anaerobic digestion acidification efficiency (II), and methanogenesis efficiency (III) under PFOA exposure.
Water 14 02255 g002
Figure 3. Change of PFOA concentration in supernatant of each reactor (I) and thermodynamic model fitting results of sludge adsorption PFOA amount within 24 h (II) (Figure 3a–e initial concentrations of PFOA were 0.5, 1.0, 1.5, 2.0, and 3.0 mg/L).
Figure 3. Change of PFOA concentration in supernatant of each reactor (I) and thermodynamic model fitting results of sludge adsorption PFOA amount within 24 h (II) (Figure 3a–e initial concentrations of PFOA were 0.5, 1.0, 1.5, 2.0, and 3.0 mg/L).
Water 14 02255 g003
Figure 4. PFOA content in sludge and supernatant of each reactor and the removal rate of PFOA by the AD reaction system.
Figure 4. PFOA content in sludge and supernatant of each reactor and the removal rate of PFOA by the AD reaction system.
Water 14 02255 g004
Figure 5. Changes of EPS content and PN/PS variation trend in the AD system under different levels of PFOA stress.
Figure 5. Changes of EPS content and PN/PS variation trend in the AD system under different levels of PFOA stress.
Water 14 02255 g005
Figure 6. Changes of microbial electron transport activity in AD system exposed to different concentrations of PFOA.
Figure 6. Changes of microbial electron transport activity in AD system exposed to different concentrations of PFOA.
Water 14 02255 g006
Table 1. After fitting Langmuir and Freundlich adsorption models, the R2 of PFOA adsorbed by sludge and the saturated adsorption capacity of sludge to PFOA.
Table 1. After fitting Langmuir and Freundlich adsorption models, the R2 of PFOA adsorbed by sludge and the saturated adsorption capacity of sludge to PFOA.
PFOA Concentration (mg/L)
Langmuir model R20.79260.67130.82210.86320.9079
Freundlich model R20.97890.98980.98580.99020.9796
Saturated adsorption capacity (ug/g·VSS)38.518284.8912122.1567161.8340239.5228
Table 2. The proportion and content of PFOA in supernatant and sludge in each reactor.
Table 2. The proportion and content of PFOA in supernatant and sludge in each reactor.
PFOA Concentration (mg/L)
PFOA in sludgeProportion (%)61.247.747.043.436.1
Content (mg/L)0.3070.4770.7050.8681.084
PFOA in supernatantProportion (%)28.429.932.531.2335.7
Content (mg/L)0.1420.2990.4880.6241.072
OthersProportion (%)10.422.420.525.3728.2
Content (mg/L)0.0530.2230.3070.5070.843
Publisher’s Note: MDPI stays neutral with regard to jurisdictional claims in published maps and institutional affiliations.

Share and Cite

MDPI and ACS Style

Xie, H.; Chen, Y.; Wang, Y.; Kong, Z.; Cao, W.; Zhang, Y. Insight into the Impacts and Removal Pathways of Perfluorooctanoic Acid (PFOA) in Anaerobic Digestion. Water 2022, 14, 2255.

AMA Style

Xie H, Chen Y, Wang Y, Kong Z, Cao W, Zhang Y. Insight into the Impacts and Removal Pathways of Perfluorooctanoic Acid (PFOA) in Anaerobic Digestion. Water. 2022; 14(14):2255.

Chicago/Turabian Style

Xie, Hongyu, Yuqi Chen, Yuzheng Wang, Zhe Kong, Wenzhi Cao, and Yanlong Zhang. 2022. "Insight into the Impacts and Removal Pathways of Perfluorooctanoic Acid (PFOA) in Anaerobic Digestion" Water 14, no. 14: 2255.

Note that from the first issue of 2016, this journal uses article numbers instead of page numbers. See further details here.

Article Metrics

Back to TopTop