Effects of single and combined copper/perfluorooctane sulfonate on sequencing batch reactor process and microbial community in activated sludge

Harnessing the power of microbial consortia for the biodegradation of per- and polyfluoroalkyl substances: Challenges and opportunities

Per- and polyfluoroalkyl substances (PFAS) are persistent environmental pollutants that pose significant risks to human health and ecosystems owing to their widespread use and resistance to degradation. This study examines the potential of microbial consortia as a sustainable and effective strategy for biodegrading PFAS. It highlights how these complex communities interact with various PFAS, including perfluorocarboxylic acids, perfluorosulfonic acids, fluorotelomer alcohols, and fluorotelomer-based precursors. Despite the potential of microbial consortia, several challenges impede their application in PFAS remediation, including effective microbial species identification, inherent toxicity of PFAS compounds, co-contaminants, complications from biofilm formation, diversity of environmental matrices, and competition with native microbial populations. Future research should focus on refining characterization techniques to enhance our understanding of microbial interactions and functions within consortia. Integrating bioinformatics and system biology will enable a comprehensive understanding of microbial dynamics and facilitate the design of tailored consortia for specific PFAS compounds. Furthermore, field applications and pilot studies are essential for assessing the real-world effectiveness of microbial remediation strategies. Ultimately, advancing our understanding and methodologies will lead to efficient biodegradation processes and positioning microbial consortia as viable solutions for PFAS-contaminated environments.

The corncobs-loaded iron nanoparticles enhanced mechanism of denitrification performance in microalgal-bacterial aggregates system when treating low COD/TN wastewater

To improve denitrification efficiency of microalgal-bacterial aggregates (MABAs) when treating low carbon to nitrogen (C/N) ratio wastewater, CK (the biological control), C1 (untreated corncobs), C2 (alkali-treated corncobs), CFe1 (C1 loaded iron nanoparticles) and CFe2 (C2 loaded iron nanoparticles) five groups of experiments were installed under artificial light (1600 lm). After 36 h of experiment, NO3--N was almost completely converted in CFe1 following by CFe2 when the initial concentration was 60.1 mg/L, whose NO3--N conversion rates were 6.2 and 3.4 times faster than the CK group, respectively. The result showed that the corncobs-loaded iron nanoparticles (CFe1, CFe2) had the potential to promote denitrification process and the CFe1 was more effective. Meanwhile, the CFe1 and CFe2 resulted in a decreased content in extracellular polymeric substances (EPS) secretion because iron nanoparticles (Fes) promoted electron transport and alleviated the nitrate stress. Moreover, the electrochemical analysis of EPS showed that the corncobs and corncobs-loaded iron nanoparticles improved the electron transport rate and redox active substances production. The increase in electron transport activity (ETSA), adenosine triphosphate (ATP) and nicotinamide adenine dinucleotide (NADH) also indicated that the CFe1 and CFe2 promoted microbial metabolic activity and the electron transport rate in MABAs. In addition, the CFe1 group enhanced the enrichment of Proteobacteria, Patescibacteria, Chlorophyta and Ignavibacteriae, which was contributed to the nitrogen removal performance of MABAs. In summary, the enhancement mechanism of corncobs-loaded iron nanoparticles on denitrification process of MABAs was depicted through EPS secretion, electrochemical characteristics, microbial metabolic activity and microbial community. The article provides a viable program for enhancing the denitrification performance of MABAs when treating low C/N wastewater.

The roles of typical emerging pollutants on N2O emissions during biological nitrogen removal from wastewater

N2O as a potent greenhouse gas often generates in the biological nitrogen removal (BNR) processes during wastewater treatment, which makes BNR become an important greenhouse gas emission source. The emerging pollutants (EPs) are ubiquitous in wastewater and they have shown to influence the BNR processes. However, the deep discussion on potential impacts of EPs on N2O emissions during BNR is rare. Moreover, the experimental parameters for EPs investigation in most of literatures are generally not in line with real-world BNR processes, which calls for deep elucidating the roles of EPs on N2O production and emission. In this work, a critical review summarizes the existing literature about influences of typical EPs on N2O emissions and associated mechanisms during BNR, and it discusses the impacts of some easily overlooked factors, such as real EPs environmental concentrations, EPs bioaccumulation, and multiple EPs coexistence on N2O emissions. This review will provide an insight into exploring and mitigating threats posed by typical EPs on N2O emissions.

Emergence of per- and poly-fluoroalkyl substances (PFAS) and advances in the remediation strategies

A group of fluorinated organic molecules known as per- and poly-fluoroalkyl substances (PFAS) have been commonly produced and circulated in the environment. PFAS, owing to multiple strong CF bonds, exhibit exceptional stability and possess a high level of resistance against biological or chemical degradation. Recently, PFAS have been identified to cause numerous hazardous effects on the biotic ecosystem. As a result, extensive efforts have been made in recent years to develop effective methods to remove PFAS. Adsorption, filtration, heat treatment, chemical oxidation/reduction, and soil washing are a few of the physicochemical techniques that have shown their ability to remove PFAS from contaminated matrixes. However these methods also carry significant drawbacks, including the fact that they are expensive, energy-intensive, unsuitable for in-situ treatment, and requirement to be carried under dormant conditions. The metabolic products released upon PFAS degradation are largely unknown, despite the fact that thermal disintegration methods are widely used. In contrast to physical and chemical methods, biological degradation of PFAS has been regarded as efficient method. However, PFAS are difficult to instantly and completely metabolize through biological methods due to the limitations of biocatalytic mechanisms. Nevertheless, cost, easy-to-operate and environmentally safe are some of the advantages over its counterpart. The present review comprehensively discusses the occurrence of PFAS, the state-of-the science of remediation technologies and approaches applied, and the remediation challenges. The article also focuses on the future research directions toward the development of effective methods for PFAS-contaminated site in-situ treatment.

Impact of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) on secondary sludge microorganisms: removal, potential toxicity, and their implications on existing wastewater treatment regulations in Canada

Perfluorooctanoic acid (PFOA) and perfluorooctane sulfonic acid (PFOS) are two of the most commonly researched per- and polyfluoroalkyl substances (PFAS). Globally, many long-chain PFAS compounds including PFOS and PFOA are highly regulated and, in some countries, PFAS use in commercial products is strictly prohibited. Despite the legal regulation of these 'forever chemicals' under the Canadian Environmental Protection Act, PFOA and PFOS compounds are still found in high concentrations in discharges from wastewater treatment plants, both from liquid and sludge streams. Yet, their potential impact on wastewater treatment effectiveness remains poorly understood. The findings of this research show that: (1) PFOS and PFOA might be hindering the overall outcome treatment performance - calling into question the efficacy of Canada's existing wastewater treatment regulatory standard (Wastewater Systems Effluent Regulations, SOR/2012-139), and (2) specific microorganisms from the Thiobacillus and Pseudomonas genera seem capable of adsorbing PFOS and PFOA onto their cell wall and even degrading the chemicals, but it is unclear as to what extent degradation occurs. The results also raise questions whether existing wastewater regulations should be expanded to include the detection and monitoring of PFAS, as well as the establishment of a regulatory wastewater treatment plant discharge standard for PFAS that is protective of human and ecological health.

Inhibition of aged microplastics and leachates on methane production from anaerobic digestion of sludge and identification of key components

Large amounts of microplastics (MPs) accumulate in the sludge anaerobic digestion system after being treated by the wastewater treatment plants, inevitably leading to aging and chemicals leaching. However, no information is available about the effects of aged MPs and leachates on the anaerobic digestion of sludge. In this study, the effects of different aged MPs ((polyethylene (PE), polyethylene terephthalate (PET), polyvinyl chloride (PVC), and polylactic acid (PLA)) and leachates on anaerobic methanogenesis of sludge were investigated. PLA-related treatments caused no adverse effects on anaerobic digestion. While PE-, PET-, and PVC-related treatments significantly inhibited methane production with an order of leachates (26.4-42.4 %) > MPs (16.1-22.9 %) > aged MPs (2.4-11.8 %). For different leachates, PET leachate caused the strongest inhibitory effects. The same order was found for the methane potential and hydrolysis coefficient. These results suggest that the inhibition of MPs on methanogenesis is mainly caused by the leachates. Based on biochemical and microbial community analysis, the primary mechanism is that the leachates induce oxidative stress, damaging microbial cells and reducing microbial activity, consequently inhibiting methanogenesis. Furthermore, via effect-directed analysis, methyl benzoate (MB), dimethyl phthalate (DMP), and 2,4-Di-tert-butylphenol (DTBP) were identified as key components in the PET-leachate inhibiting anaerobic methanogenesis.

The role of dissolved organic matter during Per- and Polyfluorinated Substance (PFAS) adsorption, degradation, and plant uptake: A review

The negative effects of polyfluoroalkyl substances (PFAS) on the environment and health have recently attracted much attention. This article reviews the influence of soil- and water-derived dissolved organic matter (DOM) on the environmental fate of PFAS. In addition to being co-adsorped with PFAS to increase the adsorption capacity, DOM competes with PFAS for adsorption sites on the surface of the material, thereby reducing the removal rate of PFAS or increasing water solubility, which facilitates desorption of PFAS in the soil. It can quench some active species and inhibit the degradation of PFAS. In contrast, before DOM in water self-degrades, DOM has a greater promoting effect on the degradation of PFAS because DOM can complex with iron, iodine, among others, and act as an electron shuttle to enhance electron transfer. In soil aggregates, DOM can prevent microorganisms from being poisoned by direct exposure to PFAS. In addition, DOM increases the desorption of PFAS in plant root soil, affecting its bioavailability. In general, DOM plays a bidirectional role in adsorption, degradation, and plant uptake of PFAS, which depends on the types and functional groups of DOM. It is necessary to enhance the positive role of DOM in reducing the environmental risks posed by PFAS. In future, attention should be paid to the DOM-induced reduction of PFAS and development of a green and efficient continuous defluorination technology.

Evaluation of the ecological impacts of short- and long-chain perfluoroalkyl acids on constructed wetland systems: Perfluorobutyric acid and perfluorooctanoic acid

Perfluoroalkyl substances (PFASs) contamination of aquatic system has attracted widespread attention in recent years. From both plant and microbial perspectives, the ecological risk of CWs by comparing PFASs with different chain lengths have not been fully understood. In this study, the influences of perfluorobutyric acid (PFBA) and perfluorooctanoic acid (PFOA) as typical of short- and long-chains on the ecological effect of CWs have been specifically studied. The results showed that plants produced oxidative stress response and the activities of superoxide dismutase (SOD) and peroxidase (POD) in leaves were stimulated by 17.23-28.13% and 10.49-14.17% upon 10 mg/L PFBA and PFOA exposure. Under the high level of PFBA and PFOA stress, the chlorophyll content was reduced by 15.20-39.40% and lipid peroxidation was observed in leaves with the accumulation of malondialdehyde (MDA) at 1.20-1.22 times of the control. Dehydrogenase (DHA) exhibited the most sensitivity in the presence of PFBA and PFOA with an inhibition ratio of over 90%. The biotoxicity of PFOA was higher than that of PFBA in terms of the inhibition degree of several substrate enzymes. The information of Illumina Miseq sequencing indicated that the diversity and structure of microbial community in CWs were significantly altered by PFBA and PFOA addition and led to an enrichment of more PFASs-tolerant bacteria.

Effects of long-term perfluorooctane sulfonate (PFOS) exposure on activated sludge performance, composition, and its microbial community

The widespread presence and persistence of perfluorooctane sulfonate (PFOS) in wastewater treatment plants, as well as its toxicity and bioaccumulation potential, necessitates the investigation on their impact on bioreactor performance. A 48-day exposure test was adopted to study the effects of low (10 μg L-1) and high (1000 μg L-1) PFOS concentrations in a sequencing batch reactor on the performance, composition, and microbial community of activated sludge. The results suggested that adding PFOS at low and high concentrations lowered the removal efficiency of total nitrogen by 22.48% (p < 0.01) and 16.30% (p < 0.01) respectively, while enhanced that of total phosphorus by 1.87% (p > 0.05) and 7.07% (p < 0.05) respectively, compared with the control group. The addition of PFOS also led to the deterioration of activated sludge dewatering performance. Composition and spectroscopic measurements revealed that the PFOS dosage changed the composition of the activated sludge. Furthermore, the PFOS altered the structure and function of the activated sludge microbial community as well as key enzyme activities.

Biodegradation of per- and polyfluoroalkyl substances (PFAS): A review

Per- and polyfluoroalkyl substances (PFAS) are a group of chemicals widely manufactured for industrial and commercial applications in the past decades due to their remarkable stability as well as hydrophobic and lipophobic nature. PFAS species have been recognized as emerging environmental contaminants of concern due to their toxicity and environmental persistence, thereby attracting intensive research seeking effective technologies for their removal from the environment. The objective of this review is to provide a thorough analysis of the biodegradation of PFAS in multiple environmental matrices and offer a future outlook. By discussing targeted PFAS species, degradation intermediates, degradation efficiencies, and microbial species, a comprehensive summary of the known microbial species and their degradation pathways are presented. The biodegradation pathways for different types of PFAS species are summarized in two major categories, biodegradation with and without the cleavage of C-F bond. Existing uncertainties and future research directions for PFAS biodegradation are provided.

Perfluorooctane sulfonate decreases the performance of a sequencing batch reactor system and changes the sludge microbial community

The existence of perfluorooctane sulfonate (PFOS) in large quantities threatens environment biosafety. However, the fate of PFOS in a sequencing batch reactor (SBR) system and its influence in system has not yet been revealed. In this study, the fate and behavior of PFOS in an SBR processing system were investigated. Mass balance analyses revealed that PFOS removal was mainly through adsorption. After the reactors were run for 20 days, the PFOS (100 mg/L) removal rate was only 28%. Under the influence of PFOS, the removal rates of chemical oxygen demand (COD) and ammonia nitrogen dropped rapidly from 92, 98% to 23, 35% in the 20th day of system operation, respectively, while, accumulation of nitrite and nitrate was reduced. Compared with the control group, PFOS stimulates microorganisms to secrete more soluble microbial products (SMP) and extracellular polymeric substances (EPS). The adsorption of PFOS and EPS causes sludge bulking and decreases settling. The richness and diversity of microorganisms decreased significantly, affecting the system's removal of COD and ammonia nitrogen. Therefore, the SBR system is not suitable for treating wastewater containing PFOS. It is necessary to remove PFOS through pretreatment to reduce its impact on the SBR system.

Degradation and effect of 6:2 fluorotelomer alcohol in aerobic composting of sludge

Perfluoroalkyl carboxylates (PFCAs) is toxic to the environment and human health. However, the degradation characteristics of fluorotelomer alcohols (FTOHs), precursors of PFACAs biodegradation, in the sludge during aerobic composting remain unclear. In this study, the degradation characteristics of 6:2 FTOH in sewage sludge by composting were researched and the influences of 6:2 FTOH on the composting process and microbial communities of the sludge were evaluated. After 52 days of composting, 6:2 FTOH retained only 0.73% of its original concentration, and its half-life was less than 1 d; 6:2 FTOH was degraded finally to perfluorohex unsaturated acid, perfluoropentanoic acid, 5:3 polyfluorinated acid (FTCA), 4:3 FTCA, and perfluorobutanoic acid through two pathways; and 6:2 FTCA and 6:2 fluorotel unsaturated acid were the intermediate products. Notably, dosing with 6:2 FTOH affected the composting process of sewage sludge. Additionally, 50 mg/kg 6:2 FTOH resulted in a decrease in the microbial richness and diversity of sludge compost. When compared with the compost without 6:2 FTOH, the proportion of Proteobacteria had increased, and the proportion of Firmicutes had decreased as the concentration of 6:2 FTOH increased. The negative effect of a dosage of 50 mg/kg 6:2 FTOH was more obvious than the effect of other treatments. This study expanded our understanding of the risk of sludge contaminated by 6:2 FTOH being used as a fertilizer after composting.

Monitoring the nitrous oxide emissions and biological nutrient removal from wastewater treatment: Impact of perfluorooctanoic acid

The impacts of perfluorooctanoic acid (PFOA) on biological nutrient removal and nitrous oxide (N₂O) emissions have been specifically studied. The experimental results show that PFOA inhibited nitrification, but promoted denitrification and reduced N₂O emissions without significantly affecting phosphorus removal. The existence of 20 mg/L of PFOA increased total nitrogen removal efficiency from 78.7 ± 6.89 % to 86.8 ± 6.39 % and reduced N₂O emission factor from 6.02 ± 0.24 % to 4.43 ± 0.10 %. The mechanism studies reveal that microorganisms released extracellular polymeric substances (EPS) under PFOA exposure to protect sludge cells against PFOA toxicity. The generated PFOA-EPS conjugates reduced the nitrification rate, but increased the denitrification rate by regulating the activity of oxidoreductases. In addition, PFOA reduced the activity of polyphosphate accumulating organisms and glycogen accumulating organisms to save carbon source for denitrification, which reduced the electronic competition between reductases, thereby achieving complete denitrification and N₂O mitigation. The promotion of PFOA for denitrification and N₂O mitigation can gain a more comprehensive cognition of the role of PFOA in wastewater treatment. The release mechanism of EPS can afford new insights for the development of effective methods to enhance nitrogen removal and reduce N₂O emissions.

Influences of hexafluoropropylene oxide (HFPO) homologues on soil microbial communities

Hexafluoropropylene oxide (HFPO) homologues, as emerging perfluoroalkyl substances (PFASs) to replace legacy PFASs, have wide applications in the organofluorine industry and have been detected in the global environment. However, it is still unclear what effect HFPO homologues will exert on microbial abundance, community structure and function. The objective of this study was to assess potential impacts of HFPO homologue acids on archaea, bacteria, and ammonia-oxidizing archaea (AOA) and bacteria (AOB) in the soil environment. Grassland soil microcosms were supplemented with low (0.1 mg/kg) or high (10 mg/kg) dosages of dimer, trimer and tetramer acids of HFPO (HFPO-DA, HFPO-TA, and HFPO-TeA), respectively. The amendment of HFPO homologues acids initially decreased the abundance of archaea and bacteria but increased them in the later period. The addition of HFPO homologues acids raised AOA abundance but restrained AOB growth during the whole incubation. AOA and AOB community structures showed considerable variations. Potential nitrifying rate (PNR) showed an increase in the initial period followed by a decline in the later period. HFPO-DA had a lasting and suppressive effect on AOB and PNR even at a nearly environmental level. Overall, HFPO homologues with different carbon chain lengths had different impacts on soil microbial community and ammonia oxidation.

New application of rutin: Repair the toxicity of emerging perfluoroalkyl substance to Pseudomonas stutzeri

Per- and polyfluoroalkyl substances (PFASs) are toxic to microorganisms, thereby affecting microbial communities in sludge and soil, but how to repair the toxicity of microorganisms remains unclear. In this study, rutin, an antioxidant, was added into a culture medium with an aerobic denitrification bacteria, Pseudomonas stutzeri, under the exposure of sodium perfluorononyloxy-benzenesulfonate (OBS) to evaluate the repair mechanisms of rutin to the toxicity of OBS to the bacteria. The results showed that rutin could repair the damage of OBS to cell structures, and reduce the death rates of the bacteria under OBS exposure. The dosage of rutin reduced the effect on the inhibition of denitrification ability of P. stutzeri under OBS exposure. Compared with the bacteria exposed to single OBS, the dosage of rutin resulted in that the death rates recovered from 96.2% to 66.4%, the growth inhibition rate decreased from 46.5% to 15.8%, the total nitrogen removal rate recovered from 66.9% to 100%, and the NO₂^- content recovered from 34.5 mg/L to 0.22 mg/L. The expressions of key denitrification genes (napA, nirS, norB, nosZ) were recovered after adding rutin under OBS exposure. Rutin changed the positive rate of reactive oxygen species, the relative superoxide dismutase and catalase activities in the bacteria which exposed to OBS. The mechanism by which rutin repaired the toxicity of OBS to P. stutzeri related to inhibiting the activities of antioxidant and denitrification enzymes rather than affecting the expressions of genes involved in these enzymes. This study sheds light on the repair method of micro-organics and reveals the repair mechanisms under PFASs exposure.

Insights into the effects of single and combined divalent copper and humic acid on the performance, microbial community and enzymatic activity of activated sludge from sequencing batch reactor

The performance, microbial community and enzymatic activity of activated sludge from four identical sequencing batch reactors (SBRs) were compared by treating synthetic wastewater under the single and combined divalent copper (Cu²⁺) at 20 mg/L and humic acid (HA) at 20 mg/L. Compared with the absence of Cu²⁺ and HA, the single HA slightly enhanced the oxygen uptake rate (OUR), the nitrification and denitrification rates and the activities of dehydrogenase, nitrifying enzymes and denitrifying enzymes, whereas the single Cu²⁺ had the opposite results. The combined Cu²⁺ and HA inhibited the OUR, nitrogen removal rate and enzymatic activity of activated sludge almost the same as the single Cu²⁺. The single HA had no obvious effect on the balance between the microbial oxidative stress and antioxidant activity. However, the variations of microbial reactive oxygen species production, peroxidase activity, catalase activity, superoxide dismutase activity, and lactate dehydrogenase release demonstrated that the combined Cu²⁺ and HA and single Cu²⁺ produced obvious toxicity to microorganisms in activated sludge. The microbial richness and diversity had some obvious changes under the single and combined Cu²⁺ and HA. The relative abundances of Nitrosomonas, Nitrospira and some denitrifying genera (e.g. Zoogloea, Dokdonella, Denitratisoma, Flavobacterium and Thermomonas) under the combined Cu²⁺ and HA were less than those under the single Cu²⁺.

Responses of nitrogen transformation processes and N2O emissions in biological nitrogen removal system to short-term ZnO nanoparticle stress

Although the adverse effects of ZnO nanoparticles (ZnO NPs) on biological nitrogen removal (BNR) processes have widely been reported, the impacts of ZnO NPs on the whole nitrogen transformation processes, especially the production of nitrous oxide (N₂O), a typical greenhouse gas in a BNR system have rarely been systematically studied yet. In this study, the performances of both the nitrification and denitrification processes were investigated and the N₂O emission was simultaneously monitored in a sequencing batch reactor (SBR) when exposed to 1, 25 or 50 mg/L ZnO NPs for one cycle. The dose-dependent ZnO NP depression effects were generally observed on denitrification processes, total nitrogen (TN) removal efficiency and N₂O emissions but not nitrification process. Meanwhile, the N₂O emission was positively correlated with NO₂^--N accumulation in the oxic stage. Further investigation showed that the expressions of nitrate (NO₃^-) reduction associated narG gene were down-regulated with the increase of NP stress, and the transcript ratios of NO₂^-/NO reduction gene to N₂O reduction one (nirK/nosZ and norB/nosZ) decreased. The released Zn²⁺ from ZnO NPs took an important role in the inhibition of denitrification processes. ZnO NPs addition also induced the dose-dependent variations in the superoxide dismutase (SOD) and catalase (CAT) activities, which probably contributed to the suppression of the excess reactive oxygen species (ROS) generations to mitigate nanotoxicity. The excessive secretion of protein (PN) in tightly bound EPS (TB-EPS) when ZnO NPs were no <25 mg/L further supported the system's potential self-regulation mechanism for nanotoxicity resistance. CAPSULE: The effects of ZnO NPs on the whole nitrogen transformation processes in a biological nitrogen removal sequencing batch reactor, including the N₂O emissions were investigated. The system's potential self-regulation mechanism for nanotoxicity resistance was addressed.

Antagonistic effect of zinc oxide nanoparticle and surfactant on anaerobic digestion: Focusing on the microbial community changes and interactive mechanism

The objective of this study was to evaluate the antagonistic effect of emerging pollutants of zinc oxide nanoparticles (ZnO NPs) and sodium dodecyl sulfate (SDS) on anaerobic digestion and explore their potential mechanism. The results indicated that at a low inhibitory concentration of ZnO NPs (1.0 mM), the practical co-inhibition was decreased by 24% and 18% in co-existence of 50 mg/L SDS and 300 mg/L SDS, respectively. More importantly, the co-existence of 300 mg/L SDS greatly enhanced methanogenesis of organics in seriously inhibited case (2.0 mM of ZnO NPs). The microbial community analysis showed that co-existed SDS enhanced the growth of Methanothrix, Methanosarcina and Methanobacterium. The antagonistic enhancement could be attributed to the net charge reversal, partially agglomeration of ZnO NPs and/or reduction of Zn²⁺ release in the presence of SDS. These findings could provide useful information for evaluating the co-inhibition of SDS and ZnO NPs on biological processes.

Enzyme response of activated sludge to a mixture of emerging contaminants in continuous exposure

The relevant information about the impacts caused by presence of emerging pollutants in mixtures on the ecological environment, especially on the more vulnerable compartments such as activated sludge (AS) is relatively limited. This study investigated the effect of ibuprofen (IBU) and triclosan (TCS), alone and in combination to the performance and enzymatic activity of AS bacterial community. The assays were carried out in a pilot AS reactor operating for two-weeks under continuous dosage of pollutants. The microbial activity was tracked by measuring oxygen uptake rate, esterase activity, oxidative stress and antioxidant enzyme activities. It was found that IBU and TCS had no acute toxic effects on reactor biomass concentration. TCS led to significant decrease of COD removal efficiency, which dropped from 90% to 35%. Continuous exposure to IBU, TCS and their mixtures increased the activities of glutathione s-transferase (GST) and esterase as a response to oxidative damage. A high increase in GST activity was associated with non-reversible toxic damage while peaks of esterase activity combined with moderate GST increase were attributed to an adaptive response.

Activated Sludge Microbial Community and Treatment Performance of Wastewater Treatment Plants in Industrial and Municipal Zones

Controlling wastewater pollution from centralized industrial zones is important for reducing overall water pollution. Microbial community structure and diversity can adversely affect wastewater treatment plant (WWTP) performance and stability. Therefore, we studied microbial structure, diversity, and metabolic functions in WWTPs that treat industrial or municipal wastewater. Sludge microbial community diversity and richness were the lowest for the industrial WWTPs, indicating that industrial influents inhibited bacterial growth. The sludge of industrial WWTP had low Nitrospira populations, indicating that influent composition affected nitrification and denitrification. The sludge of industrial WWTPs had high metabolic functions associated with xenobiotic and amino acid metabolism. Furthermore, bacterial richness was positively correlated with conventional pollutants (e.g., carbon, nitrogen, and phosphorus), but negatively correlated with total dissolved solids. This study was expected to provide a more comprehensive understanding of activated sludge microbial communities in full-scale industrial and municipal WWTPs.

Mechanism of oxytetracycline removal by aerobic granular sludge in SBR

In this study, oxytetracycline (OTC) as a target pollutant in swine wastewater was removed by aerobic granular sludge (AGS). The removal rate of 300 μg/L OTC in aerobic granular sludge sequencing batch reactor (AGSBR) increased to 88.00% in 33 days and maintained stable. The chemical oxygen demand (COD), ammonium nitrogen (NH₄⁺-N) and total phosphorus (TP) in wastewater were also efficiently removed. The removal of OTC mainly depended on the adsorption and biodegradation of AGS, and the biodegradation was increased obviously after AGS adaptation to OTC. The degradation products of OTC were analyzed by mass spectrometry. The analysis of metagenome sequencing revealed that the enzymes, such as glycosyl transferases (GTs), polysaccharide lyases (PLs) and auxiliary activities (AAs), may play an important role in the removal of OTC. The Lefse analysis showed that the Flavobacteriia, Flavobacteriales, Cryomorphaceae and Fluviicola were four kinds of microbes with significant difference in OTC feed reactor, which are considered to be drug-resistant bacteria in AGSBR. Furthermore, the dynamics of microbial community changed significantly at three levels, including the enrichment of drug-resistant microorganisms and the microorganisms that gradually reduced or even disappeared under the pressure of OTC.

Degradation of 2,2',4,4'-tetrabromodiphenyl ether by Pycnoporus sanguineus in the presence of copper ions

The degradation of 2,2',4,4'-tetrabromodiphenyl ether (BDE-47) by Pycnoporus sanguineus was investigated in order to explore the impact of the heavy metal Cu²⁺ on BDE-47 decomposition and the subsequent formation of metabolites, as well as to further elucidate the degradation mechanism of BDE-47. An increase in degradation rate from 18.63% to 49.76% in the first four days and its stabilization at (51.26 ± 0.08)% in the following days of BDE-47 incubation were observed. The presence of Cu²⁺ at 1 and 2 mg/L was found to promote the degradation rate to 56.41% and 60.79%, respectively, whereas higher level of Cu²⁺ (≥5 mg/L) inhibited the removal of BDE-47. The similar concentration effects of Cu²⁺ was also found on contents of fungal protein and amounts of metabolites. Both intracellular and extracellular enzymes played certain roles in BDE-47 transportation with the best degradation rate at 27.90% and 27.67% on the fourth and third day, individually. During the degradation of BDE-47, four types of hydroxylated polybrominated diphenyl ethers (OH-PBDEs), i.e., 6'-OH-BDE-47, 5'-OH-BDE-47, 4'-OH-BDE-17, 2'-OH-BDE-28, and two bromophenols, i.e., 2,4-DBP and 4-BP were detected and considered as degradation products. These metabolites were further removed by P. sanguineus at rates of 22.42%, 23.01%, 27.04%, 27.96%, 64.21%, and 40.62%, respectively.

Kinetics simulation of Cu and Cd removal and the microbial community adaptation in a periphytic biofilm reactor

Periphytic biofilm reactor (PBfR) shows great potential in pollutants removal. However, few studies were focused on mathematical model of pollutants removal in PBfR. A three-step PBfR was designed and a new model was developed to simulate the kinetics of Cu and Cd removal from simulated wastewater. The results show that the PBfR could remove 99.0% Cu and 99.7% Cd from liquid wastewater. The experiment data could be well fitted with a high correlation coefficients both for Cu and Cd. The microbial community in the PBfR could be self-adjusted to tolerate the toxicities of Cu and Cd, resulting in sustainable and high decontamination efficiencies. The eukaryote in the PBfR played a vital role in Cu and Cd removal. The prokaryote showed negative effect on Cu and Cd removal, though it had more diversity than eukaryote. This study provides a new approach for Cu and Cd removal and their kinetics simulation in photoautotrophic bioreactor.

Performance and mechanism of a novel algal-bacterial symbiosis system based on sequencing batch suspended biofilm reactor treating domestic wastewater

A novel algal-bacterial symbiosis system based on sequencing batch suspended biofilm reactor (A-SBSBR) was developed for simultaneously enhanced nitrogen (N) and phosphorus (P) removal from domestic wastewater. Results showed that the total N (TN) and P (TP) removal efficiencies in A-SBSBR increased to 69.91% and 94.78%, respectively. The mechanism analysis indicated that TN removal mainly occurred at non-aeration stage, and TP removal happened during the whole cycle in A-SBSBR. Compared to control SBSBR, TN removal by denitrification and anabolism and TP removal by anabolism in A-SBSBR increased by 12.70%, 7.64% and 50.13%, respectively. The Chlorophyll a accumulation in biofilm increased to 4.80 ± 0.08 mg/g. Algae related to Chlorella and Scenedesmus and bacteria related to Flavobacterium, Micropruina and Comamonadaceae were enriched in A-SBSBR and responsible for the enhanced nutrients removal effect. This study may provide a new solution to achieve nutrients removal enhancement from wastewater.

Joint toxicity on hepatic detoxication enzymes in goldfish (Carassius auratus) exposed to binary mixtures of lead and paraquat

Compared to single exposure, chemical mixtures might induce joint toxicity including additive, synergistic and antagonistic effects on both organisms and environment. Owing to the specific toxicity of oxidative stress and binding to proteins, lead (Pb) is generally recognized a non-essential and threatening heavy metal to animals and human. Paraquat (PQ) is a widely used herbicide in agriculture and can trigger oxidative stress as well as Pb. Little information was available about joint effects of the two chemicals on toxicological responses in organisms, especially in fish. In our present study, goldfish (Carassius auratus) were randomly exposed to single and combined experiments with different concentrations of Pb and PQ for 28 days. Activities of four enzyme biomarkers in liver, ethoxyresorufin-O-deethylase (EROD), 7-benzyloxy-4-trifluoromethyl-coumarin-O-debenzyloxylase (BFCOD), glutathione-S-transferase (GST) and UDP-glucuronosyltransferase (UGT) were evaluated in each experimental group on day 14 and 28. The results showed four enzyme levels were markedly reduced with the increase of concentrations in mixtures and prolonged exposure. The inhibitory EROD and BFCOD activities were not significantly changed in goldfish following PQ-treated groups with or without 0.5 mg/L Pb, which indicated PQ has more inhibitory toxicity on CYP450 enzymes than Pb in co-exposure groups. However, the reduced values of GST were observed only in the combinations containing high doses of Pb or PQ during experimental periods. Although the responses of UGT activity were similar to GST on 14th day, all combinations of Pb and PQ generated stronger inhibitions on UGT activities compared to individual Pb and PQ-treated group. These results suggested that combined exposure of Pb and PQ have more inhibitory toxicity on phase I enzymes than phase II enzymes.