Influence of polyether sulfone microplastics and bisphenol A on anaerobic granular sludge: Performance evaluation and microbial community characterization

Deciphering the inhibitory mechanisms of polystyrene microplastics on thermophilic methanogens from the insights of microbial metabolite profiling and metagenomic analyses

Due to the utilization of food packaging bags, a substantial amount of polystyrene microplastics (PS MPs) are introduced into the food waste (FW) treatment system during the pre-treatment process, potentially impacting the subsequent biochemical treatment system. In order to investigate the mechanism by which PS MPs affect anaerobic methanogenesis metabolism in thermophilic condition, this study analyzed the characteristics of methanogenesis in thermophilic anaerobic digestion (AD) of FW under different concentrations of PS MPs (100 μm, 10-200 mg/L). The results revealed a negative correlation between PS MPs concentration and methane (CH4) yield from FW. When the concentration of PS MPs reached 200 mg/L, CH4 yield decreased by 47.8 %. Further mechanistic investigations revealed that while the presence of PS MPs at lower concentrations could alleviate its adverse impact on methanogenesis by enhancing EPS content, the accumulation of reactive oxygen species (ROS) persisted with increasing PS MPs concentration, thereby inhibiting the activities of key enzymes involved in solubilization and acidification metabolisms (e.g., acetate kinase and F420). Metagenomics analysis indicated that the presence of PS MPs down-regulate abundance of genes for quorum sensing and CH4 metabolism pathways. These findings not only unveil potential detrimental effects of PS MPs on AD systems but also provide novel insights into comprehending and controlling the impact of MPs pollution on environmental preservation and energy recovery processes.

The aging and pollution behavior of microplastics in tap water supply system subjected to residual chlorine exposure

This study investigated the aging and pollution behavior of acrylonitrile butadiene styrene (ABS) and polycarbonate (PC) microplastics (MPs) exposed to residual chlorine in tap water distribution systems. The ABS and PC MPs in the aging processes were analyzed using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). Results revealed that 0.4 mg/L residual chlorine could induce morphological changes, increase surface oxygen-containing functional groups, and enhance the hydrophilicity of MPs at the CT value of 9216 mg·min/L. Additionally, both ABS and PC MPs released dissolved organic matter (DOM) into water, with higher DOM concentrations observed in the presence of residual chlorine. Besides, this interaction also led to the formation of trichloromethane (TCM). And the TCM production increased with higher MPs concentrations, smaller particle size, and longer chlorine exposure time.

Dissecting the effects of co-exposure to microplastics and sulfamethoxazole on anaerobic digestion

Microplastics (MPs) and antibiotics are frequently and simultaneously detected in sewage and sludge, raising global concerns in recent years. However, their combined effects on anaerobic digestion (AD) remain unclear. Herein, we evaluated the effects of the combinations of different MPs (i.e., polyethylene, polystyrene, polyvinyl chloride and polyethylene terephthalate) with sulfamethoxazole (SMX) on AD performance and microbial communities. The combined stress slightly decreased the chemical oxygen demand removal rate and total gas/methane production. Furthermore, co-exposure to MPs and SMX visibly changed the anaerobic sludge morphology during AD, reduced the methanogen activity, and increased the residual propionic acid concentration versus a control. The decreased relative abundances of Euryarchaeota ranged from 1.88% to 4.63% in the experimental groups compared with CK, suggesting that the microbial communities were inevitably affected by exposure to SMX alone or combined MPs/SMX. Interestingly, among the top 50 genera, only two were negatively related to a few antibiotic resistance genes, implying that sludge exhibited widespread multiple resistances. The correlation analysis between the MPs and microbial communities suggested that the MP properties, such as the aperture-desorption of MPs, may impact the microbial variations. This study will contribute to a deeper understanding of the impact of coexisting MPs/SMX on AD.

Multifaceted analysis of microplastic pollution dynamics in the Yamuna river: Assessing anthropogenic impacts and ecological consequences

Microplastics (MPs) are pervasive contaminants that pose significant ecological and human health risks, emerging as one of the most widespread anthropogenic pollutants in natural environments. This study investigates the abundance, characteristics, and distribution of microplastics (MPs) in the Yamuna River, encompassing 29 sampling points across urban, rural, and industrial zones in and around Delhi, Mathura, Haryana, and Agra. Microplastics were identified and quantified using Nile red dye staining and Micro-Raman spectroscopy, with particle size distribution predominantly between 2 μm to 80 μm and the largest detected particle measuring 256.5 μm. The average MPs concentration was 14,717 ± 4444 L-1, with a significant abundance of hazardous polymers such as polyethylene terephthalate (PET), polypropylene (PP), and polystyrene (PS). The study found that MPs were predominantly fragments and films (65.6 %) and fibers (30.6 %), with transparent particles being the most prevalent. The Pollution Load Index (PLI) consistently indicated high-risk levels (PLI > 100) at all sampling sites, highlighting substantial MP contamination. These results underscore the urgent need for continuous monitoring and the development of robust management strategies to address microplastic pollution in the Yamuna River. This study provides valuable insights into MPs spatial distribution and persistence, contributing to an improved understanding of their environmental impacts and guiding future mitigation and regulatory efforts.

Impact of phenolic-formaldehyde resin microplastics on anaerobic granular sludge: EPS interaction mechanisms and impacts on reactor performance

This paper investigates the effects of phenolic-formaldehyde resin microplastics (PF-MPs) with different particle sizes on anaerobic granular sludge (AnGS) and reveals the complex interaction mechanisms between extracellular polymeric substances (EPS) and PF-MPs through the combination of molecular dynamics simulations and spectroscopy. PF-MPs provide a new ecological niche for microorganisms. Microorganisms and EPS can adhere and accumulate on the surface of PF-MPs, producing highly active floc sludge inside the reactor, thereby increasing the chemical oxygen demand (COD) removal rate and methane production of the reactor. However, the high metabolic activity of floc sludge consumes the biodegradable components in EPS, resulting in loose rupture of the sludge particles and reduced particle size. In addition, small particle size S-PF can adhere to the sludge surface，which caused mass transfer barriers and reduced the expression of genes and enzyme activities for the sludge acidification process and the main methanogenic processes. Insufficient internal nutrients lead to endogenous metabolism within the granules, causing internal hollowing, which affects the density and settling performance of the sludge. Monolayer physical adsorption plays a major role in the adsorption of EPS on PF-MPs. 2D-COS and FTIR spectroscopy were used to elucidate the preferential binding of polysaccharides to PF-MPs. This paper explores the fate of PF-MPs in anaerobic systems and demonstrates the important role of EPS in the capture of microplastics by granular sludge, providing a theoretical basis for understanding the migration of microplastics in wastewater treatment.

Exogenous signaling molecules N-acyl-homoserine lactones promotes the reconstruction of sludge particles after impact with highly concentrated urea-formaldehyde resin microplastics

In this study, exogenous N-acyl-homoserine lactones (AHLs) was added to resist the stress by high concentration (0.5 g/L) of urea formaldehyde resin microplastics (UF-MPs) on anaerobic granular sludge (AnGS), aiming to provide a viable strategy for AnGS to withstand elevated levels of UF-MPs toxicity elucidate the intricate regulatory mechanism of AHL-mediated AnGS-QS regulation. The results showed that the three different signaling molecules (C4-HSL, C6-HSL, and C8-HSL) improved the performance of AnGS under high concentration (0.5 g/L) urea-formaldehyde resin stress, and increased sludge COD removal (4.48%, 4.76%, and 3.35%, respectively) and methanogenic activity (8.38%, 1.92%, and 18.76%, respectively). The addition of C4-HSL has the best effect on sludge particle size and strength, which is attributed to the fact that C4-HSL can significantly increase the content of polysaccharides and proteins in tightly bound extracellular polymeric substances (TB-EPS) (27.1% and 27.1%, respectively). C8-HSL most obviously promotes energy metabolism and EPS biosynthesis gene expression. Metagenomic analysis showed that trace AHLs could promote the abundance of enzymes and functional genes related to the main pathway of methane metabolism, increase the relative abundance of Methanothrix of acetophilic methanogens from 27.79% in the control group to 27.85% (C4-HSL), 28.90% (64-HSL), and 30.03% (C8-HSL), thereby improving community stability.

Plasticizers inhibit food waste anaerobic digestion performance by affecting microbial succession and metabolism

The widely existed plastic additives plasticizers in organic wastes possibly pose negative influences on anaerobic digestion (AD) performance, the direct evidence about the effects of plasticizers on AD performance is still lacking. This study evaluated the influencing mechanism of two typical plasticizers bisphenol A (BPA) and dioctyl phthalate on the whole AD process. Results indicated that plasticizers addition inhibited methane production, and the inhibiting effects were reinforced with the increase of concentration. By contrast, 50 mg/L BPA exhibited the strongest inhibition on methane production. Physicochemical analysis showed plasticizers inhibited the metabolism efficiency of soluble polysaccharide and volatile fatty acids. Microbial communities analyses suggested that plasticizers inhibited the direct interspecies electron transfer participators of methanogenic archaea (especially Methanosarcina) and syntrophic bacteria. Furthermore, plasticizers inhibited the methane metabolisms, key coenzymes (CoB, CoM, CoF420 and methanofuran) biosynthesis and the metabolisms of major organic matters. This study shed light on the effects of plasticizers on AD performance and provided new insights for assessing the influences of plasticizers or plastic additives on the disposal of organic wastes.

Evaluating effects of tetrabromobisphenol A and microplastics on anaerobic granular sludge: Physicochemical properties, microbial metabolism, and underlying mechanisms

Tetrabromobisphenol A (TBBPA) and microplastics are emerging contaminants of widespread concern. However, little is known about the effects of combined exposure to TBBPA and microplastics on the physicochemical properties and microbial metabolism of anaerobic granular sludge. This study investigated the effects of TBBPA, polystyrene microplastics (PS MP) and polybutylene succinate microplastics (PBS MP) on the physicochemical properties, microbial communities and microbial metabolic levels of anaerobic granular sludge. The results showed that chemical oxygen demand (COD) removal of sludge was lowest in the presence of TBBPA alone and PS MP alone with 33.21% and 30.06%, respectively. The microorganisms promoted the secretion of humic substances under the influence of TBBPA, PS MP and PBS MP. The lowest proportion of genes controlling glycolytic metabolism in sludge was 1.52% when both TBBPA and PS MP were added. Microbial reactive oxygen species were increased in anaerobic granular sludge exposed to MPS. In addition, TBBPA treatment decreased electron transfer of the anaerobic granular sludge and disrupted the pathway of anaerobic microorganisms in acquiring adenosine triphosphate, and MPs attenuated the negative effects of TBBPA on the acetate methanogenesis process of the anaerobic granular sludge. This study provides a reference for evaluating the impact of multiple pollutants on anaerobic granular sludge.

Electroactive properties of EABs in response to long-term exposure to polystyrene microplastics/nanoplastics and the underlying adaptive mechanisms

Given widespread presence of polystyrene (PS) microplastics/nanoplastics (MPs/NPs), the electroactive responses and adaptation mechanisms of electroactive biofilms (EABs) exposed long-term to PS-containing aquatic environments remain unclear. Therefore, this study investigated the impacts of PS MPs/NPs on electroactivity of EABs. Results found that EABs exhibited delayed formation upon initially exposure but displayed an increased maximum current density (Imax) after subsequent exposure for up to 55 days. Notably, EABs exposure to NH2PS NPs (EAB-NH2PSNPs) demonstrated a 50% higher Imax than the control, along with a 17.84% increase in viability and a 58.10% increase in biomass. The cytochrome c (c-Cyts) content in EAB-NH2PSNPs rose by 178.35%, benefiting the extracellular electron transfer (EET) of EABs. Moreover, bacterial community assembly indicated the relative abundance of electroactive bacteria increased to 87.56% in EAB-NH2PSNPs. The adaptability mechanisms of EABs under prolonged exposure to PS MPs/NPs predominantly operate by adjusting viability, EET, and bacterial community assembly, which were further confirmed a positive correlation with Imax through structural equation model. These findings provide deeper insights into long-term effects and mechanisms of MPs/NPs on the electroactive properties of EABs and even functional microorganisms in aquatic ecosystems.

Bisphenol A affects microbial interactions and metabolic responses in sludge anaerobic digestion

The widespread use of bisphenol A (BPA) has resulted in the emergence of new pollutants in various environments, particularly concentrated in sewage sludge. This study investigated the effects of BPA on sludge anaerobic digestion, focusing specifically on the interaction of microbial communities and their metabolic responses. While the influence of BPA on methane accumulation is not significant, BPA still enhanced the conversion of soluble COD, protein, and polysaccharides. BPA also positively influenced the hydrolysis-acidogenesis process, leading to 17% higher concentrations of volatile fatty acids (VFAs). Lower BPA levels (0.2-0.5 mg/kg dw) led to decreased hydrolysis and acidogenesis gene abundance, indicating metabolic inhibition; conversely, higher concentrations (1-5 mg/kg dw) increased gene abundance, signifying metabolic enhancement. Diverse methane metabolism was observed and exhibited alterations under BPA exposure. The presence of BPA impacted both the diversity and composition of microbial populations. Bacteroidetes, Proteobacteria, Firmicutes, and Chloroflexi dominated in BPA-treated groups and varied in abundance among different treatments. Changes of specific genera Sedimentibacter, Fervikobacterium, Blvii28, and Coprothermobacter in response to BPA, affecting hydrolysis and acetogenesis. Archaeal diversity declined while the hydrogenotrophic methanogen Methanospirillum thrived under BPA exposure. BPA exposure enabled microorganisms to form structured community interaction networks and boost their metabolic activities during anaerobic digestion. The study also observed the enrichment of BPA biodegradation pathways at high BPA concentrations, which could interact and overlap to ensure efficient BPA degradation. The study provides insights into the digestion performance and interactions of microbial communities to BPA stress and sheds light on the potential effect of BPA during anaerobic digestion.

Microplastics' toxic effects and influencing factors on microorganisms in biological wastewater treatment units

Prior to entering the water body, microplastics (MPs) are mostly collected at the sewage treatment plant and the biological treatment unit is the sewage treatment facility's central processing unit. This review aims to present a comprehensive analysis of the detrimental impacts of MPs on the biological treatment unit of a sewage treatment plant and it covers how MPs harm the effluent quality of biological treatment processes. The structure of microbial communities is altered by MPs presence and additive release, which reduces functional microbial activity. Extracellular polymers, oxidative stress, and enzyme activity are explored as micro views on the harmful mechanism of MPs on microorganisms, examining the toxicity of additives released by MPs and the harm caused to microorganisms by harmful compounds that have been adsorbed in the aqueous environment. This article offers a theoretical framework for a thorough understanding of the potential problems posed by MPs in sewage treatment plants and suggests countermeasures to mitigate those risks to the aquatic environment.

Enhanced methane production with co-feeding spent coffee grounds using spare capacity of existing anaerobic food waste digesters

With increasing coffee consumption worldwide, the efficient and sustainable management of spent coffee grounds (SCG) has become increasingly challenging. This study investigated the anaerobic co-digestion of small amounts of SCG with food waste (FW) at increasing co-feeding ratios of 1:100-1:10 (volatile solids basis) to assess the possibility of SCG treatment using the spare capacity of existing anaerobic digesters. Co-feeding SCG increased methane production compared to FW mono-digestion in the tested range of co-feeding ratios without compromising process stability. Methane yield did not further increase when the SCG/FW ratio increased above 4%, and process failure occurred at a 1:10 co-feeding ratio without trace element supplementation. The enhanced methanogenic performance was attributed to increased protein removal efficiency, which was potentially related to the promotion of peptide hydrolysis. The overall results suggest that co-feeding appropriate small amounts of SCG to FW digesters can be a realistic sustainable option for SCG management.

Effects of microplastics on the properties of different types of sewage sludge and strategies to overcome the inhibition: A review

Microplastics have been identified as an emerging pollutant. When microplastics enter wastewater treatment plants, the plant traps most of the microplastics in the sludge during sewage treatment. Therefore, the effects of microplastics on sludge removal performance, and on the physical and chemical properties and microbial communities in sludge, have attracted extensive attention. This review mainly describes the presence of microplastics in wastewater treatment plants, and the effects of microplastics on the decontamination efficiency and physicochemical properties of activated sludge, aerobic granular sludge, anaerobic granular sludge and anaerobic ammonium oxidation sludge. Further, the review summarizes the effects of microplastics on microbial activity and microbial community dynamics in various sludges in terms of type, concentration, and contact time. The mechanisms used to strengthen the reduction of microplastics, such as biochar and hydrochar, are also discussed. This review summarizes the mechanism by which microplastics influence the performance of different types of sludge, and proposes effective strategies to mitigate the inhibitive effect of microplastics on sludge and discusses removal technologies of microplastics in sewage. Biochar and hydrochar are one of the effective measures to overcome the inhibition of microplastics on sludge. Meanwhile, constructed wetland may be one of the important choice for the future removal of microplastics from sewage. The goal is to provide theoretical support and insights for ensuring the stable operation of wastewater treatment plants and reducing the impact of microplastics on the environment.

Effect of polyethylene terephthalate particles on filamentous bacteria involved in activated sludge bulking and improvement in sludge settleability

Excessive proliferation of filamentous bacteria within activated sludge leads to sludge structural instability and diminished settling properties, which is a prevalent issue in tannery wastewater treatment. Based on available information, there is a lack of research on the impact of particle addition on filamentous bacteria in activated sludge, specifically with respect to a reduction in sludge bulking. Therefore, polyethylene terephthalate (PET) was selected as the test material to elucidate the effect of particles on sludge bulking. The results illustrate that particles measuring 0.1 mm in diameter have a profound influence on both the quantity and morphological characteristics of filamentous bacteria in activated sludge. In an anaerobic-aoxic-oxic (AAO) reactor, the use of 4000 particles/L led to a significant decrease in the sludge volume index (SVI), reducing it from 358 mg/L to 198 mg/L. The results offer significant insights for resolving sludge bulking problems in tannery wastewaters. Moreover, the results are significant as a reference point for future investigations on the efficacy of incorporating diverse particulate materials to ameliorate issues associated with activated sludge bulking.

Microplastics and biobased polymers to combat plastics waste

Microplastics (MPs) have become the major global concern due to their adverse effects on the environment, human health, and hygiene. These complex molecules have numerous toxic impacts on human well-being. This review focuses on the methods for chemically quantifying and identifying MPs in real-time samples, as well as the detrimental effects resulting from exposure to them. Biopolymers offer promising solutions for reducing the environmental impact caused by persistent plastic pollution. The review also examines the significant progress achieved in the preparation and modification of various biobased polymers, including polylactic acid (PLA), poly(ε-caprolactone) (PCL), lignin-based polymers, poly-3-hydroxybutyrate (PHB), and poly(hydroxyalkanoates) (PHA), which hold promise for addressing the challenges associated with unplanned plastic waste disposal.

Effects of upward flow rate and modified biochar location on the performance and microecology of an anaerobic reactor treating kitchen waste

Increasing the value of food waste through anaerobic digestion is an attractive strategy. Meanwhile, the anaerobic digestion of kitchen waste also faces some technical challenges. In this study, four EGSB reactors were equipped with Fe-Mg-chitosan bagasse biochar at different locations, and the reflux pump flow rate was increased to change the upward flow rate of the reactor. The effects of adding modified biochar at different locations under different upward flow rate on the efficacy and microecology of anaerobic reactors treating kitchen waste were investigated. Results showed that Chloroflexi was the dominant microorganism when the modified biochar was added to the lower, middle, and upper parts of the reactor and mixed in the reactor, accounting for 54%, 56%, 58%, and 47%, respectively, on day 45. With the increased upward flow rate, the abundance of Bacteroidetes and Chloroflexi increased, while Proteobacteria and Firmicutes decreased. It was worth noting that the best COD removal effect was achieved when the anaerobic reactor upward flow rate was v2 = 0.6 m/h and the modified biochar was added in the upper part of the reactor, during which the average COD removal rate reached 96%. In addition, mixing modified biochar throughout the reactor while increasing the upward flow rate provided the greatest stimulus for the secretion of tryptophan and aromatic proteins in the sludge extracellular polymeric substances. The results provided a certain technical reference for improving the efficiency of anaerobic digestion of kitchen waste and scientific support for the application of modified biochar to the anaerobic digestion process.

A review on mechanistic understanding of microplastic pollution on the performance of anaerobic digestion

Anaerobic digestion (AD) has emerged as a promising technology for diverting the organic waste from the landfills along with the production of clean energy. AD is a microbial-driven biochemical process wherein the plethora of microbial communities participate in converting the putrescible organic matter into biogas. Nevertheless, the AD process is susceptible to the external environmental factors such as presence of physical (microplastics) and chemical (antibiotics, pesticides) pollutants. The microplastics (MPs) pollution has received recent attention due to the increasing plastic pollution in terrestrial ecosystems. This review was aimed for holistic assessment of impact of MPs pollution on AD process to develop efficient treatment technology. First, the possible pathways of MPs entry into the AD systems were critically evaluated. Further, the recent literature on the experimental studies pertaining to the impact of different types of MPs at different concentrations on the AD process was reviewed. In addition, several mechanisms such as direct exposure of MPs on the microbial cells, indirect impact of MPs through the leaching of toxic chemicals and reactive oxygen species (ROS) formation on AD process were elucidated. Besides, the risk possessed by the increase of antibiotic resistance genes (ARGs) after the AD process due to the MPs stress on microbial communities were discussed. Overall, this review deciphered the severity of MPs pollution on AD process at different levels.

Microplastics in Sewage Sludge: A review

Microplastics (MPs) represent a serious problem for the environment and for this reason they have been studied in many articles, especially their presence in aquatic environments and soils. MPs have been found in wastewater and sewage sludge from municipal wastewater treatment plants (WWTPs). Most part of the published works have focused on the detection and elimination of MPs in the water line and several reviews have been published in the last years. In addition, the application of sewage sludge produced from WWTPs for agricultural use is known to be a primary source of MPs in soils. However, in the scientific literature less attention has been paid to the sludge and little is known about MPs fate when it is applied in agriculture. This work aims to give a global revision on the most used techniques to identify and detect MPs in sludges, their characteristics and incidence, their effect on sludge treatments and their impact on the environment. As far as we know, there are no standardized protocols for MPs extraction from soil and the possible repercussions on the cultivation of plants are not known. This review evidences that more studies are necessary to stablished standardized protocols and decipher the main mechanisms and the effects of MPs from sewage sludge in the environment.

Effect of asparagine, corncob biochar and Fe(II) on anaerobic biological treatment under low temperature: Enhanced performance and microbial community dynamic

To ensure the efficiency of anaerobic biological treatment technology at lower temperature will expand the application of anaerobic reactor in practical industrial wastewater treatment. Through a batch experiment, asparagine, corncob biochar and Fe²⁺ were selected as strengthening measures to analyze the effects on the anaerobic sludge characteristics, microbial community and functional genes in the low temperature (15 °C). Results showed that after 21 days, asparagine began to promote chemical oxygen demand (COD) removal by the anaerobic treatment, with highest COD removal rate (81.65%) observed when the asparagine concentration was 1 mmol/L. When adding 3 g biochar, 25 mg/L Fe²⁺, and the combination of biochar and Fe²⁺, the COD removal rates reached to 82%, 92% and 97%, respectively. In the presence of asparagine, both biochar and Fe²⁺ alone or in combination increased the activity of protease (16.35%-120.71%) and coenzyme F₄₂₀ (5.63%-130.2%). The relative abundance of Proteobacteria and Methanobacterium increased in the presence of biochar and Fe²⁺. In addition, the KEGG results showed that the combined addition of biochar and Fe²⁺ enhanced bacterial replication and repair and promoted amino acid metabolism of archaea.

Levels of phthalates and bisphenol in toys from Brazilian markets: Migration rate into children's saliva and daily exposure

Bisphenols (BPs) and phthalate esters (PAEs) are extensively used in toys and childcare products. Therefore, children may be exposed to these compounds, causing potential adverse effects. Despite the strict control of the levels of these contaminants in toys by some nations, routine testing in Brazil is very scarce. The present study was aimed at determining the concentrations of PAEs and BPs in toys commercialized in Brazil, employing GC-MS and LC-MS/MS, respectively. Furthermore, the migration capacity of PAEs into saliva and the daily intake (EDI) were also estimated. Di-2-ethylhexyl phthalate (DEHP) was the PAE with the highest detection rate (93%) and migration rate (0.26 μg/min). Moreover, the levels of DEHP in some samples were above the threshold values set by the European Commission and the Brazilian Institute of Metrology, Standardization, and Industrial Quality. Among the BPs analogs, BPA and BPS presented the highest positive detection rates (72% and 30%, respectively). However, their levels were below the permitted values in all analyzed samples. A daily intake of DEHP was estimated at 29.8 μg/kg bw/day, being this exposure similar to those found in other countries and below the EFSA acceptable intake limit (50 μg/kg bw/day). However, our data are referred to exposure through oral contact with the analyzed toys, while the contribution of other potential sources, such as food consumption, were not here considered. To the best of our knowledge, this is the first study estimating the exposure of Brazilian children to PAEs and BPs, considering toys as the exposure source. These preliminary data may become a valuable guide for the control of EDC levels in toys commercialized in Brazil, as well as for future studies regarding estimation of exposure to EDCs by children taking into account multiple potential sources.

Current status of microplastics pollution in the aquatic environment, interaction with other pollutants, and effects on aquatic organisms

Microplastics, as emerging pollutants, have received great attention in the past few decades due to its adverse effects on the environment. Microplastics are ubiquitous in the atmosphere, soil, and water bodies, and mostly reported in aqueous environment. This paper summarizes the abundance and types of microplastics in different aqueous environments and discusses the interactions of microplastics with other contaminants such as polycyclic aromatic hydrocarbons (PAHs), polychlorinated biphenyls (PCBs), antibiotics, and heavy metals. The toxicity of microplastics to aquatic organisms and microorganisms is addressed. Particularly, the combined toxic effects of microplastics and other pollutants are discussed, demonstrating either synergetic or antagonistic effects. Future prospectives should be focused on the characterization of different types and shapes of microplastics, the standardization of microplastic units, exploring the interaction and toxicity of microplastics with other pollutants, and the degradation of microplastics, for a better understanding of the ecological risks of microplastics.

Performance and bacterial community profiles of sequencing batch reactors during long-term exposure to polyethylene terephthalate and polyethylene microplastics

Microplastics (MPs) are ubiquitous in wastewater treatment plants (WWTPs), but much remains to be learned about their roles in WWTPs. Herein, polyethylene terephthalate (PET) and polyethylene (PE) particles were added into sequencing batch reactors (SBRs), and the sole impacts and co-impacts of MPs with other pollutants (phenol and Cu²⁺) on wastewater treatment processes were evaluated. Results indicated that MPs did not significantly affect SBR performance, either alone or co-occurrence with phenol, but the co-exposure to MPs and Cu²⁺ severely suppressed COD removal efficiency by 37.02%-64.70%. The functional groups of activated sludge had no changes after receiving MPs, but the MPs-Cu²⁺ co-exposure could greatly promote the secretion of extracellular polymeric substances. Furthermore, MPs had no negative impacts on diversity, richness and structure of bacterial communities, and PET and PE showed different preferences for enrichment of bacterial populations. Moreover, the MPs-Cu²⁺ co-exposure obviously reduced the overall abundances of Cu-related genes in SBRs.

Evaluation of characteristics and microbial community of anaerobic granular sludge under microplastics and aromatic carboxylic acids exposure

The influences of polyether sulfone (PES) microplastics and different structures aromatic carboxylic acids such as benzoic acid (BA), phthalic acid (PA), hemimellitic acid (HA), and 1-naphthoic acid (1-NA) on the performances and characteristics of anaerobic granular sludge as well as the microbial community were investigated. The chemical oxygen demand (COD) removal efficiency was the highest in the experimental group with 40 mg/L BA, reaching 90.1%. The inhibitory effect of aromatic carboxylic acids addition on the 2,3,5-triphenyltetrazolium chloride (TTC) activity was more obvious than that on 2-para (iodo-phenyl)-3(nitrophenyl)-5(phenyl) tetrazolium chloride (INT) activity. Compared with the control group (only 0.5 g/L PES microplastics, 60.6 mg TF·g TSS·h^-1), the inhibition effect of TTC activity was 32.5 mg TF·g TSS·h^-1 and 44.3 mg TF·g TSS·h^-1 in the 40 mg/L HA and 40 mg/L 1-NA experimental groups, respectively. When aromatic carboxylic acids were added, the activities of acetate kinase and coenzyme F₄₂₀ in the anaerobic granular sludge decreased. The excitation-emission matrix (EEM) fluorescence spectra indicated that loosely bound extracellular polymeric substances (LB-EPS) began to decay. After the addition of different aromatic carboxylic acids, the CC and CH functional groups of the anaerobic granular sludge increased, suggesting that aromatic carboxylic acids migrated to the surface of anaerobic granular sludge, such a transfer would lead to changes in anaerobic granular sludge performance. High-throughput sequencing technology showed that the dominant microbial communities in the anaerobic granular sludge were Proteobacteria, Methanothrix, and Methanomicrobia. After the addition of aromatic carboxylic acids, the relative abundances of Proteobacteria, Methanobacterium, and Methanospirillum increased. In the presence of PES, 1-NA had the most serious toxicity to the anaerobic granular sludge.

How anammox responds to the emerging contaminants: Status and mechanisms

Numerous researches have been carried out to study the effects of emerging contaminants in wastewater, such as antibiotics, nanomaterials, heavy metals, and microplastics, on the anammox process. However, they are fragmented and difficult to provide a comprehensive understanding of their effects on reactor performance and the metabolic mechanisms in anammox bacteria. Therefore, this paper overviews the effects on anammox processes by the introduced emerging contaminants in the past years to fulfill such knowledge gaps that affect our perception of the inhibitory mechanisms and limit the optimization of the anammox process. In detail, their effects on anammox processes from the aspects of reactor performance, microbial community, antibiotic resistance genes (ARGs), and functional genes related to anammox and nitrogen transformation in anammox consortia are summarized. Furthermore, the metabolic mechanisms causing the cell death of anammox bacteria, such as induction of reactive oxygen species, limitation of substrates diffusion, and membrane binding are proposed. By offering this review, the remaining research gaps are identified, and the potential metabolic mechanisms in anammox consortia are highlighted.

Occurrence, effect, and fate of residual microplastics in anaerobic digestion of waste activated sludge: A state-of-the-art review

The plastic products have large consumption over last decades, resulting in a serious microplastics (MPs) pollution. Specially, the main removal way of MPs from wastewater is to transfer MPs from liquid to solid phase, leading to its enrichment in waste activated sludge (WAS). Anaerobic digestion has been served as the most potential technique to achieve both resource recovery and sludge reduction, herein this review provides current information on occurrence, effect, and fate of MPs in anaerobic digestion of WAS. The effects of MPs on WAS anaerobic digestion are greatly related to forms, particles sizes, contents, compositions and leachates of MPs. Also, the presence of MPs not only can change the effects of other pollutants on anaerobic digestion of WAS, but also can affect the fates of them. Besides, the future perspectives focused on the fate, effect and final removal of MPs during WAS anaerobic digestion process are outlined.

Occurrence, influence and removal strategies of mycotoxins, antibiotics and microplastics in anaerobic digestion treating food waste and co-digestive biosolids: A critical review

Food waste anaerobic digestion (FWAD) can be assisted with the co-digestion of manures, agricultural waste, and sewage sludge. Nevertheless, contaminants like mycotoxins, antibiotics, and microplastics (MPs) could be introduced and negatively affect the AD system. Over 180 literatures involved the occurrence, influence and removal strategies of these three types of pollutants in AD were summarized in this review. Aflatoxin B1(AFB1) as the most concerned mycotoxins were poorly degraded and brought about inhibitions in short-term. Considering methanogenesis inhibition and occurrence concentration, the risk of oxytetracycline and norfloxacin were identified as priority among antibiotics. Leaching toxic additives from MPs could be responsible for the AD inhibition, while their materials and sizes could also prolong the acidification and methanation processes in FWAD. Strategies of bioaugmentation technologies and bioreactors to enhance the removal were suggested. Perspectives were provided for a better understanding of the fates of reviewed contaminants and their elimination in FWAD systems.

Effect of microplastics in sludge impacts on the vermicomposting

To investigate the effect of microplastics (MPs) particles in vermicomposting, polyethylene (PE) particles added into sludge. Results showed that the vermicomposting with high MPs addition obtained lower removal efficiencies for organics than the vermicomposting with low MPs addition. The content of DOC and NH₄⁺-N in M₄ reactor (with the highest MPs addition) at 80 days was 8.4 mg/kg and 74.2 mg/kg, respectively. The pH, C/N, electrical conductivity (EC), and germination index (GI) results showed that the addition amount of MPs was directly proportional to the negative effect of composting. The negative effect mainly occurred after 20 days of composting. High MPs addition resulted in apparent oxidative stress and neurotoxicity on earthworm, the values of catalase (CAT) and acetylcholine esterase (AChE) in M₄ reactor increased by 2.03 times and 1.60 times. The bacteria in M₄ were more barren and lower in terms of diversity.