Tetrabromobisphenol A (TBBPA) biodegradation in acidogenic systems: One step further on where and who

Visible light-induced photocatalytic degradation of tetrabromobisphenol A on platinized tungsten oxide

In this study, we investigated the degradation of the flame retardant tetrabromobisphenol A (TBBPA) using platinized tungsten oxide (Pt/WO3), synthesized via a simple photodeposition method, under visible light. The results of degradation experiments show a significant enhancement in TBBPA degradation upon surface platinization of WO3, with the degradation rate increasing by 13.4 times compared to bare WO3. The presence of Pt on the WO3 surface stores conduction band electrons, which facilitates the two-electron reduction of oxygen and enhances the production of valence band holes (hVB+) and hydroxyl radicals (●OH). Both hVB+ and ●OH are significantly involved in the degradation of TBBPA in the visible light-irradiated Pt/WO3 system. This was verified through fluorescence spectroscopy employing coumarin as a chemical probe and oxidizing species-quenching experiments. The analysis of degradation products and their toxicity assessment demonstrate that the toxicity of TBBPA-contaminated water is significantly reduced after Pt/WO3 photocatalysis. The degradation rate of TBBPA increased with increasing Pt/WO3 dosage, reached an optimum at a Pt content of 0.5 wt%, but decreased with increasing TBBPA concentration. The decrease in degradation efficiency of Pt/WO3 was minor, both in the presence of various anions and after repeated use. This study proposes that Pt/WO3 is a viable photocatalyst for the degradation of TBBPA in water under visible light.

Anaerobic treatment removing tetrabromobisphenol A and biota safety: How do tropical aquatic species respond to effluent toxicity over short- and long-term exposures?

Wastewater containing tetrabromobisphenol A (TBBPA), a commonly used flame retardant found in wastewater, can present significant toxic effects on biota, yet its impact on tropical freshwater environments is not well understood. This study explores the effectiveness of two independent anaerobic treatment systems, the acidogenic reactor (AR) and the methanogenic reactor (MR), for the ecotoxicity reduction of TBBPA-rich wastewater in four tropical freshwater species. Despite presenting good physicochemical performance and reduced toxicity of the influent for most species, AR and MR treatments remain acute and chronic toxicity. Overall, MR exhibited greater efficacy in reducing influent toxicity compared with AR. TBBPA bioaccumulation was observed in Chironomus sancticaroli after short-term exposure to 100% MR effluent. Multigenerational exposures highlighted changes in the wing length of C. sancticaroli, showing decreases after influent and AR exposures and increases after MR exposures. These findings underscore the need for ecotoxicological tools in studies of new treatment technologies, combining the removal of emerging contaminants with safeguarding aquatic biota. PRACTITIONER POINTS: Acidogenic and methanogenic reactors reduced the acute and chronic toxicity of wastewater containing tetrabromobisphenol A. Both treatments still exhibit toxicity, inducing short- and long-term toxic effects on four native tropical species. The aquatic species Pristina longiseta was most sensitive to effluents from acidogenic and methanogenic reactors. TBBPA concentrations recovered from Chironomus sancticaroli bioaccumulation analysis ranged from 1.07 to 1.35 μg g-1. Evaluating new treatment technologies with multiple species bioassays is essential for a comprehensive effluent toxicity assessment and ensuring aquatic safety.

Composition, Release, and Transformation of Earthworm Tissue-Bound Residues of Tetrabromobisphenol A in Soil

Earthworms accumulate organic pollutants to form earthworm tissue-bound residues (EBRs); however, the composition and fate of EBRs in soil remain largely unknown. Here, we investigated the fate of tetrabromobisphenol A (TBBPA)-derived EBRs in soil for 250 days using a 14C-radioactive isotope tracer and the geophagous earthworm Metaphire guillelmi. The EBRs of TBBPA in soil were rapidly transformed into nonextractable residues (NERs), mainly in the form of sequestered and ester-linked residues. After 250 days of incubation, 4.9% of the initially applied EBRs were mineralized and 69.3% were released to extractable residues containing TBBPA and its transformation products (TPs, generated mainly via debromination, O-methylation, and skeletal cleavage). Soil microbial activity and autolytic enzymes of earthworms jointly contributed to the release process. In their full-life period, the earthworms overall retained 24.1% TBBPA and its TPs in soil and thus prolonged the persistence of these pollutants. Our study explored, for the first time, the composition and fate of organic pollutant-derived EBRs in soil and indicated that the decomposition of earthworms may release pollutants and cause potential environmental risks of concern, which should be included in both environmental risk assessment and soil remediation using earthworms.

Recent advances in sulfidized nanoscale zero-valent iron materials for environmental remediation and challenges

Over the past decade, sulfidized nanoscale zero-valent iron (S-nZVI) has been developed as a promising tool for the remediation of contaminated soil, sediment, and water. Although most studies have focused on applying S-nZVI for clean-up purposes, there is still a lack of systematic summary and discussion from its synthesis, application, to toxicity assessment. This review firstly summarized and compared the properties of S-nZVI synthesized from one-step and two-step synthesis methods, and the modification protocols for obtaining better stability and reactivity. In the context of environmental remediation, this review outlined an update on the latest development of S-nZVI for removal of heavy metals, organic pollutants, antibiotic resistance genes (ARGs), and antibiotic resistant bacteria (ARB) and also discussed the underlying removal mechanisms. Environmental factors affecting the remediation performance of S-nZVI (e.g., humic acid, coexisting ions, S/Fe molar ratio, pH, and oxygen condition) were highlighted. Besides, the application potential of S-nZVI in advanced oxidation processes (AOP), especially in activating persulfate, was also evaluated. The toxicity impacts of S-nZVI on the environmental microorganism were described. Finally, the future challenges and remaining restrains to be resolved for better applicability of S-nZVI are also proposed. This review could provide guidance for the environmental remediation with S-nZVI-based technology from theoretical basis and practical perspectives.

Role of Gastrointestinal Microbiota from Crucian Carp in Microbial Transformation and Estrogenicity Modification of Novel Plastic Additives

Ingestion is a major exposure route for hydrophobic organic pollutants in fish, but the microbial transformation and estrogenic modification of the novel plastic additives by the gut microbiota of fish remain obscure. Using an in vitro approach, we provide evidence that structure-related transformation of various plastic additives by the gastric and intestinal (GI) microbiota from crucian carp, with the degradation ratio of bisphenols and triphenyl phosphate faster than those of brominated compounds. The degradation kinetics for these pollutants could be limited by oxygen and cometabolic substrates (i.e., glucose). The fish GI microbiota could utilize the vast majority of carbon sources in a Biolog EcoPlate, suggesting their high metabolic potential and ability to transform various organic compounds. Unique microorganisms associated with transformation of the plastic additives including genera of Citrobacter, Klebsiella, and some unclassified genera in Enterobacteriaceae were identified by combining high-throughput genetic analyses and metagenomic analyses. Through identification of anaerobic transformation products by high-resolution mass spectrometry, alkyl-cleavage was found the common transformation mechanism, and hydrolysis was the major pathway for ester-containing pollutants. After anaerobic incubation, the estrogenic activities of triphenyl phosphate and bisphenols A, F, and AF declined, whereas that of bisphenol AP increased.

Proteogenomics identification of TBBPA degraders in anaerobic bioreactor

Tetrabromobisphenol A (TBBPA) is the most used flame retardant worldwide and has become a threat to aquatic ecosystems. Previous research into the degradation of this micropollutant in anaerobic bioreactors has suggested several identities of putative TBBPA degraders. However, the organisms actively degrading TBBPA under in situ conditions have so far not been identified. Protein-stable isotope probing (protein-SIP) has become a cutting-edge technique in microbial ecology for enabling the link between identity and function under in situ conditions. Therefore, it was hypothesized that combining protein-based stable isotope probing with metagenomics could be used to identify and provide genomic insight into the TBBPA-degrading organisms. The identified ¹³C-labelled peptides were found to belong to organisms affiliated to Phytobacter, Clostridium, Sporolactobacillus, and Klebsilla genera. The functional classification of identified labelled peptides revealed that TBBPA is not only transformed by cometabolic reactions, but also assimilated into the biomass. By application of the proteogenomics with labelled micropollutants (protein-SIP) and metagenome-assembled genomes, it was possible to extend the current perspective of the diversity of TBBPA degraders in wastewater and predict putative TBBPA degradation pathways. The study provides a link to the active TBBPA degraders and which organisms to favor for optimized biodegradation.