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During groundwater recharge with reclaimed water, pentabromodiphenyl ether (BDE-99) might contaminate the underground aquifers. In order to understand the effects of elevated sulfate concentrations on the biodegradation of BDE-99, lab-scale column experiments were performed to study the changes in bacterial and archaeal communities. The results confirmed that the biodegradation rate of BDE-99 improved significantly with the addition of sulfate. Oxygen was replaced by sulfate as the predominant electron acceptor, and the major biodebromination metabolites of BDE-99 were BDE-28 and BDE-47, respectively, The results from 454 pyrosequencing of 16s rRNA genes showed that the microbial community structure shifted toward communities with BDE-99 co-metabolism ability. At the bacterial genus level, Geothrix , Thiobacillus , Sphingomonas , Paenibacillus and Desulforhabdus were the five most abundant genera, wherein, Thiobacillus was able to treat the toxic products generated during polybrominated diphenyl ethers (PBDE) biodegradation. In the case of archaea at the genus level, Methanobrevibacter , Methanomethylovorans , DHVEG-6, Candidatus Nitrososphaera and Methanosphaera were the predominant groups, of which Methanobrevibacter and Methanosphaera showed good ability to metabolize BDE-99 with sulfate amendment. [ABSTRACT FROM AUTHOR]

When groundwater is recharged with reclaimed water, the presence of trace amounts of biorefractory pentabromodiphenyl ether (PBDE, specifically BDE-99) might cause potential groundwater pollution. A laboratory-scale column was designed to investigate the distribution of the community of archaea in this scenario and the associated anaerobic degradation of BDE-99. The concentration of BDE-99 decreased significantly as soil depth increased, and fluorescence in situ hybridization (FISH) analysis suggested that archaea exerted significant effects on the biodegradation of PBDE. Through 454 pyrosequencing of 16s rRNA genes, we found that the distribution and structure of the archaeal community associated with anaerobic degradation of BDE-99 in the river-based aquifer media changed significantly between different soil depths. The primary debrominated metabolites varied with changes in the vertically distributed archaeal community. The archaea in the surface layer were dominated by Methanomethylovorans, and the middle layer was mainly composed of Nitrososphaera. Nitrosopumilus and Nitrososphaera were equally abundant in the bottom layer. In addition, Methanomethylovorans abundance depended on the depth of soil, and the relative abundance of Nitrosopumilus increased with increasing depth, which was associated with the oxidation-reduction potential and the content of intermediate metabolites. We propose that Nitrososphaera and Nitrosopumilus might be the key archaeal taxa mediating the biodegradation of BDE-99. [ABSTRACT FROM AUTHOR]

The use of tertiary-treated municipal wastewater for groundwater recharge through river utilization may cause pentabromodiphenyl ether (BDE-99) pollution, which poses a potential risk to groundwater aquifers. Elevated nitrate levels may change the structure of microbial communities, thus influencing the biodegradation of BDE-99. To investigate the influence of elevated nitrate levels on the changes in microbial communities and associated biodegradation of BDE-99 appropriately, a laboratory-scale column was designed to simulate the percolation process. The results showed that the attenuation rate of BDE-99 increased with nitrate concentrations. The lower-brominated ether congeners were the primary debrominated metabolites, while high-brominated diphenyl ethers and isomers of BDE-100 also emerged, and their concentrations decreased with reduced nitrate concentrations. The microbial community composition and structure significantly changed with elevated nitrate levels and relative abundance of nitrate-reducing bacteria with diverse metabolic capabilities increased. The order of the relative abundance of the largest five classes, as well as the relative abundances of the largest five families and genera, changed with increasing nitrate concentrations. The diversity of microorganisms with universal aromatics-degrading abilities related to nitrogen transformation played an important role in mitigating the infiltration of BDE-99 to groundwater. [ABSTRACT FROM AUTHOR]

Pentabromodiphenyl ether (BDE-99) pollution can affect groundwater that has been recharged with treated municipal wastewater. To properly investigate the effect of biochar on the anaerobic degradation of BDE-99 by an archaeal community, we established three lab-scale percolation columns to simulate the recharge process. BDE-99 content decreased with increasing soil depth, especially in the biochar-amended column (BCA), which demonstrated high adsorption capacity and biodegradability. The essential biodegradation of BDE-99 by archaea was confirmed during the recharge process by fluorescence in situ hybridization (FISH) analysis. The effect of biochar on the vertical distribution of typical archaea taxa associated with BDE-99 degradation in the river-based aquifer media was confirmed by 454 pyrosequencing the archaeal 16S ribosomal RNA (16S rRNA) genes. As well as affecting the concentration of polybrominated diphenyl ethers, biochar improved the biodiversity of the archaea and had a critical influence on the majority of archaeal communities. We observed large populations of Nitrosopumilus , Nitrososphaera , and Methanomethylovorans , which are associated with the anaerobic degradation of BDE-99, and the populations of some novel archaea genera, such as Halorhabdus and Methanospirillum , increased markedly owing to the effect of biochar. We suggest that biochar could play a positive role in the anaerobic degradation of BDE-99, and could provide a cost-effective means of mitigating the migration of pollutants. [ABSTRACT FROM AUTHOR]

When using treated municipal wastewater for recharging river-based natural groundwater, pentabromodiphenyl ether (BDE-99) pollution might be a potential threat to underground aquifers. Due to their strong affinity for black carbon (BC), the migration and bioavailability of PBDEs may be decreased in aquifer media with a high BC content. To properly examine the effect of black carbon on the migration and biodegradation of BDE-99, a lab-scale column was set up to simulate the recharge process. The filler media of the two columns mainly comprised silty clay (SC) and black carbon amendment silty clay (BCA). The results showed that the attenuation effect of BDE-99 was in the order of BCA > SC. The attenuation rate constants of BED-99 in the SC and BCA systems were 0.12 and 0.18 m − 1 , respectively, which followed first-order kinetics. The two turning points of the BDE-99 percentage with depth in the leachate were 0.15 m and 0.45 m due to fast sorption and biodegradation, respectively. The primary debrominated metabolites were not the only lower brominated ether congeners; high-brominated diphenyl ethers and isomers of BDE-99 were also produced during the biotransformation process. The accumulation of BDE-99 and PBDEs in the soil was higher in BCA soils than in the SC system. The bacterial community in the upper layer was more diverse than in the bottom layer. Five known bacterial classes ( Gammaproteobacteria, Alphaproteobacteria, Betaproteobacteria, Acidobacteria and Clostridia ) and seventeen known bacterial genera (three major genera: Halomonas, Pseudomonas and Shewanella ) were considered to be PBDE-degradation-associated bacteria. The bacterial community diversity and percentage of PBDE-degradation-associated bacteria in the BCA system were marginally greater than those in the SC system. The higher bacterial diversity and adsorption capacity in the BCA system were able mitigate the migration of BDE-99 into groundwater. [ABSTRACT FROM AUTHOR]