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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]

To investigate how biochar affects coupled migration-biodegradation of NP, a lab-scale column was set up to simulate the recharge process. The filler media of the two columns was mainly composed of silty clay (SC) and biochar amendment silty clay (BCSC). The results showed that the attenuation effect of NP in the BCSC system was 3.3% higher than that in the SC system. The attenuation rate constants of NP in the SC and BCSC systems were 0.20 and 0.24 m−1, respectively, which followed first-order kinetics. The two turning points of NP concentration with depth in the leachate were 0.15 and 0.45 m as a result of fast sorption and biodegradation, respectively. The primary metabolites were not the only hydroxylated 4-nonyl-4-hydroxycyclohexa-2,5-dienone and 4-hydroxyphenyl-nonanoic-acid; detached branched alkyl moieties were also produced during the biotransformation process. The accumulation of NP in the soil was higher in BCSC soils than in the SC system. The bacterial community in the upper layer was more diverse than in the bottom layer, which was related to oxygen concentrations in the water-soil system. Five known bacterial classes (Alphaproteobacteria,Betaproteobacteria,Gammaproteobacteria,Sphingobacteria, andBacilli) and 15 known bacterial genera (six major genera: Methylobacillus,Azotobacterium,Sphingomonas,Pseudomonas,Bacillus, andHyphomicrobium) were considered to be NP-degradation-associated bacteria. The bacterial community diversity and percentage of NP-degradation-associated bacteria in the BCSC system were marginally greater than those in the SC system. The higher bacterial diversity and adsorption capacity in the BCSC system were able to mitigate the migration of NP into groundwater. [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]