Effect of black carbon on the migration and biodegradation of pentabromodiphenyl ether (BDE-99) during natural groundwater recharge with treated municipal wastewater Weifang Ma a, * , Yulin Yan a , Mengsi Ma b , Fangfang Su c , Yihan Zhang d a College of Environmental Science and Engineering, Beijing Forestry University, Beijing, 100083, China b China Water Environment Investment Limited Group, Beijing, 100071, China c Beijing Environmental Sanitation Engineering Group Co., Ltd., Beijing, 100063, China d Department of Civil and Environmental Engineering, University of Illinois at Urbana-Champaign, Urbana, IL, 61801-2352, USA article info Article history: Received 27 December 2015 Received in revised form 21 January 2016 Accepted 21 January 2016 Available online 3 February 2016 Keywords: BDE-99 Black carbon Adsorption Biodegradation Natural groundwater recharge Microbial community abstract When using treated municipal wastewater for recharging river-based natural groundwater, pentabro- modiphenyl 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 (Gammaproteo- bacteria, 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 sys- tem. The higher bacterial diversity and adsorption capacity in the BCA system were able mitigate the migration of BDE-99 into groundwater. © 2016 Elsevier Ltd. All rights reserved. 1. Introduction Most treated municipal wastewater is discharged into nearby rivers and thus naturally recharges the groundwater. River-based groundwater recharge using treated municipal wastewater is considered a promising method to alleviate groundwater depletion, especially in arid areas. In China, approximately 362.7  10 8 tons of treated municipal wastewater was discharged into the river in 2014, and nearly 3.75  10 8 t treated municipal wastewater was recharged through river utilization in Beijing (Ma et al., 2014). However, traditional wastewater treatment plants are inefficient at removing all types of contaminants (Calderon-Preciado et al., 2011; Matamoros and Salvado, 2012). Therefore, some not readily biodegradable organics pollutants, such as PBDEs, endocrine dis- rupting chemicals (EDCs), and pharmaceuticals, might pose a po- tential threat to underground aquifers. Among the organic contaminants, polybrominated diphenyl ethers (PBDEs) have become a focus of significant attention in recent years due to their persistence and ecotoxicity (UNEP, 2009). Wastewater treatment plants (WWTPs) are likely to receive significant amounts of PBDEs * Corresponding author. E-mail addresses: mpeggy@163.com (W. Ma), 1454864266@qq.com (Y. Yan), 351527262@qq.com (M. Ma), sff1224@126.com (F. Su), yzhan248@illinois.edu (Y. Zhang). Contents lists available at ScienceDirect International Biodeterioration & Biodegradation journal homepage: www.elsevier.com/locate/ibiod http://dx.doi.org/10.1016/j.ibiod.2016.01.016 0964-8305/© 2016 Elsevier Ltd. All rights reserved. International Biodeterioration & Biodegradation 113 (2016) 177e186