Biochar and activated carbon act as promising amendments for promoting the microbial debromination of tetrabromobisphenol A

Abstract

The increasing occurrence of tetrabromobisphenol A (TBBPA) in the environment is raising questions about its potential environmental health impacts as it has been shown to cause various deleterious effects in humans. The fact that the highest concentrations of TBBPA have been reported in wastewater sludge is concerning as effluent discharge and biosolids land application are likely a route by which TBBPA can be further disbursed to the environment. Our objectives in this study were to evaluate the effect of biochar (BC) and activated carbon (AC) in promoting the biodegradation of TBBPA, and characterize the response of anaerobic sludge microbial communities following amendments. Both carbonaceous amendments were found to promote the reductive debromination of TBBPA. Nearly complete transformation of TBBPA to BPA was observed in the amended reactors ~20 days earlier than in the control reactors. In particular, the transformation of diBBPA to monoBBPA, which appears to be the rate-limiting step, was accelerated in the presence of either amendment. Overall, microbial taxa responding to the amendments, i.e., ‘sensitive responders’, represented a small proportion of the community (i.e., 7.2%), and responded positively. However, although both amendments had a similar effect on TBBPA degradation, the taxonomic profile of the sensitive responders differed greatly from one amendment to the other. BC had a taxonomically broader and slightly more pronounced effect than AC. This work suggests that BC and AC show great potential to promote the biodegradation of TBBPA in anaerobic sludge, and their integration into wastewater treatment processes may be helpful for removing TBBPA and possibly other emerging hydrophobic contaminants.

Acetate promotes microbial reductive debromination of tetrabromobisphenol A during the startup phase of anaerobic wastewater sludge bioreactors

“…In the present study, by the end of the 133-day experiment, of the 51.5 μmol of TBBPA added (cumulative amount), 91.2±1.2 % and 86.3±2.2% had been transformed to BPA, in the metabolic and co-metabolic TBBPA-spiked reactors, respectively (Fig 1). Based on this observation, as well as the published results from two previous studies (Lefèvre et al, 2018;Lefevre et al, 2016), we concluded that microbial reductive debromination was the major process responsible for TBBPA transformation in our reactors. Unlike what was observed in our previous similar study in which acetate addition delayed the onset of TBBPA degradation by approximately two weeks (Lefevre et al, 2016), in the present study, TBBPA transformation started nearly immediately in both reactors with no acclimation period ( Fig.…”

“…Four bench scale anaerobic sludge reactors were assembled and operated as previously described (Lefèvre et al, 2018), and filled with 1.5 L of activated sludge (4.1±0.7 g/L of suspended solids) collected the same day at the North Durham WWTP (NC, US). The cometabolic set of reactors (i.e., reactor #1 and #2) received 1 g of sodium acetate trihydrate (5 mM final concentration), while the metabolic set (i.e., reactor #3 and #4) did not receive any additional source of carbon.…”

“…2.2.1 Illumina MiSeq sample preparation-Among the 54 samples processed for microbial DNA extraction, a subset of 36 triplicate samples collected on Days 0, 41, 55, 70, 88, and 111 from the TBBPA and control metabolic reactors were included in the Illumina MiSeq analysis. The Illumina library was prepared as previously described (Lefèvre et al, 2018). QIIME was used to analyze the Illumina MiSeq reads generated, and a workflow similar to the one previously described (Lefèvre et al, 2018) was followed.…”

“…The Illumina library was prepared as previously described (Lefèvre et al, 2018). QIIME was used to analyze the Illumina MiSeq reads generated, and a workflow similar to the one previously described (Lefèvre et al, 2018) was followed. Briefly, after read filtering, a total of 5,821,575 sequences were obtained.…”

“…Therefore, microbial community management strategies, whose underlying concept is to trigger a compositional shift towards a microbial community dominated by taxa with high degradative capabilities, are pertinent approaches to implement for improving in situ TBBPA biodegradation. Although bioaugmentation with TBBPAdegrading strains , biostimulation with various substrates, including carbonaceous charred amendments (Lefèvre et al, 2018), Fe-based particles (Peng et al, 2017a), carbon sources (Chang et al, 2012;Zu et al, 2014), and domestication of the indigenous microbial community (Peng et al, 2017b) have been shown to enhance TBBPA microbial degradation, in most cases a comprehensive characterization of the microbial communities involved has not been performed. As a result of the growing demand for consumer electronics, TBBPA concentrations are expected to increase in the near future, in particular in WWTPs.…”