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

Abstract

The detection of increasing concentrations of tetrabromobisphenol A (TBBPA) in wastewater treatment plants is raising concerns as TBBPA has been identified as a potentially toxic flame retardant. The objectives of this study were to evaluate the effect of acetate biostimulation on TBBPA microbial reductive debromination, and the response of anaerobic sludge associated microbial communities repeatedly exposed to TBBPA. Results indicate that the bulk of the microbial community did not experience significant shifts as a result of TBBPA exposure, and that only a small fraction of the community responded to the presence of TBBPA. Taxa most likely responsible for TBBPA transformation affiliated to Clostridiales and the wastewater sludge group Blvii28. The biostimulating effect of acetate was only observed during reactor startup, when acetogenesis was likely not yet occurring. However, when acetate likely started to be microbially generated in the reactor, acetate addition resulted in a slight but significant inhibiting effect on TBBPA transformation. A significant increase of hydrogenotrophic methanogens in the TBBPAspiked reactor overtime implies that TBBPA degraders were not in direct competition with methanogens for H2. These results strongly suggest that TBBPA degrading taxa might have been primarily using acetate as an electron donor for the reductive debromination of TBBPA.

Anti-Biofouling Performance of an Immobilized Indigenous Quorum Quenching Bacterium Bacillus cereus HG10 and Its Influence on the Microbial Community in a Bioreactor

“…Among the genera that were downregulated, Blvii28_wastewater-sludge_group has been commonly found in wastewater or wastewater treatment systems [38,39]. Researchers have indicated that this genus functions in the initial attachment during the biofilm forming process.…”

Insights into the Occurrence, Fate, and Impacts of Halogenated Flame Retardants in Municipal Wastewater Treatment Plants

“…The richness of wastewater sludge microbiomes and diversity of niches in WWTPs provide a number of different possible pathways for HFRs biotransformation in wastewater treatment systems and anaerobic digesters. Indeed, biotransformation of HFRs in wastewater sludge has been investigated at lab-, pilot-, and full-scale in numerous studies. ,,,− Additionally, efforts have been made to enrich, isolate and characterize the functional HFR-transforming microorganisms in wastewater sludge. − Aerobic biotransformation of HFRs in WWTPs usually occurs via oxidative transformation during aerobic treatment processes (Table ). Kim and Oh evaluated the mass balance of PBDEs in a full-scale WWTP in South Korea and concluded that a 40% mass loss of PBDEs was most likely caused by oxidative biotransformation mediated by the activated sludge microbiome; this conclusion was based on the formation of hydroxylated and methoxylated PBDEs during aerobic biological wastewater treatment .…”

“…In early laboratory studies, approximately 99% of TBBPA was anaerobically biotransformed by the digester sludge microbiome within 3 days . Similarly, a continuously operated anaerobic reactor inoculated with activated sludge completely debrominated >95% of TBBPA to BPA in 5 days . However, BPA is more toxic than TBBPA, and subsequent biotransformation processes that detoxify BPA are not always occurring in anaerobic reactors.…”

“…In addition to laboratory studies, efficient anaerobic TBBPA biotransformation (∼80% of TBBPA in the influent) has also been observed in a full-scale sludge anaerobic digester operating at a SRT of 28 days . Thus far, limited information is available about the microbial community in TBBPA biotransforming anaerobic sludge . Studies investigating the phylogeny of TBBPA debrominating bacteria showed that Comamonas , Achromobacter , Flavobacterium , and Pseudomonas dominated one TBBPA-debrominating anaerobic sludge reactor, while a separate study concluded that OTUs affiliated to Clostridiales and Blvii 28 debrominated TBBPA to BPA in an enrichment culture .…”

“…Anaerobic digestion is a promising approach to simultaneously eliminate the harms of and harvest the bioenergy from wastewater treatment solids, including primary sludge and WAS. ,, The general steps for anaerobic digestion of wastewater treatment solids include solubilization, hydrolysis, acidogenesis, and methanogenesis . Efficient anaerobic digestion depends on the collaboration of various functional groups of microorganisms. ,, Exposure to HFRs and associated transformation products can lead to inhibitory or stimulatory effects on different steps of anaerobic digestion and the final impact on anaerobic digestion performance is determined by a trade-off between the enhanced and inhibited steps. , For example, one study showed that exposure to TBBPA in anaerobic sludge reactors significantly increased the quantity of both mcr A and methanogens in the reactor, indicating potential for higher methane production . Patel et al evaluated the toxicity of phenol and benzoate, common degradation products of HFRs, on various methanogens after short-term exposure, finding that the extent of inhibition was determined by the types and concentrations of pollutants and the microbial species inhibited .…”