Tetrabromobisphenol A Affects Acetic Acid Production during Anaerobic Fermentation of Sewage Sludge

Recycling resources from human-derived waste streams is essential for sustainable development, with sewage sludge offering potential for the biological production of short-chain fatty acids (SCFAs). However, the impact of emerging contaminants on SCFA-producing processes remains poorly understood. In this study, we employed laboratory fermentation microcosms to investigate the effects of tetrabromobisphenol A (TBBPA) on SCFA-producing bioprocesses and the underlying mechanisms. Our results revealed that TBBPA at concentrations ranging from 0.5 to 5.0 mg/kg TS significantly increased the accumulation of SCFAs. However, there was no significant difference in the increments of SCFAs between fermenters containing low (0.5 mg/kg TS) and high (5 mg/kg TS) levels of TBBPA. The yield of acetic acid, which was the predominant SCFA in fermenters with a TBBPA concentration of 5 mg/kg TS, was 1.3 times higher than that in the control group. Mechanistic investigations demonstrated that TBBPA promoted substrate hydrolysis, particularly carbohydrates, due to differential interactions with organic matter. TBBPA also increased ATP levels, electron transport system (ETS) activity, and extracellular polymeric substance (EPS) secretion in enriched acidogenic and acetogenic communities, thereby enhancing microbial viability and metabolic activity. Microbial community analysis showed increased abundances of key SCFA-producing bacteria, particularly acetogens, alongside potential TBBPA degraders. Overall, this study reveals that TBBPA, despite being an environmental pollutant, can unexpectedly stimulate anaerobic fermentation via microbial adaptation and activity enhancement, offering a novel and sustainable perspective for optimizing sludge treatment and resource recovery.