Insights into the effect of carbamazepine on the anaerobic fermentation of waste activated sludge: Performance, mechanisms and regulation

The effects of pollutants on anaerobic fermentation of waste activated sludge (WAS) have been widely studied. Nevertheless, little attention was paid to how to mitigate the adverse effects of pollutants on anaerobic fermentation. In this work, representative pollutant carbamazepine (CBZ) was chosen to explore the potential effects of CBZ on WAS anaerobic fermentation. Experimental results showed that CBZ at environmental levels slightly promoted the production of short-chain fatty acids (SCFAs), which increased from 3858.2 to 4143.8 mg COD/L as the CBZ dose increased from 8 to 28 mg/kg VSS, but further increasing the CBZ dose to 88 mg/kg VSS decreased the production of SCFAs. Context of homologous group database revealed that the abundance of some functional traits changed, such as RNA processing and modification, energy production and conversion, and amino acid transport. This adverse effect was sustained because CBZ could not be degraded during anaerobic fermentation. Therefore, a regulation strategy was proposed, e.g., persulfate was used to attenuate the toxicity of CBZ to WAS anaerobic fermentation, and the results showed that the removal of CBZ reached 83.7 % in the persulfate-treated reactor. Based on density functional theory and metabolic intermediates determination, hy-droxylation and deamination reactions were the two main metabolic pathways for CBZ degradation.

Automated summary

This study explored the potential effects of the pollutant carbamazepine (CBZ) on anaerobic fermentation of waste activated sludge. The results showed that CBZ at environmental levels slightly promoted the production of short-chain fatty acids (SCFAs), but high doses of CBZ decreased the production of SCFAs. The abundance of certain functional traits changed during CBZ exposure, and the adverse effect was sustained due to CBZ being non-degradable during anaerobic fermentation. A regulation strategy using persulfate was proposed to mitigate the toxicity of CBZ, and it achieved a removal rate of 83.7%.