Carbamazepine biodegradation and volatile fatty acids production by selectively enriched sulfate-reducing bacteria and fermentative acidogenic bacteria

BACKGROUND: The micropollutant carbamazepine (CBZ) is persistent and resistant to conventional wastewater treatment. This study investigated the role of fermentative acidogenic bacteria (FAB) and sulfate-reducing bacteria (SRB) for CBZ biodegradation and volatile fatty acid (VFA) production. RESULTS: The experimental results demonstrated that CBZ biodegradation, total organic carbon and sulfate removal efficiency reached 46%, 36% and 98%, respectively, after 144 h of operation with VFA production of acetic acid (20.72 mmol L⁻¹), propionic acid (3.67 mmol L⁻¹) and butyric acid (4.90 mmol L⁻¹). However, the acetate fraction decreased from 78% to 70% with a decrease in chemical oxygen demand/sulfate (COD:SO₄²⁻) ratios from 1.06 to 0.35, respectively, suggesting that acetate was partially oxidized by SRB under substrate/COD limiting conditions. The biodegradation performance of SRB + FAB was also compared with that of a mixed microbial community (MMC). CONCLUSIONS: Upon increasing the initial CBZ concentration from 42.3 to 169.2 μmol L⁻¹, SRB + FAB exhibited much higher CBZ biodegradation (33%) than MMC (12%). Microbial community analyses confirmed the enrichment of VFA-producing species including phylum Firmicutes (2.4% to 36.8%) and class Clostridia (1.3% to 29.6%). Moreover, aromatic and nitroaromatic compound-degrading bacteria such as Escherichia and Desulfovibrio were also enriched. This signifies the applicability of SRB + FAB to pharmaceutical pollutant biodegradation in the environment.