How halogenated aromatic compounds affect the electron supply and consumption in glucose supported denitrification?

Abstract

Halogenated aromatic compounds possess bidirectional effects on denitrifying bio-electron behavior, providing electrons and potentially interfering with electron consumption. This study selected the typical 4-chlorophenol (4-CP, 0–100 mg/L) to explore its impact mechanism on glucose-supported denitrification. When COD(glucose)/COD(4-CP)=28.70–3.59, glucose metabolism remained the dominant electron supply process, although its removal efficiency decreased to 73.84–49.66 %. When COD(glucose)/COD(4-CP)=2.39–1.43, 4-CP changed microbial carbon metabolism priority by inhibiting the abundance of glucose metabolizing enzymes, gradually replacing glucose as the dominant electron donor. Moreover, 5–100 mg/L 4-CP reduced adenosine triphosphate (ATP) by 15.52–24.67 % and increased reactive oxygen species (ROS) by 31.13–63.47 %, causing severe lipid peroxidation, thus inhibiting the utilization efficiency of glucose. Activated by glucose, 4-CP dechlorination had stronger electron consumption ability than NO2−-N reduction (NO3−-N > 4-CP > NO2−-N), combined with the decreased nirS and nirK genes abundance, resulting in NO2−-N accumulation. Compared with the blank group (0 mg/L 4-CP), 5–40 mg/L and 60–100 mg/L 4-CP reduced the secretion of cytochrome c and flavin adenine dinucleotides (FAD), respectively, further decreasing the electron transfer activity of denitrification system. Micropruina, a genus that participated in denitrification based on glucose, was gradually replaced by Candidatus_Microthrix, a genus that possessed 4-CP degradation and denitrification functions after introducing 60–100 mg/L 4-CP.