Effect and microbial mechanism of pharmaceutical and personal care product exposure on partial nitrification process and nitrous oxide emission.

This study focused on the short- and long-term exposure of pharmaceutical and personal care products (PPCPs) to the partial nitrification process and nitrous oxide emission. The corresponding microbial mechanisms were also explored. The results revealed a concentration-dose effect on the partial nitrification process. Moreover, the PPCP concentration of ≥2 μg/L featured inhibitory effects on the process. The solo effect of PPCP on the partial nitrification process was analyzed through microcosmic experiments, and the results revealed significant variations in PN. A dose-effect relationship existed between the PPCP concentration and NO emission intensity. After exposure to PPCPs, the NO emission released during the partial nitrification process was significantly reduced. Different PPCPs featured various effects in mitigating NO emissions. Low PPCP concentrations led to a reduction in the richness and diversity of microbes, but their community structure remained significantly unchanged. High PPCP concentrations (≥5 μg/L) resulted in increased species richness and diversity, but their microbial community composition was significantly affected. The function prediction and nitrogen metabolic pathway analysis indicated that PPCP exposure led to the inhibition of the ammonia oxidation process. However, all genes encoding denitrification enzymes were upregulated. The microorganisms in the microbial community featured modular structural properties and wide synergistic relationships between genera. This study provides valuable insights into the effect of PPCP exposure on the particle nitrification process and corresponding changes in the microbial community.