Yongzhi Chen

Nitrate-dependent ferrous oxidation microorganisms (NDFOM) are a relatively newly discovered type of autotrophic denitrifying bacteria. In this study, FeSO ₄ solution was added to denitrifying sludge as a rapid starter for nitrate-dependent ferrous oxidation (NDFO). For the incubation process of NDFOM and the removal performance of nitrate nitrogen, three different models were employed. The experimental result confirmed a 95% NO ₃ ⁻ -N removal rate under steady conditions. The excellent fit (R ² = 0.9935) of the Boltzmann model to the kinetic data indicates that it precisely characterizes the nitrate-nitrogen (NO ₃ ⁻ -N) removal process mediated by NDFO. In conclusion, exploring the sludge acclimation process is crucial for the performance of iron autotrophic denitrification in removing nitrate nitrogen, thereby underscoring the potential of the NDFO process to be developed into a viable mainstream wastewater treatment technology.

This study investigated the performance of functional microorganisms during anaerobic fermentation and their effect on the degradation of cefadroxil under different pH conditions. The study mainly used microbial community analysis and metabolite assays, and the experiments were conducted under acidic (pH=4), neutral (pH=7) and alkaline (pH=10 and 12) conditions. The results showed that the abundance of functional microorganisms such as Caldilinea, Petrimonas, Ellin6067, Stenotrophobacter and Thauera increased significantly under alkaline conditions, especially at pH=10, where the total percentage of these microorganisms was close to 50%, suggesting that alkaline environments are more favorable for anaerobic fermentation of sludge. However, the microbial population structure was significantly reduced when pH was increased to 12, with only Petrimonas, Bacillus and Thauera as the main functional microorganisms, suggesting that the strongly alkaline conditions were unfavorable for the expression of functional microorganisms. In addition, the degradation of cefadroxil was mainly carried out through β-lactam ring hydrolysis, deamidation, demethylation, C-C bond breaking and 3,6-dihydro-2H-1,3-thiazine-4-carboxylic acid ring cleavage, and the degradation pathway was much simpler under alkaline conditions. In conclusion, alkaline conditions (especially pH=10) are more favorable for the growth of functional microorganisms and the degradation of cefadroxil.