Evolution of Microbial Community Structure and Denitrifying Functional Microorganisms in the Biological Sponge Iron System

With the growing problem of global water pollution, nitrogen pollution has become a key factor affecting aquatic ecosystems and human health. The biological sponge iron system (BSIS) has gained attention as a research hotspot due to its efficient denitrification capability. This study focused on the changes in microbial community structure and the relative abundance and interrelationships of nitrogen cycle-related functional bacteria at different operational stages of the BSIS with a sponge iron (SFe) dosage of 90 g/L. The results showed that as the operation time of the reactor extended, the relative abundance of denitrifying genera such as Saccharimonadales, Arenimonas, and Acinetobacter significantly increased, while the relative abundance of Proteobacteria showed a trend of initial increase followed by a decrease. The relative abundance of nitrifying bacteria exhibited a more complex variation, whereas the abundance of denitrifying bacteria showed a continuous upward trend. In addition, there were complex interrelationships among different denitrifying bacteria, such as a positive correlation between Saccharimonadales and Acetobacteraceae, and a negative correlation between Rhodothermus and Pseudoxanthomonas. This study not only revealed the changes in the relative abundance and interrelationships of microbial communities and nitrogen cycle-related functional bacteria over time with an SFe dosage of 90 g/L, but also provided a new perspective for understanding the intrinsic mechanism of enhanced biological denitrification by sponge iron. These findings are of great significance for optimizing the operating parameters of the BSIS, improving denitrification efficiency, and promoting the practical application of this technology in the field of environmental engineering.