MIL-88A(Fe) modified carriers induced iron autotrophic denitrification in intermittently-aerated MBBR for low C/N wastewater treatment

Abstract

Iron-assisted wastewater treatment has garnered significant attentions due to its promising potential for nitrogen removal under low carbon/nitrogen (C/N) ratios. However, the continuous addition of iron would result in unacceptably high operational cost. Herein, the iron mental-organic frame (MIL-88A(Fe)) modified sponge (MS) was developed as a source of continuous reactive iron sites and integrated in an intermittently-aerated moving bed biofilm reactor (MBBR) to enhance nitrogen removal efficiency under low (C/N) ratios. The results demonstrated that the MS-assisted system achieved stable total nitrogen removal of 76.2 ± 6.0% without adding additional iron and carbon sources when the C/N was 3.5 ± 0.3. After MS addition, the electron transport system activity increased from 8.2 ± 0.9 μgO₂/g/h to 12.7 ± 2.6 μgO₂/g/h, and the scanning electron microscope images revealed that the MS were covered with biofilm. Meanwhile, iron autotrophic bacteria (Thermomonas, Dechloromonas) and heterotrophic denitrifying bacteria (Candidatus_Competibacter) were enriched in the MS-assisted system, confirming the successful inducing of iron autotrophic denitrification process inside the reactor. This study revealed the effect of MS addition on microbial community succession and their pollutants removal characteristics, offering a feasible strategy for low C/N wastewater treatment.