Carbon fiber reinforced Fe0-mediated mixotrophic denitrification: Performance and potential mechanisms

Abstract

The denitrification efficiencies of two continuous flow mixed-culture denitrification reactors with Fe0 alone and carbon fiber reinforced Fe0 were compared by treating the synthetic wastewater containing NO3--N. The results showed that the average removal efficiencies of total nitrogen(TN) and NO3--N were as high as 89.04% and 97.13% for the experimental group R1 with carbon fiber and Fe0 injection at COD/NO3--N of 2.9-3.1 and hydraulic retention time(HRT) of 24 h, which were significantly higher than the control group R0 with Fe0 injection alone. The extracellular polymeric substances(EPS) and electron transfer activity(ETSA) variation patterns indicated that the input of carbon fiber further promoted the synthesis of EPS and enhanced the utilization of electrons by microorganisms. Scanning electron microscopy-energy dispersive spectrometry(SEM-EDS) and X-ray diffractometer(XRD) analyses revealed that there was obvious microbial corrosion on the surface of Fe0 in R1 reactor, and FeO(OH) and bioorganic-Fe complexes were the main corrosion products. Microbiological analysis showed that the increase of organic carbon source and the injection of carbon fiber effectively increased the abundance of iron autotrophic denitrifying bacteria genus and promoted the enrichment of denitrifying functional genes.

Keywords

• no3--n wastewater
• fe0
• carbon fiber
• mixotrophic denitrification
• cod/no3--n
• microbial community structure