Preparation of Self-Releasing Carbon Biofilm Carrier Based on Corncob and Denitrification Properties

Wastewater with a low carbon/nitrogen (C/N) ratio is widespread and difficult to treat. The addition of an external carbon source is an effective method for treating such wastewater. Therefore, we aimed to prepare a self-releasing carbon biofilm carrier using agricultural waste (corncobs), polyvinyl alcohol, and sponge iron in various ratios to provide a carbon source that would facilitate denitrification, providing an optimal environment for microorganisms. We found that the carbon release of the MAC biofilm carrier that accumulated over 60 d was 116.139 mg of chemical oxygen demand (COD)·g−1, whereas the accumulated total nitrogen release was approximately 0 mg·(g·d)−1. The NO3−-N removal rate after 24 h reached 98.1%, whereas the theoretical use rate of the carbon source (in terms of COD) was stable at 90.34%. In addition, the sum of the abundances of the denitrifying and cellulose-degrading bacteria was 49.89%. Furthermore, biofilm carriers are used as functional carriers that contribute to cellulose degradation, a process in which sponge iron produces Fe2+ to provide electron donors and shuttles for denitrifying bacteria and forms the iron cycle, thereby inducing an increase in microbial abundance; this increase then facilitates the microbial degradation of cellulose and synergistic denitrification through interspecific bacterial cooperation. This study provides a new and effective method for enhancing the denitrification of wastewater with low C/N ratios.