Initial carbon release characteristics, mechanisms and denitrification performance of a novel slow release carbon source

Abstract

External carbon source addition is one of the effective methods for the treatment of wastewater with low carbon to nitrogen ratio (C/N). Compared with fast-release liquid carbon sources, slow-release solid carbon sources are more suitable for the denitrification process. A novel slow-release solid carbon source (corncob-polyvinyl alcohol sodium alginate- poly-caprolactone, i.e. CPSP) was prepared using corn cob (CC) and poly-caprolactone with polyvinyl alcohol sodium alginate as hybrid scaffold. The physical properties and carbon release characteristics of CPSP and three other carbon sources were compared. CPSP had stable framework and good carbon release performance, which followed the second order release equation. The formic acid, acetic acid, propionic acid and butyric acid released from CPSP accounted for 8.27% ± 1.66 %, 56.48% ± 3.71 %, 18.46% ± 2.69% and 16.79% ± 3.02% of the total released acids respectively. The start-up period of CPSP was shorter than that of the other carbon sources in denitrification experiment, and no COD pollution was observed in the start-up phase (25-72 h) and stable phase (73-240 hr). The composition and structure of the dissolved organic compounds released by CPSP and other carbon sources were analyzed by UV-Vis absorption spectroscopy and three-dimensional fluorescence spectroscopy, which indicated that CPSP was more suitable for denitrification than the other studied carbon sources.

Keywords: Carbon release characteristics; Corn cob; Denitrification; Dissolved organic matter; Novel slow-release carbon source.