Search

• Novel carbon source and corncob had better denitrification efficiency than polycaprolactone and polyvinyl alcohol-sodium alginate. • The taxonomical composition of bacterial, fungal and archaeal communities can be altered by types of solid carbon source. • Some fungi and archaea species were conducive to solid-phase denitrification (SPD) systems. • Co-occurring network showed some potential collaboration between bacterial fungal and archaeal communities in SPD systems. • Amplicon sequence variant (ASV) can identify more taxonomies that operational taxonomic unit (OTU) cannot in this study. There is a lack of understanding about the bacterial, fungal and archaeal communities' composition of solid-phase denitrification (SPD) systems. We investigated four SPD systems with different carbon sources by analyzing microbial gene sequences based on operational taxonomic unit (OTU) and amplicon sequence variant (ASV). The results showed that the corncob-polyvinyl alcohol sodium alginate-polycaprolactone (CPSP, 0.86±0.04 mg NO 3 −-N/(g·day)) and corncob (0.85±0.06 mg NO 3 −-N/(g·day)) had better denitrification efficiency than polycaprolactone (PCL, 0.29±0.11 mg NO 3 −-N/(g·day)) and polyvinyl alcohol-sodium alginate (PVA-SA, 0.24±0.07 mg NO 3 −-N/(g·day)). The bacterial, fungal and archaeal microbial composition was significantly different among carbon source types such as Proteobacteria in PCL (OTU: 83.72%, ASV: 82.49%) and Rozellomycota in PVA-SA (OTU: 71.99%, ASV: 81.30%). ASV methods can read more microbial units than that of OTU and exhibit higher alpha diversity and classify some species that had not been identified by OTU such as Nanoarchaeota phylum, unclassified_ f_ Xanthobacteraceae genus, etc., indicating ASV may be more conducive to understand SPD microbial communities. The co-occurring network showed some correlation between the bacteria fungi and archaea species, indicating different species may collaborate in SPD systems. Similar KEGG function prediction results were obtained in two bioinformatic methods generally and some fungi and archaea functions should not be ignored in SPD systems. These results may be beneficial for understanding microbial communities in SPD systems. [Display omitted] [ABSTRACT FROM AUTHOR]

MFC anodic denitrification is more suitable for the coexistence of organic matter and nitrate in actual sewage, but the traditional carbon source has some problems such as high cost and difficulty of dosage control in MFC. Herein, corncob and polycaprolactone (PCL) were mechanically pulverized and mixed in the system of polyvinyl alcohol and sodium alginate, and cross-linked to prepare slow-release carbon source fillers (CPSP), which were added to the MFC anolyte to realize the coupling of solid-phase denitrification and anodic denitrification. Results showed the start-up period of MFC experimental group (MFC-C) with CPSP was slightly longer than the control group (MFC-0), but MFC-C's maximum output voltage (648.4 mV) and power density (2738 mW/m3) could be increased by 5% and 15% higher than that of MFC-0 (P < 0.05). The degradation process of MFC substrate in unit cycle was mainly divided into nitrogen removal stage (0–8 h) and electricity generation stage (8–48 h). The NO 3 −-N and COD degradation and power generation kinetic processes of MFC conformed to the Han-Levenspiel model. Kinetics experiments showed CPSP can improve the affinity and tolerance of MFC to NO 3 −-N, also it can alleviate the pressure of electron competition in anolyte and improve coulombic efficiency. In addition, microbial communities were significantly changed under the effect of CPSP (P < 0.001). Meanwhile, CPSP can promote the synthesis of denitrification functional genes. This study provides a new strategy to improve the performance of MFC by the addition of novel denitrification carbon source. [Display omitted] • The addition of CPSP increased the power density of the anodic denitrification MFC. • The NO 3 −-N and COD degradation and power generation kinetic processes of MFC conformed to the Han-Levenspiel model. • Microbial communities in sludge and anodic biofilms were significantly changed by CPSP. • CPSP promoted the increase of denitrification gene in MFC anode suspended sludge. [ABSTRACT FROM AUTHOR]