An innovative bilayer solid carbon source for tertiary denitrification: Synthesis, performance, and microbial diversity analysis

Abstract

The low C/N ratio poses a constraint on the tertiary nitrogen removal process in domestic sewage. Composite solid carbon sources have recently gained attention in recent years for improving nitrogen removal efficacy. However, little research has focused on the lengthy start-up of denitrification systems caused by composite solid carbon sources. In this study, we employed a biodegradable sodium alginate (SA) and corn cob (CC) mixture, implanted a polycaprolactone (PCL) and corn starch (CS) mixture, and created a new composite solid carbon source polycaprolactone-corn starch‑sodium alginate-corn cob microspheres (PCSC). The early rapid carbon release and late stable carbon release properties of PCSC allow it to rapidly enrich denitrifying bacteria and form biofilms on its surface. It only takes 5 days to start denitrification biological filters utilizing PCSC as a carbon source, with an average nitrogen removal rate of 85 %, which is 60 % and 10 % higher than SA-CC and PCL-CS, respectively. The 16S rRNA gene high-throughput sequencing revealed that the primary denitrifying bacteria on the surface of PCSC were Chitinophagaceae, Comamonadaceae, and Blastocatellaceae. Overall, PCSC can make the denitrification system start up fast, steadily, and efficiently, and it has tremendous application prospects in tertiary nitrogen removal of wastewater.