Effects of poly (1,4-butanediol succinate) carrier on the nitrogen removal performance and microbial community of sequencing batch reactors

Abstract

The C/N ratio and carrier type strongly affect aerobic denitrification and are critical for nitrogen removal by sequencing batch reactor (SBR) processes. Poly (1,4-butanediol succinate) (1,4-PBS) is a biodegradable material that provides electrons to denitrifying microorganisms. The effect of carrier on the aerobic denitrifying microorganisms is worth further studying. In this study, aerobic denitrifying microorganisms were combined with 1,4-PBS to evaluate the effects of microbial biomass on the biodegradable carriers and nitrogen removal efficiency. High-throughput sequencing results indicated that after 45 days of the operation, the Shannon index of bacteria in the 1,4-PBS group increased from 4.48 (phase I, C/N = 5 at 1–8 days) to 5.74 (phase II, C/N = 10 at 9–20 days) and continuously increased to 6.68 in phase III (C/N = 20, 21–45 days). The peak total nitrogen (TN), NH4+-N and total organic carbon (TOC) removal efficiencies were 56.4%, 75.49% and 59.56% respectively at high C/N of 20. This result indicated that PBS significantly increased microbial diversity and indirectly changed the structure of microbial communities. Moreover, principal component analysis (PCA) showed that 1,4-PBS might change the microbial community. Specifically, 1,4-PBS might increase microbial diversity and indirectly change the structure of microbial communities. Meanwhile, the content of extracellular polymeric substances increased to 416.33 g g−1 VSS. 3D-EEM spectra showed that protein-like and humic acid-like substances were the main components in SMPs, and the fluorescence intensity increased in the initial 31 days and decreased in the following 14 days. Therefore, 1,4-PBS can efficiently improve the nitrogen removal performance of microbial communities. This study offers a reliable reference for the effects of biodegradable carriers on the nitrogen removal performance of microorganisms.