Effects of nanoparticles on the anaerobic digestion properties of sulfamethoxazole-containing chicken manure and analysis of bio-enzymes

Abstract

Abstract Medium-temperature anaerobic digestion experiments lasting for 55 days were conducted using sulfamethoxazole (SMX)-containing chicken manure in sequential batch reactors added with nano-Fe2O3 at a concentration of 300 mg·kg−1·TS or nano-C60 at a concentration of 100 mg·kg−1·TS. The effects of nanoparticles on the anaerobic digestion properties of SMX-containing chicken manure were assessed by measuring the following indicators: biogas production by anaerobic digestion, chemical parameters, enzyme concentrations, and bacterial diversity and changes in antibiotic concentrations over time. The law of bacterial degradation of SMX was analyzed. The results showed that (1) adding either nano-Fe2O3 or nano-C60 promoted biogas production by anaerobic production from chicken manure containing different concentrations of SMX, and the cumulative biogas production in Fe2O3 and nano-C60 increased by 35.4% and 130.7%, respectively. The final cumulative biogas productions in different groups were as follows: 3,712(CK), 4,281(S1), 3,968(S2), 4,061(S3), 4,498(S4), and 4,639(S5) mL and the final concentration of SMX residues varied between 99.79% and 99.94%; (2) Bacterial abundance at the phylum level: on day 1, Firmicutes and Bacteroidota were the main dominant bacterial phyla, with relative abundances of 45.13–68.53% and 26.12–48.32%, respectively. The addition of nanoparticles increased the abundance of Bacteroidota in S4 and S5 significantly. The abundance of Bacteroidota was slightly higher in the group added with nanoparticles than in S2. On day 50, Firmicutes became the dominant bacterial phylum, and its relative abundance varied little across the groups, ranging from 90.87% to 94.54%; (3) At different stages, the bacterial community structure at the genus level was dramatically affected by substrates. As nutrients were being depleted, some bacterial communities lost their original competitive advantages. On day 5, the relative abundance of Prevotella increased. Especially, the relative abundances of Prevotella in S4 and S5 added with nanoparticles were lower than that in S2 by 8–10%. On day 15, the relative abundance of Prevotella in S2 decreased compared with the control group CK. A decrease was also observed in S4 and S5, although to a smaller extent than in S2.