Effects of ciprofloxacin on biogas production and microbial community composition in anaerobic digestion of swine wastewater in ASBR type reactor

ABSTRACT

In swine farming, antibiotics are often used to reduce disease and promote animal growth. Part of these compounds is not absorbed by the swine body, being excreted and later reaching the treatment systems, soil, and nearby waterbodies. This research sought to investigate the influence of adding ciprofloxacin (CIP) on the anaerobic digestion of swine wastewater. For that, a bench-scale anaerobic sequential batch reactor (ASBR) was used, with 5 L of working volume in six different phases, with volumetric organic loading rate (VOLR) and CIP dosage variation. According to the results, the optimal VOLR for the reactor was 0.60 ± 0.11 gSV L⁻¹ d⁻¹, resulting in biogas productivity of 0.51 ± 0.03 L_biogas L⁻¹ d⁻¹. After initial stability, adding substrate with 0.5 mgCIP L⁻¹ resulted in an abrupt drop of 82% in the productivity from the 7^th to 11^th day of addition, coinciding with volatile acids accumulation. Afterward, the reactor recovered and reached apparent stability, with productivity similar to the previous step without the drug. For 2.5 mgCIP L⁻¹ in the substrate, the biogas productivity at equilibrium was 11.8% lower than in the phases with the same VOLR and 0.0 and 0.5 mgCIP L⁻¹. Organic matter removals near 80% were achieved for both dosages. The 16S rRNA metagenomic analyses showed an increase in the relative abundance of most of the phyla found, indicating that the dosages used allowed the acclimatization of microorganisms and possibly the compound biodegradation.

GRAPHICAL ABSTRACT

KEYWORDS:

• Methane
• drug
• micropollutant
• sequential batch
• antibiotic resistance

Acknowledgments

The authors thank The Federal University of Technology – Paraná (UTFPR) for the scholarships and resources granted; the company BIOTECNAL, for the substrate provided and analyzes performed; and CIBIOGÁS for the inoculum provided.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Data Availability Statement

The data that support the findings of this study are available from the corresponding author (J.G.V.S.R.) upon reasonable request.

Correction Statement

This article has been corrected with minor changes. These changes do not impact the academic content of the article.

Additional information

Funding

This work was supported by The Federal University of Technology – Paraná (UTFPR): [Grant Number: Announcement No. 001/2021 - DIREC/UTFPR-TD and Announcement No. 007/2021 - PROPPG/UTFPR].