American Society of Agricultural and Biological Engineers

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Ampicillin, florfenicol, sulfamethazine, and tylosin effect on biogas production and their degradation efficiency during anaerobic digestion

Published by the American Society of Agricultural and Biological Engineers, St. Joseph, Michigan

Citation:  Paper number  131618717,  2013 Kansas City, Missouri, July 21 - July 24, 2013. (doi: @2013
Authors:   Shannon M Mitchell, Jeffrey L Ullman, Amy L Teel, Richard J Watts, Craig Frear
Keywords:   Anaerobic digestion antibiotic degradation biogas methane.

Abstract. Antibiotics enter the environment through municipal and agricultural waste streams since they are not completely metabolized in humans and animals. Non-metabolized antibiotics excreted maintain antimicrobial activity, which provides a human and ecological health concern from the risks of antibiotic-resistance promotion, changes in soil microbial ecologies, aquatic ecosystem effects, and leaching to groundwater. This study examined the impacts of four common animal husbandry antibiotics (ampicillin, florfenicol, sulfamethazine, and tylosin) on anaerobic digestion (AD) treatment efficiency and the potential for antibiotic degradation during digestion. Four antibiotics were analyzed for their biogas inhibition effects during biomethane production tests at 37°C using dairy manure solids as the substrate and municipal primary digested sludge as the inoculum. Antibiotic degradation rates were calculated, and the degradation products were identified and monitored throughout the 40 day AD process. Sulfamethazine and ampicillin exhibited no impact on total biogas production up to 280 and 350 mg/L, respectively, although ampicillin inhibited biogas production rates during early stages. Tylosin reduced biogas production by 10-40% between 171-920 mg/L. Florfenicol reduced biogas by ~5%, 40% and 80% at 6.7, 36 and 180 mg/L, respectively. These antibiotic concentrations are unusual for mixed feedlot manure, so impacts on AD should be minimal. Antibiotic degradation products were found, confirming AD effectively degraded ampicillin, florfenicol, and tylosin, although some products were persistent throughout the process. Contamination of digested solids and liquid streams with sulfamethazine and antibiotic transformation products from florfenicol and tylosin could present an environmental concern because they were not removed after 40 d of AD.

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