During her PhD studies, Yrsa Larsson investigated whether aerobic post-treatment with moving-bed biofilm reactors (MBBRs) could enhance the removal of antimicrobials from digested manure, which is a key pathway by which animal production contributes to the growing global threat of antimicrobial resistance.

The results show that aerobic MBBR treatment achieved 92% removal of a broad range of antibiotics and biocides, outperforming systems without biofilm carriers by 23%. High biocide concentrations in the digested manure confirmed the need for additional treatment steps. Degradation was not dependent on specific microorganisms, although microbial community composition influenced the metabolic pathway. Reductions in antimicrobial concentrations were associated with decreases in antibiotic resistance gene abundance, supporting the potential of aerobic MBBRs to reduce the spread of antimicrobial resistance from manure to the environment.

The PhD study was completed at Department of Environmental Science, Faculty of Technical Sciences, Aarhus University.

This summary was prepared by the PhD student.

Time: Tuesday, 26th May, 2026
Place: Building 112, H. H. Koch Auditorium, Lecture Theatre, Aarhus University, Frederiksborgvej 399, 4000 Roskilde
Title of PhD thesis: Degradation of Antimicrobials in Manure Using Aerobic Biofilm Post Treatment
Contact information: Yrsa Larsson, e-mail: yrsa@envs.au.dk, tel.: +45 55206322
Members of the assessment committee:
Professor Hans Chr. Bruun Hansen, PLEN, Copenhagen University, Denmark
Professor Ines Mulder, Soil Science, Geographical Institute, Ruhr University Bochum, Germany
Associate Professor Rumakanta Sapkota (chair), Department of Environmental Science, Aarhus University, Denmark
Main supervisor: Professor Kai Bester, Department of Environmental Science, Aarhus University, Denmark
Co-supervisor: Professor Henrik Bjarne Møller, Department of Biological and Chemical Engineering, Aarhus University, Denmark
Language: The PhD dissertation will be defended in English

The defence is public.
The PhD thesis is available for reading at the Graduate School of Technical Sciences/GSTS, Ny Munkegade 120, building 1521, 8000 Aarhus C.