Exploring antibiotic biotransformation in denitrifying wastewater treatment processes

• Autores: Silvana Inés Quiton Tapia
• Directores de la Tesis: Andreas Schäffer (dir. tes.), Francisco Omil Prieto (dir. tes.), Sonia Suárez Martínez (dir. tes.)
• Lectura: En la Universidade de Santiago de Compostela ( España ) en 2025
• Idioma: inglés
• Tribunal Calificador de la Tesis: Martina Roß Nickoll (presid.), Antón Taboada Santos (secret.), Mira Petrovic (voc.), Paola Verlicchi (voc.), Francisco Omil Prieto (voc.), Annika Jahnke (voc.)
• Programa de doctorado: Programa de Doctorado en Ingeniería Química y Ambiental por la Universidad de Santiago de Compostela
• Enlaces
  • Tesis en acceso abierto en: MINERVA
• Resumen

  • Biological nutrient treatment, primarily through activated sludge processes, is a core component of wastewater treatment plants WWTPs and the primary site for most biotransformation mechanisms. Although substantial research has focused on aerobic conditions, the mechanisms and efficiencies of micropollutant biodegradation under anoxic conditions specifically denitrification are far less understood. Denitrification, a key biological nutrient removal process, may offer a pathway for cometabolic antibiotic degradation. However, the relationships between operational parameters, microbial community composition, enzymatic activity, and micropollutant fate remain unclear. Understanding these complex interactions is critical for optimizing treatment processes, achieving compliance with increasingly stringent regulations, and mitigating the spread of antibiotic resistance.

    This doctoral research aims to bridge these knowledge gaps by investigating antibiotic biotransformation under denitrifying conditions. The work focuses on three main objectives 1 assessing cometabolic biotransformation by increasing denitrifying activity through higher substrate loading rates, 2 elucidating how microbial community shifts and enzymatic responses influence antibiotic biotransformation, and 3 understanding the fate and transformation pathways of antibiotics and their metabolites under heterotrophic and autotrophic denitrification systems.

    Using lab scale reactors, including conventional heterotrophic denitrification and the innovative N-Damo nitrite dependent anaerobic methane oxidation process, this study employs advanced techniques such as DNA metabarcoding, metaproteomics, and radiolabeled tracers. Results indicate that increasing denitrifying activity does not necessarily enhance antibiotic removal. Instead, microbial community structure and diversity are crucial, as beneficial antibiotic-degrading taxa can be outcompeted under high substrate loads. In autotrophic N-Damo systems, specific microbial and enzymatic pathways supported high nitrogen removal but did not consistently improve antibiotic degradation. Radiolabeled experiments revealed that antibiotic removal is highly dependent on chemical properties, with some compounds undergoing significant transformation while others persist. This complexity highlights the necessity of targeting specific microorganisms and enzymes for effective biotransformation.

    In conclusion, optimizing antibiotic removal in denitrifying systems requires managing microbial communities and targeting specific degradation pathways rather than merely increasing denitrification activity. Future research should focus on stimulating antibiotic degrading microbes and enhancing relevant enzymatic processes to develop more effective and sustainable wastewater treatment strategies.