Novel hybrid electro-anaerobic digestion system for simultaneous antibiotics removal and bioenergy recovery

Informations projet

ElectroAD

N° de convention de subvention: 101103499

DOI

10.3030/101103499

Projet clôturé le 31 Juillet 2025

Date de signature de la CE 6 Avril 2023

Date de début 1 Août 2024

Date de fin 31 Juillet 2026

Financé au titre de

Marie Skłodowska-Curie Actions (MSCA)

Coût total

Aucune donnée

Contribution de l’UE

€ 199 694,40

Coordonné par

UNIVERSITY OF GALWAY
Ireland

Periodic Reporting for period 1 - ElectroAD (Novel hybrid electro-anaerobic digestion system for simultaneous antibiotics removal and bioenergy recovery)

Période du rapport: 2024-08-01 au 2026-07-31

Antibiotics are now recognised as pollutants of global concern. Their widespread use has led to residues in the environment that contribute to antimicrobial resistance (AMR), a major threat to public health and ecosystems. Wastewater treatment plants are hotspots for antibiotic residues and resistance genes, yet conventional anaerobic digestion—though widely used for organic waste treatment and renewable energy recovery—often fails to remove these contaminants. This creates a dual challenge: how to maintain environmental safety while producing clean energy.

The project set out to explore a new approach by combining electrochemical stimulation with conductive materials inside an anaerobic reactor. Granular activated carbon (GAC) was used to adsorb antibiotics and to facilitate microbial interactions, while a small electrical current was applied to encourage electroactive microorganisms. By integrating these strategies, the project aimed to enhance methane generation, reduce antibiotic residues, and provide new insights into microbial ecology. The broader ambition was to contribute to EU priorities on the circular economy, renewable energy, and zero pollution, while offering solutions aligned with the Green Deal and the European AMR Action Plan.

A laboratory-scale hybrid reactor (1.7 L) was designed and tested under four conditions: a control with no additions, a reactor with GAC, a reactor with low-voltage stimulation, and a combined GAC–electrode system. The reactor was operated in three phases to test both immediate and residual effects of the applied voltage.

The results revealed distinct outcomes. The low-voltage reactor consistently produced higher methane yields, showing that electrochemical stimulation can improve bioenergy recovery. The GAC reactor, however, was most effective in removing tetracycline, an environmentally relevant antibiotic, due to strong adsorption to the carbon surface. Surprisingly, the combined GAC–electrode system did not outperform the single-factor reactors; instead, it showed a trade-off, with higher energy recovery tending to reduce antibiotic removal and vice versa. This is the first experimental evidence of such an interaction, highlighting the need for further optimisation when combining technologies.

Microbial analysis provided further insights. The electrode system enriched electroactive bacteria such as Geobacter, which support direct electron transfer between microbes, while the GAC reactor encouraged fermentative and aromatic-degrading bacteria. These community shifts explained the different functional outcomes and pointed to new strategies for tailoring microbial ecosystems in treatment processes. In addition, chemical screening identified transformation products of tetracycline, with specific intermediates accumulating in the electrode zone. This finding demonstrates how reactor design can shape contaminant fate.

Overall, the project produced three important contributions: (1) proof-of-concept evidence that electrochemical stimulation can enhance methane generation in the presence of antibiotics; (2) confirmation that GAC remains superior for antibiotic removal; and (3) the first quantitative demonstration of a trade-off between energy recovery and contaminant control in hybrid systems. These findings provide scientific benchmarks for future designs of wastewater treatment technologies. The researcher attended one international workshop, one international forum, published one peer-reviewed open access article in npj Clean Water, and gave one presentation to academic audiences.

This project generated new experimental evidence on how conductive materials and gentle electrical stimulation can be combined in anaerobic digestion to both recover energy and reduce antibiotic pollution. Previous studies had looked at these approaches separately, but this work was the first to systematically compare them side by side and link their effects on performance, microbial communities, and contaminant fate using tetracycline as a model antibiotic.

From a process perspective, the study showed that applying a small electrical current can boost methane production, even in the presence of antibiotics, while activated carbon remains the most effective option for removing antibiotic residues. When both strategies were combined, the system revealed a trade-off: higher energy recovery tended to lower antibiotic removal and vice versa. This was the first clear evidence of such an interaction, challenging the idea that combining technologies always leads to better results. It provides practical guidance for future optimisation of wastewater treatment systems.

At a mechanistic level, the project clarified how antibiotics bind to activated carbon and how this capacity decreases over time with repeated use. It also mapped how tetracycline is transformed into intermediate compounds, with some by-products accumulating specifically in electrode regions. These findings demonstrate how reactor design can influence the environmental fate of contaminants. Microbial analysis further revealed that electrical stimulation enriches bacteria capable of direct electron transfer, such as Geobacter, while activated carbon supports fermentative and aromatic-degrading microbes. These insights expand our understanding of how materials and electrical fields reshape microbial ecosystems.

In addition to scientific results, the fellowship strengthened the researcher’s professional development. Through this project, the researcher acquired new skills in reactor design, electrochemical methods, microbial analysis, and interdisciplinary project management. The fellowship also expanded international networks and provided opportunities for dissemination through publications and workshops. These experiences enhanced employability and career prospects, equipping the researcher to pursue future roles in environmental biotechnology and to contribute to EU goals in renewable energy and pollution control.

Figure 9 TET concentrations in different reactor configurations across three operational stages.

Figure 3 Experimental design of the four reators

Figure 1 Challenge, strategy, and impact of the project

Figure 11 Relationships between methane production and tetracycline removal rates in control, GAC,

Figure 8 TET variations in different reactor configurations across three operational stages.

Figure 2 Proposed synergistic mechanisms of the hybrid electro-AD system

Figure 5 Methane yield in different reactor configurations across three operational stages.

Figure 13 Proposed TET degradation pathway

Figure 14 Heatmap of dominant genera and functional groups (electroactive, aromatic compound degrad

Figure 7 COD variations in different reactor configurations across three operational stages.

Figure 6 VFA variations in different reactor configurations across three operational stages.

Figure 10 Absorption of GAC and Electrode materials

Figure 12 Normalized signal intensities of tetracycline transformation intermediates in control, GA

Figure 4 Methane production profiles of hybrid anaerobic reactors across three operational stages.

Periodic Reporting for period 1 - ElectroAD (Novel hybrid electro-anaerobic digestion system for simultaneous antibiotics removal and bioenergy recovery)

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