ELARIA has demonstrated how antibiotic resistances, pathogens, and fecal indicators can be practically monitored and assessed in advanced treated wastewater.
Wastewater treatment plants (WWTPs) are designed to reduce the concentration of pollutants and prevent direct discharge of wastewater into rivers and oceans. However, conventional wastewater treatment is not sufficient to completely remove biological contaminants. Faecal microorganisms, including multidrug-resistant pathogens, antibiotic-resistant agents and enteric viruses, are released from WWTP effluent into surface water sources. Minimising the release of these biological contaminants is becoming increasingly important to improve the quality of surface water sources and safe water reuse.
The German–Israeli joint project ELARIA investigated how advanced wastewater treatment processes can reduce hygienically relevant microorganisms, antibiotic-resistant bacteria, antibiotic resistance genes, as well as viral and bacterial indicators. The aim was to generate robust data on the removal efficiency of different treatment approaches and to derive recommendations for practical monitoring and microbiological assessment.
To achieve this, studies at full-scale wastewater treatment plants were combined with laboratory and pilot-scale experiments, as well as pilot studies conducted in Israel. The processes examined included ozonation, UV and UV-LED irradiation, chlorination, and electrochemical treatment. The evaluation was based on an extended microbiological and molecular biological methodological spectrum. In addition to classical culture-based methods, quantitative PCR techniques were applied to detect both cultivable microorganisms and genetic markers.
A key practical focus was the question of the additional hygienic-microbiological effects provided by reactive advanced treatment processes. In practice, ozonation as a fourth treatment stage is primarily designed for the removal of organic micropollutants. Investigations at full-scale treatment plants showed that ozonation operated to achieve approximately 80% micropollutant removal can simultaneously reduce microbiological parameters. Depending on the target parameter and operational conditions, cultivable bacteria and bacteriophages were reduced by approximately 1 to 2 log₁₀ units. For selected antibiotic resistance genes, reductions of around 0.5 log₁₀ units were observed. These findings demonstrate that processes such as ozonation, UV treatment, or electrochemical treatment can contribute not only to the reduction of chemical contaminants but also to the mitigation of microbiological loads.
For more detailed analysis, Long-Amplicon PCR was additionally applied. In contrast to conventional PCR methods, which mainly amplify short target sequences, this approach allows the investigation of significantly longer nucleic acid fragments. This enables a more differentiated assessment of whether intact genes remain after treatment or whether structural damage has already occurred. The method therefore represents a valuable complement to classical qPCR analyses and provides additional insights, particularly for evaluating oxidative or disinfecting processes.
The results showed that short qPCR amplicons only partially reflect the actual extent of nucleic acid damage after advanced treatment. Long-Amplicon PCR proved to be a useful complementary approach for a more differentiated assessment of the effects of reactive treatment processes.
Based on the project results, approaches for a modular monitoring concept were developed. This concept can be adapted depending on the specific research question, wastewater treatment plant, and available treatment stages. It can support operators, authorities, and planners in evaluating treatment performance, selecting appropriate monitoring parameters, and presenting treatment results transparently.
Overall, ELARIA provides an important foundation for the future monitoring and assessment of treated wastewater. The project results support water protection efforts, the scientific evaluation of water reuse, and preparation for future requirements in wastewater monitoring in line with the new EU Urban Wastewater Treatment Directive.
Publications:
Nasser, A.; Eghbaria, Y.; Stange, C.; Tiehm, A. (2025): Combined disinfection processes for the reduction of microbial indicators and antibiotic resistance genes in wastewater effluents. Beitrag zur 22nd Health-Related Water Microbiology Conference (HRWM), Amersfoort, Niederlande, 15.–20. Juni 2025. Abstractband, mündlicher Vortrag (A. Nasser).
Ho, J.; Stange, C.; Diadko, D.; Eghbaria, Y.; Nasser, A.; Tiehm, A. (2025): Elimination of antibiotic resistance, pathogens and faecal indicators in advanced wastewater treatment. Beitrag zur 22nd Health-Related Water Microbiology Conference (HRWM), Amersfoort, Niederlande, 15.–20. Juni 2025. Abstractband, mündlicher Vortrag (A. Tiehm).
Stange, C.; Tiehm, A. (2025): Entfernung von Antibiotikaresistenzen, Pathogenen und Fäkalindikatoren bei der weitergehenden Abwasserbehandlung. Gewässerschutz – Wasser – Abwasser (GWA) 259, S. 22/1–22/15. Vortrag auf der Essener Tagung, März 2025 (A. Tiehm), sowie schriftliche Veröffentlichung im Abstractband.
Tiehm, A.; Stange, C.; Stelmaszyk, L.; Ho, J. (2025): Vorteile der Long-Amplicon-PCR beim Monitoring von Antibiotikaresistenzen. Mündlicher Vortrag (A. Tiehm) auf dem TZW-Workshop „Innovative Methoden in der Mikrobiologie“, 02.04.2025, Karlsruhe.
Ho, J.; Schweikart, C.; Tiehm, A. (2025): Abwasserwiederverwendung: Sicherung der mikrobiologischen Qualität. Beitrag zum 30. TZW-Kolloquium (hybrid): Mit Erfahrung Zukunft gestalten, 03.12.2025, Karlsruhe. Mündlicher Vortrag (J. Ho).
Stange, C.; Kalyetsi, R.; Owokuhaisa, J.; Ntaro, M.; Mulogo, E.; Nasser, A.; Tiehm, A. (2025): Wastewater surveillance of antimicrobial resistance and wastewater treatment efficiency in Mbarara, Uganda, and Karlsruhe, Germany. Posterbeitrag zum 10th Symposium on Antimicrobial Resistance in Animals and the Environment, Berlin, 30.06.–02.07.2025.
