Unraveling the molecular mechanisms of trace contaminant biotransformation from wastewater to natural surface waters

• Applicant: Michael Zimmermann, Ph.D.
• Subject Area: Hydrogeology, Hydrology, Limnology, Urban Water Management, Water Chemistry, Integrated Water Resources Management ; Microbial Ecology and Applied Microbiology
• Term: since 2021
• Project identifier: Deutsche Forschungsgemeinschaft (DFG) - Project number 460396841

Complex mixtures of trace organic contaminants resulting from human activity and released into the environment are a major ecological hazard. Activated sludge in wastewater treatment plants (WWTPs) acts as partial barrier to prevent contaminants from entering the environment, but treatment efficiency varies among compounds and treatment facilities. Although microbial biotransformation has the potential to remove contaminants from the environment, there is limited mechanistic understanding of the agents of contaminant biotransformation, i.e., microbial strains and enzymes. Furthermore, the impact of treated effluents on the functioning of downstream river biofilm communities remain anecdotal. The goal of the proposed project is to better understand trace contaminant biotransformation during wastewater treatment and in downstream environments at the level of microbial communities, strains, and enzymes, and to assess their influence on wastewater-impacted freshwater microbiomes. We hypothesize that community composition at the level of bacterial strains and genetic contents, and the chemical structure of trace contaminants are the two main factors driving biotransformation variability between microbial communities. As a consequence, we expect that bioindicators could be identified to explain biotransformation variability between microbial communities. To test this hypothesis, we propose the following four tangible objectives. First, we will perform a field experiment to systematically quantify the variability between WWTPs and their surrounding aqueous environment with respect to their microbial community composition and levels of organic contaminants. Second, we will assay the biotransformation capacity of the native microbial communities sampled during the field campaign as well as individual strains isolated from activated sludge. Third, we will combine bioinformatics, biochemical, and high-throughput genetic workflows to characterize known and identify new enzymes responsible for the biotransformation of trace organic contaminants in activated sludge. Forth, we will integrate our experimental results to identify bioindicators that explain biotransformation across natural and technical microbial communities. If successful, the gained molecular insights of this project have the potential to influence future engineering of WWTPs to optimize trace contaminant removal and minimize the impact on downstream environments, to aid the design of biodegradable chemicals, and to improve chemical risk assessment. Furthermore, the project will produce a number of resources including the first bacterial strain collection from activated sludge, extensive sets of biotransformation rates, and validated contaminant-transforming enzymes. These results will provide invaluable resources and a roadmap to propel future research aiming at a better understanding of biotransformation processes during wastewater treatment and in different natural environments.

• DFG Programme: Research Grants
• International Connection: Switzerland
• Cooperation Partner: Professorin Kathrin Fenner, Ph.D.