The main focus of my research activities always has been on the application of biological processes in water and wastewater treatment and their performance optimization. Starting in 1993 with my master project at the Centre International de Recherche sur l´Eau et l´Environnement in Paris, France, I studied the performance of Circulating Bed Biofilm Reactors (CBBR) in cooperation with Lyonnaise des Eaux. This work focused on the effects of oxygen and ammonium ion concentrations on the nitrification rate and included the development of a mathematical model and its application.

Subsequently I continued and enlarged this line of study in various projects, including my PhD-project, which focused on specific microbiological effects in bio-reactors: I studied the diversity, dynamics and performance of different nitrifying microbial species for various reactor operation parameters, both for biofilms and suspended microbial populations. The major part of this work was performed at the Technische Universität München at the Lehrstuhl für Mikrobiologie with support by the Lehrstuhl für Wassergüte- und Abfallwirtschaft. It involved molecular tools for the characterization and monitoring of microbial species, such as fluorescence in situ hybridization (FISH), polymerase chain reaction (PCR) and DNA sequencing. By confocal laser scanning microscopy (CLSM) and specific image-analysis-soft-ware I investigated the three-dimensional structures of microbial populations and their spatial distribution patterns. By extensive modeling with AQUASIM-software I succeeded in identifying the role of different metabolic interactions between the species involved.

Back at the Universidade do Minho as a permanent staff member of the Department of Bioengineering I started up a research group within the renowned Research Center of Biological Engineering (CEB) in 2003. In addition to biological water and wastewater treatment processes I enlarged my field of research towards hydrobiological aspects of water resource management issues: For different lake sediments my group succeeded in analyzing phosphorous mobility and subsequently developed a mathematical model, which the Regional Government of the Azores Islands utilized in the evaluation of possible intervention scenarios. Furthermore, we investigated hydrobiological metabolisation of humic acids in rivers by engineered biofilms as a pre-treatment for potable water production. Furthermore we are studying the utilization of bio-functionalized polymers as a support material for aqueous Biofilms in wastewater as well as in-situ groundwater treatment. In terms of general water resource management we carried out different studies on cost- and energy efficiency and evaluated life cycle assessments for conventional and sustainable water treatment processes.

In 2012 I got the Professorship for Water and Wastewater Biology at the Institute for Sanitary Engineering and Waste Management (ISAH) from the Gottfried Wilhelm Leibniz Universität Hannover. Since then I have been involved in lab- and full-scale projects dealing with biological treatment of wastewater with special focus on the detection and abatement of pathogenic microorganisms as for example legionella and viruses. We have been implementing molecular methods like FISH and real-time PCR for the detection of these microorganisms in wastewater in order to give a fast response to the wastewater operators of the efficacy of their measures.