George Wells

Louis Berger Junior Professor of Civil and Environmental Engineering
McCormick School of Engineering and Applied Science
Northwestern University


Yubo Wang


Ph.D. (2017) The University of Hong Kong, Civil Engineering

My PhD program evolved around the anaerobic digestion bioprocesses. One of the scientific questions that fascinated me most was: the biochemistry and energy conservation involved in the anaerobes’ metabolism and how the intricate synergy may get established in the natural/engineered consortia. Complementary application of the molecular methods including the multi-omics approaches, the cultivation techniques and the ecological characterization may provide an unprecedented opportunity to uncover roles of some important functional microbes that are hiding in plain sight due to the cultivation bottlenecks. As a postdoc student in Wells’ group, I am now trying to expand my research areas from the anaerobic carbon cycle to the microbial nitrogen cycle. I will work with members in the group to explore the applicability of the mainstream Anammox bioprocesses; and will also focus on answering some fundamental research questions as the ecological niche of AOB/NOB/Comammox in the mainstream shortcut biological nitrogen removal processes (SCBNR).

Fabrizio Sabba


Ph.D. (2017) University of Notre Dame (USA), Civil and Environmental Engineering

Fab joined the Wells research group in 2018.  His research interests include biological processes for nutrients removal and resource recovery during water and wastewater treatment, with a focus on biofilm processes.  He obtained his Ph.D. in Environmental Engineering at the University of Notre Dame in 2017.  With funding from the Water Environment Research Foundation (WERF), he investigated nitrous oxide (N2O) emissions from biofilm systems by combining experimental and mathematical modeling approaches.  At Northwestern, Fab is involved with operation and maintenance strategies for biofilm reactors performing mainstream nitritation-anammox and other shortcut nitrogen removal bioprocesses for municipal water resource recovery facilities.  One important aspect of the performance of these reactors relies on their susceptibility to biomass loss and retention of slow-growing bacteria that could be linked to mesoscale biofilm structure and mechanical properties.  The intersection of mesoscale structure with mechanical properties applied to environmental biofilms aims to create a longer term strategy that leads to a structural health monitoring of biofilms with increased process stability and a cost/energy neutral wastewater treatment.


Graduate Students

Han Gao


Han Gao is a Ph.D. candidate in the Department of Civil and Environmental Engineering at Northwestern University. She holds a M.S. in Geography and Environmental Engineering from Johns Hopkins University, and B.S. in Environmental Science and Engineering from Tongji University. During her undergraduate study, Han was involved in research related to anaerobic digestion and algal cultivation. Her research interest is the field of resources and energy recovery from wastewater.

Jim Griffin


My research uses high throughput sequencing to investigate the complex microbial consortia in engineered and natural environments. I’m currently studying seasonal shifts in communities in Chicago’s Water Reclamation District using amplicon sequencing. I am developing new methods to improve our understanding of the environmental factors that lead to community stability and resilience and identifying triggers for and responses to disturbances is critical to designing efficient processes for nutrient removal.

Morgan Petrovich


My current research investigates spatial dynamics of antibiotic resistance and diversity in lab-scale wastewater treatment bioreactors. I have also used bioinformatics tools to analyze microbial community structure and genetic content within full-scale wastewater treatment facilities. This involved high-throughput metagenomics sequencing to track the abundance and fate of antibiotic resistance and production genes as well as mobile genetic elements such as plasmids and integrons throughout wastewater treatment systems. Some of my other past work has focused on characterization of dual and mixed-species biofilm structural parameters using data analysis of 3D image stacks obtained through confocal laser scanning microscopy (CLSM) and optical coherence tomography (OCT).

Paul Roots


My current project involves bench-scale testing of the application of anammox (anaerobic ammonium oxidizing) bacteria to mainstream municipal wastewater streams for nitrogen removal. Compared to conventional N removal methods, this process can save both energy via aeration reduction and organic carbon. Further work will investigate the operating conditions and growth structures that optimize anammox activity and biomass retention.


Alex Rosenthal


Alex joined the Wells research group in 2014 and is involved in multiple applied and fundamental research projects. His current project is an investigation of the interplay among mesoscale structure, mechanical properties, and emergent macroscale function in environmentally relevant biofilms. The long term goal of this project is to create a strategy for “structural health monitoring” of biofilm reactors that could be adopted by researchers and water resource recovery engineers to predict process stability. On the applied side, Alex is participating in studies to investigate the feasibility of (1) applying anaerobic ammonium oxidation in the mainstream of municipal water resource recovery facilities and (2) various fermentation technologies to recover waste organic carbon for beneficial use. Together, these projects help guide municipalities towards energy- and cost-neutral water resource recovery.