Our research focuses on understanding and solving problems related to the transport, fate, and cleanup of pollutants in groundwater, surface water, and soil. Our work is often interdisciplinary, and involves working at the interface of environmental engineering, microbiology, and geology, and geochemistry. As a result, it often involves collaboration with other faculty and students both in and outside the department. Our primary goal is to help identify and develop sustainable management and cleanup strategies for environmental pollutants based on a fundamental understanding of environmental processes. Pollutants of interest are legacy contaminants such as chlorinated solvents, polycyclic aromatic hydrocarbons, and nitrate, as well as emerging contaminants such as brominated flame retardants, pharmaceuticals, and perchlorate. Current areas of research include the following:
Mixing-Limited Remediation of Groundwater. In situ remediation technologies for groundwater such as bioremediation and chemical oxidation are often hindered by rates of mixing between an injected nutrient or reactant, and the contaminant of interest. The reason is that groundwater flow is laminar, and mixing is often controlled by transverse and longitudinal dispersion. We aim to understand the role of dispersive mixing on biological and chemical reactions in groundwater. In previous work, we identified the role of well-defined pore geometries on mixing-limited reactions. In current work, we are identifying the role of biomass growth on dispersive mixing and reaction rates at the pore scale via direct observation of the relevant processes in microfluidic pore networks. In collaboration with microbiologists, we are also evaluating the effect of rate-limited mixing on microbial growth and morphology, and rates of genetic adaptation to changes in substrate availability.
Microfluidic Pore Network Used for Investigating Reactive Transport and Biomass Growth
Model result of product formation along the transverse mixing line between two reactants in a model groundwater system
Mitigation of Pollutant Impacts in Urban Watersheds. Concentrations of polycyclic aromatic hydrocarbons (PAHs) have been increasing in recent decades in many urban lakes and streams, particularly in areas with rapid urbanization. Surface runoff of carbonaceous material (CM) particles is the most important pathway for the entry of PAHs into these fresh water sources. Efforts have been made to measure PAH concentrations in a variety of CMs to identify dominant sources; however, the types, amounts, and origins of PAH-associated CM particles in urban lake and stream sediments, and their relative contributions to PAH contamination remain unclear. In current work we are identifying the sources and distribution of CM particles in a small urban watershed, and PAH loadings on these particles. We recently found that CM particles associated with coal-tar sealcoats used on paved surfaces can dominate PAH loadings in urban lakes. We are exploring new best management strategies to capture these particles before they can impact urban water quality, including a new green roof on the Business Instructional Facility at the University of Illinois.
Image of core sampling of sediments at Lake Como
Fluorescent microscope image of soot obtained from the Lake Como watershed (soot is in black)
Development of Sustainable Catalytic Technologies for Drinking Water Treatment. Oxyanions such as nitrate and perchlorate are common contaminants in both surface and ground water. The accepted approach for removing them from drinking water is ion exchange. However, this produces a concentrated brine that requires further treatment or disposal. We are currently investigating sustainable catalytic technologies for reduction of oxyanion pollutants in drinking water. The three primary challenges of catalytic reduction technologies are faster kinetics, reduced fouling, and efficient regeneration. In previous work we identified palladium and indium as the optimal metals for nitrate reduction, due to their high activity and stability during oxidative regeneration. In current work, we are exploring the use of new reactive metal combinations, and novel catalyst supports, to address mitigate catalyst fouling. One approach we are taking is to load active metals inside carbon nanotubes to prevent fouling by reduced sulfur species.
TEM image of nanocolloidal palladium/copper catalysts.
Proposed perchlorate reduction pathway in the presence of hydrogen and a palladium/rhenium catalyst
In-Line Sensor Development for Water Pollutants. A large number of pollutants are present in natural waters, each often at concentrations below ppb levels. One example is 17-b-estradiol, an endocrine disrupting compound. In current work we are developing a sensor for this analyte by coupling the in-line mixing and separation capabilities of microfluidics, with highly specific binding of DNA-aptamers attached to magnetic beads. The microfluidic devices allow the magnetic-bead bound aptamers to be efficiently mixed with sample water containing the analyte of interest, and for the analyte-aptamer-bead complex to be concentrated in a magnetic field for enhanced sensitivity. The DNA-aptamer allows for highly specific binding to the analyte, and for fluorescent signaling when bound to the analyte. The development of in-line sensors is crucial for monitoring the performance of water treatment processes, providing clean, safe water, and ensuring public confidence in water supplies.
Reflected differential interference microscope image of an in-line microfluidic mixer fabricated from an etched silicon substrate
Illustration of a fluorescence-signaling DNA-aptamer attached to a magnetic bead