The overarching theme of the research performed in Environmental Engineering Science at Northwestern is focused on identifying and describing fundamental processes. This is achieved by making state of the art measurements to diagnose and predict the evolution of natural and engineered systems.

Research Examples

We have developed, in collaboration with Northwestern Synchrotron Research Center beam-line scientists, high resolution synchrotron-based X-ray computed microtomography (X-CMT) to identify the morphology of colloidal deposits formed in porous media. We have shown that difference microtomography - whereby a tomographic reconstruction is performed across an absorption edge - provides valuable information on the nature and location of the aggregates formed by the deposition of colloidal particles.

Another research goal has been to develop materials inspired by biological systems for environmental engineering applications. The specific project we are working on at present aims to develop a sustainable low energy membrane technology for treatment of impaired and contaminated water sources. Our hypothesis is that such a technology can be developed using practical membrane processes inspired by biological membranes. Biological systems conduct extremely efficient water filtration.

In modeling PCB bioaccumulation in Calumet Harbor, a highly altered ecosystem in Lake Michigan, Carla Ng discovered that its trophic structure and subsequent chemical transfer could not be captured without sufficient ecological resolution in three main areas: (1) ontogeny (changes in diet with age/size); (2) seasonality (e.g., the availability of fish eggs as a food source during spawning season); (3) trophic feedback loops (the recycling of nutrients and contaminants through consumption of detritus, e.g. mussel feces/pseudofeces and fish eggs). These properties create a complex, dynamic food web in an ecosystem that on the surface might seem simple, as it contains only a handful of species.

When a nanoparticle of TiO2 is illuminated with light of sufficient energy, an electron from the valence band is excited across the band gap to the conduction band, leaving a positively-charged hole behind. These charges may participate in redox reactions at the surface of the particle. Titanium dioxide photocatalysts have been demonstrated to perform a wide range of reactions, including the oxidation of organic pollutants. There are multiple crystallographic phases of titanium dioxide, most notably rutile and anatase. Rutile is excited by visible light, but has a fast charge recombination rate, leading to low efficiency. Anatase, however, is excited by near-UV light and has a slower rate of charge recombination, resulting in higher efficiency. Mixed phase catalysts with a high degree of rutile-anatase interfaces are highly efficient photocatalysts.

Massive coral bleaching episodes have been increasing for the past 30 years throughout the tropics; eight major bleaching events have been reported worldwide due to increase of the sea surface temperature. After a bleaching episode, most coral colonies bleach completely and die; however, certain coral colonies show resistance to bleaching and/or a remarkably fast recovery once the bleaching event subsides. We are particularly interested in studying the intrinsic properties of corals that lead to their differential reaction to bleaching and their varied recovery response.

Exchange between streams and the surrounding subsurface hyporheic zone plays a major role in the transport and fate of contaminants in watersheds.  The hyporheic zone is the region beneath the stream where stream water mixes with groundwater.  We are interested in the hydrodynamic processes that define the hyporheic zone, the resulting fluxes between streams and the subsurface, and the implications of these processes for sediment, contaminant, nutrient, and pathogen transport in streams.  Flow over a loose sediment bed produces a range of characteristic topographical features,  such as dunes, bars, and meanders, and flow interactions with these features induce hyporheic exchange flows.

Research Facilities:


Northwestern University houses many shared facilities that support our research activities.