| Research Projects |
The use of geomembranes comprised of polymers (such as high density polyethylene; HDPE) to contain or stabilize contamination is based on drastically slowing the diffusion of contaminants into uncontaminated areas by creating a barrier using the membrane material. Diffusion through the membrane barrier is slow, but contaminants will eventually break through. The time to breakthrough can be increased and the diffusion process itself can be slowed through the use of reactive membrane barriers. Reactive particles serve to either immobilize or transform contaminants within the membrane, and thus increase the time to Current efforts are focused on composite films for the treatment of polychlorinated biphenyl (PCB) contaminated sediments. In this case, the reagent is bacteria, which are theoretically inexhaustable.This work is a joint effort with Prof. Edward Cussler (Chemical Engineering and Materials Science) and Paige Novak (Civil Engineering). Pharmaceuticals and personal-care products (e.g., anti-microbials in soaps) are released into surface waters via dicharge of treated and untreated human and animal wastes. Thus, these compounds with known biological effects (e.g., antibiotics and hormones) are continuously discharged into lakes and rivers. The impact of these compounds will be partially determined by their persistence in the environment. Direct and indirect photolysis are processes likely to degrade pharmaceutical compounds in surface waters. By assessing the rates of these processes, we can determine We currently have two ongoing projects. In collaboration with Dr. McNeill and Dr. Deborah Swackhamer, we are identifying dioxin and furan products that arise from the photolysis of halogenated diphenyl ethers, including triclosan (the antimicrobial in handsoap) and PBDEs (flame retardants). We are also seeking these products in environmental matricies. The second project (a collaboration with Dr. Timothy LaPara) is investigating the utility of solar treatment of wastewater and the thermal digestion of biosolids to remove pharmaceuticals and inactivate antibiotic resistant bacteria. The water quality of streams draining watersheds has been degraded by increasing urbanization. We propose to transform traditional and very limited (in terms of spatial and temporal resolution) field measurements through the integration of multi-scale, spatially-dense, high frequency, real-time, and event-driven observations by a wireless network with embedded networked sensing. This will allow quantification of processes across scales and the capture of non-linear events. The overall objective of our research is to establish a wireless network with embedded sensing capable of monitoring fundamental water quality parameters. The ability of these fundamental water quality parameters to be used for predicting the presence of emerging chemical contaminants (pesticides and pharmaceuticals) iin urban streams will also be determined. It is hypothesized that the water quality in streams draining similar impervious urban areas is controlled by the mean and variance of effective stormwater residence time. The mean and variance of water residence time, the time it takes urban runoff to travel between the impervious urban land and a receiving aquatic body, will be characterized by radio frequency identification technology (RFID), which will be augmented with the proposed wireless network. We are currently working iin two local urban watersheds. We have deployed a network capable of measuring temperature, water depth, pH, conductivity, rainfall, turbidity and nutrients (nitrate and phosphate). We are seeking to: (1) measure fundamental water quality and hydrologic parameters with spatially-dense and high frequency resolution, (2) correlate general parameters with the presence and/or levels of emerging contaminants, and (3) integrate field measurements to the watershed using primarily the mean and variance of effective stormwater residence time. Water quality in streams will be observable as a dynamic response to land use gradients and hydrological transients rather than as an equilibrium described by average properties. This approach will enable process-based scaling and forecasting of water quality in streams from the in-stream processes to the watershed level. Studying Mineral Growth during Reaction with Pollutants Most studies of organic pollutants tranformation by mineral surfaces have focused on changes in the solution phase (i.e. the disappearance of the contaminant). In collaboration with Dr. R. Lee Penn, we have been using a variety of microscopic techniques, including tranmission electron microscopy (TEM), X-ray diffraction (XRD), and atomic force microscopy (AFM) to quantitatively link changes in the mineral surface with the kinetics of contaminant loss in solutions Recent work demonstrated that with each successive reaction with either 4-chloronitrobenzene or trichloronitromethane the goethite becomes less reactive, even when the Fe(II) is replenished in the system. The particles only grew in one direction (along the c-axis) and the particle tips became roughened. We are currently expanding the number of chemicals tested and the solution conditions to see how the minerals grow under these conditions. Abiotic Transformations of Disinfection Byproducts (DBPs) Because "unlined" cast and ductile iron pipe are present in many distribution systems, this research was performed to evaluate the abiotic degradation of DBPs by iron metal (Fe0), synthetic iron minerals, and iron corrosion pro |
breakthrough. We have built model reactive membrane barriers (using polyvinyl alcohol) containing either zero-valent iron (to contain chlorinated solvents) particles or crystalline silicotitanate (to contain Cs+ and Sr2+) particles. After these model experiments, we have successfully extended to work to the practical polymer high density polyethylene. The iron is oxidized even in the hydrophobic 
the lifetime of these compounds in natural systems and assess whether there is the potential for these compounds to have adverse effects on the biota in these ecosystems. Over the past six years, we have published 
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ducts.The experimental approach involves batch experiments performed in glass serum bottles and in reactors comprised of 6 inch ID x 12 inch iron pipe sections. An investigation of the kinetics and pathways of the degradation of the nine chlorinated and brominated haloacetic acids (HAAs) and the three chlorinated halonitromethanes (HNMs) by iron metal has been completed. All compounds were completely dehalogenatd via hydrogenolysis, except for chloropicrin (trichloronitromethane), which was degraded via a combination of hydrogenolysis and alpha-elimination. The end products of the degradation of HAAs and HNMs were acetate and methylamine, respectively. Most experiments were performed in the absence of competing oxidants such as dissolved oxygen or chlorine, but we have also investigated the kinetics of DBP degradation in the presence of these oxidants. The degradation of additional classes of DBPs (e.g., haloacetonitriles, haloketones) by Fe0, and the degradation of DBPs by iron minerals (e.g., green rust, magnetite) and iron corrosion products obtained from water distribution systems (see photo of pipe above) has also been investigated. This research has important implications for understanding and predicting the fate of DBPs in water distribution systems and may be useful for designing new water treatment systems for DBP removal from water supplies.