• Exploring Holistic Approaches to the Characterization of Particles in the Environment

      Anhalt, Ashley; Peterson, Tawnya; Tratnyek, Paul; Needoba, Joseph; Mather, Amanda (2011-11-04)
      Most of the main determinants of water quality either consist of, or are controlled by, particles. Previous water quality research has focused on particular particles in isolation or in binary combinations. In this project, we are taking a holistic approach to the characterization of the particle load in water, focusing on the collective properties of the particles rather than individual components. Because the characterization of particles is often time-consuming, applying an informatics-based approach could speed up the evaluation of water quality and the assessment of treatment effectiveness. Further, the breadth of potential changes that could be detected using this multiplex approach may far surpass the abilities of current approaches to monitor threats to water quality. Among the instruments capable of rapidly detecting and manipulating cells is imaging flow cytometry, which distinguishes cell shape and unique fluorescence properties associated with cell types. Sets of images and corresponding data from a 1.5-year time series of samples from the Columbia River were studied and the different particle properties analyzed. Principal Component Analysis (Empirical Orthogonal Function analysis) was applied in order to reduce the number of variables and identify patterns in particle characteristics when compared to environmental data collected from the observation station. The first three principal components were extracted and the dominant characteristics identified: the most prominent variables are particle size, particle color, and fluorescent qualities (transparency and phytoplankton pigments). Further work will relate these top principal components to specific environmental factors that determine water quality.
    • Modeling Advanced Oxidation Processes for Water Treatment

      Anhalt, Ashley; Sáez, A. Eduardo; Arnold, Robert; Rojas, Mario; Department of Chemical and Environmental Engineering (2012-11-09)
      Civilization is dependent on wastewater treatment plants. However, many conventional wastewater treatment processes only partially remove trace organics that result from human use, such as pharmaceuticals and endocrine disrupters. Advanced oxidation process (AOP) can be used to remove chemicals that may remain in the treated wastewater. AOP is an enhanced alternative to the traditional water treatment processes because it turns water contaminants into carbon dioxide (CO2), as opposed to simply transporting the contaminants across the different treatment phases. In order to model this process, one proposed idea uses ultraviolet light and hydrogen peroxide to oxidize the unwanted organic compounds. Previous mathematical models have been developed to simulate the UV/H2O2 process, however, the model employed in this work has advanced beyond previous efforts. Our UV/H2O2 model aims to characterize the mechanism and kinetics behind the decomposition of nonylphenol (NP) and p-cresol (PC), two chemicals in wastewater that serve as surrogates for endocrine disrupters. The model demonstrates agreement between experimental results and AOP simulations accounting for light intensity, pH, hydrogen peroxide levels, and concentrations of other radical scavengers. Our goal is to improve an already robust UV/H2O2 AOP model by taking into account spatial variations of radical concentrations. Our results take into account time and space, and show significant improvement in the accuracy of the model. This broadens the applications of this model and consequently, the degradation of organic contaminants is predictable over a wide range of conditions. The potential for polishing conventionally treated wastewater is evident.