Seminar/Events
Regular Department Seminar Monday – May 5, 2008 Evaluating the efficacy of synchrotron X-ray microtomography as a method for measuring immiscible-liquid/-water interfacial area. By Matthew Narter, SWES M.S. StudentAdvisor: Dr. Mark Brusseau Assessing the potential for monitored natural attenuation at chlorinated solvent hazardous waste sites using compound specific isotope analysis By: Justin Berkompas, SWES M.S. StudentAdvisor: Dr. Mark Brusseau Wednesday May 7 Comparison of Staphylococcus aureus and MRSA Survival in Laundry Between Top-Loading and Front-Loading Washing Machines By: Jeanne Nordstrom, SWES M.S. Student Advisor, Dr. Charles Gerba
|
submit an event SWES Calendar Announcements/Upcomming Events
SWES Faculty Retreat: Thursday, 8 May2008 at ERL – 8:30
|
Evaluating the efficacy of synchrotron X-ray microtomography as a method for measuring immiscible-liquid/-water interfacial area
Abstract
Previous studies have shown that immiscible-liquid/water interfacial areas measured with synchrotron X-ray microtomography are significantly smaller than those measured using the interfacial tracer test method for natural porous media. Research was conducted to evaluate the source of the disparity between these methods. It has been hypothesized that the disparity is due primarily to resolution constraints associated with microtomography, wherein the interfacial area associated with microscopic surface roughness is not measured. To test this hypothesis, experiments were conducted with glass beads (which have very little surface roughness). Tetrachloroethene (PCE) was used as the model immobile liquid and sodium dodecylbenzene sulfonate was used as the interfacial tracer. Glass beads were also packed into smaller aluminum columns for analysis using synchrotron X-ray microtomography. Tracer tests yielded an average interfacial area of 9.1 ± 10.9 cm-1 while microtomography results gave an interfacial area of 3.0 ± 2 cm-1. The values are similar for the two methods, indicating that the disparity observed for natural media is likely due to resolution limitations of microtomography
Assessing the potential for monitored natural attenuation at chlorinated solvent hazardous waste sites using compound specific isotope analysis
Abstract
Chlorinated solvents are the most common contaminants at the state and federal Superfund sites in Arizona and, given their myriad toxicological effects, pose a great risk to human health. The remediation of polluted soil and groundwater at the many chlorinated-solvent contaminated sites present in Arizona is critical for ensuring a safe and sustainable potable water supply. Monitored natural attenuation (MNA) has recently gained great interest as a low-cost, low-tech approach for site remediation. The primary driver of MNA feasibility is the rate at which contaminants are degraded. The goal of this project is to assess the feasibility of MNA at chlorinated solvent sites using compound specific isotope (CSI) analysis as a rapid, inexpensive, and accurate technique to characterize biodegradation rates for chlorinated solvents. Reductive dechlorination of chlorinated ethenes results in a specific, replicable and measurable enrichment of 13C in the parent chlorinated solvent. This enrichment can be used to calculate a biodegradation rate of a given compound. Data obtained from the CSI analysis will be used in conjunction with a mathematical model to evaluate MNA feasibility.
Comparison of Staphylococcus aureus and MRSA Survival in Laundry Between Top-Loading and Front-Loading Washing Machines
ABSTRACT
This study was conducted to determine whether Staphylococcus aureus and its methicillin resistant form (MRSA) added to cotton cloth swatches survive typical household laundry practices in the United States - a wash cycle, rinse cycle, and a permanent press drying cycle. Detergent was added to top-loading washing machines containing sterile and bacterial inoculated swatches and 3.2 kg of sterile cotton T-shirts. Loads containing soiled pillowcase designed to simulate the conditions (pH, organic load, etc.) encountered in soiled laundry were also run. The addition of bleach, different wash temperatures and cycle lengths were employed to determine the effect of each parameter on bacterial survival. Experiments were repeated with front-loading washers. Washing with detergent alone afforded at least a five log reduction in bacteria concentration. Complete drying and bleach use further decreased this level by an additional log. Front-load washers were more successful at lowering bacterial counts than top-loaders in nearly all laundry tests performed, most likely due to their longer rinse cycles. Laundering practices in common use in the United States do not completely eliminate Staphylococcus aureus or MRSA from clothes. The use of hot water and bleach can further reduce the numbers of surviving bacteria in laundry.