Bruce I. Dvorak

Removing 17β-estradiol from drinking water in a biologically active carbon (BAC) reactor modified from a granular activated carbon (GAC) reactor

Estrogenic compounds in drinking water sources pose potential threats to human health. Treatment technologies are needed to effectively remove these compounds for the production of safe drinking water. In this study, GAC adsorption was first tested for its ability to remove a model estrogenic compound, 17β-estradiol (E2). Although GAC showed a relatively high adsorption capacity for E2 in isotherm experiments, it appeared to have a long mass transfer zone in a GAC column reactor, causing an early leakage of E2 in the effluent. With an influent E2 concentration of 20 μg/L, the GAC reactor was able to bring down effluent E2 to ≈ 200 ng/L. To further enhance E2 removal, the GAC reactor was converted to a biologically active carbon (BAC) reactor by promoting biofilm growth in the reactor. Under optimal operating conditions, the BAC reactor had an effluent E2 concentration of ≈ 50 ng/L. With the empty bed contact times tested, the reactor exhibited more robust E2 removal performance under the BAC operation than under the GAC operation. It is noted that estrone (E1), an E2 biodegradation intermediate, was frequently detected in reactor effluent during the BAC operation. Results from this study suggested that BAC could be an effective drinking water treatment process for E2 removal and in the meantime E1 accumulation needs to be addressed.

Improving the treatment of non-aqueous phase TCE in low permeability zones with permanganate

Treating dense non-aqueous phase liquids (DNAPLs) embedded in low permeability zones (LPZs) is a particularly challenging issue for injection-based remedial treatments. Our objective was to improve the sweeping efficiency of permanganate (MnO4(-)) into LPZs to treat high concentrations of TCE. This was accomplished by conducting transport experiments that quantified the penetration of various permanganate flooding solutions into a LPZ that was spiked with non-aqueous phase (14)C-TCE. The treatments we evaluated included permanganate paired with: (i) a shear-thinning polymer (xanthan); (ii) stabilization aids that minimized MnO2 rind formation and (iii) a phase-transfer catalyst. In addition, we quantified the ability of these flooding solutions to improve TCE destruction under batch conditions by developing miniature LPZ cylinders that were spiked with (14)C-TCE. Transport experiments showed that MnO4(-) alone was inefficient in penetrating the LPZ and reacting with non-aqueous phase TCE, due to a distinct and large MnO2 rind that inhibited the TCE from further oxidant contact. By including xanthan with MnO4(-), the sweeping efficiency increased (90%) but rind formation was still evident. By including the stabilization aid, sodium hexametaphosphate (SHMP) with xanthan, permanganate penetrated 100% of the LPZ, no rind was observed, and the percentage of TCE oxidized increased. Batch experiments using LPZ cylinders allowed longer contact times between the flooding solutions and the DNAPL and results showed that SHMP+MnO4(-) improved TCE destruction by ∼16% over MnO4(-) alone (56.5% vs. 40.1%). These results support combining permanganate with SHMP or SHMP and xanthan as a means of treating high concentrations of TCE in low permeable zones.

Intensive Environmental Sustainability Education: Long-Term Impacts on Workplace Behavior

The University of Nebraska Partners in Pollution Prevention (P3) program has provided a results-oriented intensive sustainability course since 1997. This course focuses on providing students with application tools to promote environmental sustainability, including a service learning internship component directly on site at businesses. A survey was used to evaluate the long-term impact of this intensive sustainability course on subsequent workplace behavior of past student interns. Comparison of former interns with a control group found that interns reported they were more likely to apply source reduction principles in their workplace and more able to quantify the impact of implementation. A strong personal environmental ethic was an important predictor of reporting success in applying source reduction. Those past students with the intensive sustainability course and a self-reported strong environmental ethic were significantly more likely to report successful implementation of source reduction, even thoug...

Application of fuzzy set theory to industrial pollution prevention: production system modeling and life cycle assessment

Abstract This research describes a framework and case study application that merges fuzzy set methods, pollution prevention, and sustainable production concepts. There is a direct linkage between industrial pollution prevention, sustainability, and the solution of large-scale environmental problems. This linkage stems from the inherent desire for economic production, while at the same time protecting the environment from further degradation. The methodology combines systems analysis under imprecise conditions with a life cycle assessment method that is able to accept imprecise data. Analysis of systems under imprecise conditions is accomplished through analysis of process flow diagrams using fuzzy set techniques. Introduction of imprecision into life cycle assessment is accomplished by integration of fuzzy set approaches into a decision support system utilizing multiple criteria decision making. The framework is described and a case study application of an industrial parts cleaning system using an open top vapor degreaser is presented. Results of applying the method show that: (1) It is well suited for analysis of complex systems in which input data is sparse and expensive to collect. (2) The proposed framework includes a decision support system that is able to consider life cycle assessment concepts, and is able to reconcile differing opinions on available options for modification of production systems, thereby leading to more sustainable solutions.

Yard waste compost as a stormwater protection treatment for construction sites.

Runoff water quality improvement from three yard waste compost erosion control treatments were compared with two conventional treatments and an untreated control on plots of 3:1 slope during two growing seasons, using natural events and simulated rainfall. Runoff volume, suspended solids, nutrients, biomass, turf shear strength, and turfgrass color scale were monitored. The most effective compost treatment, a 5-cm thick blown compost blanket, produced 12.7 times less runoff and 9.8 times less sediment load than a straw mat and silt fence treatment. The compost treatments generated eight times more biomass than the straw mat treatments. Root development was significantly better on the compost treatments based on turf shear strength measurements. Tilled-in compost was not as effective as a compost blanket at reducing sediment loss, particularly before the establishment of grass on the plot. The cost of compost treatments was similar to that of straw mat with silt fence treatments.

Maximizing sorbent life: comparison of columns in parallel, lead-lag series, and with bypass blending.

Various adsorption column configurations can be used to increase fractional utilization and decrease adsorbent usage rate. This study compared the adsorbent usage rate of different column configurations. Mathematical models simulated chromatographic breakthrough front shapes and determined adsorbent usage rates. A configuration selection diagram based on percent mass-transfer zone (MTZ) and target C/Co (effluent concentration/influent concentration) was created to compare the adsorbent usage rate of configurations for single component systems. The target C/Co determined the column configuration with the lowest adsorbent usage rate when the MTZ was a large percentage of the column (> 60%), while all column configurations generally performed similarly at short percent MTZs (< 30%). Bypass blending was found to be most effective with a lead-lag configuration and the maximum amount of bypass. A sensitivity analysis determined that competitive adsorption can significantly change the configuration selection diagram and generally makes lead-lag more competitive compared with parallel column configurations.

Implications of Hidden Costs: Comparison of Bitumen Testing Procedures

Traditional cost analyses used for process cost comparisons often ignore costs (e.g., waste disposal, regulatory compliance, long-term liabilities) that are lumped into general overhead but actually are incurred during the process. In this research, both a traditional cost analysis and a total cost assessment (which includes many often-neglected process costs) were performed on five potential methods of testing the bitumen composition of newly paved asphalt. In the past, the bitumen content of asphalt pavement was determined by tests using toxic solvents; alternative, less polluting methods have been developed that can replace the traditional solvent extraction method. In order to represent the uncertainties in the design and cost data (especially the liability costs) for this cost comparison, fuzzy set theory was used. A traditional economic analysis that included only the capital and operating and maintenance costs found that the most environmentally friendly process (ignition ovens) was only slightly less costly than two other options. The cost of the ignition ovens and two other options were similar enough to be considered within the range of uncertainty for the analysis. However, when the hidden costs related to the environmental, health, and safety aspects for a bitumen testing procedure were incorporated into the cost analysis, the cost comparison changed significantly; the most environmentally-friendly option, ignition ovens, was shown to be by far the least-cost option. Thus, incorporating hidden environmental costs into a cost analysis can have a significant impact.

Comparison of Asphalt Extraction Procedures: Implications of Hidden Environmental and Liability Costs

In the past, asphalt extractions were performed using toxic solvents; alternative, less polluting methods have been developed that can replace the traditional solvent extraction method. Accordingly, five potential asphalt extraction methods were compared for the Nebraska Department of Roads Bituminous Laboratory: solvent extraction using trichloroethylene (TCE), solvent extraction using an alternative solvent, solvent extraction using TCE and a solvent recovering reclaimer, ignition oven, and an ignition oven and solvent combination. To compare the total cost of each option, the direct capital costs, operating and maintenance costs, as well as the hidden environmental, health, and safety costs were considered. Because the hidden costs can be difficult to quantify, a total cost assessment approach was used. To represent the uncertainties in the cost and design data, fuzzy set theory was used. A traditional economic analysis, including only the capital, and operating and maintenance costs, found that the three least-cost options were within the range of uncertainty of the analysis; these three options were the ignition oven (most environmentally friendly option), ignition oven with solvents, and solvent reclaimer. However, when the hidden costs related to the environmental, health, and safety aspects for an asphalt extraction procedure were incorporated into the cost analysis, the cost comparison changed significantly; the most environmentally friendly option, ignition oven, was shown to be by far the least-cost option. Accordingly, the quantification of environmental, health, and safety costs that are difficult to assess is very important when evaluating environmentally friendly processes.

Framework for Evaluating Sorbent Usage Rate of Various Sorption Column Configurations with and without Bypass Blending

AbstractThis study evaluated the system performance in terms of sorbent usage rate (SUR) of single column, two-column parallel, and lead-lag configurations, both with and without bypass blending, based on two normalized parameters describing the breakthrough profile (mass transfer zone length to lag ratio, or MTZ:Lag) and treatment objective (C/Co). The pore surface diffusion model was used to simulate a range of single compound scenarios to develop a framework for comparing configurations. From this analysis, regions on a MTZ:Lag versus C/Co plot could be identified in which particular configurations yielded the lowest system SUR. At low MTZ:Lag ratios, bypass blending (single column or lead-lag operation) offered significant improvements because of the ability to bypass untreated flow and reduce sorbent bed mass. However, at low target C/Co values, bypass offered little improvement. Lead-lag without bypass performed best at high MTZ:Lag ratios by passing the mass transfer zone through two columns in ser...

Atmospheric Contributions of Nitrate to Stormwater Runoff from Two Urban Watersheds

AbstractTwo independent methods were used to assess if atmospheric deposition was a major source of nitrate nitrogen (NO3-N) to stormwater in two small urban watersheds located in Lincoln, NE. Firs...