Browsing by Author "Robert C. Borden, Committee Member"

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A Fundamental Investigation of Well Injection Depth Extraction (WIDE) System Performance Aspects in Fine-Grained Soil Contaminated with Trichloroethylene
(2003-12-06) Warren, Kimberly Anne; Mohammed S. Rahman, Committee Member; Roy H. Borden, Committee Member; Mohammed A. Gabr, Committee Chair; Robert C. Borden, Committee Member
This research consisted of three components: the field demonstration, laboratory experimentation, and finite element analysis. Global WIDE system performance (in-situ ground water and contaminant transport) was investigated during the field demonstration, PVW performance was examined during laboratory experimentation, and contaminant partitioning tendencies were evaluated as a function of time and operational scheme during the finite element analysis. The field demonstration was conducted at a site located in Ashtabula, Ohio. With the exception of a silt seam located approximately 1.8 m to 2.4 m below the ground surface, the subsurface consisted of clay (CL) and the in-situ permeability was determined to be approximately 1x10-6 cm/s. TCE contamination levels as high as 300,000 mg/kg were detected on the soil, and concentrations as high as 475 mg/L were detected in the ground water. A 21.0 m by 18.3 m WIDE demonstration system was installed over an area that encompassed a TCE plume. The test area was divided into four quadrants and 494 PVWs were installed to a depth of 6.1 m. Concurrent injection extraction, alternating row extraction, and full quadrant extraction operations took place over a nine month demonstration. Vacuum pressure, injected and extracted fluid volumes, TCE concentrations (gas and soluble-phase), and water table levels were monitored. A 10 kPa laboratory tracer test experiment was conducted using a 1.0 m3 clay slurry sample with a high permeability soil seam, similar to field conditions. The test box was lined with a geocomposite to provide a constant head reservoir boundary around the test sample. Three settlement plates, 23 piezometers, and 27 tracer tubes were installed to monitor settlement, pressure head, and chloride (Cl) tracer concentration, respectively. The zone of influence and PVW geometry effects were evaluated. NAPL Simulator (a three-dimensional finite element analysis model) was calibrated using hydraulic field data and then used to simulate soluble and gas-phase contaminant transport in saturated and unsaturated soil media. Using a reference case, a parametric evaluation was initially performed to establish the input variables that significantly affect contaminant transport. System performance and contaminant partitioning tendencies were evaluated as a function of time and operational scheme. Finally, a sensitivity analysis, consisting of 36 simulations, was performed to evaluate contaminant partitioning tendencies as a function of the PVW spacing, extraction water flow rate, and mass transfer coefficient.
Hydrologic and Water Quality Assessment of Constructed Wetlands on a Coastal Plains Golf Course
(2008-12-02) Pekarek, Kathryn Ashley; Robert C. Borden, Committee Member; Robert O. Evans, Committee Chair; R. Wayne Skaggs, Committee Member
Golf courses have come under considerable scrutiny in recent years due to the large amount of chemicals and nutrients associated with their intensive management. Drainage water from the Chowan Golf and Country club in eastern North Carolina drained directly into the nutrient sensitive Albemarle Sound. Stormwater wetlands were constructed on the golf course as part of a vegetative treatment network to reduce nutrients in stormwater runoff, reduce ponding on the course, and provide additional water storage for irrigation. The wetlands were monitored for three years to evaluate the performance of the Best Management Practices (BMPs) established. Precipitation and weather data were used with stage-discharge and outflow to compute water balances for each wetland in the vegetative treatment network. Throughout the three year study period, wetlands temporarily stored between 5% and 85% of the water which entered the wetlands. During a period of drought, all wetlands stored a larger percentage of influent water than during normal rainfall periods. Peak flow rates were reduced by 7% to 92% and time to peak was delayed by 10 to 46 hours. Residence times were evaluated for wetlands with small (1:40 (2.5%)), medium (1:23 (4.5%)), and large (1:11 (9.0%)) wetland:watershed area ratios. On average, residence times were more than five days 6% of the time in the wetland with the small wetland:watershed area ratio, 45% of the time in the wetland with the medium wetland:watershed area ratio, and 66% of the time in the wetland with the large wetland:watershed area ratio. Five day residence times are generally considered the minimum residence time for effective settling of sediment, and treatment of nitrogen and phosphorus. This study demonstrates that stormwater wetlands can be utilized to reduce outflow volume and peak discharge rates in areas where drainage discharge is a concern of receiving waters. Influent and effluent concentration data was collected and combined with water balances for each wetland over a three year period. Influent concentrations from runoff had an average of 3.65 mg/L Total Kjeldahl Nitrogen (TKN), 0.15 mg/L nitrate-nitrogen (NO3-N), 0.30 mg/L ammonia-nitrogen (NH4-N) 3.82 mg/L total nitrogen (TN), 1.61 mg/L ortho-phosphate (PO4-P), and 2.06 mg/L total phosphorus (TP). Effluent water had mean concentrations of 2.06 mg/L TKN, 0.06 mg/L NO3-N, 0.14 mg/L NH4-N, 2.07 mg/L TN, 0.60 mg/L PO4-P, and 1.62 mg/L TP. Runoff water carried a mean of 12.80 kg/ha/yr TKN, 0.57 kg/ha/yr NO3-N, 1.30 kg/ha/yr NH4-N, 13.32 kg/ha/yr TN, 5.62 kg/ha/yr PO4-P, and 7.17 kg/ha/yr TP. The wetlands removed an average of 29% TKN, 67% NH4-N, 51% TN, 70% PO4-P, and 64% TP on a mass basis. Removal efficiencies for wetlands with small (1:40), medium (1:23), and large (1:11) wetland:watershed areas were compared in detail. At loading rates above 1.0 kg/ha/d TN, an increase wetland:watershed area ratio was shown to increase removal rate. An increase in wetland:watershed area ratio also increased TP removal rate. On average, the wetland with the small ratio reduced TN and TP loads by 45%. The wetland with the medium ratio reduced TN loads by 49% and TP loads by 83%. The wetland with the large ratio reduced TN load 84% and TP loads by 88%.
Molecular Characterization of Microbial Populations in Full-Scale Activated Sludge Plants and Bioaugmentation Sites
(2003-11-18) Keith, Julia Elizabeth; Robert C. Borden, Committee Member; Morton Barlaz, Committee Member; Francis de los Reyes, Committee Chair
The application of molecular biology techniques to the study of wastewater treatment and bioaugmentation was demonstrated in three studies. In the first study, full scale activated sludge treatment plants in North Carolina were surveyed to (1) determine the extent of filamentous bulking and foaming, and (2) relate these problems to the microbial community structures in the activated sludge reactors. Oligonucleotide probes targeting the rRNA of the major sublasses of the Proteobacteria, the mycolic acid containing actinomycetes (mycolata) and Sphaerotilus natans were used in quantitative hybridizations with samples from sixteen full scale plants. The survey results showed that 88% and 63% of plants in North Carolina have experienced bulking and foaming, respectively. No statistically significant correlations between the frequency and severity of foaming and the levels of any of the microbial groups were observed. However, several of the plants that had the most severe foaming problems had high levels of mycolata and alpha Proteobacteria. Bulking in the sampled plants is probably not caused by Sphaerotilus natans but by other filaments, or other floc characteristics. The sampling protocol raised questions about possible change between collection and analysis, and a second study was designed to determine optimal storage conditions. Quantitative hybridizations with the same set of probes used in the first study showed that treatment with chloramphenicol proved best in minimizing change over time in wastewater samples. However, storage at room temperature was also a viable storage option. In the third study, molecular methods were used to detect the bacterium Bacillus DA33 in augmented wastewater and soil samples. A probe targeting the 16S rRNA of this organism was designed and characterized for use in quantitative membrane hybridizations. Because a unique target sequence was not available within the 16S rRNA, another probe, this time targeting the 16S-23S intergenic spacer region, was designed and characterized. Hybridization results showed that levels of Bacillus DA33 were higher in soil than in wastewater. In several bioaugmented soil and wastewater samples, Bacillus DA33 had higher levels than in non-bioaugmented samples, but the results were mixed in other cases. Molecular methods allow us to analyze environmental samples in more detail. Integrating these methods in future studies of wastewater treatment and bioaugmentation should provide more information that will help improve design and operation.