The objective of this research was to demonstrate the application of ultrasound to field sites having problems with precipitation build up and corrosion. PTW s are passive reactive walls containing zero-valent iron metal for in-situ remediation of contaminated groundwater. However, loss of reactivity over time due to build up of corrosion and other precipitates on the iron surface is a major concern. Ultrasound energy has been established as an effective tool for revitalizing iron surface. This research applied ultrasound energy to a zero-valent iron wall constructed below the ground surface to remove precipitates and iron corrosion, increasing iron reactivity. Two field sites were selected for the ultrasound application research project. These sites have PTWs installed for the remediation of chlorinated compounds such as TCE and its daughter products. The first site is located at Launch Complex 34 (LC 34), Cape Canaveral Air Station, Florida. The second site is located at Denver Federal Center, Lakewood, Colorado. The ultrasound was applied to these sites by introducing an ultrasonic transducer in wells installed within the wall or just upstream of the wall and then applying ultrasonic energy to the entire depth of the wall. The apparatus used for ultrasound application was an omni-directional tubular resonator. Two such ultrasound units with frequencies of 25 kHz and 40 kHz were used for ultrasound treatment. Kinetic batch studies were performed on iron samples taken before and after ultrasound treatment. The degradation rate constants and half-life values for TCE were then calculated and con1pared for pre-ultrasound and post-ultrasound iron san1p les. Sin1ultaneously grounchvater \vas analyzed for di ffercnt VOCs. Soni cation period as brief as 30 n1inutes sho\vcd signi fie ant in1pact on the firstorder rate constants for TCE degradation. An increase in sonication period proved to be even n1ore effective. A sonication period of 90 n1inutes decreased TCE half-life by 30-40% for the 40-kHz resonator and 60-75~o for the 25-kHz resonator, for both the field sites. The 25-kHz resonator proved to be more effective than the 40-kHz resonator. For both field sites, ultrasound treatn1ent significantly increased TCE degradation rates, indicating a ren1oval of corrosion products and precipitates from the iron surface due to ultrasound. This technology has shown a great potential in revitalizing iron reactivity, effectively increasing the PTW life expectancy.
| Identifer | oai:union.ndltd.org:ucf.edu/oai:stars.library.ucf.edu:rtd-2987 |
| Date | 01 January 2000 |
| Creators | Sonawane, Aamod Sudhakar |
| Publisher | University of Central Florida |
| Source Sets | University of Central Florida |
| Language | English |
| Detected Language | English |
| Type | text |
| Format | application/pdf |
| Source | Retrospective Theses and Dissertations |
| Rights | Written permission granted by copyright holder to the University of Central Florida Libraries to digitize and distribute for nonprofit, educational purposes. |
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