Evaluating the Potential of Trapped Nano-size Oxygen Bubbles (NOBs) for a Controlled-release Oxygen Source of Prolonged BTEX Aerobic Biodegradation in Groundwater
Abstract
Control of dissolved oxygen (DO) concentration is a critical factor to sustain BTEX aerobic biodegradation. If nano-size oxygen bubbles (NOBs) are trapped among soil particles or rock-fractures in groundwater, they could slowly release DO and maintain aerobic degradation for several months.
This study evaluates the amount of NOBs trapped by injecting NOBs water and DO releasing pattern from the NOBs by performing soil column tests. Four soil columns with bulk density of 1.59±0.02 g/cm3 and porosity of 0.36±0.01 were prepared. To remove air bubbles trapped during soil packing, 0.1 L of CO2 gas was slowly injected into the columns and then vacuum was created inside the columns for five minutes. The CO2 gas injection and creating a vacuum were repeated five times. 0.3 L of degassed DI water was pumped into the column. DO transport test (DTT) and NOB Trapping and DO releasing test (NTDT) were performed. During the DTTs, the breakthrough curves for DO and bromide (a tracer) was similar, and retardation factor (R) of DO was close to zero, suggesting little residual trapped air gas in the four columns. In order to determine the amount of trapped NOBs and assess DO releasing pattern from NOBs, NTDT were conducted by injecting NOB water (0, 1,000, 5,000, and 10,000 times of pore volume) into four soil columns. The ratios of trapped gas volume versus pore volume (Vg/Vw) in the each soil columns was 0.01, 0.02, 0.08, and 0.20, respectively, and the mass of oxygen eluted from the trapped gas was 118, 139, 194, and 481% of the mass of DO injected into the soil column. These results suggest that NOBs trapped among soil particles or rock-fractures in groundwater could be an effective slow-releasing source of DO and could allow to maintain aerobic degradation for several months. ACKNOWLEDGEMENT This research was supported by Korea Ministry of Environment and the Technology Institute (KEITI) as "The Subsurface Environmental Management(SEM) project(2018002480005)"- Publication:
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AGU Fall Meeting Abstracts
- Pub Date:
- December 2019
- Bibcode:
- 2019AGUFM.H23I2005K
- Keywords:
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- 1829 Groundwater hydrology;
- HYDROLOGY;
- 1831 Groundwater quality;
- HYDROLOGY;
- 1832 Groundwater transport;
- HYDROLOGY;
- 1847 Modeling;
- HYDROLOGY