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Michael D Annable - One of the best experts on this subject based on the ideXlab platform.
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effect of increased groundwater viscosity on the remedial performance of surfactant enhanced Air sparging
Journal of Contaminant Hydrology, 2018Co-Authors: Jaekyeong Choi, Hobin Kwon, Michael D AnnableAbstract:Abstract The effect of groundwater viscosity control on the performance of surfactant-enhanced Air sparging (SEAS) was investigated using 1- and 2-dimensional (1-D and 2-D) bench-scale physical models. The viscosity of groundwater was controlled by a thickener, sodium carboxymethylcellulose (SCMC), while an anionic surfactant, sodium dodecylbenzene sulfonate (SDBS), was used to control the surface tension of groundwater. When resident DI water was displaced with a SCMC solution (500 mg/L), a SDBS solution (200 mg/L), and a solution with both SCMC (500 mg/L) and SDBS (200 mg/L), the Air Saturation for sand-packed columns achieved by Air sparging increased by 9.5%, 128%, and 154%, respectively, (compared to that of the DI water-saturated column). When the resident water contained SCMC, the minimum Air pressure necessary for Air sparging processes increased, which is considered to be responsible for the increased Air Saturation. The extent of the sparging influence zone achieved during the Air sparging process using the 2-D model was also affected by viscosity control. Larger sparging influence zones (de-saturated zone due to Air injection) were observed for the Air sparging processes using the 2-D model initially saturated with high-viscosity solutions, than those without a thickener in the aqueous solution. The enhanced Air Saturations using SCMC for the 1-D Air sparging experiment improved the degradative performance of gaseous oxidation agent (ozone) during Air sparging, as measured by the disappearance of fluorescence (fluorescein sodium salt). Based on the experimental evidence generated in this study, the addition of a thickener in the aqueous solution prior to Air sparging increased the degree of Air Saturation and the sparging influence zone, and enhanced the remedial potential of SEAS for contaminated aquifers.
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changes in Air Saturation and Air water interfacial area during surfactant enhanced Air sparging in saturated sand
Journal of Contaminant Hydrology, 2006Co-Authors: Kyongmin Choi, Jiwon Moon, Michael D AnnableAbstract:Abstract Reduction in the surface tension of groundwater, prior to Air sparging for removal of volatile organic contaminant from aquifer, can greatly enhance the Air content and the extent of influence when Air sparging is implemented. However, detailed information on the functional relationship between water Saturation, Air–water contact area induced by Air sparging and the surface tension of water has not been available. In this study, the influence of adding water-soluble anionic surfactant (sodium dodecyl benzene sulfonate) into groundwater before Air sparging on the Air–water interfacial area and water Saturation was investigated using a laboratory-scale sand packed column. It was found that water Saturation decreases with decreasing surface tension of water until it reaches a point where this trend is reversed so that water Saturation increases with further decrease in the surface tension. The lowest water Saturation of 0.58 was achieved at a surface tension of 45.4 dyn/cm, which is considered as the optimum surface tension for maximum de-Saturation for the initially water-saturated sand used in this study. The Air–water contact area generated in the sand column due to Air sparging was measured using a gaseous interfacial tracer, n -decane, and was found to monotonically increase with decreasing water Saturation. The results of this study provide useful design information for surfactant-enhanced Air sparging removal of volatile contaminants from aquifers.
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surfactant enhanced Air sparging in saturated sand
Environmental Science & Technology, 2004Co-Authors: Michael D AnnableAbstract:Air sparging as a subsurface remedial technique can be enhanced by the addition of a surfactant. The effect of reduced surface tension of water on the extent of Air intrusion and Air Saturation during Air sparging in porous media was investigated. A sand column and a two-dimensional sand box were used for the experiments. The surface tension was controlled using an anionic surfactant, sodium dodecyl benzene sulfonate, and the concentration used was below the critical micelle concentration. Using the sand column, the Air Saturation was measured at different surface tensions and at different Airflow rates. Initially water-saturated, the Air Saturation achieved in the column by Air sparging at a surface tension of 3.42 × 10-2 N/m was up to 5 times larger than that of water with no surfactant. At the same time, the rate at which the Air Saturation increased as a function of Airflow rate was greater at reduced surface tensions. For box experiments with homogeneous sand, reduction of the surface tension caused ...
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surfactant enhanced Air sparging in saturated sand
Environmental Science & Technology, 2004Co-Authors: Heoniki Kim, Michael D Annable, Hyoeun Soh, Dongjin KimAbstract:Air sparging as a subsurface remedial technique can be enhanced bythe addition of a surfactant. The effect of reduced surface tension of water on the extent of Air intrusion and Air Saturation during Air sparging in porous media was investigated. A sand column and a two-dimensional sand box were used for the experiments. The surface tension was controlled using an anionic surfactant, sodium dodecyl benzene sulfonate, and the concentration used was below the critical micelle concentration. Using the sand column, the Air Saturation was measured at different surface tensions and at different Airflow rates. Initially water-saturated, the Air Saturation achieved in the column by Air sparging at a surface tension of 3.42 x 10(-2) N/m was up to 5 times larger than that of water with no surfactant. Atthe same time, the rate at which the Air Saturation increased as a function of Airflow rate was greater at reduced surface tensions. For box experiments with homogeneous sand, reduction of the surface tension caused a dramatic increase in the sparging area up to 5.2 times of that generated using water with no surfactant. A sand box experiment containing a vertical channel produced preferential flow of the Air phase injected at the bottom of the channel when the surfactant was not applied. However, reducing the surface tension was found to promote Airflow through the preferential channel and the finer sand surrounding the channel. These observations support the use of low concentration surfactants to improve Air sparging swept zones.
David J Mckenzie - One of the best experts on this subject based on the ideXlab platform.
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an investigation of metabolic prioritization in the european sea bass dicentrarchus labrax
Physiological and Biochemical Zoology, 2010Co-Authors: Helene Jourdanpineau, A Dupontprinet, Guy Claireaux, David J MckenzieAbstract:Abstract We investigated the ability of European sea bass (Dicentrarchus labrax) to respond simultaneously to the metabolic demands of specific dynamic action (SDA) and aerobic exercise and how this was influenced by moderate hypoxia (50% Air Saturation). At 3 h after feeding in normoxia at 20°C, SDA raised the instantaneous oxygen uptake (Mo2) of sea bass by \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{amssymb} \usepackage{bm} \usepackage{mathrsfs} \usepackage{pifont} \usepackage{stmaryrd} \usepackage{textcomp} \usepackage{portland,xspace} \usepackage{amsmath,amsxtra} \usepackage[OT2,OT1]{fontenc} \newcommand\cyr{ \renewcommand\rmdefault{wncyr} \renewcommand\sfdefault{wncyss} \renewcommand\encodingdefault{OT2} \normalfont \selectfont} \DeclareTextFontCommand{\textcyr}{\cyr} \pagestyle{empty} \DeclareMathSizes{10}{9}{7}{6} \begin{document} \landscape $47\% \pm 18\% $ \end{document} (mean ± SEM, \documentclass{aastex} \usepackage{amsbsy} \usepackage{amsfonts} \usepackage{ams...
Giancarlo Flores - One of the best experts on this subject based on the ideXlab platform.
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changes in residual Air Saturation after thorough drainage processes in an Air water fine sandy medium
Journal of Hydrology, 2014Co-Authors: Zhen Xia, Qingshu Yang, Giancarlo Flores, Haoyu Jiang, Masashi KamonAbstract:Summary In a previous study we investigated the unstable and stable residual Air Saturations in an Air–water two-phase system in a sand medium during a series of consecutive drainage–imbibition cycles with gradually increasing initial Air Saturations. In a reciprocal study reported here we extended the previous investigation by determining residual Air Saturations in consecutive imbibition processes starting from four gradually decreasing levels of initial Air Saturation (and thus increasing water Saturation). Three parallel column tests with 9–12 consecutive drainage–imbibition cycles were performed, in which the first three imbibition processes started from the highest initial Air Saturation that could be obtained with our experimental system. The results show that all the residual Air Saturations resulting from the imbibition processes were almost constant after thorough drainage processes (even those following imbibition processes starting from low initial Air Saturations), and thus independent of the initial Air Saturation. The results also indicate that once the residual Air in interconnected pores at the end of an imbibition process was present in the form of connected, pore network-scale Air globules, the residual Air remained in this state in subsequent imbibition processes, even if they started from low initial Air Saturations. It may be deduced that the presence of thin water films on the walls surrounding large pores and large volumes of Air in their central parts during an imbibition process resulted in residual Air being in the form of connected, pore-network scale Air globules in interconnected pores. In contrast, thick water films and small volumes of Air in the central parts of the pores resulted in residual Air in the form of single pore-scale Air globules in interconnected pores. Thus, stronger dynamic flow conditions (e.g., higher capillary numbers) may be required to remobilize connected, pore network-scale Air globules than single pore-scale Air globules in a forced imbibition process.
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residual Air Saturation changes during consecutive drainage imbibition cycles in an Air water fine sandy medium
Journal of Hydrology, 2013Co-Authors: Giancarlo Flores, Weizhong Yue, Yuxin Wang, Tianggang LuanAbstract:Summary To clarify changes of residual Air Saturation under special (dynamic, nonequilibrium) conditions, the Saturation–capillary pressure (S–p) relationship including the residual Air Saturation under consecutive drainage–imbibition cycles, generated by scheduled water level fluctuations, in an Air–water two-phase sandy column was investigated. Water Saturation and capillary pressure were measured online and recorded using TDR (Time Domain Reflectometry) probes, T5 tensiometers and a datalogger. The results show that under dynamic flow conditions the residual Air Saturation changed suddenly from an unstable to a stable state with changes in initial Air Saturation during the series of imbibition cycles, and stable nonzero residual Air Saturation only occurred when the initial Air Saturation of the imbibition process exceeded 0.49, ca. double the value of the main imbibition process. Once stable residual Air Saturation was obtained, all the subsequent residual Air Saturations remained stable and constant in the following imbibition cycles. Before this threshold point, the residual Air Saturation gradually fell given sufficient imbibition time. The results also indicate that the unstable and stable residual Air Saturations were mainly due to discrete pore-scale Air globules trapped in the interiors of pores and pore-network scale globules located in interconnected pores, respectively.
Pauline M. Doran - One of the best experts on this subject based on the ideXlab platform.
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overexpression of alcohol dehydrogenase or pyruvate decarboxylase improves growth of hAiry roots at reduced oxygen concentrations
Biotechnology and Bioengineering, 2002Co-Authors: Tienli Shiao, M H Ellis, Elizabeth S Dennis, Rudy Dolferus, Pauline M. DoranAbstract:Overexpression of Arabidopsis thaliana genes for the fermentation enzymes, alcohol dehydrogenase and pyruvate decarboxylase, improved the tolerance of A. thaliana hAiry roots to low oxygen conditions. Whereas the specific growth rate of untransformed hAiry roots in shake flasks and in a multiple-tube recirculation bioreactor declined significantly with decreasing oxygen tension down to 25% Air Saturation, growth of the transformant root lines was maintained at rates similar to those achieved with full aeration. This work demonstrates that altering the expression of selected genes involved in anaerobic metabolism can alleviate the problems of oxygen deficiency in hAiry root cultures caused by poor mixing and mass transfer conditions.
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Oxygen requirements and mass transfer in hAiry-root culture.
Biotechnology and Bioengineering, 1994Co-Authors: Shaoxiong Yu, Pauline M. DoranAbstract:Oxygen mass transfer in clumps of Atropa belladonna hAiry roots was investigated as a function of root density and external flow conditions. Convection was the dominant mechanism for mass transfer into root clumps 3.5 to 5.0 cm in diameter; Peclet numbers inside the clumps ranged from 1.4 x 10(3) to 7.1 x 10(4) for external superficial flow velocities between 0.4 and 1.4 cm s(-1). Local dissolved-oxygen levels and rates of oxygen uptake were measured in aflow chamber and in bubble column and stirred bioreactors. When Air was used as oxygen source, intraclump dissolved-oxygen tensions ranged from90% to 100% Air Saturation at high external flow velocity andlow root density, to less than 20% Air Saturation in dense root clumps. Specific oxygen-uptake rate declined with increasing root density. When external boundary layers around individual roots were eliminated byforcing liquid through the clumps at superficial velocities between 0.2 and1.0 cm s(-1), internal dissolved-oxygen tension was maintained at 95% to 100% Air Saturation and rate of oxygen uptake at 1.6 x 10(-6) g g(-1) s(-1) dry weight. Liquid culture of single A. belladonna hAiry roots was used to investigate the effect of dissolved-oxygen tensionon root growth and morphology. Total root length and number of root tips increased exponentially at oxygen tensions between 70% and 100%Air Saturation. Specific growth rate increased with oxygen tension up to 100% Air Saturation; this result demonstrates that hAiry roots aeratedwithout oxygen supplementation are likely to be oxygenlimited. No growth occurred at 50% Air Saturation. Growth of hAiry roots proceeded with an average length per tip of about 1 cm; this value was essentially independent of dissolved-oxygen tension between 70% and 100% Air Saturation. (c) 1994 John Wiley & Sons, Inc.
Tianggang Luan - One of the best experts on this subject based on the ideXlab platform.
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residual Air Saturation changes during consecutive drainage imbibition cycles in an Air water fine sandy medium
Journal of Hydrology, 2013Co-Authors: Giancarlo Flores, Weizhong Yue, Yuxin Wang, Tianggang LuanAbstract:Summary To clarify changes of residual Air Saturation under special (dynamic, nonequilibrium) conditions, the Saturation–capillary pressure (S–p) relationship including the residual Air Saturation under consecutive drainage–imbibition cycles, generated by scheduled water level fluctuations, in an Air–water two-phase sandy column was investigated. Water Saturation and capillary pressure were measured online and recorded using TDR (Time Domain Reflectometry) probes, T5 tensiometers and a datalogger. The results show that under dynamic flow conditions the residual Air Saturation changed suddenly from an unstable to a stable state with changes in initial Air Saturation during the series of imbibition cycles, and stable nonzero residual Air Saturation only occurred when the initial Air Saturation of the imbibition process exceeded 0.49, ca. double the value of the main imbibition process. Once stable residual Air Saturation was obtained, all the subsequent residual Air Saturations remained stable and constant in the following imbibition cycles. Before this threshold point, the residual Air Saturation gradually fell given sufficient imbibition time. The results also indicate that the unstable and stable residual Air Saturations were mainly due to discrete pore-scale Air globules trapped in the interiors of pores and pore-network scale globules located in interconnected pores, respectively.