Groundwater contamination becomes a great concern in many countries. One of the most important pollutants is hydrocarbons. Sources of Hydrocarbons pollutants in Gazacan be a result of accidental spills of petroleum pr...Groundwater contamination becomes a great concern in many countries. One of the most important pollutants is hydrocarbons. Sources of Hydrocarbons pollutants in Gazacan be a result of accidental spills of petroleum products on the surface and uncontrolled disposal of wastewater. One of the common technologies for groundwater aquifer remediation from hydrocarbons is known as air sparging. In this study, a120 cm×100 cm×80 cmlaboratory scale aquifer model was implemented in order to investigate the effectiveness of air sparging technology in removal of petroleum products from contaminated site. Four pilot scale wells were installed at different depths and different spatial distribution. The central well was used for injecting air and the surrounding three wells were used for monitoring. The contaminated water and soil were tested for total organic carbon, lead, dissolved Oxygen and pH;one time before the start of treatment and four times through the treatment process. Total organic carbon in water and soil before air injection were 980 ppm and 0.08775 ppm, respectively. After air injection for three weeks (six hours daily) at flow rate range from 15 to20 L/min and at pressure range from 300 to 400 kPa, the concentration of pollutant was decreased to 4.0 ppm and 0.0 ppm in water and soil, respectively. Based on the results, it was clearly demonstrated that air sparging is a simple, effective and affordable technology that can be applied forGazaaquifer remediation in case of gasoline spill accidents.展开更多
A one-dimensional column is set up to study the mass transfer during air sparging process for methyl tertiary butyl ether（MTBE） removal in saturated soil and groundwater, with the condition of different airflow and ...A one-dimensional column is set up to study the mass transfer during air sparging process for methyl tertiary butyl ether（MTBE） removal in saturated soil and groundwater, with the condition of different airflow and soil penetrability. It is shown that the removal rate of MTBE can reach 80%, 90% and 95% when airflow is 0.05 m^3/h, 0. 085 m^3/h and 0. 10 m^3/h, respectively. Increasing airflow will help to increase the removal rate of dissolved MTBE, but eventually a threshold removal rate is reached, above which further increasing air injection rates does not increase the removal rate. Fine sand allows the injected air to travel in bubble form, while coarse sand and medium sand allow the injected air to travel in the form of discrete channels; the greater the soil grain size is, the more extensive the channel net work forms, which in turn leads to higher removal rate. A tailing effect of lingering residual contaminant concentrations occur within the fine sand. About 20% of MTBE cannot be removed.展开更多
In this study,a gravity-driven membrane(GDM)filtration system and hydroponic system(cultivating basil and lettuce)were combined for nutrient recovery from primary municipal wastewater.The GDM system was optimized by i...In this study,a gravity-driven membrane(GDM)filtration system and hydroponic system(cultivating basil and lettuce)were combined for nutrient recovery from primary municipal wastewater.The GDM system was optimized by increasing the periodic air sparging flow rate from 1 to 2 L/min(∼15 hr per 3-4 days),resulting in a∼52%reduction of irreversible fouling.However,the total fouling was not alleviated,and the water productivity remained comparable.The GDM-filtrated water was then delivered to hydroponic systems,and the effects of hydroponic operation conditions on plant growth and heavy metal uptake were evaluated,with fertilizer-and tap water-based hydroponic systems and soil cultivation sys-tem(with tap water)for comparison.It was found that(i)the hydroponic system under batchmode facilitated to promote vegetable growth with higher nutrient uptake rates com-pared to that under flow-through feed mode;(ii)a shift in nutrient levels in the hydroponic system could impact plant growth(such as plant height and leaf length),especially in the early stages.Nevertheless,the plants cultivated with the GDM-treated water had compara-ble growth profiles to those with commercial fertilizer or in soils.Furthermore,the targeted hazard quotient levels of all heavy metals for the plants in the hydroponic system with the treated water were greatly lower than those with the commercial fertilizer.Especially,com-pared to the lettuce,the basil had a lower heavy metal uptake capability and displayed a negligible impact on long-term human health risk,when the treated water was employed for the hydroponic system.展开更多
Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas ...Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.展开更多
Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configurat...Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configuration （a hollow half elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT＋2WHu） recommended in previous work has been used in this work. The operating temperatures were 24℃ and 81℃, identified as cold and hot respectively. The effects of superficial gas velocity, agitator speed and the corresponding power input on the local void fraction in two-phase systems are .investigated and discussed. Results show thatth-e increasing of agitator speed or gas flow rate leads to an increase in local-void fraction at the majority of measurement points in both cold and hot systems. However, the unifo,rmity of gas dispersion does not always in crease as the raising of agitator speed and power input. In either cold or hot sparged conditions, the two- and three-phase systems.have similar vertical profiles for void fraction, with maxima in similar locations; however, the void fractions are significantly lower in hot sparging than with cold. In cold operation the presence of particles leads to a lower void fraction at most points, although the local void fractions increase a little with the addition of solid particles at high temperature, in good agreement with the global gas holdup results, and the possible reasons are discussed in this paper. This work can give a better understanding of the differences between cold-gassed and hot-sparged three phase＇stirred tanks.展开更多
BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,...BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,BTEX in groundwater usually form non-aqueous phase liquid(NAPL) contaminants and exist in three phases:gas,aqueous and oil phase.Air sparging(AS) is an in situ treatment technology展开更多
Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the ...Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the saturated zone change, which may alter the flow path of the air. To understand better the particle movement, this study performed a sandbox test to estimate the soil porosity change during air sparging. A clear fracture was formed and the phenomenon of particle movement was observed when the air injection was started. The moved sand filled the porous around the fracture and the reparked sand filled the fracture, reducing the porosity around the fracture. The results obtained from the photographs of the sandbox, the current measurements and the direct sand sample measurements were close to each other and are credible. Therefore, air injection during air sparging causes sand particle movement of sand, altering the characteristic of the sand matrix and the air distribution.展开更多
Air sparging(AS) is an emerging method to remove VOCs from saturated soils and groundwater. Air sparging performance highly depends on the air distribution resulting in the aquifer. In order to study gas flow characte...Air sparging(AS) is an emerging method to remove VOCs from saturated soils and groundwater. Air sparging performance highly depends on the air distribution resulting in the aquifer. In order to study gas flow characterization, a two-dimensional experimental chamber was designed and installed. In addition, the method by using acetylene as the tracer to directly image the gas distribution results of AS process has been put forward. Experiments were performed with different injected gas flow rates. The gas flow patterns were found to depend significantly on the injected gas flow rate, and the characterization of gas flow distributions in porous media was very different from the acetylene tracing study. Lower and higher gas flow rates generally yield more irregular in shape and less effective gas distributions.展开更多
The TRU-Vision system,developed by Baker Hughes,analyzes the gas extracted from drilling mud to estimate the hydrocarbons composition in drilled rock formations.Several separation processes had been surveyed in order ...The TRU-Vision system,developed by Baker Hughes,analyzes the gas extracted from drilling mud to estimate the hydrocarbons composition in drilled rock formations.Several separation processes had been surveyed in order to enhance the gas extraction at the gas trap,namely,mechanical stirring,vacuum,air sparging,membrane separation processes,ultrasounds,and cyclones.Mechanical stirring devices(one propeller,one flat-blade turbine,and two baffles sets),a vacuum generator,and an air bubble generator were designed and assembled to increase the efficiency and the response stability of TRU-Vision system.展开更多
文摘Groundwater contamination becomes a great concern in many countries. One of the most important pollutants is hydrocarbons. Sources of Hydrocarbons pollutants in Gazacan be a result of accidental spills of petroleum products on the surface and uncontrolled disposal of wastewater. One of the common technologies for groundwater aquifer remediation from hydrocarbons is known as air sparging. In this study, a120 cm×100 cm×80 cmlaboratory scale aquifer model was implemented in order to investigate the effectiveness of air sparging technology in removal of petroleum products from contaminated site. Four pilot scale wells were installed at different depths and different spatial distribution. The central well was used for injecting air and the surrounding three wells were used for monitoring. The contaminated water and soil were tested for total organic carbon, lead, dissolved Oxygen and pH;one time before the start of treatment and four times through the treatment process. Total organic carbon in water and soil before air injection were 980 ppm and 0.08775 ppm, respectively. After air injection for three weeks (six hours daily) at flow rate range from 15 to20 L/min and at pressure range from 300 to 400 kPa, the concentration of pollutant was decreased to 4.0 ppm and 0.0 ppm in water and soil, respectively. Based on the results, it was clearly demonstrated that air sparging is a simple, effective and affordable technology that can be applied forGazaaquifer remediation in case of gasoline spill accidents.
基金Supported by National Natural Science Foundation of China(No. 20276048)
文摘A one-dimensional column is set up to study the mass transfer during air sparging process for methyl tertiary butyl ether（MTBE） removal in saturated soil and groundwater, with the condition of different airflow and soil penetrability. It is shown that the removal rate of MTBE can reach 80%, 90% and 95% when airflow is 0.05 m^3/h, 0. 085 m^3/h and 0. 10 m^3/h, respectively. Increasing airflow will help to increase the removal rate of dissolved MTBE, but eventually a threshold removal rate is reached, above which further increasing air injection rates does not increase the removal rate. Fine sand allows the injected air to travel in bubble form, while coarse sand and medium sand allow the injected air to travel in the form of discrete channels; the greater the soil grain size is, the more extensive the channel net work forms, which in turn leads to higher removal rate. A tailing effect of lingering residual contaminant concentrations occur within the fine sand. About 20% of MTBE cannot be removed.
文摘In this study,a gravity-driven membrane(GDM)filtration system and hydroponic system(cultivating basil and lettuce)were combined for nutrient recovery from primary municipal wastewater.The GDM system was optimized by increasing the periodic air sparging flow rate from 1 to 2 L/min(∼15 hr per 3-4 days),resulting in a∼52%reduction of irreversible fouling.However,the total fouling was not alleviated,and the water productivity remained comparable.The GDM-filtrated water was then delivered to hydroponic systems,and the effects of hydroponic operation conditions on plant growth and heavy metal uptake were evaluated,with fertilizer-and tap water-based hydroponic systems and soil cultivation sys-tem(with tap water)for comparison.It was found that(i)the hydroponic system under batchmode facilitated to promote vegetable growth with higher nutrient uptake rates com-pared to that under flow-through feed mode;(ii)a shift in nutrient levels in the hydroponic system could impact plant growth(such as plant height and leaf length),especially in the early stages.Nevertheless,the plants cultivated with the GDM-treated water had compara-ble growth profiles to those with commercial fertilizer or in soils.Furthermore,the targeted hazard quotient levels of all heavy metals for the plants in the hydroponic system with the treated water were greatly lower than those with the commercial fertilizer.Especially,com-pared to the lettuce,the basil had a lower heavy metal uptake capability and displayed a negligible impact on long-term human health risk,when the treated water was employed for the hydroponic system.
文摘Gas holdups in ambient gassed and hot sparged systems with multiple modern impellers and the effect of temperature on gas holdup are reported. The operating temperature has a great impact on gas holdup though the gas dispersion regime in the hot sparged system is similar to the ambient gassed condition. The gas holdup under the elevated temperature and the ambient gassed operation is successfully correlated. With the same total gas flow rate and power input, the gas holdup in the hot sparged system (say near the boiling point) is only about half of that in the ambient system. The results imply that almost all existing hot sparged reactors have been designed on the basis of incorrect estimates of the gas holdup during operation.
基金Supported by the National Natural Science Foundation of China （20576009, 20821004） and the National Basic Research Program of China （2007CB714300）. ACKNOWLEDGEMENTS The authors sincerely acknowledge the helpful discussion with Prof John M. Smith [Fluids and Systems Research Centre, School of Engineering （J2）, University of Surrey, Guildford, GU2 7XH, UK].
文摘Vertical distributions of void fraction in gas-liquid and gas-liquid-solid stirred tanks have been measured in a fully baffled dished base vessel of 0.48 m diameter, using a conductivity probe. The impeller configuration （a hollow half elliptical blade dispersing turbine below two up-pumping wide blade hydrofoils, identified as HEDT＋2WHu） recommended in previous work has been used in this work. The operating temperatures were 24℃ and 81℃, identified as cold and hot respectively. The effects of superficial gas velocity, agitator speed and the corresponding power input on the local void fraction in two-phase systems are .investigated and discussed. Results show thatth-e increasing of agitator speed or gas flow rate leads to an increase in local-void fraction at the majority of measurement points in both cold and hot systems. However, the unifo,rmity of gas dispersion does not always in crease as the raising of agitator speed and power input. In either cold or hot sparged conditions, the two- and three-phase systems.have similar vertical profiles for void fraction, with maxima in similar locations; however, the void fractions are significantly lower in hot sparging than with cold. In cold operation the presence of particles leads to a lower void fraction at most points, although the local void fractions increase a little with the addition of solid particles at high temperature, in good agreement with the global gas holdup results, and the possible reasons are discussed in this paper. This work can give a better understanding of the differences between cold-gassed and hot-sparged three phase＇stirred tanks.
文摘BTEX contaminants in groundwater seriously impact the ecological environment and human health that has become one of the urgent problems needed to be solved.Due to its low density,low solubility and strong volatility,BTEX in groundwater usually form non-aqueous phase liquid(NAPL) contaminants and exist in three phases:gas,aqueous and oil phase.Air sparging(AS) is an in situ treatment technology
文摘Air sparging is a remedial method for groundwater. The remedial region is similar to the air flow region in the saturated zone. If soil particles are transported during air sparging, the porosity distributions in the saturated zone change, which may alter the flow path of the air. To understand better the particle movement, this study performed a sandbox test to estimate the soil porosity change during air sparging. A clear fracture was formed and the phenomenon of particle movement was observed when the air injection was started. The moved sand filled the porous around the fracture and the reparked sand filled the fracture, reducing the porosity around the fracture. The results obtained from the photographs of the sandbox, the current measurements and the direct sand sample measurements were close to each other and are credible. Therefore, air injection during air sparging causes sand particle movement of sand, altering the characteristic of the sand matrix and the air distribution.
基金The National Natural Science Foundation of China(No. 20276048)
文摘Air sparging(AS) is an emerging method to remove VOCs from saturated soils and groundwater. Air sparging performance highly depends on the air distribution resulting in the aquifer. In order to study gas flow characterization, a two-dimensional experimental chamber was designed and installed. In addition, the method by using acetylene as the tracer to directly image the gas distribution results of AS process has been put forward. Experiments were performed with different injected gas flow rates. The gas flow patterns were found to depend significantly on the injected gas flow rate, and the characterization of gas flow distributions in porous media was very different from the acetylene tracing study. Lower and higher gas flow rates generally yield more irregular in shape and less effective gas distributions.
文摘The TRU-Vision system,developed by Baker Hughes,analyzes the gas extracted from drilling mud to estimate the hydrocarbons composition in drilled rock formations.Several separation processes had been surveyed in order to enhance the gas extraction at the gas trap,namely,mechanical stirring,vacuum,air sparging,membrane separation processes,ultrasounds,and cyclones.Mechanical stirring devices(one propeller,one flat-blade turbine,and two baffles sets),a vacuum generator,and an air bubble generator were designed and assembled to increase the efficiency and the response stability of TRU-Vision system.
