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Han Y, Xu J, Zhu L. Predicting soil concentrations and remediation target values of BTEX by an off-gas based mass transfer model. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 900:165731. [PMID: 37495150 DOI: 10.1016/j.scitotenv.2023.165731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/16/2023] [Revised: 07/18/2023] [Accepted: 07/20/2023] [Indexed: 07/28/2023]
Abstract
Soil vapor extraction (SVE) is a widely used technology for the remediation of volatile organic compounds (VOCs) contaminated soils. Residual concentrations of VOCs are crucial for assessing the SVE process and planning when to stop this process, however, the measurement of their residual concentrations in the soil is complicated. Herein, a pseudo-first-order sequential reaction model was established to predict the mass transfer of the BTEX (benzene, toluene, ethylbenzene, xylene) between the soil and off-gas during the SVE process. Based on this mass transfer model, the residual concentrations of BTEX in the soil during the trailing stage could be accurately estimated (R2 > 0.89) by their off-gas concentrations that were directly monitored in real time. Considering the removal efficiency and operating costs, a concept of the remediation target values (RTV) was proposed for the SVE technology, and its relevant model (R2 > 0.92, NRMSE = 6.4-16.8 %) was established based on the experimental data. The remediation endpoint can be further estimated based on the RTV with an overall accuracy of 84-100 %. These findings provide a simple and fast way to predict VOC concentrations in soil with easy-to-know factors and online monitoring of off-gas concentrations and will guide and optimize the SVE process toward more economical and efficient techniques for soil remediation.
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Affiliation(s)
- Yongxiang Han
- Department of Environmental Science, Zhejiang University, Hangzhou 310058, China
| | - Jiang Xu
- Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China
| | - Lizhong Zhu
- Department of Environmental Science, Zhejiang University, Hangzhou 310058, China; Zhejiang Provincial Key Laboratory of Organic Pollution Process and Control, Hangzhou 310058, China.
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Bai M, Liu Z, Zhan L, Yuan M, Yu H. Effect of pore size distribution and colloidal fines of porous media on the transport behavior of micro-nano-bubbles. Colloids Surf A Physicochem Eng Asp 2022. [DOI: 10.1016/j.colsurfa.2022.130851] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/29/2022]
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Xu L, Yan L, Zha F, Zhu F, Tan X, Kang B, Yang C, Lin Z. Remediation characteristics of surfactant-enhanced air sparging (SEAS) technology on volatile organic compounds contaminated soil with low permeability. JOURNAL OF CONTAMINANT HYDROLOGY 2022; 250:104049. [PMID: 35863213 DOI: 10.1016/j.jconhyd.2022.104049] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/20/2022] [Revised: 05/31/2022] [Accepted: 06/30/2022] [Indexed: 06/15/2023]
Abstract
Surfactant-enhanced air sparging (SEAS) is an effective technology for the remediation of volatile organic compounds contamination of medium and high-permeability soil, though applying SEAS to low-permeability soil contamination has rarely been explored. In this study, a series of two-dimensional physical model tests were designed to explore the feasibility and remediation characteristics of SEAS on low-permeability soil. In the test results, the incorporation and increase in surfactant concentration promoted air channel formation in the low-permeability soil, finally reduced the capillary breakthrough pressure and improved the airflow rate. The majority of the exhausted gaseous contaminants were distributed along the horizontal direction, differing from the results observed in medium and high-permeability soils. The exhausted gaseous contaminant concentration changed slightly when the sparging pressure and surfactant concentration increased at relatively low levels and increased as the sparging pressure and surfactant concentration increased further. Increasing the air sparging pressure without surfactant incorporation or with a low surfactant concentration cannot effectively remove the contaminant, while the removal efficiency can be enhanced with further increases in surfactant concentration. The discrete remediation characteristics had been confirmed during SEAS application on low-permeability soil, then the relationships between the ratios of remediation area and remediation extent under different surfactant concentrations and sparging pressures were established for remediation efficiency evaluation. Using this method, the discrete remediation characteristics can be recreated once the surfactant concentration and the sparging pressure were chosen. On the other side, targeted improvements in the remediation area or extent can be achieved by controlling the surfactant concentration and sparging pressure. Through this study, SEAS technology and the proposed evaluation method were successfully implemented in soil with hydraulic conductivity around 9E-7 m/s, which expanded the application scope of SEAS technology for contaminant removal.
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Affiliation(s)
- Long Xu
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Lixue Yan
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Fusheng Zha
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China.
| | - Fanghua Zhu
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Xiaohui Tan
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Bo Kang
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Chengbin Yang
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei 230009, China
| | - Zhiyue Lin
- NO. 327 Geological Team, Bureau of Geology and Mineral Exploration of Anhui Province, Hefei 230011, Anhui, China
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Yao M, Yuan Q, Qu D, Liu W, Zhao Y, Wang M. Effects of airflow rate distribution and nitrobenzene removal in an aquifer with a low-permeability lens during surfactant-enhanced air sparging. JOURNAL OF HAZARDOUS MATERIALS 2022; 437:129383. [PMID: 35728315 DOI: 10.1016/j.jhazmat.2022.129383] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/10/2022] [Revised: 06/01/2022] [Accepted: 06/12/2022] [Indexed: 06/15/2023]
Abstract
The application of surfactant-enhanced air sparging (SEAS) in heterogeneous aquifers has received increasing attention. In this study, a two-dimensional laboratory visualization device was used to study the migration and distribution mechanism of airflow and the nitrobenzene removal effect in an aquifer with a low-permeability lens during AS and SEAS. Experimental results showed that the surfactant significantly reduced the blocking effect of the geological interface on airflow, and the ΔPe (the air entry pressure difference between the background media and the lens) value of the geological interface decreased from 1.1 kPa to 0.3 kPa when the surfactant concentration was 800 mg/L. When the surfactant injection location was at the center of the lens and the injection volume was 1 PV (pore volume of the lens), part of the airflow entered the lens through its below interface, which clearly improved the nitrobenzene removal inside and above the lens compared with AS remediation. However, when SEAS remediation was 24 h, the surfactant redistribution caused by air sparging resulted in the airflow entering the lens to bypass the lens again, which changed the spatial distribution of airflow rate and was not conducive to the continuous removal of nitrobenzene inside the lens.
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Affiliation(s)
- Meng Yao
- School of Environmental and Safety Engineering, Changzhou University, Changzhou 213164, China; National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun 130021, China.
| | - Qian Yuan
- School of Environmental and Safety Engineering, Changzhou University, Changzhou 213164, China
| | - Dan Qu
- Baohang Environment Co.Ltd., Beijing 100036, China
| | - Wenjun Liu
- School of Environmental and Safety Engineering, Changzhou University, Changzhou 213164, China
| | - Yongsheng Zhao
- National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, Changchun 130021, China.
| | - Mingxin Wang
- School of Environmental and Safety Engineering, Changzhou University, Changzhou 213164, China.
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Yao M, Bai J, Yang X, Li X, Chang Y, Zhao Y. Effects of different permeable lenses on nitrobenzene transport during air sparging remediation in heterogeneous porous media. CHEMOSPHERE 2022; 296:134015. [PMID: 35182528 DOI: 10.1016/j.chemosphere.2022.134015] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/09/2021] [Revised: 02/12/2022] [Accepted: 02/14/2022] [Indexed: 06/14/2023]
Abstract
Air sparging (AS) is considered an effective remediation technology for groundwater contaminated by volatile organic compounds. However, the effects of AS remediation of heterogeneous aquifers with lenses of different permeability are still unclear, which limits the application of AS technology. In this study, the effects of different permeable lenses on nitrobenzene (NB) transport were quantitatively analysed by tracking the temporal and spatial evolutions of the NB concentration and using light transmission visualisation technology to observe airflow. Experimental results showed that the NB outside the airflow zone of the heterogeneous aquifer containing a gravel lens was rapidly removed, which is a special phenomenon. Through moisture content monitoring and colour tracer technology, the bubble-induced water circulation zone in a gravel lens was discovered during AS. At this time, the zone of influence (ZOI) included air flow zone and water circulation zone, while previous studies believed that the ZOI only contained the air flow zone. The presence of water circulation zone in the heterogeneous aquifer with a gravel lens increased the ZOI area and average contaminant removal flux by 5 and 2.3 times, respectively, compared with those in homogeneous aquifer. These findings have modified the conventional cognition about the ZOI and are conducive to an in-depth understanding of the remediation mechanisms and a better design of AS technology in heterogeneous aquifers with different permeable lenses.
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Affiliation(s)
- Meng Yao
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China; School of Environmental and Safety Engineering, Changzhou University, Changzhou, 213164, China; Jilin Provincial Key Laboratory of Water Resources and Environment, Jilin University, China; National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, No 2519 Jiefang Road, Chaoyang District, Changchun, Jilin, 130021, China.
| | - Jing Bai
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China; National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, No 2519 Jiefang Road, Chaoyang District, Changchun, Jilin, 130021, China
| | - Xinru Yang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China
| | - Xiaoyu Li
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China
| | - Yuehua Chang
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China
| | - Yongsheng Zhao
- Key Laboratory of Groundwater Resources and Environment, Ministry of Education, Jilin University, Changchun, 130021, China; National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Jilin University, No 2519 Jiefang Road, Chaoyang District, Changchun, Jilin, 130021, China.
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Chao JTH, Cahill AG, Lauer RM, Van De Ven CJC, Beckie RD. Propensity for fugitive gas migration in glaciofluvial deposits: An assessment of near-surface hydrofacies in the Peace Region, Northeastern British Columbia. THE SCIENCE OF THE TOTAL ENVIRONMENT 2020; 749:141459. [PMID: 33370906 DOI: 10.1016/j.scitotenv.2020.141459] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/20/2020] [Revised: 07/31/2020] [Accepted: 08/01/2020] [Indexed: 06/12/2023]
Abstract
Petroleum resource development has generated a global legacy of millions of active and decommissioned energy wells. Associated with this legacy are concerns about wellbore integrity failure and leakage of fugitive gas into groundwater and atmosphere. The fate of fugitive gas in the shallow subsurface is controlled by sediment heterogeneity, hydrostratigraphy and hydraulic connectivity. We characterized the shallow subsurface at a site in northeastern British Columbia, Canada; a region of extensive petroleum resource development. We collected 13 core profiles, 9 cone-penetrometer profiles, 58 sediment samples and 4 electrical resistivity profiles. At the site, a ~ 12 m thick layer of low-permeability diamict (10-8 m/s) overlays a more permeable (10-6 - 10-4 m/s) but highly heterogeneous sequence of glacigenic sand, clay and silt. We develop a conceptual hydrostratigraphic model for fluid flow in this system in the context of fugitive-gas migration. Driven by buoyancy forces, free-phase gas will move upward through discontinuous permeable zones within the Quaternary sediments, until it encounters lower permeability interbeds where it will pool, flow laterally or become trapped and dissolve into flowing groundwater. The vertical extent of gas migration will be significantly limited by the relatively continuous overlying diamict, a feature common across the Western Canadian Sedimentary Basin. However, intra-till lenses observed embedded within the diamict may provide pathways for gas to move vertically towards ground surface and into the atmosphere. This study provides one of the few investigations examining geological and hydrogeological heterogeneity in the shallow subsurface at scales relevant to gas migration. For glaciated regions with similar surficial geology, such as Western Canada Sedimentary Basin, gas that is released into the subsurface from an energy wellbore, below a surface diamict, will likely migrate laterally away from the wellbore, and be inhibited from reaching ground surface and emitting to atmosphere.
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Affiliation(s)
- Jessie Tse-Hua Chao
- Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada.
| | - Aaron G Cahill
- Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada; The Lyell Centre, Heriot-Watt University, Edinburgh, Scotland EH14 4AS, UK
| | - Rachel M Lauer
- Department of Geoscience, University of Calgary, Calgary, AB T2N 1N4, Canada
| | - Cole J C Van De Ven
- Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
| | - Roger D Beckie
- Earth, Ocean and Atmospheric Sciences, University of British Columbia, Vancouver, BC V6T 1Z4, Canada
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Van De Ven CJC, Mumford KG. Intermediate-Scale Laboratory Investigation of Stray Gas Migration Impacts: Transient Gas Flow and Surface Expression. ENVIRONMENTAL SCIENCE & TECHNOLOGY 2020; 54:12493-12501. [PMID: 32870667 DOI: 10.1021/acs.est.0c03530] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 06/11/2023]
Abstract
Petroleum resource development is a significant contributor of greenhouse gas emissions to the atmosphere. A potential source of emissions may result from stray gas migration. However, its contribution to overall emissions and potential groundwater contamination is unknown, and quantification of flow and dissolution of stray gas is required. The environmental expression of stray gas was investigated using an intermediate-scale (150 × 150 × 2 cm3), two-dimensional flow cell packed in both homogeneous and heterogeneous sand configurations allowing for visualization and measurement of gas movement, collection of aqueous samples, and real-time measurement of gas fluxes escaping the surface of the sand. Results show that gas is transported to the surface of the system via varying dominant discontinuous conduits for flow dictated by geology, leading to surface expression that can be greater or less than the leakage rate of gas. This suggests that surface expression is not directly indicative of the expanse and magnitude of stray gas migration leaks. It was found that 35-39% of the methane was released to the aqueous phase and 61-65% to the atmosphere. The results underscore that subsurface characteristics and gas flow are the key drivers for the overall expression of stray gas in unconsolidated sand aquifers.
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Affiliation(s)
- Cole J C Van De Ven
- Department of Civil Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada
| | - Kevin G Mumford
- Department of Civil Engineering, Queen's University, Kingston, Ontario K7L 3N6, Canada
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