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Geng Z, Zheng D, Qi Z, Xie Q, Li G, Zhang F. Direct current driven persulfate delivery and activation for heterogeneous porous media remediation: Coupling effects of electric-thermal-chemical-flow fields. JOURNAL OF HAZARDOUS MATERIALS 2024; 479:135743. [PMID: 39236534 DOI: 10.1016/j.jhazmat.2024.135743] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/05/2024] [Revised: 08/14/2024] [Accepted: 09/02/2024] [Indexed: 09/07/2024]
Abstract
Direct current (DC) has promising potential for persulfate delivery and activation in heterogeneous site remediation, yet requires deeper understanding. Here, we investigated the efficiency of DC for persulfate delivery and activation and compared with alternating current (AC). While AC electric field only influenced persulfate fate by Joule heating effect, DC electric field induced electrokinetic migration of persulfate and contaminants, as well as promoted persulfate activation with Joule heating and electrochemical reactions. DC system achieved 95 % MCB removal which was 3.1 times of that in AC system using the same voltage input (60 V) with a velocity of 0.5 m/d. When the applied DC voltage increased from 20 V to 60 V (0.5-1.5 V/cm), persulfate activation pathway changed from electrode reactions to the coupled activation pathways of electrode, chemical and heat reactions, thus resulting in increasing MCB removal efficiency from 57 % (20 V) to 95 % (40 V and 60 V). The energy consumption with 40 V (11.6 kWh/g) was 2.6 times of that using 20 V (4.4 kWh/g), and dramatically increased to 11.7 times with 60 V (50.2 kWh/g). This study provides a new perspective on improving the efficiency of persulfate delivery and activation in heterogeneous sites remediation using DC-driven system.
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Affiliation(s)
- Zhuning Geng
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Di Zheng
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Zhen Qi
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Qianli Xie
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Guanghe Li
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing 100015, PR China
| | - Fang Zhang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing 100015, PR China.
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2
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Cheng X, Jiang L, Liu W, Song X, Kumpiene J, Luo C. Phytoremediation of trichloroethylene in the soil/groundwater environment: Progress, problems, and potential. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 954:176566. [PMID: 39362566 DOI: 10.1016/j.scitotenv.2024.176566] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/08/2024] [Revised: 09/25/2024] [Accepted: 09/26/2024] [Indexed: 10/05/2024]
Abstract
Trichloroethylene (TCE) poses a significant environmental threat in groundwater and soil, necessitating effective remediation strategies. Phytoremediation offers a cost-effective and environmentally friendly approach to remediation. However, the mechanisms governing plant uptake, volatilisation, and degradation of TCE remain poorly understood. This review explores the mechanisms of TCE phytoremediation, metabolic pathways, and influencing factors, emphasizing future research directions to improve the understanding of TCE phytoremediation. The results showed that although the proportion of TCE phytovolatilisation is limited, it is important at sites chronically contaminated with TCE. The rhizosphere is a key microzone for pollutant redox reactions that significantly enhance its effectiveness when its characteristics are fully utilised and manipulated through reinforcement. Future research should focus on manipulating microbial communities through methods such as the application of endophytic bacteria and genetic modification. However, practical applications are in their infancy and further investigation is needed. Furthermore, many findings are based on non-uniform parameters or unstandardised methods, making them difficult to compare. Therefore, future studies should provide more standardised experimental parameters and employ accurate and standardised methods to develop suitable prediction models, enhancing data comparability and deepening our understanding of plant detoxification mechanisms.
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Affiliation(s)
- Xianghui Cheng
- State Key Laboratory of Organic Geochemistry and Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100039, China
| | - Longfei Jiang
- State Key Laboratory of Organic Geochemistry and Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100039, China
| | - Wuxing Liu
- CAS Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xin Song
- CAS Key Laboratory of Soil Environment & Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Jurate Kumpiene
- Department of Civil, Environmental and Natural Resources Engineering, Luleå University of Technology, Luleå 97187, Sweden
| | - Chunling Luo
- State Key Laboratory of Organic Geochemistry and Guangdong-Hong Kong-Macao Joint Laboratory for Environmental Pollution and Control, Guangzhou Institute of Geochemistry, Chinese Academy of Sciences, Guangzhou 510640, China; University of Chinese Academy of Sciences, Beijing 100039, China.
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Yang Z, Wei C, Sima J, Yan S, Yin L, Xian A, Wan J, Yang J, Song X. Quantitative sustainability assessment for in-situ electrical resistance heating coupled with steam enhanced extraction: An effective approach for the development of green remediation technologies. WATER RESEARCH 2024; 267:122450. [PMID: 39293344 DOI: 10.1016/j.watres.2024.122450] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/16/2024] [Revised: 08/23/2024] [Accepted: 09/13/2024] [Indexed: 09/20/2024]
Abstract
There is a lack of quantitative methodology for the sustainability assessment based on field data in the process of innovative technology development for groundwater remediation. This study developed a quantitative assessment framework, a model based on the life cycle assessment integrated with best management practices (LCA-BMPs), to evaluate the environmental, economic, and social sustainability of in-situ electrical resistance heating coupled with steam enhanced extraction (ERH-SEE), an innovative technology being demonstrated in the field. The results indicated that ERH-SEE offered better environmental sustainability performance compared to ERH only, with a reduction in carbon emissions by 52.6 %. ERH-SEE also significantly reduces human toxicity, resource consumption, and ecosystem impacts under the same remediation scenarios. The further assessment indicated that if taking the renewable energy share in energy structure in different countries into consideration, higher shares of renewable energy used in energy supplies can substantially reduce the environmental footprint of the studied scenarios. The economic sustainability assessment results showed that ERH-SEE was more sustainable than ERH only, as it reduces direct economic costs by 35.7 % and provides higher levels of worker employment. Regarding the social sustainability, ERH-SEE involved more complex operational procedures and presented more health risk exposure scenarios compared to ERH only, resulting in slightly more pronounced worker safety issues. Based on the final normalized results, the overall sustainability results of ERH-SEE and ERH only were 78.4 and 61.5, respectively, demonstrating that the sustainability performance of ERH-SEE was better than ERH only. It can be concluded that the application of ERH-SEE in groundwater remediation where significant heterogeneities occur in subsurface can increase the sustainability in developing countries, due to the lower percentage in renewable electricity in the energy supply. This study provided new insights into the technology development for the remediation of soil and groundwater contamination.
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Affiliation(s)
- Zongshuai Yang
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Changlong Wei
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China
| | - Jingke Sima
- Shanghai Academy of Environmental Science, Shanghai 200233, China
| | - Song Yan
- China State Science Dingshi Environmental Engineering Co., Ltd., Beijing 100073, China
| | - Lipu Yin
- China State Science Dingshi Environmental Engineering Co., Ltd., Beijing 100073, China
| | - Ao Xian
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China
| | - Jinzhong Wan
- State Environmental Protection Key Laboratory of Soil Environmental Management and Pollution Control, Nanjing Institute of Environmental Sciences, Ministry of Ecology and Environment, Nanjing 210042, China
| | - Jie Yang
- Shanghai Academy of Environmental Science, Shanghai 200233, China.
| | - Xin Song
- State Key Laboratory of Soil and Sustainable Agriculture, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 211135, China; University of Chinese Academy of Sciences, Beijing 100049, China.
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Huang W, Cao L, Ge R, Wan Z, Zheng D, Li F, Li G, Zhang F. Higher thermal remediation temperature facilitates the sequential bioaugmented reductive dechlorination. JOURNAL OF HAZARDOUS MATERIALS 2024; 475:134825. [PMID: 38876014 DOI: 10.1016/j.jhazmat.2024.134825] [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: 01/31/2024] [Revised: 05/07/2024] [Accepted: 06/03/2024] [Indexed: 06/16/2024]
Abstract
The coupling of thermal remediation with microbial reductive dechlorination (MRD) has shown promising potential for the cleanup of chlorinated solvent contaminated sites. In this study, thermal treatment and bioaugmentation were applied in series, where prior higher thermal remediation temperature led to improved TCE dechlorination performance with both better organohalide-respiring bacteria (OHRB) colonization and electron donor availability. The 60 °C was found to be a key temperature point where the promotion effect became obvious. Amplicon sequencing and co-occurrence network analysis demonstrated that temperature was a more dominating factor than bioaugmentation that impacted microbial community structure. Higher temperature of prior thermal treatment resulted in the decrease of richness, diversity of indigenous microbial communities, and simplified the network structure, which benefited the build-up of newcoming microorganisms during bioaugmentation. Thus, the abundance of Desulfitobacterium increased from 0.11 % (25 °C) to 3.10 % (90 °C). Meanwhile, released volatile fatty acids (VFAs) during thermal remediation functioned as electron donors and boosted MRD. Our results provided temperature-specific information on synergistic effect of sequential thermal remediation and bioaugmentation, which contributed to better implementation of the coupled technologies in chloroethene-impacted sites.
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Affiliation(s)
- Wan Huang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Lifeng Cao
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China; National Engineering Laboratory for Site Remediation Technologies, Beijing 100015, China; ZJU-Hangzhou Global Scientific and Technological Innovation Center, Zhejiang University, Hangzhou 311215, China
| | - Runlei Ge
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Ziren Wan
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Di Zheng
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Fangzhou Li
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China
| | - Guanghe Li
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China; National Engineering Laboratory for Site Remediation Technologies, Beijing 100015, China
| | - Fang Zhang
- State Key Joint Laboratory of Environment Simulation and Pollution Control, State Environment Protection Key Laboratory of Microorganism Application and Risk Control, School of Environment, Tsinghua University, Beijing 100084, China; National Engineering Laboratory for Site Remediation Technologies, Beijing 100015, China.
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5
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Kim J, Kaown D, Lee KK. Coupling of radon and microbial analysis for dense non-aqueous-phase liquid tracing and health risk assessment in groundwater under seasonal variations. JOURNAL OF HAZARDOUS MATERIALS 2024; 475:134939. [PMID: 38889466 DOI: 10.1016/j.jhazmat.2024.134939] [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: 02/04/2024] [Revised: 06/13/2024] [Accepted: 06/14/2024] [Indexed: 06/20/2024]
Abstract
Dense non-aqueous-phase liquids (DNAPLs) represent one of the most hazardous contaminants of groundwater, posing health risks to humans. Radon is generally used to trace DNAPLs; however, external factors, such as rainfall or stream water, can influence its efficacy. To overcome these limitations, this study pioneered the integration of radon and microbial community structures to explore DNAPL tracing and natural attenuation in the context of seasonal variations for human health risk assessments. The results showed that a radon tracer can estimate DNAPL saturation in the source zone, especially during the dry season when radon deficiency predominates. However, samples exhibited mixing effects during the wet season because of local precipitation. Moreover, bioremediation and low health risks were observed in the plume boundary zone, indicating that microbial dechlorination was a predominant factor determining these risks. The abnormal patterns of radon observed during the wet season can be elucidated by examining microbiological communities. Consequently, a combined approach employing radon and microbial analysis is advocated for the boundary zone, albeit with a less intensive management strategy, compared with that for the source zone. This novel coupling method offers a theoretical and practical foundation for managing DNAPL-contaminated groundwater.
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Affiliation(s)
- Jaeyeon Kim
- School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, the Republic of Korea
| | - Dugin Kaown
- School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, the Republic of Korea
| | - Kang-Kun Lee
- School of Earth and Environmental Sciences, Seoul National University, Seoul 08826, the Republic of Korea.
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Zheng D, Xie Q, Li F, Huang W, Qi Z, Dong J, Li G, Zhang F. Spatiotemporal dynamic temperature variation dominated by ion behaviors during groundwater remediation using direct current. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2024; 351:124091. [PMID: 38697248 DOI: 10.1016/j.envpol.2024.124091] [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: 02/26/2024] [Revised: 04/29/2024] [Accepted: 04/29/2024] [Indexed: 05/04/2024]
Abstract
Direct current (DC) electric field has shown promising performance in contaminated site remediation, in which the Joule heating effect plays an important role but has been previously underappreciated. This study focuses on the spatiotemporal characteristics and mechanism of temperature change in heterogeneous porous media with applied DC. The heating process can be divided into four phases: preferential heating of the low permeability zone (LPZ), rapid heating in the middle region, temperature drop and hot zone shift, and reheating. The dynamic ion behaviors with complex interplays among reactions, electrokinetic-driven migration, and mixed convection induced an uneven redistribution of ions and dominated the heating rate and temperature distribution. The concentration of major ions near the pH jump decreased to 1% of the initial value, even though ions were continuously pumped into the heating zone. This ion depletion caused a drop in current, heating rate, and temperature. Here ions cannot be delivered rapidly into the ion-depleted zone by electromigration due to the potential flattening in the surrounding region. The presence of LPZ intensified the nonuniformity of ion redistribution, where a regional focusing of water-soluble ions was observed, and weakened the temperature rebound compared with that using homogeneous sand. These results provide a new perspective on the regulation of DC heating in site remediation.
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Affiliation(s)
- Di Zheng
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China.
| | - Qianli Xie
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China
| | - Fangzhou Li
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China
| | - Wan Huang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China
| | - Zhen Qi
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China
| | - Jingqi Dong
- Center for Soil Protection and Landscape Design, Chinese Academy of Environmental Planning, Beijing, 100041, PR China
| | - Guanghe Li
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing, 100015, PR China
| | - Fang Zhang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing, 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing, 100015, PR China.
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7
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Li W, Zhang W, Dong J, Liang X, Sun C. Groundwater chlorinated solvent plumes remediation from the past to the future: a scientometric and visualization analysis. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2024; 31:17033-17051. [PMID: 38334923 DOI: 10.1007/s11356-024-32080-z] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/15/2023] [Accepted: 01/15/2024] [Indexed: 02/10/2024]
Abstract
Contamination of groundwater with chlorinated hydrocarbons has serious adverse effects on human health. As research efforts in this area have expanded, a large body of literature has accumulated. However, traditional review writing suffers from limitations regarding efficiency, quantity, and timeliness, making it difficult to achieve a comprehensive and up-to-date understanding of developments in the field. There is a critical need for new tools to address emerging research challenges. This study evaluated 1619 publications related to this field using VOSviewer and CiteSpace visual tools. An extensive quantitative analysis and global overview of current research hotspots, as well as potential future research directions, were performed by reviewing publications from 2000 to 2022. Over the last 22 years, the USA has produced the most articles, making it the central country in the international collaboration network, with active cooperation with the other 7 most productive countries. Additionally, institutions have played a positive role in promoting the publication of science and technology research. In analyzing the distribution of institutions, it was found that the University of Waterloo conducted the majority of research in this field. This paper also identified the most productive journals, Environmental Science & Technology and Applied and Environmental Microbiology, which published 11,988 and 3253 scientific articles over the past 22 years, respectively. The main technologies are bioremediation and chemical reduction, which have garnered growing attention in academic publishing. Our findings offer a useful resource and a worldwide perspective for scientists engaged in this field, highlighting both the challenges and the possibilities associated with addressing groundwater chlorinated solvent plumes remediation.
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Affiliation(s)
- Wenyan Li
- Jilin University Key Laboratory of Groundwater Resources and Environment of the Ministry of Education, Changchun, 130021, People's Republic of China
- Jilin University National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Changchun, 130021, People's Republic of China
| | - Weihong Zhang
- Jilin University Key Laboratory of Groundwater Resources and Environment of the Ministry of Education, Changchun, 130021, People's Republic of China.
- Jilin University National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Changchun, 130021, People's Republic of China.
| | - Jun Dong
- Jilin University Key Laboratory of Groundwater Resources and Environment of the Ministry of Education, Changchun, 130021, People's Republic of China
- Jilin University National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Changchun, 130021, People's Republic of China
| | - Xue Liang
- Jilin University Key Laboratory of Groundwater Resources and Environment of the Ministry of Education, Changchun, 130021, People's Republic of China
- Jilin University National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Changchun, 130021, People's Republic of China
| | - Chen Sun
- Jilin University Key Laboratory of Groundwater Resources and Environment of the Ministry of Education, Changchun, 130021, People's Republic of China
- Jilin University National and Local Joint Engineering Laboratory for Petrochemical Contaminated Site Control and Remediation Technology, Changchun, 130021, People's Republic of China
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Yue X, Shan Y, Zhang Y, Jiao W, Shen K. Heat and mass transfer induced by alternating current during desorption of PAHs from soil using electrical resistance heating. ENVIRONMENTAL MONITORING AND ASSESSMENT 2024; 196:135. [PMID: 38200165 DOI: 10.1007/s10661-023-12272-9] [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: 05/18/2023] [Accepted: 12/29/2023] [Indexed: 01/12/2024]
Abstract
The transfer of heat and contaminants by alternating current (AC) and the removal mechanism of polycyclic aromatic hydrocarbons (PAHs) in electrical resistance heating (ERH) need further study. The main factors affecting heat transfer and water evaporation in the ERH experiment were studied, and the desorption efficiency, temporal and spatial distribution and kinetic behavior under various conditions were analyzed. The results suggested that moisture content was a necessary condition to ensure effective heating of soil, and soil moisture content above 30% was recommended. Higher voltage intensity and/or ion concentration meant stronger input power, resulting in the rapider heating process and the shorter the boiling time. At a low desorption temperature (about 100°C), the Phe desorption mainly depended on the volatilization of surface Phe and the co-boiling of Phe-water. In ERH, the participation of AC would accelerate the diffusion of pollutants from the internal pores of soil particles and their redistribution with water phase, thus improving the Phe removed by co-boiling. It was noteworthy that AC just greatly promoted solid-liquid mass transfer, but it hardly promoted desorption directly, and the removal still depended on Phe-water co-boiling. The Phe desorption efficiency could be significantly improved from 14.0~18.4% to 59.6~70.8% under the combined action of current strengthening Phe diffusion and co-boiling. Thermogravimetric and product analysis confirmed that no new organic matter was generated, but only Phe entered the gas phase through phase change.
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Affiliation(s)
- Xiupeng Yue
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
| | - Yongping Shan
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Yaping Zhang
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China.
| | - Wentao Jiao
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, 100085, China
| | - Kai Shen
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing, 210096, China
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Yue X, Zhang Y, Shan Y, Shen K, Jiao W. Lab-scale transport and activation of peroxydisulfate for phenanthrene degradation in soil: A comprehensive assessment of the remediation process, soil environment and microbial diversity. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 901:165771. [PMID: 37532036 DOI: 10.1016/j.scitotenv.2023.165771] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/23/2023] [Revised: 07/23/2023] [Accepted: 07/23/2023] [Indexed: 08/04/2023]
Abstract
Electrokinetic transport followed by electrical resistance heating activation of peroxydisulfate is a novel in situ soil remediation method. However, the strategy of electrokinetic transport coupled with electrical resistance heating and the comprehensive evaluation of restored soil need to be further explored. In this study, a lab-scale simulation device for in situ electrokinetic transport coupled with electrical resistance heating activation of peroxydisulfate was constructed to monitor the transport and transfer of peroxydisulfate, target pollutants, and process parameters, and the physicochemical properties and bacterial community of treated soil were evaluated. The results showed that adding 10 wt% peroxydisulfate to both the anode and cathode resulted in the optimized transfer rate and cumulative concentration of peroxydisulfate under electrokinetics. After 8 h, the cumulative concentration of peroxydisulfate reached 66.15- 166.29 mmol L-1, which was attributed to the migration of a large amount of S2O82- from the cathode to the soil under electromigration. Additionally, the anodic interfacial electric potential was improved, which was more conducive to electroosmotic transport of peroxydisulfate from the anode chamber. By alternating electrokinetic transport and electrical resistance heating activation of peroxydisulfate for two cycles, the phenanthrene degradation efficiency in four evenly distributed wells between electrodes reached 75.4 %, 87.6 %, 92.3 %, and 94.4 %. With slight variations in soil morphology and structure, the electrokinetic transport coupled with electrical resistance heating activation of peroxydisulfate elevated the soil fertility index. The abundance and diversity of bacterial communities in treated soil recovered to above the original soil level after 15 days. Our findings may support the application of electrokinetic transport coupled with electrical resistance heating activation of peroxydisulfate as a promising green ecological technology for the in situ remediation of organic-contaminated soil.
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Affiliation(s)
- Xiupeng Yue
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China
| | - Yaping Zhang
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China.
| | - Yongping Shan
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
| | - Kai Shen
- Key Laboratory of Energy Thermal Conversion and Control, Ministry of Education, School of Energy and Environment, Southeast University, Nanjing 210096, China
| | - Wentao Jiao
- Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing 100085, China
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Chu L, Cang L, Sun Z, Wang X, Chen H, Fang G, Gao J. Mechanism of nitro-byproducts formation during persulfate-based electrokinetic in situ oxidation for remediation of anthracene contaminated soil. JOURNAL OF HAZARDOUS MATERIALS 2023; 453:131396. [PMID: 37058937 DOI: 10.1016/j.jhazmat.2023.131396] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/29/2023] [Revised: 03/28/2023] [Accepted: 04/08/2023] [Indexed: 06/19/2023]
Abstract
Persulfate-based electrokinetic (EK) chemical oxidation appears to be a novel and viable strategy for the in situ remediation of polycyclic aromatic hydrocarbons (PAHs) polluted soil; however, the possible toxic byproducts of PAHs have been overlooked. In this study, we systematically investigated the formation mechanism of the nitro-byproducts of anthracene (ANT) during the EK process. Electrochemical experiments revealed that NH4+ and NO2- originating from nitrate electrolyte or soil substrates were oxidized to NO2• and NO• in the presence of SO4•-. Liquid chromatography quadrupole time-of-flight mass spectrometry (LC-QTOF-MS/MS) analysis with 15N labeling revealed the formation of nitro-byproducts (14 kinds), including 1-hydroxy-4-nitro-anthraquinone and its similar derivatives, 4-nitrophenol, and 2,4-dinitrophenol. The nitration pathways of ANT have been proposed and described, mainly including the formation of hydroxyl-anthraquinone-oxygen and phenoxy radicals and the subsequent addition of NO2• and NO•. ANT-based formation of nitro-byproducts during EK, which is usually underestimated, should be further investigated due to their enhanced acute toxicity, mutagenic effects, and potential threat to the ecosystem.
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Affiliation(s)
- Longgang Chu
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Long Cang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Zhaoyue Sun
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Xinghao Wang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Hong Chen
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Guodong Fang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Juan Gao
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences Nanjing College, Nanjing 210008, China.
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11
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Xie Q, Mumford KG, Kueper BH. Simulating field-scale thermal conductive heating with the potential for the migration and condensation of vapors. JOURNAL OF HAZARDOUS MATERIALS 2023; 453:131439. [PMID: 37088018 DOI: 10.1016/j.jhazmat.2023.131439] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/26/2023] [Revised: 04/09/2023] [Accepted: 04/16/2023] [Indexed: 05/03/2023]
Abstract
Thermal conductive heating (TCH) is an in-situ thermal treatment (ISTT) technology for treating non-aqueous phase liquid (NAPL) source zones. Numerical models can be useful tools for improving remedial performance, but traditional multiphase flow models are rarely used to simulate mass recovery during ISTT applications at the field scale due to their computational expense. This study developed a 3D model based on macroscopic invasion percolation to simulate the vaporization of NAPL, and the subsequent vapor migration and potential condensation at the field scale. The model was used to simulate the mass recovery of trichloroethene (TCE) from a NAPL source zone under seven scenarios of different heater placements, including three scenarios with an undersized target treatment zone (TTZ). Simulation results showed that TCH was effective in removing NAPL within the TTZ, but the treatment zone did not extend far from the perimeter heaters. In addition, during heating, NAPL condensation outside the TTZ due to the escaping vapor was observed in all scenarios. Overall, the resulting mass recovery was lower in the three scenarios with an undersized TTZ (91-95%) than in the other four scenarios (≈ 99%). Moreover, the locations of unrecovered/condensed NAPL could be inferred by monitoring mass recovery tailing at individual extraction wells.
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Affiliation(s)
- Qianli Xie
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada.
| | - Kevin G Mumford
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada
| | - Bernard H Kueper
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada
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12
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Wen D, Liu H, Zhang Y, Fu R. Electrokinetically-delivered persulfate and pulsed direct current electric field induced transport, mixing and thermally activated in situ for remediation of PAHs contaminated soil. JOURNAL OF HAZARDOUS MATERIALS 2023; 444:130414. [PMID: 36413897 DOI: 10.1016/j.jhazmat.2022.130414] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 07/11/2022] [Revised: 11/10/2022] [Accepted: 11/14/2022] [Indexed: 06/16/2023]
Abstract
Herein, we proposed and proved a novel strategy that enhanced the delivery of persulfate (PS) to soil by electrokinetics (EK), and then applying a pulsed direct current (DC) electric field thermally activated the PS in situ, and synchronously promoted PS plume mixing, contaminants-free radicals reaction and continued to replenish PS to the soil, to achieve efficient degradation of contaminants in low permeability zones. Results showed that transport rate of PS in tested soil by EK was approximately 12.3 times than diffusion. Applying an irregular pulsed DC field maintained the targeted temperature (30-50 ℃) during activation phase, and generated two oxidative radicals (SO4∙-/∙OH). Concurrently, in the case, electromigration and electroosmosis have promoted the PS transport and the reactive mixing of PS/free radicals with polycyclic aromatic hydrocarbons (PAHs) contaminated soil and enhance the PAHs degradation. PS concentrations in pore fluid was characterized by an increase accompanied by continuous fluctuations. Eventually, in case of the long-term low-temperature activation (i.e., 30-40 ℃), a significant decreases (nearly 60%) in average concentration of PAHs in the whole soil cell was observed over 10 days. These results demonstrates that the novel strategy has great potentiality in the remediation of low permeability contaminated soil.
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Affiliation(s)
- Dongdong Wen
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Centre for Environmental Risk Management & Remediation of Soil & Groundwater, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Huaqiu Liu
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Centre for Environmental Risk Management & Remediation of Soil & Groundwater, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Yajun Zhang
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Centre for Environmental Risk Management & Remediation of Soil & Groundwater, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China
| | - Rongbing Fu
- State Key Laboratory of Pollution Control and Resource Reuse, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Centre for Environmental Risk Management & Remediation of Soil & Groundwater, College of Environmental Science and Engineering, Tongji University, Shanghai 200092, China; Shanghai Institute of Pollution Control and Ecological Security, Shanghai 200092, China.
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13
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Zhao S, Zhang J, Feng SJ. The era of low-permeability sites remediation and corresponding technologies: A review. CHEMOSPHERE 2023; 313:137264. [PMID: 36400189 DOI: 10.1016/j.chemosphere.2022.137264] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/02/2022] [Revised: 11/13/2022] [Accepted: 11/14/2022] [Indexed: 06/16/2023]
Abstract
Rational utilization of soil resources and remediation of contaminated soils are imperative due to the rapidly growing demand for clean soils. Currently, many in-situ remediation technologies are less suitable at low-permeability sites due to the limitations of soil permeability. This work defines a low-permeability site as a site with hydraulic conductivity less than 10-4 cm/s, and summarizes the migration characteristics of representative contaminants at low-permeability sites, and discusses the principles and practical applications of different technologies suitable for the remediation of low-permeability sites, including electrokinetic remediation technology, polymer flushing technology, fracturing technology, and in-situ thermal remediation technology. Enhanced and combined remediation technologies are further described because one remediation technology cannot remediate all contaminants. The prospects for the application of remediation technologies to low-permeability sites are also proposed. This work highlights the necessity of low-permeability sites remediation and the urgent need for new remediation technologies, with the hope to inspire future research on low-permeability sites.
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Affiliation(s)
- Shan Zhao
- College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai, 201306, China; College of Civil Engineering, Tongji University, Shanghai, 200092, China
| | - Jian Zhang
- College of Ocean Science and Engineering, Shanghai Maritime University, Shanghai, 201306, China
| | - Shi-Jin Feng
- College of Civil Engineering, Tongji University, Shanghai, 200092, China.
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14
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Li JP, Zhao W, Li SH, Yang XJ, Lyu SG, Liu YD, Wang HL. A novel hydrocyclone for use in underground DNAPL phase separation. THE SCIENCE OF THE TOTAL ENVIRONMENT 2022; 842:156866. [PMID: 35753481 DOI: 10.1016/j.scitotenv.2022.156866] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/01/2022] [Revised: 06/16/2022] [Accepted: 06/17/2022] [Indexed: 06/15/2023]
Abstract
Halogenated organic solvents are the most commonly detected pollutants in groundwater and are particularly toxic and harmful. How to separate these dense nonaqueous phase liquid (DNAPL) pollutants efficiently from groundwater has become an important research question. Here, a novel hydrocyclone with annular overflow structure was designed, which eliminated the short-circuit flow of the traditional hydrocyclone and solved the problem of overflow entrainment caused by the enrichment of droplets near the locus of zero vertical velocities (LZVV) into turbulence. The flow field characteristics of this novel hydrocyclone were studied using Computational Fluid Dynamics (CFD) simulation and compared with the traditional hydrocyclone. It was found that the annular gap structure of the novel hydrocyclone increased the tangential velocity of the outer vortex. Moreover, the radius of the LZVV was expanded outward by 0.17 mm, which reduced the possibility of droplets with small particle sizes in the second phase escaping from the overflow pipe. The collective effect was to eliminate the short-circuit flow. This novel hydrocyclone was able to separate DNAPL pollutants with low consumption and high efficiency, across a range of inlet velocity from 4 to 6 m/s. The maximum separation efficiency was 99.91 %. In addition, with trichloroethylene (TCE) as the target pollutant, the maximum volume fraction of the dispersed phase in the hydrocyclone was located on the side wall of the hydrocyclone. Taken together, we believe that this work will provide a low-cost, efficient separation method for the separation of groundwater- contaminated liquid mixtures. Furthermore, it has broad application prospects in the field of heterotopic remediation of groundwater.
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Affiliation(s)
- Jian-Ping Li
- National Engineering Laboratory for High Concentration Refractory Organic Wastewater Treatment Technology, East China University of Science and Technology, Shanghai 200237, China.
| | - Wei Zhao
- School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Shi-Hao Li
- School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Xue-Jing Yang
- School of Mechanical and Power Engineering, East China University of Science and Technology, Shanghai 200237, China
| | - Shu-Guang Lyu
- National Key Laboratory of Environmental Risk Assessment and Control for Chemical Processes in Environmental Protection, East China University of Science and Technology, 200237, China
| | - Yong-di Liu
- National Engineering Laboratory for High Concentration Refractory Organic Wastewater Treatment Technology, East China University of Science and Technology, Shanghai 200237, China
| | - Hua-Lin Wang
- National Engineering Laboratory for High Concentration Refractory Organic Wastewater Treatment Technology, East China University of Science and Technology, Shanghai 200237, China
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15
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Zheng D, Geng Z, Huang W, Cao L, Wan Z, Li G, Zhang F. Enhanced semi-volatile DNAPL accessibility at sub-boiling temperature during electrical resistance heating in heterogeneous porous media. JOURNAL OF HAZARDOUS MATERIALS 2022; 439:129633. [PMID: 35882169 DOI: 10.1016/j.jhazmat.2022.129633] [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: 04/26/2022] [Revised: 07/01/2022] [Accepted: 07/16/2022] [Indexed: 06/15/2023]
Abstract
Successful remediation of semi-volatile contaminants using electrical resistance heating (ERH) coupled technologies requires a deep understanding of contaminant migration and accessibility, especially with stratigraphic heterogeneity and dense nonaqueous phase liquid (DNAPL) occurrence. Here, we chose nitrobenzene (NB) as a model contaminant of semi-volatile DNAPL and uniquely demonstrated that temperature variation during ERH could induce NB DNAPL migration out of the low permeability zone (LPZ) even below water boiling temperature. When heating the system using alternating current (AC) of 140 V to a temperature range of 50-79 °C, obvious DNAPL migration was visually observed. The upward migration of DNAPL would considerably increase the mass of accessible contaminant by other remediation measures. The downstream cumulative NB mass of 1092 mg in 140 V system raised 56-folds compared to that of 19 mg in the control experiment with only groundwater flow. This migration was mainly attributed to a complex natural convection caused by temperature gradient. Comparing with traditional AC heating, ERH powered by pulsed direct current (PDC-ERH) showed a higher and more uneven heating pattern, resulting in a stronger convection at the same voltage that enhanced the DNAPL migration out of LPZ. These results revealed the importance of natural convection in the ERH process, which could be further optimized to improve the energy efficiency of remediation.
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Affiliation(s)
- Di Zheng
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Zhuning Geng
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Wan Huang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Lifeng Cao
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Ziren Wan
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China
| | - Guanghe Li
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing 100015, PR China
| | - Fang Zhang
- School of Environment and State Key Joint Laboratory of Environment Simulation and Pollution Control, Tsinghua University, Beijing 100084, PR China; National Engineering Laboratory for Site Remediation Technologies (NEL-SRT), Beijing 100015, PR China.
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16
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Wang Q, Guo S, Ali M, Song X, Tang Z, Zhang Z, Zhang M, Luo Y. Thermally enhanced bioremediation: A review of the fundamentals and applications in soil and groundwater remediation. JOURNAL OF HAZARDOUS MATERIALS 2022; 433:128749. [PMID: 35364527 DOI: 10.1016/j.jhazmat.2022.128749] [Citation(s) in RCA: 24] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/27/2022] [Revised: 03/11/2022] [Accepted: 03/18/2022] [Indexed: 06/14/2023]
Abstract
Thermally enhanced bioremediation (TEB), a new concept proposed in recent years, explores the combination of thermal treatment and bioremediation to address the challenges of the low efficiency and long duration of bioremediation. This study presented a comprehensive review regarding the fundamentals of TEB and its applications in soil and groundwater remediation. The temperature effects on the bioremediation of contaminants were systematically reviewed. The thermal effects on the physical, chemical and biological characteristics of soil, and the corresponding changes of contaminants bioavailability and microbial metabolic activities were summarized. Specifically, the increase in temperature within a suitable range can proliferate enzymes enrichment, extracellular polysaccharides and biosurfactants production, and further enhancing bioremediation. Furthermore, a systematic evaluation of TEB applications by utilizing traditional in situ heating technologies, as well as renewable energy (e.g., stored aquifer thermal energy and solar energy), was provided. Additionally, TEB has been applied as a biological polishing technology post thermal treatment, which can be a cost-effective method to address the contaminants rebounds in groundwater remediation. However, there are still various challenges to be addressed in TEB, and future research perspectives to further improve the basic understanding and applications of TEB for the remediation of contaminated soil and groundwater are presented.
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Affiliation(s)
- Qing Wang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Siwei Guo
- Zhejiang University, Hangzhou, China
| | - Mukhtiar Ali
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Xin Song
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China.
| | - Zhiwen Tang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Zhuanxia Zhang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
| | - Meng Zhang
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China
| | - Yongming Luo
- Key Laboratory of Soil Environment and Pollution Remediation, Institute of Soil Science, Chinese Academy of Sciences, Nanjing 210008, China; University of Chinese Academy of Sciences, Beijing 100049, China
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17
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Mumford KG, Martin EJ, Kueper BH. Removal of trichloroethene from thin clay lenses by electrical resistance heating: Laboratory experiments and the effects of gas saturation. JOURNAL OF CONTAMINANT HYDROLOGY 2021; 243:103892. [PMID: 34634516 DOI: 10.1016/j.jconhyd.2021.103892] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/04/2021] [Revised: 07/28/2021] [Accepted: 09/21/2021] [Indexed: 06/13/2023]
Abstract
The removal of dissolved volatile organic compounds (VOCs) from low-permeability lenses is important to limit back diffusion at sites impacted by dense non-aqueous phase liquids (DNAPLs). In situ thermal treatment (ISTT) technologies have the potential to treat DNAPL-impacted sites by enhancing diffusion from low-permeability lenses during heating. A series of two-dimensional laboratory tank experiments was conducted to investigate heating, gas formation, and trichloroethene (TCE) removal from a clay lens surrounded by sand. Results showed preferential heating of the clay and substantial TCE removal, with post-heating relative concentrations less than 0.06. The extent of TCE removal was not explained by only an increase in the aqueous TCE diffusion coefficient with increased temperature. Modelling estimates based on 1D diffusion from the lens showed that diffusion through both gas and water phases was required to match observations. Gas formation in the interior of the lens was also indicated by measured changes in bulk electrical conductivity of the clay during cool down, with gas saturations estimated to be greater than 0.21 at the end of heating. These estimates were larger than those needed to match the observed removal by diffusion, and suggest that connected gas pathways were created in the lens during heating, but that not all of the gas produced was part of those pathways. These results suggest that ISTT technologies may be effective in removing dissolved VOCs from thin clay lenses, and that gas formation within the clay should be considered when predicting the extent and rate of removal.
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Affiliation(s)
- Kevin G Mumford
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada.
| | - Eric J Martin
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada
| | - Bernard H Kueper
- Queen's University, Department of Civil Engineering, Kingston, Ontario K7L 3N6, Canada
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