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Li G, Liu S, Jiao W, Feng S, Zhan L, Chen Y. Numerical investigation and optimal design of capillary barrier cover with passive gas collection pipes on the performance at limiting landfill gas emissions. THE SCIENCE OF THE TOTAL ENVIRONMENT 2024; 927:172421. [PMID: 38614334 DOI: 10.1016/j.scitotenv.2024.172421] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/04/2024] [Revised: 04/06/2024] [Accepted: 04/10/2024] [Indexed: 04/15/2024]
Abstract
Relying solely on soil properties may not fully ensure the performance of capillary barrier covers at limiting landfill gas (LFG) emissions. This study proposed to install passive gas collection pipes in the coarse-grained soil layers of capillary barrier covers to enhance their performance at limiting LFG emissions. First, the LFG generation rate of municipal solid waste and its influencing factors were analyzed based on empirical formulas. This information provided necessary bottom boundary conditions for the analyses of LFG transport through capillary barrier covers with passive gas collection pipes (CBCPPs). Then, numerical simulations were conducted to investigate the LFG transport properties through CBCPPs and reveal relevant influencing factors. Finally, practical suggestions were proposed to optimize the design of CBCPPs. The results indicated that the maximum whole-site LFG generation rate occurred at the end of landfilling operation. The gas collection efficiency (E) of CBCPPs was mainly controlled by the ratio of the intrinsic permeability between the coarse- and fine-grained soil (K2/K1) and the laying spacing between gas collection pipes (D). E increased as K2/K1 increased but decreased as D increased. An empirical expression for estimating E based on K2/K1 and D was proposed. In practice, CBCPPs were supposed to be constructed once the landfilling operation finished. It is best to select the fine- and coarse-grained soils with K2/K1 exceeding 10,000 to construct CBCPPs.
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Affiliation(s)
- Guangyao Li
- Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China; Chongqing Research Institute, Beijing University of Technology, Chongqing 401151, China; MOE Key Laboratory of Soft Soils and Environmental Engineering, Zhejiang University, Hangzhou 310058, China
| | - Sida Liu
- Key Laboratory of Urban Security and Disaster Engineering of Ministry of Education, Beijing University of Technology, Beijing 100124, China; Chongqing Research Institute, Beijing University of Technology, Chongqing 401151, China
| | - Weiguo Jiao
- School of Civil Engineering, Guizhou Institute of Technology, Guiyang 550003, China
| | - Song Feng
- College of Civil Engineering, Fuzhou University, Fuzhou 350108, China.
| | - Liangtong Zhan
- MOE Key Laboratory of Soft Soils and Environmental Engineering, Zhejiang University, Hangzhou 310058, China
| | - Yunmin Chen
- MOE Key Laboratory of Soft Soils and Environmental Engineering, Zhejiang University, Hangzhou 310058, China
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2
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Huang D, Chen Y, Bai X, Zhang R, Chen Q, Wang N, Xu Q. Methane removal efficiencies of biochar-mediated landfill soil cover with reduced depth. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2024; 355:120487. [PMID: 38422848 DOI: 10.1016/j.jenvman.2024.120487] [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: 10/31/2023] [Revised: 02/15/2024] [Accepted: 02/21/2024] [Indexed: 03/02/2024]
Abstract
Biochar amendment for landfill soil cover has the potential to enhance methane removal efficiency while minimizing the soil depth. However, there is a lack of information on the response of biochar-mediated soil cover to the changes in configuration and operational parameters during the methane transport and transformation processes. This study constructed three biochar-amended landfill soil covers, with reduced soil depths from 75 cm (C2) to 55 cm (C3) and 45 cm (C4), and the control group (C1) with 75 cm and no biochar. Two operation phases were conducted under two soil moisture contents and three inlet methane fluxes in each phase. The methane removal efficiency increased for all columns along with the increase in methane flux. However, increasing moisture content from 10% to 20% negatively influenced the methane removal efficiency due to mass transfer limitation when at a low inlet methane flux, especially for C1; while this adverse effect could be alleviated by a high flux. Except for the condition with low moisture content and flux combination, C3 showed comparable methane removal efficiency to C2, both dominating over C1. As for C4 with only 45 cm, a high moisture content combined with a high methane flux enabled its methane removal efficiency to be competitive with other soil depths. In addition to the geotechnical reasons for gas transport processes, the evolution in methanotroph community structure (mainly type I methanotrophs) induced by biochar amendment and variations in soil properties supplemented the biological reasons for the varying methane removal efficiencies.
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Affiliation(s)
- Dandan Huang
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China; School of Ecology, Sun Yat-sen University, No. 66, Gongchang Road, Guangming District, Shenzhen, 0020518107, China
| | - Yuke Chen
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China
| | - Xinyue Bai
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China
| | - Rujie Zhang
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China
| | - Qindong Chen
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China
| | - Ning Wang
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China
| | - Qiyong Xu
- Shenzhen Engineering Laboratory for Eco-efficient Recycled Materials, School of Environment and Energy, Peking University Shenzhen Graduate School, University Town, Xili, Nanshan District, Shenzhen, 518055, China.
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Wang Q, Xie H, Peng Y, Mohammad A, Singh DN. VOCs emission from a final landfill cover system induced by ground surface air temperature and barometric pressure fluctuation. ENVIRONMENTAL POLLUTION (BARKING, ESSEX : 1987) 2023; 336:122391. [PMID: 37633438 DOI: 10.1016/j.envpol.2023.122391] [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: 05/22/2023] [Revised: 07/17/2023] [Accepted: 08/12/2023] [Indexed: 08/28/2023]
Abstract
Volatile organic compounds (VOCs) emission flux and their concentration profiles were measured at a final municipal solid waste (MSW) landfill cover in Hangzhou, China. The influencing parameters, especially ground surface air temperature and pressure were monitored concomitantly. Furthermore, a numerical model incorporating coupled thermo-hydro-chemical interaction to assess VOCs emission from this final landfill cover (LFC) system was developed and validated with the field test results. The tested total VOC emission flux from the final cover is 0.0124 μg/m2/s, which indicates that the total amount of VOCs emitted into the atmosphere is 391 mg/m2 annually. Among these, dichloromethane (DCM) dominated VOCs emission flux during May, comprising 51.8% of the total emission flux. The numerical simulation results indicated that the diffusive emission flux of VOCs varied consistently with the fluctuation of atmospheric temperature. Whereas, the advective flux varied inversely with the fluctuation of barometric pressure. The highest difference in diffusive emission flux induced by temperature variation is 183 μg/m2/day and occurred in spring. Moreover, the results demonstrated that the impact of atmospheric temperature and pressure fluctuation on the emission of VOC from final covers is non-negligible when reasonably assessing the risks of landfill and landfill gas emission budget.
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Affiliation(s)
- Qiao Wang
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China
| | - Haijian Xie
- College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, 310058, China; Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China.
| | - Yingfei Peng
- College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, 310058, China
| | - Arif Mohammad
- School of Engineering, Cardiff University, Queen's Buildings, The Parade Cardiff CF24 3AA, UK
| | - Devendra Narain Singh
- Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
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Ma J, Gu Y, Liu L, Zhang Y, Wei M, Jiang A, Liu X, He C. Study on the effect of landfill gas on aerobic municipal solid waste degradation: Lab-scale model and tests. THE SCIENCE OF THE TOTAL ENVIRONMENT 2023; 869:161875. [PMID: 36709894 DOI: 10.1016/j.scitotenv.2023.161875] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Revised: 01/11/2023] [Accepted: 01/24/2023] [Indexed: 06/18/2023]
Abstract
Aeration is of great importance in landfill remediation. However, most existing studies on aerobic waste degradation ignore the presence of landfill gases. In this study, gas characteristics during aerobic waste degradation in the presence of landfill gas in lab-scale lysimeters were investigated. Oxygen (O2) was intermittently injected into municipal solid waste. Changes in the gas concentration and reaction rate of methane (CH4), carbon dioxide (CO2), and O2 during the reaction process were monitored and calculated. The results showed that all reactions, including aerobic degradation, CH4 oxidation, and anaerobic waste degradation, occurred simultaneously during landfill aeration. The maximum O2 consumption rate was 0.013 mol day-1 kg-1 dry waste. CH4 production was stimulated after the O2 content was insufficient to sustain the aerobic environment. Higher CH4 production was likely attributed to the remaining substrate and biomass from dead aerobic microorganisms decomposed by growing anaerobic microorganisms. Based on the biochemical reaction and principle of mass conservation, a gas balance model during waste aeration was established to analyze the proportions of aerobic waste degradation, CH4 oxidation, and anaerobic waste degradation. The CH4 oxidation reaction was more advantageous than the aerobic waste degradation reaction during aeration. With an increase in gas injection times, the anaerobic reaction gradually weakened. The maximum proportion of CH4 oxidation reaction could achieve at 21.4 % during aeration, which is of great significance for the waste degradation reaction. The maximum proportion of aerobic waste degradation and the minimum proportion of anaerobic waste degradation were approximately 16.0 % and 74.2 %, respectively. The results show that landfill gas should be considered in the progress of landfill aeration. This study provides a novel approach for calculating the proportion of reactions during landfill aeration, which deepens the understanding of the reaction process and contributes to the design of aerobic landfill projects.
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Affiliation(s)
- Jun Ma
- Department of Civil Engineering, Dalian Maritime University, Dalian 116026, China
| | - Yuqi Gu
- Department of Civil Engineering, Dalian Maritime University, Dalian 116026, China
| | - Lei Liu
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; IRSM-CAS/HK PolyU Joint Laboratory on Solid Waste Science, Wuhan 430071, China; Hubei Province Key Laboratory of Contaminated Sludge and Soil Science and Engineering, Wuhan 430071, China.
| | - Yi Zhang
- State Key Laboratory of Freshwater Ecology and Biotechnology, Institute of Hydrobiology, Chinese Academy of Sciences, Wuhan 430072, China
| | - Mingli Wei
- State Key Laboratory of Geomechanics and Geotechnical Engineering, Institute of Rock and Soil Mechanics, Chinese Academy of Sciences, Wuhan 430071, China; Jiangsu Institute of Zoneco Co., Ltd., Yixing 214200, China
| | - Annan Jiang
- Department of Civil Engineering, Dalian Maritime University, Dalian 116026, China.
| | - Xiang Liu
- Department of Civil Engineering, Dalian Maritime University, Dalian 116026, China
| | - Chao He
- Shenzhen Metro Construction Group Co., Ltd., Shenzhen 518026, China
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Wang Q, Gu X, Tang S, Mohammad A, Singh DN, Xie H, Chen Y, Zuo X, Sun Z. Gas transport in landfill cover system: A critical appraisal. JOURNAL OF ENVIRONMENTAL MANAGEMENT 2022; 321:116020. [PMID: 36104890 DOI: 10.1016/j.jenvman.2022.116020] [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: 05/20/2022] [Revised: 08/10/2022] [Accepted: 08/12/2022] [Indexed: 06/15/2023]
Abstract
Landfill gas (LFG) emission is gaining more attention from the scientific fraternity and policymakers recently due to its threat to the atmosphere and human health of the populace living in surrounding premises. Though landfill cover (LFC) (viz., daily, intermittent and final cover) is widely used by landfill operators to mitigate or reduce these emissions, their overall performance is still under question. A critical analysis of available literature, primarily pertaining to (i) the composition of the landfill gases and their migration in the LFC system, (ii) experimental and mathematical investigations of the transport mechanism of gas and (iii) the impact of additives to cover soils on transport and fate of gas, has been conducted and presented in this manuscript. Investigation of the efficiency of modified soil was mainly focused on laboratory test. More field tests and application of amended cover soils should be conducted and promoted further. Studies on nitrous oxide and emerging pollutants, including poly-fluoroalkyl substances transport in landfill cover system are limited and need further research. The transport mechanisms of these unconventional contaminants should be considered regarding the selection of LFC materials including geomembrane and geosynthetic clay liners. The existing analytical and numerical models can provide a basic understanding of LFG transport mechanisms and are able to predict the migration behaviour of LFG; however, there are still knowledge gaps concerning the interaction between different species of the gas molecule when modeling multi-component gas transport. Gas transport through fractured cover should also be considered when evaluating LFG emission in the future. Simplified design method for landfill cover system regarding LFG emission based on analytical models should be proposed. Overall, mathematical models combined with experiments can facilitate more visualized and intensive insights, which would be instrumental in devising climate adaptive landfill covers.
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Affiliation(s)
- Qiao Wang
- School of Resource and Environmental Engineering, Hefei University of Technology, Hefei, 230009, China; Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China
| | - Xiting Gu
- College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, 310058, China; Architectural Design and Research Institute of Zhejiang University Co. Ltd, 148 Tianmushan Road, Hangzhou, China
| | - Suqin Tang
- Hangzhou Environmental Group, 138-1 Linban Road, Hangzhou, 310022, China
| | - Arif Mohammad
- Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Devendra Narain Singh
- Department of Civil Engineering, Indian Institute of Technology Bombay, Mumbai, 400076, India
| | - Haijian Xie
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China; College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, 310058, China.
| | - Yun Chen
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China; Architectural Design and Research Institute of Zhejiang University Co. Ltd, 148 Tianmushan Road, Hangzhou, China
| | - Xinru Zuo
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China; College of Civil Engineering and Architecture, Zhejiang University, 866 Yuhangtang Rd., Hangzhou, 310058, China
| | - Zhilin Sun
- Ocean College, Zhejiang University, Zheda Road, Zhoushan, 316021, China; College of Hydraulic Engineering and Architecture, Tarim University, Alaer, 843300, China
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Xie H, Zuo X, Chen Y, Yan H, Ni J. Numerical model for static chamber measurement of multi-component landfill gas emissions and its application. ENVIRONMENTAL SCIENCE AND POLLUTION RESEARCH INTERNATIONAL 2022; 29:74225-74241. [PMID: 35635673 PMCID: PMC9550682 DOI: 10.1007/s11356-022-20951-2] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 01/14/2022] [Accepted: 05/16/2022] [Indexed: 06/02/2023]
Abstract
The quantitative assessment of landfill gas emissions is essential to assess the performance of the landfill cover and gas collection system. The relative error of the measured surface emission of landfill gas may be induced by the static flux chamber technique. This study aims to quantify effects of the size of the chamber, the insertion depth, pressure differential on the relative errors by using an integrated approach of in situ tests, and numerical modeling. A field experiment study of landfill gas emission is conducted by using a static chamber at one landfill site in Xi'an, Northwest China. Additionally, a two-dimensional axisymmetric numerical model for multi-component gas transport in the soil and the static chamber is developed based on the dusty-gas model (DGM). The proposed model is validated by the field data obtained in this study and a set of experimental data in the literature. The results show that DGM model has a better capacity to predict gas transport under a wider range of permeability compared to Blanc's method. This is due to the fact that DGM model can explain the interaction among gases (e.g., CH4, CO2, O2, and N2) and the Knudsen diffusion process while these mechanisms are not included in Blanc's model. Increasing the size and the insertion depth of static chambers can reduce the relative error for the flux of CH4 and CO2. For example, increasing the height of chambers from 0.55 to 1.1 m can decrease relative errors of CH4 and CO2 flux by 17% and 18%, respectively. Moreover, we find that gas emission fluxes for the case with positive pressure differential (∆Pin-out) are greater than that of the case without considering pressure fluctuations. The Monte Carlo method was adopted to carry out the statistical analysis for quantifying the range of relative errors. The agreement of the measured field data and predicted results demonstrated that the proposed model has the capacity to quantify the emission of landfill gas from the landfill cover systems.
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Affiliation(s)
- Haijian Xie
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China
| | - Xinru Zuo
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China
| | - Yunmin Chen
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China
- Center for Balance Architecture, Zhejiang University, 148 Tianmushan Road, Hangzhou, 310007, China
| | - Huaxiang Yan
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Zhejiang University, Hangzhou, 310058, China.
- Department of Mechanical, Aerospace and Civil Engineering, School of Engineering, The University of Manchester, Manchester, M13 9PL, UK.
| | - Junjun Ni
- Department of Civil and Environmental Engineering, The Hong Kong University of Science and Technology, Hong Kong, People's Republic of China
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Zhu ZW, Feng SJ, Chen HX, Chen ZL, Ding XH, Peng CH. Approximate analytical model for transient transport and oxygen-limited biodegradation of vapor-phase petroleum hydrocarbon compound in soil. CHEMOSPHERE 2022; 300:134522. [PMID: 35395265 DOI: 10.1016/j.chemosphere.2022.134522] [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: 01/05/2022] [Revised: 03/12/2022] [Accepted: 04/02/2022] [Indexed: 06/14/2023]
Abstract
Volatile organic compounds (VOCs) contamination may occur in subsurface soil due to various reasons and pose great threat to people. Petroleum hydrocarbon compound (PHC) is a typical kind of VOC, which can readily biodegrade in an aerobic environment. The biodegradation of vapor-phase PHC in the vadose zone consumes oxygen in the soil, which leads to the change in aerobic and anaerobic zones but has not been studied by the existing analytical models. In this study, a one-dimensional analytical model is developed to simulate the transient diffusion and oxygen-limited biodegradation of PHC vapor in homogeneous soil. Laplace transformation and Laplace inversion of the Talbot method are adopted to derive the solution. At any given time, the thickness of aerobic zone is determined by the dichotomy method. The analytical model is verified against numerical simulation and experimental results first and parametric study is then conducted. The transient migration of PHC vapor can be divided into three stages including the pure aerobic zone stage (Stage I), aerobic-anaerobic zones co-existence stage (Stage II), and steady-state stage (Stage III). The proposed analytical model should be adopted to accommodate scenarios where the transient effect is significant (Stage II), including high source concentration, deep contaminant source, high biodegradation capacity, and high water saturation. The applicability of this model to determine the breakthrough time for better vapor intrusion assessment is also evaluated. Lower first-order biodegradation rate, higher source concentration, and shallower source depth all lead to smaller breakthrough time.
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Affiliation(s)
- Zhang-Wen Zhu
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China.
| | - Shi-Jin Feng
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China.
| | - Hong-Xin Chen
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China.
| | - Zhang-Long Chen
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China.
| | - Xiang-Hong Ding
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China.
| | - Chun-Hui Peng
- Key Laboratory of Geotechnical and Underground Engineering of Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai, 200092, China; School of Architecture and Civil Engineering, Jinggangshan University, Ji'an, Jiangxi, 343009, China.
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Li X, Li X, Wang F, Liu Y. The design criterion for capillary barrier cover in multi-climate regions. WASTE MANAGEMENT (NEW YORK, N.Y.) 2022; 149:33-41. [PMID: 35709640 DOI: 10.1016/j.wasman.2022.06.002] [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: 03/14/2022] [Revised: 05/10/2022] [Accepted: 06/03/2022] [Indexed: 06/15/2023]
Abstract
The service performance of capillary barrier cover (CBC) under continuous rainfall is unclear, leading to a lack of the design criterion for CBC in humid regions. This study proposed a design criterion for CBC in multi-climate regions. First, the influence of fine layer thickness, initial water content and rainfall intensity on the performance of CBC under continuous rainfall was clarified through a soil column test. Subsequently, calculation models of effective water storage capacity and breakthrough time were derived based on test results. Finally, a design criterion for CBC in multi-climatic regions was proposed and verified. The main findings were as follows: (1) As expected, increasing the fine layer thickness and decreasing the initial water content enhanced the water storage capacity. Within the test range, the breakthrough time has a linearly positive, linearly negative, and negative power function relationship with the fine layer thickness, initial water content, and rainfall intensity, respectively. (2) The infiltration rate of CBC is controlled by saturated hydraulic conductivity under extremely continuous rainfall, and can be described by the equivalent infiltration rate. (3) The calculation results of the proposed water storage capacity and breakthrough time models are consistent with the test results, and the proposed design criterion is robust against various climates from drought to humidity. The research results can provide a reference for the design of CBC in multi-climate regions.
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Affiliation(s)
- Xiaokang Li
- Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China.
| | - Xu Li
- Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China.
| | - Fei Wang
- Department of Higher Education Publication, China Water and Power Press, Beijing 100038, China.
| | - Yan Liu
- Key Laboratory of Urban Underground Engineering of Ministry of Education, Beijing Jiaotong University, Beijing 100044, China.
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9
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Enhanced Methane Oxidation Potential of Landfill Cover Soil Modified with Aged Refuse. ATMOSPHERE 2022. [DOI: 10.3390/atmos13050802] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/10/2022]
Abstract
Aged refuse with a landfill age of 1.5 years was collected from a municipal solid waste landfill with high kitchen waste content and mixed with soil as biocover material for landfill. A series of laboratory batch tests was performed to determine the methane oxidation potential and optimal mixing ratio of landfill cover soil modified with aged refuse, and the effects of water content, temperature, CO2/CH4, and O2/CH4 ratios on its methane oxidation capacity were analyzed. The microbial community analysis of aged refuse showed that the proportions of type I and type II methane-oxidizing bacteria were 56.27% and 43.73%, respectively. Aged refuse could significantly enhance the methane oxidation potential of cover soil, and the optimal mixing ratio was approximately 1:1. The optimal temperature and water content were about 25 °C and 30%, respectively. Under the conditions of an initial methane concentration of 15% and an O2/CH4 ratio of 0.8–1.2, the measured methane oxidation rate was negatively correlated with the O2/CH4 ratio. The maximum methane oxidation capacity measured in the test reached 308.5 (μg CH4/g)/h, indicating that the low-age refuse in the landfill with high kitchen waste content is a biocover material with great application potential.
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Lu SF, Feng SJ. Comprehensive overview of numerical modeling of coupled landfill processes. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 118:161-179. [PMID: 32892093 DOI: 10.1016/j.wasman.2020.08.029] [Citation(s) in RCA: 11] [Impact Index Per Article: 2.8] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 10/28/2019] [Revised: 06/16/2020] [Accepted: 08/13/2020] [Indexed: 06/11/2023]
Abstract
Landfilling is the primary method used for municipal solid waste (MSW) disposal. To design, optimize, and manage landfills with a life span of several decades, a deeper understanding of long-term MSW behaviors is necessary and worthwhile. These behaviors should be modeled using approaches that account for coupled processes so as to capture the evolutionary mechanisms that are mainly dominated by biochemical, mechanical, hydraulic, and thermal processes, as well as the complex interactions among them. Many mathematical models have been developed over the past three decades to address this issue. However, most of them only emphasize some of these processes, with only few models accounting for all the processes. In this review, we present a comprehensive overview of the mathematical and numerical formulations of this coupled problem. Each process occurring in landfills is interpreted in detail using different sub-models and the corresponding parameter values. Then, the existing coupled models for MSW are reviewed, and the challenges and perspectives related to the modeling of the long-term behaviors of MSW are highlighted. We conclude that more reliable constitutive formulations based not only on well-designed laboratory tests but also on field tests are necessary to improve the modeling of MSW behaviors in future.
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Affiliation(s)
- Shi-Feng Lu
- Department of Civil Engineering, School of Human Settlements and Civil Engineering, Xi'an Jiaotong University, Xi'an, Shaanxi 710049, China(1); Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China(2)
| | - Shi-Jin Feng
- Key Laboratory of Geotechnical and Underground Engineering of the Ministry of Education, Department of Geotechnical Engineering, Tongji University, Shanghai 200092, China.
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11
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Zhan LT, Wu T, Feng S, Li GY, He HJ, Lan JW, Chen YM. Full-scale experimental study of methane emission in a loess-gravel capillary barrier cover under different seasons. WASTE MANAGEMENT (NEW YORK, N.Y.) 2020; 107:54-65. [PMID: 32276126 DOI: 10.1016/j.wasman.2020.03.026] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 06/05/2019] [Revised: 02/01/2020] [Accepted: 03/18/2020] [Indexed: 06/11/2023]
Abstract
The methane emission in a loess-gravel capillary barrier cover (CBC) in winter and summer was investigated by constructing a full-scale testing facility (20 m × 30 m) with a slope angle of 14.5° at a landfill in Xi'an, China. Weather conditions, methane emission, gas concentration, temperature, and volumetric water content (VWC) in the CBC were measured. The temperature and moisture in the CBC showed a typical seasonal pattern of warm and dry in summer and cold and wet in winter. Accordingly, the maximum methane oxidation rate and methane emission were higher in summer. The mean methane influx and methane emission decreased significantly as the VWC increased beyond 40% (i.e., a degree of saturation 0.85) at a depth of 0.85 m, which was near the loess/gravel interface. At this depth, more water was presented in the loess layer in the downslope direction due to capillary barrier effects, which increased the upslope methane emission. More dominant methane emission in the middle- and upper-section of the CBC occurred in summer than in winter as there was less soil moisture to facilitate methane transfer. The LFG balance showed that a significant fraction of the loaded LFG was not accounted in the flux chamber measurements due to the preferential flow along the edges of the CBC. The maximum methane oxidation rate was 93.3 g CH4 m-2 d-1, indicating the loess-gravel CBC could mitigate methane emissions after landfill closure.
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Affiliation(s)
- Liang-Tong Zhan
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China
| | - Tao Wu
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China
| | - Song Feng
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China; College of Civil Engineering, Fuzhou University, China.
| | - Guang-Yao Li
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China
| | - Hai-Jie He
- College of Civil and Architectural Engineering, Taizhou University, Taizhou 318000, China
| | - Ji-Wu Lan
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China
| | - Yun-Min Chen
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou 310058, China
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Feng S, Leung AK, Liu HW, Ng CWW, Zhan LT, Chen R. Effects of thermal boundary condition on methane oxidation in landfill cover soil at different ambient temperatures. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 692:490-502. [PMID: 31351291 DOI: 10.1016/j.scitotenv.2019.07.108] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 04/30/2019] [Revised: 06/23/2019] [Accepted: 07/07/2019] [Indexed: 06/10/2023]
Abstract
Microbial aerobic methane oxidation (MAMO) has been considered as an environmental-friendly method for mitigating methane emission from municipal landfill sites. Soil column has in a landfill cover under one-dimensional (1-D) condition. However, most of the published soil column tests failed to simulate 1-D heat transfer due to the use of thermal conductive boundary at the sidewall. In the present study, a heavily instrumented soil column was developed to quantify the effects of thermal boundary condition on the methane oxidation efficiency under different ambient temperatures in landfill cover soil. The sidewall of the soil column was thermally insulated to ensure 1-D heat transport as would have been typically expected in the field condition. Two soil column tests with and without thermal insulation were conducted at a range of controlled ambient temperatures from 15 to 30°C, for studying how soil moisture, matric suction, gas pressure, soil temperature and gas concentration evolve with MAMO. The test results reveal that ignoring thermal insulation in a soil column test would result in a greater loss of soil heat generation by MAMO and hence oxidation efficiency by up to 100% for the range of temperature considered. When the ambient temperature increased to 30°C (but less than the optimum temperature for MAMO), the MAMO efficiency increased abruptly at first but then decreased substantially with time, and this is likely due to the accumulation of biomass generated by MAMO.
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Affiliation(s)
- S Feng
- College of Civil Engineering, Fuzhou University, China; Key Laboratory of Soft Soils and Geoenvironmental Engineering (Zhejiang University), Ministry of Education, China; Formerly Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong.
| | - A K Leung
- Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong; Formerly Division of Civil Engineering, University of Dundee, UK.
| | - H W Liu
- College of Environment and Resources, Fuzhou University, Fuzhou City, Fujian Province, China; Formerly Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong.
| | - C W W Ng
- Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong.
| | - L T Zhan
- MOE Key Laboratory of Soft Soils and Geoenvironmental Engineering, Department of Civil Engineering, Zhejiang University, Hangzhou, China.
| | - R Chen
- Department of Civil and Environmental Engineering, Harbin Institute of Technology, Shenzhen, China.
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13
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Feng S, Liu HW, Chiu ACF, Ng CWW. A steady-state analytical profile method for determining methane oxidation in landfill cover. THE SCIENCE OF THE TOTAL ENVIRONMENT 2019; 646:1528-1535. [PMID: 30235637 DOI: 10.1016/j.scitotenv.2018.07.097] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/22/2018] [Revised: 06/09/2018] [Accepted: 07/08/2018] [Indexed: 06/08/2023]
Abstract
Gas concentration profiles of carbon dioxide (CO2), oxygen (O2), methane (CH4) and nitrogen (N2) are usually measured during tests investigating microbial aerobic methane oxidation in landfill cover. However, only qualitative/limited information can be obtained from gas concentration profiles by existing methods. A new method is proposed to determine methane oxidation in soil quantitatively and comprehensively, including methane oxidation efficiency, stoichiometry, gas transfer mechanism, methane generation rate and gas reaction rate distributions. Governing equations are established based on mass balance for O2, CO2, CH4 and N2 at one-dimensional and steady-state condition. Gas transfer mechanisms considered include gas diffusion, advection and gas reaction. The method utilizes gas concentration profiles to determine gas diffusion for each gas component according to Fick's law. Then gas advections and reactions can be determined by mass balance. The method is validated by (i) published soil column tests investigating methane oxidation and (ii) a calibrated numerical model based on a selected soil column test. The new method is capable of determining methane oxidation efficiency, stoichiometry, gas transfer mechanism, methane generation rate and gas reaction rate distributions for CH4, CO2 and O2.
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Affiliation(s)
- S Feng
- College of Civil Engineering, Fuzhou University, Fuzhou City, Fujian Province, China; Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong, China.
| | - H W Liu
- Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong, China; College of Environment and Resources, Fuzhou University, Fuzhou City, Fujian Province, China.
| | - A C F Chiu
- Key Laboratory of Ministry of Education for Geomechanics and Embankment Engineering, Hohai University, 1 Xikang Road, Nanjing 210098, China.
| | - C W W Ng
- Department of Civil and Environmental Engineering, Hong Kong University of Science and Technology, Hong Kong, China.
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Bian R, Xin D, Chai X. A Simulation model for estimating methane oxidation and emission from landfill cover soils. WASTE MANAGEMENT (NEW YORK, N.Y.) 2018; 77:426-434. [PMID: 29709311 DOI: 10.1016/j.wasman.2018.04.029] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 03/21/2017] [Revised: 04/14/2018] [Accepted: 04/18/2018] [Indexed: 06/08/2023]
Abstract
Quantification of methane (CH4) oxidation and emission from landfill cover soils is important for evaluating measures to mitigate anthropogenic greenhouse gas emissions. In this study, a model that combines the multicomponent diffusive equation and Darcy's law, coupled with the dual Monod kinetic equation, was established to simulate CH4 transport, oxidation and emission in landfill cover soils. Sensitivity analysis was performed to illustrate the influence of model parameters on CH4 transport, oxidation and emission. The model was then applied to predict CH4 emissions from several column experiments. The results of the sensitivity analysis showed that a high CH4 oxidation rate can be obtained with a high Vmax of cover soil, even for a low cover soil thickness, and that oxidation efficiency is constant when the thickness of the cover soil becomes greater than a threshold value. The simulated results fitted well with the measured values, confirming that the new model provides a reliable method for estimating CH4 emissions from landfills.
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Affiliation(s)
- Rongxing Bian
- State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China
| | - Danhui Xin
- State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China; Department of Civil and Environmental Engineering, University of Delaware, Newark, DE 19716, United States
| | - Xiaoli Chai
- State Key Laboratory of Pollution Control and Resource Reuse, Tongji University, Shanghai 200092, China.
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