垃圾土变形特性及防渗膜受力的试验研究

垃圾填埋场中垃圾土的降解是垃圾填埋场沉降的主要原因,而垃圾填埋场的沉降对HPDE衬垫膜的受力和工作状态有显著的影响,HPDE衬垫膜的设计需要考虑垃圾填埋场沉降的作用,文章通过垃圾土中有机物的降解试验和垃圾土柱沉降试验,推求了考虑垃圾土压缩和降解的变形计算方法,进行了垃圾填埋场的离心模型试验,探讨了垃圾填埋场中垃圾体的变形分布规律和衬垫膜的受力特征,对衬垫膜的设计计算方法进行了研究.     

垃圾土变形特性及防渗膜受力的试验研究

垃圾填埋场中垃圾土的降解是垃圾填埋场沉降的主要原因，而垃圾填埋场的沉降对HPDE衬垫膜的受力和工作状态有显著的影响，HPDE衬垫膜的设计需要考虑垃圾填埋场沉降的作用，文章通过垃圾土中有机物的降解试验和垃圾土柱沉降试验，推求了考虑垃圾土压缩和降解的变形计算方法，进行了垃圾填埋场的离心模型试验，探讨了垃圾填埋场中垃圾体的变形分布规律和衬垫膜的受力特征，对衬垫膜的设计计算方法进行了研究。     

垃圾填埋体沉降计算方法

通过对国内外垃圾土沉降研究方法进行分析，讨论了垃圾填埋场的沉降计算方法和数学模型，认为垃圾土在填埋期的压缩变形可用土力学现有的分层总和法进行计算，而长期运行垃圾体的沉降受垃圾土的次压缩特性和有机物降解的共同影响；深圳下坪固体废弃物填埋场垃圾体的沉降量与计算结果表明，有机物降解是垃圾体沉降的主要因素。     

准好氧填埋场稳定化指标的室内模拟研究

准好氧填埋场是传统填埋场可持续发展的一个重要的方向,本文结合准好氧填埋场的室内模拟实验结果以及理论分析,提出了准好氧填埋场稳定化评价指标的四条选取原则,在模拟实验的基础上,从渗滤液性质、垃圾降解特性、填埋场地沉降三个方面建立了准好氧的评价指标体系,所包含的指标有:渗滤液COD、氨氮、TVS/TDS,固相垃圾BDM,场地沉降量。     

准好氧填埋场稳定化指标的室内模拟研究

准好氧填埋场是传统填埋场可持续发展的一个重要的方向,本文结合准好氧填埋场的室内模拟实验结果以及理论分析,提出了准好氧填埋场稳定化评价指标的四条选取原则,在模拟实验的基础上,从渗滤液性质、垃圾降解特性、填埋场地沉降三个方面建立了准好氧的评价指标体系,所包含的指标有:渗滤液COD、氨氮、TVS/TDS,固相垃圾BDM,场地沉降量.     

西北卫生填埋场渗滤液回灌系统研究

回灌技术是一种简单、低廉的渗滤液处理技术,可有效降低渗滤液中COD和氨氮的含量,加速填埋场内垃圾的降解,提高产甲烷速率和甲烷的产量,增大填埋场的沉降速率和总沉降幅度,缩短填埋场的维护期.回灌技术能够适应渗滤液水质水量的复杂变化,在我国西北地区有非常广阔的应用前景.同时,由于该技术在我国利用过程中尚缺乏成熟的工艺设计和运行经验,所以还有待进一步研究和实践.     

准好氧填埋场稳定化指标的室内模拟研究

准好氧填埋场是传统填埋场可持续发展的一个重要的方向，本文结合准好氧填埋场的室内模拟实验结果以及理论分析，提出了准好氧填埋场稳定化评价指标的四条选取原则，在模拟实验的基础上，从渗滤液性质、垃圾降解特性、填埋场地沉降三个方面建立了准好氧的评价指标体系，所包含的指标有：渗滤液COD、氨氮、TVS／TDS，固相垃圾BDM，场地沉降量。     

隔水帷幕技术在非正规垃圾填埋场治理中的工程应用

基于非正规垃圾填埋场的危害,并结合在非正规垃圾填埋场治理中常用的搬迁减量技术、好氧稳定化技术和原位封场治理技术的优缺点,提出在非正规垃圾填埋场治理中应用隔水帷幕技术,分析了应用该技术的基本条件是垃圾填埋场底部要有合适的防渗性较好的黏性土层,并通过工程应用详述了隔水帷幕技术在垃圾填埋场搬迁减量治理中的适用性。隔水帷幕技术可有效阻止垃圾填埋土和渗滤液对填埋场周边土层的污染,阻断填埋场周边地下水与渗滤液的水力联系,有效管控垃圾填埋土中污染物的扩散。     

城市垃圾填埋场填埋气产气量及产气速率的研究

城市生活垃圾填埋场填埋气产气量及产气速率直接和填埋场的设计、管理及环境影响评价相关，本文重点研究分析Buswell-Mueller化学计量法和化学需氧量法估算填埋场产气量，并进而通过Scholl-Canyon模型对产气速率进行研究，给出城市垃圾填埋场历年填埋气产气量预测计算的具体方法。     

垃圾填埋场中有机污染物的生物降解

概述了垃圾填埋场中微生物对污染物的吸收与生物化学作用,有机污染物的生物降解的基本原理及其影响因素,介绍了垃圾生物降解的四种基本动力学方程,提出了要重视我国在填埋场有机物降解机理方面的研究.     

Landfill Settlement with Decomposition and Gas Generation

A one-dimensional multiphase numerical model is developed to simulate the vertical settlement involving liquid and gas flows in a deformable (settling) municipal solid waste (MSW) landfill. MSW is represented by a chemical composition, and a global stoichiometric reaction is used to estimate the maximum yield of gas generation. Following the general assumption accepted in the literature, the gas generated by waste decomposition is assumed to comprise of methane (CH4) and carbon dioxide (CO2). The gas generation rate follows an exponentially decaying function of time. The gas generation model developed based on a first-order kinetic single-bioreactor approach includes the governing equations of gas migration, liquid flow, and landfill deformation. The Galerkin finite element method is used to solve the resulting equations. The model developed can be used to estimate the transient and ultimate settlements due to waste decomposition and gas generation in MSW landfills. The proposed model can estimate the waste porosity, gas pressure, liquid pressure, gas saturation, liquid saturation, and stress distributions in settling landfills. The results obtained for a deformable landfill are compared with a landfill having a rigid solid skeleton. Due to settlement, the depth of waste is 27% smaller in deformable landfills than that of the rigid ones.     

Secondary Compression of Municipal Solid Wastes and a Compression Model for Predicting Settlement of Municipal Solid Waste Landfills

The estimation of the capacity and settlement of landfills is critical to successful site operation and future development of a landfill. This paper reports the results of a study on biodegradation behavior and the compression of municipal solid wastes. An experimental apparatus was developed which had a temperature-control system, a leachate recycling system, a loading system, and a gas and liquid collection system. Experiments were performed both with and without optimal biodegradation for comparative purposes. Test results indicated that settlement resulting from creep was relatively insignificant when the biodegradation process was inhibited. Compression due to decomposition under optimal biodegradation conditions was found to be much larger than compression associated with creep. The biodegradation process was significantly influenced by the operational temperature. A one-dimensional model is proposed for calculating settlement and estimating the capacity of the landfill under relatively optimal biodegradation conditions. The model was developed to accommodate the calculation of settlement in landfills when a multistep filling procedure was used. The calculation method is relatively simple and convenient for design purposes. Simulations of the physical processes showed that enhancing solid waste biodegradation during the filling stage can considerably increase the capacity of the landfill and reduce postclosure settlements.     

Performance of North American Bioreactor Landfills. I: Leachate Hydrology and Waste Settlement

An assessment of state-of-the-practice at five full-scale North American landfills operating as bioreactors is presented in this two-paper set. This paper focuses on effectiveness of liners and leachate collection systems, leachate generation rates, leachate recirculation practices and rates, effectiveness in moistening the waste, and settlement of the waste over time. Except in one case, the liner and leachate collection systems at the bioreactor landfills were similar to those used for landfills operated conventionally. Leachate generation rates increased approximately linearly with recirculation rate, but in all cases, the leachate generation rate was <300?L/m2?year. Leachate depths generally were maintained within regulatory requirements, even with the highest recirculation rates. Leakage rates from liners at bioreactor landfills, including alternative liner designs employing geosynthetic clay liners, are comparable to leakage rates from conventional landfills. Thus, based on the information gathered in this study, additional requirements or features for liners or leachate collection systems are not warranted for bioreactor landfills. Diminishing capacity of horizontal recirculation trenches is common. Experience at one landfill suggests that small doses at high frequency under substantial injection pressure can deter loss of trench capacity. Only those landfills that were aggressive in recirculation had achieved water contents near the field capacity. Increasing the amount of liquid that is added may be required to achieve field capacity at some landfills, particularly if a final cover is placed soon after waste grades are reached. The rate of time-dependent waste settlement attributed to biodegradation is about 1.6 times larger in bioreactor landfills than in conventional landfills, and increases as the recirculation dosage increases.     

Effectiveness of Scrap Tire Chips as Sorptive Drainage Material

Scrap tire disposal is a problem of growing concern. One solution to this problem is innovative methods for the reuse and recycling of scrap tires. Based on batch isotherm tests, scrap tire chips have been identified to be good sorbents of volatile organic compounds (VOCs) and could be used as leachate drainage layer material in solid waste landfills and in other similar applications. To demonstrate the effects of tire chips on the leachate they come in contact with in a drainage layer over a liner, large-scale tank tests simulating the drainage layer and the clay liner and also field tests were performed. Two cells were constructed in a landfill: one with scrap tire chips and the other with gravel leachate collection layer. According to the results of the large-scale tank tests and field tests, shredded tire chips have a significantly positive impact on the quality of the leachate with which they come in contact. The use of scrap tires in landfills would reduce the magnitude of the current tire disposal problem (a 1 ha landfill requires approximately 300,000 tires to fill 0.3 m of a leachate collection layer) and convert one waste into a beneficial construction material and simultaneously mitigate the problem of VOC transport from through landfill liners.     

Modeling of Settlement in Saturated and Unsaturated Municipal Landfills

Municipal solid waste (MSW) landfills are not only used to dispose the refuse in most economical way but also utilized as a viable land in today’s waste management strategy. Settlement prediction is an important issue in order to guarantee the integrity of any postclosure structure on landfills. In this study, landfill settlement in saturated and unsaturated landfills is investigated by developing a one-dimensional mathematical model and performing numerical experiments. Under the saturated conditions, the landfill is considered to be completely liquid saturated by preventing gas generation at all times. On the other hand, for the unsaturated case, we assume that a gas mixture comprised of methane and carbon dioxide is generated as a result of microbial decomposition of MSW deposited. The gas generation is assumed to follow a first-order kinetic approach. The liquid phase and gas mixture are considered compressible as well as the solid matrix (landfill body). After the governing equations were discretized using the Galerkin finite-element method, the Gaussian elimination technique is employed for a solution. In saturated landfills, the settlement is mainly caused by the overburden weight of the waste deposited. Further, the mass loss due to waste decomposition contributes for an additional settlement in unsaturated landfills. The predicted settlements are within the range reported in the literature. The model developed can simulate porosity, pressures, saturations, and stress profiles in settling landfills as well as to predict the transient and ultimate settlements in saturated and unsaturated landfills.     

Municipal Solid Waste Landfill Settlement: Postclosure Perspectives

This paper presents settlement mechanisms and the methods for estimating settlements of municipal solid waste landfills, including bioreactor landfills. Based on results of field monitoring and data in published literature, coefficients of secondary compression for solid waste due to self-weight and external load are estimated. Special considerations are given to bioreactor landfills. Uses of these coefficients for long-term settlement estimation and their application to postclosure maintenance and development plans are discussed. Four case histories illustrating the use of these coefficients are presented. Methods of landfill treatment to reduce settlements are also presented.     

Evaluation of Decomposition Effect on Long-Term Settlement Prediction for Fresh Municipal Solid Waste Landfills

A considerable amount of settlement occurs due to the decomposition of municipal solid waste (MSW) in landfills over a period of years. Therefore, the effect of biological decomposition governs the long-term settlement characteristics of municipal solid waste landfills. In this study, we investigated the long-term settlement characteristics by applying a number of prediction methods to fresh MSW sites and predicting the settlement curves. Most proposed methods, excluding the power creep law, successfully predicted long-term settlement only if accelerated logarithmic compression due to decomposition of biodegradable MSW was included in the settlement prediction.     

Sepiolite as an Alternative Liner Material in Municipal Solid Waste Landfills

Compacted clay has traditionally been used as a lining material in municipal solid waste landfills. However, natural clays may not always provide good contaminant sorption properties. One alternative material that is abundant in some parts of Europe and Turkey as well as Western United States is sepiolite. A laboratory study was undertaken to investigate the feasibility of sepiolite as a liner material. Two clays, one rich in sepiolite and the other one rich in kaolinite mineral, as well as their mixtures were subjected to geomechanical, hydraulic, and environmental tests. The same soils were also subjected to strength and hydraulic conductivity tests after a series of freeze and thaw cycles. The results of the study indicated that relatively high hydraulic conductivity and shrinkage capacity of sepiolite necessitates addition of kaolinite before being used as a landfill material. The valence of the salt solutions affected the swell and hydraulic conductivity characteristics of the clays tested. Retardation factors for sepiolite for metal solutions are 1.2–2.2 times higher than those calculated for the clay that is rich in kaolinite, and the inorganic contaminant adsorption capacity of the clay can be improved by addition of sepiolite. The results indicated that the clay mixtures utilized in this study provide good geomechanical, hydraulic, and metal adsorption properties which may justify their potential use as a liner material in solid waste landfills.     

Modeling of Clay Liner Desiccation

The potential for the desiccation of clay liner component of composite liners due to temperature field generated by breakdown of organic matter in municipal solid waste landfills is examined using a model proposed by Zhou and Rowe. In these analyses, a set of fully coupled governing equations expressed in terms of displacement, capillary pressure, air pressure, and temperature increase are used, and numerical results are solved by using finite element method with a mass-conservative numerical scheme. The model results are shown to be in encouraging agreement with experimental data for a problem involving heating of a landfill liner. The fully coupled transient fields (temperature, horizontal stress change, suction head, and volumetric water content) are then examined for two types of composite liner system, one involving a geomembrane over a compacted clay liner (CCL) and the other involving a geomembrane over a geosynthetic clay liner (GCL). It is shown that there can be significant water loss and horizontal stress change in both the CCL and GCL liner even with a temperature increase as small as 20°C. The time to reach steady state decreases as boundary temperature increases. Under a 30°C temperature increase, it takes 5 years to reach the steady state water content with a GCL liner but 50 years with a CCL liner. The effects of various parameters, such as hydraulic conductivity and thickness of the liner, on the performance of the liner are discussed.