Landfill Settlement Research Articles

Performance comparison of a MSW settlement prediction model in Tehran landfill

The municipal solid waste (MSW) landfills experience a large post-closure settlement over time. Waste settlement significantly impairs utilities, structures, and the other facilities constructed on top of a landfill. This study presents the settlement mechanisms and the methods of estimating MSW landfill settlements. Since the waste materials exhibit engineering properties which vary depending on many factors such as the location, time, climate, this study also presents the data related to the landfill characteristics, waste composition, waste moisture content, and other physical and chemical properties of waste. In addition, this paper discusses the findings of a settlement investigation conducted at a municipal solid waste landfill in Tehran. In this research, based on the collected field data and data obtained from the available literature, a technical management tool for MSW closed landfills has been developed using MATLAB, which aims to predict time dependent settlement under self-weight and surcharge loads in landfills considering various related parameters, leachate, gas generation, and moisture distribution, coefficients of compression, whilst it calculates different properties of wastes, and determines the landfill slope stability under various conditions. This user-friendly program captures the variation of the model parameters with time. The results of the verification process indicate that the results from the technical management tool have been in a very good agreement with the measured field settlement data, collected from Tehran landfill.Moreover, the results of sensitivity analysis of the model in regard to variation of input parameters indicate that there are two prominent characteristics, having significant impacts on the overall landfill settlement. These characteristics are the landfill height and the compressibility parameters.The outcomes of this study can improve the confidence for design and construction on MSW landfills. It may reduce the uncertainty when predicting the landfill settlement and enable to apply the landfill redevelopment techniques more effectively and efficiently. Studying the creep settlement properties under the co-effect of stress, biodegradation and temperature for predicting the total landfill settlement is recommended for future studies.

Resource Mining for a Bioreactor Landfill

Background: A new generation of the sustainable landfill is designed to achieve sustainable Municipal Solid Waste (MSW) management. It is hybrid anaerobic/aerobic biodegradation landfill followed by landfill mining. However, there is limited information on landfill mining, especially the criteria and process for the practitioner to determine the end of the landfill biodegradation to commence landfill mining. Objective: Hence the overall objective of this research was to develop a comprehensive resource mining plan for bioreactor landfills. </P><P> Method: When waste decomposition becomes slower or stopped, the landfill can be mined to recover resources and utilize the recovered space. The amount of the gas generated, landfill temperature and landfill settlement are indirect measures of landfill activity. Also, the concentration of cellulose (C), hemicelluloses (H), and lignin (L) can describe the biodegradable fractions of waste. Hence the biodegradation in landfills can be monitored by recording the change in methane production, temperature, settlement and the (C+H)/L ratio of waste. Once methane recovery is minimal, landfill reaches a maximum settlement and, ambient temperature plus the (C+H)/L value reaches a stable value of 0.25 indicating end of biodegradation. At this point landfill resources including compost material, non-recoverable waste, and recyclables such as plastics, metal and glass can be mined and recovered. Compost and recyclables can be sold at market value and the non-recovered waste with high energy content can be used as refuse-derived fuel. Once the landfill has been mined space can be reused thus eliminating the need to allocate valuable land for new landfills. </P><P> Result: The landfill mining detailed in this manuscript utilizes principles from single stream type recycling facilities to ensure feasibility. The first landfill will be excavated and screened to separate the biodegraded soil and compost fraction from the recyclables. Then the screened recyclable materials are transported for further processing in a single stream type separation facility where they will be separated, bundled and sold. Conclusion: A cost calculation was performed for the resource mining of Calgary Biocell and if the mined resources are sold at market values, then the mining of Calgary Biocell would generate approximately $4M.

Investigation of Solid Waste Characteristics in Field-Scale Landfill Test Cells

<p>This paper presents the results of an experimental study carried out in field-scale test cells in order to determine the effect of aeration and leachate recirculation on waste decomposition rate, solid waste characteristics, landfill gas composition and settlement in the landfill body. Four landfill test cells with the dimensions of 20 m x 40 m x 5 m were constructed in Komurcuoda Sanitary Landfill, Istanbul. Solid wastes representing Istanbul Asian side waste characteristics were landfilled in the test cells and they were operated simulating anaerobic (AN1), leachate recirculated anaerobic (AN2), semi-aerobic (A1) and aerobic landfilling (A2) methods. Alternative landfilling methods for accelerating solid waste stabilization in landfills were investigated by means of solid waste characteristics (elemental analysis, pH, moisture content, TOC, TKN, C/N ratio, volatile solid content (VS), biochemical methane potential (BMP), and stability index (SI) analysis), landfill gas components (CH4, CO2, O2, and H2S), temperature variations in landfill body, and landfill settlement. The study indicated that aeration and leachate recirculation accelerate biodegradation rate. Higher rates of MSW biodegradation eventually provide reduction in the contaminant life span of the landfill by achieving a high waste volume reduction in a relatively short duration than anaerobic test cells, decrease the cost of long term monitoring incurred with post-closure of landfill sites. In case of impossibility of aerobic landfilling based on the results of the cost benefit analysis, it was stated out that semi-aerobic landfilling technology is also a viable method in shortening the stabilization time and accelerating the landfill gas production.</p>

Identification of initial settlement of municipal solid waste layers in Indonesian landfill.

This study presents the measurement of municipal solid waste (MSW) compressibility and subsequent development of a landfill settlement estimation model incorporating a correction factor accounting for initial settlement prior to the addition of pressure/municipal solid waste layers. Three layers of municipal solid waste obtained from a temporary waste station in Bandung, Indonesia, were placed in each of three different lysimeters/treatments (MSWorganic, layer height 35 cm; MSWmixed-1, layer height 70 cm; and MSWmixed-2, layer height 35 cm), with a time lag of sample layer input of 2 days. Tests were then undertaken based on the ASTM D2435 test standard - Standard Test Method for One-Dimensional Consolidation Properties of Soils - revealing large immediate and secondary compression ratio values reflecting the high moisture and organic matter content of the analysed municipal solid waste. From the test results, it was also detected that the initial settlement of the analysed municipal solid waste was considerable even before the addition of pressure/further layers, ranging from 10% to 17%. Thus, a modification was made to the classical Sowers settlement estimation model in the form of a correction factor representing the initial settlement occurring prior to the addition of the municipal solid waste layers. This modification resulted in a decrease in the difference between estimated and actual settlement values, from 17% to 24% based on the Sowers equation model to below 5% using the proposed modified settlement model.

Modeling Coupled Hydro-Bio-Mechanical Processes in Bioreactor Landfills: Framework and Validation

Bioreactor landfills using leachate recirculation in municipal solid waste (MSW) undergo complex interrelated hydraulic, mechanical, and biochemical processes. In this study, the authors present a mathematical framework that combines and solves together a hydraulic model, a biodegradation model, and a mechanical model to simulate and predict the coupled hydro-bio-mechanical behavior of MSW in bioreactor landfills. The mathematical framework was implemented in Fast Lagrangian Analysis of Continua (FLAC), a finite difference code. The hydraulic model was a two-phase flow model where the fluid flow was governed by Darcy’s law while the saturated–unsaturated hydraulic behavior was governed by a soil-water retention model. The mechanical behavior of the MSW was evaluated by a plane-strain explicit formulation of the Mohr-Coulomb constitutive model, which accounted for concurrent changes in the MSW properties as a result of the MSW degradation. The MSW decomposition was modeled as a first-order decay kinetics biodegradation model similar to the LandGEM model used by the United States Environmental Protection Agency. The coupled mathematical framework was validated with a published large-scale laboratory experiment and a field-scale experiment. It was applied to simulate the coupled behavior of a typical bioreactor landfill cell undergoing hydro-bio-mechanical interactions. Overall, the study shows that the proposed mathematical framework accounted for both the spatial and temporal changes in the geotechnical properties of the MSW, including the extent of degradation, and predicted the landfill settlement and MSW stabilization time for a typical bioreactor landfill configuration subjected to coupled hydro-bio-mechanical processes. In addition, some of the limitations and key challenges associated with the numerical model are highlighted.

Biogas from municipal solid waste landfills: a simplified mathematical model.

Municipal solid waste (MSW) landfills now represent one of the most important issues related to the waste management cycle. Knowledge of biogas production is a key aspect for the proper exploitation of this energy source, even in the post-closure period. In the present study, a simple mathematical model was proposed for the simulation of biogas production. The model is based on first-order biodegradation kinetics and also takes into account the temperature variation in time and depth as well as landfill settlement. The model was applied to an operating landfill located in Sicily, in Italy, and the first results obtained are promising. Indeed, the results showed a good fit between measured and simulated data. Based on these promising results, the model can also be considered a useful tool for landfill operators for a reliable estimate of the duration of the post-closure period.

A dual-permeability hydro-biodegradation model for leachate recirculation and settlement in bioreactor landfills.

A dual-permeability hydro-biodegradation model is developed to describe the leachate flow in municipal solid waste (MSW) and predict the long-term settlement induced by biodegradation in bioreactor landfills. The model is verified against Hydrus-1D and a recirculation experiment conducted in a full-scale landfill. Preferential flow and mass transfer between fissure and matrix can be reasonably modeled by the proposed model. A higher recirculation flow rate can speed up the stabilization process of landfill. However, too much recirculation leachate is not economical and environmental friendly. A stabilization speed index and a leachate utilization index are adopted to evaluate the stabilization speed of bioreactor landfill and utilization rate of leachate, respectively, and the optimal recirculation flow rate is estimated. A flow rate of q = 5×10-5-5×10-4m/h (equivalent to recirculation intensity of Q = 15-150L/tonwaste/year) is recommended for recirculation, which has been verified by the field data in numerous bioreactor landfills.

Reliability assessment of bioreactor landfills using Monte Carlo simulation and coupled hydro-bio-mechanical model

The performance of a bioreactor landfill is highly influenced by the simultaneous interactions of several coupled processes that occur within the landfill. In addition, the high uncertainty and spatial variability in the geotechnical properties of municipal solid waste (MSW) poses significant challenge in accurately predicting the performance of bioreactor landfills. In this study, a 2D coupled hydro-bio-mechanical (CHBM) model was employed to predict the behavior of MSW in bioreactor landfills. The numerical model integrated a two-phase flow hydraulic model, a plane-strain formulation of Mohr-Coulomb constitutive model, and a first order decay biodegradation model. The statistical ranges (mean and standard deviation) of some of the major influential MSW properties were derived from the published studies. Random fields of spatially variable MSW properties were generated following the log-normal distribution. Reliability-based analysis was carried out by performing several realizations of Monte-Carlo simulations and the statistical response of the output results including the moisture distribution, pore fluid pressures, landfill settlement, and interface shear response of the composite liner system were quantified. The results clearly indicate the importance of considering spatial variability of the geotechnical MSW properties and its influence on the performance of bioreactor landfills during leachate injection operations. A comparison of the results with the deterministic analysis was performed to evaluate the relative benefits and to emphasize the need for reliability-based analysis for effective design of bioreactor landfills.

A practical approach for calculating the settlement and storage capacity of landfills based on the space and time discretization of the landfilling process

The settlement of any position of the municipal solid waste (MSW) body during the landfilling process and after its closure has effects on the integrity of the internal structure and storage capacity of the landfill. This paper proposes a practical approach for calculating the settlement and storage capacity of landfills based on the space and time discretization of the landfilling process. The MSW body in the landfill was divided into independent column units, and the filling process of each column unit was determined by a simplified complete landfilling process. The settlement of a position in the landfill was calculated with the compression of each MSW layer in every column unit. Then, the simultaneous settlement of all the column units was integrated to obtain the settlement of the landfill and storage capacity of all the column units; this allowed to obtain the storage capacity of the landfill based on the layer-wise summation method. When the compression of each MSW layer was calculated, the effects of the fluctuation of the main leachate level and variation in the unit weight of the MSW on the overburdened effective stress were taken into consideration by introducing the main leachate level’s proportion and the unit weight and buried depth curve. This approach is especially significant for MSW with a high kitchen waste content and landfills in developing countries. The stress-biodegradation compression model was used to calculate the compression of each MSW layer. A software program, Settlement and Storage Capacity Calculation System for Landfills, was developed by integrating the space and time discretization of the landfilling process and the settlement and storage capacity algorithms. The landfilling process of the phase IV of Shanghai Laogang Landfill was simulated using this software. The maximum geometric volume of the landfill error between the calculated and measured values is only 2.02%, and the accumulated filling weight error between the calculated value and measured value is less than 5%. These results show that this approach is practical for satisfactorily and reliably calculating the settlement and storage capacity. In addition, the development of the elevation lines in the landfill sections created with the software demonstrates that the optimization of the design of the structures should be based on the settlement of the landfill. Since this practical approach can reasonably calculate the storage capacity of landfills and efficiently provide the development of the settlement of each landfilling stage, it can be used for the optimizations of landfilling schemes and structural designs.

An equivalent-time-lines model for municipal solid waste based on its compression characteristics

Municipal solid waste (MSW) demonstrates a noticeable time-dependent stress–strain behavior, which contributes greatly to the settlement of landfills and therefore influences both the storage capacity of landfills and the integrity of internal structures. The long-term compression tests for MSW under different biodegradation conditions were analyzed. It showed that the primary compression can affect the secondary compression due to the biodegradation and mechanical creep. Based on the time-lines model for clays and the compression characteristics of MSW, relationships between MSW’s viscous strain rate and equivalent time were established, and then the viscous strain functions of MSW under different biodegradation conditions were deduced, and an equivalent-time-lines model for MSW settlement for two biodegradation conditions was developed, including the Type I model for the enhanced biodegradation condition and the Type II model for the normal biodegradation condition. The simulated compression results of laboratory and field compression tests under different biodegradation conditions were consistent with the measured data, which showed the reliability of both types of the equivalent-time-lines model for MSW. In addition, investigations of the long-term settlement of landfills from the literature indicated that the Type I model is suitable for predicting settlement in MSW landfills with a distinct biodegradation progress of MSW, a high content of organics in MSW, a short fill age or under an enhanced biodegradation environment; while the Type II model is good at predicting settlement in MSW landfills with a distinct progress of mechanical creep compression, a low content of organics in MSW, a long fill age or under a normal biodegradation condition. Furthermore, relationships between model parameters and the fill age of landfills were summarized. Finally, the similarities and differences between the equivalent-time-lines model for MSW and the stress-biodegradation model for MSW were discussed.

Influence of dynamic coupled hydro-bio-mechanical processes on response of municipal solid waste and liner system in bioreactor landfills

A two-dimensional (2-D) mathematical model is presented to predict the response of municipal solid waste (MSW) of conventional as well as bioreactor landfills undergoing coupled hydro-bio-mechanical processes. The newly developed and validated 2-D coupled mathematical modeling framework combines and simultaneously solves a two-phase flow model based on the unsaturated Richard’s equation, a plain-strain formulation of Mohr-Coulomb mechanical model and first-order decay kinetics biodegradation model. The performance of both conventional and bioreactor landfill was investigated holistically, by evaluating the mechanical settlement, extent of waste degradation with subsequent changes in geotechnical properties, landfill slope stability, and in-plane shear behavior (shear stress-displacement) of composite liner system and final cover system. It is concluded that for the given specific conditions considered, bioreactor landfill attained an overall stabilization after a continuous leachate injection of 16years, whereas the stabilization was observed after around 50years of post-closure in conventional landfills, with a total vertical strain of 36% and 37% for bioreactor and conventional landfills, respectively. The significant changes in landfill settlement, the extent of MSW degradation, MSW geotechnical properties, along with their influence on the in-plane shear response of composite liner and final cover system, between the conventional and bioreactor landfills, observed using the mathematical model proposed in this study, corroborates the importance of considering coupled hydro-bio-mechanical processes while designing and predicting the performance of engineered bioreactor landfills. The study underscores the importance of considering the effect of coupled processes while examining the stability and integrity of the liner and cover systems, which form the integral components of a landfill. Moreover, the spatial and temporal variations in the landfill settlement, the stability of landfill slope under pressurized leachate injection conditions and the rapid changes in the MSW properties with degradation emphasizes the complexity of the bioreactor landfill system and the need for understanding the interrelated processes to design and operate stable and effective bioreactor landfills. A detailed discussion on the results obtained from the numerical simulations along with limitations and key challenges in this study are also presented.

Statistical Modeling of Municipal Solid Waste Settlement from a Lysimeter

The sanitary landfill settlement prediction is an important tool for an integrated waste management system once it allows the evaluation of the sanitary landfill useful life and assists in the development of planning actions. Several settlement models have been used as an attempt to estimate the waste volume reduction over time. However, there are few models that consider the waste biodegradation processes. The objective of this paper is to build a simple linear regression model to determine the settlements that took place over time in a lysimeter filled with municipal solid waste from the city of Campina Grande, State of Paraíba, Brazil. The lysimeter was built in the Environmental Geotechnics Group’s experimental field which is located at the Federal University of Campina Grande’s main campus. For the settlement model development, the municipal solid waste settlement from a lysimeter was monitored during 1309 days. It was observed that in the interquartile range, data exhibited a trend of linearity, so this monitoring time was selected in order to develop the model. Through the tests carried out, it can be considered that the developed model presents significant statistical parameters to estimate the waste settlement. Such model can be applied for the estimation of settlement from sanitary landfills with similar features to the ones used in this model.

3차원기법을 이용한 폐기물매립지 정보관리시스템 구축 연구

본 연구에서는 폐기물매립지 운영자, 관계 공무원 및 지역주민들에게 폐기물매립에 관한 정보 제공은 물론 실시간으로 폐기물매립지의 운영 및 관리를 최적화할 수 있는 매립 정보관리 시스템을 개발하였다. 매립 정보관리 시스템은 두 개의 시스템 (폐기물 매립이력 관리 시스템 및 매립 진척상황 관리 시스템)로 구성되어 있다. 자동화된 RFID / LPR 방식에 의한 고형 폐기물 매립이력 관리 시스템은 폐기물 수거 차량과 반입폐기물의 정보를 관리하며, 또한 폐기물매립지 외각에 설치된 추적 카메라를 이용하여 폐기물의 매립위치 및 매립시간 등의 정보를 3차원으로 DB화하여 향후 매립폐기물의 자원화 및 사후토지 이용 시 필요한 매립이력을 제공할 수 있도록 하였다. 매립진척상황 정보관리 시스템은 레이저 스캐너를 이용하여 실시간으로 매립지 부피 및 용량을 3차원으로 관리하여 매립진척상황을 실시간으로 산정할 수 있도록 하여 향후 매립지 잔여용량 분석을 통한 수요예측이 가능하도록 하였다. An information management system for a solid waste landfill site was developed, in this study, to optimize the operation and management of solid waste landfill in real time in addition to provide the information of landfill status to the landfill operator, public official concerned and local residents. The landfill information management system is composed of two systems (Solid waste landfill history management system and landfill operation and performance management system). The solid waste landfill history management system based on automated RFID/LPR system allows landfill operators to provide information of waste collection vehicles and received waste. In addition, the system aids in the identification of 3-dimensional (3D) position for landfilled solid wastes. Using the landfill operation and performance management system based on 3D laser scanner delivers information about landfill volume, settlement, landfill density, and current landfill capacity to landfill operators in real time, resulting in optimum space utilization. Ultimately, this system would dramatically reduce exposure of landfill operators to hazardous materials and improve the productivity of landfill operations.

A Comprehensive Anaerobic Degradation Model using both Mass and Energy Balance for Bio-Reactor Landfills

Landfills settle due to its weight and biodegradation of waste. Biodegradation-induced settlement is a direct result of rearrangement of waste skeleton in response to the conversion of waste mass into landfill gases. In this manuscript, a Comprehensive Anaerobic Degradation Model using both Mass and Energy Balance for Bio-Reactor Landfills was developed and compared model predations with measured data from Calgary Biocell. The model solves the mass and energy balance of waste decay, and computes the consequential rate of gas generation, and gas flux through the system. The decomposing biomass is represented as cellulose for energy balance computation. The microbial degradation of biomass generates methane, carbon dioxide and water in a exothermic reaction. The heat released due to anaerobic decay is used to calculate the increase in Biocell temperature. Then the decay constant for this Biocell temperature is used to calculate the decomposition of waste for the next time step. The above computation is continued in order to obtain the landfill settlement, temperature and the movement of landfill gas and leachate. The thermal profile predicted by the model matched reasonably well with the field values measured at the Calgary Biocell. Keywords: Anaerobic, biocell, bio degradation, decay constant, exothermic, temperature

Simulation of the solid waste landfill settlement taking into account underlying soil

As the closed landfills occupy 7 % of the territory of Ukraine, there is a question about the possibility of their use in future as a foundation for different constructions. The goal is to establish a dependency of the settlement of a closed landfill on the properties of the underlying soil and on the angle of inclination of a landfill. This will allow forecasting the possibility of using a polygon as a foundation for a variety of purposes. The mathematical simulation and the finite elements method were used. The mathematical simulation of the settlement of a landfill was carried out with consideration of geometric, physical and mechanical parameters of a landfill and its ground foundation. It was established that the ground foundation of a landfill considerably affected the value of the settlement. As a result of the studies it was found that with the decrease in the angle of inclination of the landfill’s slope the settlement significantly decreased. Thus, by reducing the angle of inclination from 75° to 30°, the settlement decreased by 5–22 % depending on the type of the underlying soil. Also, the largest decline was observed for the least dense soil (sand). With a decrease in the angle, the difference between the settlement of landfills with different ground foundations decreases. The results obtained can be used for forecasting the settlement of a polygon with different geometric and physical­mechanical parameters for evaluation of the possibility of their further use as a foundation for structures with a variety of purposes.

Retraction Notice: Sensitivity Analysis on Stability Parameters in Landfill

To study the stability of waste body failure in landfill, the landfill was divided into two parts: an active wedge and a passive wedge. A limit equilibrium analysis was used to calculate the safety factor of stability in landfill. The parameters which affected the stability of the landfill were discussed. Sensitivity curves of each parameter were proposed and effect trends of various parameters on safety factor were analyzed. Cohesion c and internal friction angles increases linearly with the safety factor. The safety factor decreases with increasing slope angleand filled height H. The safety factor of after landfill settlement was higher than the safety factor of settlement which did not occur. It increases the overall stability about 16%.

Reliability analysis of municipal solid waste landfill settlements

Reliability analysis of municipal solid waste landfill settlements

Sensitivity Analysis on Stability Parameters in Landfill

To study the stability of waste body failure in landfill, the landfill was divided into two parts: an active wedge and a passive wedge. A limit equilibrium analysis was used to calculate the safety factor of stability in landfill. The parameters which affected the stability of the landfill were discussed. Sensitivity curves of each parameter were proposed and effect trends of various parameters on safety factor were analyzed. Cohesion c and internal friction angle фs increases linearly with the safety factor. The safety factor decreases with increasing slope angle β and filled height H. The safety factor of after landfill settlement was higher than the safety factor of settlement which did not occur. It increases the overall stability about 16%.

Differential thermal infrared imaging for environmental inspection

Aerial differential thermal imaging has been proposed to characterize the ground temperature distribution of two solid waste landfills. The differential approach permitted detection of regions with thermal abnormalities potentially associated with either biogas leakage and migration or improper landfill settlement and management. Methods, results, limits, and potentialities of the proposed approach are discussed.

Laboratory Determination of Water Retention Characteristics and Pore size Distribution in Simulated MSW Landfill Under Settlement

To examine how water retention characteristics in a landfill environment change as a result of solid waste settlement and to derive the evolution of pore size distribution, a lab scale long column experiment was carried out at two different time periods while keeping all the other characteristics constant. Two columns, Column 1 and Column 2, were used in the study. The log normal distribution model was applied to model the experiment data. The Column 1 was used to obtain the water retention curve at time 0 day and the Column 2 at time 180 day. During the experiment period, landfill settlement was mainly in the primary stage of settlement. Pore size distribution was obtained by assuming that the capillary theory is applicable in the landfill environment. The results showed that water retention characteristics in solid waste landfill environment is varied with time and influenced by landfill settlement due to the changes in pore spaces. The obtained results will be taken into consideration when simulating unsaturated leachate and gas flow in municipal solid waste landfill environment.