Waste Settlement Research Articles

Analysis of long-term MSW settlement based on field data measured at two closed landfills

Waste settlement characteristics vary depending on waste composition, physical properties, waste management operations, and time. In this study, the post-closure waste settlement behavior was analyzed using field data measured at two closed municipal solid waste landfills in Korea, for 23 and 5 years after landfill closure. The long-term waste settlement data was analyzed to derive a time-varying long-term compression ratio (CLT) that was consistent with modeled biodegradation processes. A statistical assessment of the field data was conducted to examine the relationship between CLT and several factors that may affect the observed settlements. The CLT of Landfill #1 and #2 was found to vary between the two landfills that had differences in the percentage of organic matter (B0), total unit weight (γwaste), and moisture content (w) due to changes in waste management policies.

Biotransformation of Raw Mango Seed Waste into Bacterial Hydrolytic Enzymes Enhancement Via Solid State Fermentation Strategy.

Solid waste generation is a huge contributor to environmental pollution issues, and food wastes are prominent in this category due to their large generation on a day-to-day basis. Thus, the settlement of daily food waste is one of the major constraints and needs innovative manufacturingsheme to valorize solid waste insustainable manner. Moreover,these food wastes are rich in organic content, which has promising scope for their value-added products. In the present study, raw mango seed waste has been biotransformed to produce bacterial hydrolytic enzymes as feedstock. On investigating the impact of substrate, the highest bacterial cellulase production was recorded to be 18IU/gds FP (filter paper) in 24h of microbial incubation at 5g of substrate in solid-state fermentation (SSF). Furthermore, at 40°C and pH 6.0, 23IU/gds FP enzyme could be produced in 24h of SSF. Beside this, on comparing the influence of inorganic and organic nitrogen sources, urea has been found to provide better cellulase production, which yielded 28IU/gds FP in 24h of incubation, along with 77IU/gds BG (β-glucosidase) and 89IU/gds EG (endoglucanase). On the other hand, Tween-40 and Tween-80, two different surfactants, were employed at a 1.0% concentration for 24h of incubation. It was noticed that Tween-80 showed complete enzyme activity at 24h, which was found to be relatively superior to that of Tween-40. This study may have potential utility in enzyme production using mango seed as a food waste for various industrial applications.

Analytical and numerical models for strain and load calculations for geosynthetic liner systems on steep slopes

The paper develops an analytical model based on the force equilibrium for the design of steep slope geosynthetic liner systems to overcome downdrag loads from waste settlement. This analytical model calculates the required tensile stiffness for a high strength/stiffness geotextile (HS-GTX) reinforcement over the GMB to limit the maximum HS-GTX tensile strain to 5% and the maximum GMB strain to 4% on the side slope. The numerical model illustrates the need for reducing the GMB tensile strains for a single GMB liner on a steep landfill slope and confirms that the use of a HS-GTX over the GMB is able to limit the maximum HS-GTX and GMB tensile strains to the acceptable strain levels. The analytical model developed in this paper is a practical tool for preliminary design to limit tensile strains of the HS-GTX and GMB in a steep slope geosynthetic liner system.

Impact of Leachate Recirculation on the Stabilization of Municipal Solid Waste in Anaerobic Bioreactors of Different Compositions

The aim of the current study is to determine the impacts of leachate recirculation on the degradation of three compositions of municipal solid waste in anaerobic bioreactors. The study was completed by using six columns with equal volume (0.042m3) containing different densities and compositions of solid waste, in order to follow waste degradation over a limited time. Three compositions of waste were studied: simulated fresh waste of standard composition, simulated fresh waste of fermentable composition, and actual aged waste. Measurements of the significant parameters including pH, leachate conductivity, Chemical Oxygen Demand (COD), and waste settlement, were carried out. The quantity of oxidized organic matter was increased by the leachate recirculation, and the degradation period was reduced by using leachate recirculation. After 300, 150, and 480 days, waste stabilization seemed to be reached for fresh, aged, and fermentable waste, whereas the organic content decreased to 650, 480, and 4000mg COD/L, respectively.

Numerical modelling of settlement of municipal solid waste in landfills coupled with effects of biodegradation

This paper presents the development of a new settlement model to predict the long-term settlement of municipal solid wastes (MSWs). The total settlement of the MSWs results from the direct loss of solids due to decomposition and compression due to stress variation induced by loss of solids, flow of gas and liquid and mechanical creep. The geotechnical properties of MSWs are considered as functions of degrees of biodegradation (DOB). To validate the model, two settlement profilers (2.5 years) and three geodetic monitoring networks (2 years) were installed at Mugga Lane Landfill, ACT, Australia to monitor the settlement of an MSW lift and three closed landfill cells, respectively. The settlement rates of the landfill cells with the ages of 7, 8, 14, and 8, 9 and 15 years are 0.53, 0.35, 0.06 and 0.46, 0.36, 0.05 mm/day, respectively. In addition, 5 large scale and 3 small scale bioreactors were set up in the field and laboratory to address the long-term physical, mechanical and biochemical behaviours of the MSWs under different stress levels. The predicted settlement is compared to the test results from the bioreactors, in-situ monitoring data and the settlement predicted using an existing model, which has been improved by coupling the geotechnical properties of MSWs with DOBs. The predicted settlement using the proposed model well fits the test results and monitoring data. The settlement strain is predicted to be 28.2 % during the filling stage of the landfill and 5.9 % in 5 years after the closure.

Effect of increased temperature and leachate recirculation on biogas production and settlement of municipal solid waste.

This study evaluated the effects of increased temperature and leachate recirculation on volatile solids (VS), biogas, hydrogen sulphide (H2S) leachate quality (pH and chemical oxygen demand) and the settlement of municipal solid waste (MSW). Three large-scale tests were conducted with no leachate recirculation at 21°C, weekly leachate recirculation at 20°C and weekly leachate recirculation at 50°C. Leachate recirculation and increased temperature accelerated biodegradation and pushed forward the onset time (from 27 to 8 days). The increase of biodegradation activity was reflected in the change of biogas production, VS and settlement. Compressibility index , increased from 0.71 and 0.77 at 21°C to 0.83 when the temperature was 50°C. In addition, leachate recirculation and high temperature reduced H2S concentration levels by inhibiting the growth of sulphate-reducing bacteria and leachate recirculation lowered H2S production by dissolving the high H2S presence. The results showed that MSW can have significantly changed mechanical and biochemical behaviour under different temperatures and saturations. The results help understand the processes in landfills for more effective short-term and long-term design and management.

Assessment of waste settlement models based on the long-term settlement data measured at a multi-stage MSW landfill in Korea

Assessment of waste settlement models based on the long-term settlement data measured at a multi-stage MSW landfill in Korea

Comparative analysis of the quantity and quality of both synthetic and biodegradable films on kitchen waste

The huge demand for plastic use, inadequacy in waste management, and casual community behavior towards proper disposal creates a remarkable threat to life on Earth. The garbage waste, which consists of plastic bags upon exposure to rainwater and the moisture content present in the landfill, proceeds to leachate generation. This poses a major influence on the design and operation of the landfill. The present work emphasizes the effect of different types of polymeric films on kitchen waste, which is a major portion of municipal solid waste. The study has been conducted considering different polymeric films, including LDPE, starch, and LDPE blended starch film of different wt% (4 wt%, 8 wt% & 12 wt%). The objective of the present work is the keen observation of the bed height settlement of kitchen waste having different weight percent of polymeric films and the measurement of the leachate volume taken out from different containers before and after centrifugation. The quality and property of leachate have been checked by considering various parameters like COD, pH, conductivity, and salinity. It has been noticed that there is an encouraging effect on prolonged biodegradation on leachate formation and successive waste bed settlement due to the presence of plastics. It was observed that 4 wt% of LDPE blended starch film has an optimal effect on waste disposal. Hence the present work will assist in mollifying the alarming threat inflicted by plastic disposal on municipal organic solid waste.

Numerical study of strain development in high-density polyethylene geomembrane liner system in landfills using a new constitutive model for municipal solid waste

Tensile strain development in high-density polyethylene (HDPE) geomembrane (GMB) liner systems in landfills was numerically investigated. A new constitutive model for municipal solid waste (MSW) that incorporates both mechanical creep and biodegradation was employed in the analyses. The MSW constitutive model is a Cam-Clay type of plasticity model and was implemented in the finite difference computer program FLAC™. The influence of the friction angle of the liner system interfaces, the biodegradation of MSW, and the MSW filling rate on tensile strains were investigated. Several design alternatives to reduce the maximum tensile strain under both short- and long-term waste settlement were evaluated. Results of the analyses indicate that landfill geometry, interface friction angles, and short- and long-term waste settlement are key factors in the development of tensile strains. The results show that long-term waste settlement can induce additional tensile strains after waste placement is complete. Using a HDPE GMB with a friction angle on its upper interface that is lower than the friction angle on the underlying interface, increasing the number of benches, and reducing the slope inclination are shown to mitigate the maximum tensile strain caused by waste placement and waste settlement.

Comparison of waste settlement characteristics for two landfills disposed in long sequential periods

Changes in waste management policy affect the settlement characteristics of waste landfills in which the waste disposal is operated for decades. In this study, the waste settlements were calculated by using the data measured in two multi-staged landfills for 27 years. The relationship between the changes in waste management policies and settlement characteristics is analyzed. Sequentially launched waste management policies reduced the organic matters in municipal solid waste (MSW) of the landfill. This change in turn influenced the engineering properties of landfill waste, e.g. water content, unit weight, and initial void ratio, etc. Due to the reduction of food waste in landfills, the water content decreased and the unit weight increased. The initial void ratio declined by the decrease of water content and the increase of unit weight. The annual primary and secondary compression indices, Cc and Cα, of each lift also increased/decreased due to the change in waste composition. The Cc of Phase #1 increased from an average of 0.34 to an average of 0.51 because the percentage of coal ash in MSW drastically decreased and the percentage of food, paper, and plastic, which are highly compressible, increased. On the other hand, the Cc of Phase #2 declined from an average of 0.15 to an average of 0.025 due to the decrease of the waste compressibility from the reduction of organic matters. The Cα of Phase #1 and #2 decreased by the reduction of organic matter and moisture which are needed for biodegradation of wastes in the landfill.

Temperature Effects on Stability and Integrity of Geomembrane–Geotextile Interface in Municipal Solid Waste Landfill

Review of the limited experimental studies available in the published literature that investigate the effects of temperature on the shear strength of typical geomembrane (GM) and geotextile (GTX) interface is performed. These studies suggest that the shear strength of GM–GTX interfaces generally increase with an increase in temperature. However, there is no study that examined the combined effect of the temperatures along the bottom liner and the large displacement induced by the waste settlement on the short-term and long-term stability and integrity of the GM–GTX interface in a composite bottom liner system in municipal solid waste (MSW) landfills. This paper presents the application of a thermal model to predict the evolution and distribution of temperatures within the waste and along the bottom liner system of a typical landfill cell model, while simultaneously evaluating the influence of the predicted temperatures on the shear response of GM–GTX interfaces in the composite bottom liner system. The predicted temperatures along the liner interface of the simulated landfill cell varied between 4 and 32 °C, which are well within the reported temperatures in and around the bottom liners in MSW landfills. The results also suggest that beginning the placement of waste in summer is favorable than in winter, since the high temperatures at the GM–GTX during summer mobilize higher shear strengths resulting in lower shear displacements. Further, if stability analysis using limit equilibrium method is performed, then the shear strength of GM–GTX interface corresponding to the low temperature ranges expected at the site should be used for conservative and reliable estimates of the stability of the bottom liner system.

Long-term and residual settlement behaviour of a multi-staged municipal solid waste landfill, Republic of Korea.

In this study, characteristics of the long-term landfill settlement are analysed and the starting date of residual settlement is deduced using the data of the landfill 1 of the Gimpo Metropolitan Landfill (GML) measured for 27 years. The landfill 1 is a multi-staged municipal solid waste landfill where dykes are constructed after landfilling for subsequent waste fills. The landfilling began in 1992 and finished in 2000, and the waste settlement measurement continued throughout this period. The older waste of the lower lift shows higher biodegradation and larger settlement than the waste of the upper lift, which acts as vertical load. Large settlement occurred in the lower lifts due to the collapse of waste voids caused by the overburden load of the upper lifts after biodegradation of waste in the lower lifts during long-term landfilling. In the conventional landfills, that is, mono-layer landfills, the time-dependent settlement generally occurs after the stress-dependent settlement. But, most of the time, this landfill showed mainly the time-dependent settlement. The duration, at which the biodegradation of organic matters is reduced and the residual settlement begins, was 8.8 years in average and the date range was from 7.6 to 11.7 years considering each disposed block in landfill 1. This date is obtained by calculating from the mid-point time of the landfilling duration.

Settlement and slope stability analysis of landfill site for sustainable utilization

Waste accumulation in a landfill is often made a problem, especially when the landfill has reached the end of its service life, so there is a need for further utilization of the landfill, one of the things that can be done is to utilize the landfill as a place where a building can be built. In this research, a review of the waste settlement and slope stability uses the Plaxis Program to determine whether the landfill is able to withstand the burden of buildings. The research is located at Piyungan Yogyakarta Landfill. Material data in the form of the value of the friction angle, the volume weight of waste, and the modulus of elasticity obtained from previous research. From the results obtained, it is known that the deformation of waste that occurs shows a significant settlement up to 45 cm with load 1250 kg/m2 so the foundation design at landfill area needs concern about high settlement, and this can be used as the basis for sustainable utilization of landfill.

Comprehensive coupled thermo-hydro-bio-mechanical model for holistic performance assessment of municipal solid waste landfills

A comprehensive coupled thermo-hydro-bio-mechanical (CTHBM) model is proposed to simulate the coupled interactions between the hydraulic, mechanical, biochemical, and thermal processes observed in municipal solid waste (MSW) and also assess their influence on the long-term performance of MSW landfills. The hydraulic model is based on two-phase fluid flow through unsaturated porous media. The biochemical model is based on a two-stage anaerobic biodegradation model. The thermal model is based on conductive heat transport with heat generation rates derived from the biodegradation model. The mechanical model uses the soft-soil-creep constitutive model to simulate the time-dependent creep behavior of the waste. The effect of biodegradation and subsequent mass loss on the waste settlement is also incorporated. Using the proposed CTHBM model, two numerical simulations were performed on a typical full-scale landfill cell geometry to determine the long-term spatial and temporal variations in the hydraulic, mechanical, biochemical, and thermal characteristics of waste under conventional and bioreactor landfill conditions. The influence of the dynamic changes in the waste characteristics on the shear behavior of a textured geomembrane-geotextile interface in the bottom liner and cover system of the simulated landfill cell was also examined.

Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling

A coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a conventional landfill simulation with no leachate injection (CONV) and two bioreactor landfill simulations involving leachate injection—were carried out by applying the CTHBM model to a typical two-dimensional (2D) landfill cell configuration to analyze the effect of temperature on the long-term performance characteristics of a landfill system. Of the two bioreactor landfill simulations, one (BIOR-T) incorporated temperature effects on the waste decomposition, while the other simulation (BIOR-NT) did not. For the waste conditions simulated, the CONV and BIOR-T had a maximum waste temperature of 54°C and 62°C, respectively. The temperatures at the bottom liner were determined to be in the range of 1°C–32°C and 1°C–39°C over the entire simulation time of the CONV case and BIOR-T case, respectively. The effect of waste temperatures on moisture distribution, methane gas production, and landfill surface settlement was also assessed. The surface settlement response for BIOR-T and BIOR-NT simulations suggests that incorporating the effect of waste temperatures on the waste decomposition is important for a realistic prediction of the waste settlement in landfills. The BIOR-T and BIOR-NT simulations had a similar interface shear response, suggesting that the changes in the stiffness and shear strength of waste, due to incorporating temperature effects on the biodegradation rate, have no noticeable impact on the interface shear response in the bottom liner system. Overall, the proposed CTHBM model can be used to predict long-term performance characteristics (e.g., moisture distribution, landfill gas production, settlement of waste, temperatures) relevant for effective design of bioreactor landfills.

Modeling elasto-visco-bio-plastic mechanical behavior of municipal solid waste in landfills

This paper presents a mechanical model for the prediction of short-term and long-term settlement of municipal solid waste in landfills. The load-induced volumetric compression, shear behavior, tensile behavior, and the time-dependent creep compression behavior of the waste are modeled using the soft soil creep model. The compression induced by decomposition of waste is modeled based on the phenomenon of wetting-induced strains observed in compacted fills with expansive soils. The proposed model is validated using benchmark datasets obtained from two long-term laboratory experiments performed on waste samples obtained from a landfill in UK. Two additional numerical simulation cases (CONV—without leachate injection and BIOR—with leachate injection) were examined by application of the proposed mechanical model on a typical full-scale landfill cell geometry to determine the spatial and temporal variation in the short-term and long-term settlement characteristics of waste in the simulated landfill cell. The settlement of waste predicted by the model could capture the key mechanisms of short- and long-term waste settlement in landfills. The leachate injection in BIOR simulation enhanced the rate of depletion of the degradable solids resulting in a significant increase in the waste settlement. For the simulated landfill and waste conditions, the biodegradation-induced settlement contributed to more than 90% of the settlement of the waste in both CONV and BIOR simulations. The distribution of the injected leachate had a considerable influence on the settlement profiles observed within the waste.

Laboratory Analysis and Prediction of Settlement of Municipal Solid Waste Under Anaerobic Condition

The settlement of municipal solid waste under anaerobic condition is considered important for structural stability even after closure of the landfill. In this context, the settlement of waste was analyzed under constant loading in the anaerobic reactor. A settlement value of 29.9% was observed in the reactor immediately after load placement on the sample. Consolidation analysis of the collected municipal solid waste showed that the primary settlement of the waste completed after 48 h of load application. The total secondary settlement was observed to be 5.85% at the end of 202 days. From the results obtained for the biogas generation and settlement, the rate of degradation of waste was observed to be 0.477 day−1. The settlement of landfill depends upon composition, moisture content, depth, density and compression characteristics of waste. The municipal solid waste thus needs analysis of biodegradation rate and also a mathematical model to predict the settlement. Thus, the mathematical modeling of predicting the settlement of landfill showed that initially the rate of settlement of the waste was high due to high degradation rate of organic contents. The settlement of 6.4% due to biodegradation and 10–18% was predicted due to mechanical compression in the landfill.

Prediction of landfill leachate quantity in arid and semiarid climate: a case study of Aradkouh, Tehran

This paper represents the application of a developed water balance model (based on a model which has been prepared in Germany) to estimate the quantity of leachate output in arid and semiarid regions. Field capacity, saturated water conductivity, and waste direct evaporation tests were implemented to characterize the basic hydrologic properties of municipal waste and the effect of climate conditions on leachate production. A test cell in Aradkouh landfill with the area of 32 × 50 m2 was constructed to calibrate and compare the measured values with the results of the model. Since the cell is located in a semiarid climate, evaporation had a crucial role in decreasing the primary leachate quantity. The field capacity of the waste is obtained approximately 32.5% (V/V), which is more than the results of laboratory tests. Besides, the waste permeability of the cell was calculated (1.02 × 10−6 m/s) that is less than the results of experiments. In order to determine the effect of waste settlement in leachate production, an initial rate of settlement and ultimate settlement by using hyperbolic function has been obtained 0.104 and 146.5, respectively. Although aerobic reactions were not prevailing in the cell due to thermal conditions and incompatibility with the observed values, anaerobic reaction decreased the discharged leachate by 10.82%.

Modeling the stress-strain state of of a municipal solid waste landfill

Introduction. The process of municipal solid waste (further MSW) generation is inextricably linked with the life of humanity. Every day each person generates some, a small amount of garbage. As a result millions of tons of MSW are generated daily in the world which are unsuitable for further use and require disposal. There are various ways of handling MSW including their treatment, recycling and disposal. In Russian Federation the vast majority of MSW are currently located on the specially equipped facilities –– waste landfills. To date the most common waste management strategy remains their placement in a landfill. Waste landfills are arrays of stored waste and are special engineering structures designed for the safe isolation of their contents from the environment. Landfill includes gas exhaust and leachate drainage systems, liner and cover systems. The main component of this structure is waste itself. Mechanical stability of landfills should be provided at all stages of waste storage as well as after it complete filling to designed capacity and at post-closure stage. As the result of deformation of unstable waste, all landfill systems can be destroyed up to the collapse of garbage array leading to the significant environmental and other consequences. One of the most common problems leading to the various incidents at landfills is an incorrect assessment of their stability. MSW landfill is a complex multiphase system in which various interacting processes occur simultaneously. The main factor in the calculation and design of landfills is the forecast of their settlements. Studies by many authors have established that biological decomposition has a significant impact on the properties of MSW after which the waste is considered as the landfill soil with a particle size of up to 20 mm. Materials and methods. The paper presents the methodology and the results of numerical modeling of stress-strain state of the designed object “Waste Landfill”. The facility is an array of municipal solid waste of 38 meters high. Waste is stacked in the layers of 1.75 m thick. Each waste layer is covered by the loam cover of 0.25 m thick. Stress-strain state of municipal solid waste including biological creep was modelled using well-known “Soft-Soil-Creep model” (SSC-model). Results. The results of numerical simulation of stress-strain state of the waste pile at all stages of the filling and in the post-closure period are presented. An assessment of the increase in the capacity of the landfill due to the compaction and biological creep has been performed. Stability analysis of the landfill and potential failure mechanisms at different stages of filling and operation are presented. Conclusions. Numerical modeling of stress-strain state of the MSW array using the “Soft-Soil-Creep model” allows to analyze the stability of the waste pile at any stage of landfill filling and evaluate the increase in landfill capacity due to the waste settlement taking into account the mechanical creep and biocompression during layer-by-layer filling.

Numerical Modeling of Dynamic Compaction Induced Settlement of MSW Landfills

Abstract The objective of this study is to estimate dynamic compaction (DC) induced settlement of municipal solid waste (MSW) landfills using numerical modeling. Finite element (FE) based analysis ...