Municipal Solid Waste Layer Research Articles

Transient and Quasi-Steady-State Analytical Methods for Simulating a Vertical Gas Flow in a Landfill with Layered Municipal Solid Waste

The exploration of gas pressure and its distribution in landfills is a principal concern for the design and management of municipal solid waste (MSW) landfills. A one-dimensional analytical model was proposed to simulate a vertical gas flow in a landfill with layered MSWs. The transient analytical solution was obtained by the method of superposition and eigenfunction expansion and verified by a semi-analytical solution and numerical simulation. According to the results of a parametric analysis by the transient analytical solution, a vertical gas flow in landfills can be simplified to a quasi-steady-state flow. A quasi-steady-state analytical solution for simulating a vertical gas flow in a landfill with layered MSW is proposed. The quasi-steady-state analytical solution showed good agreement with the transient solution. Both temporal and spatial variations of the gas generation rate in MSW landfills were considered in the transient and quasi-steady-state analytical methods. A comparison between the proposed quasi-steady-state solution and the previously described steady-state solution showed that using the average gas generation rate or the gas generation rate corresponding to the average age of the MSW layer in the steady-state solution resulted in an error in the estimation of the gas pressure in landfills. The proposed solutions are reliable and can provide a reference for the design, management, and subsequent restoration of landfills.

Estimation of municipal solid waste amount based on one-dimension convolutional neural network and long short-term memory with attention mechanism model: A case study of Shanghai

Municipal solid waste (MSW) amount has direct influence on MSW management, policy-decision making, and MSW treatment methods. Machine learning has great potential for prediction, but few studies apply the approaches of deep learning to forecast the quantity of MSW. Therefore, the aim of this study is to evaluate the feasibility and practicability of employing the methods of supervised learning, including Attention, one-dimension Convolutional Neural Network (1D-CNN) and Long Short-Term Memory (LSTM) to predict the MSW Amount in Shanghai. Integrated 1D-CNN and LSTM with Attention model, the new structure model (1D-CNN-LSTM-Attention, 1D-CLA), is designed to forecast MSW amount. In addition, the influence of socioeconomic factors on MSW amount, the structure and layers distribution of Attention, 1D-CNN, LSTM and 1D-CLA are also discussed. The results indicate that the correlation coefficients of Attention, one-dimension CNN, LSTM, and proposed 1D-CLA model to predict the MSW in Shanghai are 78%, 86.6%, 90%, and 95.3%, respectively, suggesting the feasible and practicable. The values of 24, 0.01, 50 and 25 for the number of neurons, dropout, the value of epoch number and Batch size best fit 1D-CLA to predict the amount of MSW in Shanghai. Furthermore, the performance of 1D-CLA is better than any single model or two model's combination (R2 is 95.3%) and the mechanism of 1D-CLA is contributed by three former models following the order: LSTM>CNN>Attention.

Simulation of gas transport in a landfill with layered new and old municipal solid waste

Average biodegradation rate of newly filled municipal solid waste (MSW) in landfills is relatively fast, and the landfill gas produced by the new MSW biodegradation can cause great variations in gas pressure. To predict the gas pressure distribution in the MSW layer, a one-dimensional gas transport model is established in this study. The following factors are considered in this model: (1) the variation of gas permeability with depth; (2) the anisotropy ratio of gas permeability; (3) the settlement caused by waste biodegradation. Furthermore, a single peak model for gas production is applied as the source term of gas production. The equation for settlement caused by waste biodegradation is presented, and the time of peak gas production rate is obtained by fitting the settlement of the newly filled layer. The stratification of the unsaturated and saturated regions is taken into account by distinguishing the difference in gas saturation. The layering of the new and old waste layers is considered by distinguishing the difference in the length of time that waste has been degraded to produce gas. Based on the method of numerical calculation, the gas pressure distribution in the landfill with layered new and old MSW is well simulated. The position where the maximum gas pressure occurs is found. The sensitivity analysis shows that the influence of the anisotropy ratio on gas pressure distribution is more significant.

Temperature monitoring during a water-injection test using a vertical well in a newly filled MSW layer of a landfill.

High temperature may adversely affect municipal solid waste (MSW) biodegradation and lead to an increase in the deformation of high-density polyethylene (HDPE) pipes used for the collection of leachate and landfill gas in landfills. The test in this study was to change the waste temperature around the vertical injection well by water injection using a vertical well. The test was conducted intermittently with two different flowrates in a newly filled MSW layer of a landfill. The temperature, gas pressure and leachate level in the test area were simultaneously monitored during this study. The results showed that the waste temperature around the vertical injection well was effectively changed by water injection, which did not result in a significant rise in the leachate level. During water injection, the waste temperature influence distance in the horizontal direction increased with depth from the leachate level to the bottom of the injection well. The bottom temperature of the injection well decreased to near the water-injection temperature. The range of influence of the waste temperature caused by intermittent water injections slightly increased in this test. After water injection was stopped, the waste temperature near the vertical injection well increased quickly initially, and then the increments became more gradual with time. When the leachate level recovered stably, there was still a temperature gradient around the injection well within the range of influence. The temperature and gas pressure in the waste above the leachate level and far away from the injection well were slightly influenced by water injection.

Temperature and Gas Pressure Monitoring and Leachate Pumping Tests in a Newly Filled MSW Layer of a Landfill

Field test data on the simultaneous variations of leachate level, temperature and gas pressure in waste can be used in verifying the theoretical solution of coupled model of gas pressure and temperature in municipal solid waste (MSW) landfills. The correlation between the variations of these properties caused by leachate pumping is a major concern in the management of landfills. Therefore, temperature and gas pressure monitoring and leachate pumping tests were conducted in a newly filled MSW layer of a landfill located at Wuxi, southeastern China. The multifunctional extraction well and monitoring wells were designed to monitor the simultaneous variations of leachate level, temperature and gas pressure. The spatial and temporal distributions of these parameters and their correlation were investigated and analyzed. The results show that the highest waste temperature occurs near the leachate level. The gas pressures measured in the waste above the leachate level increase with depth. During the leachate pumping test, the temperature and gas pressure increase in the leachate level decreasing zone. When the leachate level has stably recovered, the temperature decreases slightly and gas pressure in this zone decreases to nearly zero. In addition, the MSW permeability of the newly filled MSW layer is calculated. The variation in the water content caused by the change in the leachate level affected the temperature and gas pressure in the waste. The temperature and gas pressure increased in the leachate level decreasing zone. The gas pressure was collectively affected by the water content and temperature in the waste.

Разработка фрактальной модели гидродинамики в слое твердых коммунальных отходов в процессе производства газообразного топлива

Разработка фрактальной модели гидродинамики в слое твердых коммунальных отходов в процессе производства газообразного топлива

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.

Reliability Based Approach for the Prediction of Leachate Head in MSW Landfills

The paper presents the reliability-based approach to assess the performance of landfill considering uncertainties associated with the hydraulic properties of various components of the system. A model domain having final cover system and municipal solid waste (MSW) layer is considered as an integrated system for the analysis. Water balance is computed using the Hydrologic Evaluation of Landfill Performance (HELP) model to construct response surfaces for the reliability analysis. The probability of accumulation of leachate head \(({{h}_{ac}})\) at the bottom of the MSW layer above an allowable head \(({{h}_{al}})\) is considered as the criterion for reliability estimates in this study. The results of the analysis are discussed in terms of the reliability index, \(\beta\). The impact of variations in (a) hydraulic characteristics of the various layers (b) defects and placement conditions of geomembrane (GM) on the system performance have been studied. The results reveal that the hydraulic conductivity of compacted clay layer (CCL) of the cover component along with the porosity and saturated hydraulic conductivity of MSW layer are the significant parameters, which influence the reliability. Further, impact of model uncertainty and parametric analysis of significant variables are conducted and the results are discussed.

A Case of Study About the Influence of Organic Matter in Municipal Solid Waste Settlement

Municipal solid waste (MSW) settlement can be understood as volume reduction of the waste mass disposed in a landfill. Such phenomenon is mainly the result of organic matter degradation. Settlement can also be generated by MSW distortions, particle rearrengements, and other factors. These factors can be accurately analyzed if studied in an MSW experimental cell once it simulates the landfill behavior in a known and controlled way. This study aims to analyze the behavior of an experimental cell filled with MSW and how the biodegradation can influence the settlement over time and depth. The methodology was composed of waste sampling, experimental cell construction and filling, volatile solids analysis, and settlement measurements. The MSW gravimetric and volumetric analyses were performed in order to quantify the amount of organic matter contained inside the experimental cell. The tests indicated that the amount of organic matter drastically decreased in all MSW layers, and settlement varied according to the depth of the experimental cell due to mechanical factors and organic matter consumption.

Experimental Determination of Thermal Characteristics of Municipal Solid Waste

The article is devoted to the experimental study of effective thermal characteristics of municipal solid waste (MSW) wet layer in the drying process. The research is based on the zone method. Series of laboratory experiments was performed. The drying kinetics and temperature curves were obtained on the base of which the kinetic coefficients were determined. We constructed a graph of the kinetic coefficients of the material moisture. The research results can be used for determination the temperature and moisture content fields in the MSW layer during its processing.

Effect of Mass Proportion of Municipal Solid Waste Incinerator Bottom Ash Layer to Municipal Solid Waste Layer on the Cu and Zn Discharge from Landfill.

Municipal solid waste incinerator (MSWI) bottom ash is often used as the protection layer for the geomembrane and intermediate layer in the landfill. In this study, three sets of simulated landfills with different mass proportion of MSWI bottom ash layer to municipal solid waste (MSW) layer were operated. Cu and Zn concentrations in the leachates and MSW were monitored to investigate the effect of MSWI bottom ash layer on the Cu and Zn discharge from the landfill. The results showed that the Zn discharge was dependent on the mass proportion of MSWI bottom ash layer. The pH of landfill was not notably increased when the mass proportion of MSWI bottom ash layer to MSW layer was 1 : 9, resulting in the enhancement of the Zn discharge. However, Zn discharge was mitigated when the mass proportion was 2 : 8, as the pH of landfill was notably promoted. The discharge of Cu was not dependent on the mass proportion, due to the great affinity of Cu to organic matter. Moreover, Cu and Zn contents of the sub-MSW layer increased due to the MSWI bottom ash layer. Therefore, the MSWI bottom ash layer can increase the potential environmental threat of the landfill.

Fluctuation of dissolved heavy metal concentrations in the leachate from anaerobic digestion of municipal solid waste in commercial scale landfill bioreactors: The effect of pH and associated mechanisms

Heavy metals present in landfill leachate have infrequently been related to complete anaerobic degradation municipal solid waste (MSW) due to discrete ages of deposited MSW layers and leachate channelling in landfills. In this study, anaerobic digestion of MSW was performed in two enclosed 1000 tonne bioreactors using a unique flood and drain process. Leachates were characterised in terms of pH, soluble chemical oxygen demand, volatile fatty acids (VFAs), ammonium nitrogen and heavy metals over the entire course of digestion. All parameters, including pH, fluctuated during acidogenesis, acetogenesis and methanogenesis, which strongly impacted on the dynamics of dissolved heavy metal concentrations. The simulation of dissolution and precipitation processes indicated that metal sulphide precipitation was not a factor as metal concentrations exceeded solubility limits. The correlation of pH and dissolved heavy metal concentrations indicated that other, mechanisms were involved in the homogenised conditions within the bioreactors. Beside dissolution and precipitation, the main processes most likely involved in metal distributions were adsorption (Zn, Cu, Ni, Pb and Cd), complexation (Cr) or combinations of both process (As and Co).

Experimental research of solid waste drying in the process of thermal processing

The convective drying process of municipal solid waste layer as a polydispersed multicomponent porous structure is studied. On the base of the experimental data criterial equations for calculating heat transfer and mass transfer processes in the layer, depending on the humidity of the material, the speed of the drying agent and the layer height are obtained. These solutions are used in the thermal design of reactors for the thermal processing of multicomponent organic waste.

Ecological Threats Caused by Improper Disposal and Incineration of Municipal Solid Waste

The paper discusses a critical situation regarding municipal solid waste (MSW) in Donetsk city (Ukraine) as a suitable example. Special attention is given to such problems as bio-degradation and self-ignition of MSW dumps as well as the hazard of dioxins that might be present in the emitted gases. The paper describes the materials as well as techniques used for experiments and calculations of results. The paper offers theoretical calculations of biogas emissions from MSW landfill bodies as well as the results of experimental measurements performed within laboratory conditions of a “MSW micro-landfill”. Dynamics of development of microorganism colonies within the body of MSW has been studied experimentally and a mathematical model of these processes was developed. There was calculated a volume of leachate (“MSW-sewage”) produced at MSW landfills as well as migration of toxic waste from the leachate to underground water and soil surrounding MSW landfills of Donetsk. MSW self-ignition processes taking place within waste layers and diffusion of toxic fire-hazardous gases have been studied both theoretically and experimentally. There have been developed and proposed techniques of forecasting and prevention of MSW self-ignition within MSW layers. Processes of MSW incineration together with resinous industrial waste have been studied within the framework of experiments, namely: there were measured emissions of toxic combustion gases and heavy metals as well as “distribution” of the latter in combustion gases and ash

One-Dimensional Transient Analytical Solution for Gas Pressure in Municipal Solid Waste Landfills

Landfill gas (LFG) is generated in municipal solid waste (MSW) landfills because of the decomposition of degradable components. Gas pressure within the landfilled MSWs is of importance as cover or landfill stability may be affected by gas pressure. This paper presents a one-dimensional transient analytical solution for gas pressure profiles in a MSW layer. This solution considers the variation of the LFG generation rate with respect to depth and decay of the LFG generation rate with time. The authors used the specified outward gas flux bottom boundary condition to simulate horizontal LFG collection systems and basal leachate collection systems serving dually as LFG collection systems. The presented solution also gives the outward gas flux from the MSW layer surface, which may be used to assist in the prediction of air quality near landfills. An application of the presented solution shows that averaging the LFG generation rate throughout the MSW layer results in a remarkable overestimation of gas pressure.

Analysis of solid-liquid-gas interactions in landfilled municipal solid waste by a bio-hydro-mechanical coupled model

Based on first-order kinetics of hydrolysis process, biodegradation of municipal solid waste (MSW) is assumed to obey a first-order decay equation which can take the direct effect of water content on biodegradation into account. Hydraulic model is an unsaturated-saturated flow model using mass conservation equations for fluids. Mechanical compression of MSW is expressed by a stress-age coupled compression model. Through above models, a one-dimensional (1-D) bio-hydro-mechanical coupled model is established to analyze solid-liquid-gas interactions in landfilled MSW. Values of all the model parameters for current typical Chinese MSW are determined. Numerical analysis of a hypothetical waste sample in a closed system shows that gas pressure and gas concentration is extremely large which might cause severe gas explosion problem. Total gas production is about 267.0 m3 per wet ton of fresh wastes. For another hypothetical landfilled MSW layer, the coupled model predicts a dissipation of gas pressure during passive gas collection process. Annual gas production is large at the beginning of biodegradation, and then decreases with time. Surface settlement of the wastes increases quickly initially and then becomes stable with a compression strain of about 0.32 after 20 years.

Assessment of the efficiency and economic viability of various methods of treatment of sanitary landfill leachate

This study assesses the efficiency of various physico-chemical, biological and other tertiary methods for treating leachate. An evaluation study on the treatability of the leachate from methane phase bed (MPB) reactor indicated that at an optimum hydraulic retention time of 6 days, the efficiency of the reactor in terms of biological oxygen demand (BOD) and chemical oxygen demand (COD) removal was 91.29 and 82.69%, respectively. Recycling of the treated leachate through the municipal solid waste layers in the leachate recycling unit (LRU) resulted in a significant increase in the biodegradation of organics present in the leachate. Optimum BOD and COD removal efficiencies were achieved at the third recycle; additional recycling of the leachate did not produce any significant improvement. Physico-chemical treatment of the leachate demonstrated that alum and lime (Option 2) were more economical than coagulants lime and MgCO(3). A cost analysis of the economics of the various treatments revealed that the alternative treatment consisting of a MPB bed followed by a LRU and aerated lagoon is the most cost-effective treatment. However, the alternative consisting of a MPB followed by the LRU and a soil column, which is slightly more costly, would be the most appropriate treatment when adequate land is readily available.

Measuring transient water flow in unsaturated municipal solid waste – A new experimental approach

This research investigated transient water flow in unsaturated municipal solid waste (MSW) packed in columns using neutron scattering. The method developed was able to measure absolute moisture content and moisture variation in a sample of MSW produced in the city of Fortaleza (Brazil) during a simulated tropical rain event. The technique was proven to be efficient, showing that channeling flow accounts for most of the unsaturated flow conditions. The most important effect of micro-porous flow was on water accumulation and small long-term outflow. Furthermore, the definition of field capacity used in soil sciences does not seem to apply to flow in unsaturated MSW; the MSW layers kept increasing in moisture content long after water was allowed through. Finally, the long-term draining experiment demonstrated that the macro-porous matrix may not be a continuous medium, which makes experimental procedures that rely on matrix potential in specific points of the solid waste mass inaccurate.