Landfill Operation Research Articles

Study of Biogas Composition on Operational and Non-Operational Landfill Sites from Poland

An assessment of the variability of biogas components captured in an active and closed municipal waste landfill sites differing of amount deposited waste, activity period with their passive degassing, was presented in the article. The results of research did not show significant differences between components of LFG from studied landfill sites. But was confirmed that the two landfill sites including used landfill site, became at the last phase degradation of waste and advantage the anaerobic processes at the low value below 0.02 of CH4/O2 indicator. It was demonstrated by the very low average methane content below 1%, and significant higher of oxygen above 19%. This confirm that only way of biogas utilization is to burn it in flare on the landfill sites.

The Generation, Composition and Fate of Landfill Leachate: A Review

The quantity of waste generated each year is in increase. Landfilling is one of the predominant methods for municipal waste disposal. Unfortunately, leachate is formed during the landfill operations. Therefore, proper management of leachate is essential to avoid unwanted impacts on the environment. In order to do that, the composition in relation to stage of generation should be studied. In this review, the generation and composition of leachate are highlighted.

Research on Seepage Field and Slope Stability Considering Heterogeneous Characteristics of Waste Piles: A Less Costly Way to Reduce High Leachate Levels and Avoid Accidents

Due to the characteristics of high heap and large volume, the complex layers of waste, high-water level of leachate, environmental pollution, and slope instability are easily produced. Although many researchers have studied landfill two-dimensional leachate migration law, three-dimensional seepage and stability of landfill sites have been rarely studied. This paper focuses on the heterogeneous characteristics of the landfill piles and analyzes the seepage field and slope stability of the landfill using statistical and numerical analysis methods. The calculated results are compared with the field measurement and literature research data to verify the reliability of the model, which may provide the basis for the design and safe and eco-friendly operation of the landfill. Taking an actual landfill as the research object, the saturated–unsaturated transient model of heterogeneous waste is applied to practical engineering. Considering the landfill process and heterogeneous permeability, the calculated maximum water level is higher. Compared with the homogeneous material, the difference in the water level of each waste layer is about 0.08∼1.88 m, which is not good for the stability of the landfill. Combined with the engineering characteristic distribution of a landfill, the heterogeneous stability model is applied to the actual project to study the influence of different unit weight and shear strength distribution on landfill stability. The established model is suitable for the study of two-dimensional and three-dimensional slope stability of landfill sites. Through the slope stability analysis of the three-dimensional landfill site, it is found that the bank slope of the reservoir is steep and prone to instability failure. In most studies, only the instability of the landfill is of concern, but the bank failure is ignored. In the process of landfill operation and management, while considering the capacity of the landfill, the stability of the bank slope should also be paid attention to, and if necessary, bank slope reinforcement or slope ratio improvement should be carried out.

An Integrated Environmental Assessment of MSW Management in a Large City of a Developing Country: Taking the First Steps Towards a Circular Economy Model

Most of the municipal solid waste (MSW) in developing countries ends up in landfills. For example, more than 95% of the MSW generated in Latin America is disposed of in some type of landfill. Factors such as high organic compositions, low recycling rates and poor control over the disposal sites greatly increase the environmental impacts associated with MSW management in this region, resulting in increased emissions of greenhouse gases (GHGs) and runoff of leachates. Therefore, local governments in Latin America are making efforts to transition to more “circular” management models for MSW. This is the case in the Guadalajara Metropolitan Area (GMA), the third most populous city in Mexico, where the implementation of the following two mechanical biological treatment (MBT) alternatives are being considered: 1) a high-capacity mechanical sorting facility with no biological treatment and 2) a medium-capacity mechanical sorting facility coupled with a composting process. Thus, the aim of the present study was to assess the environmental performance of the current MSW management system (baseline) as compared to the two potential MBT alternatives through life cycle assessment (LCA) and sensitivity analyses. Furthermore, by using a SWOT analysis, this study aimed to provide insights into the main economical, sociocultural, legal, political and technological/infrastructure challenges that need to be overcome in the GMA, as well as other cities in developing countries, in order to transition to circular MSW management models. An assessment of global warming potential (measured in Gg CO2-eq/year) indicated that the current MSW management system (baseline) results in the emission of 111.21 Gg CO2-eq/year, while the two potential alternative scenarios displayed a net emissions reduction of 24 and 34%, respectively, due to material recycling and the substitution of petroleum coke with refuse-derived fuel (RDF) in cement kilns. When evaluating abiotic resource depletion (measured in Gg Sb-eq/year), the potential alternative scenarios both outperformed the baseline with savings increases between 3,380 and 3,501%. This result is largely attributed to the decrease in fossil fuel consumption (due to the substitution of petroleum coke with RDF), which provides a potential reduction of 5.62 Gg Sb-eq/year. The sensitivity analysis revealed that several key parameters, such as the fraction of food and plastic wastes in the MSW, can alter the scenario rankings. Recycling of the recovered materials and treatment of the organic fraction were found to be key strategies for a reduction in direct environmental impacts. Additionally, better management of waste picker activities, standardization of landfill operations and enhancement of material separation and selective collection must be addressed prior to the introduction of new treatment technologies. The results of the study herein can assist in the formation of policies to improve the feasibility of MBT implementation and drive the first steps towards a circular economy model in the GMA, as well as other cities within Latin American and Caribbean regions with similar characteristics.

Health risks and perceptions of residents exposed to multiple sources of air pollutions: A cross-sectional study on landfill and stone mining in Danang city, Vietnam

Health risks and perceptions of residents living nearby landfills or stone mines/quarries have been well documented; however, the multiple impacts of these two pollution sources have yet to be investigated. This study aims at giving insights into the impacts of residents exposed to two pollution sources in Danang city, Vietnam: Khanh Son landfill and Phuoc Tuong quarry. In this cross-sectional study, 7-point-Likert scale questionnaires were used to collect information from 314 respondents which were divided into three groups: i) Landfill-Stone mine (LS) exposed group within 1 km from both sources, ii) Stone mine (ST) exposed group within 1 km from the stone mine, and iii) the far-exposed group about 2–3 km from the two emission sites. Air pollutants (including H2S, CH4, and total suspended particles (TSP)) and noise levels were also sampled. In addition, we estimated the potential health risk assessment due to the exposure to hydrogen sulphide in the study areas.The findings have shown that 1) There is a statistical difference (p-value < 0.001) between the two exposed groups and far-exposed group regarding health risks and residents’ perceptions; 2) Compared to the ST exposed group, the LS exposed group statistically showed a higher perception to bad odours and skin diseases; lower satisfaction with regards to the personal health condition and the operation of the landfill; and higher willingness to change current living locations; and 3) There is evidence to indicate that elevated concentrations of air pollutants are associated with the high self-reported health risks and residents' perceptions. Urgent actions should be focused on the LS exposed group, landfill and quarry operations to prevent further adverse health effects.

A review of cementitious alternatives within the development of environmental sustainability associated with cement replacement

The environmental conditions of sustainable improvement in manufacturing consist of the application of secondary raw materials in the design and structure of new structures. Presently, the demand to construct new structures is growing rapidly, especially in the developed world. All of the construction and demolition (C&D) waste is deposited in open landfills in easily reachable spaces, which leads to numerous environmental problems. The utilization of this waste in concrete will help in sustainable and greener development. The main goals of using waste, by-products, and recycled materials to develop sustainable concrete are to reduce carbon dioxide emissions, which are a cause of environmental pollution and climate change, and to enhance exploitation of waste, which creates problems of disposal that can be solved by completely or partially replacing concrete components. This paper aims to provide a comprehensive overview of the published literature on the replacement of cement in concrete such as rice husk ash (RHA), olive stone biomass ash (OBA), recycled coal bottom ash (CBA), and recycled palm oil fuel ash (POFA), and its effects on the characteristics of concrete like workability, density, compressive strength, splitting tensile strength, flexural strength, shrinkage, and durability. Also, this paper aims to review the impact of the replacement of cement on sustainability. The author has also included recommendations for future research.

Proposal for the Management of Solid Urban Waste Generated in Naranjillo, Capital of the District of Luyando, Perú

To meet the objectives, the solid urban waste generated in Naranjillo is characterized and quantified and its adequate management is proposed. For this purpose, the methodology of the United Nations Urban Management Program, the calculation of the sanitary landfill through the guide for the design, construction, and operation of manual sanitary landfills, by Jorge Jaramillo, was used. The study determined 91.14% of usable solid waste and 8.86% of unusable solid waste whose final disposal should be in the sanitary landfill. 75.72% are organic waste that have the biological treatment in the composting plant; 15.42% of inorganic solid waste should be recycled through classification in the manual segregation plant, both components should enter the economic cycle. The volume of the landfill calculated until 2030 corresponds to 1555.80m 3 for a projected population of 4695 inhabitants in that year: with an urban solid waste production of 1575.86 Kg/day. The municipality of the district of Luyando by applying the proposed model of urban solid waste will improve the quality of life of its inhabitants by avoiding the contamination of water, soil, air, and the deterioration of the landscape.

Prediction and management of household solid waste generation during COVID-19 pandemic in Bandung City using system dynamics model

Abstract WHO declared a novel coronavirus in humans as Coronavirus Disease 2019 (COVID-19) on February 2020, and Indonesia as well as Bandung City have been suffering from COVID-19 since the first case in March, 2020. Currently, the outbreak of COVID-19 has occurred for more than a year. The COVID-19 pandemic had a severe impact on the environment, like the enhancement of household solid waste as a result of work and school from home policies to decrease the rates of COVID-19 cases. This study aimed to predict the amount of household solid waste generation and analyze the waste management during COVID-19 in Bandung City using a system dynamics model. Data for model input was obtained from questionnaire to 200 respondents from Bandung spread across the sub-districts. The results revealed that the household solid waste generation was increased by 1.3 to 3.8% compared to the year before the COVID-19 pandemic. The composition of household solid waste was dominated by food and plastic waste, which have increased to 76.43% and 25.81%, respectively. The system dynamics model has predicted the household waste generation from three management scenarios for 30 years of model simulation. Scenario I: the household solid waste was totally managed by a local sanitary agency (existing condition); Scenario II: each household manage their waste by recycling; and Scenario III: the utilization of a local waste bank to manage the waste. The scenario III showed the most effective waste management to reduce the amount of household solid waste generation up to 24% by using waste bank. This scenario can be applied for more prolonged landfill operations up to 17 years.

Assessment of current solid waste management practices, community perceptions, and contributions in the City of Kigali, Rwanda

Socioeconomic development, urbanization, an uncontrollable massive population rate, and higher living standards in cities increase the amount and variety of solid waste generated. If it accumulates, it degrades the urban environment, affects natural resources, and causes health problems. Dumping sites are becoming an increasing source of concern for Rwanda municipalities, particularly in Kigali City, and they are a significant source of pollution in the air, water, and land. This article aims to assess current solid waste treatment practices in the City of Kigali and evaluate the local community attitudes, participation, and perception in waste management. This research uses a mixed method to understand better how the waste management system performs in Kigali City. The data was collected by distributing a questionnaire to respondents, conducting interviews with communities, and contacting all companies that collect and recycle waste, government institutions, and other sources such as national household surveys and reports. The quantity and type of municipal solid waste (MSW) varies in each identified district. The findings indicate that personal attitude and perception are essential while engaging in waste management practices. There are poorly implemented WM laws and regulations. Due to incomplete combustion, open landfill fire produces smoke, hazardous gases, and particles that pollute the air. In addition, methane concentrations can reach up to 50 percent of landfill gas composition at the maximum anaerobic decomposition. These gases participate in the increase of greenhouse gas effect, global warming, and climate change.

Municipal solid waste incineration (MSWI) ash co-disposal: Influence on per- and polyfluoroalkyl substances (PFAS) concentration in landfill leachate

Municipal solid waste incineration (MSWI) ash is often managed through co-disposal with unburned wastes in landfills, a practice previously reported to result in enhanced leaching of pollutants (e.g., heavy metals) in landfill leachate. The objective of this study was to evaluate the effect of co-disposed unburned wastes on per- and polyfluoroalkyl substances (PFAS) in MSWI ash landfill leachate. Leachate was collected from four landfills containing MSWI ash, either as a sole waste stream or co-disposed of with sewage sludge and MSW screenings. Samples of ash and unburned materials were collected and assessed separately for leachable PFAS in the laboratory. All samples were analyzed for 26 PFAS. Results showed that greater ash content was associated with lower leachate PFAS concentrations. The pure ash monofill exhibited the lowest PFAS in landfill leachate (290 ng L−1) while the landfill contained a large amount of unburned waste had the highest PFAS (11,000 ng L−1). For laboratory leaching tests, average ∑26PFAS concentration in lab ash leachate (310 ng L−1) was 10 and 24 times lower than observed in lab sewage sludge leachate (3,200 ng L−1) and lab MSW screenings leachate (7,500 ng L−1), respectively. Leachate from the ash-only landfill had ∑26PFAS concentration similar to what was measured in the ash itself. On the contrary, ∑26PFAS concentration in co-disposal landfill leachates were similar to those in PFAS-rich unburned waste itself, regardless of the percentages of landfilled unburned wastes. We hypothesize that leachate generated in co-disposal scenarios preferentially flows through PFAS-rich unburned materials and that biotransformation of precursors enhanced by unburned waste degradation further contributes to higher concentrations of terminal PFAS in ash co-disposal sites. Landfill operators should expect PFAS in leachates to be higher when PFAS-rich unburned wastes are disposed of alongside MSWI ash, even if the unburned fraction is small.

Integrating greenhouse gas reduction and waste policy targets to identify optimal waste treatment configurations via Carbon Emission Pinch Analysis

Municipal solid waste (MSW) is a persistent burden in many countries. The heterogeneous MSW characteristic requires a transition from the monotonous treatment strategy to a diversified low-carbon waste treatment configuration. Nevertheless, complex mathematical models hinder the policymakers from adopting scientific-based solutions in the decision-making process, and those models seldom link national greenhouse gas reduction targets to local waste policy targets. This study applies two approaches in constructing Carbon Emission Pinch Analysis to either optimize waste treatment system configurations while considering greenhouse gas reduction and waste policy targets or identify the maximum possible national greenhouse gas reduction based on a waste treatment system configuration. Among the seven types of waste treatment systems studied, the carbon emission factor of material recycling is the lowest (−0.19 t CO2-e/t MSW), whereas open landfill is the highest (0.72 t CO2-e/t MSW). The proposed ten waste treatment configurations indicate a 1.0–2.2% reduction of national greenhouse gas emissions, in which the best-case configuration (i.e., carbon sink scenario) contributes to 3.64% of the national electricity consumption in 2030. This study provides a compendious comparison of waste treatment systems integrated with greenhouse gas reduction and waste policy targets for a more circular MSW management in countries facing the waste disposal dilemma.

Leachate characteristics: Potential indicators for monitoring various phases of municipal solid waste decomposition in a bioreactor landfill

Leachate is a contaminated liquid generated during the bio-chemical decomposition processes of municipal solid waste (MSW) that occurred at semi-solid or solid-state in a bioreactor landfill (BLF). Conceptually, leachate from a BLF is analogous to the urine generated in the ‘human body’, on which the medical practitioners rely to diagnose and remediate ailments. In line with this practice, to monitor the complex MSW decomposition processes, prolonged investigations were performed to establish the temporal variation of different chemical parameters (such as pH, electrical conductivity, chemical oxygen demand, organic- and inorganic carbon, nitrate- and ammonium-nitrogen, sugars and volatile fatty acids) of the leachate collected from different cells (age≈ 6–48 months) of a fully functional BLF in Mumbai, India. Furthermore, to understand the effect of the climate, MSW composition and landfill operating conditions on the rate of the decomposition process, chemical parameters of the leachate obtained from a landfill located in the central part of Poland were compared with the BLF. The study reveals that the chemical parameters, except for the pH, evince a rapid reduction with time and attain a constant value, which indicates the ‘stabilized MSW’. Also, native microorganisms that are an integral part of MSW consume volatile fatty acids within a year in the BLF, which facilitate the rapid transformation of the decomposition process from acidogenesis and acetogenesis to the methanogenesis phase. It is worth iterating here that based on the long-term field study, a convenient and efficient methodology, which is currently missing from the literature, has been established to understand the kinetics of different phases of anaerobic decomposition. This study would be very helpful to the landfill operators, who are interested in accelerating MSW decomposition by augmenting leachate properties.

Regional differences in influence of intermediate cover permeability on perched leachate in landfill

Intermediate cover may act as impervious layers in landfill and form perched leachates, which have adverse effects on the safe operation of landfill. The formation rules of perched leachate mound in different climate regions are not the same and still unclear. To solve this problem, a finite difference method that took account of climate boundaries was conducted. Four typical cities' climate data standing for Chinese climate and 4 permeability parameters of intermediate cover were used in the simulation. The results showed that key to the formation of perched leachate is that the infiltration rate of the leachate is greater than the ks of the intermediate cover. Under arid climate conditions, the infiltrates of the leachate are generally lower than the infiltration capacity of the intermediate cover, and it is not easy to form a perched leachate mound. In humid regions, when the ks of the intermediate cover is lower than 10−5 cm/s, perched leachate forms easily in rainy seasons. The result can be useful to determine the permeability parameters of intermediate cover, especially in humid climate.

Hydrogeochemical evolution and assessment of groundwater quality in the Togo and Dahomeyan aquifers, Greater Accra Region, Ghana

Groundwater quality is generally better than surface water quality but this is not sacrosanct because during recharge and abstraction, groundwater may be subjected to variations due to influence from natural and anthropogenic processes. The Togo and Dahomeyan aquifers are threatened by several anthropogenic activities like dumping of domestic and industrial wastes in open landfill sites. These activities can be sources of groundwater constituents and can pose adverse health effects on humans and the ecosystem but little is known about the hydrogeochemical characteristics of groundwater and its quality in the area. Therefore, the present study is aimed at unravelling the hydrogeochemical characteristics and quality of groundwater in the Togo and Dahomeyan aquifers in the Greater Accra Region of Ghana. A total of 37 groundwater samples were collected and analysed for the concentrations of major ions, minor ions, and trace elements. The results were used to compute water quality parameters like electrical conductivity, sodium adsorption ratio, sodium percent, and magnesium ratio to assess the quality of the water for irrigation purposes. Groundwater shows acidic to slightly alkaline pH and evolved from Mg–Na–HCO3, Ca–Na–Mg–HCO3, Na–Ca–Mg–HCO3–Cl to Na–Mg–Ca–HCO3 with other mixed water types, which reflect the local geology. Geochemical modelling indicates that groundwater is supersaturated with respect to goethite and hematite and saturated with respect to calcite, aragonite, and dolomite in some samples. Hydrochemical graphing and multivariate statistical analysis indicate that the chemistry of groundwater in the area is primarily controlled by an interplay of chemical weathering, mineral dissolution, ion exchange reactions, agricultural activities, and sewage disposal. The groundwater is not entirely suitable for drinking purposes because of high concentrations of EC, TDS, Na+, Cl−, F−, Fe, Mn, Pb, Cr, and Ni, which exceed their maximum permissible limits provided by the World Health Organization. The computed parameters for assessing the quality of the water for irrigation reveal that 64.9% of the samples are suitable for irrigation purposes. However, 35.1% of the samples show very high salinity and sodium hazard and thus, are unsuitable for irrigation purposes. Therefore, it is recommended that mixing of the high salinity and sodium water with low salinity and sodium water can improve crop yields.

UAV-based landfill operation monitoring: A year of volume and topographic measurements.

Unmanned Aerial Vehicles (UAVs) for photogrammetry operations configures a technology capable of extracting quantitative information from land surface in a fast, accurate and safe way, reproducing it in high-resolution Digital Elevation Models (DEMs) and orthomosaics. Due to the operational efficiency of this technique, there is an interest in evaluating its quality compared to other methodologies traditionally used for monitoring procedures in infrastructure earthwork. In sanitary landfills, operational monitoring is directly linked to topographic services, as these are the main source of data for the geometric assessment of the work. In this context, the aim of the study was to verify accuracy and application range of UAV photogrammetry for geometrical and volumetric measurements, when compared to usual conventional survey procedures using total station, and how it can aggregate reliable data to landfills monitoring activities. UAV flights were carried on monthly basis, over a year. For accuracy analysis, the maximum RMSE error observed was 7.1cm for horizontal axis and 0.37cm for vertical axis for the monitoring period. Volumetric measurements were tested using Ground Control Point (GCPs) configurations distributed first at the landfill perimeter, which resulted in an average difference of 9% from that calculated by conventional topography, and measurements where GCPs were placed also in the landfill operation fronts, when a 4% average difference diverging from conventional topography was obtained. The conclusion shows that such monitoring routines, when performed periodically, provides a robust database with a high level of operational performance, covering effective information for preventive and corrective monitoring in landfill projects.

Challenges of Landfill Operation in Tanjungpinang, Kepri, Indonesia

A controlled landfill is one of the ways to manage the waste generated, which is laid between open dumping and sanitary landfill. Ganet Landfill is the only one landfill located at the Tanjungpinang, Indonesia. Currently, this landfill face the operational problem and abundant to the environmental problems. This study consists of the three objectives, (i) to study the current problems of controlled landfill operation; (ii) to determine the challenges of controlled landfill operation affect the surrounding environment, and (iii) to suggest an improvement and innovation to the controlled landfill operation. The case study was conducted at Ganet Landfill in Tanjungpinang, Indonesia as a controlled landfill. The qualitative method with the semi-structured interview instrument used in this research. The data collection involved four respondents from Ganet Landfill office and the Department of Public Housing and Peoples’ Settlement Riau Archipelago. Finding shown that the most dominant current problem in Ganet landfill is the lack of manpower, lack of heavy equipment, lack of land for the future, lack of infrastructure leading to unloading points. While the challenges faced in operating Ganet Landfill as a controlled landfill are meeting the needs of the present and future communities and spread knowledge about landfills among staff and the community. Therefore, the suggestion the improvement and innovation to the Ganet Landfill are change the controlled landfill to the sanitary landfill, cooperation with the private sector to improve the landfill operation, increase waste processing from households, and increase community concern about the landfill to make sure the controlled landfill is in line with sustainable development at the local and national perspective.

Synergistic optimization of electrocoagulation process parameters using response surface methodology for treatment of hazardous waste landfill leachate

Leachate treatment is an essential and integral part of solid waste management system, and its efficient treatment becomes more crucial when the leachate is produced from industrial or hazardous waste landfills (HWLs), as it is multi-fold more toxic than the leachate produced from municipal solid waste landfills (MSWLs). Electrocoagulation has appeared to be a promising technology for treating complex wastewater including MSWL leachate, but specific treatability studies dedicated to HWL leachate are rarely available, and thus pose a demand for fundamental and advance research in this area to bridge the existing gap. The current study delves into systematic design of experiments to check the treatability of HWL leachate through electrocoagulation, considering reduction (maximum) in chemical oxygen demand (COD) as a response variable. Response Surface Methodology (RSM) was used for design of experiments and process optimization and three-dimensional surface response was also created to understand the relationship among process parameters and response variables. After extensive experimental trials and data analysis, it was observed that electrocoagulation can be used as a potential treatment technology for leachate with Galvanized Iron (GI) as preferable electrode material and it resulted up to 90% reduction in COD under optimized condition. Significant reduction in other parameters was also observed with a removal efficiency of 58.1%, 63.6%, 42.4%, 52.5%, 54.7% and 84% for cadmium, zinc, phenolic compounds, lead, TOC, and colour, respectively. The results showed that Electrocoagulation can be used as a replacement of currently practised energy extensive treatment technologies like multiple effect evaporators, which are used by landfill operators for managing their HWL leachate. The methodology and results from this research may be utilized by the researchers and operators of HWL landfills to decide the treatment trail for HWL leachate.

Wedge method for landfill stability analysis considering temperature increase.

The increase in landfill temperature often results in shear strength reduction of both the solid waste and the liner, which leads to slope instability. However, very few landfill slope analysis methods can simultaneously consider the effect of temperature on the shear strength of the waste solid and the liner. In this study, based on the strength parameters of the liner and waste with temperature, a wedge method for translational failure analysis of landfills considering temperature increase was established. The results showed that rising temperatures caused by biochemical degradation at the bottom and middle of the landfill reduced the anti-slide force of back slope more than that of bottom slope. With the leachate level increasing, the effect of temperature rise on landfill stability became obvious. The feasibility of the proposed wedge method was verified by the engineering case study of Xiaping Landfill, Shenzhen, China. This study probably provides important guidance for the design, operation and management of municipal solid waste landfills.

BEHAVIOR OF CONCRETE COMPRESSIVE STRENGTH BY UTILIZING FLY ASH AND WOOD POWDER

The release of CO2 into the atmosphere, which is caused by cement manufacturing, is a substantial cause of global warming. Besides, rapid industrial expansion has prompted concerns about how to properly dispose of industrial by-products. Many of them might pollute the environment if discarded in open landfills. In recent years, utilization of natural and industrial waste as a supplement to cement or aggregates has become incredibly popular as a means of improving concrete performance, satisfy rising cement needs and achieving environmental sustainability. A blend of fly ash (as a cement substitute) and wood powder (as a fine aggregate substitute) might be a viable alternative for determining the impact on the concrete mixture. In this study, fine aggregate is substituted with 5%, 10%, and 15% wood powder, and cement is replaced with 10%, 15%, and 20% fly ash to get the best combination in terms of compressive strength. When a 5% wood powder replacement is done with fine aggregate and a 10-15% replacement of cement is made with fly ash, compressive strength improves between 2.19-3.58% and 4.12-7.51% for 28 days and 90 days. It is found that if the quantity of wood powder in concrete exceeds 5%, the compressive strength drops dramatically. Besides that, concrete constructed with a 20% fly ash and 15% wood powder mixture disintegrated while curing. However, concrete containing up to 10% wood powder and up to 15% fly ash has been demonstrated to be effective when compared to plain concrete. Furthermore, based on the compressive strength test results of concrete at 28 days and environmental sustainability, a considerable proportion of construction expenses may be saved by substituting 10-15% of cement with fly ash.

Slope stability analysis of a landfill subjected to leachate recirculation and aeration considering bio-hydro coupled processes

During the operation of landfills, leachate recirculation and aeration are widely applied to accelerate the waste stabilization process. However, these strategies may induce high pore pressures in waste, thereby affecting the stability of the landfill slope. Therefore, a three-dimensional numerical analysis for landfill slope stability during leachate recirculation and aeration is performed in this study using strength reduction method. The bio-hydro coupled processes of waste are simulated by a previously reported landfill coupled model programmed on the open-source platform OpenFOAM and then incorporated into the slope stability analysis. The results show that both increasing the injection pressure for leachate recirculation and maximum anaerobic biodegradation rate will reduce the factor of safety (FS) of the landfill slope maximally by 0.32 and 0.62, respectively, due to increased pore pressures. The ignorance of both waste biodegradation and gas flow will overestimate the slope stability of an anaerobic bioreactor landfill by about 20–50%, especially when the landfilled waste is easily degradable. The FS value of an aerobic bioreactor landfill slope will show a significant reduction (maximally by 53% in this study) when the aeration pressure exceeds a critical value and this value is termed as the safe aeration pressure. This study then proposes a relationship between the safe aeration pressure and the location of the air injection screen (i.e., the horizontal distance between the top of the injection screen and the slope surface) to avoid landfill slope failure during aeration. The findings of this study can provide insights for engineers to have a better understanding of the slope stability of a bioreactor landfill and to design and control the leachate recirculation and aeration systems in landfills.