The remediation and management of old municipal solid waste (MSW) landfills are pivotal for advancing urban ecological sustainability. This study aims to systematically assess the mechanical properties, environmental behaviors, and synergistic mechanisms of remediated landfill-mined soil-like material (SLM) through advanced oxidation and stabilization processes. The results indicate that synergistic remediation with advanced oxidation and stabilization processes significantly increased the mechanical strength of stabilized SLM to over 0.6 MPa, and reduced the organic content by about 20 %, making it suitable for reuse in geotechnical engineering. The choice of oxidizing agents markedly affected the mechanical properties of stabilized SLM; for example, the application of sodium percarbonate in conjunction with stabilized materials further enhances the strength by simultaneously promoting the pozzolanic reaction. Furthermore, the heavy metal leaching behaviors of the stabilized SLM were found to be environmentally safe. The enhanced performance of stabilized SLM is primarily attributed to the synergistic effects of oxidation and pozzolanic reactions. The advanced oxidation process decreases organic matter content and increases its stability by reducing the proportion of readily decomposable O-alkyl C. Concurrently, pozzolanic reactions produce ettringite crystals and C-(A)-S-H gels, which not only fill micropores and improve particle bonding but also aid in heavy metal immobilization through surface adsorption, complexation, and physical encapsulation. These insights provide a comprehensive understanding of the remediation processes and resource recovery potential of SLM from old MSW landfills.

It is a fact that the temperature inside the waste mass is higher than the ambient outside the landfill. However, only a few experimental works have tried to address the effect of such elevated temperatures on the mechanical behavior of waste. Accordingly, developing a constitutive model based on experimental achievement is still incipient. In this paper, results from experimental literature and the results of a complementary testing campaign aided in better understanding and modeling the waste thermo-mechanical behavior. An existing model framework by the authors is extended to incorporate thermal effects on the waste bulk and fibrous reinforcement particles. The model predicted fairly the mechanical behavior of waste in terms of deviatoric stress, pore water pressure, and volumetric strains in drained and undrained triaxial tests performed on samples at different temperatures and with different plastic contents. Values of deviatoric stress predicted by the model for two specific axial strains are compared with experimental results, considering all the tested samples, proving the model's capabilities in reproducing the waste's overall behavior. Considering an axial strain of 20%, the probabilities of the model error occurrence in the range of +/- 25% are 55% and 67% for CIU and CID tests, respectively.

Rampant industrial growth and urbanization have caused a wide range of hazardous contaminants to be released into the environment resulting in several environmental issues that could eventually lead to ecological disasters. The unscientific disposal of urban and industrial wastes is a critical issue as it can cause soil contamination, bioaccumulation in crops, groundwater contamination, and changes in soil characteristics. This article explores the impact of various industrial and urban wastes, including petroleum hydrocarbons (PHs), coal-fired fly ash, municipal solid waste (MSW) and wastewater (MWW), and biomedical waste (BMW) on various types of soil. The contamination and impact of each of these wastes on soil properties such as compaction characteristics, plasticity, permeability, consolidation characteristics, strength characteristics, pH, salinity, etc is studied in detail. Most of the studies indicate that these wastes contain heavy metals, organics, and other hazardous compounds. When applied to the soil, PHs tend to cause large settlements and reduction in plasticity, while the effect of coal-fired fly ash varies as it mainly depends on the type of soil. From the studies it was seen that the long-term application of MWW improves the soil health and properties for agricultural purposes. Significant soil settlements were observed in areas of MSW disposal, and studies show that MSW leachate also alters soil properties. While the impacts of direct BMW disposal have not been extensively studied, few researchers have concentrated on utilizing certain components of BMW, like face masks and nitrile gloves to enhance the geotechnical characteristics of weak soil. Soil remediation is required to mitigate the contamination caused by heavy metals and PHs from these wates to improve the soil quality for engineering and agricultural purposes, avert bioaccumulation in crops, and pose less environmental and public risks, and ecotoxicity. Coal-fired fly ash and biomedical waste ash contain compounds that promote pozzolanic reactions in soil, recycling and reuse as soil stabilizers offer an effective strategy for their reduction in the environment, thus complying to sustainable practices. In essence, this study offers a contemporary information on the above aspects by identifying the gaps for future research and mitigation strategies of contaminated soils.

The escalating global issue of soil pollution by heavy metals, particularly incinerated municipal solid waste fly ash (IMSWFA), necessitates effective remediation strategies. The prevailing approach for safely disposing and utilization of IMSWFA involves high-temperature sintering. In this work, we propose a cost-effective method to produce ceramsites by utilizing IMSWFA, municipal sludge (MS), contaminated soil (CS), and iron tail slag (ITS). After conducting a comprehensive analysis and comparison of outcomes obtained from orthogonal experiments and single-factor experiments, it was determined that the optimal preparation conditions for achieving desirable results are preheating at a temperature of 400 degrees C for 15 min followed by sintering at a temperature of 1150 degrees C for 10 min. The optimal ratio of raw materials for ceramsites is 15 % IMSWFA, 15 % MS, 58 % CS, and 12 % ITS. The ceramsites, prepared in accordance with the specified process and raw material ratio, exhibit remarkable properties including robust stability, minimal water absorption, reduced weight, and elevated cylindrical compressive strength. The ceramsites demonstrate an exceptionally high heavy metal loss ratio ranging from 91 % to 100 %, while exhibiting significantly lower leaching quantities of these metals compared to the raw materials. Additionally, aging tests of ceramsites were performed under UV light and acid/alkaline etching to simulate the real-world environment. This work can be utilized to investigate the long-term environmental impact of ceramsites derived from municipal solid waste (MSW), thereby making a valuable contribution to the advancement of solid waste management technology.

In cold and saline soil areas, concretes usually experience multi-factor erosions, such as freezing- thawing cycles (FTCs), drying-wetting cycles (D-Ws), and salt erosion. To promote green and sustainable development of the construction industry, municipal solid waste incinerator bottom ash (MSWIBA) was adopted as a partial replacement for conventional fine aggregates in concretes. In this study, the coupled effects of the D-Ws and salt erosion (i.e., 5 % NaCl solution and 5 % Na2SO4 2 SO 4 solution) were experimentally conducted to investigate the mechanical and micro- structural properties of ordinary and MSWIBA concretes. The results showed that D-Ws had a negative effect on the mechanical properties of concretes. The depth and width of cracks in concretes increased with the D-Ws raised. During the D-Ws, the influence of salt solution on concretes could be divided into two stages. Initially, the filling effect of salt crystals was beneficial to the development of concrete strength. Subsequently, salt crystals accumulated in concretes caused cracks, and accelerated the deterioration of concrete specimens. Meanwhile, sodium sulphate reacted with hydration products in concretes to produce some expansive substances, the evident diffraction peaks of expansive substances (e.g., gypsum and ettringite) had been clearly observed after D-Ws. Thus, the damage effect of 5 % Na2SO4 2 SO 4 solution (SS) to concrete structure was more serious than that of water (WT) and 5 % NaCl solution (CS). Furthermore, the total porosity of the concrete specimens generally decreased with the MSWIBA substitution rate increased. There was an optimal MSWIBA content for concretes to obtain the excellent mechanical and microstructural properties. In detail, when the substitution rate of MSWIBA was between 0 % and 33.0 %, it had an excellent effect on improving the pore structure of concretes. Specifically, the compressive strength of concretes was larger than 35.0 MPa when the substitution rate of MSWIBA with natural river sand was between 24.8 % and 57.8 %, whereas the substitution rate of MSWIBA should not exceed 33.0 % exposed to D-Ws. This study could provide a significant reference for the sustainable development of concretes in cold and saline soil areas, as well optimization and innovation usage of MSWIBA.

Inadequate management of solid waste stands out as a primary cause of environmental contamination, leading to a decline in groundwater quality in the vicinity of landfill sites. Though landfills are required by federal regulation to have liners formed by plastic or clayey layers, these liners tend to have leaks, which can result in landfill leachate percolation into the soil and aquifers, contaminating nearby water sources and further damaging ecosystems. Currently, the elevated nitrate (NO3-) concentration in groundwater spurred by landfill leachates is becoming a growing global concern. Various regions across the world present groundwater NO3- concentrations exceeding the threshold limit (50 mg/L) of WHO for drinking purpose. In this scenario, it is requisite to consider and develop highly efficient and affordable solutions for the long-term management of groundwater resources. Therefore, a bibliographical review was conducted in this paper by searching literature in Web of Science, ScienceDirect, Google Scholar, SpringerLink, PubMed, and Scopus to analyze NO3- pollution in groundwater caused by landfill leachates and explore the impacts of landfills and NO3- pollution on the environment and human health. In addition, this review also presents an overview of the leachate treatment technologies to remove nitrogenous compounds, particularly NO3-. This review entails a worldwide appraisal of groundwater NO3- pollution to comprehend the human health risks and aid in optimizing groundwater quality. A resulting framework developed in this review provides an improved grasp of the link between inadequate landfill management and adverse environmental and health outcomes and urged all stakeholders to address the issue of solid waste to ensure environmental and human health. Overall, the results emphasize the need for immediate action and collaborative efforts to mitigate these impacts and ensure the long-term sustainability of waste management practices.

The rational disposal and resource utilization of municipal solid waste incineration bottom ash (MSWI-BA) is an urgent problem to be solved. This study explores the impact of MSWI-BA and its finely ground powder (MSWIBAP) as fine aggregates and solidifying agent components in pre-mixed fluidized solidified soil (PM-FSS) by conducting tests on the unconfined compressive strength and volume stability. Additionally, it analyzes the composition and microstructure properties of hydration products using techniques such as XRD, TG-DSC, MIP, and FTIR. The results demonstrated that the PM-FSS incorporating MSWI-BA and MSWI-BAP exhibited a dense microstructure and excellent mechanical properties, with the main hydration products being Aft, C-(A)-S-H gel, square crystal, etc. The volume deformation of PM-FSS with MSWI-BA and MSWI-BAP increased, but it did not affect the development of its mechanical strength. MSWI-BA can be used as a solidifying agent component and fine aggregate for the preparation of PM-FSS, achieving its resource utilization.

This study investigates the geotechnical performance of municipal solid waste fines (MSWF) stabilized with xanthan gum and agar gum. As urbanization escalates, the challenge of managing MSW becomes more critical, especially in India, projected to produce up to 436 million tonnes annually by 2050. Landfill mining yields material with poor engineering properties, necessitating effective stabilization techniques. This research evaluates the efficacy of xanthan and agar gums in enhancing the geotechnical properties of MSW fines. Various tests, including compaction, triaxial, and unconfined compressive strength, were conducted on samples subjected to different curing periods. The results indicate a substantial improvement in the mechanical properties of MSW fines treated with agar gum, including a maximum increase of 58% in unconfined compressive strength (UCS). Microstructural examinations confirm enhanced interparticle bonding, while leachate analysis shows a notable reduction in heavy metal release. Statistical assessments underscore the significance of curing time in determining the final properties of the treated MSW fines. Overall, agar gum emerges as a more effective biopolymer for MSW fines stabilization, with curing duration playing a vital role in achieving optimal geotechnical characteristics. These findings offer valuable insights for selecting appropriate bio-treatment methods for heterogeneous materials like MSW fines.

Plastics within municipal solid waste (MSW) are non-degradable. As MSW continues to degrade, the relative content of plastics rises, and particle gradation may also change. Moreover, throughout the landfilling process, MSW is subjected to various stress conditions, potentially influencing its mechanical properties. This study explored the effects of varying plastic contents, different particle gradations, and distinct stress paths on the mechanical properties of MSW, and consolidated drained triaxial tests of 42 groups of reconstituted MSW specimens were conducted. The results showed that there was an optimal plastic content of 6-9 % for MSW, where the shear strength of MSW was higher than that of MSW with other plastic contents. When the stress path changed from TC45 to TC72, the optimal plastic content of MSW changed from 6 % to 9 %. As the plastic content increased, both the cohesion and internal friction angle of the MSW initially increased, then subsequently decreased. The impact of plastic content on cohesion was more pronounced than on the internal friction angle, especially at larger strains. Under various stress paths, MSW with distinct particle size distributions demonstrated diverse stress-strain behaviors. Traditional criteria for evaluating well-graded conditions in soils are not suitable for MSW. The effect of gradation on the cohesion of MSW is essentially due to the predominant role of fiber content; the relationship between gradation and the internal friction angle in MSW is complex and correlates closely with the content of both coarse and fine particles, as well as fibers. This study serves as an essential reference for predicting deformations in landfills and analyzing the stability of landfill slopes.

Landfill failure threatens the safety of surrounding cities and causes soil and water pollution. High water levels can usually spur landfill failure. With the presence of earthquake, landfill instability is triggered in a greater possibility. However, the dynamic response and failure mechanism of landfills with high water level subjected to earthquakes are not yet clearly understood, and relevant experimental studies are quite scarce. This study includes a series of seismic centrifuge tests to investigate the seismic response of the landfill at different water levels. An improved method is proposed to prepare synthetic municipal solid wastes (MSWs) with similar staticdynamic properties to the actual MSWs. The failure and evolution mechanism of landfills with high water levels induced by the earthquake is revealed. Significant transitions are observed in the dynamic response of deformation, acceleration, and pore-water pressure as the water level changes. With the rise of water level, the settlement at the top of the landfill decreases first and then increases, while the horizontal displacement at the toe increases slowly, followed by a sudden drop; the acceleration amplification coefficient in the middle of the landfill increases first and then decreases; the dynamic pore-water pressure gradually decreases from positive to negative, but oscillates at the moderate water level. Three failure criteria and a hydro-earthquake coupled failure limit are proposed to demonstrate the combined effect of water level and earthquake on landfill stability. The test results provide a basis to establish seismic failure standards for landfills with different water levels and guide the seismic instability design of landfills with high water level.