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Ethylene propylene diene monomer (EPDM) rubber is used in critical sectors such as national defense, military, and aerospace. However, it has performance limitations under high temperatures, affecting its dynamic mechanical properties, creep, and stress relaxation. To overcome these limitations, rare earth cerium oxide (CeO2) was incorporated as a filler into EPDM in this study, which enhances its properties and makes it suitable for the demanding applications. It could be seen that the CeO2‐enriched EPDM has significantly improved mechanical characteristics at elevated temperatures. The Young's modulus of CeO2‐enriched EPDM increased by about 100 %, while the energy storage modulus reaches a maximum increase of around 140 % at 165 °C. The addition of CeO2 improves its damping properties, provides better creep and stress relaxation resistance, and results in greater residual strain recovery. At room temperature, the impact on the stress relaxation rate at 50 % strain is minimal for the material EPDM, and it is almost negligible for the material EPDM/CeO2.These findings demonstrate that CeO2‐enriched EPDM has enhanced performance under high‐temperature conditions. Under elevated temperature conditions, EPDM enriched with CeO2 exhibits enhanced mechanical properties, superior creep resistance, and stable stress relaxation behavior, rendering it more adept at withstanding the rigorous conditions encountered in aerospace applications. [ABSTRACT FROM AUTHOR]

Vegetation has been found to improve the hydrological performance of landfill cover. However, existing studies ignore the effects of hydrogen sulfide (H2S), which forms the toxic odour generated from municipal solid wastes. Hydrogen sulfide is a potential signalling molecule in regulating plant-stomata aperture, but how the plant–hydrogen sulfide interaction affects the water–gas transport in soil remains unknown. This aim of this study was to investigate the effects of hydrogen sulfide on Bermuda grass growth and its influence on water–gas transport in unsaturated soils. Soil columns, with and without vegetation, were prepared and fumigated with different hydrogen sulfide concentrations. These columns were subjected to controlled drought and rainfall sequentially. The results showed that grass leaves almost wilted without hydrogen sulfide fumigation due to the Pythium diseases caused by the antecedent waterlogged conditions. In contrast, hydrogen sulfide fumigation promoted grass growth because of the fungicidal effects of hydrogen sulfide. In drought, hydrogen sulfide fumigation caused stomata closure, which resulted in a lower matric suction in the vegetated soil than that without hydrogen sulfide fumigation. Accordingly, hydrogen sulfide concentration reduced because of oxidation by metal oxides in soil. Upon subsequent rainfall, more infiltration but lower matric suction was observed in vegetated soils than was found in the bare case, whereas hydrogen sulfide concentration decreased continuously due to gas dissolution in the pore water. Direct application of laboratory findings herein to field cases should be used with caution, because the applied continuous lighting and low evapotranspiration rate of the soil column tests may not be representative of field conditions. [ABSTRACT FROM AUTHOR]

Concrete pipes both reinforced and unreinforced still serve as efficient subsurface infrastructure, especially when used as culverts and sewer lines. In which its structural performance greatly affected by pipe-soil interaction through installation types. In this study the effect of concrete bedding on the behavior of buried unreinforced concrete pipe is investigated through full-scale experimental testing program which the concrete pipes are embedded in gravelly sand soil that is loose and dense. With thickness of 30 cm over pipe crown and subjected to different surface loadings. Seven standard 300 mm internal diameter precast unreinforced concrete pipes were evaluated in a lab soil box test facility. Two loading conditions are used, namely earth fill that simulated by a uniform loading platform, and wheel load that simulated using a patch loading platform with dimensions of 254×508 mm2 (10×20 in.2), which is used by AASHTO to mimic the wheel load of an HS20 truck. The results demonstrated that controlled installation utilizing dense compaction granular backfill could achieve 70% of the pipe strength acquired by employing the typical concrete bedding of the indirect design approach. For concrete bedding under patch loads, the greatest bedding factor (ratio between the supporting strength of buried concrete pipe to the three-edge bearing test strength) obtained is 4.53. The failure loads of pipes with concrete bedding is greater than pipes with compacted soil bedding by 30% for uniform loading and 43% for patch loading. [ABSTRACT FROM AUTHOR]

At the end of 2020, Talang Gulo Landfill Site 1 in Jambi City was officially closed due to overcapacity. Municipal solid waste disposal has shifted to the Talang Gulo site 2 with a life expectancy of ± 90 years based on the design plan. However, this is difficult to realize because segregation and composting are not optimal, so more than 90% of the waste transported to the final processing site (TPA) is in a landfill. Thus, landfill mining was executed to utilize excavated landfill waste as a material and energy. It was carried out at depths of 3, 5, and 7 meters with an estimated sample age of > 9 years. The mixed landfill samples contained 55.6-66.2% moisture content, 50.3-80.6% volatile content, 19.4-49.7% ash content, 2.6-4.2% fixed carbon, and 3.5-5.7 MJ/kg calorific value. Furthermore, the landfill waste was dried using the biodrying method, combining fresh and landfill waste in the pile composition. The ratio of landfill waste to the addition of fresh waste is 1:0 (control pile), 1:1, 1:2, 1:3, and 1:4. The drying method reduced moisture content of 9-29.1% with a lower calorific value of 5-6.8 MJ/kg. Based on statistical analysis, it is known that waste ratio has a significant effect on moisture content. Based on the weighting results, the optimum mixture ratio is 1:1 (pile 2). [ABSTRACT FROM AUTHOR]

This study is a critical review of municipal solid waste (MSW) hydraulic conductivity that includes investigation of the influence of vertical stress, dry unit weight and degradation. A total of 56 studies were compiled that included laboratory-, pilot- and landfill-scale hydraulic conductivity experiments. Compacting waste and increasing vertical stress reduce MSW hydraulic conductivity via reshaping the pore networks throughout the waste matrix, reducing the void ratio and increasing tortuosity. However, the magnitude of reduction in hydraulic conductivity is dependent on stress, waste composition and decomposition. Solid waste decomposition can have opposing effects on hydraulic conductivity. Some studies have indicated that an increase in MSW decomposition results in particle size reduction and settlement that reduces the void ratio and decreases hydraulic conductivity. Conversely, some studies indicate that waste decomposition reduces the solid mass, which increases the void ratio and creates larger flow paths that increase hydraulic conductivity. The data compilation, observations and key findings from this study are beneficial for solid waste practitioners to improve design, analysis and operation of MSW landfills. [ABSTRACT FROM AUTHOR]

This article reports on how management approaches influence methane emissions from landfills. The project team created various landfill operational scenarios for different regions of the planet with respect to waste composition, organic waste reduction and landfill gas recovery timing. These scenarios were modelled by applying a basic gas generation model according to the United Nations Intergovernmental Panel on Climate Change (IPCC) recommendations. In general, the IPCC's recommended modelling parameters and default values were used. Based on the modelling undertaken, two options stand out as being the most effective methane mitigation measures in a wide range of conditions throughout the world: (a) early gas recovery and (b) reduction of the amount of biodegradable organic waste accepted in a landfill. It is noted that reduction of organic input to any given landfill can take many years to realize. Moreover, suitable alternative processing or disposal options for the organic waste can be unaffordable for a significant percentage of the planet's population. Although effective, organic waste reduction cannot therefore be the only landfill methane mitigation measure. Early landfill gas recovery can be very effective by applying basic technologies that can be deployed relatively quickly, and at modest cost. Policymakers and regulators from around the globe can significantly reduce adverse environmental impacts from landfill gas emissions by stimulating both the early capture and flaring and/or energy recovery of landfill gas and programmes to reduce the inflow of organic waste into landfills. [ABSTRACT FROM AUTHOR]

In environmental sciences, comprehending the movement of subsurface contaminants is crucial for formulating effective remediation measures. The self‐potential (SP) method has become a common tool for delineating landfill contamination plumes. Contaminant diffusion or migration represents dynamic processes, with corresponding SP responses evolving over time. However, conventional SP interpretation approaches have predominantly relied on static single‐frame inversion, overlooking the temporal correlation in time‐series SP data and resulting in cumulative errors. To tackle this challenge, we introduce a novel method for time‐lapse inversion of SP data leveraging particle filtering. This approach recursively refines the priori state model through posteriori observations to achieve precise estimations of dynamic models. Specifically, a spherical polarization model is deployed to establish the state equations of underground contaminant diffusion and transport models, whereas the observation model is derived through forward modeling. The proposed method is validated using two synthetic examples and one lab‐measured dataset. The findings demonstrate the efficacy of the time‐lapse inversion algorithm in precisely estimating dynamic models, outperforming static single‐frame inversion based on the particle swarm optimization algorithm. The posteriori distribution of particles approximates a bell‐shaped distribution, with the true state closely positioned near the peak probability. Therefore, we affirm that conducting time‐lapse inversion of time‐series SP data through particle filtering is an effective and dependable approach for accurately estimating dynamic model states. [ABSTRACT FROM AUTHOR]

• Developed GHG emission models for incineration and landfilling. • Analyzed influencing factors of GHGs from MSW from space-time dimension. • Analyzed GHG emission pattern of legacy MSW. • Forecasted GHG emissions from MSW before 2030. The municipal solid waste (MSW) management is significantly contributing to global greenhouse gas (GHG) emissions. Analyzing the emission pattern of GHGs from MSW is essential for formulating appropriate carbon mitigation policies. Based on IPCC Models, GHG emissions from MSW were calculated in Chinese provinces from 2004 to 2021 by landfilling and incineration operations, separately. Landfilling and incineration generated approximately 1271 MtCO 2 -eq and 198 MtCO 2 -eq from 2004 to 2021, respectively. GHG emissions from landfilling increased from 2004 to 2020 and declined in 2021, while GHG emissions from incineration demonstrated an increasing trend with three distinct growth stages. A panel regression model was then employed to identify the key factors influencing GHG emissions. GDP and population are positively related to GHG emissions from landfills, while PCCE is negatively related to GHG emissions from landfills. GDP and PCCE have a positive impact on GHG emissions from incineration, while population showed no significant impact. Multi-expression programming was used to develop an explicit model, forecasting GHG emissions from MSW by 2030. From 2022 to 2024, GHG emissions from landfills will quickly decrease, while GHG emissions from incineration will rapidly increase. Subsequently, the GHG emission rate of incineration will slow down, and GHGs from landfilling will slowly decrease due to no MSW for landfill disposal. The methods and results provide insightful information for policy-makers and waste management sector. [ABSTRACT FROM AUTHOR]

[Display omitted] • Partitioning of CBZ and SD was determined in landfill refuse-leachate phase. • K d values were concerned with organic matter and specific surface area of refuse. • K d values were related to leachate properties (pH and humic acid content). • Different sorption mechanisms of CBZ and SD in refuse-leachate phase were proposed. Pharmaceuticals have been detected at high concentrations in landfill leachate and refuse, which may pose potential long-term environmental impacts. The interaction of pharmaceuticals between leachate and refuse contributes to their retention through in situ sorption, thereby mitigating this impact. However, limited efforts have been made to describe the distribution characteristics of pharmaceuticals in the refuse-leachate phase. In this study, two refuse and three leachate samples were used to obtain partitioning coefficients (K d) for two typical pharmaceuticals, carbamazepine (CBZ) and sulfadiazine (SD), with campus soil as a comparison. Landfill refuse exhibited higher K d values (12.36 ± 0.90 and 19.76 ± 1.96 mL/g for CBZ and 1.90 ± 0.34 and 6.27 ± 0.58 mL/g for SD in two samples, respectively) than campus soil (3.73 ± 1.31 mL/g for CBZ and 0.81 ± 0.26 mL/g for SD), influenced by refuse properties such as higher organic matter (OM) content and specific surface area (SSA). The influence of leachate pH on K d values depended on the electrostatic interaction between the species of target pollutants and negatively charged refuse. The effect of humic acid (HA) was related to its binding with target pollutants in solution and its competition with them for sorption sites. Electrostatic repulsion, hydrogen bonding and π-π interaction were the proposed mechanisms in SD sorption on refuse, while hydrogen bonding participated in the sorption of CBZ. The results will help aid the understanding of the distribution of pharmaceuticals in the refuse-leachate system and improve corresponding management strategies. [ABSTRACT FROM AUTHOR]

This research provides the first assessment of the leachate impact on water sources near the newly installed Landfill and Recovery Center (LRC) in Tangier, Morocco, which has been operational since the beginning of 2021. The investigation involved the analysis of microbiological and chemical parameters in water samples from four community wells and five surface water sources in the M’harar and Tahaddart Wadis during the dry season. Chemical analysis focused on detecting heavy metals, which were quantified using Atomic Absorption Spectrometry. Microbiological analysis involved assessing the presence of Fecal Indicator Bacteria utilizing the membrane filtration method. The findings reveal alarmingly high levels of fecal bacteria and distinct spatial water quality patterns, with a notable gradient of bacteriological contamination in groundwater sources surrounding the LRC. The highest concentrations were noted at well P.1, located about 3.6 meters from the LRC, while at well P.4, located 1 km away, there is a regression in bacterial and metal concentration, suggesting leachate percolation, likely due to construction faults and inadequate waste management. The heavy metal concentrations remained below the World Health Organization’s maximum acceptable values. Nevertheless, the overall results of the M’harar and Tahaddart Wadis waters show no leachate runoff. The study highlights the urgent need to improve the installation of proper leachate collection tanks and treatment systems as well as robust environmental monitoring, to protect the ecological integrity of the Biological and Ecological Interest Site (SIBE) of the Tahaddart region and safeguard public health. This study is limited by its focus on a specific geographic area and the timing of sampling, which restricted the groundwater analysis to only four wells. Future research should include sampling across different seasons and a broader range of wells to provide a more comprehensive understanding of water quality dynamics. [ABSTRACT FROM AUTHOR]

This article investigates the pivotal role of non-hazardous waste landfills in achieving greenhouse gas (GHG) reduction objectives within the European Union (EU).1 This study leverages the experience of key stakeholders in the European landfilling, assesses the efficacy of 'best-in-class' landfill installations, evaluates their potential impact on GHG reduction, and offers concrete recommendations for operators and policymakers. 'Best-in-class' landfills exceed the commonly accepted best practices by implementing all the following practices: (1) an anticipated capture system during the operating phase, (2) prompt installation of the final cover and capture system, with use of an impermeable cover, (3) operated as bioreactor, keeping optimal humidity, (4) adequate maintenance and reporting, (5) recovery of captured gas and (6) treatment of residual methane emissions throughout the waste decomposition process. The main finding is that switching from the actual mix of practices to 'best in class' practices would reduce by ~21 MtCO2eq (−36%) the emissions due to the degradation of waste landfilled between 2024 and 2035, compared to the 'business-as-usual scenario', while also providing a renewable energy source, bringing potential avoided emissions and energy sovereignty. The findings underscore that in addition to implementing the organics diversion and waste reduction targets of the EU, adopting 'best-in class' landfill practices has the potential to bolster energy recovery, mitigate emissions and stimulate biomethane production, thereby advancing the EU environmental goals. [ABSTRACT FROM AUTHOR]

A first-order kinetic model for the simultaneous anaerobic–aerobic degradation of municipal solid waste (MSW) is presented in the study. The model incorporates the effect of oxygen concentration on anaerobic degradation, enabling the coexistence of anaerobic and aerobic processes within specific oxygen ranges. The model can thoroughly consider the impacts of temperature, moisture content, oxygen concentration, and free air space (FAS) on the degradation rates of five substrates, i.e., holocellulose, non-cellulosic sugars, proteins, lipids, and lignin. The model was successfully verified against two experimental results. The sequential model underestimates both compression strain and degradation ratio, with peak underestimation ratios of 8.7% and 9.2%, respectively. Using the simultaneous model, the effects of anaerobic age, temperature, and aeration rate on landfill aerobic remediation efficacy are quantitatively assessed. Two evaluation criteria, namely the advance rate of aerobic remediation stabilization time (Rt) and the degradation rate after 100 days of aerobic remediation ( λ 100 a ), are adopted. The results indicate the following: (1) Rt is more sensitive to anaerobic age and temperature, while λ 100 a is more affected by anaerobic age and aeration rate; (2) under optimal conditions, Rt and λ 100 a can reach 86.3% and 70.9%, respectively. The present model provides a crucial theoretical framework for evaluating aerobic remediation effectiveness in both anaerobic sanitary landfills and informal landfills, offering valuable insights for practical implementation and management. [ABSTRACT FROM AUTHOR]

In the context of the shift toward a closed-loop economy, soil-like fractions from landfills are increasingly seen as a potential raw material. Pollution, including potentially toxic elements (PTEs), limits the use of soil-like fractions. The study objective was to assess the level of contamination with PTEs and the ecological risk of the soil-like fraction from a landfill using an interval method on the basis of a quantile analysis. Quantile analysis allows visualization and interpretation of data based on statistical principles using a cumulative distribution function for the data. Quantiles divide the entire dataset into equal parts by probability, and they indicate the proportion of observations that have a value less than or equal to a given quantile. A study was conducted at a landfill in Volgograd. The contents of Cd, Ni, Pb, Hg, Cu, and Zn were studied in a soil-like fraction. The contents of Hg, Pb, and Zn were low and did not pose any risks to the environment. Cd, Ni, and Cu were the main reasons for the contamination of the soil-like fraction. Quantile analysis has shown that the soil-like fraction is polluted unevenly and is described by several contamination levels. The pollution level with PTEs in the soil-like fraction is low, with a probability of 27–31%. The other part of the soil-like fraction has a pollution level ranging from moderate to very high. The environmental risk of a soil-like fraction is associated with Cd and Ni. With a probability of 23.5%, a soil-like fraction is a high environmental risk and requires a responsible attitude and measures to ensure environmental safety. With probabilities of 29.4% and 47.1%, the complex potential environmental risks of a soil-like fraction are low and moderate, respectively. The soil-like fraction located at a depth of more than 2.5 m has a low level of pollution and a low environmental risk. Potentially, this part of a soil-like fraction can be isolated and, after detoxification, used. The significance of this research lies in providing a novel approach to evaluate the ecological risk of soil-like fractions from landfills, which can inform more effective sustainable waste utilization practices in landfill mining. [ABSTRACT FROM AUTHOR]

Geomembrane (GM) is a kind of cost-efficient material for pollutant barriers in landfills, while defects can occur during the installation or service periods, resulting in a mixed-type boundary condition (MTBC) at the top surface of the underlying soil layer (SL). In this study, a novel boundary transform method is employed to handle the MTBC problem of axisymmetric transport of organic contaminant through defected GM, and a semi-analytical solution is derived to evaluate the concentration profiles in the spatiotemporal domain. The proposed solution is in the cylindrical coordinates that can incorporate the diffusion and dispersion processes, as well as the concentration condition in the GM defect. The discretization method, integral transforms and corresponding inverse transforms are applied to obtain the semi-analytical solution, which is demonstrated to be effective compared to the numerical results. The model is applied to predict the migration characteristics of organic contaminant in several cases, followed by discussions to evaluate the influencing roles of defect rate, anisotropic coefficient, and segment number. Results indicate that the existence of defects substantially reduces the barrier capacity of the GM layer, and the contaminant migration time varies in several orders of magnitude for different MTBCs. [ABSTRACT FROM AUTHOR]

This paper presents a design method for liner systems of municipal solid waste (MSW) landfills with high leachate heads based on the breakthrough time of an indicative contaminant (Chloride). The performance of liner systems with varying thicknesses of compacted clay liner and attenuation layer was assessed. The single composite liner consisting of a geomembrane and a 0.75-thickness compacted clay liner can meet the 50-year breakthrough time requirement of the liner system for cases with the thickness of the attenuation layer >3 m and the average height of waste HD < 60 m. The double liner system consisting of two geomembranes with one single 0.3 m-thickness compacted clay liner, as proposed in the Chinese landfill standards, cannot meet the 50-year breakthrough time requirement of the liner system, especially for large-scale landfills (e.g. HD > 60 m). The double composite liner with two composite liners consisting of a geomembrane and a 0.3 m-thickness compacted clay liner can be used for a landfill with an average height of over 60 m. Different liner systems for other cases with different average design heights of waste and the thickness of the attenuation layer were proposed. They can be easily used for MSW landfills with high leachate heads. [ABSTRACT FROM AUTHOR]

[Display omitted] The Sudokwon landfill (SL) in the Seoul metropolitan area, South Korea, is among the world's largest landfills, striving to curtail landfill gas (LFG) emissions and achieve carbon neutrality by 2050. Since 2005, the SL Management Corporation (SLC) has measured LFG emissions (i.e., methane (CH 4) and carbon dioxide (CO 2)) using a dynamic flux chamber proposed by the US EPA. However, uncertainty prevails in validating the reduction of LFG emissions due to the limited spatiotemporal data coverage. In 2020, an eddy covariance (EC) system was installed to enhance measurements, revealing highly fluctuating LFG emissions driven by waste layer LFG production, LFG collection, and atmospheric pressure changes. During the study period, the annual CH 4 emission increased slightly from 465.0 ± 4.2 to 485.5 ± 6.4 g C m−2, while that of CO 2 decreased by 2/3 (from 408.7 ± 16.5 to 270.6 ± 18.8 g C m−2), primarily due to the doubled CO 2 uptake by the vegetated topsoil. Our first long-term (March 2020 to February 2022) quasi-continuous monitoring using EC (with a gap-filling and partitioning technique based on Random Forest) emphasizes the difficulty of temporal upscaling of discontinuously observed surface emissions to quantify the LFG inventory and the need for continuous observations or suitable proxies (e.g., atmospheric CH 4 concentration). [ABSTRACT FROM AUTHOR]

[Display omitted] • PMOB is an economical solution to reduce landfill CH 4 emissions. • Both single- and two-phase flow models are used for calculating LUGM. • LUGM doesn't reflect gas flow rate into MOL. • A novel PMOB design is proposed with a trapezoidal MOL-GDL interface. • Trapezoidal MOL-GDL interface enhances total gas flow rate into MOL. Passive methane oxidation biosystems (PMOBs) are developed as an innovative and cost-effective solution to reduce methane (CH 4) emissions from municipal solid waste landfills. A PMOB consists of a methane oxidation layer (MOL) and an underlying gas distribution layer (GDL). The length of unrestricted gas migration (LUGM) has been recently proposed as the design criterion for PMOBs where the LUGM is calculated as the horizontal length along the MOL-GDL interface with the volumetric gas content (θ a) exceeding the threshold volumetric gas content (θ a,occ). This paper examined water and gas migration within three PMOBs with different MOL-GDL interfaces subject to precipitation and evaporation using verified numerical models. The results show that the use of a single-phase flow model underestimates the LUGM values of the PMOB for heavy precipitation events, and a two-phase flow model should be used to calculate both the LUGM and the total gas mass flow rate into the MOL when designing PMOBs. Both zig-zag and trapezoidal MOL-GDL interfaces can redistribute the gas mass flow rate at the MOL-GDL interface, while the trapezoidal MOL-GDL interface slightly outperforms the zig-zag MOL-GDL interface for enhancing the total gas mass flow rate into the MOL when comparing with the planar MOL-GDL interface. The zig-zag and trapezoidal MOL-GDL interfaces allow gas migration in the upper part of each PMOB segment even when the lower part of each PMOB segment was filled with water, and thus have a potential to minimize hotspot formation. [ABSTRACT FROM AUTHOR]

• Estimates of modeled CH 4 emission (E) data for 1,325 U.S. landfills were reviewed. • Operators use two methods to estimate E from landfills with a gas collection system. • First-order decay (FOD) method shows increasing emissions. • Collection efficiency assumption method shows decreasing emissions. • FOD method shows some agreement to remotely sensed national estimates. As part of its commitment to the United Nations Framework Convention on Climate Change, the U.S. annually develops a national estimate of methane emissions from municipal solid waste (MSW) landfills by aggregating activity data from each facility. Since 2010, the U.S. has reported a 20 % decrease in MSW landfill emissions despite a 21 % increase in tons disposed. Operator-submitted data were investigated to understand the causes of this decline. In the U.S., operators of landfills with a gas collection and control system (GCCS) calculate their facility's emissions via two separate approaches – (1) first-order decay (FOD) and (2) collection efficiency assumption (CEA) − and select either result to feed into the annual inventory. The FOD model predicts methane generation proportional to waste disposal and that approach calculated a 19 % increase in total methane generated from 2010 to 2022, whereas generation via the CEA approach decreased by 8.9 %. The amount of measured methane collected has increased 7.5 % for the same years. Discrepancies between the two models' generated methane, assumed gas collection efficiencies, and oxidized methane compound into substantive differences in national estimates. Operators more frequently select the CEA method, which results in decreased national estimates. If only the FOD method was used, U.S. MSW landfill emissions would be 1.3-1.7 times greater than current estimates which is similar to recent extrapolations from remote sensing campaigns in the U.S. Both models contain parameters with large inherent uncertainty. Without measurement methods that continuously quantify both point-source and diffuse emissions, an assessment of either equation's accuracy cannot be made. [ABSTRACT FROM AUTHOR]

• Demonstration of a whole-site flushing technique in an MSW landfill. • Use of bromide and water as tracers in landfill. • Verification of dual-porosity behaviour of MSW. • in situ field-scale estimates of block diffusion time. • Examination of different fill-and-draw flushing scenarios. A fill-and-draw flushing test on a landfill cell containing MSW waste was carried out to examine the operational viability of this method for accelerating the flushing of contaminants and landfill stabilisation. During the fill cycle, 800 m3 of water containing the tracer bromide was pumped into the base of a 0.44 ha landfill cell, resulting in the estimated saturation of 9,400 m3 of waste. Abstraction took place in two phases, during which 1,100 m3 of tracer/leachate was recovered. Samples of leachate were analysed for the tracer, electrical conductivity and indigenous solutes chloride and ammonia. Tracer recovery was between 63 and 72 % for bromide. An estimated 227 kg of ammonia and 575 kg of chloride were removed. Test data was used to calibrate a 1D, dual-porosity model involving advection in a mobile zone, and diffusion into 'blocks' of a less mobile zone. The model fitted well to the early time data, whereas later data appears to have been affected by recharge. The results of this trial demonstrate the possibilities of the 'fill-and-draw' concept using the basal leachate drainage system of landfills as a potential accelerated landfill remediation technique. However, modelling results suggest low contaminant removal efficiency. Including a pause between the fill and the draw cycles improves mass removal. [ABSTRACT FROM AUTHOR]

Emerging contaminants (ECs) present a significant risk to both the ecological environment and human health. Landfill leachate (LL) often contains elevated EC levels, posing a potential risk to localized groundwater. This study aimed to characterize ECs in municipal solid waste landfills (MSWLs) and hazardous waste landfills (HWLs) in northeast (NE) China. One and three HWLs and MSWLs in NE China with varying types, operational years, and impermeable layers were selected as case studies, respectively. Statistical analysis of 62 indicators of nine ECs in leachate and the groundwater environment indicated the presence of perfluorinated compounds (PFCs), antibiotics, alkylphenols (APs), and bisphenol A (BPA). The leachates of the four landfills exhibited elevated concentrations of ECs of 21.03 μg/L, 40.04 μg/L, 14.54 μg/L, and 43.05 μg/L for PFCs, antibiotics, Aps, and BPA, respectively. There was a positive correlation between the highest concentrations of ECs in groundwater and those in leachate as well as with operational duration of the landfill; in contrast, groundwater EC was negatively correlated with the degree of impermeability. This study can guide future management of ECs in landfills and hazardous waste sites in China, particularly in NE China. [ABSTRACT FROM AUTHOR]

Diverting food waste from landfills is crucial to reduce emissions and meet Paris Agreement targets. Between 2014 and 2024, nine US states banned commercial waste generators—such as grocery chains—from landfilling food waste, expecting a 10 to 15% waste reduction. However, no evaluation of these bans exists. We compile a comprehensive waste dataset covering 36 US states between 1996 and 2019 to evaluate the first five implemented state-level bans. Contrary to policy-makers’ expectations, we can reject aggregate waste reductions higher than 3.2%, and we cannot reject a zero-null aggregate effect. Moreover, we cannot reject a zero-null effect for any other state except Massachusetts, which gradually achieved a 13.2% reduction. Our findings reveal the need to reassess food waste bans using Massachusetts as a benchmark for success. [ABSTRACT FROM AUTHOR]

Highlights Environmental hazards caused by the ever‐increasing end‐of‐life (EoL) glass fiber reinforced polymer (GFRPs) composite waste is of major concern for the sustainable development of the industry. Compared to land filling or incineration, pyrolysis is one of the most promising environmentally friendly methods of disposal of EoL GFRPs. Pyrolysis not only results in recovery of clean glass fibers but other valuable products, such as oils. However, long processing time at elevated temperature leads to aggravation of already existed surface flaws along with the structural changes. Therefore, thermal conditioning of glass fibers results in severe deterioration of the strength in recovered fibers and hence limiting the use of recovered fibers to low end‐products. In this study, a new strategy was adopted where instead of complete cleaning of the fibers at pyrolysis stage, the fibers were partially oxidized and the complete removal of char from the surface of glass was done during hot alkaline etching. This strategy was opted to enhance the quality of the required fibers while reducing the processing time. The results showed ~200% increase in strength of fibers after the combined treatment of pyrolysis and post etching compared to the just pyrolyzed samples with etching time of just 1 min. End‐of‐life panels of GFRPs were pyrolyzed under inert environment of Argon. Residual char was partially removed through post oxidation under flowing air. Hot alkaline etching resulted in complete removal of char and surface defects. Partial oxidation and short etching cycles resulted in improved strength of recovered glass fibers. [ABSTRACT FROM AUTHOR]

This paper introduces a new retaining structure, multi-step cantilever retaining walls pulled locally with geogrids, which has advantages of light weight, quick installation and good applicability for high fill earthworks. Considering log-spiral rotation failure mechanism passing by the heel of the lowest wall members as well as pull-out failure and tensile rupture of the flexible reinforcements, an analytical procedure for seismic overall stability of the retained embankment is proposed based on the upper-bound limit analysis method combined with pseudo static approach. Analysis results of a practical example show that the proposed safety factor and critical slip surface are identical with those by numerical simulation method via FLAC3D. The safety factor increases approximately linearly with the ultimate tension force and the number of reinforcements and nonlinearly with the length of reinforcements within a certain range. Horizontal seismic force has noticeable effect on the slope stability, and vertical seismic effect becomes significant under high horizontal acceleration coefficient. The safety factor is decreasing and the critical slip surface develops obviously towards the embankment exterior as the total number of vertical wall members increases. Besides, the distribution width and setback distance from the walls of the strip surcharge have certain effects on the retained slope stability. [ABSTRACT FROM AUTHOR]

On the path of circular economy, Algeria has initiated several waste management plans. Technical landfill centers (TLCs) installation was one of the adopted solutions. In this context, the purpose of this study is the clarification of TLCs role on realization of social and environmental challenges of circular economy, by analyzing the TLC Bougeurgeur-Guelma Data, while adopting a qualitative approach. Results showed that this center achieves effective results on the social dimension and considerable results on the environmental one. [ABSTRACT FROM AUTHOR]

The Segawe municipal solid waste (SW) landfill in Tulungagung Regency, Indonesia, has currently exceeded its capacity. This study aimed to determine the potential use of dumped SW at the landfill as raw material for the production of refuse derived fuel (RDF). Buried SW samples were collected at a passive zone of the landfill in six locations. The samples were sieved using 10 and 30 mm mesh sieves. A composition analysis was conducted following the ASTM D5231-92 method to sample fractions of greater than 30 mm size. The density was measured according to the weight and volume. The moisture and volatile matter contents were analyzed using the ASTM D2216-10 and D3175-07 methods, respectively. The calorific value was measured using a Parr C3000 bomb calorimeter following the ASTM D5865 method. The buried SW composition was dominated by a fraction size that was greater than 30 mm (79.4%). This fraction was dominantly composed of plastics (71.2%) and had average volatile matter and calorific values which met RDF criteria as a fuel. However, the ash and moisture contents exceeded the standards and, therefore, required appropriate treatments before their applications. [ABSTRACT FROM AUTHOR]

Waste generation has seen a significant surge in the last decade, presenting an urgent need for efficient and sustainable waste management strategies. The mounting piles of landfill waste underscore the criticality of segregating recyclable from non-recyclable waste, a measure that could alleviate numerous global environmental challenges. The increasing necessity to differentiate waste into specific categories such as paper, plastic, and metal is becoming evident; these categories demand distinct disposal and recycling methods. Addressing this automatic detection and segregation issue calls for an automated garbage classification system, achievable through computer vision. This paper introduces a deep learning and computer vision-based Smart Ensembled Framework for Waste Management (SEFWaM) to categorize garbage into various classes for improved waste management. This innovative model employs a fusion of transfer learning—a deep learning technique and boosting to devise an ensembled approach for efficient waste classification. Our proposed approach, trained on the Trashnet 2.0 dataset, has demonstrated superior performance over competing algorithms in terms of Weighted Macro Precision (WMP), Weighted Macro Recall (WMR), Weighted Macro F1-Score (WMF), and test accuracy. The proposed SEFWaM model achieves an accuracy of 94.2% for the considered dataset, proving its superior efficiency over other deep learning-based models. This research thereby contributes to a pressing environmental issue by offering an automated, efficient solution for waste management. [ABSTRACT FROM AUTHOR]

Phosphate tailings are usually used as backfill material in order to recycle tailings resources. This study considers the effect of the mix proportions of clinker-free binders on the fluidity, compressive strength and other key performances of cementitious backfill materials based on phosphate tailings. In particular, three solid wastes, phosphogypsum (PG), semi-aqueous phosphogypsum (HPG) and calcium carbide slag (CS), were selected to activate wet ground granulated blast furnace slag (WGGBS) and three different phosphate tailings backfill materials were prepared. Fluidity, rheology, settling ratio, compressive strength, water resistance and ion leaching behavior of backfill materials were determined. According to the results, when either PG or HPG is used as the sole activator, the fluidity properties of the materials are enhanced. Phosphate tailings backfill material activated with PG present the largest fluidity and the lowest yield stress. Furthermore, the backfill material's compressive strength is considerably increased to 2.9 MPa at 28 days after WGGBS activation using a mix of HPG and CS, all with a settling ratio of only 1.15 percent. Additionally, all the three ratios of binder have obvious solidification effects on heavy metal ions Cu and Zn, and P in phosphate tailings. Graphic Abstract [ABSTRACT FROM AUTHOR]

With annualized expansion rates close to 8 % in 2018 and a projected range of 18–30 % by 2030, wasted batteries are a continual economic and ecological concern due to the growing use of electronic gadgets. The improper preservation and handling of waste discharges are not regulated, which allows for their accumulation in public areas and the release of dangerous materials into the ecosystem at the landfill. To improve the energy properties and lifespan of batteries, current advancements in battery manufacturing mandate the application of novel materials for electrolytes and nanomaterials for cathode materials. Novel battery chemicals may further complicate recycling and containment efforts because it still needs to be determined how much of an influence they will have on the ecosystem. Only a few nations can now recycle mass-manufactured lithium batteries, making up barely 5 % of the more than 345,000 tonnes of garbage produced worldwide in 2018. To provide evidence for policy and legislation, this concise review intends to incorporate current describe and emergent battery pollutant, their adverse ecological aftermath, and ongoing diagnostic techniques. [ABSTRACT FROM AUTHOR]

Groundwater contamination from non-engineered landfills has been extensively documented. However, there is a gap in extensive field research regarding whether engineered landfills can also contribute to groundwater contamination. We selected 62 engineered municipal landfills in Eastern China and collected both leachate samples from the landfills and groundwater samples from nearby wells. Through the analysis of inorganic solute indicators in both groundwater and leachate samples, we explored the impact of landfill leachate on the inorganic solute composition of groundwater. Our findings revealed that over half of the groundwater samples surrounding the landfill sites exceeded recommended drinking water limits for inorganic solutes. The correlation analysis demonstrates a significant relationship between Cl−, SO42−, Na+, and K+ levels in leachate and groundwater, highlighting the direct impact of landfill activities on groundwater quality. Moreover, specific characteristics of the landfill, such as its age, the total waste volume, and geographic location, were found to influence the inorganic solute composition in the groundwater. This effect was apparent in the positive correlations between the age of the landfill and NH3-N, Ca2+, and Mg2+ levels in groundwater, the total waste volume of the landfill and Ca2+ content in groundwater, and the latitude of the landfill and Cl− and HCO3− concentrations in groundwater. This work carries implications for assessing environmental risks associated with engineered landfills and enhancing landfill design, management, and monitoring practices. [ABSTRACT FROM AUTHOR]

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A new landfill cover system, biochar-methanotrophs-clay (BMC) cover is recommended for reducing methane emissions at landfills. It also contributes to decreasing soil permeability and improving soil water retention in a long time, due to highly porous structure of biochar and the growth metabolism of methanotrophs. To determine the effects of biochar content, oxidation aging times and methane-filled days on hydraulic properties, a total of 60 groups of experiments were conducted. The saturated hydraulic conductivity (ksat) was obtained by flexible wall permeameter with controllable hydraulic head pressure. The results showed that the ksat of BMC increased with increasing biochar content and oxidation aging times, while decreased with adding methane-filled days. The soil-water characteristic curves (SWCCs) were obtained with soil suction measured by the filter paper method. The results indicated the water retention capacity of MBC reduced with increasing oxidation aging times but increased with adding methane-filled days. Detected by mercury intrusion porosimetry (MIP), fourier transform infrared spectroscopy (FTIR) and scanning electron microscope (SEM), the differences displayed the changes of pore structures and extracellular polymeric substances (EPS). The oxidation aging of biochar increased the volume of pores, resulting in the increased ksat and the decreased water retention capacity. However, the growing of methanotrophs decreased the volume of pores, resulting in the ksat decreased and the water retention capacity increased due to EPS. No matter how many times the oxidation aging process was experienced, the BMC with longer methane-filled days exhibited relatively lower ksat and better water retention capacity. This implied a more stable barrier capacity to reduce water infiltration in the long term. By combing a series of macro and micro experiments, this paper provides theoretical guidance for the application of biocharmethanotroph- clay mixture to landfill covers. [ABSTRACT FROM AUTHOR]

This study investigates five cases of municipal solid waste (MSW) landfill slope failures in the USA, China, Sri Lanka, and Greece, with the aim of assessing the safety margins and reliability of these slopes. The stability and reliability of the landfill slopes were evaluated under both static and seismic loading conditions, using pre-failure geometries and geotechnical data, with analyses conducted in accordance with Eurocode 7, employing all three design approaches. Under static loading, the factors of safety were close to unity, and reliability indexes ranged from 1.0 to 2.8, both falling below the recommended values set by Eurocode. The landfill slopes failed to meet the stability criteria in Design Approaches 2 and 3, while in Design Approach 1, four out of five landfills met the criteria. Under seismic conditions, safety factors and reliability indexes were significantly lower than the prescribed criteria in all analyses. Sensitivity analyses revealed that in two cases, unit weight and friction angle were the dominant parameters, while cohesion was the dominant parameter in one case. The findings of this study underscore the importance of establishing minimum design requirements for MSW landfill slope stability to mitigate potential risks to public health and the environment. [ABSTRACT FROM AUTHOR]

Composite indicators (CIs) are being utilized more frequently to assess and monitor environmental systems. The revised leachate pollution index (r-LPI) is one such composite indicator used to quantify the pollution potential of landfill leachate on a scale of 5–100. The development of CIs involves several steps, and each of these steps has various methodological choices, each of which could lead to different results. Thereby, the reliability of the quantified pollution potential of leachate may be questioned. This study investigated the techniques for developing the r-LPI, examining decisions related to parameter selection, normalization technique, weighting approach, sub-indicator weights, and their aggregation. As the index developer made the decisions, each of these stages was fraught with uncertainty. The uncertainty in the various stages of the development of r-LPI was quantified using the Monte Carlo-based uncertainty analysis and the sensitivity analysis approach. Uncertainty analysis is a helpful but seldom-used step of index development that identifies the model's most dependable sections. Sensitivity analysis was carried out to ascertain the degree of impact the input parameters have on the r-LPI values. The combined use of sensitivity and uncertainty analysis in this study for the formulation of r-LPI affirmed the transparency, credibility, and accuracy of the index. [ABSTRACT FROM AUTHOR]

• Modelling LFG accumulation and flow below leachate level. • Considerations include buoyant forces and porous interactions. • The mechanisms of LFG accumulation, ascent and discontinuous flow are investigated. • Bubble generation leads to > 20 % rise in the leachate level. Landfills in developing countries are typically characterized by high waste water content and elevated leachate levels. Despite the ongoing biodegradation of waste in the highly saturated regions of these landfills, which leads to gas accumulation and bubble formation, the associated gas pressure that poses a risk to landfill stability is often overlooked. This paper introduces a landfill gas (LFG) bubble generation model and a two-fluid model that considers bubble buoyancy and porous medium resistance. The entire process can be divided into two stages based on the force balance and velocity of bubbles: Bubble Development Stage and the Two-Fluid Flow Stage. The models were validated using a one-dimensional analytical solution of hydraulic distribution that considers bubble generation, as well as an experiment involving air injection into a saturated medium. The mechanisms of LFG accumulation and ascent, leachate level rise, and discontinuous leachate-gas flow were then investigated in conjunction with continuous flow in the unsaturated region. The results indicate that the generation of LFG bubbles below the leachate level can cause a rise in the level height of more than 20%. During the Bubble Development Stage, there is a critical height for bubble ascent, above which the buoyancy exceeds the combined forces of gravity and resistance, resulting in less than 10% of bubbles continuously flowing into the unsaturated zone for recovery. The developed model effectively captures the accumulation and flow of LFG bubbles below the leachate level and could be further utilized to study leachate-gas pumping in the future. [ABSTRACT FROM AUTHOR]

To evaluate the water quality in the Poprad, Kamienica, Dunajec river and the Łubinka stream in the Sącz agglomeration, two series of pilot studies were conducted on raw water samples, with a particular focus on both physical parameters (such as total suspended matter, turbidity, pH, and conductivity) and chemical parameters. The analysis presented increased concentrations of phosphorus, nitrogen, BOD5, COD, chlorides, sulfates, permanganate value, orthophosphates, total suspended matter, specific electrolytic conductivity (PEW), pH levels, and various elements including lithium, magnesium, manganese, potassium, sodium, calcium, and iron. No exceedance of the detection limits for individual pesticides were observed in the waters of the Poprad, Kamienica rivers and the Łubinka stream. Nevertheless, increased concentrations of the insecticide imidacloprid and the fungicide imazalil were detected in the Dunajec river. The primary factors impacting water quality in the Sącz agglomeration are the use of fertilizers, the proximity of wastewater treatment plants, and the presence of landfill sites. [ABSTRACT FROM AUTHOR]

Phytoremediation is an alternative technology for treating leachate by utilizing plants. The objective of this study was to examine the concentrations of total suspended solid (TSS), total nitrogen (TN), and cadmium (Cd) in leachate through the phytoremediation process using Chlorophytum comosum, Echinodorus palaefolius, and Hippochaetes lymenalis. The research was conducted on a laboratory scale with a batch system. The leachate was sourced from the Ngipik Landfill, Gresik, East Java, Indonesia, and was collected from the inlet of the Ngipik Landfill Leachate Treatment Unit. Acclimatization was carried out for 7 days. A range finding test (RFT) was conducted by varying the concentration composition of the leachate compared to tap water, with the planting medium being 25% leachate: 75% tap water, 50% leachate: 50% tap water, 50% leachate: 75% tap water, and 100% leachate: 0% tap water (v/v). The plants used in each reactor weighed 1 kg. The reactors used for the phytoremediation process were plastic boxes with dimensions of 51×32×31 cm. The planting medium consisted of gravel-sized 10-20 mm, with a thickness of 7 cm, and soil with a thickness of 7 cm. This research showed that the average final TSS concentration of the leachate was 25.50 ± 44.37 mg/L. The average TSS reduction efficiency reached 94.90 ± 8.87%. The average final TN concentration of the leachate was 409.42 ± 139.19 mg/L, with an average TN reduction efficiency of 89.73 ± 4.62%. The average Cd concentration in the leachate was 0.0012 ± 0.0013 mg/L, with an average Cd concentration reduction efficiency of 92.30 ± 8.48%. The final TSS and Cd concentrations met the leachate quality standards, with values of 100 mg/L and 0.1000 mg/L, respectively. However, the final TN concentration did not meet the leachate quality standards, as the final TN concentration in the leachate was 60 mg/L. [ABSTRACT FROM AUTHOR]

Located in Douala V (Cameroon), Makepé Missoké is a lowland area that is influenced by the Tongo Bassa and Ngongué rivers. The site has a closed dumpsite, that operated from the 1975's to 2003 for the disposal and storage of domestic waste produced in Douala. Geoelectric profiling (ERT) coupled with seismo-electric imaging was used to characterize the shallow aquifer of the Douala subbasin and map subsurface pollution. Fourteen geoelectrical profiles were deployed between June and August 2018 and March 2019. Along these lines, 49 sets of seismo-electric point data were collected in December 2021. A total of 118 wells drilled (2018) were used to obtain water level and topographic data. The aquifer geometry, hydraulic characteristics, permeability, lithology and leachate plume extent were determined. This survey enables us to visualize waste infiltration and migration within Makepé. The drilled wells indicate that the main lithologies observed are clay, sandy clay, sand, clayey sand and gravel. The leachate plume observed after processing the electric profiles had a resistivity signature of < 10 Ωιτι, and high electrical conductivity are observed in some wells. The leachate migrates within the subsurface along a northwest-southwest trend, where ground water pollution is observed due to leachate infiltration. This infiltration resulted in poor water quality indices in some collected samples. Such pollution is common in unconfined aquifers (< 50 m) due to the absence of a confining layer at the landfill. An increase in resistivity values with depth toward the northeast direction indicates progressive vertical dilution during leachate mineralization. This study integrated geoelectric and seismo-electric tomography with basic water chemistry analysis to effectively characterize the groundwater within the phreatic Quaternary/Mio-Pliocene aquifers of the Douala basin. [ABSTRACT FROM AUTHOR]

Introduction: Methane oxidation biosystems (MOBs) are cost effective engineered systems capable of catalyzing the transformation of CH4 into CO2 biotically, thereby mitigating emissions from landfills. Method: In this study we validate how accurately one can predict the hydraulic behaviour of a MOB using numerical modeling. More precisely how one can identify the length of unrestricted gas migration (LUGM), a critical design criterion for effective methane abatement biosystems. Laboratory experiments were conducted to obtain the material properties for a compost mixed with plastic pellets, and sand. With the water retention curve and air permeability function, we predicted the hydraulic performance of a MOB using Hydrus-2D. We then designed and constructed a MOB and monitored several key parameters for 12 months. The validation of the design methodology was conducted using field measurements, while actual climatic data was used as input in numerical modeling. Results: The air permeability function was an appropriate activation function for determining LUGM. Accordingly, the predicted hydraulic behaviour matched the measured hydraulic behaviour reasonably well, validating the proposed procedure. [ABSTRACT FROM AUTHOR]

To elucidate the time-dependent swelling behavior of landfill sand-bentonite mixture liners under the effect of organic pollutants, an no loading swelling ratio test was conducted on mixtures with varying sand and diesel content. The evolution characteristics of the swelling time curve morphology were investigated. The micro-mechanisms underlying the swelling time effect evolution were explored. The results indicated that the sand-diesel interaction significantly altered the swelling time curve morphological characteristics of the mixture. As the sand content increased, the swelling coefficient at the stable state decreased. However, during the rapid swell phase, dieselcontaminated mixed soil does not exhibit the increase-then-decrease pattern in swell coefficient seen in unpolluted mixed soil. The duration of both the slow swelling phase and the time to reach a stable state were longer. Mechanistic analysis revealed that cation exchange capacity is insufficient to effectively analyze the evolution characteristics of the swelling time curve. Instead, the initial swelling potential of bentonite is the true indicator of the mixture’s swelling properties. The particle size distribution influences the changes in the swelling coefficient during the rapid swelling phase, but diesel alters the particle size distribution, mitigating its impact. The oil sealing effect within intra-aggregate and inter-aggregate pores not only weakened the swelling characteristics of the mixture at all stages but also increased the permeability resistance, thereby reducing the duration of the rapid swelling phase and extending the slow swelling and stable swelling phases. [ABSTRACT FROM AUTHOR]

A series of ternary rare earth – transition metal – tetrelides RET2Tt2 (RE = Sc, Y, La, Lu; T = Fe, Co, Ni, Cu, Ru, Rh, Pd, Ag, Os, Ir, Pt, Au; Tt = Si, Ge) was synthesized by arc melting of the elements and subsequent annealing. The samples were characterized by powder X-ray diffraction and in addition, the structures of REOs2Si2 (RE = Y, La, Lu), LaAu2Si2, LaAg2Ge2 and LaAu2Ge2 were refined from single crystal X-ray diffractometer data. The tetrelides crystallize with the ThCr2Si2 type (I4/mmm) except the platinum compounds which adopt the klassengleiche superstructure of the CaBe2Ge2 type (P4/nmm). The transition metal atoms have tetrahedral tetrel coordination and the tetrahedra condense to layers via common edges. The stacking of these layers leads to Tt−Tt bonds in the ThCr2Si2 type phases and heteroatomic T−Tt bonds in the CaBe2Ge2 type phases. The rare earth atoms fill larger cages within these three-dimensional networks (coordination number 16 with RE@T8Tt8) with site symmetries 4/mmm (ThCr2Si2 type) and 4mm (CaBe2Ge2 type). Systematic multinuclear solid state NMR spectroscopic investigations allowed observing the effect of the involved rare-earth metal, transition metal and tetrel group element, respectively. In particular, 29Si isotropic resonance shifts can be predicted from element-specific increments and interatomic Si–Si bonding interactions manifest themselves in axially symmetric magnetic shielding anisotropies. [ABSTRACT FROM AUTHOR]

The effect of applied stress (20, 60, and 150 kPa) on the diffusion of perfluorooctanoic acid (PFOA) and perfluorooctane sulfonate (PFOS) through a geosynthetic clay liner (GCL) is examined. The diffusion coefficients deduced from GCL diffusion tests for PFOA and PFOS decrease linearly with decreasing final bulk GCL void ratio (increasing applied stresses). The different components of the same GCL are also tested for PFOA and PFOS sorption. No statistically significant sorption of PFOA is observed for any of the components of the GCL. However, some sorption of PFOS onto the cover and carrier geotextiles of the GCL is observed with in an average distribution coefficient, K d ∼2.22 ml/g for the GCL. Permeants containing different PFAS compounds are tested to assess their impact on the Geomembrane (GMB) - GCL interface transmissivity in composite liners. Results show PFAS concentrations up to 20 ppm had negligible impact on the GMB-GCL interface transmissivity. Lastly, the GCL specimens extracted from the diffusion tests are tested for hydraulic conductivity. No impact of PFAS is seen on the hydraulic conductivity of GCLs subjected to high applied loads, but a small increase is seen on the GCLs subjected to relatively low applied stresses. • First diffusion test and parameters on PFAS migrating through a GCL and evaluation of a diffusion coefficient for PFOS and PFOA. • First interface transmissivity test with a PFAS-contaminated solution and assessment of the effect of PFAS on interface transmissivity and evaluation of the effect of PFAS on the hydraulic conductivity of GCL used in transmissivity tests. • Use of a diffusion test to independently verify batch test results for partitioning of PFOS and PFOA to a GCL. [ABSTRACT FROM AUTHOR]

1,4‐Dioxane is a probable human carcinogen and a persistent aquatic contaminant. Cometabolic biodegradation of 1,4‐dioxane is a promising low‐cost and effective treatment technology; however, further demonstration is needed for treating landfill leachate. This technology was tested in two full‐scale moving bed biofilm reactors (MBBRs) treating raw landfill leachate with tetrahydrofuran selected as the cometabolite. The raw leachate contained on average 82 μg/L of 1,4‐dioxane and before testing the MBBRs removed an average of 38% and 42% of 1,4‐dioxane, respectively. First, tetrahydrofuran was added to MBBR 1, and 1,4‐dioxane removal was improved to an average of 73%, with the control MBBR removing an average of 37% of 1,4‐dioxane. During this period, an optimal dose of 2 mg/L of tetrahydrofuran was identified. Tetrahydrofuran was then fed to both MBBRs, where the 1,4‐dioxane removal was on average 73% and 80%. Cometabolic treatment at the landfill significantly reduced the concentration of 1,4‐dioxane received from the landfill at a downstream wastewater treatment and indirect potable reuse facility, reducing the load of 1,4‐dioxane from 44% to 24% after the study. Practitioner Points: Cometabolic degradation of leachate 1,4‐dioxane with THF in MBBRs is a feasible treatment technology and a low‐cost technique when retrofitting existing biological treatment facilities.The MBBRs can be operated at a range of temperatures, require no operational changes beyond THF addition, and operate best at a mass ratio of THF to 1,4‐dioxane of 24.Source control of 1,4‐dioxane significantly reduces the concentration of 1,4‐dioxane in downstream wastewater treatment plants and potable reuse facilities. [ABSTRACT FROM AUTHOR]