Non-hazardous Waste Landfills Research Articles

Investigation on trommeled legacy waste from full-scale mining of old dumpsites: Suitable for valorization or scientific disposal?

The burgeoning interest in resource recovery from old dumpsites has significantly propelled the adoption of Landfill Mining (LFM) in recent years. This study is centred around evaluating the quality of materials recovered from the full-scale LFM activities at two major dumpsites in India, focusing on the valorization potential of the segregated legacy waste. A detailed analysis was conducted on the segregated waste fractions based on particle size (−30 mm, 30 to 6 mm, and −6 mm, as sourced from the sites), employing both batch and column leaching methods across a range of liquid-to-solid (L/S) ratios (0.1–10.0 L/kg).The findings reveal a pronounced concentration of contaminants within the −6 mm fraction compared to the 30 to 6 mm and −30 mm fractions. Column leaching tests revealed a reduction in contaminant concentration, correlating with incremental changes in L/S ratio. Notably, this trend remained consistent across varying particle sizes and specific type of contaminants assessed. Notably, color intensity of leachate reduced significantly from 720 to 1640 Platinum Cobalt Units (PCU) at an L/S ratio of 0.1 L/kg to a minimal 94–225 PCU at an L/S of 10 L/kg. Dissolved salts emerged as a primary concern, marking them as significant contaminants in both leaching methods. The analysis confirmed that the segregated fractions comply with the USEPA Waste Acceptance Criteria (WAC), permitting their disposal in non-hazardous waste landfills. However, the elevated presence of dissolved salts, exceeding reuse limits by 5–35 times, limits their open or unrestricted reuse. Despite this, isolated reuse aligns with regulations from the Netherlands and Germany, suggesting viable pathways for compliant utilization. Geotechnical assessments indicate the potential for repurposing the −30 mm fraction as alternative earthfill and construction material. While heavy metal leaching does not pose significant concerns, the prevalent unscientific disposal practices near urban settlements highlight potential human health risks.This investigation enriches the understanding of the physicochemical properties, leaching behaviour, and reuse potential of segregated legacy waste, offering crucial insights for civic authorities in determining appropriate reuse and disposal strategies for such materials.

Carbon sequestration through mineral carbonation: Using commercial FGD-gypsum from a copper smelter for sustainable waste management and environmental impact mitigation

In this study, we conducted a comprehensive examination of a commercial FGD gypsum produced in a Copper (Cu) smelter process and delved into its potential use as a Calcium (Ca)-rich material for ex-situ mineral carbonation by exploring the partitioning and fate of these metal impurities. The resulting carbonation end-product displayed a calcium carbonate (CaCO3) content of 71.1%, featuring a relatively low CO2 conversion, which may be attributed to the presence of metallic impurities in the commercial FGD-gypsum. Most of these metallic impurities, acting as inputs to the carbonation process, originate from the parent FGD-gypsum matrix. This results in an increased ionic strength within the FGD gypsum, potentially impeding the diffusion of carbon dioxide (CO2) from the gas phase to the aqueous phase. The partitioning and examination of the speciation of major, minor, and trace elements at all stages of CO2 conversion allowed us to propose four potential reaction pathways influencing carbonation efficiency: (i) the formation of metal carbonates, (ii) the production of metal oxides and oxyhydroxides, (iii) the development of metal multiform compounds, and (iv) elements deviating from the outlined patterns. Commercial FGD-gypsum is suitable for acceptance at non-hazardous waste landfills. However, it's essential to highlight that leaching values of As exceed the inert range and non-hazardous waste standards in commercial FGD-gypsum. Although most heavy metal leaching values from the carbonate end-product stay below non-hazardous limits, the release of some heavy metal leachates from the carbonate end-product may limit reuse options for these materials.

Experimental Investigation on the Properties of Street and Sidewalk Cleaning Waste

Abstract One of the municipal waste streams is street cleaning waste, classified under code 20 03 03. They are not considered hazardous waste. Due to the lack of other management technology, they are sent to landfills. This waste, among other things, by its high chloride content especially after winter, can contribute to changes in the salinity of surface and groundwater and soil salinization, which consequently contributes to changes in the local environment and entire ecosystems. As it is deposited entirely in landfills, it also contributes to the salinity of leachate generated here. The Regulation of the Minister of Economy of July 16, 2015, on allowing waste to be deposited in landfills, the total organic carbon in waste deposited in non-hazardous and inert waste landfills must not exceed 5% of dry weight. The purpose of this article is to present a study of the quality of the waste on parameters like water content, organic and mineral fraction in the dry weight of the waste, and fractional separation. The water content of the waste ranged from 12–27%, while the mineral fraction in the dry weight was 91–94%. The smallest fraction below 0.05 mm accounted for 0d 1.8 to 4.5%.

Effects of landfill age, climate, and size on leachate from urban waste landfills in Portugal: A statistics and machine learning analysis

The leachate generated by in urban waste landfills can cause environmental pollution if not controlled and treated. With different proportions of biodegradable waste, urban waste degrades over several phases in anaerobic conditions within a landfill. Using multivariate leachate data from 32 engineered landfills in Portugal, each with a similar waste composition, and all classified as non-hazardous waste landfills receiving urban waste, statistical inference was applied to categorise and deduce significant statistical differences in leachate volume and quality between landfill age, size, and climate, as well as the interactions and effects within these categories. The findings show that the effects of size and age on the leachate volume are prevalent over local, Mediterranean climate conditions; in larger landfills, waste may not be degrading as efficiently as in medium-sized landfills; hotter zones showed higher levels of COD and lower levels of BOD5 than warmer zones, indicating increased biological activity under higher temperature conditions; TN and NH4-N increase significantly with age and size; Cl- also significantly increases with age, showing higher levels, along with SO42-, in hotter zones as well as a concentration effect in the dry season, along with K+; heavy metals maintain levels as landfills age from intermediate to old, with only Cd2+ and Pb2+ showing significant reductions. High correlations between macro inorganics and between heavy metals were found. Cluster analysis showed two main branches, one representing the initial to intermediate stages of anaerobic degradation, and the other the interactions between leaching parameters in the later methanogenic phase of landfill stabilisation.

Assessment of CH4 and CO2 Emissions from a Gas Collection System of a Regional Non-Hazardous Waste Landfill, Harmanli, Bulgaria, Using the Interrupted Time Series ARMA Model

Municipal solid waste (MSW) landfills are among the major sources of greenhouse gas (GHG) emissions affecting global warming and the Earth’s climate. In Bulgaria, 53 regional non-hazardous waste landfills (RNHWL) are in operation, which necessitates conducting studies to determine the environmental risk from the emitted GHGs. This study attempted to assess the CH4 and CO2 emissions from three gas wells of a cell (in active and closed phases, each of 2.5 years duration) in an RNHWL, Harmanli (41°54′24.29″ N; 25°53′45.17″ E), based on monthly in situ measurements by portable equipment, using the Interrupted Time Series (ITS) ARMA model. The obtained results showed a significant variation of the CH4 and CO2 concentrations (2.06–15.1% v/v) and of the CH4 and CO2 emission rates (172.81–1762.76 kg/y) by gas wells (GWs), months and years, indicating the dynamics of the biodegradation of the deposited waste in the areas of the three GWs. Throughout most of the monitoring period (2018–2022), the CH4 concentrations were higher than the CO2 concentrations (% v/v), while CO2 emissions were lower than CH4 emissions (kg/y), a fact that could be explained by the differences in the mass of the two gases. The emissions rates of both gases from GW2 dominated over those from GW1 and GW3, giving a reason to determine the zone of GW2 as a hotspot of Cell-1. On the whole, CH4 and CO2 emission rates were higher in the winter (December–February) and partly in the spring (March–May) compared to summer–autumn (June–November). However, the CH4 and CO2 concentrations and emissions decreased drastically after the Cell-1 closure. The CH4/CO2 ratio (0.68–2.01) by months and gas wells demonstrated a great sensitivity, making it a suitable indicator for the assessment of organic waste biodegradation level in the landfills. The ITS ARMA model confirmed the negative and significant effect of the cell closure on CH4 and CO2 emissions; the correlations found between predicted and observed values were strong and positive (0.739–0.896).

Assessment of industrial by-products as amendments to stabilize antimony mine wastes

The spread of antimony from mine wastes to the environment represents a matter of great concern due to its adverse effects on impacted ecosystems. There is an urgent need for developing and adopting sustainable and inexpensive measures to deal with this type of wastes. In this study the Sb leaching behavior of mine waste rocks and mine tailings derived from the exploitation of Sb ore deposits was characterized using standard batch leaching tests (TCLP and EN-12457-4) and column leaching essays. Accordingly, these mine wastes were characterized as toxic (>0.6 mg Sb L−1) and not acceptable at hazardous waste landfills (>5 mg Sb kg−1), showing also an ongoing Sb release under prolonged leaching conditions. Two industrial by-products were evaluated as amendments to stabilize them, namely deferrisation sludge (DFS) and a by-product derived from the treatment of aluminum salt slags (BP–Al). Mine wastes were amended with different doses (0–25%) of DFS or BP-Al and the performance of these treatments was evaluated employing also batch and column leaching procedures. The effectiveness of DFS to immobilize Sb was much higher than that exhibited by BP-Al. Thus, treatments with 25% BP-Al showed Sb immobilization levels of approximately 33–53%, whereas treatments with 5 and 25% DFS already attained Sb immobilization levels up to approximately 80–90 and 90–99%, respectively. Mine tailings amended with 5% DFS and mine waste rocks amended with 25% DFS decreased their leachable Sb contents below the limit for non-hazardous waste landfill acceptance (<0.7 mg Sb kg−1). Likewise, these DFS treatments were able to revert their toxic characterization. Moreover, the 25% DFS treatment showed to be a long-lasting stabilizing system, efficient at least during a leaching period equivalent to 10-year rainfall with a great Sb leaching reduction (close to 98%). After this long-term leaching process, DFS-treated mine wastes kept their non-hazardous and non-toxic characterization. The amorphous Fe (oxyhydr)oxides composing DFS were responsible for the important Sb removal capacity showed by this by-product. Thus, when DFS was applied to mine wastes mobile Sb was importantly fixed as non-desorbable Sb, showing also a considerable Sb removal capacity in presence of strong competing anions such as phosphate. The application of DFS as amendment presents a great potential to be used as a sustainable long-term stabilizing system of Sb mine wastes.

An integrated characterisation of incineration bottom ashes towards sustainable application: Physicochemical, ecotoxicological, and mechanical properties

Environmental protection is a central concern regarding municipal solid waste incineration bottom ash (IBA) management, but the assessment of waste Hazardous Property HP14 (ecotoxicity) is still under debate. Civil engineering applications may be a suitable management strategy. This work aimed at evaluating IBA regarding mechanical behaviour and environmental hazardous potential, including a biotest battery for ecotoxicity assessment (comprising miniaturised tests), to explore its potential for safe utilization. Physical, chemical, ecotoxicological (Aliivibrio fischeri, Raphidocelis subcapitata, Lemna minor, Daphnia magna, Lepidium sativum), and mechanical (one-dimensional compressibility, shear strength) analyses were performed. The low leaching for potentially toxic metals and ions complied with European Union (EU) limit values for non-hazardous waste landfills. No relevant ecotoxicological effects were found. The biotest battery seems suitable for ecotoxicological assessment in the aquatic ecosystem, providing wide information on waste impact on different trophic/functional levels and chemical uptake routes, simultaneously involving short-duration tests and reduced amounts of waste. IBA presented more compressibility than sand, but its mixture with sand (30%:70%) was closer to sand compressibility. IBA (lower stresses) and the mixture (higher stresses) showed slightly higher shear strength than sand. Overall, IBA presented the potential for valorisation as loose aggregates from an environmental and mechanical viewpoint in a circular economy framework.

Examination of the environmental behavior of phosphogypsum with the application of lab-scale experiment

Phosphogypsum (PG) is a reject of the phosphoric acid production process in phosphate fertilizer industries. The process results in the production of relatively large quantities of PG that it might cause serious environmental and human health concerns. The data of a laboratory investigation of PG are presented here. Lab-scale experiments with lysimeters were conducted in order to simulate and examine the environmental characteristics and the temporal behavior of PG leachates in terms of physicochemical characteristics and chemical composition. Based on the results, leachates from already deposited for many years PG or its mixture with marble powder, seemed to have better pH and conductivity values and lower elemental concentrations compared to leachates from freshly disposed PG. However, the leachates characteristics improve and stabilize in both cases after four days of irrigation or of 1080–1240 mm of rain. Most major elements were found to have minimal leachability, and the material satisfied the environmental limits for its disposal at landfills for inert and non-hazardous wastes.

CONTENTS OF THE COMPONENT ELEMENTS OF THE ECOLOGICAL AND ECONOMIC MECHANISM FOR SELECTION OF LAND PLOTS FOR THE LOCATION OF THE REGIONAL LANDFILL OF SOLID NON-HAZARDOUS WASTE (ON THE EXAMPLE OF LUTSK CLUSTER OF VOLYN REGION)

The need to introduce resource-saving technologies and environmental protection policies both at the international and regional levels, the rapid growth of the Earth's population in recent centuries and the associated processes of industrialization, urbanization, intensification of agricultural production, the increase in the need for energy resources and, accordingly, the increase in the amount of waste, which pollute the environment, further complicates the task of substantiating the locations of new waste disposal facilities and evaluating existing ones. The constituent elements of the ecological and economic mechanism for the selection of land plots for the location of regional landfill of solid non-hazardous waste are highlighted using the example of Lutsk waste management cluster of Volyn region, which solves the above problems. The mechanism makes it possible to determine promising land plots for the location of the regional landfill of solid non-hazardous waste landfills. With its help, one can choose the number of alternative sites required by the specific task. It takes into account primarily the interests of the community, sanitary and hygienic norms, it is economically attractive and preserves territories valuable for the environment. The ecological and economic mechanism for the selection of land plots for the location of regional landfill of solid non-hazardous waste consists of five stages. They include the evaluation of the territory according to economic, ecological, social and sanitary criteria. The elements of the mechanism in the form of five stages are performed separately and sequentially. Since the mechanism for greater visibility and practical use was developed on the example of a real territory, which is identified with the territory of modern Lutsk district of Volyn region, a plot of land was chosen, which is the most optimal for the disposal of waste from this territory. Further actions in the development of this mechanism and its practical value are given. Key words: ecological and economic mechanism, land plot, regional landfill, waste, Lutsk cluster, rejection criteria, distance matrix, competitive criteria.

Cement encapsulation processes to mitigate the risks posed by different types of antimony-bearing mine waste

In this study cement encapsulation processes of different types of mine waste generated from the exploitation of Sb ore deposits were evaluated as a way to manage them and avoid further environmental pollution and the negative impact on surrounding ecosystems. For this purpose, Sb-bearing mine waste rocks, mine tailings, and smelting waste were subjected to cementation processes using Portland cement/calcium hydroxide as binder and different binder:mine waste ratios (10:90–80:20 wt%). The encapsulated materials were characterized for their mechanical behavior (compressive strength test), leaching properties (batch shaking and tank leaching tests), and mineralogical and chemical composition by X-ray powder diffraction, scanning electron microscopy, and electron microprobe analysis. A binder:mine waste ratio of 40:60 wt% was found appropriate to decrease the leachable Sb concentrations at levels below the limit for acceptance at non-hazardous waste landfills. Diffusion was the main mechanism controlling Sb leaching. The obtained effective diffusion coefficients and developed compressive strengths indicate that the encapsulated materials were suitable for disposal. Therefore, according to their leaching and strength characteristics, the encapsulated mine wastes derived using the indicated conditions could be deposited at landfills for non-hazardous waste, thus minimizing the environmental hazards caused by their accumulation in the mine surrounding areas. Additionally, according to the Dutch legislation on the use of waste materials in the built sector, some formulations of encapsulated mine tailings already met the Sb leaching requirement for open (un-insulated) construction applications. Therefore, Sb-bearing mine wastes, especially mine tailings, also present a great potential to be recycled as substitutes for natural aggregates in concrete in construction applications. Antimony was mostly preserved in the original Sb-bearing phases [Fe and Sb (oxyhydr)oxides and tripuhyite] after the encapsulation processes. Of compounds resulting from the hydration of Portland cement, C-(A)-S-H phases predominated, having an important role in attenuating the Sb release from the different types of mine waste; average Sb2O5 contents of 0.12–0.31 wt% were found in C-(A)-S-H phases.

FCC spent catalyst as an alternative reagent in Mo-contaminated hazardous waste enhanced stabilization

Hazardous wastes containing heavy metals must be stabilized through the addition of appropriate and costly chemical reagents before they can be safely disposed in non-hazardous waste landfill. Although effective, this practice can also significantly increase the waste final mass. This work focuses on the possibility of using another Mo contaminated waste, as an alternative reagent, to partially stabilize critical contaminant leaching trough chemical-physical interactions. Thanks to its unusual properties, spent fluid catalytic cracking (FCCSC) catalyst, classified as hazardous waste, was tested here as good candidate for Mo-contaminated waste partial stabilization. Results highlighted that FCCSC can be effective in drastically reducing the Molybdenum leaching below the legal limit for non-hazardous waste landfill disposal while significantly limiting the increase of the final mass of waste to be disposed with a substantial reduction of the industrial treatment cost, landfill volume requirement and overall environmental burden. By minimizing the waste to be landfilled, this research supports both the European directives and policies on sustainable waste management strategies and BAT (Best Available Techniques) for the treatment of industrial wastes within a circular economy framework.

Sustainable Management Strategy for Solidification/Stabilization of Zinc Plant Residues (ZPR) by Fly Ash/Clay-Based Geopolymers

Solidification/stabilization (S/S) of acid waste using Ordinary Portland Cement (OPC) is widely implemented, but, due to the impact on climate change, alternative methods are being investigated. In this work, first, the feasibility of using coal fly-ash/clay-based geopolymers for the S/S of Zn plant residues (ZPR), Cadmium Sponge (CS), and Anode Mud (AM) is proposed as a treatment prior to disposal in landfills. Different variables, such as the type of processing, molding (as-received waste), and pressing (dried waste), and activators, a commercial and an alternative residual sodium carbonate, have been studied. The technical and environmental assessments of the S/S process by means of compressive strength and the leaching of critical pollutants have been monitored. Immobilization efficiencies of Cd and Zn higher than 99% have been obtained by dosing 50% of the acid waste, 6 M NaOH solution (20 min contact time), cured at 75 °C (48 h) and at room temperature (28 days), achieving in the leachates pH values of 7 to 10 and [Cd] and [Zn] &lt; 1 and 2.5 mg/kg, respectively. However, alkaline activation increases As leaching, mainly associated with the clay. Secondly, removing clay from the geopolymer formulation, the optimization of geopolymer parameters, acid waste/geopolymer ratio, liquid/solid ratio, and NaOH molar concentration enables obtaining a significant reduction in the release of As and Cd, and Zn is kept at acceptable values that meet the non-hazardous waste landfill disposal limits for the S/S of both acid wastes.

Effects of Chlorides and Sulphates on Heavy Metal Leaching from Mortar with Raw and Electrodialytically Treated MSWI Fly Ash.

Municipal solid waste incineration (MSWI) fly ash could be used as supplementary cementitious material in cement-based materials. However, heavy metal leaching, such as Cd, Cr, Cu, Pb and Zn, both from the MSWI fly ash and cement-based materials containing MSWI fly ash, remains a persistent obstacle. Here, an up-scaled electrodialytic treatment was used as a pre-treatment to remove heavy metals from MSWI fly ash before using the fly ash in mortar. Mortar samples with 10 wt% replacement of cement with either raw or elecrtodialytically treated MSWI fly ash were subjected to monolithic (in-use scenario) and crushed mortar (end-of-life scenario) leaching tests. The environmental conditions (e.g., exposure to chlorides or sulfates) at the surface of cement-based materials can affect leaching. Acidified H2O, NaCl or Na2SO4 solutions were, therefore, used for the leaching tests. Up to 80% heavy metal removal by the up-scaled electrodialytic pre-treatment was feasible. Regulatory limits for disposing of the MSWI fly ash in non-hazardous waste landfills were exceeded, even if the electrodialytic treatment removed heavy metals. However, leaching from monolithic mortar samples complied with the regulatory limits, while Cr leaching exceeded the regulatory limits for all crushed mortar samples when using NaCl or Na2SO4. Both NaCl and Na2SO4 generally increased the heavy metal leaching yield from fly ash and mortar compared to leaching with acidified H2O. The results of the study suggest that environmental conditions should be taken into account when assessing leaching from cement-based materials with MSWI fly ash.Graphical

ЗМІНА ТАРИФНОЇ СТАВКИ ПОСЛУГИ ЗАХОРОНЕННЯ ВІДХОДІВ У КОНТЕКСТІ СУЧАСНОГО ЗЕМЛЕКОРИСТУВАННЯ (НА ПРИКЛАДІ ЛУЦЬКОГО КЛАСТЕРА ВОЛИНСЬКОЇ ОБЛАСТІ)

n the modern business environment, the issue of ensuring ecological and natural-technogenic safety of the population's vital activities is urgent. The higher the level of urbanization, the more resources are consumed and, accordingly, the amount of waste when using such resources increases. Ukraine belongs to the countries with a high level of urbanization. 94%of all waste in Ukraine is placed in landfills and landfills, which in turn are placed, built and used in violation of environmental safety standards.Regional non-hazardous waste landfills are a modern analogue of solid waste landfills. They require an informed decision regarding their location, area, construction approaches, etc. In this case, there is a need to calculate a new tariff for the waste disposal service.The authors made an attempt to calculate the change in the tariff rate for the waste disposal service in the context of new land uses of non-hazardous waste disposal facilities on the example of a regional non-hazardous waste landfill with an area of 28 hectares near the village of Klepachiv of the Lutsk Territorial Community of the Lutsk District of the Volyn Region. For this purpose, the normative monetary valuation of the plot was calculated for the calculation of the rent on its basis when the plot of land is withdrawn for public needs. Taking into account the costs of design and construction, operation, reclamation and post-operational care of the landfill, the maximum cost of construction of a non-hazardous waste landfill was calculated. Knowing the sum of all costs for the entire design period of the landfill's existence and its reclamation, a monthly tariff is calculated, which must be paid by all residents of the service area of this landfill. A comparison of the project tariff and the existing one is also provided.The results of the comparison of the two tariffs make it possible to further study modern waste management problems and find the most effective approaches to their solution.

Hydrogen-Rich Gas Produced by the Chemical Neutralization of Reactive By-Products from the Screening Processes of the Secondary Aluminum Industry

In the framework of the industry of secondary aluminum, the chemical neutralization of highly reactive materials that come from the pre-treatment screening processes of scraps (beverage cans and domestic appliances) was investigated through experiments in aqueous alkaline solutions. Metallic aluminum-rich by-products are classified, according to EU law, as dangerous waste, as they can potentially develop flammable gases capable of forming explosive mixtures with air. In this way they cannot be disposed of in landfills for non-hazardous wastes if chemical neutralization is not planned and performed beforehand. In this way, these experiments were mainly aimed at unraveling the oxidation rate and at quantifying the production of hydrogen-rich gases from the reactions of the metallic aluminum-rich by-products in a water-rich alkaline (liquid or vapor) environment. Reactions were carried out in a stainless-steel batch mini-reactor with metering and sampling valves, with the resulting gases analyzed by gas-chromatography (GC). The experimental setup was planned to avoid the following issues: (i) the corrosion of the reactor by the alkaline solution and (ii) the permeability of the system to hydrogen (i.e., possible leaks of H2), related to the fast kinetics and short duration of the reactions (which may hinder a pile-up-effect) between the solid by-products and the liquid. The procedure was defined by a controlled interaction process between metals and liquid, using NaOH to increase reaction rates. The experimental runs performed in the mini-reactor proved to be effective for eliminating the reactive metallic aluminum, reaching a maximum hydrogen production of 96% of the total gases produced in the experiments. The relations between gas generation (up to 55 bar of H2 in the experiments, which lasted for four days) and each specific parameter variation are discussed. All the obtained results can be transferred and applied to (i) the possible industrialization of the method for the chemical neutralization of these dangerous by-products, increasing sustainability and workplace safety, (ii) the use of the resulting hydrogen as a source of energy for the furnaces of the secondary aluminum industry itself, and (iii) new technological materials (e.g., “foamed geopolymers”), by using hydrogen as a foaming agent, coupled with aluminosilicate materials, during geopolymeric reactions.

Contaminants of concern (CoCs) pivotal in assessing the fate of MSW incineration bottom ash (MIBA): First results from India and analogy between several countries.

Present study characterizes municipal solid waste incineration bottom ash (MIBA) from three incineration plants in Delhi with an intent to serve the dual objectives: a) assessing the disposal/reuse options for Delhi MIBA, b) evaluating variability in results across the countries (including India) and assessing if is significant enough to influence the fate of MIBA of varied origin. A review on leaching studies of MIBA (50 research papers) was conducted which aided in achieving both the objectives. Delhi MIBA samples were analysed for chemical composition. The two commonly adopted leaching tests i.e., TCLP and EN 12457-2, were conducted and the results were checked against regulatory threshold levels (RTLs) to achieve the first objective. Leaching concentration of the contaminants was compared with the compiled literature and RTLs to accomplish the second objective. The compendium of literature most importantly revealed the physicochemical parameters which are pivotal in determining the fate of MIBA but have been missing from many studies. Ten such parameters were identified: Cr, Cu, Mo, Sb, Cl-,SO42-, Cd, Pb, Ni and Zn and are referred as contaminants of concern (CoCs). Delhi MIBA was found suitable for disposal to non-hazardous waste landfills and unsuitable for unrestricted reuse. CoCs identified in Delhi MIBA were identical to those observed in literature (except Cd, Pb and Zn). The variability in leaching concentration of CoCs, observed from comparative assessment of results, spanned nearly 2 to 3 log10 magnitudes for Cu, Cr, Pb, Sb and Zn while 1 to 2 log10 magnitudes for Mo, Cl-andSO42-.

Partial Stabilization of Mo-Containing Hazardous Wastes Using a Ferrous Sulfate-Based Additive as a Redox Agent

Bottom and fly ashes from a hazardous waste incineration plant, which showed a high concentration of Mo in a leaching test, have been treated to decrease its leachability to below the limit set by the laws in force for admittance to a non-hazardous waste landfill. Both ashes have a basic pH, that is, of around 11–13, therefore most of the molybdenum species were expected to be in the form of molybdate ions (MoO42−), the most soluble molybdenum compound. The aim of the study was to immobilize the molybdate ions using the reducing properties of the Fe2+ ion, in compliance with specific pH and redox potential conditions, which resulted to be crucial for the partial stabilization and immobilization of Mo. The bottom ash was treated both by adding a cost-effective ferrous sulfate-based additive alone and by adding it together with calcium oxide. The fly ash was initially tested with the same ferrous sulfate-based additive; a mix of the former additive and a concentrated solution of sulfuric acid (96%) was then tested to increase the stabilization efficiency. The conducted experiments revealed that the molybdenum leaching behavior can be controlled efficiently by adding ferrous sulfate, under specific pH and redox potential conditions, thereby providing further insight into the sustainable chemical conditions necessary to partially stabilize Mo-containing hazardous waste.

Characterization of Excavated Waste of Different Ages in View of Multiple Resource Recovery in Landfill Mining

With the aim of examining the forcing factors in postmanagement landfills, in this study, excavation waste from nonhazardous municipal waste landfill in Tuscany was characterized for the first time. The specific objective was to estimate the feasibility of sampling and analyzing the excavated waste in order to define its properties and provide information about possible landfill mining projects. Based on the biochemical methane potential assays, it was shown that the excavated waste had not yet been stabilized (i.e., with a production of 52.2 ± 28.7 NlCH4/kgTS) in the landfill, probably due to the low excavated waste moisture content (36% ± 6% w/w). Furthermore, excavated waste has a high calorific value, i.e., 15.2 ± 4.1 MJ/kg; the quantity of combustibles in the industrial shredder waste (16 MJ/kg) was rather modest compared to that of municipal solid waste (20.8 MJ/Kg). In conclusion, during large scale excavation of the landfill, it was possible to evaluate how a dedicated treatment plant could be designed to treat and select waste which might appear in a different category. For excavated industrial waste, detailed mechanical sorting may be convenient for end-of-waste recovery to improve calorific value.

Heavy metal stabilization of industrial solid wastes using low-grade magnesia, Portland and magnesia cements

In this study, stabilization/solidification of electric arc furnace dust and Pb-refining dust was investigated. Stabilization of both wastes was performed by mixing each raw waste with MgO, Portland cement, MgO with MgCl2 (magnesium oxychloride cement), and MgO with phosphate salts (magnesium phosphate cement), at ratios between 5 and 25 wt%. Stabilization/solidification processes were evaluated using EN 12457-4 standard leaching test and stabilized wastes were classified according to the 2003/33/EC Decision. Leachates of stabilized electric arc furnace dust with magnesium oxychloride and magnesium phosphate cement at 10 wt% and 5 wt%, respectively, presented lower concentrations than the regulation limits for disposal in non-hazardous waste landfills; however, the stabilized electric arc furnace dust using MgO or Portland cement at 25 wt% cannot be disposed in hazardous waste landfills. Stabilized Pb-refining dust using MgO or Portland cement at 25 wt% can be disposed of in hazardous waste landfills, whereas stabilized Pb-refining dust with magnesium oxychloride and magnesium phosphate cement at 20 wt% is suitable for disposal in non-hazardous waste landfills. The efficiency of magnesia cements stabilization is attributed to regulation of pH at 10–11, where metal solubility is diminished and positive surface charge of hydrolyzed MgO products results in high adsorption of metalloids oxy-anions.

Hydraulic Conductivity of Compacted Lime-Softening Sludge Used as Landfill Liners

The research goal was to investigate the hydraulic conductivity of compacted lime-softening sludge as a material to be applied to landfill liners. In doing so, the effect of compaction and moulding moisture content on the sludge hydraulic conductivity was assessed. An approximate polynomial k10mean at hydraulic gradients ≥30 for degree of compaction (0.95–1.05) and moulding moisture content (28%–36%) was determined. The results of short-term tap water permeation tests revealed that all hydraulic conductivity values were less than 2.5•10–8 m/s. A lowest hydraulic conductivity of 6.5•10–9 m/s, as well as a corresponding moisture content of 31% were then established. The long-term hydraulic conductivity was measured with tap water, distilled water, NaOH and HCl solutions and municipal waste leachate. The factors of permeating liquids and permeation time significantly affected the initial hydraulic conductivity. The long-term hydraulic conductivity increased for NaOH and HCl solutions and decreased for tap and distilled water. A significant reduction of hydraulic conductivity was observed for leachate permeation. The investigated material met the requirements for the liner systems of inert landfill sites regardless of pH and the limit value for hazardous and non-hazardous waste landfills.