Hazardous wastes and management strategies of landfill leachates: A comprehensive review

Environmental impacts of organic residues from livestock management on soil and groundwater

Leaching nitrogenous compounds and total organic carbon (TOC) from livestock waste can contribute to long-term soil and groundwater quality degradation, particularly under rainfall-driven infiltration. This study investigates the behavior of these contaminants using a combination of laboratory-scale leaching, adsorption, and desorption experiments alongside pilot-scale field monitoring. Results indicate that organic residues derived from livestock waste processing release high concentrations of ammonium (NH₄+-N) and TOC even after extended rainfall exposure (up to 1600 mm). Subsequent desorption phases show nitrate (NO₃--N) emerging as the dominant leached species over time, suggesting microbial transformation and increased subsurface mobility. Field observations confirm these trends, with gradual accumulation of NO₃--N and TOC observed in groundwater near storage areas. This study addresses a significant knowledge gap regarding the long-term dynamics of contaminants originating from livestock waste. The findings underscore the importance of effective containment, consistent monitoring, and appropriate site management strategies to reduce potential impacts on water resources.

Visualization of physicochemical parameters' behavior in leachate, baseliner, and surface water during dry and rainy seasons at a sanitary landfill

Landfill leachate, a major environmental contaminant, is influenced by multiple factors and can migrate through landfill systems, spreading over considerable distances and polluting surrounding ecosystems. This study utilized Ball Mapper, a topological data analysis tool, to qualitatively explore hidden relationships between physicochemical parameters in leachate, surface water, and the baseliner, which can aid in pollution monitoring. The resulting Ball Mapper topological graphs uncovered behavioral similarities and relationships among parameters across different seasonal conditions. The analysis effectively revealed underlying patterns and interconnections by clustering parameters with similar behavior into the same nodes and linking those with hidden similarities. Additionally, Spearman correlation was used to validate the Ball Mapper output, the analysis showed that baseliner and surface water had a weak linear relationship with leachate, except for PO₄3 (r = 0.99), SO₄2⁻(r = 0.71), TSS (r = 0.82), and pH (r = 0.95) in surface water across seasons, which could be as a result of runoff, sediment transport, and environmental factors rather than direct leachate infiltration. The study also demonstrated that while seasonal variations in precipitation influenced leachate volume and pollutant concentrations, the landfill's engineered barriers effectively mitigated the potential environmental impact of leachate migration. Ball Mapper successfully showed the hidden behavior that traditional clustering methods may miss, highlighting its potential as a valuable tool for environmental monitoring.

Application of novel polymer materials for anti-fouling control of landfills: A comprehensive durability evaluation

The novel polymer material is lightweight, environmentally friendly, and offers excellent anti-seepage properties, making it an ideal candidate as a cutoff wall for emergency isolation in landfills, controlling leachate migration. However, limited studies exist on the comprehensive durability of this material. Laboratory experiments were conducted on polyurethane samples through simulating landfill conditions, particularly using dry-wet cycling experiments to mimic seasonal variations in landfill water levels. Pb(NO₃)₂-Zn(NO₃)₂ and CaCl₂ solutions, as representative components of leachate, were evaluated for their effects on the material. The results indicate that the dry-wet process significantly impacted the anti-seepage performance, with the permeability coefficient increasing by 11.7% compared to immersion in pure leachate. The highest impact on material performance was observed in the Pb(NO₃)₂-Zn(NO₃)₂ mixed solution, which led to a 24.2% increase in permeability compared to distilled water, followed by CaCl₂ solution. Two lifetime prediction models yielded a safe service lifetime over 100 years for the polymer material even with heavy metal exposure, utilizing the Arrhenius equation and the WLF (Williams-Landel-Ferry) equation, and high-density materials were recommended. The study confirms the material's strong potential for long-term use, providing a solid foundation for its application in landfill environments. Furthermore, attention should be paid to the destruction of frequent fluctuations in water levels and heavy metals on the polymer cutoff wall.

Taxonomic description and genome sequence of Anaerorudis cellulosivorans gen. Nov. sp. nov., a novel cellulose- and Xylan-degrading bacterium of the Bacteroidota phylum isolated from a lab-scale methanogenic landfill bioreactor digesting municipal solid waste

Bacteria responsible for the anaerobic decomposition of lignocellulosic waste biomass play key roles in the global carbon cycle and possess enzymes with potential industrial application. Here, a novel anaerobic, thermophilic, non-spore-forming bacterium, strain m5T, was isolated from methanogenic enrichment cultures obtained from a lab-scale methanogenic landfill bioreactor digesting anaerobic municipal solid waste. Cells were Gram-stain-negative, catalase-negative, oxidase-negative, rod-shaped, and non-motile. The genomic DNA G + C content was 40.92 mol%. The optimal NaCl concentration, temperature and pH for growth were 0.5-1 g.L-1, 45 °C, and at pH 7.0, respectively. The major fatty acids were C14:0, C16:0, C18:0, C18:1ω9c, and anteisoC15:0. Strain m5T was able to grow in the absence of yeast extract on glucose, fructose, arabinose, cellobiose, galactose, maltose, raffinose, sucrose, lactose, and pyruvate. In the presence of 0.2 % yeast extract, strain m5T grew on wide range of carbohydrates and amino acids, and was able to use complex substrates such cellulose and xylan. Major end products from cellulose and xylan degradation were valerate and propionate. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolate was most closely related to Seramator thermalis SYSU GA16112T (94.42 % 16S rRNA gene sequence identity). Genome-based relatedness as well as both Average Nucleotide Identity (ANI), and Average Amino Acid Identity (AAI) strongly supported that strain m5T belongs to the Dysgonomonadaceae family. Metagenomic analysis of the landfill bioreactor community revealed that the Dysgonomonadaceae family was the most abundant in the constructed bioreactors. Based on its unique genomic features, strain m5T is considered to represent a novel genus, for which the name Anaerorudis is proposed. Moreover, several phenotypic, biochemical, and physiological properties differentiated the novel bacterial strain from related species, indicating that the strain represents a new species for which the name Anaerorudis cellulosivorans sp. nov. is proposed, with strain m5T (= DSM 112743T = ATCC TSD-267T) being the type of strain. This study highlights the biotechnological potential of strain m5T, specifically in the bioconversion of cellulose and xylan, a recalcitrant substrate within lignocellulosic plant biomass, to enhance biogas production.

Treatment of landfill leachate wastewater by chemical coagulation-flocculation, electro-membrane bioreactor, and anaerobic hybrid system

In this study, the treatment of landfill leachate wastewater by chemical coagulation, an electro-membrane bioreactor (e-MBR), and an anaerobic hybrid system was studied. First, chemical coagulation process was applied to landfill leachate wastewater, which is referred to their high organic pollutants. Aluminum sulfate (alum), poly aluminum chloride (PAC), ferric chloride (FeCl3), and ferrous sulfate (FeSO4) were used as coagulants. After determining the coagulant type, pH optimization (6-10) and the amount of coagulant (0.5-2.5 g/l) was optimized. In the chemical coagulation-flocculation experiments, optimum conditions were determined as 1.0 g/l alum at pH 9. At these conditions, chemical oxygen demand (COD), total phenolic contents (TPC), and color analyses were examined and 31.16%, 35.32%, and 24.42% removal efficiencies were obtained, respectively. After coagulation-flocculation pretreatment, the e-MBR system was applied to the wastewater to obtain further treatment. Iron (Fe) electrode and ultrafiltration membrane (UP150) were used in the e-MBR system. 5, 10, and 20 V electric current was applied to the system and time-dependent flux measurements were carried out. COD, TPC, and color analyses were performed in both mixed liquor and membrane permeate. The results indicated that over ˃90% removal efficiency for COD, TPC, and color was achieved when the electric current increased from 5 to 20 V. In addition, it was also observed that the membrane fouling decreased and the flux increased. Since it still did not meet the discharge criteria, the wastewater obtained from e-MBR treatment was subjected to the anaerobic system. After 10 days of incubation, COD, TPC, and color removal were found to be 99.25%, 100%, and 99.57%, respectively. PRACTIONER POINTS: The treatment of leachate wastewater by chemical coagulation, electro-membrane bioreactor, and anaerobic hybrid system was studied. Optimum conditions were determined as 1 g/l alum at pH 9 for chemical coagulation. It was observed that the membrane fouling decreased and the flux increased. COD, color, and TPC removal efficiency were found to be 99.5%, 100%, and 99.6%, respectively.

Joint interpretation of magnetic, transient electromagnetic, and electric resistivity tomography data for landfill characterization and contamination detection

Geophysical techniques have become increasingly crucial for characterizing landfills, offering noninvasive methods for subsurface exploration and contamination assessment. In this study, an integrated geophysical approach-utilizing magnetic, electrical resistivity tomography (ERT), and transient electromagnetic (TEM) surveys-was employed to characterize the Weidenpesch landfill in Cologne, Germany and assess potential groundwater contamination. The results from these methods were consistent, effectively delineating the landfill boundaries and identifying possible contamination. The waste body was distinguished by its relatively low resistivity values with an average value of 1-10 Ω·m in the western and central parts of the landfill and 20-50 Ω·m at its eastern part in contrast with the surrounding high-resistivity gravelly sand layer (several hundreds of Ω·m), and a depth of up to 15 m. The variability in conductivity and magnetic susceptibility across different landfill sections indicated the heterogeneity of buried materials. Additionally, the ERT and TEM data indicate low resistivity values (below 5 Ω·m) at depths of 20-25 m. A correlation with the borehole data suggests that this may represent a contaminated coal/clay layer. Furthermore, repeated TEM measurements revealed significant variation in subsurface conductivity over time, highlighting the need for continuous monitoring. This study demonstrates the effectiveness of an integrated geophysical approach for providing a comprehensive understanding of subsurface landfill conditions, which is essential for informed environmental management and remediation.

Enhancing leachate management with antibacterial nanocomposites incorporating plant-based carbon dots and Satureja Khuzestanica essential oils

Landfill leachate, a complex mixture of pollutants, poses a significant environmental hazard. This study reports the synthesis and characterization of superabsorbent nanocomposites (SANs) designed for enhanced performance in waste management applications. SANs were prepared using carboxymethyl cellulose (CMC) and sodium polyacrylate (SPA) as the main components, carbon dots (CDs) to improve absorption, and Satureja Khuzestanica essential oil (SEO) for antibacterial performance. The results demonstrated that the addition of CDs significantly increased the absorption capacity and liquid retention of the samples, with a water absorption capacity reaching up to 8621 %. Furthermore, the samples exhibited high mechanical strength, with tensile strength improving by over 100 % in the presence of CDs. The inclusion of SEO provided strong antibacterial activity against Escherichia coli and Staphylococcus aureus, with inhibition zones measuring up to 26 mm. These SANs, with their high absorption capacity, mechanical robustness, and antibacterial properties, show great potential for improving waste management practices, particularly in leachate absorption strategies.

Nanotechnology in action: silver nanoparticles for improved eco-friendly remediation

Nanotechnology is an exciting area with great potential for use in biotechnology due to the far-reaching effects of nanoscale materials and their size-dependent characteristics. Silver and other metal nanoparticles have attracted a lot of attention lately because of the exceptional optical, electrical, and antimicrobial characteristics they possess. Silver nanoparticles (AgNPs) stand out due to their cost-effectiveness and abundant presence in the earth's crust, making them a compelling subject for further exploration. The vital efficacy of silver nanoparticles in addressing environmental concerns is emphasized in this thorough overview that dives into their significance in environmental remediation. Leveraging the distinctive properties of AgNPs, such as their antibacterial and catalytic characteristics, innovative solutions for efficient treatment of pollutants are being developed. The review critically examines the transformative potential of silver nanoparticles, exploring their various applications and promising achievements in enhancing environmental remediation techniques. As environmental defenders, this study advocates for intensified investigation and application of silver nanoparticles. Furthermore, this review aims to assist future investigators in developing more cost-effective and efficient innovations involving AgNPs carrying nanoprobes. These nanoprobes have the potential to detect numerous groups of contaminants simultaneously, with a low limit of detection (LOD) and reliable reproducibility. The goal is to utilize these innovations for environmental remediation purposes.

Cadmium neurotoxicity: Insights into behavioral effect and neurodegenerative diseases

Cadmium (Cd) induced neurotoxicity has become a growing concern due to its potential adverse effects on the Central Nervous System. Cd is a Heavy Metal (HM) that is released into the environment, through several industrial processes. It poses a risk to the health of the community by polluting air, water, and soil. Cd builds up in the brain and other neural tissues, raising concerns about its effect on the nervous system due to its prolonged biological half-life. Cd can enter into the neurons, hence increasing the production of Reactive Oxygen Species (ROS) in them and impairing their antioxidant defenses. Cd disrupts the Calcium (Ca2+) balance in neurons, affects the function of the mitochondria, and triggers cell death pathways. As a result of these pathways, the path to the development of many neurological diseases affected by environmental factors, especially Cd, such as Alzheimer's Disease (AD) and Amyotrophic Lateral Sclerosis (ALS) is facilitated. There are cognitive deficits associated with long exposure to Cd. Memory disorders are present in both animals and humans. Cd alters the brain's function and performance in critical periods. There are lifelong consequences of Cd exposure during critical brain development stages. The susceptibility to neurotoxic effects is increased by interactions with a variety of risk factors. Cd poses risks to neuronal function and behavior, potentially contributing to neurodegenerative diseases like Parkinson's disease (PD) and AD as well as cognitive issues. This article offers a comprehensive overview of Cd-induced neurotoxicity, encompassing risk assessment, adverse effect levels, and illuminating intricate pathways.

Toxic heavy metals in a landfill environment (Vientiane, Laos): Fish species and associated health risk assessment

Leachates from municipal landfills introduce toxic heavy metals into water, causing bioaccumulation. This study assesses metal levels and potential human health risks associated with consuming Anabas testudineus and Channa striata. Inductively coupled plasma mass spectrometry detected Cd, Cu, Cr, Ni, Pb, and Zn in both fish species. Leachate metal concentrations meet international discharge standards, Cd, Cr, and Pb in the fish exceed the international accepted values. Gastrointestinal tract+liver samples show significant variation between species, particularly in Cd and Pb. EDI, THQ/HI, and TR for the both species fall below TDIs, lower than the limit of 1, and within the acceptable range of the US-EPA permissible limit, respectively. Fish consumption appears safe regarding carcinogenic risk, but exceeding metal limits could impact heavy metals accumulation in the local food chain. Raising public awareness is crucial, and governmental agencies and environmental organizations should enhance waste treatment technologies and enact relevant health legislation.

Graphene Derived from Municipal Solid Waste

Landfilling is long the most common method of disposal for municipal solid waste (MSW). However, many countries seek to implement different methods of MSW treatment due to the high global warming potential associated with landfilling. Other methods such as recycling and incineration are either limited to only a fraction of generated MSW or still produce large greenhouse gas emissions, thereby providing an unsustainable disposal method. Here, the production of graphene from treated MSW is reported that including treated wood waste, using flash Joule heating. Results indicated a 71%-83% reduction in global warming potential compared to traditional disposal methods at a net cost of -$282 of MSW, presuming the graphene is sold at just 5% of its current market value to offset the cost of the flash Joule heating process.

Landfill leachate a potential challenge towards sustainable environmental management

The increasing amount of waste globally has led to a rise in the use of landfills, causing more pollutants to be released through landfill leachate. This leachate is a harmful mix formed from various types of waste at a specific site, and careful disposal is crucial to prevent harm to the environment. Understanding the physical and chemical properties, age differences, and types of landfills is essential to grasp how landfill leachate behaves in the environment. The use of Sustainable Development Goals (SDGs) in managing leachate is noticeable, as applying these goals directly is crucial in reducing the negative effects of landfill leachate. This detailed review explores the origin of landfill leachate, its characteristics, global classification by age, composition analysis, consequences of mismanagement, and the important role of SDGs in achieving sustainable landfill leachate management. The aim is to provide a perspective on the various aspects of landfill leachate, covering its origin, key features, global distribution, environmental impacts from poor management, and importance of SDGs which can guide for sustainable mitigation within a concise framework.

Potentially toxic elements (PTEs) and ecological risk at waste disposal sites: An analysis of sanitary landfills

This study presents an analysis of soil contamination caused by Ni, Zn, Cd, Cu, and Pb at municipal solid waste (MSW) landfills, with a focus on ecological risk assessment. The approach aims to assess how different landfill practices and environmental conditions affect soil contamination with potentially toxic elements (PTEs) and associated environmental risks. Soil samples were collected from MSW landfills in Poland and the Czech Republic. The research included a comprehensive assessment of PTEs in soils in the context of global environmental regulations. The degree of soil contamination by PTEs was assessed using indices: Geoaccumulation Index (Igeo), Single Pollution Index (Pi), Nemerow Pollution Index (PN), and Load Capacity of a Pollutant (PLI). The ecological risk was determined using the Risk of PTEs (ERi) and Sum of Individual Potential Risk Factors (ERI). The maximum values of the indicators observed for the Radiowo landfill were as follows: Igeo = 4.04 for Cd, Pi = 24.80 for Cd, PN = 18.22 for Cd, PLI = 2.66, ERi = 744 for Cd, ERI = 771.80. The maximum values of the indicators observed for the Zdounky landfill were as follows: Igeo = 1.04 for Cu, Pi = 3.10 for Cu, PN = 2.52 for Cu, PLI = 0.27, ERi = 25 for Cd, ERI = 41.86. The soils of the tested landfills were considered to be non-saline, with electrical conductivity (EC) values less than 2,000 μS/cm. Varying levels of PTEs were observed, and geostatistical analysis highlighted hotspots indicating pollution sources. Elevated concentrations of Cd in the soil indicated potential ecological risks. Concentrations of Cu and lead Pb were well below the thresholds set by the environmental legislation in several countries. In addition, Ni concentrations in the soils of both landfills indicated that the average levels were within acceptable limits. Principal Component Analysis (PCA) revealed common sources of PTEs. The identification of specific risk points at the Radiowo and Zdounky sites contributes to a better understanding of potential hazards in landfill environments. By establishing buffer zones and implementing regular maintenance programs, emerging environmental problems can be addressed in a timely manner.

Technological solutions to landfill management: Towards recovery of biomethane and carbon neutrality

Inadequate landfill management poses risks to the environment and human health, necessitating action. Poorly designed and operated landfills release harmful gases, contaminate water, and deplete resources. Aligning landfill management with the Sustainable Development Goals (SDGs) reveals its crucial role in achieving various targets. Urgent transformation of landfill practices is necessary to address challenges like climate change, carbon neutrality, food security, and resource recovery. The scientific community recognizes landfill management's impact on climate change, evidenced by in over 191 published articles (1998-2023). This article presents emerging solutions for sustainable landfill management, including physico-chemical, oxidation, and biological treatments. Each technology is evaluated for practical applications. The article emphasizes landfill management's global significance in pursuing carbon neutrality, prioritizing resource recovery over end-of-pipe treatments. It is important to note that minimizing water, chemical, and energy inputs in nutrient recovery is crucial for achieving carbon neutrality by 2050. Water reuse, energy recovery, and material selection during manufacturing are vital. The potential of water technologies for recovering macro-nutrients from landfill leachate is explored, considering feasibility factors. Integrated waste management approaches, such as recycling and composting, reduce waste and minimize environmental impact. It is conclusively evident that the water technologies not only facilitate the purification of leachate but also enable the recovery of valuable substances such as ammonium, heavy metals, nutrients, and salts. This recovery process holds economic benefits, while the conversion of CH4 and hydrogen into bioenergy and power generation through microbial fuel cells further enhances its potential. Future research should focus on sustainable and cost-effective treatment technologies for landfill leachate. Improving landfill management can mitigate the adverse environmental and health effects of inadequate waste disposal.

A review on recent environmental electrochemistry approaches for the consolidation of a circular economy model

Availability of raw materials in the chemical industry is related to the selection of the chemical processes in which they are used as well as to the efficiency, cost, and eventual evolution to more competitive dynamics of transformation technologies. In general terms however, any chemically transforming technology starts with the extraction, purification, design, manufacture, use, and disposal of materials. It is important to create a new paradigm towards green chemistry, sustainability, and circular economy in the chemical sciences that help to better employ, reuse, and recycle the materials used in every aspect of modern life. Electrochemistry is a growing field of knowledge that can help with these issues to reduce solid waste and the impact of chemical processes on the environment. Several electrochemical studies in the last decades have benefited the recovery of important chemical compounds and elements through electrodeposition, electrowinning, electrocoagulation, electrodialysis, and other processes. The use of living organisms and microorganisms using an electrochemical perspective (known as bioelectrochemistry), is also calling attention to "mining", through plants and microorganisms, essential chemical elements. New process design or the optimization of the current technologies is a major necessity to enhance production and minimize the use of raw materials along with less generation of wastes and secondary by-products. In this context, this contribution aims to show an up-to-date scenario of both environmental electrochemical and bioelectrochemical processes for the extraction, use, recovery and recycling of materials in a circular economy model.

Waste materials composited into an adsorbent for landfill leachate treatment

The ability of a composite adsorbent composed primarily of various waste materials to adsorb heavy metals, NH3-N, and chemical oxygen demand (COD) from landfill leachate was investigated through batch sorption experiments. The study determined the optimal contact time and adsorbent dosage for the removal of Pb, Zn, Cu, Fe, NH3-N, and COD to be 15, 90, 30, 180, 30, and 30 min, respectively. The corresponding optimum adsorbent dosages were determined to be 5, 30, 5, 15, 5, and 30 g, respectively. The composite adsorbent exhibited high removal efficiencies, achieving the following maximum values: 96.4% for Pb, 92.7% for Zn, 60.3% for Cu, 87.1% for Fe, 75.0% for NH3-N, and 67.5% for COD. Pb and Fe showed the best fit with a Langmuir isotherm model, with corresponding adsorption capacities of 0.0165 and 1.14 mg/g, respectively. For Zn, Cu, NH3-N, and COD, the equilibrium data demonstrated the best fit with an Elovich isotherm model, with adsorption capacities of 0.004, 0.005, 0.016, and 4.29 mg/g, respectively. The kinetic data followed the pseudo-second-order kinetic model. It presented a potential solution for the disposal of the waste from which it was derived.

Exploiting fungi in bioremediation for cleaning-up emerging pollutants in aquatic ecosystems

Aquatic pollution negatively affects water bodies, marine ecosystems, public health, and economy. Restoration of contaminated habitats has attracted global interest since protecting the health of marine ecosystems is crucial. Bioremediation is a cost-effective and eco-friendly way of transforming hazardous, resistant contaminants into environmentally benign products using diverse biological treatments. Because of their robust morphology and broad metabolic capabilities, fungi play an important role in bioremediation. This review summarizes the features employed by aquatic fungi for detoxification and subsequent bioremediation of different toxic and recalcitrant compounds in aquatic ecosystems. It also details how mycoremediation may convert chemically-suspended matters, microbial, nutritional, and oxygen-depleting aquatic contaminants into ecologically less hazardous products using multiple modes of action. Mycoremediation can also be considered in future research studies on aquatic, including marine, ecosystems as a possible tool for sustainable management, providing a foundation for selecting and utilizing fungi either independently or in microbial consortia.