Search Results (432)

Rapid urbanization in China has driven annual food waste production to 130 million tons, posing severe environmental challenges for anaerobic digestate management. To resolve trade-offs among drying efficiency, resource recovery (fertilizer/fuel), and carbon neutrality by optimizing the biodried product (BDP) recycling ratio (0–15%), six BDP treatments were tested in 60 L bioreactors. Metrics included drying kinetics, product properties, and environmental–economic trade-offs. The results showed that 12% BDP achieved a peak temperature integral (514.13 °C·d), an optimal biodrying index (3.67), and shortened the cycle to 12 days. Furthermore, 12% BDP yielded total nutrients (N + P₂O₅ + K₂O) of 4.19%, meeting the NY 525-2021 standard in China, while ≤3% BDP maximized fuel suitability with LHV > 5000 kJ·kg⁻¹, compliant with CEN/TC 343 RDF standards. BDP recycling reduced global warming potential by 27.3% and eliminated leachate generation, mitigating groundwater contamination risks. The RDF pathway (12% BDP) achieved the highest NPV (USD 716,725), whereas organic fertilizer required farmland subsidies (28.57/ton) to offset its low market value. A 12% BDP recycling ratio optimally balances technical feasibility, environmental safety, and economic returns, offering a closed-loop solution for global food waste valorization. Full article

The management of landfill leachate remains a persistent environmental issue for municipalities globally. Although dedicated treatment in engineered landfills mitigates environmental contamination, it is often cost-prohibitive. Co-treatment of landfill leachates in sewage treatment plants has been broadly studied, but there are a lot of issues associated with it. Sewage treatment plants apply physical, chemical, and biological processes, and the co-treatment of leachates—contaminated with metals, pesticides, emerging contaminants, and other toxic compounds—can impair the biological equilibrium of the system and compromise the quality of effluents and sludges. In the present research, the processes leading to the formation of landfill leachates and the processes that promote the removal of contaminants in sewage treatment plants were discussed. A theoretical, early screening level mixing model, incorporating removal rates and leachate concentrations from the literature, was employed to simulate effluent concentrations from a co-treatment process involving sequential decantation and an upflow anaerobic sludge blanket (UASB). Under a conservative worst-case scenario obtained from the literature, the model predicts that adsorption of contaminants onto the particulate phase enables removal of metals from the solution. However, considering the volumes of sludge involved, the predictions indicate that concentrations should be lower than naturally occurring in the sediments. It is proposed that continuous monitoring follow-up is a mandatory safeguard for any co-treatment operation. Full article

Per- and polyfluoroalkyl substances (PFAS) are a group of emerging organic contaminants receiving rising attention due to the threat they may pose to human health and their strong persistence in the environment, determined by their widespread use in the market as additives, reactants, or coverings. Since the most common end-of-life of products is landfill, countless case studies have confirmed the presence of PFAS in leachates. This work aims to evaluate and compare the environmental impacts of four different PFAS removal techniques from landfill leachate through a life cycle assessment performed on laboratory tests. Global warming, particulate matter formation, and human toxicity were examined and discussed in detail, since they represent most of the final single-score impact. The toxicity contribution of the residual PFAS in the matrix was investigated, resulting almost negligible. The results highlight activated carbon, sludge disposal, and sulfuric acid as major environmental hotspots for all categories. The clariflocculation followed by activated carbon adsorption results in the least impactful technique with promising PFAS removal efficiencies, between 44.3% and 82.2% depending on carbon dosage. Very precise correlations in the trends of the impact categories and the use of different functional units were also analysed. Full article

Landfill leachate reverse osmosis (RO) treatment generates a highly concentrated stream rich in recalcitrant organic matter, particularly humic substances (HS), which present potential for recovery and reuse as a biofertilizer. This study evaluated HS recovery from the RO concentrate of the Seropédica Landfill (Rio de Janeiro, Brazil) using a nanofiltration (NF) process with a polyethersulfone membrane (MWCO = 1000 Da) operated at 9 bar. The NF system achieved a volume reduction factor of 2.5, rejecting 70–75% of the organic matter. At the same time, salts were predominantly transmitted to the permeate. The phytotoxicity of recovered HS solution was evaluated through maize (Zea mays L.) germination assays at concentrations ranging from 20 to 100 mg HS/L. All treatments showed germination indices above 100%, indicating the absence of phytotoxicity, and seedling growth significantly improved relative to the control, especially at 20 mg HS/L. Trace metal concentrations in the recovered HS complied with Brazilian standards for irrigation water. Overall, the results show that nanofiltration is highly effective in concentrating humic substances from leachate RO concentrate, minimizing the presence of salts, and contributing to strategies for landfill leachate management. Full article

A major factor in worldwide ecological harm is the large quantity of municipal solid waste generated because of rapid industrialization and population growth. Nowadays, there are numerous mechanical, biological, and thermal waste treatment processes that can reduce the amount of landfilled waste. A variety of analytical tests are conducted to evaluate the potential risks that landfills pose to human health and the environment. Among these, laboratory leaching tests are commonly employed to assess the release of specific waste constituents that may become hazardous to the environment. Municipal solid waste (MSW) management poses significant environmental risks due to leachate contamination in bioreactor landfills, where acidic conditions (pH ≈ 5) can mobilize heavy metals. This study evaluates the reliability of leaching tests for biodried reject MSW from CWMC Marišćina, Croatia, by comparing standard EN 12457-1 and EN 12457-2 methods (L/S = 2 and 10 L/kg) with simulations of aerobic degradation using acetic acid (10 g/L) to maintain pH = 5 over 9 days. Waste composition analysis revealed plastics (35%), paper/cardboard (25%), metals (15%), and glass (10%) as dominant fractions. Although the majority of parameters determined through standard leaching tests remain below the maximum permissible limits for non-hazardous waste, simulations under acidic conditions demonstrated substantial increases in eluate concentrations between days 6 and 9: Hg (+1500%), As (+1322%), Pb (+1330%), Ni (+786%), and Cd (+267%), with TDS rising 33%. These results highlight the underestimation of risks by conventional tests, emphasizing the need for pH-dependent methods to predict in situ leachate behavior in MBO-treated waste and support improved EU landfill regulations for enhanced environmental protection. Full article

The study evaluates the long-term environmental performance of natural filtration dams for leachate treatment at a municipal solid waste landfill. Field measurements of a system operating for 24 years, equipped with natural clay-loam filtration barriers, provide empirical validation for assessing the effectiveness and durability of natural material-based treatment approaches. Hydrogeological studies, including well drilling, water sampling, and comprehensive chemical analysis, demonstrate that the cascade filtration system achieves pollutant removal efficiencies of 80–95% for major contaminants. Physical property measurements reveal progressive density reduction from 1005 to 994 kg/m³ and viscosity decreases from 1.048 to 1.011 cSt across the treatment system. Numerical simulations demonstrate that contaminant transport under actual site conditions remains diffusion-dominated over multi-decadal timescales, with aquifer concentrations remaining below 1% of source values after 50 years. Parametric studies reveal that density-driven convective fingering develops only at source concentrations exceeding 100 g/L. The findings validate the long-term viability of natural geological barriers combined with cascade filtration systems for cost-effective leachate treatment, demonstrating that preliminary treatment through natural filtration effectively suppresses gravitational instabilities and protects underlying aquifers. Full article

A leachate from alkaline leaching of copper shaft furnace (CSF) dust as a hazardous waste was used in this study for performing a chemical precipitation experiment of lead, zinc, and copper. The precipitation processes for lead, zinc, and copper were theoretically optimized based on a thermodynamic study. To determine suitable operating conditions, metal phase stability, reaction mechanisms, and precipitation order were analyzed using the Hydra/Medusa and HSC Chemistry v.10 software packages. In the first experimental stage, treatment of the alkaline leachate resulted in the formation of insoluble lead sulfate (PbSO₄), while zinc remained dissolved for subsequent recovery. In the second stage, the zinc-bearing solution was treated with Na₂CO₃, producing a mixed zinc precipitate consisting of Zn₅(OH)₆(CO₃)_2(s). This study determined that the optimal conditions for chemically precipitating lead as PbSO₄ from alkaline leachate (pH 13.5) are the use of 1 mol/L H₂SO₄ at pH 3.09 and Eh 0.22 V at 25 °C, while optimal zinc precipitation from this solution (pH 3.02) is achieved with 2 mol/L Na₂CO₃ at pH 9.39 and Eh –0.14 V at 25 °C. A small amount of copper present in the solution co-precipitated and was identified as an impurity in the zinc product. The chemical composition of the resulting precipitates was confirmed by SEM–EDX analysis. Full article

Water scarcity is an increasingly critical global issue, particularly in arid regions like Morocco. Innovative approaches, such as the use of alternative water sources like landfill leachate, offer promising solutions. In this study, phosphate washing sludge was used to treat landfill leachate with the aim of producing irrigation-quality water and recovering nitrogen from the resulting sediment. A total of 40 L of raw leachate was treated with three concentrations of phosphate washing sludge (25%, 37%, and 50%). This volume was processed at the laboratory scale as a proof of concept for potential larger-scale applications. After 24 to 36 h of mixing and agitation, the mixture underwent sedimentation, yielding clear supernatants and nitrogen-rich sludge pellets. These pellets showed a significant increase in organic matter content, from 6.4% to 13.5%, representing an enhancement of 110.9%, thus demonstrating partial leachate depollution and organic matter enrichment. Microbiological analyses revealed a 98.9% reduction in fecal streptococci. The supernatants met irrigation water standards in terms of pH and electrical conductivity, and phytotoxicity tests on maize seeds confirmed their suitability for irrigation. Additionally, the recovered nitrogen-rich sediment presents a valuable input for composting and soil amendment. Full article

Leachates from municipal organic waste contain high concentrations of ammonium and organic matter, making their treatment a top priority. The present study addressed leachate treatment under nitrification and focused on the diversity and abundance of comammox bacteria and their interaction with other canonical microorganisms. Batch reactors (1L) were fed with synthetic (100 mg HN₄⁺-N/L) or leachate ammonium and operated at 150 rpm, 3 mg DO/L, pH 7, and 30 °C. Reactor performance was evaluated using metabolic response variables and the microbial community by shotgun metagenomic sequencing. The results showed ammonium and organic matter (5200 mg COD/L) consumption efficiencies above 95%. The abundance and richness of the microbial community decreased in the presence of leachates. Sequences of the genus Nitrosomonas predominated with the synthetic medium, while the genus Nitrospira was the most abundant when fed with leachates. Archaea and anammox sequences were also detected. Comammox sequences of Candidatus Nitrospira inopinata, C. N. nitrificants, C. N. kreftii, C. N. neomarina, C. N. nitrosa, and C. N. allomarina were also detected, with the first species being predominant in the presence of leachates. These findings demonstrate that comammox and canonical microorganisms coexist during ammonium removal from leachates. Full article

Landfill leachate is highly concentrated wastewater containing non-biodegradable organic compounds and toxic substances. For this reason, advanced treatment methods are necessary for its treatment. The article discusses the possibility of treating leachate in a hybrid system combining ultrasonic pretreatment and anaerobic co-digestion with dairy wastewater in an anaerobic membrane bioreactor. Two laboratory-scale submerged anaerobic membrane reactors with a capillary module with membranes with a pore size of 0.1 μm and an effective filtration area of 0.35 m² were used in this study. An ultrasound disintegrator at 22 kHz (amplitude 14 µm) was used for leachate pretreatment. It was found that, as a result of leachate sonification (time > 10 min), the BOD₅/COD ratio in the wastewater increased from 0.1 to 0.4, and the content of dissolved organic compounds accounted for more than 40% of the total COD. Preliminary sonication of the leachate resulted in improved co-digestion efficiency in a reactor fed with conditioned leachate. A 92% reduction in organic pollutants was achieved, as well as a biogas production rate of 0.5 L biogas/g COD removed. Full article

The limited availability of high-quality ore deposits and the environmental hazards of metallurgical wastes highlight the importance of developing resource-efficient metal recovery technologies. Zinc kiln slag (ZKS), also known as Waelz slag, a by-product material enriched in non-ferrous metals, was processed through oxidative HCl leaching with H₂O₂ as an oxidant. Thermodynamic simulation and laboratory experiments were applied to determine optimal leaching conditions to dissolve copper, zinc, and iron. Optimal leaching efficiency was achieved with consumptions of 0.8 g HCl and 0.1 g H₂O₂ per gram of ZKS, a liquid-to-solid (L/S) ratio of 5 mL/g, a temperature of 70 °C, and a duration of 180 min, which resulted in recoveries of 96.3% Cu, 93.6% Fe, and 76.8% Zn. The solid residue with 43.5 wt.% C is promising for reuse as a reductant material in pyrometallurgical processes. Copper and arsenic were separated from the leachate via cementation with iron powder, achieving recovery rates of 98.9% and 91.2%, respectively. A subsequent two-step iron precipitation produced ferric hydroxide with 52.2 wt.% Fe and low levels of impurities. As a result, the developed novel hydrochloric acid oxidative leaching and metal precipitation route for ZKS recycling provides an efficient and sustainable alternative to conventional treatment methods. Full article

Leachate from the Magtaa Kheira landfill exhibits complex physicochemical characteristics that restrict the efficacy of single-treatment processes. This study assessed a sustainable two-stage treatment strategy combining coagulation–flocculation and adsorption. During the initial stage of the study, both aluminum sulfate (AS) and a bio-based coagulant derived from Moringa oleifera seeds (MOS) were evaluated for their effectiveness in the pretreatment of leachate. Box–Behnken Design combined with Response Surface Methodology was used to optimize the coagulation process using aluminum sulfate (AS). The highest removal efficiencies were 91% for turbidity and 85% for chemical oxygen demand (COD) removal, achieved at an AS concentration of 1.44 g·L⁻¹ and an initial pH of 8. In parallel, the performance of MOS extract was investigated as an eco-friendly alternative to AS. An FTIR analysis revealed the presence of protein-associated hydroxyl (3288 cm⁻¹) and carboxyl and amine groups (1647 cm⁻¹), which are integral to destabilization via hydrogen bonding, while SEM confirmed a surface morphology conducive to effective floc formation. MOS demonstrated comparable turbidity removal to AS, significantly reducing both sludge generation and chemical consumption. Following the coagulation stage, treated leachates were passed through a granular activated carbon (GAC) column, enhancing overall COD removal to over 94% to reach acceptable discharge and reuse levels. The coagulation–adsorption sequence, incorporating both chemical and bio-based coagulants, provides an efficient and sustainable approach for the treatment of complex leachate, addressing both performance and environmental considerations. Full article

Platinum’s unique properties, such as its high resistance to corrosion and high temperatures, are driving an increased use in modern technologies and advanced chemistry. However, the World Platinum Investment Council has projected, for the third consecutive year, a global deficit of platinum for 2025 and a negative forecast until 2029, highlighting the need for the development of new metallurgical methodologies to recover platinum but also to recycle product containing it. The use of alkaline amino acid (glycine) promises a highly selective and more environmentally friendly recovery methodology. Over the Platinum Group Metals, recovery studies have been performed only on palladium, but no published literature over platinum was found. This study investigated the feasibility of platinum adsorption from alkaline glycine solutions under various operational conditions using activated carbon. Results are demonstrating that platinum can be successfully recovered under the effects tested: 92.37–97.93% (carbon dosage), 70.00–95.72% (temperature), 94.08–97.39% (pH), 95.16–96.23% (platinum concentration), 95.72–96.53% (glycine concentration), and 95.72–97.12% (cyanide concentration). The scientific significance of this study lies in the confirmation for the potential use of a more environmentally friendly approach to recover platinum as opposed to the current cyanide and acidic chloride system. Full article

Landfill is a source of environmental concern as it may contaminate surface and groundwater, which could be a major source of potable water supply. Reverse osmosis (RO) membrane treatment is a well-known technique for treating leachate, but it requires high pressures of 80 bars or more to function. In addition, pretreatment, scaling, biofouling and concentrate disposal bring additional challenges to RO operation. The use of nanofiltration (NF) membranes with low rejection ensures the concentrate is separated into organic and salt solutions at a low pressure of 16–18 bars and ensures the concentrate volume is reduced to less than 3% of its initial value. This results in a reduction in energy consumption by a factor of least three compared to using conventional high-pressure RO, which reduces the initial leachate amount to 9–10%, and evaporation results in a subsequent reduction in concentrate volume to 3–4 per cent of the initial leachate volume. Due to the low osmotic pressure, the volume of an organic solution after separation can be reduced by three to four times compared to a saline solution of the same concentration. Full article

Plant Microbial Fuel Cells (PMFCs) represent a promising technology that uses electroactive bacteria to convert the chemical energy in organic matter into electrical energy. The addition of carbon pellet on electrodes may increase the specific surface area for colonization via bacteria. Use of nutrients such as urea could enhance plant growth. Our study aims to address the following questions: (1) Does carbon pellet layering affect the electrical performance of PMFCs? (2) Does urea treatment of the plants used to feed the PMFCs affect the electrical performance? A new prototype of PMFC has been tested: the plant pot is on the top, drainage water percolates to the tub below, containing the Microbial Fuel Cells (MFCs). To evaluate the best layering setup, two groups of MFCs were constructed: a “Double layer” group (with carbon pellet both on the cathode and on the anode), and a “Single layer” group (with graphite only on the cathode). All MFCs were plant-fed by Spathiphyllum lanceifolium L leachate. After one year, each of the previous two sets has been divided into two subsets: one wetted with percolate from plants fertilized with urea, and the other with percolate from unfertilized plants. Open circuit voltage (mV), short circuit peak current, and short circuit current after 5 s (mA) produced values that were measured on a weekly basis. PMFCs characterized by a “Single layer” group performed better than the “Double layer” group most times, in terms of higher and steadier values for voltage and calculated power. Undesirable results regarding urea treatment suggest the use of less concentrated urea solution. The treatment may provide consistency but appears to limit voltage and peak values, particularly in the “Double layer” configuration. Full article