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The technical feasibility of advanced oxidation process, in particular persulfate (PS) oxidation followed by struvite precipitation for landfill leachate treatment and nutrient recovery has been depicted in the current study. Furthermore, the impact of activation of PS with thermal and ultraviolet (UV) irradiation techniques on COD removal efficiency is also investigated. A maximum COD removal efficiency of 96% is accomplished at 65 °C together with supply of UV irradiation. The impact of persulfate dose, pH, and PS/65 °C/UV system on COD and biodegradability is also illustrated in the current study. Additionally, decomposition rate constant values are also ascertained in the present study. Afterwards, nutrient recovery using struvite precipitation is carried out for sustainable utilization of resources. Preliminary treatment of leachate with PS/65 °C/UV system is greatly conducive to recovering high quality struvite crystals. Besides, 94.9%, 83.5%, and 91.3% of PO43− - P, NH4+ - N, and Mg2+ recovery efficiency attained respectively at pH 9.5 and 1.2:1:1 molar ratio of Mg2+: NH4+ - N: PO43− - P. Additionally, all the nutrient recovery studies are validated using chemical equilibrium model Visual MINTEQ. Later, bioavailable fraction of PO43− - P in the recovered struvite is also investigated for utilization as fertilizer. The presence of Cu and Zn in the recovered struvite precipitate enhanced its economic value as a fertilizer. Since Cu and Zn are vital micronutrients for growth of plants. The low soluble values of recovered struvite precipitate confirmed its utilization as slow releasing fertilizer. [ABSTRACT FROM AUTHOR]

[Display omitted] • An integration of vehicle routing problem and life cycle assessment was adopted. • Derived leachate treatment contributes significantly to greenhouse gas emissions. • Centralized vehicle management decreases the greenhouse gas emissions. • Waste separation decreases greenhouse gas emissions significantly. • Vehicle electrification holds big potentials for greenhouse gas reduction. This study presents a comprehensive analysis of greenhouse gas (GHG) emissions associated with waste transfer and transport, incorporating derived leachate treatment—a factor often overlooked in existing research. Employing an integration model of life cycle assessment and a vehicle routing problem (VRP) methods, we evaluated the GHG reduction potential of waste transfer and transport system. Two Chinese counties with different topographies and demographics were selected, yielding 80 scenarios that factored in waste source separation as well as vehicle capacity, energy sources, and routes. The functional unit (FU) is transferring and transporting 1 tonne waste and treating derived leachate. The GHG emissions varied from 12 to 39 kg CO 2 equivalent per FU. Waste source separation emerged as the most impactful mitigation strategy, not only for the studied system but for an integrated waste management system. Followings are the use of larger capacity vehicles and electrification of the vehicles. These insights are instrumental for policymakers and stakeholders in optimizing waste management systems to reduce GHG emissions. [ABSTRACT FROM AUTHOR]

Improper disposal of municipal solid waste led to the release of heavy metals into the environment through leachate accumulation, causing a range of health and environmental problems. Phycoremediation, using microalgae to remove heavy metals from contaminated water, was investigated as a promising alternative to traditional remediation methods. This study explored the potential of Scenedesmus sp. as a phycoremediation agent for heavy metal removal from landfill leachate. The study was conducted in batch, continuous, and membrane bioreactor (MBR). In the batch system, Scenedesmus sp. was added to the leachate and incubated for 15 days before the biomass was separated from the suspension. In the continuous system, Scenedesmus sp. was cultured in a flow-through system, and the leachate was continuously fed into the system with flow rates measured at 120, 150, and 180 mL/h for 27 days. The MBR system was similar to the continuous system, but it incorporated a membrane filtration step to remove suspended solids from the treated water. The peristaltic pump was calibrated to operate at five different flow rates: 0.24 L/h, 0.30 L/h, 0.36 L/h, 0.42 L/h, and 0.48 L/h for the MBR system and ran for 24 h. The results showed that Scenedesmus sp. was effective in removing heavy metals such as lead (Pb), cobalt (Co), chromium (Cr), nickel (Ni), and zinc (Zn) from landfill leachate in all three systems. The highest removal efficiency was observed for Ni, with a removal of 0.083 mg/L in the MBR and 0.068 mg/L in batch mode. The lowest removal efficiency was observed for Zn, with a removal of 0.032 mg/L in the MBR, 0.027 mg/L in continuous mode, and 0.022 mg/L in batch mode. The findings depicted that the adsorption capacity varied among the studied metal ions, with the highest capacity observed for Ni (II) and the lowest for Zn (II), reflecting differences in metal speciation, surface charge interactions, and affinity for the adsorbent material. These factors influenced the adsorption process and resulted in varying adsorption capacities for different metal ions. The study also evaluated the biomass growth of Scenedesmus sp. and found that it was significantly influenced by the initial metal concentration in the leachate. The results of this study suggest that Scenedesmus sp. can be used as an effective phycoremediation agent for removing heavy metals from landfill leachate. [ABSTRACT FROM AUTHOR]

An important hidden source of soil heavy metal pollution was the discharge of wastewater and waste rock during mining production activities. Numerous processes could result in the buildup of heavy metals in soil, and exposure to these metals could irreversibly harm a person's health. The source, distribution and quantity of historical waste residue in a pyrite mining area were described, and the nature of the waste residue was determined based on the results of toxic leaching identification in this study. The study showed that the pH value of the leaching solution of the waste residues was less than 6. Therefore, these waste residues was the second category of general industrial solid waste. The soil around the waste residues was basically acidic. Also, the content of arsenic, cadmium and copper in farmland soil around the waste residues exceeded the screening value in the Soil Environmental Quality Standard Risk Control of Soil Pollution in Farmland (GB15618-2018). Therefore, the arsenic, cadmium and copper in the waste residue could migrate with rainwater and cause some pollution to the neighboring farmland soil. The surface water was acidic and the arsenic concentration in the surface water exceeded the standard limit. Therefore, surface water was affected by acidic wastewater. However, the impact of project wastewater on groundwater was not significant. Through the analysis of the pollution status, comprehensive treatment countermeasures and secondary pollution prevention measures for the waste residue were proposed, as well as the issues that need attention when formulating specific treatment plans, which could provide a reference for similar projects. [ABSTRACT FROM AUTHOR]

Background: Leachate, containing challenging-to-degrade organic substances and persistent toxins, poses significant environmental concerns. Advanced oxidation processes (AOPs) have emerged as a promising solution for effective leachate treatment. This research provides a comprehensive review of the impact of various AOPs in leachate treatment. Methods: This systematic review was conducted, encompassing commonly used AOPs such as ozone, peroxone, O3/catalyst, Fenton, photo-Fenton, UV/TiO2, photolytic persulfate, O3/UV, and O3/H2O2/ UV. Extensive searches were performed using reputable databases, including EBSCO, PubMed, Web of Science, and Google Scholar. Specific keywords and inclusion/exclusion criteria were applied. Data regarding leachate treatment parameters were meticulously summarized and analyzed using descriptive statistical methods. Results: The efficiency of AOPs in removing leachate organic matter varied, with chemical oxygen demand (COD) removal ranging from 41% to 83% in treatment systems. The order of effectiveness was found to be: O3/UV/H2O2 > photo-Fenton > UV/TiO2 > Fenton > persulfate (PS) > O3/UV > O3/H2O2 > O3/ catalyst > ozonation (O3). The highest COD removal efficiency of 83.75% was achieved using the O3/UV/ H2O2 AOP approach. The removal efficiency of color also varied, ranging from 32% to 100%, depending on the leachate’s characteristics, concentration, and specific treatment process utilized. Conclusion: AOPs, particularly the hybrid approach using O3/UV/H2O2, significantly enhance waste leachate treatment by effectively degrading persistent organic compounds through the generation of hydroxyl radicals. Further research is required to optimize AOPs and improve their efficiency in waste leachate treatment.

Microbial fuel cells (MFCs) are devices that use microorganisms to produce electricity from organic matter. In this study, the bacterium Delftia acidovorans spp was used to evaluate energy generation in a single-chamber MFC. In this evaluation, six MFCs were assembled with different exchange membranes: two with carbon fiber composite membrane, two with maghemite membrane and two with heat-treated maghemite. Synthetic maghemite was characterized using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR) measurements. Bioelectricity monitoring in the MFCs was conducted for 15 days, with data collected every 60 seconds. The cell that achieved the highest bioelectricity production was the one with heat-treated maghemite, reaching a production of 286.50mV. It used 100% leachate from fruit and vegetable waste as a substrate, starting with values of 365 mg/L of N-NH4, 96000 mg/L of biochemical oxygen demand (BOD5), 101500 mg/L of chemical oxygen demand (COD) and a pH of 4.11. In the results, the carbon fiber treatment had a higher removal efficiency percentage of up to 63.38% for BOD5 and 69.67% for COD. For ammonium nitrogen removal, all cells showed good removal efficiency of up to 92.49%. The pH value increased in all treatments due to the degradation of organic matter, reaching a value of up to 5.96. Thus, the efficiency of Delftia acidovorans spp. and carbon fiber are a good alternative as an exchange membrane in purifying leachate contaminants within an MFC.

In the past, due to improper sludge treatment technology and the absence of treatment standards, some municipal sludge was simply dewatered and then sent to landfills, occupying a significant amount of land and posing a serious threat of secondary pollution. To free up land in the landfill area for the expansion of a large-scale wastewater treatment plant (WWTP) in Shanghai, in this study, we conducted comprehensive pilot research on the entire chain of landfill sludge reprocessing and resource utilization. Both the combination of polyferric silicate sulfate (PFSS) and polyetheramine (PEA) and the combination of polyaluminum silicate (PAS) and polyetheramine (PEA) were used for sludge conditioning before dewatering, resulting in dewatered sludge with approximately 60% moisture content. The combined process involved coagulation and sedimentation, flocculation, and oxidation to treat the leachate generated during dewatering. The treatment process successfully met the specified water pollutant discharge concentration limits for the leachate, with the concentration of ammonia nitrogen in the effluent as low as 15.6 mg/L. Co-incineration in a power plant and modification were applied to stabilize and harmlessly dispose of the dewatered sludge. The coal-generating system ran stably, and no obvious problems were observed in the blending process. In the modification experiment, adding 5% to 7% of the solidifying agent increased the sludge bearing ratio by 53% and 57%, respectively. This process effectively reduced levels of fecal coliforms and heavy metals in the sludge but had a less noticeable effect on organic matter content. The modified sludge proved suitable for use as backfill material in construction areas without requirements for organic matter. The results of this study provide valuable insights for a completed full-scale landfill sludge reclamation and land resource release project. [ABSTRACT FROM AUTHOR]

BACKGROUND AND OBJECTIVES: Leachate recirculation has become a global practice for anaerobic digestion of municipal solid waste. Implementation of artificial neural networks for modeling and prediction of this process still remains challenging. Additionally, there has been a lack of research regarding the generalization capacity of neural networks using the data from other studies. This study aimed to enhance methane production rates and decrease biostabilization time in municipal solid waste treatment. It addressed the research gap in applying and generalizing neural networks to predict biogas production based on laboratorymeasured parameters. METHODS: Two distinct systems were utilized for leachate treatment. System 1 involved collecting the leachate delivered by a new municipal solid waste reactor and transferring it to a recirculation tank. System 2 consisted of passing the fresh municipal solid waste leachate through a degraded municipal solid waste and then returning the obtained liquid back to the waste reactor. The experimental data were employed to develop an artificial neural network to predict methane content and cumulative biogas production. The model was trained and optimized using the experimental data. The effectiveness and generalizability of the optimal neural network were evaluated by using it for the unseen data from other studies, ensuring its ability to make accurate predictions beyond the training dataset. FINDINGS: The results demonstrated that in System 1, ammonium and chemical oxygen demand concentrations in the leachate progressively increased to high levels. In System 2, the average removal efficiencies for chemical oxygen demand and ammonium were found to be 85 percent and 34 percent respectively. The methane yield in biogas reached 59 liters per kilogram of dry weight, with a corresponding methane fraction of 63 percent. The neural network model showed an excellent performance, with validation performances of 0.716 and 0.634. The overall performance of the dataset resulted in correlation coefficients of 0.9991 and 0.9975. Finally, high correlation coefficients of 0.88 and 0.82 were achieved by incorporating the test data from other studies. CONCLUSION: Leachate recirculation enhanced the reduction of chemical oxygen demand and the production of methane in bioreactors. Ammonium concentrations initially increased and later decreased due to waste adsorption and bacterial assimilation. The artificial neural network applied for predicting the cumulative methane production from municipal solid waste displayed a robust generalizability when tested on the data from other studies. The neural network was not significantly affected by changes in waste chemical properties, laboratory conditions, and recirculation rate. However, it showed a significant sensitivity to variation of waste mechanical properties. [ABSTRACT FROM AUTHOR]

Nitrous oxide (N2O) is an important greenhouse gas (GHG) and an ozone-depleting substance that can be emitted from landfills. Understanding the dynamics of N2O and its contribution to total emissions is critical to effective mitigation measures. This study outlines the dynamics of N2O in solid waste landfills and N2O emissions from them. N2O generation in anaerobic landfills is primarily due to denitrification and, to a lesser extent, nitrification, which occurs in the oxygenated cover soil layer and the working face. However, nitrification and denitrification are very limited within landfills. The landfill leachate contains high concentrations of ammonia (NH3). Thus, a significant amount of N2O is generated from aerobic processes during leachate treatment. Bioreactor landfills emit more N2O than traditional anaerobic landfills. The majority of N2O emitted from bioreactor landfills is generated through different pathways, such as hydroxylamine (NH2OH) oxidation, nitrifier denitrification, and heterotrophic denitrification. These processes are affected by several factors, including the carbon-to-nitrogen (C/N) ratio, NH3 oxidation rate NH3 oxidation rate, redox conditions, and temperature. Addressing N2O emissions from landfills will be necessary to achieve an integrated nitrogen management strategy that helps minimize N2O emissions. [ABSTRACT FROM AUTHOR]

Nature-based solutions (NBS) imitate natural processes and serve to generate multi-benefit values and services to the local communities. Sustainable solutions are multi-purpose measures implemented at the site, and offer communities targeted environmental water-related solutions in wastewater treatment, water retention, and pollution mitigation that result in a climate-resilient landscape. Numerous good cases combine NBS for environmental pollution mitigation, prevention, and management. They can be implemented and managed locally, and are stimulated as zero-emission and climate-resilient technology. The main areas of intervention where NBS is best applied are agricultural run-off mitigation (constructed ecosystems), wastewater and leachate treatment (constructed wetlands), revitalisation of standing water bodies (floating wetlands), stormwater retention measures (rain gardens), and nutrient reuse (sludge drying reed beds). A new report by the Sustainable sanitation Task Force (active in Global Water Partnership Central and Eastern Europe) on NBS in wastewater treatment indicates a moderate improvement in NBS application, but also relevant progress in engineering knowledge and innovation. It also estimates the application of several NBS treatment technologies for rural sanitation improvement and water reuse potentials.

BACKGROUND AND OBJECTIVES: Leachate recirculation has become a global practice for anaerobic digestion of municipal solid waste. Implementation of artificial neural networks for modeling and prediction of this process still remains challenging. Additionally, there has been a lack of research regarding the generalization capacity of neural networks using the data from other studies. This study aimed to enhance methane production rates and decrease biostabilization time in municipal solid waste treatment. It addressed the research gap in applying and generalizing neural networks to predict biogas production based on laboratory-measured parameters.METHODS: Two distinct systems were utilized for leachate treatment. System 1 involved collecting the leachate delivered by a new municipal solid waste reactor and transferring it to a recirculation tank. System 2 consisted of passing the fresh municipal solid waste leachate through a degraded municipal solid waste and then returning the obtained liquid back to the waste reactor. The experimental data were employed to develop an artificial neural network to predict methane content and cumulative biogas production. The model was trained and optimized using the experimental data. The effectiveness and generalizability of the optimal neural network were evaluated by using it for the unseen data from other studies, ensuring its ability to make accurate predictions beyond the training dataset.FINDINGS: The results demonstrated that in System 1, ammonium and chemical oxygen demand concentrations in the leachate progressively increased to high levels. In System 2, the average removal efficiencies for chemical oxygen demand and ammonium were found to be 85 percent and 34 percent respectively. The methane yield in biogas reached 59 liters per kilogram of dry weight, with a corresponding methane fraction of 63 percent. The neural network model showed an excellent performance, with validation performances of 0.716 and 0.634. The overall performance of the dataset resulted in correlation coefficients of 0.9991 and 0.9975. Finally, high correlation coefficients of 0.88 and 0.82 were achieved by incorporating the test data from other studies.CONCLUSION: Leachate recirculation enhanced the reduction of chemical oxygen demand and the production of methane in bioreactors. Ammonium concentrations initially increased and later decreased due to waste adsorption and bacterial assimilation. The artificial neural network applied for predicting the cumulative methane production from municipal solid waste displayed a robust generalizability when tested on the data from other studies. The neural network was not significantly affected by changes in waste chemical properties, laboratory conditions, and recirculation rate. However, it showed a significant sensitivity to variation of waste mechanical properties.

Microbial fuel cells (MFCs) are devices that use microorganisms to produce electricity from organic matter. In this study, the bacterium Delftia acidovorans spp was used to evaluate energy generation in a single-chamber MFC. In this evaluation, six MFCs were assembled with different exchange membranes: two with carbon fiber composite membrane, two with maghemite membrane and two with heat-treated maghemite. Synthetic maghemite was characterized using X-ray powder diffraction (XRD), X-ray photoelectron spectroscopy (XPS), Brunauer-Emmett-Teller (BET) and Fourier transform infrared spectroscopy (FTIR) measurements. Bioelectricity monitoring in the MFCs was conducted for 15 days, with data collected every 60 seconds. The cell that achieved the highest bioelectricity production was the one with heat-treated maghemite, reaching a production of 286.50mV. It used 100% leachate from fruit and vegetable waste as a substrate, starting with values of 365 mg/L of N-NH4, 96000 mg/L of biochemical oxygen demand (BOD5), 101500 mg/L of chemical oxygen demand (COD) and a pH of 4.11. In the results, the carbon fiber treatment had a higher removal efficiency percentage of up to 63.38% for BOD5 and 69.67% for COD. For ammonium nitrogen removal, all cells showed good removal efficiency of up to 92.49%. The pH value increased in all treatments due to the degradation of organic matter, reaching a value of up to 5.96. Thus, the efficiency of Delftia acidovorans spp. and carbon fiber are a good alternative as an exchange membrane in purifying leachate contaminants within an MFC. [ABSTRACT FROM AUTHOR]

Limited information is available in the literature regarding the energy consumption and the greenhouse gases emitted during landfill leachates treatment. A full-scale landfill leachates treatment system that included primary sedimentation, biological treatment in sequencing batch reactors, reverse osmosis and mechanical vapor recompression evaporation was monitored and evaluated for the removal of major pollutants, energy consumption and greenhouse gas emissions. Samples were taken during a period of two years from different points of the system, while the actual power consumption was calculated considering the available mechanical equipment and the hours of operation. The quantities of greenhouse gases emitted were estimated using appropriate equations and based on the operational characteristics of the system. According to chemical analyses, biological treatment resulted in partial removal of COD and total nitrogen, while the removal of BOD5 and NH4-N was significant, reaching 90 and 98%, respectively. Use of reverse osmosis increased the removal of all pollutants, satisfying the requirements of the legislation on wastewater discharge into the environment. Power consumption was calculated to be 35.3 KWhr per m3 of treated leachate, while mechanical vapor recompression evaporation was responsible for 60.5% of the total energy required. The contribution of other processes to energy consumption was as follows, in decreasing order: sequencing batch reactors > reverse osmosis > primary treatment. The roots blower vacuum pump used for mechanical vapor recompression evaporation, and the blowers providing air to the sequencing batch reactors, were the most energy-intensive pieces of apparatus, contributing 44.2% and 11.3% of the required energy, respectively. The quantity of greenhouse gases emitted was estimated to be 27.7 Kg CO2eq per m3 of treated leachates. Among the different processes used, biological treatment and mechanical vapor recompression evaporation contributed to 45.7% and 44.1% of the total emissions, respectively. The findings of this study reveal that an integrated landfill leachate treatment system that combines biological treatment and reverse osmosis can assure the protection of the aquatic environment by producing high-quality effluent; however, further research should be conducted regarding the sustainable management of reverse osmosis concentrate. Mechanical vapor recompression evaporation contributes significantly to the environmental footprint of the landfill leachates treatment system due to both high energy consumption and elevated emissions of greenhouse gases. [ABSTRACT FROM AUTHOR]

Nature-based solutions (NBS) imitate natural processes and serve to generate multi-benefit values and services to the local communities. Sustainable solutions are multi-purpose measures implemented at the site, and offer communities targeted environmental water-related solutions in wastewater treatment, water retention, and pollution mitigation that result in a climate- resilient landscape. Numerous good cases combine NBS for environmental pollution mitigation, prevention, and management. They can be implemented and managed locally, and are stimulated as zero-emission and climate-resilient technology. The main areas of intervention where NBS is best applied are agricultural run-off mitigation (constructed ecosystems), wastewater and leachate treatment (constructed wetlands), revitalisation of standing water bodies (floating wetlands), stormwater retention measures (rain gardens), and nutrient reuse (sludge drying reed beds). A new report by the Sustainable sanitation Task Force (active in Global Water Partnership Central and Eastern Europe) on NBS in wastewater treatment indicates a moderate improvement in NBS application, but also relevant progress in engineering knowledge and innovation. It also estimates the application of several NBS treatment technologies for rural sanitation improvement and water reuse potentials. [ABSTRACT FROM AUTHOR]

The aim of this study was to investigate the simultaneous biogas generation and leachate treatment using municipal waste and its polluted leachate at Mashhad landfill in northeast Iran. The research focused on examining the kinetic model of CH4, CO2, CO, H2S and O2 production with and without leachate recirculation (LR) through control/test wells. The findings from both wells showed an increase in logarithmic CH4 production rate, with the coefficient related to the rate of increase in methane concentration ranging from 0/52-0/64 in the control well and 0/47-0/55 in the test well, respectively. Under LR conditions, it was observed that the CH4 production rate was slower, taking an average of 120 minutes to reach 50% concentration, compared to just 15 minutes without LR. Using first-order equations, the CH4 production coefficients were measured to be 2/17 h−1 and 0/9 h−1 for the control and test wells, respectively. The analysis of recirculated leachate revealed a significant decrease (∼30%) in the total volume of leachate with 72% COD removal, which could help manage overloaded leachate problems in the landfill. The COD removal coefficient was found to be 0/036 day−1 in the control well, whereas the test well with leachate recirculation showed a more rapid decrease from 50 g.l−1 to about 14 g.l−1 with a removal coefficient of 0/012 day−1, three times higher than the control well. Additionally, nitrogen content analysis indicated that although the amount of ammonia content increased with LR, the increase was relatively low in comparison to conditions without LR, equivalent to 1394 ppm and 1000 ppm in control and test wells, respectively. This study aligns with the water-energy-nexus concept by offering a sustainable solution for waste management and energy generation, while also addressing water management challenges associated with landfill operations.

Leachates from landfills are highly polluted with a considerable content of organic and inorganic pollutants which pose severe deterioration to environment including soil, groundwater, surface water and air. Several mitigative measures have been applied for effective management of leachate such as biological treatment, engineering device control leachate migration, physical/chemical treatment, and membrane technology. Among the alternatives, anaerobic digestion (AD) is promising, with effective removal of pollutants and high potential for renewable energy production and nutrient recovery. Landfill leachate (LFL) is an excellent source as a substrate in an AD system, with its high content of organic matters. The advantages and disadvantages of AD of LFL were extensively discussed in this review in terms of its potential as a co-substrate, pre-treatment application, and the types and design parameters of the digester. The review critically evaluated the previous studies on leachate treatment using an AD system as well as potential factors which can enhance the treatment efficiency, including the application of an integrated system, additive substances as well as potential inhibition factors. Pre-treatment methods have the potential to meet desired effluent quality of LFL before discharging into receiving bodies. The review also highlighted the application of kinetic modelling and machine learning practices, along with the potential of energy generation in AD of LFL. Additionally, the review explored the various strategies, and recent advances in the anaerobic treatment of LFL, which suggested that there is a requirement to further improve the system, configuration and functioning as a precursor in selecting suitable integrated LFL-treatment technology. [ABSTRACT FROM AUTHOR]

In the past, due to improper sludge treatment technology and the absence of treatment standards, some municipal sludge was simply dewatered and then sent to landfills, occupying a significant amount of land and posing a serious threat of secondary pollution. To free up land in the landfill area for the expansion of a large-scale wastewater treatment plant (WWTP) in Shanghai, in this study, we conducted comprehensive pilot research on the entire chain of landfill sludge reprocessing and resource utilization. Both the combination of polyferric silicate sulfate (PFSS) and polyetheramine (PEA) and the combination of polyaluminum silicate (PAS) and polyetheramine (PEA) were used for sludge conditioning before dewatering, resulting in dewatered sludge with approximately 60% moisture content. The combined process involved coagulation and sedimentation, flocculation, and oxidation to treat the leachate generated during dewatering. The treatment process successfully met the specified water pollutant discharge concentration limits for the leachate, with the concentration of ammonia nitrogen in the effluent as low as 15.6 mg/L. Co-incineration in a power plant and modification were applied to stabilize and harmlessly dispose of the dewatered sludge. The coal-generating system ran stably, and no obvious problems were observed in the blending process. In the modification experiment, adding 5% to 7% of the solidifying agent increased the sludge bearing ratio by 53% and 57%, respectively. This process effectively reduced levels of fecal coliforms and heavy metals in the sludge but had a less noticeable effect on organic matter content. The modified sludge proved suitable for use as backfill material in construction areas without requirements for organic matter. The results of this study provide valuable insights for a completed full-scale landfill sludge reclamation and land resource release project.

Natural material, agricultural waste, and industrial waste are locally accessible resources that are utilized as environment-friendly and inexpensive sorbent. The natural abundance source like green waste mussel shell (GWMS) adsorbent makes them an advantageous basic sorbent material to produce inexpensive water treatment adsorbent. This study addresses the evaluation of GWMS as an efficient sorbent material to minimize the utilization of traditional adsorbents namely activated carbon (AC) and zeolite (ZEO) for removing pollutants from leachate. COD and ammoniacal nitrogen (NH3–N) were identified as the two problematic parameters in landfill leachate. Batch adsorption experiments were performed with 100 mL of prepared leachate solution in 2.5 g, 7.5 g, and 12.5 g dosages. The leachate solution was shaken in an incubator for 2 h at 200 rpm shaking speed and pH 7. The GWMS dosage at 7.5 g illustrated that the removal percentage of COD is 71% and that of NH3–N is 47%. The adsorption capacity related to the complete monolayer coverage of saturated molecules shows that the maximum adsorption capacity of COD is 47.39 mg g−1 and that of NH3–N is 26.18 mg g−1. Langmuir and Freundlich values are better described by Langmuir than Freundlich based on R2 values for COD > NH3–N where 0.9941 > 0.9891. The R2 values for COD > NH3–N for the linear plot of the pseudo-second-order were 0.9997 > 0.9763, respectively. [ABSTRACT FROM AUTHOR]

Abstract The resource recovery of heavy metals from effluent has significant environmental implications and potential commercial value. Chromium phosphide nanoparticles embedded in a nitrogen‐/phosphorus‐doped porous carbon matrix (CrP/NPC) are synthesized via a consecutive Cr6+ leachate treatment and resource recovery process. Electrochemical testing shows that CrP/NPC shows excellent nitrogen reduction reaction (NRR) performance, which yields the highest NH3 production rate of 22.56 μg h−1 mg−1cat. and Faradaic efficiency (16.37%) at −0.5 V versus the reversible hydrogen electrode in a 0.05 M Na2SO4 aqueous solution, as well as robust catalytic stability. The isotopic experiments using 15N2 as a nitrogen source confirm that the detected NH3 is derived from the NRR process. Finally, density functional theory (DFT) calculations show that the electron deficiency environment of the Cr site can significantly reduce the barrier of the NRR process and promote the formation of intermediate species.

The leachate produced in landfills represents one of the main environmental risks. Among the main emerging techniques of leachate treatment is evaporation. The present study aimed to implement and monitor the performance of natural and forced evaporation technology in open and closed systems. The open pilot experiment system consisted of storage tanks, sprinklers and an evaporative panel, obtaining an average evaporation rate in the system of over 100 L.day−1. For the closed pilot system, different temperatures were combined with different air speeds, simulated by a fan. The results obtained during this operation ranged from 7.7 to 127.2 L.day−1 for the various climatic conditions simulated. In both experiments, wind speed proved to be the most significant climatic characteristic, followed by temperature. With regard to the dispersion of microorganisms in the air, both pilots showed a downward trend in colony-forming units (CFUs) as the distance increased. The volatile organic compound (VOCs) most likely to be present in the atmosphere surrounding the experiments were Dimethyl-Diazene, Tetramethyl-Silane, 2-Nitro-Propane, and 3-Methyl-Butanenitrile. The performance of leachate evaporation, which can be applied in various climatic conditions, leads to the conclusion that these techniques are a viable alternative to conventional landfill leachate treatment methods. • In the open pilot, the daily evaporation volume was approximately 26 L.m−2. • The best evaporation efficiency of the closed pilot was 353.3 L.m−2.day−1. • The most significant climatic characteristic for the evaporation was wind speed. • The number of microorganisms is inversely proportional to the pilot's distance. • Dimethyldiazene, 2-Nitropropane and 3-Methylbutanenitrile were VOCs detected in air. [ABSTRACT FROM AUTHOR]

Limited information is available in the literature regarding the energy consumption and the greenhouse gases emitted during landfill leachates treatment. A full-scale landfill leachates treatment system that included primary sedimentation, biological treatment in sequencing batch reactors, reverse osmosis and mechanical vapor recompression evaporation was monitored and evaluated for the removal of major pollutants, energy consumption and greenhouse gas emissions. Samples were taken during a period of two years from different points of the system, while the actual power consumption was calculated considering the available mechanical equipment and the hours of operation. The quantities of greenhouse gases emitted were estimated using appropriate equations and based on the operational characteristics of the system. According to chemical analyses, biological treatment resulted in partial removal of COD and total nitrogen, while the removal of BOD5 and NH4-N was significant, reaching 90 and 98%, respectively. Use of reverse osmosis increased the removal of all pollutants, satisfying the requirements of the legislation on wastewater discharge into the environment. Power consumption was calculated to be 35.3 KWhr per m3 of treated leachate, while mechanical vapor recompression evaporation was responsible for 60.5% of the total energy required. The contribution of other processes to energy consumption was as follows, in decreasing order: sequencing batch reactors > reverse osmosis > primary treatment. The roots blower vacuum pump used for mechanical vapor recompression evaporation, and the blowers providing air to the sequencing batch reactors, were the most energy-intensive pieces of apparatus, contributing 44.2% and 11.3% of the required energy, respectively. The quantity of greenhouse gases emitted was estimated to be 27.7 Kg CO2eq per m3 of treated leachates. Among the different processes used, biological treatment and mechanical vapor recompression evaporation contributed to 45.7% and 44.1% of the total emissions, respectively. The findings of this study reveal that an integrated landfill leachate treatment system that combines biological treatment and reverse osmosis can assure the protection of the aquatic environment by producing high-quality effluent; however, further research should be conducted regarding the sustainable management of reverse osmosis concentrate. Mechanical vapor recompression evaporation contributes significantly to the environmental footprint of the landfill leachates treatment system due to both high energy consumption and elevated emissions of greenhouse gases.

• PFAS concentration was evaluated for 15 on-site leachate treatment facilities. • PFAA-precursors convert into PFAAs in the treated effluent. • PFAS concentration and species distribution fluctuate at the surface amid aeration. • RO systems reduce over 95 % of PFAS concentration in the permeate. • The interpretation of TOP assay for leachate is subject to limitations. Many consumer and industrial products, industrial wastes and dewatered sludge from municipal wastewater treatment plants containing per- and polyfluoroalkyl substances (PFAS) are disposed of in landfills at the end of their usage, with PFAS in these products leached into landfill leachates. On-site leachate treatment is one possible method to reduce PFAS in leachates. Many landfills are equipped with on-site leachate treatment systems, but few full-scale facilities have been systematically evaluated for PFAS concentration changes. The objective of this study was to evaluate a cross-section of full-scale on-site landfill treatment systems to measure changes in PFAS concentrations. Leachate samples were collected before and after treatment from 15 facilities and were evaluated for 26 PFAS, including 11 perfluoroalkyl carboxylic acids (PFCAs), 7 perfluoroalkyl sulfonic acids (PFSAs), and 8 perfluoroalkyl acid precursors (PFAA-precursors). Transformation of precursors was evaluated by the total oxidizable precursor (TOP) assay. Results showed no obvious reductions in total measured PFAS (∑ 26 PFAS) for on-site treatment systems including ponds, aeration tanks, powdered activated carbon (PAC), and sand filtration. Among evaluated on-site treatment systems, only systems fitted with reverse osmosis (RO) showed significant reductions (98–99 %) of ∑ 26 PFAS in the permeate. Results from the TOP assay showed that untargeted PFAA-precursors converted into targeted short-chain PFCAs increasing ∑ 26 PFAS in oxidized samples by 30 %, on average. Overall, results of this study confirm the efficacy of RO systems and suggest the presence of additional precursors beyond those measured in this study. [ABSTRACT FROM AUTHOR]

[Display omitted] • Fifteen landfill facilities, with on-site treatment systems in Florida, were evaluated. • Changes between influent and effluent (Δ) were analyzed. • Δ conductivity, pH, alkalinity, and ammonia were associated with Δ PFAS. • Δ PFAS were associated with Δ Ba, Co, Ca, Fe, Mg and Zn. • Associations may be due to effects from dilution and chemical precipitation. Per- and polyfluoroalkyl substances (PFAS) have been found at relatively elevated concentrations in landfill leachates. Some landfill facilities treat physical-chemical parameters of their leachates using on-site leachate treatment systems before discharge. The objective of this study was to evaluate whether changes in physical-chemical parameters of leachate at on-site treatment systems (including bulk measurements, oxygen demanding components, and metals) were associated with concentration changes in PFAS. Leachates were evaluated at 15 on-site treatment facilities which included pond systems, aeration tanks, powdered activated carbon (PAC), sand filtration, reverse osmosis (RO) and combination treatment processes. Results show that most physical-chemical parameters and PFAS were significantly reduced in RO systems (over 90 %). For pond systems, statistically significant correlations (r s > 0.6, p < 0.05) were observed between ∑ 26 PFAS changes and the changes in pH, alkalinity, ammonia, and some metals. Significant correlations were also found between ∑ 8 PFAAs precursors changes and specific conductivity (SPC), pH, alkalinity, ammonia, and metals changes. For aeration tank systems, significant correlations (r s > 0.6, p < 0.05) were observed between ∑ 26 PFAS changes and changes in total dissolved solids and zinc, and between the changes of ∑ 8 PFAAs precursors and field pH. These correlations are believed to be associated with rainfall dilution and precipitation of calcium carbonate and other metals as leachate is introduced to the atmosphere. [ABSTRACT FROM AUTHOR]

Highly active Ti/Sb–SnO2 electrodes were fabricated using sol-gel spin coating procedure, which exhibited a rough, uniform and multilayer coating structure. The effects of different Sb-SnO2 film layers on the physiochemical, electrochemical properties and pollutant degradability of electrodes and the mechanism were evaluated on a systematic basis. The electrodes with more active layers exhibited higher electro-catalytic performance. Upon exceeding 8 layers, the promotion effect of the coating was reduced. Considering various factors, this paper recommends preparing Ti/Sb–SnO2 electrodes coated with 8 layers to obtain higher electro-catalytic ability in landfill leachate treatment. The specific number of coating layers should be determined according to the electrode requirements. This work provided a theoretical basis and technical support for the preparation of Ti-SnO2 electrodes with high electro-catalytic activity and stability, while it still remains a great challenge to achieve an excellent balance between performance and stability before Ti/Sb-SnO2 electrodes can be implemented on a large scale in wastewater treatment. HIGHLIGHTS Sol-gel spin coating method could be used to exhibit a multilayer coating structure.; Electrodes with more active layers had higher electro-catalytic performance.; Upon exceeding 8 layers, the promotion effect of the coating was reduced.; Ti/Sb-SnO2 electrodes coated with 8 layers could obtain higher electro-catalytic ability during leachate treatment.;

The generation of leachate is one of the main problems of municipal solid waste disposal, which can lead to a severe threat to surface and groundwater. In this research, landfill leachate was treated through modifiying bentonite with HDTMA-Br (Hexadecyltrimethylammonium bromide). The effects of surfactant intercalating quantity, pH, contact time, and adsorbent dose was investigated in a batch experiment. Raw and modified clay was also characterized using different techniques including Fourier transformation infrared spectroscopy (FTIR), X-ray diffractometry (XRD), scanning electron microscopy (FE-SEM), Brunauer-Emmett-Teller (BET), and Thermogravimetric analysis (TGA). The optimization experiment revealed that 50 min of equilibration, 50g L-1 of dosage and pH= 3, for the clay loaded with a capacity of 1.0 CEC (cation exchange capacity), were the optimum condition for COD removal of landfill leachate. The maximum turbidity reduction rate was 92.1%, at a pH of 11, absorbent dosage of 40 g L-1, and the contact time of 30 min. The findings of this research showed that this modified clay could be used as an affordable adsorbent for reducing COD and turbidity from landfill leachate. [ABSTRACT FROM AUTHOR]

The physical appearance of leachate when it emerges from a typical landfill site is a strongly odoured black, yellow or orange colored cloudy liquid which contains organic and inorganic pollutants which makes it unsatisfactory to be released in water bodies without any prior treatment. The goal of current study was to examine the effectiveness of waste green mussel shell (WGMS) for the removal of pollutants from stabilized leachate. Chemical oxygen demand (COD) and ammonium nitrogen (NH3-N) was investigated as the two major contaminants in leachate. In this study, adsorption method employed for the treatment of landfill leachate. Static batch experiment was carried out with 100 mL leachate sample with pH 7, contact time 120 min, dosage 4.0 g with 200 rpm shaking speed. The best removal was achieved at 2.0 g with the removal percentage of COD and N-NH3 were 58% and 48%, respectively. Langmuir isotherm adsorption model showed best fitted with coefficient of determination for COD with the value of R² = 0.9944 and NH3-N with the value of R² = 0.9918 respectively as compared to Freundlich model shows the value for COD with the value of R² = 0.9825 and NH3-N with the value of R² = 0.9508. Thus, it indicates adsorbent adsorption occurs monolayer adsorption on homogeneous surface. The WGMS provides a significantly lower cost medium for reduction of COD and NH3-N. [ABSTRACT FROM AUTHOR]

This work proposes a suitable treatment for the leachates from a sewage sludge composting process using a specific windrow (biopile). The biopile's evolution and organic content degradation were followed for 2 months with regular leachate spraying to assess the physico-chemical and biological impacts, and determine the risk of enrichment with certain monitored pollutants. The final objective was the valorization of the biopile substrates in the composting process, while respecting the quality standards of use in a circular economy way. Classical physico-chemical parameters (pH, conductivity, dissolved organic carbon (DOC), total dissolved nitrogen (TDN), etc.) were measured in the leachates and in the water-extractable and dry-solid fractions of the biopile, and the catabolic evolution of the micro-organisms (diversity and activities), as well as the enrichment with persistent organic pollutants (POPs) (prioritized PAHs (polycyclic aromatic hydrocarbons) and PCBs (polychlorinated biphenyls)), were determined. The results showed that the microbial populations that were already present in the biopile, and that are responsible for biodegradation, were not affected by leachate spraying. Even when the studied compost leachate was highly concentrated with ammonium nitrogen (10.4 gN L−1 on average), it significantly decreased in the biopile after 2 weeks. A study on the evolution of the isotopic signature (δ15 N) confirmed the loss of leachate nitrogen in its ammoniacal form. The bio-physico-chemical characteristics of the biopile at the end of the experiment were similar to those before the first spraying with leachate. Moreover, no significant enrichment with contaminants (metal trace elements, volatile fatty acids, or persistent organic pollutants) was observed. The results show that it would be possible for composting platforms to implement this inexpensive and sustainable process for the treatment of leachates. [ABSTRACT FROM AUTHOR]

A large amount of fruit and vegetable waste is generated every day in big cities. The efficient disposal of such biodegradable waste can be considered a challenge. Leachate contains large amounts of pollutants, and treating it is very complex, expensive, and requires a variety of hybrid processes. This study used the Analytic Hierarchy Process (AHP) to analyze suitable treatment methods for the leachate from fruit and leek fields. Quantitative and qualitative parameters or a combination of these parameters were used as defined in Expert Choice software. The criteria used for this purpose included chemical oxygen demand (COD), biochemical oxygen demand (BOD), COD/BOD, temperature, TOC, pH, total dissolved solids (TDS), total suspended solids (TSS), and time. These criteria, which are important for leachate classification, were identified and extracted by experts; their importance was ranked by AHP software. The research process was divided into two parts to ascertain a faster method: the significance of the parameter time and the insignificance of the parameter time. Biological treatment methods outperformed the other methods where the parameter time was insignificant. In the cases where the parameter time was significant, chemical methods and, in particular, two methods with ozone compounds (Ozone + GAC, Ozone + H2O2) outperformed the other methods.

In the present study, the integration of the electrochemical process with a membrane bioreactor was used as a new technology for leachate treatment. In the electro-membrane bioreactor (EMBR), aluminum electrodes were used as anodes and cathodes. The EMBR was operated at a current density of 0.5 mA/cm2 and a solids retention time of 90 days to remove common contaminants such as ammonia-nitrogen (NH3-N), chemical oxygen demand (COD), phosphate (PO43--P), and ultraviolet absorbance at 254 nm (UV254). The maximum removal efficiencies of COD and NH3-N were above 98%. The average removal efficiency of PO43--P by the EMBR system was 93%, which was significant compared to previous studies. The removal rate of humic substances based on UV254 was provided at approximately 96.95%. The trans-membrane pressure rate was acceptable for 80 days in the EMBR, which could be related to sludge size improvement and filtration resistance through the occurrence of electrocoagulation, electrophoresis, and electroosmosis mechanisms. The mean removal efficiencies in the EMBR were 90, 91.25, 96, and 87.5 % for chromium (Cr), cadmium (Cd), zinc (Zn), and iron (Fe), respectively. The slight change of mixed liquor-suspended solids (MLSS) in the leachate treatment reactor showed that the microorganisms in the new EMBR system had high adaptation. Based on the results, the EMBR is a promising technology to improve leachate treatment performance due to its excellent removal efficiency of common contaminants, metal removal, and reducing fouling.

The leachate produced by waste transfer stations (WTSs) contains substantial amounts of refractory organic matter and ammonia, necessitating on-site treatment. In this study, a novel electrocatalytic oxidation (ECO) process with Fe-DSA dual anode configuration was established for leachate pretreatment. In this configuration, chloride in the leachate was converted to active chlorine by the DSA anode, while ferric hydroxide (Fe(OH) 3) was produced from Fe anode. As a result, Fe (VI) was in situ formed through the reactions between active chlorine and Fe(OH) 3. Simultaneous and efficient removal of COD and NH 4 +-N in the ECO process with Fe-DSA dual anode configuration was achieved, significantly improving leachate biodegradability compared with the Fe–Fe and DSA-DSA dual anode configurations. The transformation characteristics of organic compounds in the ECO process were investigated through the electrospray ionization Fourier transform ion cyclotron resonance mass spectrometry (ESI FT-ICR MS) analysis. The ECO process with Fe-DSA dual anode configuration promoted the removal and transformation of lignins/carboxylic rich alicyclic molecules (CRAM)-like and tannins compounds with biologically refractory properties, as well as S-containing compounds with biological toxicity. Further X-ray photoelectron spectroscopy (XPS) analysis revealed that iron oxides, amorphous Fe-(oxy) hydroxide, and amorphous Fe(OH) 3 produced by Fe (VI) decomposition in the ECO process with Fe-DSA dual anode configuration enhanced removal performance through coagulation. In addition, the contribution of different active species to organic matter removal in the ECO process was quantified by quenching experiments. High-valent iron oxidation dominated the ECO process with Fe-DSA dual anode configuration, while active chlorine oxidation, •OH oxidation and coagulation synergistically contributed to organic matter removal. [Display omitted] • The ECO process with Fe-DSA dual anodes can achieve in situ ferrate generation. • About 50% COD and 40% ammonia can be removed simultaneously from leachate. • More ferrate was formed with Fe-DSA dual anodes than Fe–Fe or DSA-DSA dual anodes. • Refractory lignins/CRAM-like, tannins and S-containing organic removal was achieved. • High-valent iron oxidation was crucial for organic removal with Fe-DSA dual anodes. [ABSTRACT FROM AUTHOR]

Leachates from landfills are highly polluted with a considerable content of organic and inorganic pollutants which pose severe deterioration to environment including soil, groundwater, surface water and air. Several mitigative measures have been applied for effective management of leachate such as biological treatment, engineering device control leachate migration, physical/chemical treatment, and membrane technology. Among the alternatives, anaerobic digestion (AD) is promising, with effective removal of pollutants and high potential for renewable energy production and nutrient recovery. Landfill leachate (LFL) is an excellent source as a substrate in an AD system, with its high content of organic matters. The advantages and disadvantages of AD of LFL were extensively discussed in this review in terms of its potential as a co-substrate, pre-treatment application, and the types and design parameters of the digester. The review critically evaluated the previous studies on leachate treatment using an AD system as well as potential factors which can enhance the treatment efficiency, including the application of an integrated system, additive substances as well as potential inhibition factors. Pre-treatment methods have the potential to meet desired effluent quality of LFL before discharging into receiving bodies. The review also highlighted the application of kinetic modelling and machine learning practices, along with the potential of energy generation in AD of LFL. Additionally, the review explored the various strategies, and recent advances in the anaerobic treatment of LFL, which suggested that there is a requirement to further improve the system, configuration and functioning as a precursor in selecting suitable integrated LFL-treatment technology.

Open dumping of Municipal Solid Waste (MSW) results in generation of leachate that contains large amounts of organic matter, ammonia, heavy metals, chlorinated organics, phenolic compounds, phthalates, and pesticide residues which irreparably contaminate both surface and groundwater. Advanced Oxidation Processes (AOP) have been reported as one of the effective treatment methods, especially in improving the biodegradability of the leachate as well as effective in removing recalcitrant organics. With AOP pre-treatment rendered the leachate becomes more amenable to further treatment using biological treatment, adsorption, or ion-exchange processes. The study reported in this paper mainly aims at assessing the suitability of ozone and peroxone (O3+H2O2) based advanced oxidation processes (AOP) for the treatment of MSW leachate from the open dumpsite. The effect of reaction time, impact of O3 dose, and H2O2 concentration on the efficiency of COD removal, improvement in the biodegradability of the leachate, and pH change were determined as the performance parameters for the treatment process. The maximum COD removal efficiency was found to be 46% and 82% with ozone alone (3975 mg/L) and with ozone (9275 mg/L) + 50 mg/L H2O2 each with 120 min. reaction time. It is also found that the BOD5/COD ratio has been increased from 0.09 to 0.58 at optimum O3 + 50 mg/L H2O2 treatment would offer as an effective method for increasing the biodegradability. [ABSTRACT FROM AUTHOR]

Sustainable material sources are an important agenda to protect the environment and to meet human needs. In this study, Scenedesmus sp. was used to treat municipal landfill leachate via batch and continuous cultivation modes to protect the environment and explore sufficient biomass production for bioethanol production using Saccharomyces cerevisiae. Physicochemical characteristics of leachate were determined for the phases before, during, and after the process. Batch and continuous cultivation were used to treat raw leachate to determine optimum conditions for treatment. Then, the biomass of Scenedesmus sp. with and without sonication was used as a substrate for ethanol production. Sonication was carried out for biomass cell disruption for 20 min at a frequency of 40 kHz. Through batch cultivation mode, it was found that pH 7 was the optimum condition for leachate treatment. Continuous cultivation mode had the highest removal values for COD, phosphorus, and carbohydrate, namely 82.81%, 79.70%, and 84.35%, respectively, among other modes. As for ethanol production, biomass without sonication with 9.026 mg·L−1 ethanol, a biomass concentration of 3.300 µg·L−1, and pH 5 were higher than biomass with sonication with 5.562 mg·L−1 ethanol, a biomass concentration of 0.110 µg·L−1, and pH 5. Therefore, it is evident that the leachate has the potential to be treated by Scenedesmus sp. and converted to bioethanol in line with the concept of sustainable materials. [ABSTRACT FROM AUTHOR]

Reverse osmosis (RO) membrane process has been extensively used for leachate treatment both in incineration plants and landfills. However, operation and maintenance costs caused by membrane pollution limit the wide application of RO membrane. In order to further understand membrane fouling, this study analyzes the influent, effluent, concentrated liquid pollutants and membrane fouling of typical waste incineration plants and landfills in Chongqing, a city in the west of China based on the comparison of three-dimensional excitation and emission matrix fluorescence (3DEEM) and nanometer particle size. In addition, this paper discusses the change law of chemical oxygen demand (COD) and main pollutants in membrane fouling in the disc tube reverse osmosis (DTRO) system in a single operation cycle, analyzes the main components of membrane fouling, and draws the accumulation of RO membrane pollutants, in order to provide a reference for understanding the composition, formation and control of membrane fouling. [ABSTRACT FROM AUTHOR]

The resource recovery of heavy metals from effluent has significant environmental implications and potential commercial value. Chromium phosphide nanoparticles embedded in a nitrogen‐/phosphorus‐doped porous carbon matrix (CrP/NPC) are synthesized via a consecutive Cr6+ leachate treatment and resource recovery process. Electrochemical testing shows that CrP/NPC shows excellent nitrogen reduction reaction (NRR) performance, which yields the highest NH3 production rate of 22.56 μg h−1 mg−1cat. and Faradaic efficiency (16.37%) at −0.5 V versus the reversible hydrogen electrode in a 0.05 M Na2SO4 aqueous solution, as well as robust catalytic stability. The isotopic experiments using 15N2 as a nitrogen source confirm that the detected NH3 is derived from the NRR process. Finally, density functional theory (DFT) calculations show that the electron deficiency environment of the Cr site can significantly reduce the barrier of the NRR process and promote the formation of intermediate species. [ABSTRACT FROM AUTHOR]

Treatment of stabilized leachate as a by-product of municipal landfills has been a significant challenge as the leachate contains recalcitrant organic matter which has low biodegradability. In this study, the efficacy of the advanced oxidation process using cavitation–ozonation to remove recalcitrant organic matter in leachate samples from TPST Bantar Gebang was evaluated. Several operational and process parameters including pH, ozone flowrate, and contact time were varied to determine the best conditions for removing recalcitrant organic matter represented by Chemical Oxygen Demand (COD). This study determined the optimum operating conditions for the cavitation–ozonation process: pH 11, ozone discharge of 3 L/min, and contact time of 30 minutes. The result was a COD removal efficiency of 20.37%, an increase of 52.06% in the concentration of BOD5, and a 90% increase in the ratio of BOD5 to COD. This study has shown that cavitation–ozonation is an effective pre-treatment, as it increases the biodegradability of stabilized leachate and reduces the load on subsequent treatment processes.

Most landfill leachates contain organic compounds that cannot be easily separated by conventional biological processes. Recently, integration of membrane bioreactors and electro-oxidation has been proposed as a suitable option for the treatment and separation of organic and inorganic contaminants in leachate. Therefore, in the present study, the performance of submerged electro-membrane bioreactor (SEMBR) along with a conventional membrane bioreactor (MBR) on a pilot scale was evaluated for the treatment of leachate. Both bioreactors were used to compare treatment efficiency under the same conditions. The removal rates of chemical oxygen demand (COD), ammonia nitrogen (NH4+–N), phosphate (PO43−–P), color, UV254, and metals were investigated. The results showed that applying electric current to the MBR could approximately increase the COD removal efficiency from 94 to 98.5%; PO43−–P removal from 70 to 99%; NH3+–N removal from 91 to 99%; UV254 removal from 80 to 96%; and heavy metals removal from 40 to 95%. Humic acid removal efficiency as another indicator of humic substances was increased from 75% in the MBR to 96% in the SEMBR process. The results also showed that the effluent can be introduced into the wastewater treatment plant for further treatment. The SEMBR process achieved a minimization of fouling of membranes compared to conventional MBR. The consumption of the energy and electrode was in accordance with the previous results, and the required energy of 1.57 kWh/m3 of wastewater was calculated. The sludge volume index (SVI) in SEMBR (105 ml/g) was better than MBR (135 ml/g) due to the electrokinetic effect on the production of denser flocs. Based on the results, it can be concluded that the application of electric current can improve the performance of MBR in removing PO43−, NH4+, and membrane fouling. [ABSTRACT FROM AUTHOR]

Leachate treatment is crucial in landfill management. As landfill ages, inert constituents and ammonia nitrogen concentration in leachate increases, which results in a decrease in biological treatability. In this study, a full-scale MBR treating leachate was dynamically modeled using ASM1. The investigated landfill has been serving for more than 25 years; thus, a decrease in biodegradable organic content and an increase in nitrogen content of the leachate is expected in the years ahead. The calibrated model predicted MLSS, effluent COD, and effluent TN concentrations with high accuracy. Following the calibration study, it was found that soluble inert COD and soluble inert organic nitrogen fractions were the primary reasons of high COD and TKN concentrations in the effluent, respectively. The validated model of the full-scale MBR system treating leachate can be a useful tool to understand the limitations of the system. Soluble inert constituents of the leachate that pass through the membrane necessiate additional treatment processes for discharge into surface water bodies. [ABSTRACT FROM AUTHOR]

Background and Objective: Nowadays, due to the conventional methods of landfilling, the environmental concerns about generated leachate are becoming a global problem. Physical-chemical process is considered a potential and cost-effective solution for the treatment of municipal landfill leachate. Since jar-test are time-consuming experiments for obtaining the appropriate concentration of coagulants, the aim of this research was the treatment of landfill leachate using response surface methodology as a substitute for conventional methods in coagulation–flocculation process. Materials and Methods: Experiments were performed in a six-cell jar-test with effective volume of 500 mL. The ability of Ferric chloride hexahydrate to response to four parameters including COD, TSS, alkalinity and turbidity was investigated. To evaluate the model and optimization of coagulant concentration and pH, central composite design and response surface methodology were used due to the highest removal efficiency. Physical and chemical analyses were performed based on standard methods for the examination of water and wastewater. Results: The results showed that the quadratic model was achived for the three responses (COD, TSS and alkalinity) and the Reduced Quadratic model was obtained for Turbidity under the optimum conditions for the concentration of 10.23g/L at pH 8.85. Verification experiments, under optimum conditions in removal of COD, TSS, turbidity and alkalinity resulted 66.79%, 88.61%, 97.53% and 67.89%, respectively. Statistical studies (ANOVA table, the amounts of R2 and P-value) showed that the models were suitable for providing experimental data and in all models, the R2 value was greater than 0.99. P-value values also showed that the effects of quadratic model and reduced quadratic model were significant in ferric choloride dosage and coagulation pH. These experimental results were consistent with those predicted by the model. Conclusion: According to the obtained results by response surface methodology, coagulation–flocculation process can be used as the effective process to remove leachate inhibitors.

Considering the severe shortage of water resources in Iran, the utilization of treated municipal wastewater in the agricultural sector is an effective way for supplying water requirement of plants and reducing environmental pollution. Phytoremediation is an environmentally- friendly method to eliminate many pollutants. Vetiver (Vetiver zizanioides L. Nash) and reed plant (Phragmites australis) are two special plants for phytoremediation because of their unique physiological and morphological characteristics. The present research was carried out to improve the quality of leachate by vetiver and reed plant and, using hydroponic system evaluate their efficiency in the removal of contaminants. For this purpose a pilot study (containers containing 200 L leachate) was conducted including two plants, two densities, four retention times (3, 7, 14, 21 day) and control (with no plants). All experiments were performed with three replications. At the end of each period, BOD, COD, nitrate and phosphate were determined and evaluated. Results showed that the amount of COD, BOD, phosphate and nitrate was decreased by 68, 60, 82 and 83%, respectively, for the vetiver grass after 21 days. Also, results showed that the amount of COD, BOD, phosphate and nitrate was decreased by 65, 30, 60 and 63%, respectively, for the reed plant after 21 days. Finally, the results indicated that the best density for the treatment of vetiver grass and reed plant was a density of 4 in a closed environment. According to the results of this study, the vetiver plant and the reed plant have good potential to reduce pollutants.

Leachate waste consists of various mixtures of organic, inorganic, and heavy metal contaminants, which are responsible for groundwater and surface water contamination. Landfills apply physical, chemical, and biological processes for the treatment of leachate. Most studies on leachate treatment by coagulation and flocculation are based on the selection and performance of natural based biopolymers in comparison with various inorganic metal salts and grafted polymers used for the removal of contaminants. In addition, adsorption processes utilizing non-conventional activated carbons as absorbents are the current emerging focus of the researchers in leachate treatment. These adsorbents are low-in-cost, efficient, and renewable compared to conventional adsorbents. The present paper aimed to evaluate and review the technology utilising various greener approaches in coagulation, flocculation, and adsorption as the physicochemical approaches to leachate treatment. The challenges and future work regarding the development of these green products in the commercial markets were comprehensively evaluated.