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Incineration has become an important municipal solid waste (MSW) treatment strategy, and generates a large amount of bottom ash (BA). Although some BA is reused, much BA and pretreatment residues from BA recycling are disposed in landfill. When BA and MSW are co-landfilled together, acid neutralization capacity and alkaline earth metal dissolution of BA, as well as different components of MSW may change environmental conditions within the landfill, so the degradation of organic matter and the physical and chemical properties of leachate would be affected. In this study, the effect of co-landfilled BA and MSW on the leachate characteristics during the hydrolysis and acidogenesis phase was studied using different BA/MSW ratios and MSW compositions. The results showed that the co-landfill system increased leachate pH, electric conductivity and alkalinity. For MSW with a high content of degradable components, the release and degradation of total organic carbon (TOC) and volatile fatty acids (VFA) from MSW were promoted when the BA ratio by wet weight was less than 50%, and the biodegradability of leachate was improved. When the BA ratio exceeded 50%, the degradation of organic matters was inhibited. For MSW with low content of degradable components, when the proportion of BA was less than 20%, the release and degradation of TOC and VFA from MSW were promoted and alkalinity increased. When the BA ratio exceeded 20%, the degradation of organic matters was inhibited. The 50% BA ratio could improve the bio-treatability of leachate indicated by the leachate pH and C/N ratio. However, BA inhibited the release of nitrogen (TN and NH 4 + -N) at all BA ratios and MSW compositions. At the same time, the addition of BA increased the risk of leachate collection system clogging due to the dissolution and re-precipitation of alkaline earth metals contained in BA., (Copyright © 2017 Elsevier Ltd. All rights reserved.)

This research focused on the inhibitory effects of Ca on the aerobic biological treatment of landfill leachate containing extremely high Ca concentrations. When the Ca concentration in leachate to be treated was more than 4500 mg l -1 , the total organic carbon removal rate was significantly reduced and the processing time to achieve the same removal efficiency was 1.4 times that in the control treatment without added Ca. In contrast, the total nitrogen and ammonia nitrogen (NH 4 + -N) removal efficiencies were positively related to the Ca concentration, increasing from 65.2% to 81.2% and from 69.2% to 83.7%, respectively, when the dosage of added Ca increased from zero to 8000 mg l -1 . During aerobic treatment, the reductions of solution Ca concentration were in the range of 1003-2274 mg l -1 and were matched with increases in the Ca content in the residual sludge. The inhibition threshold of Ca in the leachate treated by the activated sludge process appeared to be 4500 mg l -1 , which could be realized by controlling the influent Ca concentration and using an appropriate sludge return ratio in the activated sludge process.

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]

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]

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]

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]

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]

Despite solid wastes' landfill disposal limitation due to recent European legislation, landfill leachate disposal remains a significant problem and will be for many years in the future, since its production may persist for years after a site's closure. Among process technologies proposed for its treatment, microbial fuel cells (MFCs) can be effective, achieving both contaminant removal and simultaneous energy recovery. Start-up and operation of two dual-chamber MFCs with different electrodes' structure, fed with mature municipal solid waste landfill leachate, are reported in this study. Influent (a mix of dairy wastewater and mature landfill leachate at varying proportions) was fed to the anodic chambers of the units, under different conditions. The maximum COD removal efficiency achieved was 84.9% at low leachate/dairy mix, and 66.3% with 7.6% coulombic efficiency (CE) at a leachate/dairy ratio of 20%. Operational issues and effects of cells' architecture and electrode materials on systems' performance are analyzed and discussed. [ABSTRACT FROM AUTHOR]

• Application of membrane separation process in China is comprehensively investigated. • Leachate treatment capacity of NF is the highest in landfill and incineration plant. • A combination of NF and RO exhibits the best efficiency for leachates treatment. • Membrane processes are more likely to be adopted in economically developed regions. • Operation costs of membrane process mainly depends on the pre-treatment process. To comprehensively investigate the application of membrane separation technology in the treatment of landfill leachate in China, the performance of nearly 200 waste management enterprises of different sizes in China were analyzed, with an emphasis on their scale, regional features, processes, and economic characteristics. It was found that membrane separation technologies, mainly nanofiltration (NF), reverse osmosis (RO), and NF + RO, have been used in China since 2004. The treatment capacity of the two most dominant membrane separation technologies, i.e., NF and RO, were both almost 60,000 m3/d in 2018, and both technologies are widely used in landfills and incineration plants. Their distribution is mainly concentrated in eastern and southwestern China, where the amount of municipal solid waste (MSW) is relatively high and the economy is developing rapidly. Membrane separation technology is the preferred technique for the advanced treatment of leachate because more contaminants can be effectively removed by the technology than by other advanced processes. However, the membrane retentate that is produced using this technology—commonly known as leachate concentrate—is heavily contaminated due to the enrichment of almost all the inorganic anions, heavy metals, and organic matter that remain after bioprocessing. An economic cost analysis revealed that the operating cost of membrane separation technology has stabilized and is between 1.77 USD/m3 and 4.90 USD/m3; electricity consumption is the most expensive cost component. This review describes the current problems with the use of membrane separation technology and recommends strategies and solutions for its future use. [ABSTRACT FROM AUTHOR]

This study investigates the performance of a combined anaerobic-aerobic system in the treatment of leachate within 5 months. Experiments were carried out in a two-stage anaerobic completely stirred tank reactor followed by an aerobic reactor with effective volumes of 10, 30, and 14 L at a constant rate of 2 L/day. The reactors were placed in series so that the output from the first anaerobic reactor was the input for the second one, and the output from the second reactor was connected to the input of the aerobic phase. After an initiation phase, the organic loading rate (OLR) was increased from 0.55 to 2.65 kg COD/m3. day. The optimum OLR was found to be 2.05 kg COD/m3. day at which, the removal efficiency of chemical oxygen demand (COD) in the two-stage anaerobic phase, the aerobic phase, and the treatment system as a whole were 93%, 37.1%, and 95.6%, respectively. The BOD 5 removal efficiency of the system was 96.8%. The coefficients of determination between the removed COD and produced biogas were 0.98 and 0.99. Although the two-stage anaerobic phase increased the levels of ammonia nitrogen, alkalinity and turbidity by 31.28%, 15.18%, and 18.7%, the aerobic phase reduced these parameters by 50.30%, 57.23%, and 72.1%, respectively. Image 1 • Effect of OLRs on high COD content MSW landfill leachate. • COD removal efficiency of 93% was obtained through two-stage anaerobic digestion. • The behavior of produced biogas was similar to the COD removal rate (R2 = 0.98–0.99). • Ammonia and alkalinity increased in anaerobic phase but decreased in aerobic phase. [ABSTRACT FROM AUTHOR]

Municipal solid waste (MSW) landfill leachate is a highly contaminated liquid effluent. Leachate has a complex nature that needs to be appropriately treated before being discharged into the environment. There are various options for leachate treatment. Deciding which option should be applied is a complex process, since it depends on many factors that need to provide a balance between the technical, economic, and environmental aspects of sustainability. Multi-criteria decision-making (MCDM) methods are useful techniques to solve complex problems that cannot be easily solved. In this study, MCDM techniques are used for an evaluation of four different leachate treatment options: recirculation of leachate to a landfill site (A1), combined treatment with municipal wastewater (A2), anaerobic and aerobic sequential treatment (A3), and advanced leachate treatment based on membrane processes (A4). The selection of the most appropriate one, based on the criteria, analytic network process (ANP), and preference ranking organization method for enrichment evaluations (PROMETHEE) methods, was applied as MCDM techniques using the Super Decisions software and D-Sight software, respectively. Both the ANP and the PROMETHEE analysis results demonstrate that option A2 is the most appropriate for all of the decision-makers. [ABSTRACT FROM AUTHOR]

Plastics are indispensable in modern society but also pose a persistent threat to the environment. In particular, microplastics (MPs) have a substantial environmental impact on ecosystems. Municipal solid waste landfill leachates are a source of MPs, but leakage of MPs from leachates has only been reported in a few studies. As a modern city, Hong Kong has a remarkably high population density and a massive plastic waste generation. However, it depends on conventional landfilling for plastic waste management and traditional thermal ammonia stripping for leachate treatment. Yet, the MP leakage from landfill leachates in Hong Kong has not been disclosed. This is the first study that aimed to identify, quantify, and characterise MPs in raw and treated leachates, respectively, from major landfill sites in Hong Kong. The concentrations of MPs varied from 49.0 ± 24.3 to 507.6 ± 37.3 items/L among the raw leachate samples, and a potential correlation was found between the concentration of MPs in the raw leachate sample from a given landfill site and the annual leachate generation of the site. Most MPs were 100–500 μm fragments or filaments and were transparent or yellow. Regarding the polymeric materials among the identified MPs, poly(ethylene terephthalate) and polyethylene were the most abundant types, comprising 45.30% and 21.37% of MPs, respectively. Interestingly, leachates treated by ammonia stripping contained higher concentrations of MPs than raw leachate samples, which demonstrated that the traditional treatment process may not be sufficient regarding the removal of emerging pollutants, such as MPs. Overall, our findings provide a more comprehensive picture of the pollution of MPs in landfill leachates in Hong Kong and highlight the urgent need for adopting the consideration of MPs into the conventional mindset of waste management systems in Hong Kong. [Display omitted] • Landfill leachate is a potential source of microplastics (MPs) in Hong Kong. • Concentrations of MPs ranged from 49.0 to 507.6 items/L in raw leachates. • Most MPs were 100–500 μm fragments or filaments and were transparent or yellow. • Concentration of MPs correlated with annual leachate generation of landfill. • Ammonia stripping for leachate treatment led to increased concentrations of MPs. [ABSTRACT FROM AUTHOR]

In many developing countries, there has been growing interest in bioreactor landfills for municipal solid waste (MSW) management. This research study has been conducted for comparing leachate characterization and waste stabilization in simulated pilot-scale anaerobic bioreactor landfills. Four pilot-scale reactors were constructed and operated for 540 d. This study aimed to show whether a pilot-scale bioreactor containing sewage sludge mixed with MSW, with a geotextile filter in its drainage layer, and with recirculating leachate, could improve leachate quality and waste stabilization in a landfill. Bioreactor R1 comprised MSW and sewage sludge, while bioreactor R2 was the same as R1 but with a geotextile-1 (GT-1) filter fitted. R3 contained no sludge but only MSW and GT-1 fitted, while R4 contained no sludge but only MSW and two layers of geotextile filter (GT-2 and GT-3). All reactors were operated with leachate recirculation, simulating bioreactor landfills. The results showed that the chemical oxygen demand (COD) half-lives of leachate from the reactors were approximately 8, 7, 9, and 10 months for R1, R2, R3, and R4, respectively. By the end of the study, the waste in R2 and R4 was more stable, with 66% and 65% reductions in volatile solids, respectively. Reactor R2, which contained MSW, sewage sludge, and one-layer geotextile (GT-1), provided higher stabilization of MSW and shorter COD half life than the other reactors. [ABSTRACT FROM AUTHOR]

Abstract The remediation of volatile organic compounds (VOCs) from aqueous solution using Municipal solid waste biochar (MSW-BC) has been evaluated. Municipal solid waste was pyrolyzed in an onsite pyrolyzer around 450 °C with a holding time of 30 min for the production of biochar (BC). Physiochemical properties of BC were assessed based on X-Ray Fluorescence (XRF) and Fourier transform infra-red (FTIR) analysis. Adsorption capacities for the VOCs (m-xylene and toluene) were examined by batch sorption experiments. Analysis indicated high loading of m-xylene and toluene in landfill leachates from different dump sites. The FTIR analysis corroborates with the Boehm titration data whereas XRF data demonstrated negligible amounts of trace metals in MSW-BC to be a potential sorbent. Adsorption isotherm exhibited properties of both Langmuir and Freundlich which is indicative of a non-ideal monolayer adsorption process taking place. Langmuir adsorption capacities were high as 850 and 550 μg/g for toluene and m-xylene respectively. The conversion of MSW to a value added product provided a feasible means of solid waste management. The produced MSW-BC was an economical adsorbent which demonstrated a strong ability for removing VOCs. Hence, MSW-BC can be used as a landfill cover or a permeable reactive barrier material to treat MSW leachate. Thus, the conversion of MSW to BC becomes an environmentally friendly and economical means of solid waste remediation. Graphical abstract Image 1 Highlights • Landfill leachates were contaminated with elevated levels of m-xylene and toluene. • Biochar produced from municipal solid waste had low amounts of trace metals. • Volatile organics were removed well by biochar without an ideal monolayer mechanism. • Biochar production from organic waste is a sustainable solution to waste management. [ABSTRACT FROM AUTHOR]

The paper analyzes the advanced technologies of wastewater treatment with a high content of organic pollutants and ammonium ions. Two different bi-stage scenarios for the treatment of such effluents are proposed. The first scenario includes the pretreatment in aerated lagoons and the final stage at the wastewater treatment plants after appropriate dilution with municipal sewages. The second scenario also includes the first stage in aerated lagoons with a tertiary treatment at the plant for cyanobacteria cultivation with the use of obtained biomass for biofuels production. The effects of the aeration periodicity on the leachate treatment efficiency and also on the composition of microbiocenosis in the aerated lagoons were investigated. The leachates of the Lviv landfill of municipal solid waste (MSW) were used in experimental investigations. The Lviv landfill of MSW was used for domestic and industrial wastes deposition for almost six decades, since the 1960s. It was found that the highest effect of ammoniacal nitrogen removal was obtained in the mode of periodic aeration, with the cycle duration of two hours including the one-hour aeration. It was found that the microorganisms extracted from the leachates of the Lviv MSW landfill are prospective for the new biotechnologies of treatment of the highly concentrated wastewaters, since this microbiocenosis is resistant to the widespread pollutants, in particular to heavy metal ions. [ABSTRACT FROM AUTHOR]

The purpose of this work was to study the treatment of a leachate coming from the municipal solid waste landfill of Astana (Kazakhstan). Physical (striping and adsorption), biological and photochemical processes were applied separately or in combination, and the treatment efficiency was attended in terms of carbon and nitrogen removal. The leachate carbon was by 45%-60% inorganic while nitrogen was almost 100% inorganic in the form of ammonia. The results showed that inorganic carbon and ammonia can be almost entirely removed by air stripping at pH = 7 and pH = 12, respectively. The removal of organic carbon by stripping alone was lower than 4% but combined to adsorption reached 20%, and to biological treatment 30%. The removal of organic carbon by photochemical oxidation alone was 43%. The combination of stripping, adsorption and biological treatment resulted in 37% organic carbon and with the addition of photochemical oxidation step the removal was increased to 59%. In overall, total carbon removal reached 85% and total nitrogen removal almost 100%. The results showed that the decomposition of landfill leachate carbon is a challenging task requiring a combination of processes. On the contrary, as almost all nitrogen is inorganic, air stripping at elevated pH alone can sufficiently eliminate it. [ABSTRACT FROM AUTHOR]

This study investigated the biodegradability of composting leachate and biogas production in different Organic Loading Rates (OLRs) in lab-scale series AMBR-ASBR bioreactors, Anaerobic Migrating Blanket Reactor (AMBR) and Anaerobic Sequencing Batch Reactor (ASBR). The raw Leachate with OLRs of 1.04–19.65 gCOD/L.d went into the AMBR reactor and then into the ASBR reactor with hydraulic retention time of 24 h. The produced methane and biogas were measured by GC-TCD and gas meter. The results showed that the best removal efficiency for BOD 5 , COD and readily biodegradable COD (rbCOD) in AMBR-ASBR hybrid reactor were 99.43%, 97.35% and 99.79%, respectively. The maximum amounts of biogas and methane production were 16.37 and 9.99 L in OLR of 10.08 gCOD/L.d. With the increase in OLRs, biogas production also increased, but in higher OLRs (18.52 gCOD/L.d) with a sudden increase in OLR, methane and biogas production decreased. Moreover, the ratio of the biogas production to inlet COD was 1.35 L (R 2 = 0.994), that is equal to the ratio of produced biogas (L) to inlet Volatile Suspended Solids (VSS) (g) (R 2 = 0.972). Thus, considering OLRs effects, it was observed that the AMBR-ASBR hybrid reactor as a novel series system could be remarkably efficient in compost leachate treatment and increasing biogas production. [ABSTRACT FROM AUTHOR]

One of the inevitable drawbacks of sanitary landfilling of municipal solid waste (MSW) is the production of leachate. This study aimed to assess the treatment of leachate for the purpose of removing ammonium and organic carbon using the anammox process. To grow autotrophic bacteria in the reactor, the carbon source was gradually decreased from 500 mg L–1 to less than 10 mg L–1. NH4 and nitrite concentrations from 5 and 6.6 to 300 and 396 mg L–1, respectively, were injected into the reactor and the removal was investigated. Finally, in order to assess carbon and nitrogen removal simultaneously, the concentrations of chemical oxygen demand, ammonia, and nitrite were increased to 250, 500, and 660 mg L–1, respectively. The highest efficiencies for ammonium and nitrite removal that were obtained were 76.69% and 91.12%, respectively, at the volumetric loading rate of 0.15 and 0.132 kg m–3 d–1 in the hydraulic retention time (HRT) of 24 h. As HRT decreased from 24 to 6 h and the loading rate increased, the highest efficiencies achieved for the removal of ammonia and NO2 were 95.19% and 80.56%, respectively. Eventually, ammonium removal efficiency did not exceed 22.28% while the removal efficiency for organic matters was 72.63%. Contrary to nitrite, ammonium removal is dependent on the appropriate performance of the anammox process. [ABSTRACT FROM AUTHOR]

This study illustrates the characteristics and contamination potential through leachate pollution index (LPI) of raw leachate as well as leachate after treated with chemical coagulants for both the dry and rainy seasons. The leachate samples were collected at a regular intervals of time from four distinct solid waste disposal sites--sanitary disposal (Dhaka), open disposal (Chittagong), sanitary disposal (Khulna) and open disposal (Rajshahi)--at four cities in Bangladesh. The study was carried out from November 2013 to September 2014; these periods covered both the dry and rainy seasons. In the laboratory, standard test methods were followed for the determination of physical and chemical as well as organic and nitrogen compounds in leachate samples. The leachate samples of dry season showed comparatively the higher pollutant concentration than that of rainy seasons of the selected disposal sites. Based on results, it was observed that the concentration of raw leachate and consequently its LPI values exceed the permissible limits of maximum leachate discharge standards. Here it can be noted that the leachate generated from the selected disposal sites is highly contaminated and exceed the LPI value 5.77 (Bangladesh) as well as 7.38 (India and Hong Kong) of maximum leachate discharge standards and proper treatment will have to be ensured before discharging the leachate into the natural streams. In the laboratory, then the leachate was treated using FeCl3 at optimum dosage as well as the concentration and consequently the values of LPI of treated leachate were found within the limit of maximum leachate discharge standards. [ABSTRACT FROM AUTHOR]

The management of solid waste is one of the major challenges faced by any developing country. In recent years, the increase in the urban population, together with their changes in production/consumption patterns, the improvement in people's living standards and the proliferation of suburbs have led to a significant increase in solid waste in Morocco, with an overall production of 6.9 million tons per year. The quantity of municipal solid waste (MSW) is about 5.3 million tons per year, equivalent to 0.76 kg per day per capita. Waste generated in rural areas has been estimated as 1.6 million tons per year, corresponding to 0.3 kilo per capita per day. Systematic waste collection practice is a major bottleneck, yet it is a major factor that contributes to the success of any waste management program. According to official estimates, approximately 82% of the urban population and only 20% of the rural population benefit from the existing collection services. The low rate of collection causes open dumps and the dispersion of garbage in the streets. According to a recent survey in 2013, only 37% of the collected waste are deposited in controlled landfills. Most of the waste dumping sites are located in the former quarries. This mismanagement causes significant negative impact on the environment and water resources since 40% of the landfills are closer to the rivers and aquifers. The release of greenhouse gases, as well as the proliferation of insects are also a serious nuisance, causing health and environmental problems. In addition, the sector must also confront challenges manifested by the persistence of the nearly 200 landfills that have not yet been rehabilitated. A World Bank study in the year 2003 estimated costs related to the weak performance of the solid waste management system as 0.5% of the gross domestic product (GDP). To deal with the challenges posed by the mismanagement of household waste, several measures and initiatives were undertaken by the government. This includes, among others, the launch of the National Household Solid Waste Program (NHSWP) in the year 2007 by the Moroccan Ministry of Interior and the Moroccan Secretary of State for Water and Sustainable Development, with the support of the World Bank. The cost of the program was estimated to be 40 billion MAD, allocated in the following proportions: collection and cleaning: 72%; construction and operation of controlled landfills: 14.6%; rehabilitation and closure of the dumps: 6.2%; field studies, follow-up and control: 3.5%; sorting, recycling and valorization: 1.8%; communication, awareness and training: 1.8%. In Morocco, designated public landfills are managed by 12 companies and they have achieved a turnover of 268 million dirhams and employed 150 agents, in addition to the creation of many direct and indirect jobs related to sorting, transporting and recycling services. Landfill leachate is considered as a high-strength wastewater which is often characterized by high salinity, organic loads, and a complex mixture of hardly biodegradable substances such as proteins, lipids, phenolic compounds and toxic ammonium ions. The treatment of leachate is an important issue in Morocco because there is no treatment system (in-situ or ex-situ) that achieves complete treatment of the leachates. Therefore, in order to meet the discharge limits, most of the treatment process is limited to forced evaporation. This process leads to odor problems near the treatment site and the alteration of surface and ground water quality. At present, this is a social nuisance and a burden to the municipalities. However, some newly established controlled landfills have introduced processes such as reverse osmosis (RO), in the city of Rabat, and a two-step process comprising of leachate pretreatment by an ultrafiltration membrane bioreactor followed by RO treatment (the Evalix process), in the city of Meknès. From a resource recovery viewpoint, Morocco has confirmed its ambitions to upgrade biogas production through two major biogas capture/valorization initiatives in the cities of Fez and Oujda, respectively. The new landfill located in the city of Fez is able to upgrade a part of the biogas generated from organic waste for the production of electricity (487,170 KW). It is noteworthy to mention that the cumulative electrical energy injected into the public lighting network in the city of Fez reached 5.8 million KW in one year, representing approximately 25% of the energy required for street lighting in Fez city. Concerning sorting activities, several new projects were launched for social reasons, especially to integrate and educate the manual sorters (ragpickers). The sorters were brought together to a cooperative society so that their activities were monitored and their security conditions can be enhanced. This includes the establishment of sorting hangars, administrative premises and cloakrooms. Marrakesch city has constructed the first recycling center at new Marrakech controlled landfill, one of the largest in North Africa. [ABSTRACT FROM AUTHOR]

• Leachate foaming properties were systematically characterized by the designed foam analyzer. • Linear alkylbenzene sulfonate (LAS) is demonstrated to be an indispensable surfactant in leachate. • The distribution characteristics of LAS in leachate are consistent with the variety of foaming performance. • The pH value of leachate is positively correlated with the concentration of anionic surfactants. Serious foaming problems and the excessive consumption of defoamer have undoubtedly become one of the most critical problems that hinder municipal solid waste (MSW) leachate treatment efficiency and industry development. Since there is limited research penetrating the foaming mechanism and identification of the key surfactants, current defoaming and surfactant removal techniques lack pertinence and orientation. In this study, a foaming characterization device was developed and ultra-performance liquid chromatography-tandem mass spectrometry (UPLC/MS/MS) was optimized to accurately identify the key surfactants affecting leachate foaming and offer a glimpse into their interaction mechanisms. This study collected leachate samples from 9 typical landfills and waste-to-energy facilities of various waste compositions, climatic conditions, ages, and geographical locations. The foaming problem of leachate was mainly centered on raw leachate and nanofiltration membrane concentrate (NFC). Fresh leachate performed with relatively low foaming capacity and foam stability, associated with low surfactant concentration. The pH value of the system was positively correlated with the concentration of anionic surfactants, indicating significant impacts on surfactant release in MSW. Since the distribution characteristics of linear alkylbenzene sulfonate (LAS) in leachate were consistent with the variety of foaming performances, LAS proved to be an indispensable surfactant in the leachate involved in this study, and its content proportion escalated to 92.87% in aged leachate. [Display omitted] [ABSTRACT FROM AUTHOR]

In this study, the leachate treatments were compared in two simulated landfill bioreactors with different operation modes. In one reactor, the leachate was circulated between a landfill and a methanogenic reactor, while the other reactor was operated using direct recirculation of the leachate. The pH, Chemical Oxygen Demand (COD), volatile fatty acids (VFA), NH4+-N of leachate, and the biologically degradable material (BDM), the enzymatic activities of municipal solid waste (MSW) were analyzed to achieve the essential characterization of the landfill. The results revealed that the loss of organic materials from the landfill occurred in an active methanogenic environment in the later period, while the environment was acidic due to a high concentration of VFA and contained a large volume of BDM during the early stage. In addition, the dehydrogenase and polyphenol oxidase activities of refuse were majority higher in the bioreactor landfill that was connected to a methanogenic reactor. Furthermore, the efficiency of leachate treatment was enhance at least 20%, and the stabilization process was accelerated over 50% in the landfill that was operated in conjunction with the methanogenic reactor when compared to the landfill in which there was direct leachate recirculation. [ABSTRACT FROM AUTHOR]

In this study, leachate samples from the IZAYDAS landfill were collected and analyzed for a period of 30 months from December 2001 to May 2004. The landfill is located in the city of Kocaeli in Turkey and it has been in use since 1998. The leachate is pre-treated by a full-scale physico-chemical treatment system prior to transportation to the municipal wastewater treatment plant for a final treatment and disposal. Chemical analyses were performed on both raw and pre-treated leachate samples and the temporal variation of several parameters were monitored including pH, COD, SS, phenol, Total P, S−2, CN−, Ba, and selected heavy metals (Cr, Ni, Cu, Zn, Cd, Hg, As, Sn, Sb, Pb). The data collected were fitted with trendlines to represent temporal variations. Principal component analysis (PCA) as a multivariate statistical method was later used for filtering the data so that only the significant independent variables could be determined. While the method identified Cu, Total P, Zn, and COD for the raw leachate, Zn, Cu, Total P, S, and COD were the ones most essential for explaining the variation within the data for the pre-treated leachate. The concentrations of the most of the parameters in the raw leachate were lower than the ranges reported in the literature. The results show that a physico-chemical treatment planting incorporating a dissolved air flotation (DAF) stage can be used as an effective alternative for landfill leachate pre-treatment. [ABSTRACT FROM AUTHOR]

The generation of contaminated leachate remains an inevitable consequence of the practice of solid waste disposal in landfills. The collection and treatment of leachate have become common practice in order to prevent environmental pollution. Leachate treatment is highly dependent on the quality of leachate, which in turn is influenced by various factors including waste composition and operational procedures. This paper investigates the treatability of high-strength leachate from pre-sorted and baled municipal solid waste characterized by high organic and moisture content. For this purpose, waste disposal and leachate generation rates were monitored. Leachate samples were collected and analysed for selected indicators including BOD, COD, pH, and NH 4 -N and a pilot scale treatment plant with coagulation, precipitation and sequential batch biological reactors was constructed to evaluate the feasibility of leachate treatment. Concentration levels were related to biological activity within the landfill and the results indicated that (1) pre-sorting and baling of the waste did not hinder waste stabilization; and (2) the high organic and moisture contents resulted in an extremely strong leachate, particularly at the onset of biodegradation processes, which can affect the leachate treatment facility. The effectiveness of the pilot plant in treating the leachate exceeded 90% using COD and NH 4 -N as indicators. [ABSTRACT FROM AUTHOR]

Stabilised leachate usually contains lower concentration of organic compounds than younger leachate; it has low biodegradability and generally unsuitable for biological treatment. The effectiveness of tetravalent metal salts in a coagulation-flocculation (C–F) process is still inclusive. Application of natural coagulants as an alternative to the chemical could reduce chemical usage, is less costly, and environmentally friendly. Hence, the objective of the current research is to examine the possibility of reducing the amount of Tin (IV) chloride (SnCl 4) as a primary coagulant by adding Jatropha curcas (JC) as a flocculant as a sole treatment through the C–F process in treating concentrated suspended solids (SS) (547 mg/L), colour (19,705 Pt–Co) and chemical oxygen demand (COD) (4202 mg/L) in stabilised landfill leachate. The work also aims to evaluate the sludge properties after treatment. Functional groups, such as carboxylic acids, hydroxyl and amine/amino compounds (protein contents), were detected in the JC seed to facilitate the C–F process by neutralising the charge pollutant in water and cause the possibility of hydrogen bonding interaction between molecules. The combination of JC seed (0.9 g/L) as a flocculant reduced the dosage of SnCl 4 as a coagulant from 11.1 g/L to 8.5 g/L with removals of 99.78%, 98.53% and 74.29% for SS, colour and COD, respectively. The presence of JC improved the sludge property with good morphology; the particles were in a rectangular shape, had clumps and strong agglomeration. These properties of sludge proved that JC seed could enhance the adsorption and bridging mechanism in the C–F procedure. [Display omitted] • The effectiveness of tetravalent metal-based coagulants is still inclusive. • The application of Jatropha curcas (JC) seed aims to reduce SnCl4. • 99.78, 98.53, and 74.29% reductions in SS, colour, and COD were obtained. • Lower SnCl 4 dosages maintained the same removal in the presence of JC. • The treatment was carried out in a worst-case scenario with no other treatments. [ABSTRACT FROM AUTHOR]

Surface spraying, horizontal trenches, and vertical wells are the most common leachate recirculation system used at landfills in engineering practice. In order to quantify the efficiency of the three aforementioned recirculation systems, a hydro–biochem–mechanical-coupled model was developed in the present work, which can describe hydrodynamic and biochemical behaviors in food-waste-rich landfills. A typical landfill cell was modeled in COMSOL. The results indicate that leachate recirculation can accelerate the decomposition of municipal solid waste (MSW) with food-rich waste content, relieving acidification, improving gas generation efficiency, and consequently, increasing the early settlement in landfills. [ABSTRACT FROM AUTHOR]

Despite the strong ability for complexation of heavy metals, a high amount of humic substances (HS) is always contained in membrane retentate from municipal solid waste landfill leachates treatment processes. Submerged Combustion Evaporation (SCE) can be used to effectively concentrate the membrane retentate. However, the impact of the SCE treatment on HS complexation capacity is still unclear. Since cadmium (Cd) plays a vital role in the pollution of soil and food, this study investigated the influence of the SCE treatment on the Cd complexation potential of leachate HS. Specific effects and complexation properties on Cd complexation of leachate HS before and after the SCE treatment were demonstrated using the Non-Ideal Competitive Adsorption model. The results showed that the Cd complexation capacity of carboxyl sites increased from 3.76 to 4.65 mol/kg-Total Organic Carbon (TOC) after the SCE treatment, which agreed with the stoichiometric number of proton binding sites. Moreover, characterization results indicated that SCE increased the affinity of HS for Cd by enhancing the overall aromaticity of HS (E 2 :E 4 from 9.8 to 9.3), dominantly due to the humic acid contribution. By modeling the practical Cd remediation scenarios, the enhanced Cd complexation performance of HS after SCE treatment was observed even at low pH values (pH = 5) or insufficient TOC content (TOC = 50 mg/L). Image 1 • Cd complexation capacity of leachate HS increases after SCE treatment. • The complexation parameters of HS increase from 1.38 to 1.61 after SCE. • Increased aromaticity degree of HS leads to the enhanced complexation capacity. • The aromatization of HA increased by 0.5% is a dominated factor. • pH value plays a significant role at low level of TOC (50 mg/L). Main finding:Complexation performance of leachate humic substances is enhanced after Submerged Combustion Evaporation. Increased aromaticity degree dominates the enhancement. [ABSTRACT FROM AUTHOR]

Solid waste generation has been projected to increase worldwide. Presently, the most applied methodology to dispose of solid waste is landfilling. However, these landfill sites, over time release a significant quantity of leachate, which can pose serious environmental issues, including contamination of water resources. There exist many physicochemical and biological landfill leachate treatment schemes with varying degrees of success. With an increasing focus on sustainability, there has been a demand for developing eco-friendly, green treatment schemes for landfill leachates with viable resource recovery and minimum environmental footprints. Microalgae-based techniques can be a potential candidate for such a treatment scenario. In this article, research on microalgae-based landfill leachate treatments reported in the last 15 years have been summarized and critically reviewed. The scale-up aspect of microalgae technology has been discussed, and the related critical factors have been elucidated. The article also analyzes the resource recovery potential for microalgal techniques with respect to leachate treatment and explores possible methodologies to minimize the environmental footprints of the microalgae-based treatment process. The future research potential in the area has been identified and discussed. [ABSTRACT FROM AUTHOR]

Landfill application is the most common approach for biowaste treatment via leachate treatment system. When municipal solid waste deposited in the landfills, microbial decomposition breaks down the wastes generating the end products, such as carbon dioxide, methane, volatile organic compounds, and liquid leachate. However, due to the landfill age, the fluctuation in the characteristics of landfill leachate is foreseen in the leachate treatment plant. The focuses of the researchers are keeping leachate from contaminating groundwater besides keeping potent methane emissions from reaching the atmosphere. To address the above issues, scientists are required to adopt green biological methods to keep the environment safe. This review focuses on the assorting of research papers on organic content and nitrogen removal from the leachate via recent effective biological technologies instead of conventional nitrification and denitrification process. The published researches on the characteristics of various Malaysian landfill sites were also discussed. The understanding of the mechanism behind the nitrification and denitrification process will help to select an optimized and effective biological treatment option in treating the leachate waste. Recently, widely studied technologies for the biological treatment process are aerobic methane oxidation coupled to denitrification (AME-D) and partial nitritation–anammox (PN/A) process, and both were discussed in this review article. This paper gives the idea of the modification of the conventional treatment technologies, such as combining the present processes to make the treatment process more effective. With the integration of biological process in the leachate treatment, the effluent discharge could be treated in shortcut and novel pathways, and it can lead to achieving "3Rs" of reduce, reuse, and recycle approach. [ABSTRACT FROM AUTHOR]