Decomposition Of Municipal Solid Waste Research Articles

Effect of landfill leachates on urban soil: A review

The increasing generation of Municipal Solid Waste (MSW) is a significant global concern, with landfills receiving around 1.4 billion tonnes of MSW yearly. Inadequate landfill management contributes to environmental degradation, with landfill leachate being a substantial outcome of MSW decomposition. Leachate contains inorganic nutrients, volatile and dissolved organic molecules and heavy metals and its properties vary depending on waste composition, moisture content and seasonal elements. Heavy metals found in leachate include Pb, Cu, Cr, Ni, Mn, Hg, Fe, Zn and Cd and Emerging Organic Contaminants (EOCs) such as Persistent Organic Pollutants (POPs), Endocrine Disrupting Chemicals (EDC), pharmaceuticals and Personal Care Products (PCPs) are also prevalent. Microplastics (MPs) have been found in raw leachate samples at concentrations ranging from 49.0 ± 24.3 to 507.6 ± 37.3 items/L. Landfill leachate production ranks among the most aggressive pollutants to the environment, particularly to soil and poses a danger of contaminating both surface and groundwater. This review examines the potential impacts of landfill leachate on soil quality and the broader implications of this phenomenon, summarizing recent scientific studies and presenting the direct and indirect effects of leachate on soil based on the literature. Bibliometric analysis of publications in the Scopus database reveals a growing scholarly interest in this topic, with the number of publications in the Science Citation Index (SCI) database increasing dramatically to over 464 articles between 2009 and 2024.

A critical review of municipal solid waste hydraulic conductivity: A mini review.

This study is a critical review of municipal solid waste (MSW) hydraulic conductivity that includes investigation of the influence of vertical stress, dry unit weight and degradation. A total of 56 studies were compiled that included laboratory-, pilot- and landfill-scale hydraulic conductivity experiments. Compacting waste and increasing vertical stress reduce MSW hydraulic conductivity via reshaping the pore networks throughout the waste matrix, reducing the void ratio and increasing tortuosity. However, the magnitude of reduction in hydraulic conductivity is dependent on stress, waste composition and decomposition. Solid waste decomposition can have opposing effects on hydraulic conductivity. Some studies have indicated that an increase in MSW decomposition results in particle size reduction and settlement that reduces the void ratio and decreases hydraulic conductivity. Conversely, some studies indicate that waste decomposition reduces the solid mass, which increases the void ratio and creates larger flow paths that increase hydraulic conductivity. The data compilation, observations and key findings from this study are beneficial for solid waste practitioners to improve design, analysis and operation of MSW landfills.

Antibiotics inhibit methanogenesis during municipal solid waste decomposition

Municipal solid waste (MSW) landfills are significant sources of antibiotics. However, the effects of antibiotics on MSW decomposition process and methanogenesis during solid waste decomposition remain insufficiently characterized. This study investigated the effects of environmentally relevant concentrations (ERCs) of antibiotics (200 μg/kg for each antibiotic) on MSW decomposition and methanogenesis in bioreactors treated with and without eight antibiotics (three tetracyclines, three sulfonamides, and two macrolides). The key phases of MSW decomposition, namely the aerobic, anaerobic acid, and methanogenic phases, were determined by analyzing the key physiochemical parameters of the leachate, including pH, chemical oxygen demand, and biochemical oxygen demand. We assessed the bacterial and archaeal compositions, along with the abundance of the gene encoding the alpha subunit of methyl-coenzyme M reductase (mcrA), during MSW decomposition using high throughput 16S ribosomal RNA (rRNA) gene sequencing and quantitative polymerase chain reactions, respectively. Our results revealed that antibiotics significantly altered the compositions of bacteria and methanogens, leading to decreased mcrA abundance and methanogenesis. Specifically, antibiotics inhibited cellulose-degrading bacteria (Firmicutes) and archaea (E2) in the anaerobic acid phase and hydrolytic bacteria (Proteobacteria) in the methanogenic phase, resulting in lower degradation of biodegradable matter than that of the biodegradation without antibiotics treatment. However, the typical MSW decomposition process indicated by the key decomposition phases was successfully separated in both bioreactors, suggesting that antibiotics did not affect overall MSW decomposition process development or the associated individual decomposition phases establishment. These findings suggest that antibiotics at ERCs may inhibit methanogenesis during MSW decomposition, thereby providing fundamental information for methane management and climate change studies.

Roles of ageing on the physical, chemical and mechanical parameters of a prototype municipal solid waste

ABSTRACT This study is mainly aimed at exploring effects of the aging-induced chemical decomposition of Municipal Solid Waste (MSW) on the shear response and physical properties of locally available MSW of Fars province, Iran, at its in-situ condition. To this end, a large direct shear device (1×1×1.1 m3) is designed, fabricated and employed to evaluate the parameters of the failure envelop at plane strain condition representing slopes of engineered landfills. Bulk disturbed samples of fresh MSW are exhumed from an operational disposal site to be implemented into the study and subsequently remolded in the large-scale shear box. Four drained shear tests are performed under a variety of vertical stresses. Next, intact components of MSW are landfilled over a period of 3, 6, and 9 months. Similar shear experiments are conducted at the end of each mentioned time interval. Mechanical behavior of MSW is completely frictional and internal friction angle of the studied MSW non-linearly increases with time from 44.2º to 55.7º. The stress-strain response is almost bilinear over a wide range of displacement. The decomposition process is further clarified in light of results of pH tests conducted on the leachate of the MSW at the end of various landfilling time intervals.

A landfill serves as a critical source of microplastic pollution and harbors diverse plastic biodegradation microbial species and enzymes: Study in large-scale landfills, China

Microplastics (MPs) are emerging pollutants. Landfills store up to 42% of worldwide plastic waste and serve as an important source of MPs. However, the study of MPs distribution and the plastic biodegradation potential in landfills is limited. In this study, the distribution of abundance, size, morphology and polymer type of MPs and plastics biodegradation species in refuse samples along landfill depths were extensively investigated within a large-scale landfill in Shenzhen, China. In addition, plastics biodegradation enzymes were evaluated in seven Chinese large-scale landfills leachate. MPs distribution pattern was investigated in all refuse samples. The abundance of MPs in refuse samples varied between 81 and 133 items/g. The size of MPs in all samples varied between 0.03 and 5 mm, and the average sizes were 1.2 mm ± 0.1 mm. The main morphology and polymer type were fragments and cellophane, respectively. Landfill depth was significantly negatively correlated with the relative abundance of MPs size 1–5 mm (p < 0.05) and was positively correlated with the relative abundance of MPs size < 0.2 mm (p < 0.05), suggesting that plastics were broken down during municipal solid waste decomposition. The multiple regression on matrices analysis further showed the landfill depths and plastic morphology significantly impact the MPs distribution. The strains, Lysinibacillus massiliensis (with relative abundance of 1.8%) for low-density polyethylene and polystyrene biodegradation, and Pseudomonas stutzeri (0.1%) for low density polythene and polypropylene biodegradation, were detected on the plastic surface with high relative abundance. Furthermore, 75 plastic degradation species and their associated 31 enzymes (breakdown 24 plastics) were discovered in seven landfills leachate samples.

Ironmaking Using Municipal Solid Waste (MSW) as Reducing Agent: A Preliminary Investigation on MSW Decomposition and Ore Reduction Behavior

Ironmaking Using Municipal Solid Waste (MSW) as Reducing Agent: A Preliminary Investigation on MSW Decomposition and Ore Reduction Behavior

Geospatial alternatives for quantification of bio-thermal influence zone in the vicinity of a solid waste dump.

Owing to the release of toxic gases, leachate and thermal emissions that originate from waste dumps, these sites significantly impact environmental sustainability. The study attempts to assess the deleterious impact of municipal solid waste (MSW) dump on surrounding forested landscape by employing geospatial technologies, which are cost and time-effective. For this purpose, temporal period ranging from 2015 to 2020, having 41 valid satellite observations has been selected for study. Firstly, the radii of intense hazardous zone and hazardous zone have been measured, as two separate parameters, which are 580 ± 30 m and 1260 ± 30 m, respectively. Secondly, average spatial extent of bio-influence zone is measured to be 1262 m while the average thermal influence zone extends up to 530 m around the MSW dumping site. A detailed analysis of influence zone variations reveals that the bio-influence zone depends on multitude of meteorological parameters, whereas the thermal influence zone relies mainly on seasonal temperature fluctuations. Moreover, the level of severity of emissions from MSW decomposition directly depends upon temperature. The long-term variability analysis of these hazardous zones reveals the stationarity of their spatial extents, signifying forest resilience. This study has proved significance of geospatial techniques as an alternate of expensive and time intensive assessment methods involving in situ measurements. So the proposed technique is beneficial for environmentalists, decision-makers and municipal authorities for analysing the extent and severity of MSW pollutants for forest community to address the problem of ecological degradation.

Viral community in landfill leachate: Occurrence, bacterial hosts, mediation antibiotic resistance gene dissemination, and function in municipal solid waste decomposition

A municipal solid waste (MSW) landfill is a significant source of antibiotic resistance, pathogens and viruses and also a habitat for microbial consortia that perform MSW decomposition. Viruses are of great significance in ecological interactions such as MSW decomposition and antibiotic resistance gene (ARG) transmission. In this study, the viral community structure and the associated driver, the linkage of viruses and their bacterial hosts, the virus-associated ARG dissemination and virtual community function on MSW decomposition were investigated in landfill leachate from seven cities, China. The seven cities include four megacities, two large-scale cities and one small-scale city, representing the leachate characters of China. The results showed that the leachates were dominated by the phage families Siphoviridae, Myoviridae and Podoviridae (91.7 ± 3.6) %. Their putative hosts were the important MSW decomposers Lactobacillus, Pseudomonas, Clostridium, Proteiniphilum, and Bacteroides. The structure of the viral community was significantly affected by pH (P = 0.007, analyzed by RDA) and the bacterial community (R = 0.83, P < 0.001, analyzed by Mantel test). The relative abundance of ARGs showed a strong correlation (R > 0.8, P < 0.01) with viral family, suggesting that viruses play an important role in ARGs dissemination. Phage regulate bacterial population abundance through top-down effects, thus participating in MSW decomposition. These results demonstrate that viral community are involve in ARGs transmission and dissemination and mediate MSW decomposition in landfill.

Microbial Mediation of Carbon, Nitrogen, and Sulfur Cycles During Solid Waste Decomposition.

Landfills are a unique "terrestrial ecosystem" and serve as a significant carbon sink. Microorganisms convert biodegradable substances in municipal solid waste (MSW) to CH4, CO2, and microbial biomass, consisting of the carbon cycling in landfills. Microbial-mediated N and S cycles are also the important biogeochemical process during MSW decomposition, resulting in N2O and H2S emission, respectively. Meanwhile, microbial-mediated N and S cycles affect carbon cycling. How microbial community structure and function respond to C, N, and S cycling during solid waste decomposition, however, are not well-characterized. Here, we show the response of bacterial and archaeal community structure and functions to C, N, and S cycling during solid waste decomposition in a long-term (265days) operation laboratory-scale bioreactor through 16S rRNA-based pyrosequencing and metagenomics analysis. Bacterial and archaeal community composition varied during solid waste decomposition. Aerobic respiration was the main pathway for CO2 emission, while anaerobic C fixation was the main pathway in carbon fixation. Methanogenesis and denitrification increased during solid waste decomposition, suggesting increasing CH4 and N2O emission. In contract, fermentation decreased along solid waste decomposition. Interestingly, Clostridiales were abundant and showed potential for several pathways in C, N, and S cycling. Archaea were involved in many pathways of C and N cycles. There is a shift between bacteria and archaea involvement in N2 fixation along solid waste decomposition that bacteria Clostridiales and Bacteroidales were initially dominant and then Methanosarcinales increased and became dominant in methanogenic phase. These results provide extensive microbial mediation of C, N, and S cycling profiles during solid waste decomposition.

Leachate characteristics: Potential indicators for monitoring various phases of municipal solid waste decomposition in a bioreactor landfill

Leachate is a contaminated liquid generated during the bio-chemical decomposition processes of municipal solid waste (MSW) that occurred at semi-solid or solid-state in a bioreactor landfill (BLF). Conceptually, leachate from a BLF is analogous to the urine generated in the ‘human body’, on which the medical practitioners rely to diagnose and remediate ailments. In line with this practice, to monitor the complex MSW decomposition processes, prolonged investigations were performed to establish the temporal variation of different chemical parameters (such as pH, electrical conductivity, chemical oxygen demand, organic- and inorganic carbon, nitrate- and ammonium-nitrogen, sugars and volatile fatty acids) of the leachate collected from different cells (age≈ 6–48 months) of a fully functional BLF in Mumbai, India. Furthermore, to understand the effect of the climate, MSW composition and landfill operating conditions on the rate of the decomposition process, chemical parameters of the leachate obtained from a landfill located in the central part of Poland were compared with the BLF. The study reveals that the chemical parameters, except for the pH, evince a rapid reduction with time and attain a constant value, which indicates the ‘stabilized MSW’. Also, native microorganisms that are an integral part of MSW consume volatile fatty acids within a year in the BLF, which facilitate the rapid transformation of the decomposition process from acidogenesis and acetogenesis to the methanogenesis phase. It is worth iterating here that based on the long-term field study, a convenient and efficient methodology, which is currently missing from the literature, has been established to understand the kinetics of different phases of anaerobic decomposition. This study would be very helpful to the landfill operators, who are interested in accelerating MSW decomposition by augmenting leachate properties.

Abiotic decomposition of municipal solid waste under elevated temperature landfill conditions

Abiotic decomposition of simulated Municipal Solid Waste (MSW) was investigated for thermal reactions that impact landfill gas components such as methane, carbon dioxide, and hydrogen. The gas composition and temperature were monitored as a function of heating rate and time. The tests were conducted at 483 kPa (70 psig), 55 wt% moisture, and 30 to 60 W controlled heat input in the presence of biological inhibitors. The gas composition trends show that for heat inputs higher than 46 W, the CH4/CO2 ratio diverges from the initial value of 1.0 to as low as 0.2, correlated to a decrease in CH4 concentration. Major findings of the study include that the primary gas composition ratio (CH4/CO2) starts to reduce from the baseline value of 1.0 as the heating rate is increased from 30 W to 51 W and further declines at significantly higher rates beyond 51 W. The hydrogen evolution was directly proportional to the amount of CH4 available in the system. Low levels of CH4 (<25%) correspond to decreased H2 levels in the system (<5%) whereas injection of CH4 gas in the system correspond with a renewed H2 generation The study provides insights into the operational conditions such as available heat and moisture leading to changes in landfill gas ratios.

Viral Community in Landfill Leachate: Occurrence, Bacterial Hosts, Mediation Antibiotic Resistance Gene Dissemination, and Function in Municipal Solid Waste Decomposition

Viral Community in Landfill Leachate: Occurrence, Bacterial Hosts, Mediation Antibiotic Resistance Gene Dissemination, and Function in Municipal Solid Waste Decomposition

Viral Community in Landfill Leachate: Occurrence, Bacterial Hosts, Mediation Antibiotic Resistance Gene Dissemination, and Function in Municipal Solid Waste Decomposition

Viral Community in Landfill Leachate: Occurrence, Bacterial Hosts, Mediation Antibiotic Resistance Gene Dissemination, and Function in Municipal Solid Waste Decomposition

A case study on establishing the state of decomposition of municipal solid waste in a bioreactor landfill in India.

Estimation of temporal changes undergone by municipal solid waste (MSW) in its physico-chemico-geomechanical properties in a bioreactor landfill (BLF) is essential for: (i) efficient landfilling, (ii) establishing the state of decomposition of MSW with time and (iii) deciding upon the appropriate time to initiate landfill mining. To achieve this, a series of destructive (DTs) and non-destructive tests (NDTs) can be conducted on the MSW samples in the BLF. With this in view, several DTs were conducted on these samples retrieved from different depths of the two cells of a fully operational BLF in Mumbai, India. Subsequently, the physical and chemical properties of these samples such as composition, moisture content, volatile solids (VS), elemental content, lignocellulosic content (i.e. cellulose, hemicellulose and lignin content) and bio-methanation potential, were determined by following the laboratory testing, as a function of time. Also, NDTs such as cone penetration test and multichannel analysis of surface waves were conducted on these cells of BLF to obtain geomechanical parameters (viz. cone resistance, sleeve resistance, friction ratio and shear wave velocity) of the MSW. Based on the data obtained from these tests, and reported in the literature, it has been observed that the VS, elemental content, lignocellulosic content and bio-methanation potential of MSW exhibits very well-defined trends, as compared to the geomechanical parameters, with time. Furthermore, it has been observed that the VS, hydrogen-, carbon- and nitrogen-content reduce significantly (≈62%, 70%, 50% and 30%, respectively), following an exponential decay, until the critical time (tcr) (≈4 years) has been achieved. As, beyond tcr these parameters remain practically unchanged, which corresponds to the 'stabilized MSW', mining of the BLF can be initiated without further delay.

DecoMSW: A Methodology to Assess Decomposition of Municipal Solid Waste for Initiation of Landfill Mining Activities

Biochemical decomposition of municipal solid waste (MSW) in landfills leads to the generation of leachate, gases and humus substances. In this context, a methodology to assess D ecomposition of MSW, designated as DecoMSW, has been developed; based on a series of tests conducted on samples of the fresh MSW and those retrieved from the active bioreactor landfill (BLF) cells of age from 13 to 48 months. Furthermore, spatial and temporal variation in the (i) physical (composition) and (ii) chemical (pH, volatile solids, total organic carbon, elemental analysis, ammonium and nitrate-nitrogen, biomethanation potential, lignocellulosic content) characteristics of the MSW samples exhumed from the landfill have been established. Finally, these characteristics were correlated vis-à-vis the respective values of the fresh MSW. From this exercise, it has been observed that except for nitrate-nitrogen, all other chemical parameters of MSW decrease exponentially with time until 20 months, and beyond that, they remain constant, which is an indication of stabilization of MSW. In short, it has been demonstrated that DecoMSW is instrumental in assessing the state of decomposition of MSW with respect to time in the BLF and facilitates initiation of the landfill mining activities.

Study of kinetic and thermal decomposition from municipal solid waste pellets using model-fitting methods

Reaction rate model could be determined from kinetic characteristics. Kinetic and thermal decomposition of municipal solid waste (MSW) pellets, consist of organic material, plastic, paper and leaves, with tapioca flour as binder (0%, 3% and 6%) were studied in thermogravimetric analyzer from temperature 50°C to 800°C at heating rate 10 0C/min in N2 atmospheres. The kinetic parameter were determined by Model Fitting or Coats Redfern Methods with different kinetic reaction model. Results of this study have shown that MSW pellets in various binder has activation energy values 64.64 kJ/mol and 22.06 kJ/mol for 0%, 68.83 kJ/mol and 21.99 kJ/mol for 3%, and 69.29 kJ/mol and 22.62 kJ/mol for 6% at temperature ranges between 200°C-400°C and 400°C-500°C respectively in typical three dimensional diffusion (D3) mechanism kinetic reaction model.

Numerical Model of Leachate Recirculation in Bioreactor Landfills with High Kitchen Waste Content

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.

Implications of municipal solid waste co-disposal experiments on biodegradation and biochemical compatibility.

The objective of this study was to evaluate waste biodegradation and biochemical compatibility for different waste co-disposed with municipal solid waste (MSW). Laboratory-scale reactors were operated with MSW co-disposed with special solid waste, liquid waste, or sludge waste. Early and aggressive addition of liquid wastes during reactor startup did not stimulate anaerobic decomposition of fresh MSW. The majority of the liquid waste reactors were acid stuck and had leachate pH<6 and chemical oxygen demand in the range of 50,000mg-O2/L. The majority of liquid wastes in this study were not observed to be effective anaerobic inoculums and would not be recommended as the sole moisture source for bioreactor landfills. Enhanced early methane production was observed in the MSW reactors co-disposed with sludge (anaerobic and industrial) relative to the landfill leachate control reactors and all other waste combinations evaluated. Methane generation was observed in reactors operated with foundry waste or gypsum board co-disposed with MSW. Despite biochemical methane potential (BMP) results that indicated methane generation would be inhibited with these two waste streams, co-disposing with MSW did not completely inhibit anaerobic degradation. The BMP assays provided methane yield under ideal conditions, but did not capture other benefits of co-disposal (e.g., impacts of moisture addition). A potential co-disposal waste source should not be ruled out by BMP results alone.

A constitutive model for municipal solid waste considering mechanical creep and biodegradation-induced compression

A constitutive model is developed to describe the stress–strain–time behavior for decomposing municipal solid waste (MSW) within a critical state soil mechanics framework. The model is an extension of the Modified Cam-Clay plasticity model. In this model, three sources contribute to the hardening of MSW due to volumetric strain: time-independent plastic volumetric strain, time-dependent volumetric mechanical creep strain, and time-dependent volumetric strain due to the biodegradation (decomposition) of MSW. The MSW model was evaluated through numerical analyses of large-scale one-dimensional compression tests in the laboratory and the field and the reported vertical and horizontal deformations of a MSW landfill. The associated model parameters were obtained by compositional analysis of the waste, from values reported in the literature, and by fitting numerical results to observed behavior. For the laboratory compression test, the best-fit numerical simulation over-predicted the early settlement but converged on the experimental values after 200 days. Initially, the calculated vertical strains in the field-scale test deviated from the measured strains by up to 10% over the 398-day period of the test. However, numerical results after adjusting model parameters to provide the best fit with the measured strains resulted in a maximum deviation of less than 3% over the test duration. The calculated vertical displacements of the MSW landfill were consistent with field measurements. However, the calculated horizontal displacements were significantly lower than the measured values. Sensitivity studies showed that the time-dependent settlement predicted by the model is highly sensitive to the biodegradation rate of MSW. The good agreement between numerical values and observed vertical deformations for the SWEAP section on the MSW landfill suggests that the model has the potential to assess the performance of subsystems in landfills (e.g., the performance of a side slope liner system subject to landfill settlement). However, the discrepancy between predicted and observed horizontal displacements suggests that the numerical model can be improved by incorporating deviatoric creep deformations in the constitutive model.

Microbial community composition and metabolic functions in landfill leachate from different landfills of China

Landfill leachate usually harbors complex microbial communities responsible for the decomposition of municipal solid waste. However, the diversity and metabolic functions of the microbial communities in landfill leachate as well as the factors that influence them are still not well understood. In this study, Illumina MiSeq high-throughput sequencing was used to investigate the microbial community composition and metabolic functions in landfill leachate from 11 cities in China. The microbial diversity and structure of different leachate samples exhibited obvious differences. In general, Bacteroidetes, Firmicutes and Proteobacteria were the three dominant microbial communities among the 26 bacterial phyla identified in landfill leachate, regardless of the geographical locations. Diverse bacterial genera associated with various functions such as cellulolytic bacteria (e.g., Sphaerochaeta and Defluviitoga), acidifying bacteria (e.g., Prevotella and Trichococcus) and sulfate-reducing bacteria (e.g., Desulfuromonas and Desulfobacterium) were detected abundantly in the landfill leachate. Moreover, the archaeal community in all leachate samples was dominated by the orders Methanomicrobiales and Methanosarcinales belonging to the Euryarchaeota phylum. Notably, the archaea-specific primer pair covered more diverse archaeal communities than the universal bacteria-archaea primer pair. Seventeen archaeal genera belonging to acetoclastic, hydrogenotrophic, and methylotrophic methanogens were identified, and the composition of the dominant genera in these samples varied greatly. The canonical correlation analysis indicated that landfill age, electrical conductivity, ammonia nitrogen, and total nitrogen were significantly correlated with the microbial community structure. Based on PICRUSt2, a total of 41 metabolic pathways belonging to six metabolic pathway groups were predicted, and the KEGG pathway Metabolism was the most abundant group across all leachate samples. This study provides an important insight into the composition and functional characteristics of the microbial communities in landfill leachate.