Bioreactor Landfill Research Articles

Investigations into the landfill behaviour of raw and treated wastes

Bioreactor landfills (BLFs) basically involve recirculation of leachate in controlled quantities back into the bioreactor landfill to boost biodegradation of municipal solid wastes thereby improving its efficiency. This augmented biodegradation leading to faster and improved stabilization of landfill waste is being showcased by a study on two anaerobic bioreactors. One bioreactor is being loaded with raw wastes having high organic content causing an impediment in the biogas production and biodegradation and on the other hand, there is a bioreactor of same configuration loaded with windrow compost as treated waste having lower polluting potential. An attempt is made to showcase a comparative analysis to investigate the impact of treatment on biodegradation in both raw and treated MSWs. Over a 9–10 month study period which is currently under progress, data from the first 3 months (13 weeks) is presented. Treated wastes have given better results as compared to raw MSW due to lower polluting potential in terms of both leachate quality as well as biogas production. Speculations are being made that treated wastes will give better results for the whole study period in terms of environmental sustainability.

Application of Electrical Resistivity Tomography in Geotechnical and Geoenvironmental Engineering Aspect

Electrical resistivity tomography (ERT) has turned out to be one of the most applied and user-friendly geophysical methods in geotechnical and geoenvironmental research. ERT is an emerging technology that is becoming popular nowadays for investigating subsurface conditions. Multiple attributes of the technology using various electrode configurations significantly reduce measurement time and are suitable for applications even in hardly accessible mountain areas. It is a noninvasive test for subsurface characterization and a very sensitive method used to determine geophysical properties, i.e., structural integrity, water content, fluid composition, etc. This paper aimed to elucidate the ERT technique’s main features and applications in geotechnical and geoenvironmental engineering through four case studies. The first case study investigated the possible flow paths and areas of moisture accumulation after leachate recirculation in a bioreactor landfill. The second case study attempted to determine the moisture variation along highway pavement. The third case study explored the slope failure investigation by ERT. The fourth case study demonstrated the efficiency of the ERT method in the landfill evapotranspiration (ET) cover to investigate moisture variation on a broader scale and performance monitoring. In all of the four cases, ERT exhibited promising performance.

Performance evaluation of bioreactor landfills with leachate recirculation: an experimental study

Performance evaluation of bioreactor landfills with leachate recirculation: an experimental study

Integrated Resiliency and Sustainability Assessment of Bioreactor Landfills

Integrated Resiliency and Sustainability Assessment of Bioreactor Landfills

Anaerobic digestion of the organic fraction of municipal solid waste in a simulated bioreactor to improve predictive modeling of landfill systems

Municipal solid waste (MSW) generation is increasing globally, containing up to 57 % organic matter. Trapping and extraction of methane (CH4) produced via anaerobic digestion (AD) of the organic fraction of MSW (OFMSW) reduces CH4 released from landfills into the atmosphere. To estimate CH4 production from OFMSW, mathematical models are frequently used, but their accuracy varies under the non-ideal conditions that are inevitable in real landfilling scenarios. This work calibrates first-order decay (FOD) and Gompertz models for predicting CH4 production from the OFMSW based on experimental results from a pilot-scale landfill bioreactor operating under non-ideal conditions, namely under dry and mesophilic conditions with low leachate recirculation inteded to represent landfills in developing countries. This study achieved a 73 % and 66 % reduction in volatile solids (VS) and total solids (TS), respectively, demonstrating successful organic degradation. Models were calibrated using laboratory data, showing high correlation and accuracy >80 % in a Chemical Oxygen Demand (COD) mass balance. The experiment produced 104.3 mL CH4 g−1 VS with accurate predictions from calibrated models Non-calibrated models, however, overestimated methane production by 75 %. Work highlights the importance of modifying models for non-ideal conditions, and results provide useful information for landfills in developing countries.

The effect of waste degradation on landfill gas production in field-scale of bioreactor landfill

The effect of waste degradation on landfill gas production in field-scale of bioreactor landfill

Effects of biochar-amended soils as intermediate covers on the physical, mechanical and biochemical behaviour of municipal solid wastes

The effects of biochar-amended soils as landfill covers have been extensively studied in terms of liquid and gas permeability. However, the influences of biochar-amended soils on the performance of municipal solid wastes (MSWs) in bioreactor landfills have not been well understood. This paper investigates the potential application of biochar-amended soils as final and intermediate covers in landfills. The MSWs with biochar-amended soils as final and intermediate covers were recirculated with mature leachate in laboratory-scale bioreactors. The pH, chemical oxygen demand, ammonia and volatile fatty acids (VFAs) concentrations of leachates, mass reduction rates, settlement, methane, and total gas generations of MSWs were investigated. The results indicate that biochar-amended soils as intermediate landfill covers can provide pH-buffer capacity, increase the pH of leachate and decrease the accumulation of VFAs in the early stage of decomposition. The concentration of ammonia in the leachate with biochar-amended soils as intermediate cover is lower than that with natural soils. The application of biochar-amended soils as intermediate and/or final covers increases the biocompression ratios and settlement of MSWs. The application of biochar-amended soils as final cover slightly decreases the methane generation potential (L0). Biochar-amended soils as intermediate covers increase L0 by 10%, and biochar-amended soils as both intermediate and final covers enhance L0 by 25%. The increase in the ammonia removal, settlement, and methane yield indicates the viability of biochar-amended soils as intermediate landfill covers. Further studies can focus on the long-term behaviour of MSWs with soil covers with different biochar amendment rates and particle sizes.

Biodegradation of high cellulose-lignin content agricultural wastes in bioreactors

The bioreactor landfill is a solid waste disposal method that provides rapid degradation of solid waste and acquisition of methane. Bioreactors in which leachate circulation is carried out are generally operated anaerobically. The biodegradation of wastes with high lignin and cellulose content is very difficult. Especially under anaerobic conditions (moreover, if there is a lack of moisture), such wastes almost never decompose. In this study, the degradation of waste sunflower stalks that are difficult to biodegrade and have a high lignin-cellulose content and the production of methane gas in semi-aerobic bioreactors have been investigated. Sunflower stalks were loaded into the bioreactors in different proportions and mixed with the organic fraction of municipal solid waste (OFSWM). The bioreactors have been operated under different operating conditions. The contents of cellulose, hemicellulose, lignin, and initial and final organic matter in the wastes loaded into the bioreactors were examined. Parameters such as pH, COD, BOD5, TKN, NH4-N in leachate were analysed and the amounts of total and methane gas were measured. Initially, all bioreactors have been operated anaerobically. In the decomposition of the sunflower stalk, while 43% of the organic matter removal was achieved in the anaerobic bioreactor, 60% of the organic matter removal was realized in the semi-aerobic/anaerobic bioreactor. The other agricultural wastes were then subjected to decomposition under semi-aerobic/anaerobic operating conditions. As a result of the study, it can be said that semi-aerobic pretreatment accelerates the decomposition of agricultural waste with a high lignin and cellulose content, decreases the COD values of leachate, and increases the amount of methane.

Theoretical one-dimensional porous media model for microbial growth on pore plugging and permeability evolution and its verification

ABSTRACT The growth, reproduction, and metabolic activities of microorganisms can lead to blockages within porous media, a phenomenon commonly observed in landfill engineering. Termed as microbial plugging, this phenomenon is significantly influenced by the inherent permeability characteristics of the system. In this study, we propose a simulation model based on the Monod equation to elucidate the clogging process caused by microorganisms in one-dimensional pore channels. Our primary focus is on the application of this model in landfill bioreactor systems. We demonstrate that microbial clogging in these systems is predominantly affected by factors such as the maximum environmental carrying capacity and pore size. These factors are directly influenced by the presence of solid waste within the landfill. By offering a theoretical foundation for mitigating microbial clogging in pore channels of landfill bioreactor systems, this research has the potential to contribute to the development of more efficient and effective waste management practices.

Lime sludge assisted anaerobic bioreactor landfilling of municipal solid waste for enhanced leachate stabilization and bioenergy yield

Bioreactor landfilling even being advanced technology for enhanced stabilization of municipal solid waste (MSW), often suffers with adverse acidogenic conditions. Such conditions reinforce poor leachate stabilization, and reduced biomethane yield. This work attempts to counter the challenges of adverse MSW landfilling conditions through incorporation of waste alkaline sludge from paper industry. The amendment in anaerobic bioreactor landfilling of MSW was practiced by adding lime sludge (LS) with MSW in three distinct proportions: 20 g LS/kg MSW (LS100), 50 g LS/kg MSW (LS250) and 100 g LS/kg MSW (LS500), keeping LS0 as control. Periodic leachate and biomethane analysis showed benefits of proportionate LS addition. The control reactor often experienced leachate ponding and inhibitory conditions for anaerobic digestion. However, reactor LS250 achieved highest decrease in leachate organic strength removal (76.47 %) and biomethane production (8.315 L) over the period of landfilling. The pH and volatile fatty acids (VFAs) were in coordination with LS proportions. The LS addition beyond 100 g LS/kg MSW (LS500) could decrease the leachate pollution removal and biomethane yield. Finally, the Gompertz growth model showed excellent fit (R2 >0.997) to recorded biomethane. The study expands the scope of utilizing similar sludges for amendment of existing landfilling practices for efficient bioconversion of organic fractions of MSW.

Prediction of oxygen distribution in the waste mass from an aeration well in bioreactor landfills.

The key to upgrade the efficiency of aerobic remediation of landfills is to determine the distribution characteristics of oxygen concentration during aerobic ventilation. This study discusses the distribution law of oxygen concentration with time and radial distance based on a single-well aeration test at an old landfill site. The transient analytical solution of the radial oxygen concentration distribution was deduced using the gas continuity equation and approximation of calculus and logarithmic functions. Oxygen concentration data from the field monitoring were compared with the results predicted by the analytical solution. The results indicated that the oxygen concentration initially increased and then decreased with prolonged aeration time. With an increase in radial distance, the oxygen concentration rapidly declined, followed by a gradual decrease. The influence radius of the aeration well increased slightly when the aeration pressure increased from 2 to 20 kPa. The field test data agreed with the analytical solution prediction results, preliminarily verifying the reliability of the oxygen concentration prediction model. Results from this study provide a basis of guidelines for the design, operation and maintenance management of a landfill aerobic restoration project.

Dynamic emissions of N<sub>2</sub>O from solid waste landfills: A review

Nitrous oxide (N<sub>2</sub>O) is an important greenhouse gas (GHG) and an ozone-depleting substance that can be emitted from landfills. Understanding the dynamics of N<sub>2</sub>O and its contribution to total emissions is critical to effective mitigation measures. This study outlines the dynamics of N<sub>2</sub>O in solid waste landfills and N<sub>2</sub>O emissions from them. N<sub>2</sub>O 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 (NH<sub>3</sub>). Thus, a significant amount of N<sub>2</sub>O is generated from aerobic processes during leachate treatment. Bioreactor landfills emit more N<sub>2</sub>O than traditional anaerobic landfills. The majority of N<sub>2</sub>O emitted from bioreactor landfills is generated through different pathways, such as hydroxylamine (NH<sub>2</sub>OH) oxidation, nitrifier denitrification, and heterotrophic denitrification. These processes are affected by several factors, including the carbon-to-nitrogen (C/N) ratio, NH<sub>3</sub> oxidation rate NH<sub>3</sub> oxidation rate, redox conditions, and temperature. Addressing N<sub>2</sub>O emissions from landfills will be necessary to achieve an integrated nitrogen management strategy that helps minimize N<sub>2</sub>O emissions.

Lutispora saccharofermentans sp. nov., a mesophilic, non-spore-forming bacterium isolated from a lab-scale methanogenic landfill bioreactor digesting anaerobic sludge, and emendation of the genus Lutispora to include species which are non-spore-forming and mesophilic.

A novel anaerobic, mesophilic, non-spore-forming bacterium (strain m25T) was isolated from methanogenic enrichment cultures obtained from a lab-scale methanogenic landfill bioreactor containing anaerobic digester sludge. Cells were Gram-stain-negative, catalase-positive, oxidase-negative, rod-shaped, and motile by means of a flagellum. The genomic DNA G+C content was 40.11 mol%. The optimal NaCl concentration, temperature and pH for growth were 2.5 g l-1, 35 °C and at pH 7.0, respectively. Strain m25T was able to grow in the absence of yeast extract on glycerol, pyruvate, arginine and cysteine. In the presence of 0.2 % yeast extract, strain m25T grew on carbohydrates and was able to use glucose, cellobiose, fructose, raffinose and galactose. The novel strain could utilize glycerol, urea, pyruvate, peptone and tryptone. The major fatty acids were iso-C15 : 0, C14 : 0, C16 : 0 DMA (dimethyl acetal) and iso-C15 : 0 DMA. Phylogenetic analysis based on 16S rRNA gene sequences indicated that the new isolate was closely related to Lutispora thermophila EBR46T (95.02 % 16S rRNA gene sequence similarity). Genome relatedness was determined using both average nucleotide identity and amino acid identity analyses, the results of which both strongly supported that strain m25T belongs to the genus Lutispora. Based on its unique phylogenetic features, strain m25T is considered to represent a novel species within the genus Lutispora. Moreover, based on its unique physiologic features, mainly the lack of spore formation, a proposal to amend the genus Lutispora is also provided to include the non-spore-forming and mesophilic species. Lutispora saccharofermentans sp. nov. is proposed. The type strain of the species is m25T (=DSM 112749T=ATCC TSD-268T).

ENHANCED IN-SITU REDUCTION OF LEACHATE PARAMETERS DUE TO AERATION AND LEACHATE RECIRCULATION IN PILOT SCALE MSW BIOREACTOR LANDFILL MODELS IN TROPICAL CLIMATE

The processes for optimizing toxicity removal of leachate from pilot scale Municipal Solid Waste bioreactor landfills were attempted. Landfill models were simulated in Fibre Reinforced Plastic tanks of size 1.5m x 1.0m x 1.0m by applying interventions like aeration and leachate recirculation. It was found that the Chemical Oxygen Demand and Biochemical Oxygen Demand values increased till 46th week after which the values started reducing. On 89th week after closure of landfill, the aerobic landfill model showed the minimum values for COD (10,200 mg/l) and both anaerobic and aerobic models with leachate recirculation had the lowest BOD (4934 mg/l). By 116th week the least concentrations of COD and BOD were in anaerobic landfill model with leachate recirculation (64 and 22 mg/l). Ammonia Nitrogen was the least in aerated model with leachate recirculation by 116th week from closure (281 mg/l). Conductivity was less in the landfill models with leachate recirculation (4.2 and 5 mS/cm for anaerobic and aerobic respectively).

Study of leachate recharge model and vertical well design method for bioreactor landfills.

Leachate recharging not only solves the leachate treatment problem but also has tremendous environmental and engineering benefits. In this study, a recharge model was developed based on consideration of the inhomogeneous characteristics of the pile and the degree of clogging of the leachate collection and removal system (LCRs), and a design diagram of the maximum injection pressure Ps and the minimum setback distance ds was given. The following conclusions are obtained: the rate of diffusion in the horizontal and burial depth directions depends on anisotropy coefficient A, and the rate of development of the blocked water level on the LCRs depends on the degree of blockage h1. The development rate of the region affected by the recharging is low at the beginning of the recharging and increases rapidly when the moment Tb is reached, which decreases with the injection pressure P, and the degree of blockage h1. The safety factor of slope Fs decreases at a slower rate when the anisotropy coefficient is 0 < A < 1 and 15 < A < 20, and at a faster rate when 1 < A < 15. When the LCRs is blocked, the injection pressure P and anisotropy coefficient A increase the degree of influence on the recharge efficiency and slope stability, and when the blocked water level h1 > 30m, recharge is not recommended. This model and the vertical well design method can well simulate the recharging process and its effect on the slope stability and provide a reference for the design of vertical wells.

Introduction of acid-neutralizing layer to facilitate the stabilization of municipal solid waste landfill

Rapid stabilization is important for landfill operation and beneficial for treatment capacity recovery, biogas production, and pollution control. Acidification of municipal solid waste (MSW) landfill hinders the degradation of MSW. In this study, a leachate-recirculated landfill bioreactor with acid-neutralizing layer (reactor BL) and a control landfill bioreactor without the acid-neutralizing layer (CL) were operated for 509 days. The pH of the landfill was increased by the acid-neutralizing layer. The landfill gas production volume increased by 18.3 % in reactor BL compared with CL during the study period, and the CH4 concentration was also increased. A greater MSW mass reduction was observed in reactor BL than in CL. Microbial community analysis demonstrated that the presence of the acid-neutralizing layer promoted the abundance of methanogens. Based on these observations, it is believed that application of the acid-neutralizing layer accelerated the stabilization by mitigating the acidification of landfill, which promote the abundance of methanogens and enhance the MSW degradation. These results help to understand the influencing mechanism of acid-neutralizing layer on the landfill stabilization, and provide a new approach for the practical landfill to achieve fast stabilization.

Sustainability of waste-to-hydrogen conversion pathways: A life cycle thinking-based assessment

Waste-derived hydrogen (H2) has been identified as a clean energy source which could simultaneously abate greenhouse gas (GHG) emissions and avert municipal solid waste (MSW) from being deposited in perpetual landfills. In this study, four waste-to-hydrogen processes – gasification, pyrolysis, integrated pyrolysis-gasification, and landfill bioreactor technology – are studied with MSW as feedstock. Following technological evaluations, life cycle assessment and life cycle costing are performed for different scenarios and configurations to evaluate their environmental footprint, levelized cost of H2, and energy return on investment. Finally, multicriteria decision-making was applied using the VIKOR method under four weighting schemes to evaluate the four processes under varying decision-making contexts. Gasification results in the highest H2 outputs and energy returns, whereas pyrolysis produces the lowest levelized cost due to its biochar by-product formation. Nevertheless, all four technologies proved to be performing optimally under different weightings of environmental, economic, and social elements, suggesting the versatility of the waste-to-hydrogen concept and its suitability to be applied in various decision-making contexts. The results and novelties of this study would contribute toward planning and investment decision-making in sustainable H2 production and clean energy.

Assessment of Sewage Sludge and Coir Pith as Alternative Cover Materials to Red Soil in Bioreactor Landfills

This study assessed the performance of sewage sludge and coir pith as a potential alternative to virgin red soil as cover material in bioreactor landfills. Three field scale models of anaerobic bioreactor landfills were set up so as to study the performance of the cover materials on leachate generation time, quality and quantity. In one reactor (R1), red soil was used as the cover and was kept as control. In the other two reactors (R2 and R3), modified sewage sludge and coir pith were used as the cover materials, respectively. The leachate produced from each were analyzed based on its quality (Total Solids, pH, BOD, COD, Nitrate and Iron), quantity and generation time. Red soil provided respectively 41.08% and 25.5% reduction in BOD than modified sewage sludge and coir pith. However, coir pith showed better performance in reduction of leachate quantity, total solids, nitrate and iron, thus making it suitable for use as an alternate cover material.

Anthropocene Geochemical and Technological Signatures of an Experimental Landfill Bioreactor in the Central Valley of California

The geochemical signatures of a 12-year-old experimental bioreactor at a California landfill are used to identify elemental concentrations and ratios that characterize the landfill and relate it to the age and state of technology of the deposited waste. The bioreactor was constructed and sealed with a synthetic liner during 2001–2002 and operated and monitored as an anaerobic digester to enhance methane production. In 2013, the bioreactor was sampled and trace element concentrations of the extracted fine fractions were determined. The concentrations normalized to a regional soil composition, reveal systematic peaks for transition metals, alkali metals, heavy metals, and various metalloids and non-metals. A group of potential solder elements (Cu, Zn, Cd, In, Sn, Pb, Bi, and Sb) shows moderate to strong co-variations and is largely attributed to household electronic components and other similar products, while elements that correlated well with rare-earth and other elements are related to the diluting effect of a soil component used as cover. Batteries show modest to little effects on the overall concentrations. Circulating fluids (recycled leachate) in the controlled reactor did not completely redistribute and homogenize the elemental signatures within the time frame of the bioreactor. It is concluded that the present experimental landfill defines an Anthropocene marker identifiable by building material (plaster), PVC plastic, and household electronic components (Pb–Sn solder). These marker elements and ratios are variably diluted by soil components identified by alkali metals, rare-earths, and high field-strength elements (Hf, Zr, Nb, and Ta).

Reliability Assessment of Bioreactor Landfill Performance Using Coupled Thermo-Hydro-Bio-Mechanical Model

Reliability Assessment of Bioreactor Landfill Performance Using Coupled Thermo-Hydro-Bio-Mechanical Model