Landfill Cells Research Articles

Amendment for increased methane production rate in municipal solid waste landfill gas collection systems

Optimization of methane production rate can potentially decrease the operational lifetime of the landfill site and assist with better management of methane harvesting from the landfill cells. Increased moisture content in landfill cells is known to increase the rate of methane production. Several natural biopolymers can sustain moisture content in a solid matrix while providing a scaffolding for microbial communities to grow. This research examined the effect of the biopolymer, produced by Rhizobium tropici, on bench-scale methane generation from municipal solid waste. The addition of the R. tropici biopolymer increased the rate of methane production from 27% to 78% when compared to the control study for low and high concentrations of biopolymer amendment, respectively. R. tropici biopolymer shortened the lag phase by up to six days over the control, depending on the level of biopolymer amendment added to the solid waste. The mechanism appears to be facilitating biofilm formation through the combination of increased moisture retention and surface modification of the solid waste. Incorporation of biopolymer amendment in the alternative daily cover activities at commercial landfills could provide a viable approach for full scale application.

Comprehensive coupled thermo-hydro-bio-mechanical model for holistic performance assessment of municipal solid waste landfills

A comprehensive coupled thermo-hydro-bio-mechanical (CTHBM) model is proposed to simulate the coupled interactions between the hydraulic, mechanical, biochemical, and thermal processes observed in municipal solid waste (MSW) and also assess their influence on the long-term performance of MSW landfills. The hydraulic model is based on two-phase fluid flow through unsaturated porous media. The biochemical model is based on a two-stage anaerobic biodegradation model. The thermal model is based on conductive heat transport with heat generation rates derived from the biodegradation model. The mechanical model uses the soft-soil-creep constitutive model to simulate the time-dependent creep behavior of the waste. The effect of biodegradation and subsequent mass loss on the waste settlement is also incorporated. Using the proposed CTHBM model, two numerical simulations were performed on a typical full-scale landfill cell geometry to determine the long-term spatial and temporal variations in the hydraulic, mechanical, biochemical, and thermal characteristics of waste under conventional and bioreactor landfill conditions. The influence of the dynamic changes in the waste characteristics on the shear behavior of a textured geomembrane-geotextile interface in the bottom liner and cover system of the simulated landfill cell was also examined.

Influence of Waste Temperatures on Long-Term Landfill Performance: Coupled Numerical Modeling

A coupled thermo-hydro-bio-mechanical (CTHBM) numerical model to simulate the long-term behavior of municipal solid waste in landfills is presented. Three numerical simulations—a conventional landfill simulation with no leachate injection (CONV) and two bioreactor landfill simulations involving leachate injection—were carried out by applying the CTHBM model to a typical two-dimensional (2D) landfill cell configuration to analyze the effect of temperature on the long-term performance characteristics of a landfill system. Of the two bioreactor landfill simulations, one (BIOR-T) incorporated temperature effects on the waste decomposition, while the other simulation (BIOR-NT) did not. For the waste conditions simulated, the CONV and BIOR-T had a maximum waste temperature of 54°C and 62°C, respectively. The temperatures at the bottom liner were determined to be in the range of 1°C–32°C and 1°C–39°C over the entire simulation time of the CONV case and BIOR-T case, respectively. The effect of waste temperatures on moisture distribution, methane gas production, and landfill surface settlement was also assessed. The surface settlement response for BIOR-T and BIOR-NT simulations suggests that incorporating the effect of waste temperatures on the waste decomposition is important for a realistic prediction of the waste settlement in landfills. The BIOR-T and BIOR-NT simulations had a similar interface shear response, suggesting that the changes in the stiffness and shear strength of waste, due to incorporating temperature effects on the biodegradation rate, have no noticeable impact on the interface shear response in the bottom liner system. Overall, the proposed CTHBM model can be used to predict long-term performance characteristics (e.g., moisture distribution, landfill gas production, settlement of waste, temperatures) relevant for effective design of bioreactor landfills.

Assessment of water quality status in the impact area of the “Piškornica” landfill

Disposal of household and industrial waste at the Piškornica site began in 1982 on what was then an unmanaged landfill cell, which allowed contamination to pass into underground layers. Landfill rehabilitation was conducted between 2005 and 2013 and conformed to the environmental protection conditions and measures that were prescribed by an EIA procedure, but rehabilitation still has not been fully completed. An environmental permit was issued for rehabilitation of the landfill. The decision and environmental permit prescribed groundwater quality monitoring. Prior to these documents, five piezometers were placed into operation in 1991. The objective of this paper is to determine the potential differences in ground and surface water quality that may have resulted from landfill operations, effectiveness of the rehabilitation efforts, and the potential risk of contamination of the Ivanščak water well. The results of the research were subjected to statistical analyses (e.g., T-test and ANOVA). Based on the regional flow model, a numerical groundwater flow model and contamination transport model were created, which provided scenarios for the potential spread of pollution from the Piškornica landfill while considering different water well operation regimes. It was concluded that a) even though rehabilitation has not been completed, the groundwater quality status improved and b) none of the analysed real flow scenarios generated redirection of streamline patterns towards the Ivanščak water well. Considering future development and likely increase of the Ivanščak well capacity, the expansion of monitoring was proposed for additional measuring locations

PLANNING OF THE SANITARY LANDFILL SYSTEM IN SURAKARTA CITY

Waste processing sites have a sueful life, as the activities and populations increase in the Surakarta City has led to increasing volume of the garbage that come to landfill every day. Putri Cempo’s Landfill operation system still uses the conventional system, called open dumping. This system causes accumulation of garbage increasingly mountainous and not polluted. Therefore, a system called sanitary landfill is planned to increase landfill capacity and extend the life of landfill.The purpose of this final project is to plan the development of landfill in Surakarta City with a sanitary landfill system. This development is made by making landfill cell in lieu of the open dumping system. The method of landfill cell waste using the trench method to further optimize landfill cell land.The development of TPA using a sanitary landfill was carried out in an area of 6.7 Ha. With the prediction of the amount of waste entering the landfill in 2026 around 15.041 tons/year. The age of using landfill is predicted to range from 5 years and the drainage size used is 50x50 and 100x50 made from river stone for around the landfill and made from precast cell for around the facilities building

Modeling elasto-visco-bio-plastic mechanical behavior of municipal solid waste in landfills

This paper presents a mechanical model for the prediction of short-term and long-term settlement of municipal solid waste in landfills. The load-induced volumetric compression, shear behavior, tensile behavior, and the time-dependent creep compression behavior of the waste are modeled using the soft soil creep model. The compression induced by decomposition of waste is modeled based on the phenomenon of wetting-induced strains observed in compacted fills with expansive soils. The proposed model is validated using benchmark datasets obtained from two long-term laboratory experiments performed on waste samples obtained from a landfill in UK. Two additional numerical simulation cases (CONV—without leachate injection and BIOR—with leachate injection) were examined by application of the proposed mechanical model on a typical full-scale landfill cell geometry to determine the spatial and temporal variation in the short-term and long-term settlement characteristics of waste in the simulated landfill cell. The settlement of waste predicted by the model could capture the key mechanisms of short- and long-term waste settlement in landfills. The leachate injection in BIOR simulation enhanced the rate of depletion of the degradable solids resulting in a significant increase in the waste settlement. For the simulated landfill and waste conditions, the biodegradation-induced settlement contributed to more than 90% of the settlement of the waste in both CONV and BIOR simulations. The distribution of the injected leachate had a considerable influence on the settlement profiles observed within the waste.

Numerical modeling of coupled biochemical and thermal behavior of municipal solid waste in landfills

A coupled bio-thermal (BT) model is proposed and validated for the prediction of long-term biochemical and thermal behavior of municipal solid waste (MSW) in landfills. The biochemical and thermal behavior of the waste was modeled using a two-stage anaerobic degradation model and diffusive heat transport model, respectively. A temperature function that accounts for the inhibitory effect of non-optimum temperatures on the microbial growth was proposed to simulate the coupled effects of biochemical and thermal behavior of waste in landfills. Six numerical simulation cases representing conventional and bioreactor landfill conditions were performed on a typical full-scale landfill cell model to determine the spatial and temporal variation in the long-term biochemical and thermal characteristics of waste in landfills. The results from the numerical analyses show that incorporating the effect of temperature of waste in the modeling of biodegradation of waste in landfills plays a significant role in realistically predicting the long-term biochemical and thermal regime in MSW landfills. The proposed BT model captures the key trends in the landfill gas (LFG) production and waste temperatures typically observed in actual full-scale landfills. Elevated waste temperatures were predicted especially in the bioreactor landfill cases suggesting that rapid decomposition of waste induces high heat generation rates; however, the elevated temperatures were short-lived.

Short-chain chlorinated paraffins in soils indicate landfills as local sources in the Tibetan Plateau

Background contamination levels of contemporary persistent organic pollutants (POPs) may be elevated due to local discharges, and hence it is of high importance to assess and monitor them in alpine and Polar Regions. This study investigated the role of waste disposal in the Tibetan plateau as the local source of short-chain chlorinated paraffins (SCCPs). SCCPs were determined in soils from the urban landfill and rural dumpsites, with a concentration range of 56.8–1348 ng/g dw. The gradient descent of SCCP levels from Lhasa landfill to the surrounding soils with increasing distances suggested a significant SCCP release from waste disposal. The transport pattern was well fitted by the Boltzmann equation after normalization in terms of soil organic carbon contents. Compared to the landfill cells closed in early years, the recently closed cells contained higher concentrations but lower proportions of the short-chain congener groups, likely reflecting the SCCP use history in Tibet. In open-burning dumpsites, higher SCCP levels and dominance of lighter congener groups indicates that such crude waste treatment process might cause an extra release of volatile SCCPs. This study elucidates local SCCP inputs to the background environment, and demonstrates that both urbanization and badly-managed landfill have been contributing to the presence of contemporary POPs in the Tibetan Plateau.

Management of the biodegradable fraction of residual waste by bioreactor landfill.

The performances of an integrated system based on mechanical biological treatment and bioreactor landfill with leachate recirculation for managing the mixed municipal solid waste generated in a given Italian district were investigated. In the mechanical biological treatment the municipal solid waste was mechanically sorted into two main streams: a dry and a mechanically sorted organic fraction consisting of 45,000 tonnes year-1. After being sorted the mechanically sorted organic fraction was aerobically pretreated before being disposed of in the 450,000 m3 bioreactor landfill. Experimental runs showed that an aerobic pretreatment period ranging from 15 to 30 days was able to maximize the methane generated by the mechanically sorted organic fraction once landfilled up to 10 Nm3 tonne-1. The aerobic pretreatment leads to a significant volatile solids reduction in the first 30 days, after which the volatile solids concentration remained quite constant. Similarly the potential dynamic respirometer index was significantly reduced in the first 15 days of the aerobic pretreatment decreasing from about 5,000 to about 3,500 mgO2kgVS-1h-1. The whole amount of electrical energy producible by the landfill ranged from 18.5 kWh tonne-1 to 21 kWh tonne-1, depending on the strategies adopted for the activation in bioreactor mode of each landfill cell by the leachate recirculation.

Characterization of Florida, U.S. landfills with elevated temperatures

The occurrence of elevated temperatures within landfills is a challenging issue for landfill operators to detect and correct. Little is known regarding the causes of elevated temperatures (ETs) or the number of landfills currently operating under such conditions. Therefore, the goal of this research was to determine which landfills within Florida have been impacted by ETs, and to develop a more complete understanding of the factors that may lead to these landfills becoming elevated temperature landfills (ETLFs). Historical landfill gas wellhead data, waste deposition reports, and landfill site geometry were collected for 27 landfill cells through the Florida Department of Environmental Protection electronic document management system, OCULUS database and from landfill operators and owners. These data were evaluated to quantify the characteristics that result in landfills having ‘elevated’ temperatures. Gas data included landfill gas temperatures and methane, carbon dioxide, and balance gas content. Furthermore, landfill maps were created in ArcGIS to observe spatial distribution of ETs in landfills over time. Upon analysis of the landfill gas wellhead data, it was discovered that 74% of studied landfill cells had ET readings; regulatory limits specify a maximum allowable gas temperature of 55 °C (131 °F). It was discovered that 37% of landfill cells contained MSW ash; of these cells, 90% of them are considered ETLFs. ETLF cells are on-average double the site area and approximately 6 m deeper than the average non-ETLF cell. Furthermore, results suggest that heat propagation in most landfills is limited; however, heat propagation is possible if gas wells are turned off for an extended time period.

Scaling up laboratory column testing results to predict coupled methane generation and biological settlement in full-scale municipal solid waste landfills

Prediction of methane (CH4) generation and settlement of biodegrading municipal solid waste (MSW) is of primary interest to landfills aiming at biogas recovery for energy generation and MSW stabilization. We investigate these two concurring processes using datasets from 35 laboratory column tests and 8 pilot- and full-scale landfill cells available in the literature. We fit the datasets using three CH4 generation models, i.e., conventional first-order decay (FOD) model, coupled FOD model, and coupled Gompertz model. The latter two models are proposed in this study which couple CH4 generation with biological settlement strain (εB) instead of elapsed time. Each model requires only four to five input parameters which can be reasonably estimated a priori based on the initial conditions of the MSW and landfills. The performances of the models are compared using jackknife resampling approach and normalized root-mean-square error (NRMSE) values. The coupled Gompertz model results in on average 50% lower NRMSE when predicting the time-dependent CH4 generation in all the datasets compared to the other two models. Thus, we demonstrate that CH4 generation from biodegrading MSW in landfills can be better predicted using the corresponding εB than the elapsed time.

Population dynamics of microbial species under high and low ammonia nitrogen in the alternate layer bioreactor landfill (ALBL) approach

Anaerobic landfill process is still believed to be a complex ecosystem due to the lack of knowledge on the functional activities of microbial species. This research sought to introduce a novel landfill bioreactor, named here as the alternate layer bioreactor landfill (ALBL) of fresh MSW (FW) and stabilized waste (CT) to avoid inhibitory conditions for the microbial species in anaerobic landfill. The stabilized waste layer in the bottom of landfill cell significantly changed microbial ecology of fresh MSW which in turn reduced the concentrations of NH4-N (29–31%) and VFAs (33–38%) in the ALBL approach, compared to fresh MSW disposal in sanitary landfill. The reduction of NH4-N favored early onset of methanogenesis within 6 weeks and methane (CH4) content of landfill gas increased from 11% to 40–50% (v/v), owing to the coexistence of Methanosarcinales (36–50%) and Methanomicrobiales (26–28%) archaea. The acetoclastic methanogenesis was achieved by reducing NH4-N toxicity in the ALBL.

Evolution properties and dechlorination capacities of particulate organic matter from a landfill

Particulate organic matter (POM) includes humin and non-degradable residues, and the knowledge about its composition, evolution and environmental behavior is limited. The composition, evolution and its influence on dechlorination of the POM in landfill was studied. The results show that POM accounts for 27 %–57 % of the organic matter in landfill cell, which is mainly composed of protein-, fulvic- and humic-like components. Firmicutes and Proteobacteria were the main microorganisms driving the compositional evolution of POM during the landfilling process. The electron acceptance capacities (EAC) and electron donating capacities (EDC) of POM were in the range of 0.05–0.51 μmol/gC−1 and 0.13–0.66 μmol/gC−1, respectively, and the average EAC and EDC of POM in the intermediate and old stage of landfill were higher than those in the initial stage. The combined action of MR-1 and POM increased the degradation rate of PCP by 20 %–40 %, which was ascribed to the reduction capacities and electron transfer process of POM. POM derived from the intermediate and old stages promoted PCP dechlorination more effectively when compared with the initial stage due to its high electron transfer capacities (ETC), which are of great significance for soil in-situ bioremediation.

Failure of an unfilled landfill cell due to an adjacent steep slope and a high groundwater level: A case study

Stability is a factor of vital importance for landfills, during both construction and operation. Slope failures are likely to occur in landfills located in regions with soft soils and a high groundwater table. In this study, the failure of an unfilled landfill cell, located in a typical coastal soft soil area, was explored. The failure was found to be caused by the instability of a continuous slope formed by the unfilled landfill cell and an adjacent construction waste landfill. A series of post-failure field investigations were performed, including cone penetration tests, monitoring of horizontal displacement of the sliding body, and an investigation of the groundwater. Additionally, finite element modeling and limit equilibrium analysis were applied to study the failure mechanism and the factor of safety (FOS), respectively. Both the field investigations and the theoretical analyses indicated that the geometrical configuration and the soft substratum provided the basis for the formation of the sliding surface, while a rise of the groundwater level due to continuous rainfall and poor drainage condition triggered the failure. This case reveals that the stability of landfills in regions with soft soils should be thoroughly assessed, and that appropriate ground treatment is necessary to avoid potential sliding along soft substrata. Furthermore, special attention should be paid to determination of the safe distances to surrounding earth structures, considering the effect of any ground treatment applied.

Fugitive methane emissions through the cover system of a Brazilian landfill cell

This paper evaluates the fugitive emissions of methane through a compacted soil cover layer in a cell of the Metropolitan Center Sanitary Landfill, in Salvador, Bahia, Brazil. Static-flow chamber tests were carried out in cracked and non-cracked soil areas in periods of high and low rainfall. Correlation coefficients between fugitive emissions and variables such as precipitation, moisture content and distance from drains, among others, were tested, and empirical equations are proposed for the estimation of fugitive emissions in both areas. Non-linear multiple regressions were able to fit the experimental results. However, a large number of independent variables were required. The fugitive methane emissions ranged from 0 to 356 (g/m2)/d. During the rainy season, points located in cracked areas showed an increase in emissions, with cracks in the soil acting as preferential flow paths. The opposite occurred in areas with few fissures and cracks. Considering the field biogas recovery rate, fugitive methane emissions accounted for, on average, 12% of the methane produced in the area in the period of analysis.

Intermediate covering of municipal solid waste landfills with alkaline grits, dregs and lime mud by-products of kraft pulp production

The increasing demand for intermediate covering materials in municipal solid waste landfills stimulates studies for finding alternative materials for this purpose. This study evaluates the use of dregs and grits and of lime mud generated in kraft pulp mills in considerably large volumes as covering materials in municipal solid waste landfills. Emphasis was given to the generated leachate quality and effects on the microbiological activities within the landfill cells. Three experimental units simulating landfill cells, 3 m high and 1 m in diameter, were assembled and monitored during 6 months. Unit 1 (U1) was filled with municipal solid waste (MSW), and a mixture of dregs and grits in a proportion of 70% and 30%, respectively, was used as covering material. Unit 2 (U2) used lime mud as covering material, and Unit 3 (U3) was filled solely with MSW without any covering material, as a control. The concentration of the leachate’s Chemical Oxygen Demand (COD) decreased by 91% and 92%, respectively, for U2 and U3: a decrease was not observed for U1, which remained above 30,000 mg/L, until the end of the six-month monitoring interval. Nine months after this interval, the COD decrease for U1, U2 and U3 was 92%, 98% and 97%, respectively. The metal concentrations in the leachates of the three experimental units were below the legal limits for discharge into watercourses in Brazil. The substitution of soil by the mixtures of dregs and grits and lime mud proved to be technically feasible, but the concentration of sodium in the leachate produced in Unit U1 (12,480 mg/L) was 13 times higher than U3 (control unit) and should be taken into consideration. This fact may have caused inhibition of the bioactivity in the cell and thus delayed the degradation of organic matter.

Use of electrical resistivity tomography for detecting the distribution of leachate and gas in a large-scale MSW landfill cell.

In this study, integrate electrical resistivity tomography (ERT) tests were carried out in a large-scale (5.0 × 4.0 × 7.5m) MSW landfill cell to investigate the possibility of detecting perched leachate mounds, leachate level, and gas accumulation zones at wet landfills. The resistivity of both bulk waste and waste components at different moisture states were measured and the three-phase volumetric relationships of the waste pile were analyzed to better interpret the ERT test results in the large-scale cell. The following observations were given: (1) The relationship between resistivity and volumetric moisture content (VMC) of waste sample can be reasonably fitted by Archie's law. The resistivity of waste components at a saturated state was all lower than 21Ωm. (2) A significant amount of void gas was entrapped in the underwater waste, being 30.4-34.8% of the whole waste pile in volume. (3) Low-resistivity zones (< 5.0Ωm) were observed in the waste pile being fully drained under a gravity condition, which was believed to be related to a perched leachate. (4) The average VMC values of the waste layer below and above the leachate level were in the ranges of 46.5-53.1% and 28.1-41.3%, respectively. (5) Irregular variations of high-resistivity zones (> 40Ωm) observed in the underwater waste were associated with the accumulation and dissipation of gas pressure. It was found that the "gas-breaking value" in the gas accumulation zone was up to 10.5kPa greater than the pore liquid pressure in the stable methanogenesis stage. These findings shone a light on the possibility of using the ERT method as an efficient tool for mapping the gas/leachate distribution and improving operations at wet landfills.

Evaluation of toxic potential of leachate originating from experimental landfill cells containing household waste and healthcare waste.

Two experimental cells with household solid waste and healthcare solid waste were monitored in order to evaluate the pollution potential, and its toxicity effects corresponding to the chemical substances present in the leachates generated, correlating the physico-chemical composition with the ecotoxicity results (organisms Aliivibrio fischeri and Danio rerio). From the statistical evaluation of the physico-chemical analysis results, leachate generated in the household solid waste cell presented greater or equal values than to the healthcare solid waste cell, except for the turbidity parameter. The ecotoxicity results showed the same behaviour as that obtained with the physico-chemical analysis. A significant positive correlation was verified between chemical oxygen demand, alkalinity and ammonia nitrogen parameters with the leachate toxicity. This study concluded that healthcare solid waste presented less or equal polluting potential compared with household solid waste, and the co-disposal can be considered a viable alternative in sanitary landfills.

N-Heterocyclic Carbenes in Organocatalysis

Stability is a factor of vital importance for landfills, during both construction and operation. Slope failures are likely to occur in landfills located in regions with soft soils and a high groundwater table. In this study, the failure of an unfilled landfill cell, located in a typical coastal soft soil area, was explored. The failure was found to be caused by the instability of a continuous slope formed by the unfilled landfill cell and an adjacent construction waste landfill. A series of post-failure field investigations were performed, including cone penetration tests, monitoring of horizontal displacement of the sliding body, and an investigation of the groundwater. Additionally, finite element modeling and limit equilibrium analysis were applied to study the failure mechanism and the factor of safety (FOS), respectively. Both the field investigations and the theoretical analyses indicated that the geometrical configuration and the soft substratum provided the basis for the formation of the sliding surface, while a rise of the groundwater level due to continuous rainfall and poor drainage condition triggered the failure. This case reveals that the stability of landfills in regions with soft soils should be thoroughly assessed, and that appropriate ground treatment is necessary to avoid potential sliding along soft substrata. Furthermore, special attention should be paid to determination of the safe distances to surrounding earth structures, considering the effect of any ground treatment applied.

FUGITIVE METHANE EMISSIONS FROM TWO EXPERIMENTAL BIOCOVERS CONSTRUCTED WITH TROPICAL RESIDUAL SOILS: FIELD STUDY USING A LARGE FLUX CHAMBER

This study aimed at assessing the response of two experimental passive methane oxidation biocovers (PMOB) installed in a Brazilian landfill located in Guarapuava, State of Parana. The PMOBs covered an area of 18 m² each, and were 0.70-m-thick. The first PMOB (control subarea) was constructed using the same soil used to cover closed landfill cells, i.e. a typical residual soil. The second PMOB (enriched subarea) was constructed with a mixture of the residual soil and mature compost, with a resulting organic matter content equal to 4.5%. CH4 and CO2 surface fluxes were measured in a relatively large (4.5 m²) static chamber. CH4, CO2 and O2 concentrations were also measured at different depths (0.10, 0.20, 0.25 and 0.30 m) within PMOBs. The concentrations from the raw biogas were also measured. Methane oxidation efficiencies (Effox) were estimated based on the CO2/CH4 ratio. The average CH4 and CO2 concentrations in the raw biogas (42% and 32%, respectively) for the 16 campaigns corroborated those typically found in Brazilian landfills. Lower CH4 fluxes were obtained within the enriched subarea (average of 20 g.m-2.d-1), while the fluxes in the control subarea averaged 34 g.m-2.d-1. Effox values averaged 42% for the control subarea and 80% for the enriched one. The results indicate that there is a great potential to reduce landfill gas (LFG) emissions by using passive methane oxidation biosystems composed of enriched substrates (with a higher content of organic matter).