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Remediation of Typical Municipal Solid Waste Dumpsite in Bangalore City
... The leachate head increased marginally in this condition but is within the permissible limit. Recirculation of leachate enhances the waste degradation rate and Fig. 7 HELP model output for leachate collection and 50% recirculation (Reprinted from sughosh et al. [10]. With permission from ASCE) reduces the time required for stabilization of the waste. ...
... Schematic diagram of column experiment for methane oxidation in biocovers (Reprinted from sughosh et al.[10]. With permission from ASCE) ...
... Total landfill gas and methane gas emission from Landfill (Reprinted from sughosh et al.[10]. With permission from ASCE) Methane reduction potential with respect to depth (Reprinted from sughosh et al.[10]. ...
The current practices of containing the waste in dumpsite/landfill are considered as unsustainable due to their negative impact on the environment, society and economy. Remediation of the existing open dumpsite into bioreactor landfills helps in recovering the valuable land area at a faster rate due to the reduction in the time required for waste stabilization process. The problem of leachate treatment can also be addressed effectively during the remediation process. Therefore, remediating an existing dumpsite can be classified as an approach towards achieving the sustainability in landfilling practices. In this study, an approach for remediating an existing municipal solid waste (MSW) dumpsite in Bangalore city is presented by addressing the three major aspects, viz., landfill gas (LFG), leachate and the recovery of air space. Modelling tools are used to estimate the LFG emission and to design the leachate collection and recirculation systems. The methane oxidation potential of the digested MBT waste as a biocover material is evaluated using column experiments. The biocover systems are then designed to mitigate the LFG emissions from the dumpsite.
The study was aimed to improve the degradation of organic pollutants in municipal solid waste (MSW) through the bio-stimulation process. The results showed that the physico-chemical properties of MSW (control) had a high value of pH (9.2 ± 0.02); total suspended solids (TSS: 1547 ± 23 mg/kg⁻¹), and total dissolved solids (TDS:76 ± 0.67 mg/kg⁻¹). After the biostimulation process (biostimulated MSW), the physico-chemical parameters of MSW were reduced as pH (7.1 ± 0.01); TSS (41± 0.01 mg/kg⁻¹), and TDS (789 ± 03 mg/kg⁻¹). Furthermore, the major organic pollutants detected from MSW by gas chromatography-mass spectroscopy (GC-MS) analysis at different retention time (RT) were hexadecane (RT-8.79); pentadecane (RT-9.36); and hexasiloxane (RT-9.43) while these organic pollutants were degraded after the biostimulation process. The whole-genome metagenome sequencing size (%) analyses showed major groups of bacteria (40.82%) followed by fungi (0.05%), virus (0.0032%), and archaea (0.0442%) in MSW. The species richness and evenness of the microbial community were decreased substantially due to the biostimulation treatment. The total number of genes in the biostimulated MSW (PS-3_11267) sample were 465302 whereas the number of genes in the control MSW (PS-4_11268) sample was 256807. Furthermore, the biostimulated MSW (PS-3_11267) aligned the reads to bacteria (19502525), fungi (40030), virus (3339), and archaea (12759) genomes whereas the control sample (PS-4_11268) aligned the reads to bacteria (17057259), fungi (19148), virus (1335), and archaea (18447) genomes.
Moreover, the relative abundance at genus level in biostimulated MSW (PS-3_11267) (Ochrobactrum and Phenylobacterium), phylum; (Proteobacteria and Actinobacteria), and species (Chthoniobacter flavus and Vulgatibacter incomptus) level was the most abundant. The results provided valuable information regarding the degradation of organic pollutants in MSW by microbial communities through biostimulation for the prevention of soil pollution and health protection.
The design of a gas collection system (GCS) for a landfill involves estimating several critical parameters, such as the radius of influence (ROI), suction pressures, number of wells and their spacing. One of the biggest challenges lies in the estimation of ROI for a particular landfill. In this study, the ROI for a Bagalur landfill is estimated for various possible gas generation rates. ROI for active and passive GCS is estimated with numerical modelling (two-dimensional) for all definitions of ROI at different suction pressures. An inverse correlation was observed between the values of various definitions of ROI at different gas generation rates. Justification for this behaviour is brought out by addressing the conceptual difference between these definitions. The number of wells along with their spacing was then calculated, and the efficiency of the design was assessed with three-dimensional modelling. Passive and active systems had average methane recovery rates of 84% and 88%, respectively, with an atmospheric methane flux ranging from 10 ⁻⁹ to 10 ⁻¹⁰ kg m ⁻² s ⁻¹ . The high recovery rate and low methane flux indicate the effectiveness of the design. The values of the methane flow rate from the extraction well were validated with a theoretical method, suggesting the usability of the model for future investigations.
The sustainable landfilling concept has several advantages over conventional waste management practices in addressing various socio-economic and environmental concerns. This study presents an overview of the sustainable landfilling concept and various unit processes associated with it. The waste management approaches followed in the city of Bangalore and the benefits of applying the sustainable landfilling concept are discussed. A review of the bioreactor landfills, landfill mining, and biocover systems are presented. Laboratory scale bioreactor studies on the degradation of mechanically and biologically treated waste of Bangalore city under anaerobic, aerobic, and semi-aerobic conditions are presented. The performance of bioreactor landfills and the selection of waste treatment units are greatly influenced by the municipal solid waste properties and hence are reviewed in the study.
Bangalore generates around 3,500 tons of municipal solid waste (MSW) per day. The current waste management practices involve preliminary mechanical and biological treatment before landfilling. Assessment of the waste management practices followed by the municipality by using life cycle analysis (LCA) is presented in this study. LCA is also used in the study to explore alternatives to the current practices and handle the waste in a more sustainable way. The analysis is performed in terms of material flow, energy flow, and the impacts of waste processing on the environment. Five impact categories consisting of global warming, acidification, eutrophication, human toxicity, and aquatic ecotoxicity potentials were investigated. The result presents the comparison of open dumping of MSW (which was practiced earlier) with the existing integrated waste management (IWM) system. Results also show that the environmental impact of IWM system with a bioreactor landfill having an energy recovery facility is lesser than the above two cases.
Through this study are presented the results of a first test of leachate recirculation on landfill methane production in Guadeloupe archipelago (at the North of the Lesser Antilles, French West Indies, island tropical and humid climate). In French West Indies, methane produced by landfilling is commonly flared without energy recovery. In this paper, assessment is made of the potential for leachate recirculation to increase methane production for energetic purpose in a tropical area. This process could also rapidly reduce the volume of leachate to be treated. The results obtained here show that by injecting 5 m 3 of leachate in several draining leachate wells, a sharp increase in the proportion of methane in biogas is observed just a few days after. The older the waste is, the more efficient this process seems to be. In some parts of the waste dome, the methane proportion is nearly doubled at the biogas wellhead. In island context, leachate recirculation could be a long-term solution to produce energy assuming that the quantity of solid waste sent to landfill remains sufficient to maintain a viable operation of the waste dome, to reduce costs of leachate treatment and to create new space for waste storage.
Landfills are common land disposal methods employed in most of the developing countries across the world. The waste disposal methods, such as open dumps, landfill without and with gas recovery systems and bioreactor landfills, are assessed using the life-cycle analysis (LCA) method. These scenarios were applied to Bangalore (Karnataka, India). This method serves as a decision making tool for selecting the most sustainable, energy- and cost-efficient methods. The analysis is done in terms of the material flow, energy flow, and impacts of open dumping and land filling on the environment. The global warming potential was considered as the most important factor, as its impact on the environment is high. The life-cycle cost analysis (LCCA) is also done considering an average life of a landfill as 50 years. Cost analysis was done in terms of the initial fixed costs, yearly maintenance cost, and postclosure monitoring and maintenance cost. The revenue generated from trading power that could be generated from the landfills was also considered. The power that could be generated from the landfills was calculated as 11 MW. The bioreactor landfill could be used twice in 50 years when compared to the engineered landfill as the waste stabilization period varied from 10 years in bioreactor landfill to few decades in case of engineered landfills. Among the four scenarios, the bioreactor landfill had an edge over the other methods environmentally and economically, whereas the open dump scenario was the least favored option as the impacts caused to the environment was considerably huge.
The Outer Loop landfill bioreactor (OLLB) located in Louisville, KY, USA has been in operation since 2000 and represents an opportunity to evaluate long-term bioreactor monitoring data at a full-scale operational landfill. Three types of landfill units were studied including a Control cell, a new landfill area that had a piping network installed as waste was being placed to support leachate recirculation (As-Built cell), and a conventional landfill that was modified to allow for liquid recirculation (Retrofit cell). The objective of this study is to summarize the results of settlement data and assess how these data relate to solids decomposition monitoring at the OLLB. The Retrofit cells started to settle as soon as liquids were introduced. The cumulative settlement during the 8years of monitoring varied from 60 to 100cm. These results suggest that liquid recirculation in the Retrofit cells caused a 5-8% reduction in the thickness of the waste column. The average long-term settlement in the As-Built and Control Cells was about 37% and 19%, respectively. The modified compression index (Cα(')) was 0.17 for the Control cells and 0.2-0.48 for the As-Built cells. While the As-Built cells exhibited greater settlement than the Control cells, the data do not support biodegradation as the only explanation. The increased settlement in the As-Built bioreactor cell appeared to be associated with liquid movement and not with biodegradation because both chemical (biochemical methane potential) and physical (moisture content) indicators of decomposition were similar in the Control and As-Built cells. The solids data are consistent with the concept that bioreactor operations accelerate the rate of decomposition, but not necessarily the cumulative loss of anaerobically degradable solids.
Eleven statewide waste characterization studies were compared to assess variation in the quantity and composition of waste after separation of recyclable and compostable materials, i.e., discarded waste. These data were also used to assess the impact of varying composition on sequestered carbon and methane yield. Inconsistencies in the designation of waste component categories and definitions were the primary differences between study methodologies; however, sampling methodologies were consistent with recommended protocols. The average municipal solid waste MSW discard rate based on the statewide studies was 1.90 kg MSW person −1 day −1 , which was within the range of two national estimates: 2.35 and 1.46 kg MSW person −1 day −1 . Dominant components in MSW discards were similar between studies. Organics food waste, yard trimmings, paper, and plastic components averaged 23.6 4.9%, 28.5 6.5%, and 10.6 3.0% of discarded MSW, respectively. Construction and demolition C&D waste was 20.2 9.7% of total solid waste discards i.e., MSW plus C&D. Based on average statewide waste composition data, a carbon sequestration factor CSF for MSW of 0.13 kg C dry kg MSW −1 was calculated. For C&D waste, a CSF of 0.14 kg C dry kg C and D waste −1 was estimated. Ultimate methane yields L o of 59.1 and 63.9 m 3 CH 4 wet Mg refuse −1 were computed using EPA and state characterization study data, respectively, and were lower than AP-42 guidelines. Recycling, combustion, and other management practices at the local level could significantly impact CSF and L o estimates, which are sensitive to the relative fraction of organic components in discarded MSW and C&D waste.
The management of municipal solid waste has become an acute problem due to enhanced economic activities and rapid urbanisation. Increased attention has been given by the government in recent years to handle this problem in a safe and hygienic manner. In this regard, Municipal Solid Waste Management (MSWM) environmental audit has been carried out for Bangalore city through the collection of secondary data from government agencies, and interviews with stakeholders and field surveys. Field surveys were carried out in seven wards (representative samples of the city) to understand the practice and identify the lacunae. The MSWM audit that was carried out functional-element-wise in selected wards to understand the efficacy and shortfalls, if any, is discussed in this paper. Biographical notes: Ramachandra holds a BE (Electrical Engg) from Bangalore University, India and a PhD in Energy and Environment from the Indian Institute of Science. He has made significant contributions in the area of energy and environment. His areas of research include energy systems, environmental management, regional planning, spatial decision support systems, GIS and remote sensing. He teaches principles of remote sensing, digital image processing, renewable energy technologies, and natural resources management. He has published over 108 research papers as well as nine books. His latest book entitled Management of Municipal Solid Waste, 2006, has been published by Capital Publishers, New Delhi. He is a fellow of the Institution of Engineers (India) and Institution of Electrical Engineers (UK), senior member, IEEE (USA) and AEE (USA), and many similar institutions.
This study evaluated two biofilter designs to mitigate methane emissions from landfill vents. Water-spreading biofilters were designed to use the capillarity of coarse sand overlain by a finer sand to increase the active depth for methane oxidation. Compost biofilters consisted of 238-L barrels containing a 1:1 mixture (by volume) of compost to expanded polystyrene pellets. Two replicates of each type of biofilter were tested at an outdoor facility. Gas inflow consisted of an approximately 1:1 mixture (by volume) of CH4 and CO2. Methane output rates (J(out); g m(-2) day(-1)) were measured using the static chamber technique and the Pedersen et al. (2001) diffusion model. Methane oxidation rate (J(ox); g m(-2) day(-1)) and fraction of methane oxidized (f(ox)) were determined by mass balance. For methane inflow rates (J(in)) between 250 and 500 g m(-2) day(-1), the compost biofilter J(ox), 242 g m(-2) day(-1), was not significantly different (P = 0.0647) than the water-spreading biofilter J(ox), 203 g m(-2) day(-1); and the compost f(ox), 69%, was not significantly different (P = 0.7354) than water-spreading f(ox), 63%. The water-spreading biofilter was shown to generally perform as well as the compost biofilter, and it may be easier to implement at a landfill and require less maintenance.
The paper presents results of a comprehensive study on characterization of mechanically biologically treated waste generated in Bangalore, India. Physical, biochemical and engineering characteristics of the waste are presented. The methodology to separate the components of consolidation which includes primary, secondary and biodegradation strains is reviewed. A laboratory scale anaerobic bioreactor depicting the behaviour of the waste in a bioreactor landfill was studied for 370 days and the settlement, gas generation and leachate characteristics were monitored. Study on characterization of waste indicates an organic content of 54% and carbon, nitrogen and hydrogen in the range of 19.28, 1.64 and 11.07% respectively. Around 20–26% of settlement and 15 L of landfill gas/kg of dry waste was observed in laboratory scale bioreactor studies. Both laboratory and small scale bioreactor test results indicate that the MSW has high biodegradable content and biomethane potential. It is prone to large settlements and has shear strength parameters comparable to those published in literature. The behaviour of waste under given conditions can be understood from the above studies and the results provide valuable data necessary for designing MSW treatment scheme which includes waste to energy systems and bio reactor landfill with gas and leachate collection systems.
Landfill gas (LFG) contains high concentrations of methane, which contributes to the greenhouse effect. LFG also contains aromatic hydrocarbons and chlorinated aliphatics, which, by emission to ambient air, can be a local health threat. In addition, chlorinated aliphatics may also influence the earth’s ozone layer.
The objectives of the study were to investigate the degradation of LFG constituents in LFG-affected soils, and to evaluate the importance of the degradation processes to the emission.
High methane oxidation potentials were found in laboratory experiments at 25 °C. The degradation seemed to follow zero order reaction kinetics, and was 3-4 times slower at 10 °C than at 25 °C. High degradation rates for benzene and toluene were also observed. In soils sampled away from the landfill, where almost no LFG contamination had been observed, longer lag phases and lower degradation rates of the two aromatic hydrocarbons were observed.
Slow cometabolic degradation of trichloroethylene (TCE) and 1,1,1-trichloroethane (TCA) was observed when methane was present in the batch experiments. The rates were much lower than the rates for the aromatic hydrocarbons.
In the field at Skellingsted Landfill, Denmark, high methane emissions were observed in an area just outside the landfill area, probably as a result of the clay landfill covering, which has led to significant lateral migration of LFG. Indications of active methane oxidation in the field were observed by measuring soil gas profiles.
By comparison of the results obtained in the laboratory with the field results, it is shown that degradation processes may have a significant effect on the emission of all the compounds studied. However, the subject needs much more attention.
Leachate recirculation in municipal solid waste (MSW) landfills operated as bioreactors offers significant economical and environmental benefits. Subsurface leachate recirculation in MSW landfills is commonly achieved by using horizontal trenches or vertical wells. Currently, there are no design guidelines available for leachate recirculation using a subsurface leachate recirculation system (LRS). The key objective of this study is to prepare design guidelines for LRS consisting of horizontal trenches. This paper presents a numerical study of LRS consisting of horizontal trenches. The design parameters evaluated in this study include: (1) Leachate injection pressure head; (2) hydraulic conductivity of trench backfill and MSW; (3) dimensions of trench; and (4) spacing and geometric formation of trenches. The finite-element saturated/unsaturated flow model HYDRUS-2D was used for the numerical study. The hydraulic performance of the LRS was evaluated primarily using the simulated recirculated leachate flux and distribution of flow under steady-state flow condition. The key findings of this numerical study are: (1) Logarithm of leachate flux and leachate injection pressure head have a curvilinear relationship and leachate flux is directly proportional to the hydraulic conductivity of MSW; (2) if hydraulic conductivity of trench backfill is equal to or greater than that of MSW, any further increase in the hydraulic conductivity of the trench backfill has negligible impact on leachate flux; (3) for a given cross-sectional area, horizontal trenches having width greater than depth can recirculate greater leachate flux and can wet more area of the waste; and (4) reduction in the horizontal spacing between trenches and vertically staggering the trenches reduces "dry zones" between trenches where otherwise recirculated leachate may not reach.
Landfilling is one of the most common ways of municipal solid waste (MSW) disposal in developing countries. Air pollutants emitted from landfills contributes to the emission in the atmosphere of greenhouse gases and cause serious problems to the human health. Methane emission from landfill is serious environmental global concern as it accounts for approximately 15 percentages of current greenhouse gas emissions. The current study was focused on the determination of air emissions from the Akrotiri landfill site which is located at the Akrotiri area (Chania, Greece). The models used are the triangular model, the stoichiometric model and LandGEM model. These models are used to estimate the total landfill gas production from a given amount of waste. The models differ on their scientific approach for the quantification on emissions, their complexity and input data requirements. The LandGEM model was selected for the determination of more representative assessed landfill gas emission rates. The maximum biogas production rate by the LandGEM model was calculated to be 1.64× 10 3 Mg yr -1 and was observed during the year 2008 for the A phase of the landfill, while for the B phase the maximum biogas production rate was 2.70 × 10 3 Mg yr -1 and was observed during 2014.
A low-cost alternative approach to reduce landfill gas (LFG) emissions is to integrate compost into the landfill cover design in order to establish a biocover that is optimized for biological oxidation of methane (CH(4)). A laboratory and field investigation was performed to quantify respiration in an experimental compost biocover in terms of oxygen (O(2)) consumption and carbon dioxide (CO(2)) production and emission rates. O(2) consumption and CO(2) production rates were measured in batch and column experiments containing compost sampled from a landfill biowindow at Fakse landfill in Denmark. Column gas concentration profiles were compared to field measurements. Column studies simulating compost respiration in the biowindow showed average CO(2) production and O(2) consumption rates of 107 ± 14 gm(-2)d(-1) and 63 ± 12 gm(-2)d(-1), respectively. Gas profiles from the columns showed elevated CO(2) concentrations throughout the compost layer, and CO(2) concentrations exceeded 20% at a depth of 40 cm below the surface of the biowindow. Overall, the results showed that respiration of compost material placed in biowindows might generate significant CO(2) emissions. In landfill compost covers, methanotrophs carrying out CH(4) oxidation will compete for O(2) with other aerobic microorganisms. If the compost is not mature, a significant portion of the O(2) diffusing into the compost layer will be consumed by non-methanotrophs, thereby limiting CH(4) oxidation. The results of this study however also suggest that the consumption of O(2) in the compost due to aerobic respiration might increase over time as a result of the accumulation of biomass in the compost after prolonged exposure to CH(4).
Because effective operation of bioreactor landfills involves careful operation and construction of infrastructure beyond that necessary in traditional landfills, upfront capital and operating costs are greater than those associated with traditional landfills. Prior to investing in bioreactor landfills, landfill owners must be convinced that larger short-term expenses (e.g., liquid and/or air injection infrastructure) will be balanced by future economic benefits (e.g., extension of landfill life, reduced leachate treatment costs, etc.). The purpose of this paper is to describe an economic model developed to evaluate the impact of various operational (anaerobic, aerobic, or hybrid) and construction (retrofit and as-built) bioreactor landfill strategies on project economics. Model results indicate retrofit bioreactor landfills are more expensive than traditional landfills, while both the as-built and aerobic bioreactor landfills are less costly. Simulation results indicate the parameters that influence bioreactor economics most significantly are airspace recovery, gas recovery and subsequent use to generate electricity, and savings resulting from reduced leachate treatment costs.
Between 1977 and 2005 six large-scale failures of municipal solid waste dumps and landfills have been recorded in the technical literature. The volumes of waste mobilized in the failures varied from 10-12 000 m(3) in a failure that killed nearly 300 people to 1.5 million m(3) in a failure that caused no deaths or injuries. Of the six failures, four occurred in dumps that, as far as is known, had not been subjected to any prior technical investigation of their shear stability. The remaining two failures occurred in engineer-designed landfills, one of which practised leachate recirculation, and the other co-disposed of liquid waste along with solid waste. The paper reviews, describes and analyses the failures and summarizes their causes.
The methane oxidation potential of several types of compost methanotrophic biofilter columns were compared in the laboratory over a period of 220 days. The results indicate an increase in methanotrophic activity over a period of about 100 days, up to a maximum of 400 g m(-2) day(-1), and a gradual decline to about 100 g m(-2) day(-1) within the next 120 days. High methane oxidation rates appear to be restricted to a small area of the column, 10-15 cm thick. Based on the laboratory investigations carried out to determine the cause for the decline in methane oxidation rate, it was concluded that the formation of exopolymeric substances (EPS), at the zones of maximum methane oxidation, was responsible for this decline. In monitoring methane oxidation in a column for up to 600 days, it was observed that mixing of the medium after formation of EPS enabled the column to temporarily recover high performance. The results suggest that stable, homogenous compost, with a low C/N and low ammonium content, mixed on a regular basis, could achieve and maintain high methane oxidation efficiencies.
In the long-term, landfills are producing landfill gas (LFG) with low calorific values. Therefore, the utilization of LFG in combined heat and power plants (CHP) is limited to a certain period of time. A feasible method for LFG treatment is microbial CH(4) oxidation. Different materials were tested in actively aerated lab-scale bio-filter systems with a volume of 0.167 m(3). The required oxygen for the microbial CH(4) oxidation was provided through perforated probes, which distributed ambient air into the filter material. Three air input levels were installed along the height of the filter, each of them adjusted to a particular flow rate. During the tests, stable degradation rates of around 28 g/(m(3) h) in a fine-grained compost material were observed at a CH(4) inlet concentration of 30% over a period of 148 days. Compared with passive (not aerated) tests, the CH(4) oxidation rate increased by a factor of 5.5. Therefore, the enhancement of active aeration on the microbial CH(4) oxidation was confirmed. At a O(2)/CH(4) ratio of 2.5, nearly 100% of the CH(4) load was decomposed. By lowering the ratio from 2.5 to 2, the efficiency fell to values from 88% to 92%. By varying the distribution to the three air input levels, the CH(4) oxidation process was spread more evenly over the filter volume.
Landfill gases produced during biological degradation of buried organic wastes include methane, which when released to the atmosphere, can contribute to global climate change. Increasing use of gas collection systems has reduced the risk of escaping methane emissions entering the atmosphere, but gas capture is not 100% efficient, and further, there are still many instances when gas collection systems are not used. Biotic methane mitigation systems exploit the propensity of some naturally occurring bacteria to oxidize methane. By providing optimum conditions for microbial habitation and efficiently routing landfill gases to where they are cultivated, a number of bio-based systems, such as interim or long-term biocovers, passively or actively vented biofilters, biowindows and daily-used biotarps, have been developed that can alone, or with gas collection, mitigate landfill methane emissions. This paper reviews the science that guides bio-based designs; summarizes experiences with the diverse natural or engineered substrates used in such systems; describes some of the studies and field trials being used to evaluate them; and discusses how they can be used for better landfill operation, capping, and aftercare.