Facultative Bioreactor Landfill: An Environmental and Geotechnical Study

A relatively new concept of Municipal Solid Waste treatment is known as bioreactor landfill technology. Bioreactor landfills are sanitary landfills that use microbiological processes purposefully to transform and stabilize the biodegradable organic waste constituents in a shorter period of time. One of the most popular types of bioreactor landfills is the landfill with leachate recirculation. However, it is observed that ammonia rapidly accumulates in landfills that recirculate leachate and may be the component that limits the potential to discharge excess leachate to the environment. In the facultative landfill, leachate is nitrified biologically using an on-site treatment plant and converted by denitrifying bacteria to nitrogen gas, a harmless end-product. In this research, three pilot-plant scale lysimeters are used in a comparative evaluation of the effect of recirculating treated and untreated leachate on waste stabilization rates. The three lysimeters are filled with waste prepared with identical composition. One is being operated as a facultative bioreactor landfill with external leachate pre-treatment prior to recirculation, the second is being operated as an anaerobic bioreactor landfill with straight raw leachate recirculation, and the third one is the control unit and operated as a conventional landfill. Apart from environmental restrictions, geotechnical constraints are also imposed on new sanitary landfills. The scarcity of new potential disposal areas imposes higher and higher landfills, in order to utilize the maximum capacity ofthose areas. In this context, the knowledge of the compressibility of waste landfills represents a powerful tool to search for alternatives for optimization of disposal areas and new solid waste disposal technologies. This dissertation deals with and discusses the environmental and geotechnical aspects of municipal solid waste landfills. In the Environmental Engineering area, it compares the quality of the leachate and gas generated in the three lysimeters and discusses the transfer of the technology studied through lysimeters to procedures for full-scale operation. In the geotechnical area, this dissertation discusses the compressibility properties of the waste and provides a state-of-the-art review of MSW compressibility studies. It also evaluates the compressibility of MSW landfills for immediate and long-term settlements and proposes a new model for compressibility of waste landfills

Facultative Bioreactor Landfill: An Environmental and Geotechnical Study

A relatively new concept of Municipal Solid Waste treatment is known as bioreactor landfill technology. Bioreactor landfills are sanitary landfills that use microbiological processes purposefully to transform and stabilize the biodegradable organic waste constituents in a shorter period of time. One of the most popular types of bioreactor landfills is the landfill with leachate recirculation. However, it is observed that ammonia rapidly accumulates in landfills that recirculate leachate and may be the component that limits the potential to discharge excess leachate to the environment. In the facultative landfill, leachate is nitrified biologically using an on-site treatment plant and converted by denitrifying bacteria to nitrogen gas, a harmless end-product. In this research, three pilot-plant scale lysimeters are used in a comparative evaluation of the effect of recirculating treated and untreated leachate on waste stabilization rates. The three lysimeters are filled with waste prepared with identical composition. One is being operated as a facultative bioreactor landfill with external leachate pre-treatment prior to recirculation, the second is being operated as an anaerobic bioreactor landfill with straight raw leachate recirculation, and the third one is the control unit and operated as a conventional landfill. Apart from environmental restrictions, geotechnical constraints are also imposed on new sanitary landfills. The scarcity of new potential disposal areas imposes higher and higher landfills, in order to utilize the maximum capacity ofthose areas. In this context, the knowledge of the compressibility of waste landfills represents a powerful tool to search for alternatives for optimization of disposal areas and new solid waste disposal technologies. This dissertation deals with and discusses the environmental and geotechnical aspects of municipal solid waste landfills. In the Environmental Engineering area, it compares the quality of the leachate and gas generated in the three lysimeters and discusses the transfer of the technology studied through lysimeters to procedures for full-scale operation. In the geotechnical area, this dissertation discusses the compressibility properties of the waste and provides a state-of-the-art review of MSW compressibility studies. It also evaluates the compressibility of MSW landfills for immediate and long-term settlements and proposes a new model for compressibility of waste landfills

Use of leaching tests to characterize landfill leachate in the long term period. Apllication in risk analysis

In this experimental work leaching tests on waste coming from two old uncontrolled landfill, simulating aerobic and anaerobic landfill operations. The results allowed a comparison between the two operating conditions, confirming the positive effects of aeration on leachate quality, the not well defined behavior of metals and enhancing the importanc

Experimental Assessment of Coupled Physical-Biochemical-Mechanical-Hydraulic Processes of Municipal Solid Waste Undergoing Biodegradation.

Proper management and disposal of municipal solid waste (MSW) remains an unresolved global problem. One solution to handle existing and future MSW is to move away from modern landfills that focus on containment and move towards bioreactor landfills that promote MSW biodegradation and enhance methane (CH4) generation and its collection as an alternative energy source. Solid, liquid and gas phases of MSW coexist in different proportions within a landfill, and evolve with time due to concurring and coupled physical-biochemical-mechanical-hydraulic processes during MSW biodegradation. A fundamental understanding of the concurring processes is needed to design, monitor, and operate bioreactor landfills effectively and efficiently. Seven large-size (d=300 mm; h=600 mm) laboratory landfill simulators were developed to degrade unprocessed MSW of variable waste composition that is representative of the MSW in a mega-scale landfill. The simulators were operated and monitored for up to four years to assess the evolution of the physical, mechanical, and hydraulic properties of MSW, the evolution of the biochemical characteristics of generated leachate and biogas, and population dynamics of MSW-degrading microorganisms. The coupled processes were found to be systematic, correlated to each other, and dependent on initial waste composition. Testing of MSW in fresh and fully-degraded (retrieved from laboratory simulators) states was performed to assess the physical and mechanical properties of MSW using a unique 300-mm diameter simple shear apparatus. The shear strength and compressibility of MSW changed due to biodegradation and was a function of the initial waste composition and the biodegradation state. A relationship between the shear strength and shear-wave velocity of MSW was established for fresh and degraded MSW. Laboratory results on CH4 generation and settlement of MSW during biodegradation generated as part of this study were supplemented by an extensive database synthesized from the literature that includes laboratory results and field measurements from numerous landfills. The database was analyzed to quantify the influence of moisture content of waste, overburden pressure, landfill monitoring and control, and temperature on MSW degradation. Based on the findings of this study, recommendations to promote MSW biodegradation include enhancing biodegradation conditions, optimizing initial waste composition, and increasing biogas collection efficiency.PHDEnvironmental EngineeringUniversity of Michigan, Horace H. Rackham School of Graduate Studieshttp://deepblue.lib.umich.edu/bitstream/2027.42/120798/1/xcfei_1.pd

Saturated hydraulic conductivity of municipal solid waste considering the influence of biodegradation

FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOMunicipal solid waste (MSW) permeability is influenced mainly by compaction, unit weight, overburden pressure, composition, and biodegradation of the waste. However, the variation of hydraulic conductivity with MSW biodegrading over time has not yet been14491449FAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULOFAPESP - FUNDAÇÃO DE AMPARO À PESQUISA DO ESTADO DE SÃO PAULO2010/18560-

Mechanics of biocell landfill settlements

Prediction of landfill gas generation and settlements are of concerns in design and maintenance of biocell landfills. Accurate settlement prediction is essential for design of piping systems used for the delivery of re-circulated leachate and recovery of landfill gas. Landfill settlement is the result of change in overburden stresses and biodegradation of waste. Biodegradation-induced settlement results from the re-arrangement of waste skeleton in response to the decomposition of waste mass. Current practice of landfill settlement modeling is predominantly empirical, thus most of the available techniques make no attempt to simulate the real mechanisms of waste settlement. Traditionally compressibility index is defined similar to that of clays, to explain the general settlement behavior of waste. Although a landfill is an interacting multiphase medium there is limited research to explain landfill gas generation and dissipation and moisture distribution as integral parts of the process of landfill settlements. This dissertation describes a model which couples settlements of a biocell landfill with the generation and dissipation of landfill gases and distribution of moisture. The major mechanisms of waste settlement were identified as mechanical compression and biodegradation-induced strain. Mechanical compression was modeled with the help of laboratory simulations. To model the biodegradation-induced settlement, it was assumed that waste degradation obeys the first order reaction kinetics. The mass balance of the landfill gas was used to link settlement with gas pressure. The Richards equation was used to simulate the distribution of moisture. A computer program was written to numerically predict the settlements, gas pressure and volumetric moisture content in a biocell landfill using landfill geometry and waste properties. In the absence of a complete set of data, settlement and gas pressure components of the model were validated using data from two different landfills. The model was then used to predict the settlement behavior of The City of Calgary Biocell Landfill. The model predicted higher strain values, when moisture as well as gas pressure were incorporated in to the simulation. Therefore, it was concluded that modeling settlement without taking gas pressure and moisture in to account, could underestimate the total settlement. The model was capable of predicting landfill density, and the density values predicted for twenty five years matched with those reported in literature

Treatment of Landfill Waste, Leachate and Landfill Gas: Modelling/Simulation and Experimental Studies

Landfilling has been relegated to containing waste and hoping for minimal environmental impact. However, landfills produce harmful leachate and landfill gas that require treatment. To speed up the landfill biodegradation process, aerating the landfill to promote aerobic biodegradation has been implemented successfully. However, the conversion from a traditional anaerobic landfill to an aerobic landfill is to this point, not well researched. A 3-dimensional dynamic mathematical model was developed that depicts the conversion of a landfill from an anaerobic to an aerobic operation. The results of the model (CO2 volume fraction and temperature), agreed with data from published work. The model solved for the liquid and gaseous pressures/velocities, gas composition, anaerobic/aerobic biomass concentrations and temperature; all were solved with respect to space and time. Landfill leachate requires treatment before release and landfill gas requires purification (removal of CO2) before it can be used as a fuel. A hybrid sorption (absorption and adsorption/ion exchange) system was developed to treat leachate and purify landfill gas in the same column. The absorption results showed that leachate could remove more carbon dioxide from the landfill gas than pure water, due to its slight basicity. The adsorption/ion exchange results showed that lead could be removed from model leachate but not below Ontario discharge guidelines with the length of the column used (50-55 cm zeolite bed height)

Carbon Mass balance in the first phase of a semiaerobic-Anaerobic-Aerated (S.An.A) landfill mode

Sono stati indagati gli effetti che una pre aerazione può avere su una fase anaerobica.In particolare, gli effetti che ha l'aerazione sui parametri che influenzano la digestione anaerobica, quali pH, VFA, alcalinità e ammoniaca.Sono stati messi a confronto due tipi di aerazione differenti e valutate le performance. E' stato implementato un bilancio del carbonio parzial