Graduation Semester and Year

2013

Language

English

Document Type

Thesis

Degree Name

Master of Science in Civil Engineering

Department

Civil Engineering

First Advisor

Sahadat Hossain

Abstract

Municipal solid waste (MSW) is made up of household and commercial waste. Total MSW generated in USA in 2009 was 243 million tons and 54.3% of this waste generation was landfilled (EPA, 2009). MSW buried in landfills contribute a significant amount of gas (Landfill Gas or LFG) to atmosphere. The landfilled MSW is the third largest methane contributor to the atmosphere.One way to manage the LFG is the concept of bioreactor landfills. A bioreactor landfill is a controlled landfill where liquid and gas conditions are actively managed in order to accelerate or enhance biostabilization of MSW. Biostabilization of MSW is usually enhanced by leachate recirculation through MSW. Leachate recirculation can be implemented using different techniques. Using vertical wells, which is the topic of this study, is one way to recirculate leachate in a landfill.Vertical wells are more common in retrofit landfills that implementation of horizontal trenches are not possible or economical. The leachate recirculation system can contain a bunch of single wells, or a bunch of well clusters. In this study, the performance of both single and cluster arrangement was studied.The main objective of this study was to model the leachate recirculation using vertical wells in order to predict the wetted area around the well. HYDRUS-2D was used to create finite element models that simulate the field condition. The area of interest in this study was the Cefe Valenzuela landfill in Corpus Christi, TX. Currently, the landfill is permitted by Texas Commission on Environmental Quality (TCEQ) to operate as Enhanced Leachate Recirculation (ELR) landfill. The preliminary design details of vertical wells have been used in this study. However, an extensive experimental program carried out to characterize the MSW.The experimental program showed the fresh or partially degraded state of MSW. However, in some locations such as 40 ft of BH-1 and BH-2 the MSW is mostly degraded. Based on the laboratory test results two set of material properties, one representing the fresh or partially degraded state and another representing the mostly degraded state, were developed and assigned as MSW properties.Numerical simulations were performed using various leachate quantity and anisotropy factors. Longer lateral extent of leachate distribution is achieved when higher leachate quantity is injected or more anisotropic factor is assumed. Also, the lateral extent was higher in the mostly degraded MSW. In fresh or partially degraded MSW, the affected zone profile is oval shape with the well at top; however, for mostly degraded MSW it is more circular with the well at center. Leachate injection using a well cluster also was simulated to predict the group behavior of vertical wells. Cluster of two wells was found an efficient arrangement that affects a large area; however, cluster of three wells was not efficient because of the short space below the lowest well. Finally, simulations were validated based on the City of Denton Landfill. Simulations were performed for the City of Denton using same approach for this study. The simulation results were matching with the available electrical resistivity images of the recirculated area.

Disciplines

Civil and Environmental Engineering | Civil Engineering | Engineering

Comments

Degree granted by The University of Texas at Arlington

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