Elevated temperatures in waste containment facilities

temperature;Landfill;combustion;pyrolysis;methane;biodegradation

Jafari, Navid H

关键词: temperature;    Landfill;    combustion;    pyrolysis;    methane;    biodegradation;   

Others  :  https://www.ideals.illinois.edu/bitstream/handle/2142/88158/JAFARI-DISSERTATION-2015.pdf?sequence=1&isAllowed=y

美国|英语

来源: The Illinois Digital Environment for Access to Learning and Scholarship

【 摘 要 】

Municipal solid waste (MSW), construction demolition debris (CDD), industrial byproducts, and many other wastes are landfilled in waste containment facilities. A number of factors can lead to elevated temperatures and thus present a hazard to the public health and safety. For instance, MSW landfills can produce obnoxious odors, toxic gases, and aggressive leachates. In addition, they can damage gas extraction, leachate collection, interim cover, and composite liner systems. These events can result in expensive remediation and warrant the permanent closure of the facility. The main objectives of this research are to: (1) identify causes and frequency of elevated temperatures; (2) develop a reactivity test for hazardous classification of aluminum production waste (APW); (3) develop an experiment to characterize gas generation and composition of APW; (4) identify progression of indicators for elevated temperatures in MSW landfills; (5) propose a classification system for landfill operators to assess the location and movement of elevated temperatures; and (6) evaluate the impact of elevated temperatures to high density polyethylene (HDPE) geomembrane service life.MSW landfills with a gas collection and control system used to comply with federal regulations (40 CFR, Part 60, Subpart WWW) operate each gas extraction well with a landfill gas temperature less than 55°C (131°F) because methane production from mesophilic bacteria starts to significantly decrease if the temperature of the waste mass exceeds 55°C (Kasali and Senior 1989; Hartz et al. 1982). At temperatures beyond 64°C, Ahring et al. (1995) report that thermophilic methanogens are inhibited and methane production slows or ceases. Therefore, in this thesis waste temperatures above 65°C is considered to be elevated because anaerobic decomposition has been curtailed. Several factors can lead to elevated landfill temperatures, including aerobic decomposition, self-heating, partially extinguished surface fires, exothermic chemical reactions, and spontaneous combustion. Although the leading mechanism of elevated temperatures is air ingress, landfills are also experiencing elevated temperatures due to exothermic reactions from APW. Because aluminum production waste does not meet hazardous waste classification criteria, they are commonly disposed in MSW landfills. As a result, a novel bench-scale calorimeter is developed and calibrated to measure potential temperature escalation. The calorimeter experiments at varying sodium hydroxide (NaOH) strengths show temperatures can rise to 100°C. For a landfill operator, the optimal concentration of NaOH was determined to be 1 M to 2 M NaOH because it provides sufficient alkalinity to react the metallic aluminum and fulfill the objectives of a rapid procedure to evaluate the reactivity criterion for hazardous waste classification. A gas generation test is developed and calibrated to evaluate hydrogen production and ammonia emissions from this waste stream. In addition, guidelines are provided for the disposal of APW in waste containment facilities. Whether aluminum wastes, air ingress, or other mechanisms lead to elevated temperatures, these events start in a localized area and over time can expand and consume entire landfill facilities. A case study is used to consolidate changes in landfill behavior into an ordered sequence (referred herein as progression of indicators) to permit landfill operators and first responders to detect and identify the location of elevated temperatures. Expanding on the progression of indicators, two case histories are used to develop methods to illustrate spatial and temporal changes in landfill behavior. In particular, the first case study illustrates spatial movements with gas wellhead temperature, ratio of methane to carbon dioxide, and settlement, while the second case study demonstrates subsurface temperature migration. These two case studies along with the progression of indicators are used to classify MSW landfills into five zones: anaerobic biodegradation, gas front, heating front, smoldering front, and combustion/pyrolysis zone. In addition, elevated temperatures can negatively impact engineered components in composite bottom liners, cover systems, leachate collection, and gas extraction and recovery systems. A case study is used to investigate the effect of elevated temperatures on HDPE geomembrane service life. When peak temperatures reach 60°C to 80°C, the geomembrane service life can be reduced to decades for the conditions examined and thus raises concerns regarding the integrity of the geomembrane at high temperatures.