The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion
<p> The performance and stability of a thermophilic anaerobic digestion system are inherently dependent on the engineered environment within each reactor. While the selection of operational parameters such as mixing, solids retention time, and digestion temperature are often selected on the ba...
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ndltd-VTETD-oai-vtechworks.lib.vt.edu-10919-357712020-09-29T05:41:47Z The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion Wilson, Christopher Allen Environmental Engineering Novak, John T. Love, Nancy G. Boardman, Gregory D. methanogenesis thermophilic anaerobic digestion biosolids odors <p> The performance and stability of a thermophilic anaerobic digestion system are inherently dependent on the engineered environment within each reactor. While the selection of operational parameters such as mixing, solids retention time, and digestion temperature are often selected on the basis of certain desirable outcomes such as the deactivation of human pathogens, these parameters have been shown to have a broad impact on the overall sludge digestion process. Since the current time-temperature requirements for biosolids pathogen reduction are most easily met at elevated digestion temperatures within the thermophilic range, it is certainly worth examining the effect of specific digestion temperatures on ancillary factors such as operational stability and the aesthetic quality of biosolids. </p><p> A series of experiments were carried out in which wastewater sludge was digested at a range of temperatures (35°C, 49°C, 51°C, 53°C, 55°C, 57.5°C). Each reactor was operated for a period at steady state in order to make observations of microbial activity, digestion performance, and biosolids aesthetics as affected solely by digestion temperature. Results of this study show that poor operational stability arises in reactors operated at 57.5°C. Elevated concentrations of hydrogen and short-chain fatty acids in the 57.5°C digesters are evidence that the observed temperature-induced digester failures are related to the temperature sensitivity of hydrogenotrophic (CO2-reducing) methanogens. Reactors operated at other temperatures performed equally well with respect to solids removal and operational stability. </p><p> In addition, peak volatile organic sulfur compound (VOSC) production from biosolids treated at 51°C and above was greatly reduced in comparison with mesophilic anaerobic digestion and a lower temperature (49°C) thermophilic system. Since the biosolids methanogenic community appeared to be equally capable of degrading VOSC over the range of thermophilic temperatures, the conclusion is that the activity of VOSC producing organisms in digested and dewatered biosolids is greatly reduced when operating temperature in excess of 51°C are used. </p><p> This study shows that small changes in an operationally defined parameter such as digestion temperature can have a large impact on the performance and stability of a digestion process. Single minded selection of digestion temperature in order to achieve effective pathogen reduction can result in poor digester performance and the production of an aesthetically unacceptable product. Careful selection, however, of an appropriate digestion temperature can not only ensure successful pathogen reduction in compliance with current regulations, but can also improve the performance, stability, and aesthetic quality of digestion systems employing thermophilic anaerobic digestion.</p> Master of Science 2014-03-14T20:48:10Z 2014-03-14T20:48:10Z 2006-11-08 2006-11-20 2009-12-13 2006-12-13 Thesis etd-11202006-102834 http://hdl.handle.net/10919/35771 http://scholar.lib.vt.edu/theses/available/etd-11202006-102834/ Wilson_ETD_Thesis.pdf In Copyright http://rightsstatements.org/vocab/InC/1.0/ application/pdf Virginia Tech |
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methanogenesis thermophilic anaerobic digestion biosolids odors |
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methanogenesis thermophilic anaerobic digestion biosolids odors Wilson, Christopher Allen The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
description |
<p> The performance and stability of a thermophilic anaerobic digestion system are inherently
dependent on the engineered environment within each reactor. While the selection of operational
parameters such as mixing, solids retention time, and digestion temperature are often selected on
the basis of certain desirable outcomes such as the deactivation of human pathogens, these
parameters have been shown to have a broad impact on the overall sludge digestion process.
Since the current time-temperature requirements for biosolids pathogen reduction are most easily
met at elevated digestion temperatures within the thermophilic range, it is certainly worth
examining the effect of specific digestion temperatures on ancillary factors such as operational stability and the aesthetic quality of biosolids.
</p><p>
A series of experiments were carried out in which wastewater sludge was digested at a range of
temperatures (35°C, 49°C, 51°C, 53°C, 55°C, 57.5°C). Each reactor was operated for a period
at steady state in order to make observations of microbial activity, digestion performance, and
biosolids aesthetics as affected solely by digestion temperature. Results of this study show that poor operational stability arises in reactors operated at 57.5°C. Elevated concentrations of
hydrogen and short-chain fatty acids in the 57.5°C digesters are evidence that the observed
temperature-induced digester failures are related to the temperature sensitivity of
hydrogenotrophic (CO2-reducing) methanogens. Reactors operated at other temperatures
performed equally well with respect to solids removal and operational stability.
</p><p>
In addition, peak volatile organic sulfur compound (VOSC) production from biosolids treated at
51°C and above was greatly reduced in comparison with mesophilic anaerobic digestion and a
lower temperature (49°C) thermophilic system. Since the biosolids methanogenic community
appeared to be equally capable of degrading VOSC over the range of thermophilic temperatures,
the conclusion is that the activity of VOSC producing organisms in digested and dewatered
biosolids is greatly reduced when operating temperature in excess of 51°C are used.
</p><p>
This study shows that small changes in an operationally defined parameter such as digestion
temperature can have a large impact on the performance and stability of a digestion process.
Single minded selection of digestion temperature in order to achieve effective pathogen
reduction can result in poor digester performance and the production of an aesthetically
unacceptable product. Careful selection, however, of an appropriate digestion temperature can
not only ensure successful pathogen reduction in compliance with current regulations, but can
also improve the performance, stability, and aesthetic quality of digestion systems employing
thermophilic anaerobic digestion.</p> === Master of Science |
author2 |
Environmental Engineering |
author_facet |
Environmental Engineering Wilson, Christopher Allen |
author |
Wilson, Christopher Allen |
author_sort |
Wilson, Christopher Allen |
title |
The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
title_short |
The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
title_full |
The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
title_fullStr |
The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
title_full_unstemmed |
The Effect of Steady-State Digestion Temperature on the Performance, Stability, and Biosolids Odor Production associated with Thermophilic Anaerobic Digestion |
title_sort |
effect of steady-state digestion temperature on the performance, stability, and biosolids odor production associated with thermophilic anaerobic digestion |
publisher |
Virginia Tech |
publishDate |
2014 |
url |
http://hdl.handle.net/10919/35771 http://scholar.lib.vt.edu/theses/available/etd-11202006-102834/ |
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