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Management of hydrogen sulfide in anaerobic digestion of enzyme pretreated marine macro-algae

Haghighatafshar, Salar LU (2012) VVA820 20121
Chemical Engineering
Abstract
Enzymatic pretreatment of algae – by means of cellulose degrading enzyme – was evaluated through lab-scale and pilot-scale experiments. The degradation efficiency of the enzyme depended on the initial physical quality of the algae. Lab-scale batch anaerobic digestion experiments showed comparatively low methane potential for the pretreated algae at both mesophilic and thermophilic temperatures. However, the raw algae (cut into small pieces) were found to be hardly hydrolysable. The methane potential of raw algae in thermophilic and mesophilic digestion was about 17 NmL/gVS and −36 NmL/gVS respectively. Presence of inhibitory agent(s) was obvious at both temperatures. Very fast growth of sulfate-reducing bacteria was noticed in the... (More)
Enzymatic pretreatment of algae – by means of cellulose degrading enzyme – was evaluated through lab-scale and pilot-scale experiments. The degradation efficiency of the enzyme depended on the initial physical quality of the algae. Lab-scale batch anaerobic digestion experiments showed comparatively low methane potential for the pretreated algae at both mesophilic and thermophilic temperatures. However, the raw algae (cut into small pieces) were found to be hardly hydrolysable. The methane potential of raw algae in thermophilic and mesophilic digestion was about 17 NmL/gVS and −36 NmL/gVS respectively. Presence of inhibitory agent(s) was obvious at both temperatures. Very fast growth of sulfate-reducing bacteria was noticed in the continuous digestion, so that in less than 20 days, hydrogen sulfide concentrations over 10000 ppm were observed in both meso- and thermophilic reactors. Inhibition of methanogenesis in the thermophilic reactor occurred at unionized dissolved sulfide concentration of about 22 mg/L (10000 ppm in the biogas) while it was mainly nonSRB acetogens that were inhibited in the mesophilic reactor at unionized sulfide concentrations as high as 50 mg/L (17000 ppm in the biogas). This shows that probably thermophilic digestion is more prone to be inhibited at high sulfide concentrations regarding methanogenesis. Micro-aeration was found to be more efficient in the thermophilic reactor while its effect on the mesophilic process was negligible. (Less)
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author
Haghighatafshar, Salar LU
supervisor
organization
course
VVA820 20121
year
type
H2 - Master's Degree (Two Years)
subject
language
English
id
5277171
alternative location
http://www.chemeng.lth.se/exjobbR/E654.pdf
date added to LUP
2015-05-06 14:06:49
date last changed
2015-05-06 14:06:49
@misc{5277171,
  abstract     = {Enzymatic pretreatment of algae – by means of cellulose degrading enzyme – was evaluated through lab-scale and pilot-scale experiments. The degradation efficiency of the enzyme depended on the initial physical quality of the algae. Lab-scale batch anaerobic digestion experiments showed comparatively low methane potential for the pretreated algae at both mesophilic and thermophilic temperatures. However, the raw algae (cut into small pieces) were found to be hardly hydrolysable. The methane potential of raw algae in thermophilic and mesophilic digestion was about 17 NmL/gVS and −36 NmL/gVS respectively. Presence of inhibitory agent(s) was obvious at both temperatures. Very fast growth of sulfate-reducing bacteria was noticed in the continuous digestion, so that in less than 20 days, hydrogen sulfide concentrations over 10000 ppm were observed in both meso- and thermophilic reactors. Inhibition of methanogenesis in the thermophilic reactor occurred at unionized dissolved sulfide concentration of about 22 mg/L (10000 ppm in the biogas) while it was mainly nonSRB acetogens that were inhibited in the mesophilic reactor at unionized sulfide concentrations as high as 50 mg/L (17000 ppm in the biogas). This shows that probably thermophilic digestion is more prone to be inhibited at high sulfide concentrations regarding methanogenesis. Micro-aeration was found to be more efficient in the thermophilic reactor while its effect on the mesophilic process was negligible.},
  author       = {Haghighatafshar, Salar},
  language     = {eng},
  note         = {Student Paper},
  title        = {Management of hydrogen sulfide in anaerobic digestion of enzyme pretreated marine macro-algae},
  year         = {2012},
}