Biotechnology Industry |
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Environmental Biotechnology |
Electronic Journal of Biotechnology ISSN: 0717-3458 |
Vol.
10 No. 3, Issue of July 15, 2007 |
© 2007 by Pontificia Universidad Católica
de Valparaíso -- Chile |
Received June 6,
2006 / Accepted March 5, 2007 |
DOI: 10.2225/vol10-issue3-fulltext-7 |
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Effect of temperature on the anaerobic
digestion of palm oil mill effluent
Wanna
Choorit*
Biotechnology
Program
School of Agricultural Technology
Walailak University
Tasala, Nakhonsithammarat 80160 Thailand
Tel: 667 567 2355
Fax: 667 567 2302
E-mail: cwanna@wu.ac.th
Pornpan
Wisarnwan
Biotechnology
Program
School of Agricultural Technology
Walailak University
Tasala, Nakhonsithammarat 80160 Thailand
Tel: 667 567 2303
Fax: 667 567 2302
E-mail: rombiot@hotmail.com
*Corresponding
author
Financial
support:
Walailak University
and the Southern Palm (1978) Co., Ltd.
Keywords:
hydraulic retention times, mesophilic reactor, methane, organic
loading rate, temperature variations, thermophilic reactor, volatile
fatty acids.
Abbreviations: |
BOD:
biochemical oxygen demand
COD: chemical oxygen demand
CSTRs: continuous stirred tank reactors
HRT: hydraulic retention time
OLRs: organic loading rates
POME: palm oil mill effluent
TKN: total Kjeldahl nitrogen
TS: total solid
TSS: total suspended solid
TVFA: total volatile fatty acid
UASFF: up-flow anaerobic sludge fixed film
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Two
continuous stirred tank reactors (CSTRs) each fed with palm oil mill
effluent (POME), operated at 37șC and 55șC, respectively, were investigated
for their performance under varies organic loading rates (OLRs). The
37șC
reactor operated successfully at a maximum OLR of 12.25 g[COD]/L/day
and a hydraulic retention time (HRT) of 7 days. The 55șC reactor operated successfully
at the higher loading rate of 17.01 g[COD]/L/day and had a HRT of
5 days. The 37șC
reactor achieved a 71.10% reduction of chemical oxygen demand (COD),
a biogas production rate of 3.73
L of gas/L[reactor]/day containing 71.04% methane,
whereas the 55șC reactor achieved a 70.32% reduction
of COD, a biogas production rate of 4.66 L of gas/L[reactor]/day containing
69.53% methane. An OLR of 9.68 g[COD]/L/day, at a HRT of 7 days, was
used to study the effects of changing the temperature by 3șC increments. The reactor processes
were reasonably stable during the increase from 37șC to 43șC and the decrease from 55șC
to 43șC.
When the temperature was increased from 37șC
to 46șC,
the total volatile fatty acid (TVFA) concentration and biogas production
was 2,059 mg as acetic acid/L and 1.49 L of gas/L[reactor]/day at day 56,
respectively. When the temperature was reduced from 55șC to 40șC, the TVFA concentration and
biogas production was 2,368 mg as acetic acid/L and 2.01 L of gas/L[reactor]/day at day 102,
respectively. By first reducing the OLR to 4.20 g[COD]/L/day then
slowly increasing the OLR back to 9.68 g[COD]/L/day, both reactors
were restored to stable conditions at 49șC
and 37șC
respectively. The initial 37șC
reactor became fully acclimatized at 55șC
with an efficiency similar to that when operated at the initial 37șC
whereas the 55șC
reactor also achieved stability at 37șC
but with a lower efficiency.
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