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A comparative kinetic evaluation of the anaerobic digestion of untreated molasses and molasses previously fermented with Penicillium decumbens in batch reactors
A comparative kinetic study was carried out on the anaerobic digestion of untreated beet molasses alcoholic fermentation wastewater and beet molasses previously fermented with Penicillium decumbens. Three 1 l volume stirred tank reactors were used for the study, one with freely suspended biomass (Co...
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Published in: | Biochemical engineering journal 2004-05, Vol.18 (2), p.121-132 |
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Main Authors: | , , |
Format: | Article |
Language: | English |
Subjects: | |
Citations: | Items that this one cites Items that cite this one |
Online Access: | Get full text |
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Summary: | A comparative kinetic study was carried out on the anaerobic digestion of untreated beet molasses alcoholic fermentation wastewater and beet molasses previously fermented with
Penicillium decumbens. Three 1
l volume stirred tank reactors were used for the study, one with freely suspended biomass (Control), and the other two with biomass supported on Saponite (magnesium silicate) and Esmectite (aluminium silicate), respectively. The reactors were batch fed at mesophilic temperature (35
°C) using COD loadings of between 12 and 140
ml of untreated molasses with a COD of 80.5
g/l and of between 43 and 304
ml of molasses previously fermented with a COD of 23.0
g/l. The anaerobic digestion process of both substrates was found to follow a first-order kinetics and the experimental accumulated methane volume (
G)–time (
t) data to conform to an equation of the form:
G=
G
m[1−exp(−
K
0
t)], from which the specific rate constants,
K
0, were calculated. In the case of untreated molasses, the
K
0 values decreased considerably from 2.87 to 0.10 (Saponite), from 2.78 to 0.10 (Esmectite) and from 2.16 to 0.07 per days (Control) when the loading of molasses applied and initial COD added were increased from 12 to 140
ml and 1 to 10
g/l, respectively; this showed an inhibition phenomenon in the three reactors studied. In contrast to this, the kinetic constants of the anaerobic digestion of pre-treated molasses were virtually constant over the COD range used (1–7
g/l) in the three reactors considered. Finally, the average methane yield coefficient for pre-treated molasses was 305
ml CH
4 STP/g COD
removed, viz. 35% higher than that provided by untreated molasses. |
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ISSN: | 1369-703X 1873-295X |
DOI: | 10.1016/S1369-703X(03)00198-0 |