Biological Treatment Of Palm Oil Mill Effluent (Pome) In An Up-Flow Anaerobic Sludge Blanket (Uasb) Btoreactor
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Date
2007-04
Authors
Mat Don, Dr. Mashitah
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Abstract
The development of an effective and simple method for treatment of palm oil mill
effluent (POME) is a challenging task for palm oil mills. Considering the high
organic character of POME, anaerobic process is the most suitable approach for its
treatment. As such,'up-flow anaerobic sludge fixed film (UASFF) bioreactor was
designed for rapid biotransformation of organic matter to methane using granulated
microbial aggregates. lt is a hybrid reactor with an up-flow fixed film (UFF) part
over an upflow anaerobic sludge blanket (UASB) section. lt helps to shorten the
start-up period at low hydraulic retention time (HRT) with increasing organic
loading rate of 2.67-23.15 g COD/.d. Granular sludge was found to develop
rapidly within 20 days with an increase in size of granules from an initial pin point
size to about 2 mm. Besides that, the anaerobic digestion was analyzed and
modeled using response surface methodology (RSM), with HRT and influent
carbon oxygen demand (COD6) as the variables. Results showed that an increase
in the variables resulted in a decrease in COD removal, solid retention time (SRT)
and solid retention factor (SRF), respectively. However, the COD removal rate,
volatile fatty acid (VFA)/alkaline used, CO2 percentage in biogas and methane
production rate tend to increase. The yield of methane was 0.287-0.348 | CHa/g
CODrsrne*6. For biokinetic coefficients; apparent half-velocity constant A, halfvelocity
constant K", maximum specific microbial growth rate pr"r, methane yield
constant Yy and growth yield constant Y" were found to be 0.738 g COD/ l, 0.982
g COD/ l, 0.207 d-', 0.325 | CH4 STP/g COD,",,1ou"6 and 0.174 g VSS/g COD,"'ou"6,
respectively. Apparently, the reactor performance fed with pre-settled and
chemically pretreated POME was also compared. An optimum condition for the
digestion of POME was at feed flow rate Qr 1.65 yd, up-flow velocity V,r 0.6 m/h
and Qr 2.45 Vd and Vuo 0.75 mlh for both cases. Nevertheless, a densely packed
rod (Methanosaeta) and cocci shaped (Methanosarsina) microorganisms were
found to develop in the granular sludge formed in the UASFF bioreactor at various
operating conditions.
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Chemical Engineering