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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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
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