Ronnachai Chaisri, Piyarat Boonsawang, Poonsuk Prasertsan, and Sumate Chaiprapat

pp. 311 - 323

Abstract

Anaerobic treatment of palm oil mill effluent (POME) with the separation of the acidogenic and methanogenic phase was studied in an up-flow anaerobic sludge blanket (UASB) reactor and an up-flow anaerobic filter (UFAF) reactor. Furthermore, the effect of OLR on methane and volatile fatty acid productions in UASB and UFAF reactors was investigated. In this research, UASB as acidogenic reactor was used for volatile fatty acid production and UFAF as methanogenic reactor was used for methane production. Therefore, POME without pH adjustment was used as influent for the UASB reactor. Moreover, the synthetic wastewater with pH adjustment to 6.00 was fed into the UFAF reactor. The inoculum source for both reactors was the combination of POME sludge collected from the CSTR of a POME treatment plant and granule
sludge collected from the UASB reactor of a frozen sea food industry treatment plant. During experimental operation, the organic loading rate (OLR) was gradually increased from 2.50 to 17.5 g COD/l/day in the UASB reactor and 1.10 to 10.0 g COD/l/day in the UFAF reactor. Consequently, hydraulic retention time (HRT) ranged from 20.0 to 2.90 days in the UASB reactor and from 13.5 to 1.50 days in the UFAF reactor. The result showed that the COD removal efficiency from both reactors was greater than 60.0%. In addition,
the total volatile fatty acids increased with the increasing OLR. The total volatile fatty acids and acetic acid production in the UASB reactor reached 5.50 g/l and 4.90 g/l, respectively at OLR of 17.5 g COD/l/day and HRT of 2.90 days before washout was observed. In the UFAF reactor, the methane and biogas production
increased with increasing OLR until an OLR of 7.50 g COD/l/day. However, the methane and biogas production significantly decreased when OLR increased up to 10.0 g COD/l/day. Therefore, the optimum OLR in the laboratory-scale UASB and UFAF reactors were concluded to be 15.5 and 7.50 g COD/l/day, respectively.