Effect of Operating Condition on Performance of Anaerobic Hybrid Reactor at Thermophilic Temperature

Abstract

Anaerobic hybrid reactor (AHR), like the upflow anaerobic sludge bed-fixed film reactor, was applied to treat and produce methane from raw palm oil mill effluent (POME) with high chemical oxygen demand (COD) and suspended solid (SS). This study was aimed at improving anaerobically digested POME at thermophilic temperature (55 °C) through optimization of organic loading rate (OLR) and hydraulic retention time (HRT). COD removal and methane production were measured as indicators of the reactor performance as well as pH and ratio of total volatile acid (TVA) and alkalinity (Alk) were used for the reactor stability. Microbial activities of inoculum seed for acidogens and methanogens at thermophilic temperature were 0.17 gCOD_methane/gVSS.d and 0.72 gCOD_glucose/gVSS.d, respectively. Experimental results within 78 days showing that OLR and HRT of AHR for methane production increased from 1.2 to 5.5 gCOD/l.d and shortened from 20 to 10 d, respectively. AHR was investigated in order to achieve high reactor performance and stability. High microbial activities of acidogens and methanogens in sludge and packed zones of AHR were found during operation. High performances of COD removal efficiency and methane production rate were in the range of 80-90% and increased from 1.35 to 7.82 l/d, respectively, when the OLR increased and HRT decreased within the tested range. In addition, methane yield coefficient was increased from 0.19 to 0.32 lCH₄/gCOD removed.High reactor stability could keep in pH 7.0-8.0 andTVA/Alk was lower than 0.5.

Keywords: Anaerobic hybrid reactor, Palm oil mill effluent, Operating condition, Thermophilic temperature.