Abstract:
Phase separation of anaerobic process is an importance parameter significantly affecting microbial ecology and characteristics of UASB reactor. In this study two-stage anaerobic process was evaluated in laboratory-scale reactors which consist an acid tank called Hydrolysis Upflow Sludge Blanket (HUSB) 14 L working volume and UASB 3.139 L receiving feed from a palm oil mill wastewater containing COD of 101,333 – 137,000 mg/L. The two reactors operated at room temperature. This study was focused on determining the optimum hydrolysis condition for volatile suspended solid (VSS) removal, enhance organic solid to volatile fatty acid (VFA) and determining the efficiency of phase separation under steady state conditions, HUSB reactor was conducted at initial pH 6.00 and hydraulic retention time (HRT) of 14 days. Removal efficiencies of 75.94% were achieved at feed VSS concentration of 63,600 mg/L and increasing of VFA was 91.18 +- 6.98% in batch experiment, and removal efficiencies of 58.21 +- 4.69 % were achieved at feed VSS concentration of 51,903.70 +- 2,630.51 mg/L and the increasing of VFA was 84.64 +- 2.87 % for continuous reactor (HUSB). In the methanogenesis phase, the UASB reactor was achieved 79.54 +- 2.77% COD removal efficiency at hydraulic retention time (HRT) 24 hours at organic loading 28 kg COD/m[superscript3] –d. Methane content in the produced biogas was 65.7 +- 1.37 % and a methane yield at optimum loading of 0.11 – 0.15 L/g BOD [subscriptRemoved] An increasing alkalinity maintained the methanogenic reactor at around 7.5 and effluent recirculation alleviated the need for alkali additions to the feed of the methanogenic reactor.