Treatment of thin stillage in a high-rate anaerobic fluidized bed bioreactor (AFBR)

The primary objective of this work was to investigate the treatability of thin stillage as a by-product of bioethanol production plants using an anaerobic fluidized bed bioreactor (AFBR) employing zeolite with average diameter of (dm) of 425–610 μm and specific surface area (SSA) of 26.5 m2/g as the carrier media. Despite the very high strength of thin stillage with chemical oxygen demand of 130,000 mg TCOD/L and suspended solids of 47,000 mg TSS/L, the AFBR showed up to 88% TCOD and 78% TSS removal at very high organic and solids loading rates (OLR and SLR) of 29 kg COD/m3 d and 10.5 kg TSS/m3 d respectively and hydraulic retention time (HRT) of 3.5 days. Methane production rates of up to 160 L/d at the steady state equivalent to 40 LCH4/Lthin stillage d and biogas production rate per reactor volume of 15.8 Lgas/Lreactor d were achieved.