Performance of Anaerobic Fluidized/Expanded Bed Reactor Using Corn Cob Flour as Microcarriers.

Abstract

We investigated the treatment characteristics of the fluidized/expanded bed reactor (reactor A) using corn cob flour (CCF) as microcarriers and compared it to a UASB reactor (reactor B) .The fluidized/expanded bed reactor using CCF was used as a methane fermentation reactor of mesophilic two-phase digestion type, and synthetic wastewater used in this study was a mixtere of volatile fatty acids. The loading rates in both reactors were increased gradually by mainly decreasing the hydraulic retention time (HRT) .After 120 days, COD loading rate in reactor A was 30kg-CODcr⋅m-3⋅day-1 with a biogas production of about 90l⋅day-1.On the other hand, the COD loading rate in reactor B was over 20kg-CODcr⋅m-3⋅day-1 after 90 days with a biogas production of about 85l⋅day-1. The methane content and gas yield in both reactors were calculated to be 70-80% and 600l⋅kg-COD removed-1 for reactor A and 70-80% and 570l⋅kg-COD removed-l for reactor B. The lag between the start-up period in reactor A compared to that in reactor B appears to be affected by the amount of anaerobic seed sludge. The low C3-VFA removal rate caused the accumulation of propionic acid. The operation of both the reactors resulted in the accumulation of granule-like particles made up of anaerobic microorganisms. We found cocci, short rods and rod-type microorganisms on the surface of both sludges. These microorganisms resembled the genus of Methanococcus, Methanobacterium and Methanothix. From this data, it was concluded that CCF may be utilized as microcarriers for the fluidized/expanded bed reactor.