Start-up criteria for a Upflow Anaerobic Sludge Blanket (UASB) reactor

A laboratory scale Upflow Anaerobic Sludge Blanket (UASB) reactor study was done with spentwash (distillery effluent) as substrate. The start-up studies revealed that the recirculation of biogas, produced during the initial stages, under low organic loading rates helps in mixing as well as partial supplementation of carbon dioxide for excess hydrogen in the reactor. The gas composition before and after recirculation, the volatile acids profile and the solids variation along the reactor height before and after recirculation were studied. The process efficiency and methane content increases substantially after recirculation of biogas and the microscopic examination of the sludge during the experiment indicates that the granules mainly composed of long multicellular filaments of rod shaped organisms, presumably methanothrix soehngenii.