Anaerobic digestion from residue of industrial cassava industrialization with acidogenic and methanogenic physical separation phases

A trial was carried out in a continuous regimen, using a completely stirred tank reactor, at acidogenic phase, and a hybrid reactor (upflow anaerobic sludge blanket + fixed bed) at methanogenic phase at room temperature. The residue to be treated came from a flour and cassava meal industry, and the reactors operated for 300 d with affluent chemical oxygen demand (COD) conc entrations of 7500, 9000, 11,000, and 14,000 mg/L. The final results showed a biogas production with a content of 80% methane and an average reduction of COD and free cyanide of nearly 96 and 98%, respectively. The separation of phases selected bacterial groups. At acidogenic phase, a predominance o f propionic, iz-butyric, and Iz-valeric acids, as well as a biomass compose d of 95% fermentative bacilli, which were responsible for a 90% reduction i n free cyanide concentration, was observed. At methanogenic phase, a predom inance of methanogenic bacteria that came only from the Methanothrix genus was observed. The bacteria were responsible for high levels of organic matt er removal and methane production.