Anaerobic Digestion of Sugarcane Vinasse Through a Methanogenic UASB Reactor Followed by a Packed Bed Reactor.

The anaerobic treatment of raw vinasse in a combined system consisting in two methanogenic reactors, up-flow anaerobic sludge blanket (UASB) + anaerobic packed bed reactors (APBR), was evaluated. The organic loading rate (OLR) was varied, and the best condition for the combined system was 12.5 kg COD m-3 day-1 with averages of 0.289 m3 CH4  kg COD r-1 for the UASB reactor and 4.4 kg COD m-3 day-1 with 0.207 m3 CH4  kg COD r-1 for APBR. The OLR played a major role in the emission of H2 S conducting to relatively stable quality of biogas emitted from the APBR, with H2 S concentrations <10 mg L-1 . The importance of the sulphate to COD ratio was demonstrated as a result of the low biogas quality recorded at the lowest ratio. It was possible to develop a proper anaerobic digestion of raw vinasse through the combined system with COD removal efficiency of 86.7% and higher CH4 and a lower H2 S content in biogas.