Estratégia operacional para maximizar a produção de metano em reatores UASB tendo como substrato vinhoto.

Abstract

In this thesis, it was tried to evaluate an operational strategy for maximizing the production o f methane in UASB reactor treating vinasse. To this end, four UASB reactors were operated (Ri, R2, R3 and R4) and subjected to different operational conditions. While the first two were operated at room temperature for 130 days, the latter two were operated at a constant temperature o f 37 °C for 60 days. The reactors Ri and R3, taken as references reactors were operated relatively low load at high efficiency, whereas reactors R2 and R» were overload with organic material in order to produce a sludge rich in methanogenic bacteria for high degradation rates o f the substrate. The maximum volumetric organic load (VOC) attained in reactor R| was 14 gCOD / L.d, with an efficiency o f organic material removal in the reactor ranging between 58% and 92%. R2 on the other hand, showed a VOC o f 28 gCOD/L.d. with an average efficiency o f 48%. Reactors R3 and R4, reached a maximum VOCs o f 35 and 45 gCOD / L.dia respectively, with COD removal efficiencies o f 80 and 65% respectively. The performance o f the reactors was compared with regard to removed volumetric organic load and methane production. The maximum VOCremoved were 11, 14, 28 And 31 gCOD / L.dia and the maximum methane productions were 82,9, 97,1, 177.4 and 176.9 respectively for the reactors Ri, R2, R3 and R». The characteristics of the sludge as a function of imposed operating conditions in the reactor were assessed by specific tests for reactors Ri, R2. The sludge reactor R2 had significant changes in the SMA (specific methanogenic activity) values of SMA, rising from 0.44 gCOD-CHVgSVT.d at the beginning o f the operation to 0.92 gCOD-CHVgSVT.d at the end o f the operation period. The sludge o f Rj in turn did not have the same increase in SMA values, exhibiting a maximum at 0.68 gCOD-CHVgSVT.d. This shows that the operational strategy o f maintaining a UASB reactor overloaded, favoured the growth o f a group o f organisms with high rates o f substrate degradation, which were shown to be superior to microorganisms developing in the reactor operated with high removal efficiency of organic matter. However during the trial period there was a loss o f sludge in the reactor R2 , so that the methane production capacity did not increase in proportion to the increase in SMA. I t was not possible to identify the reason for the loss o f sludge.