Produção de hidrogênio e metabólitos em reator anaeróbio de leito fluidizado e em reator de leito granular expandido a partir de glicerol

Abstract

This work aimed to evaluated the biological hydrogen production using crude glycerol as feedstock in two anaerobic reactors: (1) anaerobic fluidized bed reactor (AFBR), that allows high mass transfer, and (2) an expanded granular sludge blanket reactor, that can used with high efficiency even at high organic loading. In the AFBR, it was evaluated the influence of HRT (14, 12, 10, 8, 6, 4, 2 and 1 hour) in the hydrogen production using crude glycerol as feedstock at 5 g.L-1 and expanded clay as support material. In the EGSB, the HRT varied from 24 to 1 hour, it was used the same feedstock as that used in the AFBR. The reactors were maintained at controlled temperature at 30°C. The noculum for AFBR and EGSB was granular sludge taken from UASB reactor treating poultry slaughterhouse that was previously submitted to heat treatment. In the AFBR, the hydrogen production rate (HPR) increased from 0.08 to 0.73L.h-1.L -1 with the decrease at HRT from 14 to 1 hour, respectively. The hydrogen yield (HY) did not presented the same trend and remained almost unchanged (0.62, 0.76, 0.73, 0.75, 0.60, 0.58, 0.69, 0.85 molH2.mol-1glycerol). For this reactor, the main byproducts were 1,3-propanediol (1,3-PD), ethanol, acetic, butyric and propionic acid. The highest 1,3-PD (1,230 mg.L-1), ethanol (723 mg.L-1), acetic acid (204 mg.L-1), propionic acid (759 mg.L-1) and butyric acid (324 mg.L-1) concentration occurred at HRT of 6, 14, 8, 2, 6 hours, respectively. In the EGSB, the HPR and the HY presented the same trend: HPR increased from 0.018 to 1.708 L.h-1.L-1 and HY increased from 0.19 to 2.87 molH2.mol-1glycerol with the decrease in the HRT from 14 to 1 hour. For both reactors, the AFBR and the EGSB,the highest HPR and HY occurred at HRT of 1 hour. As well as for the AFBR, the main byproducts quantified in the EGSB were 1,3-propanediol (1,3-PD), ethanol, acetic, butyric and propionic acid. The highest 1,3-PD (1,606 mg.L -1), ethanol (400 mg.L-1), acetic acid (219 mg.L-1), propionic acid (1,075 mg.L-1) and butyric acid (248 mg.L-1) concentration occurred at HRT of 16, 12, 16, 8, 20 hours, respectively.