Controlling methane and hydrogen production from cheese whey in an EGSB reactor by changing the HRT.

This study assessed the effects of hydraulic retention time (HRT; 8 h-0.25 h) on simultaneous hydrogen and methane production from cheese whey (5000 mg carbohydrates/L) in a mesophilic (30 °C) expanded granular sludge bed (EGSB) reactor. Methane production was observed at HRTs from 4 to 0.25 h. The maximum methane yield (9.8 ± 1.9 mL CH4/g CODap, reported as milliliter CH4 per gram of COD applied) and methane production rate (461 ± 75 mL CH4/day Lreactor) occurred at HRTs of 4 h and 2 h, respectively. Hydrogen production increased as methane production decreased with decreasing HRT from 8 to 0.25 h. The maximum hydrogen yield of 3.2 ± 0.3 mL H2/g CODap (reported as mL H2 per gram of COD applied) and hydrogen production rate of 1951 ± 171 mL H2/day Lreactor were observed at the HRT of 0.25 h. The decrease in HRT from 8 to 0.25 h caused larger changes in the bacterial populations than the archaea populations. With the decrease in HRT (6 h-0.25 h), the Shannon diversity index decreased (3.02-2.87) for bacteria and increased (1.49-1.83) for archaea. The bacterial dominance increased (0.059-0.066) as the archaea dominance decreased (0.292-0.201) with the HRT decrease from 6 to 0.25 h.

Valorization of the Crude Glycerol for Propionic Acid Production Using an Anaerobic Fluidized Bed Reactor with Grounded Tires as Support Material.

This study evaluated the propionic acid (HPr) production from crude glycerol (CG) (5000 mg L-1) in an anaerobic fluidized bed reactor (AFBR). Grounded tire particles (2.8-3.35 mm) were used as support material for microbial adhesion. The reactor was operated with hydraulic retention times (HRT) varying from 8 to 0.5 h under mesophilic (30 °C) conditions. The HPr was the main metabolite produced, increasing in composition from 66.5 to 99.6% by decreasing the HRT from 8 to 0.5 h. Other metabolic products were 1,3-propanediol, with a maximum of 29.4% with an HRT of 6 h, ethanol, acetic, and butyric acids. The decrease in HRT from 8 to 0.5 h decreased the HPr yield, with a maximum of 0.48 ± 0.06 g HPr g COD-1 and an HRT of 6 h, and favored HPr productivity, with a maximum of 4.09 ± 1.24 g L-1 h-1 and HRT of 0.5 h. In the biogas, the H2 content increased from 12.5 to 81.2% by decreasing the HRT from 8 to 0.5 h. These results indicate the potential application of the AFBR for HPr production using an immobilized mixed culture.

Co-Fermentation of Cheese Whey and Crude Glycerol in EGSB Reactor as a Strategy to Enhance Continuous Hydrogen and Propionic Acid Production.

This study evaluated the production of hydrogen and propionic acid in an expanded granular sludge bed (EGSB) reactor by co-fermentation of cheese whey (CW) and crude glycerol (CG). The reactor was operated at hydraulic retention time (HRT) of 8 h by changing the CW/CG ratio from 5:1 to 5:2, 5:3, 5:4, and 5:5. At the ratio of 5:5, HRT was reduced from 8 to 0.5 h. The maximum hydrogen yield of 0.120 mmol H2 g COD-1 was observed at the CW/CG ratio of 5:1. Increasing the CG concentration repressed hydrogen production in favor of propionic acid, with a maximum yield of 6.19 mmol HPr g COD-1 at the CW/CG ratio of 5:3. Moreover, by reducing HRT of 8 to 0.5 h, the hydrogen production rate was increased to a maximum value of 42.5 mL H2 h-1 L-1at HRT of 0.5 h. The major metabolites were propionate, 1,3-propanediol, acetate, butyrate, and lactate.

Improving EGSB reactor performance for simultaneous bioenergy and organic acid production from cheese whey via continuous biological H2 production.

OBJECTIVES: To evaluate the influence of hydraulic retention time (HRT) and cheese whey (CW) substrate concentration (15 and 25 g lactose l-1) on the performance of EGSB reactors (R15 and R25, respectively) for H2 production. RESULTS: A decrease in the HRT from 8 to 4 h favored the H2 yield and H2 production rate (HPR) in R15, with maximum values of 0.86 ± 0.11 mmol H2 g COD-1 and 0.23 ± 0.024 l H2 h-1 l-1, respectively. H2 production in R25 was also favored at a HRT of 4 h, with maximum yield and HPR values of 0.64 ± 0.023 mmol H2 g COD-1 and 0.31 ± 0.032 l H2 h-1 l-1, respectively. The main metabolites produced were butyric, acetic and lactic acids. CONCLUSIONS: The EGSB reactor was evaluated as a viable acidogenic step in the two-stage anaerobic treatment of CW for the increase of COD removal efficiency and biomethane production.

Continuous Hydrogen Production from Agricultural Wastewaters at Thermophilic and Hyperthermophilic Temperatures.

The objective of this study was to investigate the effects of hydraulic retention time (HRT) (8 to 0.5 h) and temperature (55 to 75 °C) in two anaerobic fluidized bed reactors (AFBR) using cheese whey (AFBR-CW = 10,000 mg sugars L-1) and vinasse (AFBR-V = 10,000 mg COD L-1) as substrates. Decreasing the HRT to 0.5 h increased the hydrogen production rates in both reactors, with maximum values of 5.36 ± 0.81 L H2 h-1 L-1 in AFBR-CW and 0.71 ± 0.16 L H2 h-1 L-1 in AFBR-V. The optimal conditions for hydrogen production were the HRT of 4 h and temperature of 65 °C in AFBR-CW, observing maximum hydrogen yield (HY) of 5.51 ± 0.37 mmol H2 g COD-1. Still, the maximum HY in AFBR-V was 1.64 ± 0.22 mmol H2 g COD-1 at 4 h and 55 °C. However, increasing the temperature to 75 °C reduced the hydrogen production in both reactors. Methanol and butyric, acetic, and lactic acids were the main metabolites at temperatures of 55 and 65 °C, favoring the butyric and acetic metabolic pathways of hydrogen production. The increased productions of lactate, propionate, and methanol at 75 °C indicate that the hydrogen-producing bacteria in the thermophilic inoculum were inhibited under hyperthermophilic conditions.

Bioconversion of waste office paper to hydrogen using pretreated rumen fluid inoculum.

In this study, a microbial consortium from an acid-treated rumen fluid was used to improve the yields of H2 production from paper residues in batch reactors. The anaerobic batch reactors, which contained paper and cellulose, were operated under three conditions: (1) 0.5 g paper/L, (2) 2 g paper/L, and (3) 4 g paper/L. Cellulase was added to promote the hydrolysis of paper to soluble sugars. The H2 yields were 5.51, 4.65, and 3.96 mmol H2/g COD, respectively, with substrate degradation ranging from 56 to 65.4 %. Butyric acid was the primary soluble metabolite in the three reactors, but pronounced solventogenesis was detected in the reactors incubated with increased paper concentrations (2.0 and 4.0 g/L). A substantial prevalence of Clostridium acetobutylicum (99 % similarity) was observed in the acid-treated rumen fluid, which has been recognized as an efficient H2-producing strain in addition to ethanol and n-butanol which were also detected in the reactors.