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Abstract: Investigating how a bioreactor functions is a necessary precursor for successful reactor design and operation. Traditional methods used to investigate flow-field cannot meet this challenge accurately and economically. Hydrodynamics model can solve this problem, but to understand a bioreactor in sufficient depth, it is often insufficient. In this paper, a coupled hydrodynamics-reaction kinetics model was formulated from computational fluid dynamics (CFD) code to simulate a gas–liquid–solid three-phase biotreatment system for the first time. The hydrodynamics model is used to formulate prediction of the flow field and the reaction kinetics model then portrays the reaction conversion process. The coupled model is verified and used to simulate the behavior of an expanded granular sludge bed (EGSB) reactor for biohydrogen production. The flow patterns were visualized and analyzed. The coupled model also demonstrates a qualitative relationship between hydrodynamics and biohydrogen production. The advantages and limitations of applying this coupled model are discussed. [ABSTRACT FROM AUTHOR]

Abstract: There has been little work on the optimal configuration of biohydrogen production reactors. This paper describes three-dimensional computational fluid dynamics (CFD) simulations of gas–liquid flow in a laboratory-scale continuous stirred-tank reactor used for biohydrogen production. To evaluate the role of hydrodynamics in reactor design and optimize the reactor configuration, an optimized impeller design has been constructed and validated with CFD simulations of the normal and optimized impeller over a range of speeds and the numerical results were also validated by examination of residence time distribution. By integrating the CFD simulation with an ethanol-type fermentation process experiment, it was shown that impellers with different type and speed generated different flow patterns, and hence offered different efficiencies for biohydrogen production. The hydrodynamic behavior of the optimized impeller at speeds between 50 and 70rev/min is most suited for economical biohydrogen production. [Copyright &y& Elsevier]

The effect of different gases, CO2 concentration, and separation of CO2 from reaction system on photo-fermentation H2 production was investigated by batch culture in this study. Experimental results showed that different gases (Ar,N2,CO2, and air) as gas phase have obviously affected on photo-H2 production and a high concentration of CO2 can inhibit the growth and H2 evolution of Rhodopseudomonas faecalis RLD-53. When CO2 concentration at 5%, cell increased most rapidly the specific growth rate of 0.489g/l/h and the specific growth rate fell to be 0.265g/l/h when CO2 concentration at 40%. However, the growth of RLD-53 at CO2 concentration of 60–100% was almost completely inhibited. At CO2 concentrations of 5% and 10%, the maximum H2 yield was 2.54 and 2.59mol-H2/mol acetate, respectively, and it was similar with the control (2.61mol-H2/mol acetate). H2 not produced when CO2 concentration at 60–100%. In conclusion, separation of CO2 from reaction system can stimulate H2 production in the entire photo-H2 production process and H2 yield increased about 12.8–18.85% than the control. [Copyright &y& Elsevier]

The Rhodopseudomonas faecalis strain RLD-53 was isolated from freshwater pond sludge and was demonstrated it could produce hydrogen. This study to investigate their ability of hydrogen production under some conditions in batch culture experiments. At pH 7.0, temperature 35°C and light intensity of 4000lux, the H2 yield was 2.64mol-H2/mol-acetate, 2.34mol-H2/mol-propionate, 1.75mol-H2/mol-lactate and 3.55mol-H2/mol-malate, respectively. The maximal H2 production rate of 32.62ml-H2/l/h and H2 yield of 2.84mol-H2/mol-acetate were achieved when beef extract was used as nitrogen source. Light intensity is the most important factor for H2 production, H2 production yield and rate decreased with increasing light intensity and reached highest under light intensity of 3000–5000lux. Result indicated the strain RLD-53 was a high efficient bacteria for hydrogen production. [Copyright &y& Elsevier]

Abstract: In this study, some key factors, for example, diluted ratio of effluents, the ratio of dark-photo bacteria, light intensity and light/dark cycle influencing hydrogen production by combining Clostridium butyricum and immobilized Rhodopseudomonas faecalis RLD-53 in batch culture, were investigated. Experimental results showed the photo-hydrogen yield decreased when increasing diluted ratio from 1:0.5 to 1:3, and it reached the maximum value of 4368ml-H2/l-effluents at the ratio of 1:0.5. When the ratio of dark-photo bacteria was at 1:2, the hydrogen yield reached highest value of 4.946mol-H2/mol-glucose and cumulative hydrogen volume was 5357ml-H2/l-culture during the combination process. When the light intensity was at 10.25W/m2, the hydrogen volume of photo-fermentation and the combination process reached maximum value of 4260ml-H2/l-effluents and 5892ml-H2/l-culture, respectively. During the combination process, maximum total hydrogen yield was 5.374mol-H2/mol-glucose. Meanwhile, hydrogen production under light/dark cycle was evaluated. [Copyright &y& Elsevier]

Abstract: In order to increase the hydrogen yield from glucose, hydrogen production by immobilized Rhodopseudomonas faecalis RLD-53 using soluble metabolites from ethanol fermentation bacteria Ethanoligenens harbinense B49 was investigated. The soluble metabolites from dark-fermentation mainly were ethanol and acetate, which could be further utilized for photo-hydrogen production. Hydrogen production by B49 was noticeably affected by the glucose and phosphate buffer concentration. The maximum hydrogen yield (1.83mol H2/mol glucose) was obtained at 9g/l glucose. In addition, we found that the ratio of acetate/ethanol (A/E) increased with increasing phosphate buffer concentration, which is favorable to further photo-hydrogen production. The total hydrogen yield during dark- and photo-fermentation reached its maximum value (6.32mol H2/mol glucose) using 9g/l glucose, 30mmol/l phosphate buffers and immobilized R. faecalis RLD-53. Results demonstrated that the combination of dark- and photo- fermentation was an effective and efficient process to improve hydrogen yield from a single substrate. [Copyright &y& Elsevier]

The design of an optimum and cost-efficient medium for high-level production of hydrogen by Ethanoligenens harbinense B49 was attempted by using response surface methodology (RSM). Based on the Plackett–Burman design, Fe2+ and Mg2+ were selected as the most critical nutrient salts. Subsequently, the optimum combination of the selected factors and the sole carbon source glucose were investigated by the Box–Behnken design. Results showed that the maximum hydrogen yield of 2.21mol/molglucose was predicted when the concentrations of glucose, Fe2+ and Mg2+ were 14.57g/L, 177.28mg/L and 691.98mg/L, respectively. The results were further verified by triplicate experiments. The batch reactors were operated under an optimized condition of the respective glucose, Fe2+ and Mg2+ concentration of 14.5g/L, 180mg/L and 690mg/L, the initial pH of 6.0 and experimental temperature of 35±1 oC. Without further pH adjustment, the maximum hydrogen yield of 2.20mol/molglucose was obtained based on the optimized medium with further verified the practicability of this optimum strategy. [Copyright &y& Elsevier]