Biohydrogen production as a function of pH and substrate concentration.
ABSTRACT The conversion of organics in wastewaters into hydrogen gas could serve the dual role of renewable energy production and waste reduction. The chemical energy in a sucrose rich synthetic wastewater was recovered as hydrogen gas in this study. Using fractional factorial design batch experiments, the effect of varying pH (4.5-7.5) and substrate concentration (1.5-44.8 g COD/L) and their interaction on hydrogen gas production were tested. Mixed bacterial cultures obtained from a compost pile, a potato field, and a soybean field were heated to inhibit hydrogen-consuming methanogens and to enrich sporeforming, hydrogen-producing acidogens. It was determined that the highest rate (74.7 mL H2/(L*h)) of hydrogen production occurred at a pH of 5.5 and a substrate concentration of 7.5 g COD/Lwith a conversion efficiency of 38.9 mL H2/(g COD/L). The highest conversion efficiency was 46.6 mL H2/(g COD/L).
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ABSTRACT: The authors examined the effects of operating parameters on the production by dark fermentation of the wastewater generated from food waste recycling facilities, in short "food waste wastewater (FWW)". Central composite design based response surface methodology was applied to analyze the effect of initial pH (5.5-8.5) and substrate concentration (2-20 g Carbo. COD/L) on production. The experiment was conducted under mesophilic () condition and a heat-treated ( for 20min)anaerobic digester sludge was used as a seeding source. Although there was a little difference in carbohydrate removal, yield was largely affected by the experimental conditions, from 0.38 to 1.77 mol /mol . By applying regression analysis, yield was well fitted based on the coded value to a second order polynomial equation (p = 0.0243): Y = , where , , and Y are pH, substrate concentration (g Carbo. COD/L), and hydrogen yield (mol /mol ), respectively. The 2-D response surface clearly showed a high inter-dependency between initial pH and substrate concentration, and the role of these two factors was to control the pH during fermentation. According to the statistical optimization, the optimum condition of initial pH and substrate concentration were 7.0 and 13.4 g Carbo. COD/L, respectively, under which predicted yield was 1.84 mol /mol . Microbial analysis using 16S rRNA PCR-DGGE showed that sp. such as , , and were main -producers.Transactions of the Korean hydrogen and new energy society. 01/2011; 22(3).
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ABSTRACT: Fermentative hydrogen production is a promising technology for garneting renewable and clean energy from renewable and waste resources. We isolated hydrogen producing bacteria from activated sludge, and profiled their fermentative functions using 16S rRNA gene-directed PCR-denaturing gradient gel electrophoresis (DGGE), clone library and heterotrophic plate isolation. Three individual hydrogen producers, which harboured the [FeFe] hydrogenase gene were isolated and identified by 16S rDNA sequence, and further physiologically characterised for the first time as Clostridium sp. (W1), Clostridium butyricum (W4) and Clostridium butyricum (W5). The C. butyricum W5 demonstrated the best fermentative performance for hydrogen production and was used as working strain throughout this study. We experimentally identified the suitable operating parameters, including carbon and nitrogen sources, pH, temperature and inoculum size. The putative [FeFe] hydrogenase gene family structure of C. butyricum W5 was also described. Finally, the changes in [FeFe] hydrogenase mRNA expression of C. butyricum W5 during fermentation were monitored, using quantitative real-time Reverse Transcriptase PCR. Statistical analysis showed that both the [FeFe] hydrogenase mRNA expression level and cell growth have a positive relationship with hydrogen production.
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ABSTRACT: In this study, characteristics of biological hydrogen production and microbial distribution were investigated with the wastewater of Tofu manufacturing process. Comparison of hydrogen production was conducted with acid or base pre-treatment of the wastewater. Maximum hydrogen production was acquired with combination of heat and acid treatment. Hydrogen production () and maximum hydrogen production rate () was calculated 661.01 mL and 12.21 mL/g dry wt biomass/hr from the modified Gompartz equation. Most of microbial community was analyzed as Streptococcus sp. from PCR-DGGE experiment of 16S rDNA. It was concluded that most significant microorganism for hydrogen production was Streptococcus gallolyticus sub sp. in this experiment.Journal of Korean Society of Environmental Engineers. 01/2009; 31(2).