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1.
The pilot-scale of two-stage thermophilic (55 °C) for biohythane production from palm oil mill effluent (POME) was operated at hydraulic retention time (HRT) of 2 days and organic loading rate (OLR) of 27.5 gCOD/L⋅d) for first stage and HRT of 10 days and OLR of 5.5 gCOD/L⋅d for second stage. Biohythane production rate was 1.93 L-gas/L⋅d with biogas containing 11% H2, 37% CO2, and 52% CH4. Recirculation of methane effluent mixed with POME at a ratio of 1:1 can control pH in the first stage at an optimal range of 5.0–6.5. Microbial community in hydrogen stage dominated by Thermoanaerobacterium sp., while methane stage dominated by Methanosarcina sp. The H2/CH4 ratio of biohythane was 0.13–0.18 which suitable for vehicle fuel. Biohythane production from POME could be promising cleaner biofuel with flexible and controllable H2/CH4 ratio.  相似文献   

2.
The major objective of dark fermentative H2 production (DFHP) is the significant enhancement of the H2 production performance from economic and engineering perspectives. An up-flow anaerobic sludge blanket (UASB) reactor based on H2-producing granules (HPGs) has been introduced, which results in the efficiency of the H2 production being improved significantly. However, the long start-up period remains a substantial obstacle in the stable operation of the UASB reactor. In the present study, a newly proposed operational strategy was employed to form the HPG using xylose as the feedstock, and this resulted in a successful reduction of the start-up period of the UASB reactor. After the mixed liquor in the continuously stirred tank reactor was transferred to the UASB reactor as a seeding source, the height of the HPG in the UASB reactor was progressively increased. In the UASB reactor, a maximum H2 yield of 2.98 mol H2/mol xylose and a stable H2 production rate of 9.98 L H2/L/h were observed at a hydraulic retention time of 6 h and a substrate concentration of 30 g COD/L. In this novel method, HPGs with an average particle size of 2.32 mm (0.1–4.7 mm) were successfully developed after 120 days and this is the first report documenting the successful formation of HPGs using xylose as feedstock in a UASB reactor.  相似文献   

3.
Biohydrogen production from crude glycerol by immobilized Klebsiella sp. TR17 was investigated in an up-flow anaerobic sludge blanket (UASB) reactor. The reactor was operated under non-sterile conditions at 40C and initial pH 8.0 at different hydraulic retention times (HRTs) (2–12 h) and glycerol concentrations (10–30 g/L). Decreasing the HRT led to an increase in hydrogen production rate (HPR) and hydrogen yield (HY). The highest HPR of 242.15 mmol H2/L/d and HY of 44.27 mmol H2/g glycerol consumed were achieved at 4 h HRT and glycerol concentrations of 30 and 10 g/L, respectively. The main soluble metabolite was 1,3-propanediol, which implies that Klebsiella sp. was dominant among other microorganisms. Fluorescence in situ hybridization (FISH) revealed that the microbial community was dominated by Klebsiella sp. with 56.96, 59.45, and 63.47% of total DAPI binding cells, at glycerol concentrations of 10, 20, and 30 g/L, respectively.  相似文献   

4.
Acid agave bagasse hydrolyzates have been used as a substrate for hydrogen production, however, bioreactors are unstable and with poor performance. Granular biomass could be more successful in producing hydrogen from acid agave bagasse hydrolyzates in comparison with suspended biomass. Thus, this study aimed to evaluate the effect of increasing concentrations of acid agave hydrolyzates on hydrogen production, to compare the hydrogen productivity and stability of granular biomass in an expanded granular sludge bed (EGSB) reactor and suspended biomass in an anaerobic sequencing batch reactor (AnSBR) fed with acid hydrolyzates, and finally to determine the variation of microbial communities established in both bioreactor configurations. In batch tests, the heat-treated inoculum produced hydrogen from acid agave hydrolyzates without observing inhibition at 6.3 g/L of carbohydrates (CHO). This hydrolyzate concentration was used to start up the AnBSR, which reached a productivity of 226 ± 53 mL H2/L⋅d at organic loading rates (OLR) from 3.2 to 4.5 gCHO/L⋅d. The hydrogen production stability index decreased from 0.8 to 0.6 at increasing OLR, and the AnSBR failed at the highest OLR of 5.7 g/L⋅d. The EGSB reactor reached the highest productivity of 361 ± 130 mL H2/L⋅d at an OLR of 7.4 gCHO/L⋅d, but with a low stability index of 0.6. Independently of the bioreactor configuration, microbial communities associated with the production of acetate/lactate were successfully established in both configurations with the prevalence of Lactobacillus spp. A low abundance of typical H2 producers like Clostridium was always observed over the whole period of operation (<10% of the total abundance). In sum, the hydrogen productivity from acid agave hydrolyzates was higher for the EGSB reactor than for the AnSBR, but with much lower stability. The evidence provided by this study suggests the establishment of metabolic pathways for hydrogen production from organic acids.  相似文献   

5.
An innovative multistage anaerobic hythane reactor (MAHR) which combines an internal biofilm (MH) and an external up-flow sludge blanket (MM) was proposed to produce biohythane from wastewater. The effect of pH on its biohythane production and microbial diversity was performed. Results showed that the maximum hydrogen production rate (4.900 L/L/d) was achieved at a pH of 6.0, in comparison to a maximum methane production rate of 10.271 L/L/d at a pH of 6.5. In addition, a suitable hythane (H2/(H2+CH4) of 16.06%) production can be achieved in MH after the initial pH was adjusted from 7.0 to 6.5, and a relatively high methane yield (271.34 mL CH4/gCOD) was obtained in MM. Illumina Miseq sequencing results revealed that decreasing pH led to an increase of the acidogenesis families (Eubacteriaceae, Ruminococcaceae) in MH and an increase of hydrogenotrophic methanogens (Methanobacteriaceae) in MM. The Methanosaetaceae gradually occupied a major portion after a long period of recovery. This work demonstrated the unique advantages of MAHR for the biohythane production under optimal pH conditions.  相似文献   

6.
Dark fermentative hydrogen production by a hot spring culture was studied from different sugars in batch assays and from xylose in continuous stirred tank reactor (CSTR) with on-line pH control. Batch assays yielded hydrogen in following order: xylose > arabinose > ribose > glucose. The highest hydrogen yield in batch assays was 0.71 mol H2/mol xylose. In CSTR the highest H2 yield and production rate at 45 °C were 1.97 mol H2/mol xylose and 7.3 mmol H2/h/L, respectively, and at 37 °C, 1.18 mol H2/mol xylose and 1.7 mmol H2/h/L, respectively. At 45 °C, microbial community consisted of only two bacterial strains affiliated to Clostridium acetobutulyticum and Citrobacter freundii, whereas at 37 °C six Clostridial species were detected. In summary hydrogen yield by hot spring culture was higher with pentoses than hexoses. The highest H2 production rate and yield and thus, the most efficient hydrogen producing bacteria were obtained at suboptimal temperature of 45 °C for both mesophiles and thermophiles.  相似文献   

7.
In this study, controlling an anaerobic microbial community to increase the hydrogen (H2) yield during the degradation of lignocelluosic sugars was accomplished by adding linoleic acid (LA) at low pH and reducing the hydraulic retention time (HRT) of an anaerobic sequencing batch reactor (ASBR). At pH 5.5 and a 1.7 d HRT, the maximum H2 yield for LA treated cultures fed glucose or xylose reached 2.89 ± 0.18 mol mol−1 and 1.94 ± 0.17 mol mol−1, respectively. The major soluble metabolites at pH 5.5 with a 1.7 day HRT differed between the control and LA treated cultures. A metabolic shift toward H2 production resulted in increased hydrogenase activity in both the xylose (13%) and glucose (34%) fed LA treated cultures relative to the controls. In addition, the Clostridia population and the H2 yield were elevated in cultures treated with LA. A flux balance analysis for the LA treated cultures showed a reduction in homoacetogenic activity which was associated with reducing the Bacteriodes levels from 12% to 5% in the glucose fed cultures and 16% to 10% in the xylose fed cultures. Strategies for controlling the homoacetogens and optimal hydrogen production from glucose and xylose are proposed.  相似文献   

8.
Thermoanaerobacterium-rich sludge was used for hydrogen production and phenol removal from palm oil mill effluent (POME) in the presence of phenol concentration of 100–1000 mg/L. Thermoanaerobacterium-rich sludge yielded the most hydrogen of 4.2 L H2/L-POME with 65% phenol removal efficiency at 400 mg/L phenol. Butyric acid and acetic acid were the main metabolites. The effects of oil palm ash, NH4NO3 and iron concentration (Fe2+) on hydrogen production and phenol removal efficiency from POME by Thermoanaerobacterium-rich sludge was investigated using response surface methodology (RSM). The RSM results indicated that the presence of 0.2 g Fe2+/L, 0.3 g/L NH4NO3 and 20 g/L oil palm ash in POME could improved phenol removal efficiency, with predicted hydrogen production and phenol removal efficiency of 3.45 L H2/L-POME and 93%, respectively. In a confirmation experiment under optimized conditions highly reproducible results were obtained, with hydrogen production and phenol removal efficiency of 3.43 ± 0.12 L H2/L-POME and 92 ± 1.5%, respectively. Simultaneous hydrogen production and phenol removal efficiency in continuous stirred tank reactor at hydraulic retention time (HRT) of 1 and 2 days were 4.0 L H2/L-POME with 85% and 4.2 L H2/L-POME with 92%, respectively. Phenol degrading Thermoanaerobacterium-rich sludge comprised of Thermoanaerobacterium thermosaccharolyticum, Thermoanaerobacterium aciditolerans, Desulfotomaculum sp., Bacillus coagulans and Clostridium uzonii. Phenol degrading Thermoanaerobacterium-rich sludge has great potential to harvest hydrogen from phenol-containing wastewater.  相似文献   

9.
Statistical experimental designs were applied for the optimization of medium constituents for hydrogen production from xylose by newly isolated Enterobacter sp. CN1. Using Plackett–Burman design, xylose, FeSO4 and peptone were identified as significant variables which highly influenced hydrogen production. The path of steepest ascent was undertaken to approach the optimal region of the three significant factors. These variables were subsequently optimized using Box–Behnken design of response surface methodology (RSM). The optimum conditions were found to be xylose 16.15 g/L, FeSO4 250.17 mg/L, peptone 2.54 g/L. Hydrogen production at these optimum conditions was 1149.9 ± 65 ml H2/L medium. Under different carbon sources condition, the cumulative hydrogen volume were 1217 ml H2/L xylose medium, 1102 ml H2/L glucose medium and 977 ml H2/L sucrose medium; the maximum hydrogen yield were 2.0 ± 0.05 mol H2/mol xylose, 0.64 mol H2/mol glucose. Fermentative hydrogen production from xylose by Enterobacter sp. CN1 was superior to glucose and sucrose.  相似文献   

10.
Xylose and glucose are the major sugar components of lignocellulosic hydrolysate. This study aims to develop thermophilic hydrogen-producing consortia from eight sediments-rich samples of geothermal springs in Southern Thailand by repeated batch cultivation at 60 °C with glucose, xylose and xylose-glucose mixed substrates. Significant hydrogen production potentials were obtained from thermophilic enriched cultures encoded as PGR and YLT with the maximum hydrogen yields of 241.4 and 231.6 mL H2/g sugarconsumed, respectively. After repeated batch cultivation the hydrogen yield from xylose-glucose mixed substrate of PGR increased to 375 mL H2/g sugarconsumed which was 30% higher than that of YLT (287 mL H2/g sugarconsumed). Soluble metabolites from xylose-glucose mixed substrates were composed mostly of butyric acid (20.6-21.8 mM), acetic acid (7.2-13.5 mM), lactic acid (8.2-11.7 mM) and butanol (4.4-13.0 mM). Denaturing gradient gel electrophoresis (DGGE) profiles illustrated small difference in microbial patterns of PGR enriched with glucose, xylose-glucose mixed substrate and xylose. The dominant populations were affiliated with low G + C content Gram-positive bacteria, Thermoanaerobacterium sp., Thermoanaerobacter sp., Caloramater sp. and Anoxybacillus sp. based on the 16S rRNA gene. Cultivation of the enriched culture PGR in oil palm trunk hydrolysate, the maximum hydrogen yield of 301 mL H2/g sugarconsumed was achieved at hydrolysate concentration of 40% (v/v). At higher concentration to 80% (v/v), the hydrogen fermentation process was inhibited. Therefore, the efficient thermophilic hydrogen-producing consortia PGR has successfully developed and has great potential for production of biohydrogen from mixed sugars hydrolysate.  相似文献   

11.
The production of biohydrogen through dark fermentation of palm oil mill effluent (POME) was evaluated in two-stages of biohydrogen in an anaerobic sequencing batch reactor (ASBR) system using enriched mixed culture for the first time. This study attempts to examine the effect of HRT and its interaction behavior with the solid retention time (SRT), and the sugar consumption. The effluent after discharged from the thermophilic reactor contained 7.61 g/L TC and 22.87 g/L TSS was fed to the secondary mesophilic reactor system. Results indicated that the overall sugar consumption reached 88.62% at the optimum HRT of 12 h with the SRT set to 20 h. The optimum hydrogen yield and HPR in the thermophilic stage were 2.99 mol H2/mol-sugar and 8.54 mmol H2/L·h respectively, while for the mesophilic stage were 1.19 mol H2/mol-sugar and 1.47 mmolH2/L·h respectively. The overall HPR showed an improvement and increase from 8.54 mmol H2/L·h to 10.34 mmol H2/L.h. Microbial community analysis of mixed culture in the two-stage thermophilic (55.0 °C) and mesophilic (37.0 °C) ASBR reactor was dominated by Thermoanaerobacterium sp. based on the PCR-DGGE technique.  相似文献   

12.
Feasibility of hydrogen production from acid and enzymatic oat straw hydrolysates was evaluated in an anaerobic sequencing batch reactor at 35 °C and constant substrate concentration (5 g chemical oxygen demand/L). In a first experiment, hydrogen production was replaced by methane production. Selective pressures applied in a second experiment successfully prevented methane production. During this experiment, initial feeding with glucose/xylose, as model substrates, promoted biomass granulation. Also, the highest hydrogen molar yield (HMY, 2 mol H2/mol sugar consumed) and hydrogen production rate (HPR, 278 mL H2/L-h) were obtained with these model substrates. Gradual substitution of glucose/xylose by acid hydrolysate led to disaggregation of granules and lower HPR and HMY. When the model substrates were completely substituted by enzymatic hydrolysate, the HMY and HPR were 0.81 mol H2/mol sugar consumed and 29.6 mL H2/L-h, respectively. Molecular analysis revealed a low bacterial diversity in the stages with high hydrogen production and vice versa. Furthermore, Clostridium pasteurianum was identified as the most abundant species in stages with a high hydrogen production. Despite that feasibility of hydrogen production from hydrolysates was demonstrated, lower performance from hydrolysates than from model substrates was obtained.  相似文献   

13.
In this study, the feasibility of a continuous two-stage up-flow anaerobic sludge blanket (UASB) reactor system, consisted of thermophilic (55 °C) dark fermentative H2 production and mesophilic (35 °C) CH4 production from coffee drink manufacturing wastewater (CDMW), was tested. A recently proposed operational strategy was used to overcome a major drawback of the long start-up period of the UASB reactor. Firstly, a completely stirred tank reactor (CSTR) was operated for 8 days to prepare seeding. The seed was then directly transferred to the UASB reactor. Microbial aggregation took place in the initial period, and the floc size was gradually increased over time. In UASB reactor, the maximum H2 yield of 2.57 mol H2/mol hexoseadded and a stable H2 production rate of 4.24 L H2/L/h were observed at a hydraulic retention time (HRT) of 6 h and substrate concentration of 20 g Carbo. COD/L. In this novel method using CDMW, thermophilic H2-producing granules with an average particle size of 1.3 mm was successfully developed after 100 days. The more bioenergy recovery was attempted in a post-treatment process using a mesophilic UASB reactor for CH4 production from the H2 fermented effluent. The maximum CH4 yield of 325 mL of CH4/g COD was achieved with removing 93% of the COD at an organic loading rate of 3.5 g COD/L/d. The developed two-stage UASB reactor system achieved biogas conversion by 88.2% (H2 15.2% and CH4 73%) and COD removal by 98%.  相似文献   

14.
Bio-hydrogen production from food waste by anaerobic mixed cultures was conducted in a continuous stirred tank reactor (CSTR). The hydraulic retention time (HRT) was optimized in order to maximize hydrogen yield (HY) and hydrogen production rate (HPR). The maximum hydrogen content (38.6%), HPR (379 mL H2/L. d) and HY (261 mL H2/g-VSadded) were achieved at the optimum HRT of 60 h. The major soluble metabolite products were butyric and acetic acids which indicated a butyrate-acetate type fermentation. Operation of CSTR at HRT 60 h could select hydrogen producing bacteria and eliminate lactic acid bacteria and acetogenic bacteria. The microbial community analyzed by polymerase chain reaction-denaturing gradient gel electrophoresis (PCR-DGGE) revealed that the predominant hydrogen producer was Clostridium sp.  相似文献   

15.
Biohydrogen production from palm oil mill effluent by two-stage dark fermentation and microbial electrolysis was investigated under thermophilic condition. The optimum chemical oxygen demand (COD) concentration and pH for dark fermentation were 66 g·L−1 and 6.5 with a hydrogen yield of 73 mL-H2·gCOD−1. The dark fermentation effluent consisted of mainly acetate and butyrate. The optimum voltage for microbial electrolysis was 0.7 V with a hydrogen yield of 163 mL-H2·gCOD−1. The hydrogen yield of continuous two-stage dark fermentation and microbial electrolysis was 236 mL-H2·gCOD−1 with a hydrogen production rate of 7.81 L·L−1·d−1. The hydrogen yield was 3 times increased when compared with dark fermentation alone. Thermoanaerobacterium sp. was dominated in the dark fermentation stage while Geobacter sp. and Desulfovibrio sp. dominated in the microbial electrolysis cell stage. Two-stage dark fermentation and microbial electrolysis under thermophilic condition is a highly promising option to maximize the conversion of palm oil mill effluent into biohydrogen.  相似文献   

16.
Hydrogen production in a novel sonicated biological hydrogen reactor (SBHR) was investigated and compared with a continuous stirred tank reactor (CSTR). The two systems were operated at a hydraulic retention time (HRT) of 12 h and two organic loading rates (OLRs) of 21.4 and 32.1 g COD/L.d. The average hydrogen production rates per unit reactor volume for the conventional CSTR were 2.6 and 2.8 L/L.d, as compared with 4.8 and 5.6 L/L.d for SBHR, at the two OLRs, respectively. Hydrogen yields of 1.2 and 1.0 mol H2/mol glucose were observed for the CSTR, respectively, while for the SBHR, the hydrogen yields were 2.1 and 1.9 mol H2/mol glucose at the two OLRs, respectively. The hydrogen content in the SBHR’s headspace was higher than that in CSTR by 10% and 31% at OLRs of 21.4 and 32.1 g COD/L.d, respectively. Both glucose conversion efficiency and HAc/HBu ratio in the SBHR were higher than in the conventional CSTR at both OLRs. The biomass yield of about 0.32 g VSS/g COD observed in the CSTR and 0.23 g VSS/g COD in the SBHR substantiate the higher H2 yield in the SBHR. DGGE analysis confirmed the specificity of the microbial hydrogen-producing culture in the SBHR, with two different hydrogen producers (Clostridium sp. and Citrobacter freundii) detected in the SBHR and not detected in the CSTR.  相似文献   

17.
The hydrogen-producing bacterium SP-H2 was isolated from a thermophilic acidogenic reactor inoculated with municipal sewage sludge and processing a carbohydrate-rich simulated food waste. Based on the 16S rRNA gene sequence, the bacterium was identified as Thermoanaerobacterium thermosaccharolyticum. The maximum growth rate was observed at 55–60 °C and pH 7.5. The H2-producing activity of the bacterium was studied using mono-, di- and tri-saccharides related to both hexoses (maltose, glucose, mannose, fructose, lactose, galactose, sucrose, raffinose, cellobiose) and pentoses (xylose and arabinose), as well as using real wastewaters (cheese whey, confectionery wastewater, sugar-beet processing wastewater). The highest H2 yield was observed during dark fermentation (DF) of maltose (1.91 mol H2/mol hexose or 77.8 mmol H2/L). The maximum H2 production rate was observed during DF of xylose (13.3 ml H2/g COD/h) and cellobiose (2.47 mmol H2/L/h). The main soluble metabolite products were acetate, ethanol and butyrate. The acetate concentration had a statistically significant positive correlation with the H2 content in biogas and the specific H2 yield. Based on the results of the correlation analysis, it was tentatively assumed that in the formic acid (mixed-acid) type fermentation, the rate of H2 production was higher than in the butyric acid type fermentation. With regard to real wastewater, cheese whey and confectionery wastewater were distinguished by a higher H2 yield (152 ml H2/g COD) and H2 production rate (0.57 mmol H2/L/h), respectively. The highest concentrations of confectionery wastewater and cheese whey, at which the DF process took place, were 5915 and 7311 mg COD/L, respectively. At the same time, SP-H2 dominated in the microbial community, despite the presence of indigenous microorganisms in wastewater. Thus, T. thermosaccharolyticum SP-H2 is a promising strain for DF of carbohydrate-rich unsterile wastewater under thermophilic conditions.  相似文献   

18.
Batch and continuous modes for bio-hydrogen production by co-digesting cassava starch wastewater with buffalo dung were investigated. Response surface methodology with central composite design was used to optimize the bio-hydrogen production conditions. A hydrogen production potential of 1787 mL H2/L was achieved under optimal conditions of 2.84 g/L of NaHCO3, an initial pH of 6.77 and a total chemical oxygen demand (tCOD)/total nitrogen ratio of 42.36. A continuous stirred tank reactor was operated under the optimum conditions from batch mode to investigate the effects of hydraulic retention time (HRT) of 72, 60 and 48 h on hydrogen production. The highest hydrogen content, hydrogen production rate and hydrogen yield of 33%, 839 mL H2/L.d and 16.90 mL H2/g-CODadded, respectively, were achieved at a HRT of 60 h. The predominant hydrogen producer under the optimal conditions in batch mode was Clostridium sp. while Clostridium sp., Megasphaera sp. and Chloroflexi sp. were observed in the continuous hydrogen production mode at an optimal HRT.  相似文献   

19.
The influence of different inoculum pretreatments (pH and temperature shocks) on mesophilic (37 °C) and thermophilic (55 °C) dark fermentative H2 production from xylose (50 mM) and, for the first time, on the composition of the active microbial community was evaluated. At 37 °C, an acidic shock (pH 3, 24 h) resulted in the highest yield of 0.8 mol H2 mol?1 xylose. The H2 and butyrate yield correlated with the relative abundance of Clostridiaceae in the mesophilic active microbial community, whereas Lactobacillaceae were the most abundant non-hydrogenic competitors according to RNA-based analysis. At 55 °C, Clostridium and Thermoanaerobacterium were linked to H2 production, but only an alkaline shock (pH 10, 24 h) repressed lactate production, resulting in the highest yield of 1.2 mol H2 mol?1 xylose. This study showed that pretreatments differentially affect the structure and productivity of the active mesophilic and thermophilic microbial community developed from an inoculum.  相似文献   

20.
This study aimed to evaluate the effect of the organic loading rate (OLR) (60, 90, and 120 g Chemical Oxygen Demand (COD). L?1. d?1) on hydrogen production from cheese whey and glycerol fermentation as cosubstrates (50% cheese whey and 50% glycerol on a COD basis) in a thermophilic fluidized bed reactor (55 °C). The increase in the OLR to 90 gCOD.L?1. d?1 favored the hydrogen production rate (HPR) (3.9 L H2. L?1. d?1) and hydrogen yield (HY) (1.7 mmol H2. gCOD?1app) concomitant with the production of butyric and acetic acids. Employing 16S rRNA gene sequencing, the highest hydrogen production was related to the detection of Thermoanaerobacterium (34.9%), Pseudomonas (14.5%), and Clostridium (4.7%). Conversely, at 120 gCOD.L?1. d?1, HPR and HY decreased to 2.5 L H2. L?1. d?1 and 0.8 mmol H2. gCOD?1app, respectively, due to lactic acid production that was related to the genera Thermoanaerobacterium (50.91%) and Tumebacillus (23.56%). Cofermentation favored hydrogen production at higher OLRs than cheese whey single fermentation.  相似文献   

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