Continuous Flow Stirred Tank Reactor Research Articles

Study of dynamics of glucose-glucose oxidase-ferricyanide reaction

This work is focused on dynamics of the glucose-glucose oxidase-ferricyanide enzymatic reaction with or without sodium hydroxide in a continuous-flow stirred tank reactor (CSTR) and in a batch reactor. This reaction exhibits pH-variations having autocatalytic character and is reported to provide nonlinear dynamic behavior (bistability, excitability). The dynamical behavior of the reaction was examined within a wide range of inlet parameters. The main inlet parameters were the ratio of concentrations of sodium hydroxide and ferricyanide and the flow rate. In a batch reactor we observed an autocatalytic drop of pH from slightly basic to medium acidic values. In a CSTR our aim was to find bistability in the presence of sodium hydroxide. However, only a basic steady state was found. In order to reach an acidic steady state, we investigated the system in the absence of sodium hydroxide. Under these conditions the transition from the basic to the acidic steady state was observed when inlet glucose concentration was increased.

Age distribution and the degree of mixing in continuous flow stirred tank reactors

New development of mean age theory is discussed for quantitative analysis of mixing and age distribution in steady continuous flow stirred tank reactors. A new relationship between the moments of age and the moments of residence time are derived. With this new relationship the variance of residence time distribution can be computed much more efficiently and accurately. The relationships of three existing variances of age are described and a new set of variances and the degree of mixing are defined. The theory is used to characterize mixing performance in a CFSTR with different layouts of an inlet and an outlet. Mean age and higher moments of age in the reactors are obtained from CFD solutions of their steady transport equations. The spatial distribution of mean age reveals details of the spatial non-uniformity in mixing. Variances of age and the degree of mixing discussed by Danckwerts and Zwietering are computed for the first time in the literature for non-ideal stirred tank reactors. It is found that although these measures are useful, certain key features in non-uniform mixing are not reflected accurately. Results show that the new set of variances and the degree of mixing more accurately characterize the non-uniform mixing in the reactors.

폐미역을 이용한 생물흡착 시스템별 중금속 제거 효율 평가

폐미역을 이용한 생물흡착제의 중금속 제거능력을 조사하기 위해 lab-scale의 생물흡착시스템에서 최적조건을 구명하고, lab-scale의 생물흡착시스템의 최적조건하에서 large-scale PBCC 시스템의 중금속 제거능력을 조사하였다. Lab-scale 생물흡착시스템별 중금속 제거능력은 PBCC보다 CSTR이 뛰어났지만 CSTR은 폐수유입속도가 48 L/day이상에서 완전혼합상태를 유지하지 못하여 안정적인 운전이 가능한 PBCC가 적합하였다. Cu용액의 유입속도 및 농도별 Cu 제거능력은 유입속도 12 L/day 및 유입농도 10 mg/L일 때 Cu용액 처리량이 가장 뛰어났으나 경제적인 부분을 검토한 결과 유입속도 24 L/day 및 유입농도 100 mg/L가 적절할 것으로 판단되었다. 처리단계별 Cu 제거능력은 컬럼을 연속식으로 배열하는 것이 Cu 제거효율이 높았다. 중금속 종류별 제거능력은 Pb, Cr의 처리효율이 높았고 Cu용액 이외의 다른 중금속 용액들도 Cu와 동등한 수준 이상의 처리효율을 나타내었다. Lab-scale의 PBCC 시스템을 27배 규모로 scale-up한 large-scale PBCC 시스템의 Cu 제거능력은 138 L로 lab-scale의 5 L와 비교하였을 때 동등한 수준을 유지하였다. 따라서 중금속 처리를 위한 최적 폐미역 활용 생물흡착시스템은 PBCC 시스템인 것으로 판단되나, 실제 중금속 폐수에 본 최적시스템을 적용하기 위해서는 중금속 폐수 특성에 따른 적용성 연구가 추가로 진행되어야 할 것으로 판단된다. BACKGROUND: Heavy-metal pollution represents an important environmental problem due to the toxic effects of metals, and their accumulation throughout the food chain leads to serious ecological and health problems. METHODS AND RESULTS: Optimum conditions in continuous-flow stirred tank reactor (CSTR) and packedbed column contactor (PBCC) using brown seaweed biosorbent were investigated. Under optimum conditions from both lab-scale biosorbent systems, removal efficiency of copper (Cu) in a large-scale PBCC system was investigated. Removal capacity of Cu using brown seaweed biosorbent in a lab-scale CSTR system was higher than that in a lab-scale PBCC system. On the other hand, over 48 L/day of flow rate in Cu solution, removal efficiency of Cu in a lab-scale PBCC system was higher than that in a lab-scale CSTR system. Optimum flow rate of Cu was 24 L/day, optimum Cu solution concentration was 100 mg/L. Removal capacity of Cu at different stages was higher in the order of double column biosorption system > single column biosorption system. Under different heavy metals, removal capacities of heavy metal were higher in the order of Pb > Cr > Ni > Mn <TEX>${\geq}$</TEX> Cu <TEX>${\geq}$</TEX> Cd <TEX>${\fallingdotseq}$</TEX> Zn <TEX>${\geq}$</TEX> Co. Removal capacity of Cu was 138 L in a large-scale PBCC system. Removal capacity of Cu a large-scale PBCC system was similar with in a lab-scale PBCC system. CONCLUSION(s): Therefore, PBCC system using brown seaweed biosorbent was suitable for treating heavy metal wastewater.

Prediction of Tracer Concentration and Mixing in CFSTRs with Mean Age Distribution

Three-dimensional time-dependent tracer concentration distributions in nonideal continuous flow stirred tank reactors with pulse input are studied computationally. Both the steady transport equation for mean age and the time-dependent transport equation for tracer concentration are solved. It is found that the time-dependent tracer concentration history can be divided into two stages: an initial stage, in which the concentration is highly location-dependent, and a stationary stage, in which the concentration decays with a location-independent, constant exponential rate. This rate is found to be the inverse of the volume-averaged mean age. The length of the initial stage is found to be very short, on the same order of magnitude as the batch blend time. It is also found that the scaled concentration distribution in the stationary stage is almost identical to the scaled mean age distribution. The spatial and temporal concentration distribution in the stationary stage can be determined once the initial stage and the mean age solution are obtained. Thus, the CPU time required is orders of magnitude smaller than that for the full time integration of the unsteady concentration equation. With the solution of tracer concentration distribution known, mixing time and other quantitative measures for the tracer mixing can be easily calculated.

Investigations of different chemiluminescent peaks in H2O2–SCN−–Cu2+–OH−–luminol flow system

In the H2O2-SCN(-) -Cu(2+)-OH(-)-luminol oscillatory system of chemiluminescence, the effects of the ingredient concentrations, temperature, flow rate and complexing agent on the oscillatory dynamics were investigated in a continuous-flow stirred tank reactor (CSTR). The dynamical structure of two peaks during a period was discussed in detail. By addition of EDTA to the oscillating system, the peak I height decreased sharply while the peak II height was little affected, and the period kept constant. This may be due to the fast reaction between Cu(II) and EDTA and the highly stable complex Cu(II)-EDTA. From the experimental study and mechanism analysis, the chemiluminescent peak I corresponds to Cu(II) → Cu(I) transformation and the peak II corresponds to the Cu(I) → Cu(II) transformation process. The key species involving in the two-transformation process are inferred to be superoxide radical and hydroxyl radical.

Continuous biohydrogen production from diluted molasses in an anaerobic contact reactor

An anaerobic contact reactor (ACR) system comprising a continuous flow stirred tank reactor (CSTR) with settler to decouple the hydraulic retention time (HRT) from solids retention time (SRT) was developed for fermentative hydrogen production from diluted molasses by mixed microbial cultures. The ACR was operated at various volumetric loading rates (VLRs) of 20–44 kgCOD·m−3·d−1 with constant HRT of 6 h under mesophilic conditions of 35°C. The SRT was maintained at about 46–50 h in the system. At the initial VLR of 20 kgCOD·m−3·d−1, the hydrogen production rate dropped from 22.6 to 1.58 L·d−1 as the hydrogen was consumed by the hydrogentrophic methanogen. After increasing the VLR to 28 kgCOD·m−3·d−1 and discharging the sludge for 6 consecutive times, the hydrogentrophic methanogens were eliminated, and the hydrogen content reached 36.4%. As the VLR was increased to 44 kgCOD·m−3·d−1, the hydrogen production rate and hydrogen yield increased to 42.1 L·d−1 and 1.40 mol H2·molglucose-consumed-1, respectively. The results showed that a stable ethanoltype fermentation that favored hydrogen production in the reactor was thus established with the sludge loading rate (SLR) of 2.0–2.5 kgCOD·kgMLVSS−1·d−1. It was found that the ethanol increased more than other liquid fermentation products, and the ethanol/acetic acid (mol/mol) ratio increased from 1.27 to 2.45 when the VLR increased from 28 to 44 kgCOD·m−3·d−1, whereas the hydrogen composition decreased from 40.4% to 36.4%. The results suggested that the anaerobic contact reactor was a promising bioprocess for fermentative hydrogen production.

Effect of pH, ORP and Influent COD on Hydrogen Content in Fermentative Hydrogen Production

Fermentative hydrogen production was carried out using a continuous flow stirred tank reactor (CSTR) for the investigation of the hydrogen content in the biogas. Molasses was used as the substrate; hydraulic retention time (HRT) was 6 h; the temperature was in the range of 35±1 .It was showed that hydrogen content increased from 38% to 59% when pH decreased from 5 to 4.6 with oxidation-reduction potential (ORP) increased from -420 mV to -380 mV. The hydrogen content dropped from 50% to 30% as influent COD was improved from4000 mg/L to 6000 mg/L. Hydrogen content increased to 35% when influent COD was improved to 7000 mg/L, however decreased to 25% when influent COD was 8000 mg/L. Ethanol in terminal products is accompanied with hydrogen production but with lower hydrogen content. Butyric acid indicates higher hydrogen content than ethanol.

Methanogenic pathway and community structure in a thermophilic anaerobic digestion process of organic solid waste

The methanogenic pathway and microbial community in a thermophilic anaerobic digestion process of organic solid waste were investigated in a continuous-flow stirred-tank reactor using artificial garbage slurry as a feedstock. The decomposition pathway of acetate, a significant precursor of CH(4) and a key intermediate metabolite in the anaerobic digestion process, was analyzed by using stable isotopes. A tracer experiment using (13)C-labeled acetate revealed that approximately 80% of the acetate was decomposed via a non-aceticlastic oxidative pathway, whereas the remainder was converted to methane via an aceticlastic pathway. Archaeal 16S rRNA analyses demonstrated that the hydrogenotrophic methanogens Methanoculleus spp. accounted for >90% of detected methanogens, and the aceticlastic methanogens Methanosarcina spp. were the minor constituents. The clone library targeting bacterial 16S rRNA indicated the predominance of the novel Thermotogales bacterium (relative abundance: ~53%), which is related to anaerobic acetate oxidizer Thermotoga lettingae TMO, although the sequence similarity was low. Uncultured bacteria that phylogenetically belong to municipal solid waste cluster I were also predominant in the microflora (~30%). These results imply that the microbial community in the thermophilic degrading process of organic solid waste consists exclusively of unidentified bacteria, which efficiently remove acetate through a non-aceticlastic oxidative pathway.

Modeling Simultaneous Nitrification–Denitrification Process in an Activated Sludge Continuous Flow Stirred-Tank Reactor: System Optimization and Sensitivity Analysis

Biological nitrogen removal from municipal wastewater is an important issue. Nitrogen removal by simultaneous nitrification–denitrification (SND) process has drawn much attention in the past few years because of potential reduction in capital and operating costs. Performance of SND process treatment in a continuous flow stirred-tank reactor was examined using Activated Sludge Model No. 1. Individual biomass cells were taken to be suspended with dissolved oxygen (DO) equally available to every cell without considering any floc formation. The combination of operating DO concentration and solids retention time were key factors for effective nitrogen removal. Simulation output predicted significant nitrogen reduction at 0.4 mg/L operating DO and 15-day solids retention time (SRT). The effect of additional operating conditions on nitrogen removal was evaluated. As sufficient electron donor was necessary for sustaining denitrification, the influent biodegradable COD to total kjeldahl nitrogen ratio had significant effect on overall nitrogen reduction and was effective when such ratio was ≥10. Neither hydraulic retention time nor recycle ratio (R) had any notable effect on nitrogen removal. Stochastic simulations considered the natural variability of kinetic and stoichiometric parameters in Activated Sludge Model No. 1 and used Monte Carlo analysis to assess the reliability of SND system operated at optimum conditions. A sensitivity analysis was performed with the stochastic simulation results to identify those model parameters significantly affecting process performance. Predictions from such analysis were found to be in close agreement with previous experimental results and can be used to look into the possibility of converting extended aeration-type activated sludge processes into potential biological nitrogen removal system.

ChemInform Abstract: Sustained and Damped Oscillations in the Permanganate-Hydroxylamine Reaction in a Continuous-Flow Stirred Tank Reactor.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

Trichloroethene and cis-1,2-dichloroethene concentration-dependent toxicity model simulates anaerobic dechlorination at high concentrations. II: continuous flow and attached growth reactors.

A model that was used to describe toxicity from high concentrations of chlorinated aliphatic hydrocarbons (CAHs) on reductively dechlorinating cultures in batch reactors (Sabalowsky and Semprini (in press)) was extended here to simulate observations in continuous flow suspended and attached growth reactors. The reductively dechlorinating anaerobic Evanite subculture (EV-cDCE) was fed trichloroethene (TCE) and excess electron donor to accumulate cis-1,2-dichloroethene (cDCE) in a continuous flow stirred tank reactor (CFSTR); and an attached growth recirculating packed column (RPC). A concentration-dependent toxicity model used to simulate the results of batch reactors in part I (Sabalowsky and Semprini (in press) Biotechnol Bioeng) also simulated well the observations for the CFSTR and RPC growth modes. The toxicity model incorporates cDCE and TCE toxicity coefficients that directly increase the cell decay coefficient in proportion with cDCE and TCE concentrations. Simulated estimates of the cDCE and TCE toxicity coefficients indicate reductively dechlorinating cells are most sensitive to high concentrations of cDCE and TCE in batch-fed growth, followed by CFSTR, with attached growth being least sensitive. The greater toxicity of TCE than cDCE, and ratio of the modeled toxicity coefficients, agrees with previously proposed models relating toxicity to partitioning in the cell wall (K(M/B)), proportional to octanol-water partitioning (K(OW)) coefficients.

Enhancement of anaerobic hydrogen production by iron and nickel

The effects of iron and nickel on hydrogen (H 2) production were investigated in a glucose-fed anaerobic Continuous Flow Stirred Tank Reactor (ACSTR). Both iron and nickel improved the reactor performance and H 2 production was enhanced by 71% with the sole iron or nickel supplementation. In all cases, H 2 production yield was increased by lowering both ethanol and total metabolites production and increasing butyrate production. Furthermore, iron and nickel slightly increased biomass production while glucose degradation decreased with the supplementation of nickel. Dynamic changes in bacterial composition as analyzed by 16S rRNA gene-targeted denaturing gradient gel electrophoresis (DGGE) revealed that hydrogen was produced mainly by Clostridium butyricum strains and that nickel addition decreased the microbial diversity.

Temperature-Induced Bifurcations in the Cu(II)-Catalyzed and Catalyst-Free Hydrogen Peroxide-Thiosulfate Oscillating Reaction

We study the oxidation dynamics of thiosulfate ions by hydrogen peroxide in the presence of trace amounts of copper(II) using the reaction temperature as a control parameter in a continuous flow stirred tank reactor. The system displays period-doubling, aperodic, and mixed-mode oscillations at different temperatures. We are able to simulate these complex dynamics with a model proposed by Kurin-Csorgei et al. The model suggests that the Cu(2+)-containing term is not essential for the observed oscillations. We find small-amplitude and high-frequency oscillations in the catalyst-free experimental system. The reaction between H(2)O(2) and S(2)O(3)(2-) contains the core mechanism of the H(2)O(2)-S(2)O(3)(2-)-Cu(2+) and H(2)O(2)-S(2)O(3)(2-)-SO(3)(2-) oscillatory systems, while the Cu(2+) and SO(3)(2-) modulate the feedback loops so as to strengthen the oscillatory dynamics.

The Succession of Microbial Community in CSTR Hydrogen Production System

The continuous flow stirred tank reactor (CSTR) is used for the experimental device. We discuss that the succession of climax community of the ecosystem according to composition of terminal liquid products and gas products, and the effect of the change of ‘causing factor’—organic loading rate(OLR) on the structure of microbial communities in the CSTR system, and the feedback regulation among the ‘following factors’( pH value, ORP value) and structure of microbial community. The community succession law restricted by OLR was studied from the angle of community dynamic: when OLR increases from 14 kg/m3•d to 20 kg/m3•d, the content of ethanol and acetic acid increased to about 60% ～ 80% of total terminal liquid products; hydrogen is started to product at the 18th day and stabilized at about 5 L/d gradually ,the maximum was 6.155L/d; the pH value and ORP value are 4.0～4.3 and -370～-400mv stable respectively, which indicated that ethanol-type fermentation microbial community replaced mixed acid fermentation microbial community.

Multiple Equilibria in Complex Chemical Reaction Networks: Semiopen Mass Action Systems

In two earlier articles, we provided sufficient conditions on (mass action) reaction network structure for the preclusion of multiple positive steady states in the context of what chemical engineers call the continuous flow stirred tank reactor. In such reactors, all species are deemed to be present in the effluent stream, a fact which played a strong role in the proofs. When certain species are deemed to be entrapped within the reactor, the questions that must be asked are more subtle, and the mathematics becomes substantially more difficult. Here we extend results of the earlier papers to semiopen reactors and show that very similar results obtain, provided that the network of chemical reactions satisfies certain weak structural conditions; weak reversibility is sufficient but not necessary.

Stable coexistence of two Caldicellulosiruptor species in a de novo constructed hydrogen-producing co-culture

BackgroundMixed culture enrichments have been used frequently for biohydrogen production from different feedstock. In spite of the several advantages offered by those cultures, they suffer poor H2 yield. Constructing defined co-cultures of known H2 producers may offer a better performance than mixed-population enrichments, while overcoming some of the limitations of pure cultures based on synergies among the microorganisms involved.ResultsThe extreme thermophiles Caldicellulosiruptor saccharolyticus DSM 8903 and C. kristjanssonii DSM 12137 were combined in a co-culture for H2 production from glucose and xylose in a continuous-flow stirred tank reactor. The co-culture exhibited a remarkable stability over a period of 70 days under carbon-sufficient conditions, with both strains coexisting in the system at steady states of different dilution rates, as revealed by species-specific quantitative PCR assays. The two strains retained their ability to stably coexist in the reactor even when glucose was used as the sole growth-limiting substrate. Furthermore, H2 yields on glucose exceeded those of either organism alone under the same conditions, alluding to a synergistic effect of the two strains on H2 production. A maximum H2 yield of 3.7 mol (mol glucose)-1 was obtained by the co-culture at a dilution rate of 0.06 h-1; a higher yield than that reported for any mixed culture to date. A reproducible pattern of population dynamics was observed in the co-culture under both carbon and non-carbon limited conditions, with C. kristjanssonii outgrowing C. saccharolyticus during the batch start-up phase and prevailing at higher dilution rates. A basic continuous culture model assuming the ability of C. saccharolyticus to enhance the growth of C. kristjanssonii could mimic the pattern of population dynamics observed experimentally and provide clues to the nature of interaction between the two strains. As a proof, the cell-free growth supernatant of C. saccharolyticus was found able to enhance the growth of C. kristjanssonii in batch culture through shortening its lag phase and increasing its maximum biomass concentration by ca. 18%.ConclusionsThis study provides experimental evidence on the stable coexistence of two closely related organisms isolated from geographically-distant habitats under continuous operation conditions, with the production of H2 at high yields. An interspecies interaction is proposed as the reason behind the remarkable ability of the two Caldicellulosiruptor strains to coexist in the system rather than only competing for the growth-limiting substrate.

Extended continuous-flow stirred-tank reactor (ECSTR) as a simple model of life under thermodynamically open conditions

A continuous-flow stirred-tank reactor (CSTR) is a vital tool for investigating the nonlinear dynamics of chemical systems. This report proposes an extended CSTR (ECSTR) inspired by active and passive transports through a closed membrane in living systems. In addition to the externally-controlled flow in a conventional CSTR, we introduce passive diffusion through a membrane into the ECSTR. This extension allows us to control the chemical dynamics with a larger parameter-dimension. Numerical analyses show that the ECSTR can expand an oscillatory region in the parameter space and can convert a non-oscillatory chemical system to an oscillatory system.

Modeling Integrated Fixed‐Film Activated Sludge and Moving‐Bed Biofilm Reactor Systems I: Mathematical Treatment and Model Development

A mathematical model for integrated fixed-film activated sludge (IFAS) and moving-bed biofilm reactor wastewater treatment processes was developed. The model is based on theoretical considerations that include simultaneous diffusion and Monod-type reaction kinetics inside the biofilm, competition between aerobic autotrophic nitrifiers, non-methanol-degrading facultative heterotrophs, methanol-degrading heterotrophs, slowly biodegradable chemical oxygen demand, and inert biomass for substrate (when appropriate) and space inside the biofilm; and biofilm and suspended biomass compartments, which compete for both the electron donor and electron acceptor. The model assumes identical reaction kinetics for bacteria within suspended biomass and biofilm. Analytical solutions to a 1-dimensional biofilm (assuming both zero- and first-order kinetics) applied to describe substrate flux across the biofilm surface are integrated with a revised and expanded matrix similar to that presented as the International Water Association (London, United Kingdom) Activated Sludge Model Number 2d (ASM2d) stoichiometric and kinetic matrix. The steady-state mathematical model describes a continuous-flow stirred-tank reactor.

Biogas Plasticization Coupled Anaerobic Digestion: Continuous Flow Anaerobic Pump Test Results

In this investigation, the Anaerobic Pump (TAP) and a conventional continuous flow stirred tank reactor (CFSTR) were tested side by side to compare performance. TAP integrates anaerobic digestion (AD) with biogas plasticization-disruption cycle to improve mass conversion to methane. Both prototypes were fed a "real world" 50:50 mixture of waste-activated sludge (WAS) and primary sludge and operated at room temperature (20 degrees Celsius). The quantitative results from three steady states show TAP peaked at 97% conversion of the particulate COD in a system hydraulic residence time (HRT) of only 6 days. It achieved a methane production of 0.32 STP cubic meter CH(4) per kilogram COD fed and specific methane yield of 0.78 m(3) CH(4) per cubic meter per day. This was more than three times the CFSTR specific methane yield (0.22 m(3) CH(4) per cubic meter per day) and more than double the CFSTR methane production (0.15 m(3) CH(4) per kilogram COD fed). A comparative kinetics analysis showed the TAP peak substrate COD removal rate (R (o)) was 2.24 kg COD per cubic meter per day, more than three times the CFSTR substrate removal rate of 0.67 kg COD per cubic meter per day. The three important factors contributing to the superior TAP performance were (1) effective solids capture (96%) with (2) mass recycle and (3) stage II plasticization-disruption during active AD. The Anaerobic Pump (TAP) is a high rate, high efficiency-low temperature microbial energy engine that could be used to improve renewable energy yields from classic AD waste substrates like refuse-derived fuels, treatment plant sludges, food wastes, livestock residues, green wastes and crop residuals.

Quantitative fluorescent in-situ hybridization: a hypothesized competition mode between two dominant bacteria groups in hydrogen-producing anaerobic sludge processes

Two hydrogen-producing continuous flow stirred tank reactors (CSTRs) fed respectively with glucose and sucrose were investigated by polymerase chain reaction-denatured gradient gel electrophoresis (PCR-DGGE) and fluorescent in-situ hybridization (FISH). The substrate was fed in a continuous mode decreased from hydraulic retention time (HRT) 10 hours to 6, 5, 4, 3, and 2 hours. Quantitative fluorescent in-situ hybridization (FISH) observations further demonstrated that two morphotypes of bacteria dominated both microbial communities. One was long rod bacteria which can be targeted either by Chis150 probe designed to hybridize the gram positive low G + C bacteria or the specific oligonucleotide probe Lg10-6. The probe Lg10-6, affiliated with Clostridium pasteurianum, was designed and then checked with other reference organisms. The other type, unknown group, which cannot be detected by Chis150 was curved rod bacteria. Notably, the population ratios of the two predominant groups reflected the different operational performance of the two reactors, such as hydrogen producing rates, substrate turnover rates and metabolites compositions. Therefore, a competition mode of the two dominant bacteria groups was hypothesized. In the study, 16S rRNA-based gene library of hydrogen-producing microbial communities was established. The efficiency of hydrogen yields was correlated with substrates (glucose or sucrose), HRT, metabolites compositions (acetate, propionate, butyrate and ethanol), thermal pre-treatment (seed biomass was heated at 100 degrees C for 45 minutes), and microbial communities in the bioreactor, not sludge sources (municipal sewage sludge, alcohol-processing sludge, or bean-processing sludge). The designed specific oligonucleotide probe Lg10-6 also provides us a useful and fast molecular tool to screen hydrogen-producing microbial communities in the future research.