Biomedical subjects

Han-Qing Yu

Publications and source records attributed to Han-Qing Yu.

At least 19 recordsLinked to original sources

PubMed2006

Determination of the pore size distribution and porosity of aerobic granules using size-exclusion chromatography.

The pore size distribution and porosity of aerobic granules with different diameters were evaluated using size-exclusion chromatography, in which polyethylene glycols and distilled water were, respectively, used as solute and mobile phase. The porosity of the aerobic granules varied from 68% to 93% and the exclusion limit, expressed as molecular mass, showed a significant difference. For the small-size granules with a diameter of 0.2-0.6mm, molecules greater than 137,000Da could not penetrate the pores, while the exclusion limits of the middle-size granules with a diameter of 0.6-0.9mm and large-size ones with a diameter of 0.9-1.5mm were 76,000 and 29,000Da, respectively. The extracellular polymeric substances of the granules might clog the pores and might be responsible for the reduced porosity. A correlation between the bioactivity and available porosity of the aerobic granules was found. The experimental results show that the size-exclusion chromatography was appropriate for elucidating the pore size distribution and porosity of the aerobic granules.

Aerobiosis↗

PubMed2006

Aerobic granulation with brewery wastewater in a sequencing batch reactor.

Aerobic granular sludge was cultivated in a sequencing batch reactor fed with brewery wastewater. After nine-week operation, stable granules with sizes of 2-7 mm were obtained. With the granulation, the SVI value decreased from 87.5 to 32 mL/g. The granular sludge had an excellent settling ability with the settling velocity over 91 m/h. Aerobic granular sludge exhibited good performance in the organics and nitrogen removal from brewery wastewater. After granulation, high and stable removal efficiencies of 88.7% COD(t), 88.9% NH(4)(+)-N were achieved at the volumetric exchange ratio of 50% and cycle duration of 6h. The average COD(t) and COD(s) of the effluent were 212 and 134 mg/L, respectively, and the average effluent ammonium concentration was less than 14.4 mg/L. Nitrogen was removed due to nitrification and simultaneous denitrification in the inner core of granules.

Bacteria, Aerobic↗

PubMed2006

Substrate consumption and biomass growth of Ralstonia eutropha at various S0/X0 levels in batch cultures.

The biomass growth, substrate consumption and polyhydrobutyrate (PHB) production of Ralstonia eutropha with butyric acid and fructose as the carbon and energy sources at various ratios of initial substrate concentration (S0) to initial biomass concentration (X0) were investigated in this study. Results indicated that the PHB content increased with the increasing S0/X0 ratio. Different substrates exhibited a similar trend for cell growth and substrates consumption with the changing S0/X0 ratio. The specific consumption rates of both butyric acid and fructose increased with the increasing S0/X0 ratio. An S0/X0-dependent kinetic model was modified to describe the kinetics of biomass growth and substrate consumption for R. eutropha. This model was verified with the experimental results from this work and in literature.

Biomass↗

PubMed2006

Analysis of adsorption characteristics of 2,4-dichlorophenol from aqueous solutions by activated carbon fiber.

In this study experiments were conducted to investigate the adsorption of 2,4-dichlorophenol (2,4-DCP) by activated carbon fiber (ACF) activated by static air. With the results of batch experiments at various temperatures, the adsorption isotherms, kinetics and thermodynamics of this adsorption process were evaluated. Four adsorption isotherm models, Langmuir, Freundlich, Redlich-Peterson and Toth equations, were used to fit the experimental data and the results reveal that the adsorption isotherm models fitted the data in the order of: Langmuir>Redlich-Peterson>Toth>Freundlich isotherms. A pseudo second-order adsorption model was better to describe the adsorption data than the pseudo first-order model and the Bangham model at the temperatures tested. The activation energy was calculated to be 40.90 kJ/mol, while the thermodynamic parameters DeltaH and DeltaS were estimated to be -5.82 kJ/mol and 0.07 kJ/(molK), respectively.

Adsorption↗

PubMed2006

Formation of extracellular polymeric substances from acidogenic sludge in H2-producing process.

In this study, the formation of extracellular polymeric substances (EPS) and surface characteristics of an acidogenic sludge in anaerobic H(2)-producing process was investigated. Results show that carbohydrates, proteins, and humic substances were the dominant components in bound EPS (BEPS), while in soluble EPS (SEPS), carbohydrates were the main component. The total content of BEPS initially increased but then kept almost unchanged during fermentation from 25 to 35 h; after that, it slightly decreased. The total content of SEPS increased to 172.5 +/- 0.05 mg C g(-1) volatile suspended solid with the time that increased to 23.5 h, and then rapidly decreased until 43 h; thereafter, it kept almost unchanged. The SEPS had good correlations with the specific H(2) production rate, substrate degradation rate, and specific aqueous products formation rate, but the BEPS seemed to have no such correlations with these specific rates. Results also confirm that part of EPS could be utilized by the H(2)-producing sludge. As the substrate was in short supply, the EPS would be hydrolyzed to sever as carbon and energy source.

Anaerobiosis↗

PubMed2006

Gamma radiation-induced grafting of a cationic monomer onto chitosan as a flocculant.

Grafting of (2-methacryloyloxyethyl) trimethyl ammonium chloride onto chitosan through gamma-radiation in acidic aqueous solutions was achieved for production of a novel flocculant. The grafted copolymer was characterized by Fourier-transform infrared, X-ray powder diffraction and thermogravimetric analysis. The effects of reaction parameters, such as total absorbed dose, dose rate, monomer concentration and temperature, on grafting percentage were investigated. The flocculation capacities of the grafted copolymer were evaluated with 0.25% (w/v) kaolin suspensions using the standard jar test. The results demonstrate the superiority of the grafted copolymer over chitosan as a flocculant.

Cations↗

PubMed2006

Rheological and fractal characteristics of granular sludge in an upflow anaerobic reactor.

The rheological and fractal characteristics of the granular sludge in an upflow anaerobic sludge blanket (UASB) reactor were investigated in this study. The influences of sludge concentration and temperature on the rheological properties of the granular sludge were evaluated, and the Bingham model was adopted to describe its rheology. In addition, image analysis was used to determine the sludge fractal dimension. The results indicate that the UASB granular sludge showed a shear-thinning behavior. The relationships between the limiting viscosity and the sludge concentration, as well as the limiting viscosity and temperature could be respectively modeled using an exponential equation and Arrhenius equation well. The Bingham model was able to adequately describe the rheology of the granular sludge. The fractal dimension of the granular sludge, 2.79+/-0.03, was larger than that of some other aggregates, suggesting that the granular sludge were more compact and denser. Furthermore, the relationship between rheological and fractal properties of the granular sludge could be properly described with the model proposed by Shih et al. [1990. Scaling behavior of the elastic properties of colloidal. Phys. Rev. A 42, 4772-4779].

Anaerobiosis↗

PubMed2006

Biological hydrogen production in a UASB reactor with granules. II: Reactor performance in 3-year operation.

The experiment was conducted to evaluate the performance of an upflow anaerobic sludge blanket (UASB) with granules for H(2) production from a sucrose-rich synthetic wastewater at various substrate concentrations (5.33-28.07 g-COD/L) and hydraulic retention times (HRTs) (3-30 h) for over 3 years. The kinetics of H(2) production was evaluated, and the sludge yield and endogenous decay coefficient of the H(2)-producing granules were estimated to be 0.334 g-VSS/g-COD and 0.004/h, respectively. Based on Gibbs free energy calculations, the formation thermodynamics of caproate, an important aqueous product, were analyzed. Experimental results show that the H(2) partial pressure in biogas decreased with increasing substrate concentration, but was not sensitive to the variation of HRT in a range of 6-22 h. The H(2) production rate increased with increasing substrate concentration, but decreased with increasing HRT. The H(2) yield was in the range of 0.49-1.44 mol-H(2)/mol-glucose. Acetate, butyrate, caporate, and ethanol were the main aqueous products in the reactor, and their concentrations were dependent on both substrate concentration and HRT. An elevated substrate concentration resulted in a shift of fermentation from butyrate- to caporate-type in the reactor and the formation of caproate was dependent on the H(2) partial pressure. The 3-year experimental results demonstrate that H(2) could be produced continuously and stably from the acidogenic-granule-based UASB reactor.

Bacteria, Anaerobic↗

PubMed2006

Biological hydrogen production in a UASB reactor with granules. I: Physicochemical characteristics of hydrogen-producing granules.

Hydrogen-producing granules with an excellent settling ability were cultivated in an upflow anaerobic sludge blanket reactor treating a sucrose-rich synthetic wastewater. The physicochemical characteristics of granules were evaluated in this study. The mature granules had a diameter ranging from 1.0 to 3.5 mm and an average density of 1.036 +/- 0.005 g/mL, whereas they had good settling ability and a high settling velocity of 32-75 m/h. The low ratio of proteins/carbohydrates for the extracellular polymeric substances (EPS) in the granules suggests that carbohydrates rather than proteins, might play a more important role in the formation of the H(2)-producing granules. The contact angle of the mature granules, 54 +/- 2 degrees , was larger than that of the seed sludge (38 +/- 2 degrees ), indicating that the microbial cells in the H(2)-producing granules had higher hydrophobicity. The granules had fractal nature with a fractal dimension of 1.78. Their porosities were in the range of 0-0.70, and increased with increasing granule size. The ratios between the observed and predicted settling velocities by Stokes' law were in a range of 1.00-1.50, and the fluid collection efficiency of the granules ranged from 0 to 0.19, indicating that their permeabilities were lower and that there was little advective flow through their interior. Experimental results also suggest that molecular diffusion appeared to play an important role in the mass transfer through the H(2)-producing granules.

Bacteria, Anaerobic↗

PubMed2006

A generalized model for aerobic granule-based sequencing batch reactor. 1. Model development.

A generalized model was established for simulating an aerobic granule-based sequencing batch reactor (SBR) with considerations of biological processes, reactor hydrodynamics, mass transfer, and diffusion. Methodology of discretization was effectively used forthe model development and calculations. The activated sludge model no.1 was modified to describe the biological processes within the granules. Based on the difference between the calculated and measured results, the model structure was further improved through introducing simultaneous consumption of soluble substrates by storage and heterotrophs growth with a changeable reaction rate. Model calculations were conducted using a MATLAB program. The calculation results show the respective contributions of granules in different size fractions and slices to the overall change of model component concentrations. Moreover, oxygen concentration profiles within granules and oxygen consumption rate varied in one operating cycle. This confirms the applicability and validity of the discretization method and the model structure.

Aerobiosis↗

PubMed2006

A generalized model for aerobic granule-based sequencing batch Reactor. 2. Parametric sensitivity and model verification.

The sensitivity of the effluent chemical oxygen demand, NH4+-N and volatile suspended solids concentrations toward the stoichiometric and kinetic coefficients, oxygen diffusivity, characteristics of granules, and operating parameters was analyzed. With such a parametric sensitivity analysis, calibration of the model, which was established for describing aerobic-granule-based sequencing batch reactor (SBR) in the accompanying paper, was performed by comparing the measured and predicted values for model components. Thereafter, the established model was verified with the experimental results for four aerobic-granule-based SBRs with different granule sizes and fed with different wastewaters. The verification results show that the model established in this work was applicable to simulating and predicting the performance of an aerobic-granule-based SBR.

Aerobiosis↗

PubMed2006

FTIR-spectral analysis of two photosynthetic hydrogen-producing [corrected] strains and their extracellular polymeric substances.

The Fourier transform infrared (FTIR) spectra of the cells of two photosynthetic H(2)-producing strains, Rhodoblastus acidophilus and Rhodobacter capsulatus, as well as their extracellular polymeric substances (EPS), were evaluated. The FTIR spectra of R. capsulatus and its EPS during its cultivation were also recorded. The main peaks in the spectra, including 1,080 cm(-1) (carbohydrates), 1,250 cm(-1) (nucleic acids), 2,830-2,930 cm(-1) (lipids), 1,660-1,535 cm(-1) (Amide I and II of proteins), were observed. The relative heights of these peaks in the spectra of the two strains were different, showing the difference in contents of various components in the cells or EPS. The ratios among the main components in the EPS obtained from the FTIR spectra were in good agreement with those from a conventional quantitative chemical analysis. As an easy, rapid, and direct technique, the FTIR spectroscopy could be used to characterize the components and their relative contents of EPS of photosynthetic bacteria.

Bacterial Proteins↗

PubMed2006

Influence of 2,4-dinitrophenol on the characteristics of activated sludge in batch reactors.

The response of activated sludge characteristics to the presence of 2,4-dinitrophenol (dNP) in batch cultures was investigated in this study. The sludge yield slightly decreased with an increase in dNP concentration. At 10 mg l(-1), or lower, dNP significantly reduced sludge yield and relative specific growth rates (mu/mu0), but didn't substantially affect its relative specific chemical oxygen demand removal rate (q/q0). Presence of dNP at 1-20 mg l(-1) increased the specific oxygen uptake rate of activated sludge, and slightly changed its hydrophobicity. An analysis on inhibition indicated that the reduction in sludge yield in the presence of dNP was mainly attributed to the significant decreased sludge growth, rather than the reduced substrate degradation.

2,4-Dinitrophenol↗

PubMed2006

Anaerobic digestion of cattail with rumen culture in the presence of heavy metals.

The anaerobic digestion of cattail by rumen cultures in the presence of Cu(II), Cd(II) or Cr(VI) was investigated in this study. Three cases were respectively observed for the different metal dosages: promoted cattail degradation and methane production at a low heavy metal concentration, e.g., Cu(II) 2.4 mg/l, Cd(II) 1.6 mg/l, Cr(VI) 4.0 mg/l; reduced cattail degradation efficiency and methane production at a middle metal level; a severe inhibition to the cattail degradation at a high heavy metal dosage. The inhibition kinetics of Cu(II) on the digestion of cattail by rumen cultures was also analyzed and a simplified Andrews equation was used to describe such an inhibition. The inhibition constants for Cu(II) on the degradation of cattail, production of volatile fatty acids and formation of methane were estimated as 7.4, 9.5 and 6.4 mg/l, respectively. Comparative experimental results suggest that the order of toxicity degree of the tested metals on the rumen cultures was: Cd(II) > Cu(II) > Cr(VI).

Anaerobiosis↗

PubMed2006

Stability of sludge flocs under shear conditions: roles of extracellular polymeric substances (EPS).

The roles of extracellular polymer substances (EPS) in the shear stability of aerobic and anaerobic flocs were investigated. Both pH and EDTA concentration had a significant effect on the floc stability. The sludge flocs became much weaker as the solution pH increase to above 10. Addition of 1 mM EDTA or more could cause considerable cell erosion and deflocculation of the anaerobic flocs, whereas more than 3 mM EDTA was needed to show its adverse effect on the stability of aerobic flocs. A fraction of the EPS, around 10 mg/g SS for the aerobic flocs and 15 mg/g SS for the anaerobic flocs, could be extracted by fluid shear when the dispersed mass concentration approached the equilibrium. This suggests that most of the dispersed particles were glued by a small amount of readily-extractable EPS fraction. In addition to the abundance of this EPS fraction, its proteins/carbohydrates ratio, about 0.22:1 for the aerobic flocs and 2.66:1 for the anaerobic flocs, also appeared to be an important factor governing the microbial floc stability. A lower content of the readily-extractable EPS fraction and a lower ratio of proteins/carbohydrates were responsible for the greater stability of microbial flocs. The total content of the EPS, however, did not show a direct correlation with the floc stability. A hypothesis about biological flocs with two distinct structural regions was proposed. The outer part contained dispersible cells loosely entangled by the readily-extractable EPS fraction. This part was layered and would become completely dispersed at an infinite shear intensity. On the other hand, the inner part contains biomass in a stable structure tightly glued by EPS, which could not be dispersed by shear except under unfavorable conditions.

Bacterial Adhesion↗

PubMed2006

Permeabilities of anaerobic CH4-producing granules.

The permeability of anaerobic CH4-producing granules was investigated with both settling and size exclusion chromatography experiments. The experimental results indicate that the two methods could be successfully applied to evaluate the permeability of the CH4-producing granules. An interdependent relationship was found to exist between the two methods for explaining the permeability of the granules. Both methods demonstrate that the porosity of the CH4-producing granules decreased with increasing size, while their settling velocities had an opposite trend. Extracellular polymeric substances yielded by the anaerobic microorganisms might clog the pores within the granules, resulting in a reduction in their porosities. The experimental results also suggest that molecular diffusion appeared to play an important role in the mass transfer in and/or through the granules.

Anaerobiosis↗

PubMed2006

Biosorption of 2,4-dichlorophenol by immobilized white-rot fungus Phanerochaete chrysosporium from aqueous solutions.

The fungus Phanerochaete chrysosporium was immobilized in several polymer matrices: Ca-alginate, Ca-alginate-polyvinyl alcohol (PVA) and pectin, and was then used as a biosorbent for removing 2,4-dichlorophenol (2,4-DCP) in wastewater. Immobilization of P. chrysosporium onto pectin was less efficient than that onto other matrices because of its poor mechanical strength and low adsorption efficiency. Ca-alginate immobilized fungal beads with biocompatibility exhibited good mechanical strength and adsorption efficiency over 60%. Among the different biomass dosages in Ca-alginate immobilized fungal beads, 1.25% (w/v) was the optimum. The adsorption data of 2,4-DCP on the blank Ca-alginate beads, free, and immobilized fungal biomass could be described by the Langmuir and Freundlich isotherms very well. Desorption operation was efficiently completed by using distilled water as eluant, and the desorption efficiency reached 82.16% at an optimum solid/liquid ratio of 14.3. The consecutive adsorption/desorption cycles studies employing the Ca-alginate immobilized fungal beads demonstrated that the immobilized fungal biomass could be reused in five cycles without significant loss of adsorption efficiency and adsorbent weight.

Adsorption↗

PubMed2006

Characterization of extracellular polymeric substances of aerobic and anaerobic sludge using three-dimensional excitation and emission matrix fluorescence spectroscopy.

In this study three-dimensional excitation-emission matrix (EEM) fluorescence spectroscopy was applied to characterize the extracellular polymeric substances (EPS) extracted from aerobic and anaerobic sludge in wastewater treatment. Three fluorescence peaks were identified in EEM fluorescence spectra of the EPS samples. Two peaks were attributed to the protein-like fluorophores, and the third to the humic-like fluorophores. The effects of both pH and EPS concentration were significant on EEM fluorescence spectra of EPS, but the ionic strength had no substantial effect on EEM spectra of the EPS. The differences in the EPS fluorescence parameters, e.g., peak locations, intensities and ratios of various peak intensities, indicate the difference in the chemical structures of the EPS from various origins. EEM spectroscopy was proven to be an appropriate and effective method to characterize the EPS from various origins in wastewater treatment systems.

Aerobiosis↗