Ay Su

Dark fermentation on biohydrogen production: pure culture.

Biohydrogen is regarded as an attractive future clean energy carrier due to its high energy content and environmental-friendly conversion. While biohydrogen production is still in the early stage of development, there have been a variety of laboratory- and pilot-scale systems developed with promising potential. This work presents a review of literature reports on the pure hydrogen-producers under anaerobic environment. Challenges and perspective of biohydrogen production with pure cultures are also outlined.

Dissolved organic matter with multi-peak fluorophores in landfill leachate.

Dissolved organic matter (DOM) sampled from municipal landfill leachate of different ages with/without anoxic or aerobic treatment, was intensively fractionated via size exclusion chromatography (SEC) and hydrophobic resins, and was studied with fluorescence excitation and emission matrix (EEM). Six fluorophores with multiple EEM peaks (fluorophore A-F) were identified based on the collected EEM spectra and validated by bi-variate analysis, principal component analysis, and parallel factor analysis, as follows (excitation wavelength Ex and emission wavelength Em): (Ex 240, 310, 360 nm, Em 460 nm), (Ex 220, 280 nm, Em 340 nm), (Ex 220, 270 nm, Em 300 nm), (Ex 220, 280 nm, Em 360 nm), (Ex 230, 320 nm, Em 420 nm) and (Ex 220, 310 nm, Em 400 nm). The spectral characteristics of these fluorophores were discussed using fractional EEM and apparent molecular weight (AMW) data obtained via SEC analysis. The triple peak flurophore A was pointed at a hydrophobic acid or hydrophobic neutral compound with a pyrenyl functional group of AMW 2500-3500 Da, which displayed an excitation wavelength at 360 nm and a fluorescence intensity ratio of 6.70(+/-1.79):1.70(+/-0.41):1 (fluorescent intensities of Ex 240:Ex 310:Ex 360 nm at Ex 460 nm). This compound is observed to be refractory in landfilling or in anoxic/aerobic treatments, and is specific to this leachate contamination. This paper revealed that the coupling of SEC and EEM can be useful to track the fluorescent DOM fraction in landfill leachate.

Characteristics of rapidly formed hydrogen‐producing granules and biofilms

The physicochemical and microbiological characteristics of rapidly formed hydrogen‐producing granules and biofilms were evaluated in the present study. Microbial species composition was examined using the 16S rDNA‐based separation and sequencing techniques, and spatial distribution and internal structure of microbial components were evaluated by examining the confocal laser scanning microscope (CLSM) images. Phylogenetic analysis indicated that a pure culture of Clostridium pasteurianum‐like bacterium (98% similarity) was found in microbial community of granules and biofilms. It is postulated that containing such a species favored the rapid immobilization of hydrogen‐producing culture. Manure granules and biofilms secreted 24–35 mg extracellulous proteins and 142–175 mg extracellulous polysaccharides in each gram of culture (in VSS). Such a high productivity of extracellulous polymers (ECP), a bio‐glue to facilitate cell‐to‐cell and/or cell‐to‐substratum interaction, may work as the driving forces for the immobilization of C. pasteurianum. As abundant proteins were noted in the granule cores, it can be derived that rapid formation of the hydrogen‐producing granules could be due to the establishment of precursor protein‐rich microbial nuclei. Biotechnol. Bioeng.

Boiling of methanol and HFE-7100 on heated surface covered with a layer of mesh

This work has experimentally elucidated the effects of boiling saturated methanol or saturated and subcooled HFE-7100 on heated surface covered with a layer of mesh. The whole boiling curves were constructed. The fine mesh layer enhances the heat transfer efficiency of nucleate boiling at low wall superheats. Nevertheless, the presence of mesh would deteriorate the efficiency of film boiling mode and reduce both, the critical heat flux (CHF) and minimum heat flux (MHF). Comparisons between boiling of methanol and that of HFE-7100 were made.

Dissolved organic matter and estrogenic potential of landfill leachate

The estrogenic potentials of leachate samples collected at Laogang Sanitary Landfill in Shanghai, China were measured together with the associated dissolved organic matter (DOM) in leachate samples. Over 99% of the DOM in fresh leachate was removed upon 3-7 years of landfill, leaving only DOM with strong fluorescent activity. Anoxic or aerobic treatment of landfill leachate can further degrade DOM of MW<300 Da and transform those with fluorescent activity of MW>10(5) Da to those of 2000-10(5) Da. Neither landfilling nor storage in anoxic pond effectively removed estrogenic potential of leachate. Fractionation test revealed that residual organic matters of MW 3000-14000 Da and of <600 Da with high UV254 contributed most of the estrogenic activities in leachate. Aerobic SBR treatment considerably reduced the estrogenic potential of these organic matters in leachate.

Model for Sludge Cake Drying Accounting for Developing Cracks

This study analyzed convective drying of wastewater sludge cakes with three-dimensional cake structures probed using an X-ray microcomputerized tomography scanner (micro-CT). Crack development and surface skin layers were utilized in model development. The drying cake had an extremely heterogeneous structure, with detail presented by constructed three-dimensional, tetrahedral volumetric grids. Drying modeling was conducted numerically by solving the conservation equations with assigned boundary conditions at so-constructed complicated volumetric structural model.

Spreading dynamics of power-law fluid droplets

This paper aims at providing a summary of the theoretical models available for non-Newtonian fluid spreading dynamics. Experimental findings and model predictions for a Newtonian fluid spreading test are briefly reviewed. Then how the complete wetting and partial wetting power-law fluids spread over a solid substrate is examined. The possible extension of Newtonian fluid models to power-law fluids is also discussed.

Prediction and Experimental Validation of In-Plane Current Distribution Between Channel and Land in a PEFC

A nonisothermal, two-phase model for polymer electrolyte fuel cells is validated against the experimental data of in-plane current density profiles. Overall, good agreement is achieved between predicted and measured current density distributions between the channel and land with submillimeter resolution. Numerical simulations clearly show that the in-plane current profile results from the interplay between the ohmic control and mass transport control, both of which depend strongly on the two-phase water transport along the in-plane direction. Under relatively dry and large stoichiometric conditions, the current density peak is seen to shift from under the land to under the channel with increasing average current density, signifying control by membrane resistance at low current densities but by oxygen diffusion at high current densities. Finally, the validated model reveals the dramatic influence of the channel/land width and gas diffusion layer compression on the in-plane current density profile, thus underscoring the necessity to match these two key parameters in experimental measurements of in-plane current distribution.

Estrogenic activity of fractionate landfill leacahte.

Dissolved organic matter (DOM) in leachate samples collected at Laogang Sanitary Landfill in Shanghai, China were fractionated using size exclusion chromatography and were characterized using estrogen receptor-alpha competitor screening assay as toxicity activity index. The estrogen activity of leachate was determined mainly by the hydrophobic acid DOM with moderate MW (3000-14,000 Da) and low MW (<630 Da) and with high aromaticity and fluorophores of possibly pyrenyl characteristics. Landfilling for up to seven years or oxic storage for one month degraded a few of these estrogens. Aerobic SBR treatments effectively degraded the hydrophobic estrogens, but rarely degraded the hydrophilic estrogens.

Unified Analysis of Dewatering and Drying of Sludge Cake

To remove water from a suspension one needs to break down the binding energy between the adjacent water and the solid surface and to convey this water out of the suspension system. Using the binding energy between water and solids and the disrupting energy provided by mechanical and thermal means, this work presents a unified analysis on the dewatering of wet materials using binding energy as a clarification index. The binding energy versus residual water content plot for a wastewater sludge estimated the extent of dewatering each stage and the corresponding energy requirement.