Young-Fo Chang

Glycerol degradation in single-chamber microbial fuel cells.

Glycerol degradation with electricity production by a pure culture of Bacillus subtilis in a single-chamber air cathode of microbial fuel cell (MFC) has been demonstrated. Steady state polarization curves indicated a maximum power density of 0.06 mW/cm(2) with an optimal external resistance of 390Ω. Analysis of the effect of pH on MFC performance demonstrated that electricity generation was sustained over a long period of time under neutral to alkaline conditions. Cyclic voltammetry exhibited the increasing electrochemical activity with the increase of pH of 7, 8 and 9. Voltammetric studies also demonstrated that a two-electron transfer mechanism was occurring in the reactor. The low Coulombic efficiency of 23.08% could be attributed to the loss of electrons for various activities other than electricity generation. This study describes an application of glycerol that could contribute to transformation of the biodiesel industry to a more environmentally friendly microbial fuel cell-based technology.

Comparative bioelectricity production from various wastewaters in microbial fuel cells using mixed cultures and a pure strain of Shewanella oneidensis

Current and power density from four wastewaters, agriculture (AWW), domestic (DWW), paper (PWW), and food/dairy (FDWW), were comparatively evaluated in combination with three inocula: wastewater endogenous microbes (MFC1), Shewanella oneidensis MR-1 (MFC2), and wastewater endogenous microbes with MR-1 (MFC3) in single chamber microbial fuel cells (MFC). Using AWW (0.011 mA/cm(2); 0.0013 mW/cm(2)) and DWW (0.017 mA/cm(2); 0.0036 mW/cm(2)), MFC2 was the best candidate providing the maximum current, whereas AWW-MFC1 and DWW-MFC1 were unable to construct a well-established MFC. FDWW produced a maximum current from MFC3 (0.037 mA/cm(2); 0.015 mW/cm(2)), and confirmed the unsuitability of MFC2 at an alkaline pH. FDWW-MFC3 also performed best with the highest substrate degradation and coulombic efficiency. Mixed culture in MFC3 resulted in higher current generation under the influence of MR-1 (except in PWW), indicating the endogenous microbes were not solely responsible for the current but the outperformance was significantly attributed to the association of MR-1.

Removal of Cu, Pb and Zn by foam fractionation and a soil washing process from contaminated industrial soils using soapberry-derived saponin: A comparative effectiveness assessment

The feasibility of using the eco-friendly biodegradable surfactant saponin (a plant-based surfactant) from soapberry and surfactin from Bacillus subtilis (BBK006) for the removal of heavy metals from contaminated industrial soil (6511mgkg(-1) copper, 4955mgkg(-1) lead, and 15090mgkg(-1) zinc) by foam fractionation and a soil flushing process was evaluated under variation of fundamental factors (surfactant concentration, pH, temperature and time). The results of latter process showed that 1-2% Pb, 16-17% Cu and 21-24% Zn was removed by surfactin after 48h, whereas the removal of Pb, Cu and Zn was increased from 40% to 47%, 30% to 36% and 16% to 18% in presence of saponin with an increase from 24 to 72h at room temperature by the soil washing process at pH 4. In the foam fractionation process, the metal removal efficiencies were increased with increases in the saponin concentration (0.075-0.15gL(-1)) and time (24-72h), whereas the efficiency was decreased with increasing pH (4-10) and temperature (>40°C). The removal efficiencies of Pb, Cu and Zn were increased significantly from 57% to 98%, 85% to 95% and 55% to 56% with an increase in the flow rate from 0.2 to 1.0Lmin(-1) at 0.15gL(-1) saponin (pH 4 and 30°C). The present investigation indicated that the foam fractionation process is more efficient for the removal of heavy metal from contaminated industrial soil in comparison to the soil washing process. The plant-based eco-friendly biodegradable biosurfactant saponin can be used for environmental cleanup and pollution management.

Synthesis of Brushite Particles in Reverse Microemulsions of the Biosurfactant Surfactin

In this study the “green chemistry” use of the biosurfactant surfactin for the synthesis of calcium phosphate using the reverse microemulsion technique was demonstrated. Calcium phosphates are bioactive materials that are a major constituent of human teeth and bone tissue. A reverse microemulsion technique with surfactin was used to produce nanocrystalline brushite particles. Structural diversity (analyzed by SEM and TEM) resulted from different water to surfactin ratios (W/S; 250, 500, 1000 and 40,000). The particle sizes were found to be in the 16–200 nm range. Morphological variety was observed in the as-synthesized microemulsions, which consisted of nanospheres (~16 nm in diameter) and needle-like (8–14 nm in diameter and 80–100 nm in length) noncalcinated particles. However, the calcinated products included nanospheres (50–200 nm in diameter), oval (~300 nm in diameter) and nanorod (200–400 nm in length) particles. FTIR and XRD analysis confirmed the formation of brushite nanoparticles in the as-synthesized products, while calcium pyrophosphate was produced after calcination. These results indicate that the reverse microemulsion technique using surfactin is a green process suitable for the synthesis of nanoparticles.

Electricity Generation and Wastewater Treatment of Oil Refinery in Microbial Fuel Cells Using Pseudomonas putida

Microbial fuel cells (MFCs) represent a novel platform for treating wastewater and at the same time generating electricity. Using Pseudomonas putida (BCRC 1059), a wild-type bacterium, we demonstrated that the refinery wastewater could be treated and also generate electric current in an air-cathode chamber over four-batch cycles for 63 cumulative days. Our study indicated that the oil refinery wastewater containing 2213 mg/L (ppm) chemical oxygen demand (COD) could be used as a substrate for electricity generation in the reactor of the MFC. A maximum voltage of 355 mV was obtained with the highest power density of 0.005 mW/cm2 in the third cycle with a maximum current density of 0.015 mA/cm2 in regard to the external resistor of 1000 Ω. A maximum coulombic efficiency of 6 × 10−2% was obtained in the fourth cycle. The removal efficiency of the COD reached 30% as a function of time. Electron transfer mechanism was studied using cyclic voltammetry, which indicated the presence of a soluble electron shuttle in the reactor. Our study demonstrated that oil refinery wastewater could be used as a substrate for electricity generation.

Time of flight diffraction imaging for double-probe technique

Due to rapid progress in microelectronics and computer technologies, the system evolving from analog to digital, and a programmable and flexible synthetic aperture focusing technique (SAFT) for the single-probe pulse-echo imaging technique of ultrasonic nondestructive testing (NDT) becomes feasible. The double-probe reflection technique usually is used to detect the nonhorizontal flaws in the ultrasonic NDT. Because there is an offset between the transmitter and receiver, the position and size of the flaw cannot be directly read from the image. Therefore, a digital signal processing (DSP) imaging method is proposed to process the ultrasonic image obtained by double-probe reflection technique. In the imaging, the signal is redistributed on an ellipsoid with the transmitter and receiver positions as focuses, and the traveltime sum for the echo from the ellipsoid to the focuses as the traveltime of signal. After redistributing all the signals, the useful signals can be constructively added in some point in which the reflected point is; otherwise, the signals will be destructively added. Therefore, the image resolution of the flaw can be improved and the position and size of the flaw can be estimated directly from the processed image. Based on the experimental results, the steep flaw (45 degrees) cannot be detected by the pulse echo technique but can be detected by the double-probe method, and the double-probe B-scan image of 30 degrees tilted crack is clearer than the pulse echo B-scan image. However, the flaw image departs from its true position greatly. After processing, the steep flaw image can be moved to its true position. When the flaws are not greater than the probe largely, the sizes of the flaws are difficult to be discriminated in both pulse echo and double-probe B-scan images. In the processed double-probe B-scan image, the size of the flaws can be estimated successfully, and the images of the flaws are close to their true shape.

A 3-D Image Detection Method of a Surface Opening Crack in Concrete Using Ultrasonic Transducer Arrays

The detection of the size and the location of existing three dimensional cracks in a concrete structure is an important topic in civil engineering. In this paper, a multisource, multireceiver method that considers the travel times diffracted by a crack tip is introduced, to backcalculate a 3-D image of the crack tip of a surface opening crack. The possible location of the crack tip front is on the surface of an ellipsoid, which is constructed by a fixed travel time length measured from the source to the receiver, by letting the source and receiver points be the foci of the corresponding ellipsoid. If the locations of the source and the receiver, together with the associated measured travel time of the diffracted echo between each source-receiver pair are known, the image of the tip can be determined by counting the number of intersections of the ellipsoidal surfaces in an image construction cellular structure. The backcalculated crack tip image, as seen from experimental data, match the dimensions of the real crack very well, demonstrating the capability and accuracy of this newly proposed multisource, multireceiver method for concrete NDE.

Evaluation of remediation process with soapberry derived saponin for removal of heavy metals from contaminated soils in Hai-Pu, Taiwan

The use of a biodegradable natural plant-based surfactant extracted from soapberry is proposed for the remediation of Ni, Cr and Mn from industrial soil site in Hai-Pu, Taiwan. Batch experiments were performed under variation of fundamental factors (saponin concentration, pH, and incubation time) for metal remediation. Removal of Ni and Mn were increased with increasing saponin concentration (0.015-0.150 g/L), whereas the removal of Cr was increased upto 0.075 g/L saponin. The Ni, Cr and Mn were removed significantly (p < or = 0.05) at near to the neutral and slightly acidic (pH 5 to 8) conditions. Removal efficiency of Ni (99%) from the soil was found to be greater than that of Cr (73%) or Mn (25%) in the presence of saponin at a concentration of 0.150 g/L at pH 5. The removal percentage increased with incubation time where the removal of Ni was faster than that of Cr and Mn. The result indicates the feasibility of eco-friendly removal of heavy metal (Ni, Cr and Mn) from industrial soil by soil washing process in presence of plant derived saponin.

Feasibility of detecting embedded cracks in concrete structures by reflection seismology

Reflection seismology has been widely used in the petroleum exploration industry for decades. To improve the capabilities of detecting the depths and lengths of cracks inside a concrete element, an ultrasonic common depth point (CDP) reflection technique was employed in this study. The effectiveness and accuracy of applying the reflection seismology method to detect cracks embedded in concrete structures are discussed. Test results show that simulated blind cracks with certain lengths, dip angles and depths inside concrete specimen can be successfully imaged and identified. This study shows that when the signals reflected from the crack are obscure, the CDP signal stacking method is very useful and provides an opportunity to look into the object, which is not possible with traditional ultrasonic methods.

Identification and discrimination of bacteria using Fourier transform infrared spectroscopy

Bacterial spectra were obtained in the wavenumber range of 4000-600 cm(-1) using FTIR spectroscopy. FTIR spectral patterns were analyzed and matched with 16S-rRNA signatures of bacterial strains OS1 and OS2, isolated from oil sludge. Specific spectral bands obtained from OS1 (FJ226761), reference strain Bacillus flexus (ATCC 49095), OS2 (FJ215874) and reference strain Stenotrophomonas maltophilia (ATCC 19861) respectively, suggested that OS1 and ATCC 49095 were closely related whereas OS2 was different. The bands probably represent groups of proteins and lipids of specific bacteria. Separate peaks found in B. flexus were similar to those of OS1. The S. maltophilia (ATCC 19861) and OS2 exhibited a similar peak at 3272 cm(-1). Amide bands (I, II and III) exhibited that OS1 and B. flexus were closely related, but were different from OS2. In the fingerprint region, peak at 1096 cm(-1) and 1360 cm(-1) exhibited the specific fingerprints of OS2 and reference strain S. maltophilia (ATCC 19861), respectively. The specific fingerprint signature was found at 1339 cm(-1) for OS1 and at 1382 cm(-1) for B. flexus ATCC 49095, allowing these two strains of B. flexus to be differentiated. This spectral signature originated from phospholipid and RNA components of the cell. Principle components analysis (PCA) of spectral regions exhibited with distinct sample clusters between Bacillus flexus (ATCC 49095), S. maltophilia (ATCC 19861), OS1 and OS2 in amide and fingerprint region.