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.

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.

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.

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.

Reliable estimation of virtual source position for SAFT imaging.

The synthetic aperture focusing technique (SAFT), employing a scanned focused transducer as a virtual source, is commonly used to image flaws in immersion testing. The position of a virtual source is estimated from rays emitted from the rim of a focused transducer. However, it is often found that the virtual source position cannot be uniquely determined because of severe focal spot aberration at the focal zone. Based on an analysis of the energy radiated from the focused transducer and the refracted energy varied with the incident angle of ultrasound, we propose that paraxial rays emitted from the focused transducer are the best for estimating the position of a virtual source for incorporation into SAFT. This study results also shows that by using this simple virtual source position estimation for SAFT, the axial resolution and SNR of the reconstructed image can be greatly improved. This new approach minimizes the effect of such factors as refraction at high-velocity-contrast interfaces, distance of the transducer to the couplant-specimen interface, and the focal length of a focused transducer, which may cause focal spot aberration resulting in decreased sensitivity in SAFT imaging.

A single-chamber microbial fuel cell without an air cathode.

Microbial fuel cells (MFCs) represent a novel technology for wastewater treatment with electricity production. Electricity generation with simultaneous nitrate reduction in a single-chamber MFC without air cathode was studied, using glucose (1 mM) as the carbon source and nitrate (1 mM) as the final electron acceptor employed by Bacillus subtilis under anaerobic conditions. Increasing current as a function of decreased nitrate concentration and an increase in biomass were observed with a maximum current of 0.4 mA obtained at an external resistance (R(ext)) of 1 KΩ without a platinum catalyst of air cathode. A decreased current with complete nitrate reduction, with further recovery of the current immediately after nitrate addition, indicated the dependence of B. subtilis on nitrate as an electron acceptor to efficiently produce electricity. A power density of 0.0019 mW/cm(2) was achieved at an R(ext) of 220 Ω. Cyclic voltammograms (CV) showed direct electron transfer with the involvement of mediators in the MFC. The low coulombic efficiency (CE) of 11% was mainly attributed to glucose fermentation. These results demonstrated that electricity generation is possible from wastewater containing nitrate, and this represents an alternative technology for the cost-effective and environmentally benign treatment of wastewater.

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.

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.

Low-temperature synthesis of rose-like ZnO nanostructures using surfactin and their photocatalytic activity.

Rose-like ZnO nanostructures were synthesized by the precipitation method using a biosurfactant (surfactin) as a templating-agent stabilizer. The concentration of surfactin in the precursor solution significantly influenced the thickness and density of the petals in the rose-like structures, and all samples were of a wurtzite phase. The thickness of the petal was found to decrease with increasing surfactin concentration. The average thickness of the petals was found to be between 10 and 13 nm. Photocatalytic degradation of methylene blue using rose-like ZnO nanostuctures was investigated, and the morphology, density and thickness of the ZnO petals were found to influence the photodegradation activity. The samples with loosely-spread petals, or plate-like ZnO structures, brought about the strongest photodegradation in comparison with the dense rose-like structures. The greater activity of the loose-petal structures was correlated with their higher absorption in the UV region in comparison with the other samples. The ZnO samples prepared using low surfactin concentrations had higher rate constant values, i.e., 9.1 x 10(-3) min(-1), which revealed that the photodegradation of methylene blue under UV irradiation progressed by a pseudo first-order kinetic reaction.

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.

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.