The effect of salinity conditions on kinetics of trichloroethylene biodegradation by toluene-oxidizing cultures

This study investigates the effect of salt (NaCl) conditions on the biodegradations of trichloroethylene (TCE) by mixed cultures enriched on toluene. Two cultures were separately cultivated in this investigation, involving culture LHTO4, cultivated with freshwater and culture HHTO4, cultivated with 3.5% (w/v) NaCl solution. Batch tests were conducted to elucidate the degradations of toluene, TCE and a mixture of toluene and TCE by cultures LHTO4 at salinities of 0, 2 and 3.5% and by HHTO4 at salinity of 3.5%. The measurements were analyzed with microbial kinetics. The results show that for culture LHTO4 in the resting cells, when the transient salinities increased from 0 to 3.5%, the maximum specific rate of TCE degradation, k(TCE), declined from 2.28 to 1.45 d(-1), and the observed TCE transformation capacity, T(c,obs), decreased from 0.060 to 0.036 mgTCE/mgVSS. In the presence of toluene, TCE degradation was more inhibited by toluene (inhibition coefficients, K(I,TOL) were 0.8, 2.2, and 0.96 mg/L for salinity 0, 2, and 3.5%, respectively) than toluene degradation was by TCE (K(I,TCE) were 14, 5.8, and 1000 mg/L for salinity 0, 2, and 3.5%, respectively). Under long-term salinity stress, the culture HHTO4 maintained its capacity to utilize toluene but lost its effectiveness in the cometabolic transformation of TCE: k(TCE) fell to 0.25 d(-1) and T(c,obs) dropped to 0.024 mgTCE/mgVSS. This work reveals that the degradation of TCE by toluene-oxidizing cultures under saline conditions can be best described by the chosen kinetic equations and experimentally estimated constants, which can thus be used to lay a foundation for the rational design of biological processes to remove TCE from saline solutions.     

受控堆肥生物降解法测定全生物降解塑料(PBS)性能

依据GB/T 19277-2003/ISO 14855:1999,对降解塑料聚丁二酸丁二醇酯(PBS)、丁二酸对苯二甲酸丁二醇共聚酯(PBST)进行堆肥化条件下生物降解能力的测定.试验结果,用此方法评价塑料生物降解性能是可行的.PBS、PBST具有良好的生物降解性.建立了高分子材料测定方法的操作系统.     

Cadmium sorption by EPSs produced by anaerobic sludge under sulfate-reducing conditions

This study showed that EPS produced by anaerobic sludge under sulfate-reducing bacteria was effective in removing Cd(2+) from solution. The sorption data could be described by the Freundlich isotherm model. The q(m) derived from the Langmuir isotherm model was up to 2720 mg/g EPSs. The presence of copper and nickel ions had significantly reduced the cadmium sorption by EPS and the presence of zinc had little effect. Analysis of FTIR spectra demonstrated that C-O-C of polysaccharides at 1150-1030 cm(-1), group of the amide(I), CH(2) group of the lipids, carboxyl and -OH groups of proteins and polysaccharides were involved in cadmium binding, of which the -OH groups and the C-O-C group of polysaccharides played a major role in cadmium sorption by EPSs.     

Determination of thermal diffusivity under mixed boundary conditions

An examination is made of different variants of the determination of thermal diffusivity when boundary conditions fixed in time are imposed. It is shown that for these cases the thermal diffusivity may be determined by a single method.     

Kinetics of the biodegradation of green table olive wastewaters by aerobic and anaerobic treatments

The biodegradation of the organic pollutant matter present in green table olive wastewater (GTOW) is studied in batch reactors by an aerobic biodegradation and by an anaerobic digestion. In the aerobic biodegradation, the evolution of the substrate (in terms of chemical and biochemical oxygen demand), biomass, and total polyphenolic compounds present in the wastewater are followed during the process, and a kinetic study is performed using Contois' model, which when applied to the experimental results provides the kinetic parameter of this model, resulting in a modified Contois' equation (q=3.3S/(0.31S(0)X+X), gCOD/gVSS d(-1)). Other kinetic parameters were determined: the cellular yield coefficient (YX/S=5.7x10(-2) gVSS/gCOD) and the kinetic constant of cellular death phase (kd=0.16 d(-1)). Similarly, in the anaerobic digestion, the evolution of the substrate digested and the methane produced are followed, and the kinetic study is conducted using a modified Monod model combined with the Levenspiel model, due to the presence of inhibition effects. This model leads to the determination of the kinetic parameters: kinetic constant when no inhibitory substance is present (kM0=8.4x10(-2) h(-1)), critical substrate concentration of inhibition (TP*=0.34 g/L) and inhibitory parameter (n=2.25).     

Anaerobic biodegradation of fluoranthene under methanogenic conditions in presence of surface-active compounds

Bacillus cereus isolated from municipal wastewater treatment plant was used as a model strain to assess the efficiency of two anionic surfactants, a chemical surfactant and a biosurfactant during fluoranthene biodegradation under anaerobic methanogenic conditions. The surfactants selected for the study were linear alkyl benzene sulphonates (LAS) and rhamnolipid-biosurfactant complex from Pseudomonas sp. PS-17. Biodegradation of fluoranthene was monitored by GC/MS for a period up to 12th day. No change in the fluoranthene concentration was registered after 7th day. The presence of LAS enhanced the cell growth as well as the fluoranthene biodegradation. The rhamnolipid-biosurfactant at both used concentrations inhibited the cell growth and had no effect on the biodegradation rate. It was shown that LAS did not affect the microbial cell permeability and its positive effect on fluoranthene biodegradation was most likely as a result of the increased fluoranthene solubility. The results indicate that LAS can be considered as a promising agent for facilitation of the process of anaerobic polycyclic aromatic hydrocarbons (PAH) biodegradation under methanogenic conditions.     

Mechanism and kinetics of thermal decomposition of uranyl nitrate hexahydrate under the nonisothermal conditions

Thermal decomposition of UO₂(NO₃)₂·6H₂O to U₃O₈ was studied by thermogravimetric (TG), differential thermogravimetric (DTG), and differential thermal (DTA) analyses in combination with gaschromatographic and chemical methods. The process is described by kinetic data recorded under the non-isothermal conditions. UO₂(NO₃)₂·6H₂O transforms into UO₃ in eight main stages in the 40–300°C range, and UO₃ into U₃O₈, in three stages with the peaks of weight loss at 580, 620, and 645°C.     

Substrate independent assembly of optical structures guided by biomolecular interactions

The chip-scale integration of optical components is crucial for technologies as diverse as optical communications, optoelectronics displays, and photovoltaics. However, the realization of integrated optical devices from discrete components is often hampered by the lack of a universal substrate for achieving monolithic integration and by incompatibilities between materials. Emergent technologies such as chip-scale biophotonics, organic optoelectronics, and optofluidics present a host of new challenges for optical device integration, which cannot be solved with existing bonding techniques. Here, we report a new method for substrate independent integration of dissimilar optical components by way of biological recognition-directed assembly. Bonding in this scheme is achieved by locally modifying the substrate with a protein receptor and the optical component with a biomolecular ligand or vice versa. The key features of this new technology include substrate independent assembly, cross-platform vertical scale integration, and selective registration of components based on complementary biomolecular interactions.     

Electrochemical studies of microbiologically influenced corrosion of X80 steel by nitrate-reducing Bacillus licheniformis under anaerobic conditions

In this work, the impact of a wild-type nitrate-reducing Bacillus licheniformis strain on the corrosion behavior of X80 steel under anaerobic conditions was studied by electrochemical tests and biofilm characterization. The bioelectrochemical, electrochemical, and chemical reactions between X80 steel and microorganisms were investigated comprehensively. The results show that B. licheniformis can accelerate the corrosion of X80 steel substrate in early immersing by two ways: biocatalytic cathodic...     

Temperature field of a composite body under mixed thermal contact conditions

A heat-conduction equation is obtained for a piecewise-homogeneous body in the case when nonideal thermal contact conditions are satisfied on part of the connecting surface. The temperature field of a composite semiinfinite plate is investigated as an example.Translated from Inzhenerno-Fizicheskii Zhurnal, Vol. 49, No. 5, pp. 839–844, November, 1985.     

Studies on adsorption, desorption and biodegradation of pentachlorophenol by the anaerobic granular sludge in an upflow anaerobic sludge blanket (UASB) reactor

PCP-degrading anaerobic granular sludge could be formed in an upflow anaerobic sludge blanket (UASB) reactor that was seeded with anaerobic sludge acclimated to chlorophenol. When hydraulic retention time (HRT) was 20-22 h and PCP loading rate was 200-220 mgL(-1)d(-1), the wastewater containing 170-180 mgL(-1) PCP could be treated effectively in UASB reactor, and PCP removal rate reached up to 99.5%. PCP adsorption and desorption by anaerobic granular sludge follow Freundlich isothermal equation and part of adsorption capacity was not reversible. And the isothermal equation could well describe the variation law of PCP adsorption and desorption by anaerobic granular sludge. The results indicated that the principal removal mechanism of PCP was biodegradation by anaerobic granular sludge, but not adsorption or volatilization.     

Enantioselective interactions at the solid-liquid interface of an HPLC column under working conditions

A technique is presented which allows studying the enantioselective interactions occurring at the solid-liquid interface of a chiral stationary phase (CSP) and a racemate relevant to high performance liquid chromatography (HPLC). A conventional chiral column (Chiralpak AS) was mounted on an attenuated total reflection-infrared (ATR-IR) cell mimicking an HPLC setup equipped with an ATR-IR detector. Racemic pantolactone (PL) was used as the selectand. This setup in combination with modulation excitation spectroscopy (MES) allows for the identification of inter- and intramolecular hydrogen bonds being crucial for enantioseparation under HPLC operation conditions. The method is based on a two step strategy. In a first step, the enantiomers are separated by the chiral column similar to a standard HPLC experiment and upon adsorption on the identical CSP deposited on the internal reflection element (IRE), they are detected by ATR-IR spectroscopy. This experiment provides a retention time for each enantiomer. From the difference in retention, a suitable frequency is calculated which is used in a second experiment where the racemate concentration is varied alternately (modulation) in a way that the pulses of ( R)-PL and ( S)-PL exhibit a phase lag of 90 degrees after elution through the column. This procedure allows one to gain separate information of the enantioselective selectand-CSP interaction after performing a demodulation similar to a phase sensitive detection (PSD). A further benefit of this method is the strong enhancement of the signal-to-noise ratio. The effectiveness of the method is demonstrated by investigating the observed faster decrease in retention time of the later-eluted ( R)-PL, as compared to ( S)-PL, when separating at higher temperatures (from 12 to 36 degrees C). The origin is attributed to a weakening of a specific hydrogen bond between the C=O of ( R)-PL and the N-H of the CSP.     

Effects of shrinkage reducing admixture in shrinkage compensating concrete under non-wet curing conditions

The practice of using expansive agents has been recommended to manufacture shrinkage-compensating concrete provided that an adequate wet curing is carried out. On the other hand, more recently the use of shrinkage reducing admixture (SRA) has been suggested to improve concrete performance in terms of lower risk of cracking related to drying shrinkage.However, neither expansive agent nor SRA, when used separately, can definitively and safely avoid the risk of cracking caused by drying shrinkage in real concrete structures under the practical conditions of curing on many job-sites.This paper shows the advantages of the combined use of SRA and CaO-based expansive agent to produce shrinkage-compensating concrete even in the absence of an adequate wet curing.     

Wear characteristics of plasma-nitrided CrMo steel under mixed and boundary lubricated conditions

An investigation of the sliding wear mechanisms of a plasma-nitrided CrMo steel is undertaken using a running-in procedure that eliminates severe wear under mixed and boundary lubricated conditions. In the running-in procedure, using a pin-on-disc wear machine, smooth contact surfaces are obtained rather than the rough contact surfaces generally found in laboratory experiments. This enables the wear mechanisms to be investigated more clearly, particularly mild wear processes. The work shows no measurable nor visible wear under full fluid film lubricated conditions, the existence of polishing under mixed lubricated conditions and micro-pits under boundary lubricated conditions. The results presented in this paper indicate that a mild abrasive wear mechanism predominates under mixed lubricated conditions and a micro-fatigue wear mechanism under boundary lubricated conditions. Examination of the microstructure reveals the formation of white layer regimes on the contact surfaces after tests under boundary lubricated conditions, which suggests severe work-hardening of the contact surfaces. This revised version was published online in November 2006 with corrections to the Cover Date.     

Thermally induced changes in the magnetic properties of iron oxide nanoparticles under reducing and oxidizing conditions

Application of iron oxide nanoparticles in the fields of water purification, biomedicine or chemistry often requires controlled magnetic properties that can be modified by changing temperature and redox conditions. Therefore, this work investigates the changes in the magnetic properties of iron oxide nanoparticles in the FeOOH − Fe₂O₃ − Fe₃O₄ system (i.e. hematite, goethite, lepidocrocite, maghemite and magnetite) at heating under reducing and oxidizing conditions. The results show that heat treatment of hematite and goethite in the presence of a reducing agent (5% starch) leads to their conversion into high magnetic magnetite. The starting temperature of transformation is approximately 350 °C for both samples. The magnetization increases to 86 Am²/kg for hematite reduced at 700 °C and to 88 Am²/kg for goethite reduced at 900 °C. An intense reaction occurs within the first 10 min and then the conversion process decelerates. Thermal treatment of lepidocrocite under both oxidizing and reducing conditions leads to an increase in magnetization due to the formation of maghemite and magnetite, respectively. Regardless of the redox conditions, the formation of magnetic phase begins at a temperature of 250 °C and is associated with the formation of maghemite from lepidocrocite. Under oxidizing conditions, the magnetization begins to decrease at 350 °C, which is associated with the conversion of maghemite to hematite. On the contrary, under reducing conditions, the magnetization of lepidocrocite increases up to 900 °C, which is associated with the formation of magnetite. Maximum values of magnetization are 36 Am²/kg for maghemite obtained at 350 °C, and 88 Am²/kg for magnetite obtained at 900 °C from lepidocrocite. With the help of conventional heating, the magnetic properties of IONs can be altered by phase transformations in the FeOOH − Fe₂O₃ − Fe₃O₄ system. Temperature and redox conditions are the two most important factors controlling the transformation pathways and the magnetic properties of the resulting IONs.     

Inverse problem of fracture mechanics for a circular disc under mixed boundary conditions

Solution method for the problem of prevention of early brittle fracture of a circular disc with mixed boundary conditions was proposed. Theoretical analysis on determination of normal displacement of points on the boundary of a circular disc weakened by arbitrarily allocated rectilinear cracks was carried out. A closed system of algebraic equations permitting to provide minimization of fracture parameters (stress intensity factors) subject to geometrical and mechanical characteristics of a disc was constructed. Minimization of the stress intensity factors in a circular disc was carried out. They found normal displacement of points on the boundary of the circular disc increases carrying capacity of the disc.     

Experimental and simulation study of hydrogen sulfide adsorption on impregnated activated carbon under anaerobic conditions

In this study, a sodium carbonate impregnated activated carbon (IAC) was applied as the adsorbent for low concentration hydrogen sulfide (H2S) in nitrogen under the anaerobic conditions in a fixed bed. The effects of impregnation, relative humidity, temperature, and the inlet H2S concentration on the adsorption process were intensively investigated. The data of adsorption capacity were correlated by Langmuir isotherm. The results showed that the data fitted the model well within the concentration range studied. The IAC demonstrated more than three times adsorption capacity for H2S under dry conditions, compared with the original activated carbon (AC). It was confirmed that increasing relative humidity enhanced H2S adsorption capacity on both AC and IAC, and the adsorption capacity of H2S decreased slightly with increasing temperature. To predict breakthrough curves, a one-dimension model for the fixed beds packed with porous adsorbents was proposed and numerically solved. Simulation results matched with the experimental data in most part of the breakthrough curves.     

Microbial conversion of sulfur dioxide in flue gas to sulfide using bulk drug industry wastewater as an organic source by mixed cultures of sulfate reducing bacteria

Mixed cultures of sulfate reducing bacteria (SRB) were isolated from anaerobic cultures and enriched with SRB media. Studies on batch and continuous reactors for the removal of SO(2) with bulk drug industry wastewater as an organic source using isolated mixed cultures of SRB revealed that isolation and enrichment methodology adopted in the present study were apt to suppress the undesirable growth of anaerobic bacteria other than SRB. Studies on anaerobic reactors showed that process was sustainable at COD/S ratio of 2.2 and above with optimum sulfur loading rate (SLR) of 5.46kgS/(m(3)day), organic loading rate (OLR) of 12.63kg COD/(m(3)day) and at hydraulic residence time (HRT) of 8h. Free sulfide (FS) concentration in the range of 300-390mgFS/l was found to be inhibitory to mixed cultures of SRB used in the present studies.