Performance of a biofilter for the removal of high concentrations of styrene under steady and non-steady state conditions

The performance of a laboratory scale perlite biofilter inoculated with a mixed culture was evaluated for gas phase styrene removal under various operating conditions. Experiments were carried out by subjecting the biofilter to different flow rates (0.15–0.9 m³ h⁻¹) and concentrations (0.03–17.3 g m⁻³), corresponding to inlet loading rates varying from as low as 3 g m⁻³ h⁻¹ to as high as 1390 g m⁻³ h⁻¹. A maximum elimination capacity (EC) of 382 g m⁻³ h⁻¹ was achieved at an inlet loading rate of 464 g m⁻³ h⁻¹ with a removal efficiency of 82%. The high elimination capacity reached with this system could have been due to the dominant presence of filamentous fungi among others. The impact of relative humidity (RH) (30%, 60% and >92%) on the biofilter performance was evaluated at two constant loading rates, viz., 80 and 260 g m⁻³ h⁻¹, showing that inhibitory effects were only significant when combining the highest loads with the lowest relative humidities. Biomass distribution, moisture content and concentration profiles along the bed height were significantly dependent on the relative humidity of the inlet air and on the loading rate. The dynamic behaviour of the biofilter through vigorous short and long-term shock loads was tested at different process conditions. The biofilter was found to respond apace to rapid changes in loading conditions. The stability of the biomass within the reactor was apparent from the fast response of the biofilter to recuperate and handle intermittent shutdown and restart operations, either with or without nutrient addition.     

Effects of adsorptive properties of biofilter packing materials on toluene removal

Various adsorptive materials, including granular activated carbon (GAC) and ground tire rubber (GTR), were mixed with compost in biofilters used for treating gaseous toluene, and the effects of the mixtures on the stability of biofilter performance were investigated. A transient loading test demonstrated that a sudden increase in inlet toluene loading was effectively attenuated in the compost/GAC biofilter, which was the most significant advantage of adding adsorptive materials to the biofilter packing media. Under steady conditions with inlet toluene loading rates of 18.8 and 37.5 g/m³/h, both the compost and the compost/GAC biofilters achieved overall toluene removal efficiencies greater than 99%. In the compost/GAC mixture, however, biodegradation activity declined as the GAC mass fraction increased. Because of the low water-holding capacity of GTR, the compost/ground tire mixture did not show a significant improvement in toluene removal efficiency throughout the entire operational period. Furthermore, nitrogen limitations affected system performance in all the biofilters, but an external nitrogen supply resulted in the recovery of the toluene removal efficiency only in the compost biofilter during the test periods. Consequently, the introduction of excessive adsorptive materials was unfavorable for long-term performance, suggesting that the mass ratio of the adsorptive materials in such mixtures should be carefully selected to achieve high and steady biofilter performance.     

Performance evaluation of full-scale upflow anaerobic sludge blanket reactor treating distillery spentwash

Performance of full-scale upflow anaerobic sludge blanket (UASB) reactors treating distillery spentwash was evaluated. The plant was designed to handle 650 m³ day⁻¹ of distillery spentwash having an average chemical oxygen demand (COD) concentration of 112,400 mg l⁻¹ with a HRT of 6 days. In the plant, the pH level of the influent varied from 3.50 to 4.40 but the pH of the treated effluent stabilized to a range of 7.36 to 7.68 during the study period. The operation of the reactors during study period revealed the stable conditions of the reactors, which is evident from the low COD, biochemical oxygen demand (BOD) and total solids (TS) contents in treated effluent. In the plant, the COD, BOD₅ and TS removal efficiencies were stabilized to the range of 62.19–66.59, 72.42–77.11, and 58.47–60.46%, respectively at an organic loading rate of 2.15–4.60 kg COD m⁻³ day⁻¹. The biogas production was stabilized to the range of 48,290–135,115 m³ week⁻¹ with 60% methane content. The total quantity of biogas produced ranged from 0.40 to 0.57, 1.04 to 1.71 and 0.40 to 0.56 m³ kg⁻¹ removals of COD, BOD and TS, respectively. This study concluded that the treatment of distillery spentwash using UASB reactors contributed significantly for pollution load reduction besides generating renewable in-house bio-energy.     

A study on sediment accumulation and environmental pollution of Fethiye Gulf in Turkey

This study aims to estimate with available data the present situation of sediment deposited at Fethiye Gulf—which is located in southwestern part of Turkey and has high tourism potential—to evaluate environmental effects of sediment transportation and to analyse future measures in the plain and upper basins to minimize possible sediment accumulation in the gulf. As a result of the study, it was determined that approximately 3.62 million m³ sediment has been transported to the gulf, and gulf area has been narrowed by up to 7 ha. The concentration of very fine load (silt and clay) transported to gulf by streams, offtake canals, and wastewater canals of mining sector varies between 1.0 and 16.0 mg l⁻¹. However, the sediment concentration of samples taken from open canals belonging to ferrochromous facilities varies between 25.0 and 65.0 mg l⁻¹. In those canals, it was seen that a large amount of Cr, Pb, and Hg metals exist. It shows that ferrochromous facilities have not been able to deposit fine grain load. The specific weight of transported sediment to gulf is between 2.75 and 2.80 g cm⁻³. Dissolved oxygen values in the gulf were measured at between 8.0 and 9.0 mg l⁻¹.     

Feasibility of <Emphasis Type="Italic">m</Emphasis>-cresol degradation using an indigenous mixed microbial culture with glucose as co-substrate

An indigenous mixed culture of microorganisms, isolated from the soil of a gasoline filling station, was used in degrading m-cresol in presence of glucose as an alternative carbon source. Initial glucose concentration was kept at either 250 or 500 mg l⁻¹, to initiate and support necessary culture growth, and that of m-cresol was varied between 50 and 400 mg l⁻¹. A maximum total biomass yield value of 0.925 g g⁻¹ was obtained at 100 mg l⁻¹ m-cresol and 500 mg l⁻¹ glucose initial concentrations in the media. Variation in the experimentally observed specific growth rate revealed that m-cresol initial concentrations, above 100 mg l⁻¹, inhibited the culture growth irrespective of the glucose concentrations used in the study. Complete degradation of m-cresol was observed within a time period of 18–26 h depending upon the initial concentrations of m-cresol and glucose in the media; on the other hand, glucose utilization was quick and preceded m-cresol degradation. A sum kinetics model was used to describe the variation in the culture specific growth rate, which gave a high coefficient of determination (R ²) value >0.98. From the interaction parameter values obtained by solving this model, the inhibitory effect of glucose on m-cresol degradation by the culture was found to be more pronounced compared to the effect of m-cresol on glucose utilization. This study showed good potential of the indigenous mixed culture in degrading m-cresol when it is provided with a simple alternative carbon source, such as glucose, for supporting its growth.     

On the generalized large set of Kasami sequences

In this paper, we present a new family of binary Kasami sequences of length 2 ⁿ − 1 for even integer n = 2m. It generalizes the recently proposed large set F^(l){\mathcal{F}^{(l)}} of Kasami sequences by relaxing the restriction on l to a more general case. The presented sequence family takes five nontrival correlation values −1, −1 ± 2 ^m , −1 ± 2 ^{m + gcd(m,l)}, and has family size 2^3m  + 2 ^m or 2^3m  + 2 ^m −1. We also completely determine the distribution of these correlation values.     

Thermophysical Property Measurements of Liquid Gadolinium by Containerless Methods

Thermophysical properties of liquid gadolinium were measured using non-contact diagnostic techniques with an electrostatic levitator. Over the 1585 K to 1920 K temperature range, the density can be expressed as ρ(T) = 7.41 × 10³ − 0.46 (T − T _m) (kg · m⁻³) where T _m = 1585 K, yielding a volume expansion coefficient of 6.2 × 10⁻⁵ K⁻¹. In addition, the surface tension data can be fitted as γ(T) = 8.22 × 10² − 0.097(T − T _m)(10⁻³ N · m⁻¹) over the 1613 K to 1803 K span and the viscosity as η(T) = 1.7exp[1.4 × 10⁴/(RT)](10⁻³ Pa · s) over the same temperature range.     

Thermophilic biofiltration of H2S and isolation of a thermophilic and heterotrophic H2S-degrading bacterium, Bacillus sp. TSO3

Thermophilic biofiltration of H₂S-containing gas was studied at 60 °C using polyurethane (PU) cubes and as a packing material and compost as a source of thermophilic microorganisms. The performance of biofilter was enhanced by pH control and addition of yeast extract (YE). With YE supplement and pH control, H₂S removal efficiency remained above 95% up to an inlet concentration of 950 ppmv at a space velocity (SV) of 50 h⁻¹ (residence time = 1.2 min). H₂S removal efficiency strongly correlated with the inverse of H₂S inlet concentrations and gas flow rates. Thermophilic, sulfur-oxidizing bacteria, TSO3, were isolated from the biofilter and identified as Bacillus sp., which had high similarity value (99%) with Bacillus thermoleovorans. The isolate TSO3 was able to degrade H₂S without a lag period at 60 °C in liquid cultures as well as in the biofilter. High H₂S removal efficiencies were sustained with a periodic addition of YE. This study demonstrated that an application of thermophilic microorganism for a treatment of hot gases may be an economically attractive option since expensive pre-cooling of gases to accommodate mesophilic processes is not required.     

Creep behavior of AZ31 magnesium alloy in low temperature range between 423 K and 473 K

The deformation behavior of coarse-grained AZ31 magnesium alloy was examined in creep at low temperatures below 0.5 T _m and low strain rates below 5 × 10⁻⁴ s⁻¹. The creep test was conducted in the temperature range between 423 and 473 K (0.46–0.51 T _m) under various constant stresses covering the strain rate range 5 × 10⁻⁸ s⁻¹–5 × 10⁻⁴ s⁻¹. All of the creep curves exhibited two types depending on stress level. At low stress (σ/G < 4 × 10³), the creep curve was typical of class I behavior. However, at high stresses (σ/G > 4 × 10³), the creep curve was typical of class II. At the low stress level, deformation could be well described by solute drag creep whereas at the high stress level, deformation could be well described by dislocation climb creep associated with pipe diffusion or lattice diffusion. The transition of deformation mechanism from solute drag creep to dislocation climb creep, on the other hand, could be explained in terms of solute-atmosphere-breakaway concept.     

Spectral study of interaction between poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine)–poly(ethylene glycol)–poly(<Emphasis Type="SmallCaps">l</Emphasis>-lysine) and nucleic acids

Polymer-DNA interactions have attracted considerable interests due to their important application in DNA transfection and cellular drug delivery technologies. In this work, a new detection assay for DNA is proposed with a tri-block copolymer poly(l-lysine)–poly(ethylene glycol)–poly(l-lysine) by resonance light scattering technique with the linear ranges from 0.0656 to 6.56 μg ml⁻¹. The detection limit for DNA is 0.42 ng ml⁻¹. Most coexisting substances do not interfere in the detection. UV-spectra and FTIR-spectra were employed to demonstrate the mechanisms of the interaction that the conformation of the DNA changes because the microenvironment of DNA changes.     

Improvements in the Dynamic Plane Source Method

Three sources of errors in the extended dynamic plane source (EDPS) method caused by the discrepancy between experiment and model are analyzed. The source effect is eliminated by introducing the nuisance parameter R ₀ and the surface effect by a surrounding vacuum. The original model assumes a constant heating power but a constant current is used in the experiment. Suppression of this effect leads to a new solution of the heat equation designated as the constant-current model. The measurements on polymethylmetacrylate (PMMA) in vacuum, evaluated by the constant-current model, provided results of λ = 0.191 W.m⁻¹.K⁻¹ and a = 0.118 ×10⁻⁶ m ².s ^{− 1}, which are in good agreement with published values. The total standard uncertainty was estimated as 1.5 % for both thermophysical properties.     

Screening and optimization of media constituents for decolourization of Mordant Blue-9 dye by Phanerochaete chrysosporium

Decolourization of Mordant Blue-9 (MB-9) by the white-rot fungi Phanerochaete chrysosporium MTCC 787 was investigated by screening and optimization of the media constituents used for growing the fungus. Both % decolourization and specific removal of MB-9 by the fungus were taken as the responses to screen and optimize the media constituents using statistically valid Plackett–Burman and response surface methodology (RSM) design of experiments, respectively. Amongst the media constituents screened, glucose, veratryl alcohol, KH₂PO₄ and CaCl₂ were selected as the most important (P value < 0.05) media constituents for MB-9 dye decolourization; the other media constituents, viz. MgSO₄, tween 20, NH₄Cl₂ and inoculum size were, however, found to be insignificant in the study. Central composite design followed by RSM used in optimizing the important media constituents for enhancing the decolourization of MB-9 dye revealed optimum combinations of glucose, 13.46 g l⁻¹; veratryl alcohol, 9.30 mM; KH₂PO₄, 24.52 g l⁻¹; CaCl₂, 2.18 g l⁻¹; MgSO₄, 9.89 g l⁻¹; NH₄Cl₂, 4.68 g l⁻¹; tween 20, 0.050% and inoculum size, 0.8 OD₆₅₀, which gave a maximum % dye decolourization of 100% and specific dye removal of 0.1571 mg U⁻¹.     

Kinetics of zero-valent iron reductive transformation of the anthraquinone dye Reactive Blue 4

The effect of operational conditions and initial dye concentration on the reductive transformation (decolorization) of the textile dye Reactive Blue 4 (RB4) using zero-valent iron (ZVI) filings was evaluated in batch assays. The decolorization rate increased with decreasing pH and increasing temperature, mixing intensity, and addition of salt (100 g L⁻¹ NaCl) and base (3 g L⁻¹ Na₂CO₃ and 1 g L⁻¹ NaOH), conditions typical of textile reactive dyebaths. ZVI RB4 decolorization kinetics at a single initial dye concentration were evaluated using a pseudo first-order model. Under dyebath conditions and at an initial RB4 concentration of 1000 mg L⁻¹, the pseudo first-order rate constant (k_obs) was 0.029 ± 0.006 h⁻¹, corresponding to a half-life of 24.2 h and a ZVI surface area-normalized rate constant (k_SA) of 2.9 × 10⁻⁴ L m⁻² h⁻¹. However, as the initial dye concentration increased, the k_obs decreased, suggesting saturation of ZVI surface reactive sites. Non-linear regression of initial decolorization rate values as a function of initial dye concentration, based on a reactive sites saturation model, resulted in a maximum decolorization rate (V_m) of 720 ± 88 mg L⁻¹ h⁻¹ and a half-saturation constant (K) of 1299 ± 273 mg L⁻¹. Decolorization of RB4 via a reductive transformation, which was essentially irreversible (2–5% re-oxidation), is believed to be the dominant decolorization mechanism. However, some degree of RB4 irreversible sorption cannot be completely discounted. The results of this study show that ZVI treatment is a promising technology for the decolorization of commercial, anthraquinone-bearing, spent reactive dyebaths.     

Thermal Transport Properties of Functionally Graded Carbon Aerogels

Novel graded carbon aerogels were synthesized to study the impact of different synthesis parameters on the material properties on a single sample and to test a new, locally resolved thermal-conductivity measurement technique. Two identical cylindrical aerogels with a graded structure along the main cylindrical axis were synthesized. Along the gradient with an extension of about 20 mm the densities range from 240 kg·m⁻³ to 370 kg·m⁻³ and the effective pore diameter determined via small angle X-ray scattering and SEM increase systematically from 70 nm up to 11,000 nm. One specimen was cut perpendicular to the cylinder axis into disc-shaped samples; their thermal conductivities in an argon atmosphere, as determined via a standard laser-flash technique, range from 0.06W·m⁻¹·K⁻¹ to 0.12W·m⁻¹·K⁻¹ at 600 °C. The second specimen, cut to obtain a sample with the gradient in-plane, was investigated with a spatially resolved laser-flash technique at ambient conditions. The results of the two different techniques are compared and discussed in detail.     

Ethylene removal evaluation and bacterial community analysis of vermicompost as biofilter material

Biofiltration of ethylene provides an environmentally friendly and economically beneficial option relative to physical/chemical removal, where selection of appropriate bed material is crucial. Here the vermicompost with indigenous microorganisms as bed material was evaluated for ethylene removal through batch test and biofilter experiment. Temporal and spatial dynamics of bacterial community in the vermicompost-biofilter under different ethylene loads were characterized by culture and denaturing gradient gel electrophoresis (DGGE) methods. The results showed that ethylene was effectively degraded by the vermicompost under conditions of 25-50% moisture content and 25-35 °C temperature. The vermicompost-biofilter achieved nearly 100% ethylene removal up to an inlet load of 11 mg m⁻³ h⁻¹. Local nitrogen lack of the vermicompost in the biofilter was observed over operation time, but the change of pH was slight. DGGE analysis demonstrated that the bacterial abundance and community structure of vermicompost-biofilter varied with the height of biofilter under different ethylene loads. Pseudomonads and Actinobacteria were predominant in the biofilter throughout the whole experiment.     

Modeling of chromium (VI) biosorption by immobilized Spirulina platensis in packed column

This study describes biosorption of chromium (VI) by immobilized Spirulina platensis, in calcium alginate beads. Three aspects viz. optimization of bead parameters, equilibrium conditions and packed column operation were studied and subsequently modeled. Under optimized bead diameter (2.6 mm), calcium alginate concentration (2%, w/v) and biomass loading (2.6%, w/v) maximum biosorption was achieved. 140 g l⁻¹ loading of optimized beads resulted in 99% adsorption of chromium (VI) ions from an aqueous solution containing 100 mg l⁻¹ of chromium (VI). The quantitative chromium (VI) uptake was effectively described by Freundlich adsorption isotherm. The immobilized S. platensis beads were further used in a packed bed column wherein the effects of bed height, feed flow rate, inlet chromium (VI) ion concentration were studied by assessing breakthrough time. The performance data were tested for various models fitting in order to predict scale up-design parameters such as breakthrough time and column height. Results were encouraging.     

Shock behaviour of a phenolic resin

Phenolic resins are used in many aspects of everyday life, e.g. as the matrix material for carbon fibre laminates used in the aerospace industry. Consequently, detailed knowledge of this material, especially while under shock loading, is extremely useful for the design of components that could be subjected to impact during their lifespan. The shock Hugoniot equations of state for phenolic resin (Durite SC-1008), with initial density of 1.18 g cm⁻³ have been determined using the plate-impact technique with in situ manganin stress gauges. The Hugoniot equation in the shock velocity–particle velocity plane was found to be non-linear in nature with the following equation: U _S = 2.14 + 3.79u _p − 1.68u _p². Further, the Hugoniot in the pressure–volume plane was observed to largely follow the hydrostatic curve. Lateral gauge measurements were also obtained. An ANSYS Autodyn^TM 2D model was used to investigate the lateral stress behaviour of the SC-1008. A comparison of the Hugoniot elastic limit calculated from the shear strength and measured sound speeds gave reasonable agreement with a value of 0.66 ± 0.35 GPa obtained.     

High-speed preparation and dielectric properties of BaTi<Subscript>4</Subscript>O<Subscript>9</Subscript> film by laser chemical vapor deposition

BaTi₄O₉ film was prepared on Pt/Ti/SiO₂/Si substrate by laser chemical vapor deposition. The microstructure and dielectric properties were investigated. The single-phase BaTi₄O₉ film with random orientation was obtained. The surface consisted of round and rectangular grains, and the cross-section was columnar microstructure. The deposition rate (R _dep) was 135 μm h⁻¹. The dielectric constant (ε _r) and loss (tanδ) were 35 and 0.01, respectively, at 1 MHz. With increasing temperature, ε _r increased and showed a broad peak around 736 K, which indicated there might be a phase transition.     

Current–voltage characteristics and impedance spectroscopy of LiNbO<Subscript>3</Subscript> films grown by RF magnetron sputtering

Polycrystalline LiNbO₃ films with random orientation of grains on (001)Si substrates have been grown by RF magnetron sputtering method. Electrical conductance of the formed (001)Si–LiNbO₃ heterostructures is defined through hopping mechanism by charge localization centers (CLC) in the band gap of LiNbO₃ with concentration N _t  = 2.3 × 10²⁴ m⁻³. Analysis of the impedance frequency spectrum has disclosed two relaxation processes of Maxwell–Wagner type with relaxation times τ₁ = 0.1 s and τ₂ = 1 × 10⁻⁴ s. Thermal annealing at T = 650 °C leads to an increase in the average grain size from 50 to 95 nm; it also leads to a decrease in the CLC concentration down to N _t  = 2.8 × 10²⁰ m⁻³. Electrical conductance of (001)Si–LiNbO₃ heterostructures after thermal annealing is determined by space charge limited conduction mechanism. There have been defined parameters of dielectric hysteresis loops. It has been demonstrated that thermal annealing leads to a decrease in values of remanent polarization and coercive field.     

Influence of temperature and strain rate on cohesive properties of a structural epoxy adhesive

Effects of temperature and strain rate on the cohesive relation for an engineering epoxy adhesive are studied experimentally. Two parameters of the cohesive laws are given special attention: the fracture energy and the peak stress. Temperature experiments are performed in peel mode using the double cantilever beam specimen. The temperature varies from −40 to + 80°C. The temperature experiments show monotonically decreasing peak stress with increasing temperature from about 50 MPa at −40°C to about 10 MPa at + 80°C. The fracture energy is shown to be relatively insensitive to the variation in temperature. Strain rate experiments are performed in peel mode using the double cantilever beam specimen and in shear mode, using the end notch flexure specimen. The strain rates vary; for peel loading from about 10⁻⁴ to 10 s⁻¹ and for shear loading from 10⁻³ to 1 s⁻¹. In the peel mode, the fracture energy increases slightly with increasing strain rate; in shear mode, the fracture energy decreases. The peak stresses in the peel and shear mode both increase with increasing strain rate. In peel mode, only minor effects of plasticity are expected while in shear mode, the adhesive experiences large dissipation through plasticity. Rate dependent plasticity, may explain the differences in influence of strain rate on fracture energy between the peel mode and the shear mode.