Nutrient release from integrated constructed wetlands sediment receiving farmyard run‐off and domestic wastewater

Constructed wetland sediments are frequently contaminated with nitrogen and phosphorus. There is a risk that accumulated pollutants can either be remobilised or reach the groundwater. Five identical mesocosms, which were filled with subsoil collected from full‐scale integrated constructed wetland (the first cell receives the most contaminated influent), were set up to examine nutrient removal within sediment layers. The results indicated that accumulated nutrients leached out into inflow water and that the sediment capacity of nutrient retention decreased as the wetlands aged. Furthermore, the mesocosm planted with Phragmites australis achieved better treatment results compared with the one planted with Agrostis stolonifera. The risk of contamination to groundwater does not exist because none of the treated water reached the bottom outlet during the study period. Both the bentonite (clay) and biogeochemical processes taking place within sediments proved to be efficient in preventing polluted water from infiltrating into lower lying soils.     

Analyzing correlated binary data using SAS

We discuss methods for analyzing repeated binary measurements on the same individual. In spite of the fact that the repeated measurements on the same individual are correlated, the ordinary logistic regression maximum likelihood estimates (which assume that the repeated measures are independent) are consistent and asymptotically normal (K. Y. Liang and S. L. Zeger, Biometrika 73, 13 (1986]. However, the inverse of the estimated information matrix (assuming independence) can give inconsistent estimates of the asymptotic variance of estimated parameters. We describe how to obtain the logistic regression estimates, as well as a consistent estimate of their covariance matrix, in SAS, with minimal matrix manipulations.     

Numerical simulation of dilute turbulent gas‐particle flow with turbulence modulation

A numerical study of a dilute turbulent gas‐particle flow with inelastic collisions and turbulence modulation in an Eulerian framework is described. A new interpretation is provided for the interaction/coupling terms, based on a fluctuating energy transfer mechanism. This interpretation provides for a new robust closure model for the interaction terms with the ability to predict the turbulence dampening as well as the turbulence enhancement phenomenon. Further, the model developed herein is investigated along with a variety of other published closure models used for the interaction/coupling terms, particle drag, and solid stress. The models are evaluated against several sets of benchmark experiments for fully‐developed, turbulent gas‐solid flow in a vertical pipe. © 2011 American Institute of Chemical Engineers AIChE J, 2012     

The development of canola oil based bio‐resins

Bio‐based resins made from vegetable oils offer a sustainable alternative to petroleum‐based thermoset resins. The thermosetting resin systems we have developed from epoxidized canola oil and the polyurethanes we have produced from canola oil‐based polyols show promise as cost‐effective materials incorporating a high renewable content. Here we outline the use of canola oil based bio‐resins in composite boards, and in polyurethane adhesive and insulating foam applications.     

Conversion of Polycrystalline Al2O3 into Single-Crystal Sapphire by Abnormal Grain Growth

In a given batch more than 30%–40% of polycrystalline, MgO-doped Al₂O₃ tubes were converted into single crystals of sapphire by abnormal grain growth (AGG) in the solid state at 1880°C. Most crystals grew 4–10-cm in length in tubes with wall thicknesses of 1/2 and 3/4 mm and outer diameters of 5 and 7 mm, respectively, and had their c -axes oriented ∼ 90° and 45° to the tube axis. Initiation of AGG was associated with low values of bulk MgO concentration near 50 ppm. The unconverted tubes did not develop centimeter-size crystals but instead exhibited millimeter-size grains. The different grain structures in converted and unconverted tubes may be related to nonuniform concentration of MgO in the extruded tubes. The growth front of the migrating crystal boundary was typically nonuniformly shaped, and the interface between the single crystal and the polycrystalline matrix was composed of many "curved" boundary segments indicative of classical AGG in a single-phase material. The average velocities of many migrating crystal boundaries were quite high and reached ∼1.5 cm/h. The average grain boundary mobility at 1880°C was calculated as 2 × 10⁻¹⁰ m³/(N·s), representing the highest value reported so far in Al₂O₃ and within a factor of 2.5 of the calculated intrinsic mobility. Under similar experimental conditions sapphire crystals did not grow when a codopant of CaO, La₂O₃, or ZrO₂ was added in concentrations of several hundred ppm.     

Influence of normal contact force model on simulations of spherocylindrical particles

How the choice of elastic normal contact force model affects predictions from discrete element method simulations of spherocylindrical particles is investigated in this article. Three force models were investigated: (1) a Hertzian force model (HFM) which assumes a circular contact area; (2) a linear force model (LFM) with a constant stiffness; and (3) a modified HFM (MFM) that accounts for various contact areas and contact transitions. With the MFM, transitions between contact area types must be accounted for otherwise discontinuities in the contact force can occur. It is found that simple force models (HFM, LFM) can be substituted for more accurate force models if only force data and bulk properties are of interest. However, if more detailed contact information, such as contact area, contact overlap, contact duration, or collision frequency, are needed, for example, in population balance models and transient liquid bridge modeling, then a more accurate force model should be used. © 2018 American Institute of Chemical Engineers AIChE J, 64: 1986–2001, 2018     

Effect of catalyst type on the kinetics of the photoelectrochemical disinfection of water inoculated with E. coli

The rates of the photoelectrochemical disinfection of Escherichia coli at TiO₂ electrodes were measured as a function of concentration and applied potential. Two different TiO₂ photoelectrodes were used: a thermally treated titanium plate and a porous film prepared by a sol–gel hydrolysis technique. The kinetics of the disinfection process were found to depend upon the nature of the electrode material. For the thermal film they were first order, and half order for the sol–gel film. It was also found that the catalytic activity per unit surface area of catalyst is many orders of magnitude greater than that observed using TiO₂ slurries; this was attributed to the reduced rate of electron-hole recombination afforded by the application of a small potential bias (1 V vs Ag/AgCl), and hence the exploitation of the electric field enhancement (EFE) effect.     

Strength Degradation and Failure Mechanisms of Electron-Beam Physical-Vapor-Deposited Thermal Barrier Coatings

Failure mechanisms were determined for electron-beam physical-vapor-deposited thermal barrier coating (TBC) systems from the degradation of mechanical properties and microstructural changes in a furnace cycle test. Bond strength degradation for TBCs resulted from the initiation and growth of interfacial delamination defects between the yttria-stabilized zirconia topcoat and the thermally grown alumina (TGO). It is proposed that defects started from concave depressions in the bondcoat surface created by the grit-blast-cleaning process and that defect growth was driven by the reduction in compressive strain in the TGO as the alumina deformed into and displaced the bondcoat during the cooling cycles. Inclusion of yttrium in the substrate resulted in a doubling of the furnace cycle life of the TBCs because of enhanced fracture toughness of the TGO-bondcoat interface.     

LONG-TERM PERFORMANCE OF HOLLOW FIBRE MEMBRANE SOLVENT EXTRACTION MODULES USED FOR Cr(VI) RECOVERY FROM ELECTROPLATING RINSE WATER

ABSTRACT

The long-term performance of a hollow fibre membrane solvent extraction unit has been investigated for the recovery of Cr(VI) from plating rinse water. A pilot scale experiment was performed in a local electro-plating plant using-membrane modules with an area of 0·17 m². The separation of Cr(VI) from the rinse liquor was carried out in two hollow fibre membrane modules, and is compared with a single module supported liquid membrane (SLM) which was also used in the same service. The Cr(VI) flux declined gradually to half the initial value after 25 days. This was found to be due to the membrane fouling combined with the degradation of organic solvent. The loss of organic solution was initially severe but stabilized after a few days and became negligible. The flux in the SLM mode appeared similar but the life time was very short, less than a day, however continuous operation was attainable by periodic replenishment of the membrane. Using both designs, it has been shown that Cr(VI) could be extracted from dilute feed into the stripping solution with an enrichment factor of 10 – 20 times using this technique.