Comparison of recirculation configurations for biological nutrient removal in a membrane bioreactor

A 12-L lab-scale membrane bioreactor (MBR), consisting of an anaerobic and anoxic compartment followed by an oxic plate-frame membrane compartment, was evaluated for carbonaceous and nutrient removals by varying the recirculation of mixed liquor and permeate. The hydraulic retention times (HRTs) for the anaerobic, anoxic, and oxic compartments were 2, 2, and 8h, respectively. The solids residence time (SRT) for the oxic compartment was 25 days. Five different recirculation configurations were tested by recirculating mixed liquor and/or permeate recirculation equal to the influent flow rate (identified as 100%) into different locations of the anaerobic and anoxic compartments. Of the five configurations, the configuration with 100% mixed liquor recirculation to the anaerobic compartment and 100% permeate recirculation to the anoxic compartment gave the highest percentage removal with an average 92.3+/-0.5% soluble chemical oxygen demand (sCOD), 75.6+/-0.4% total nitrogen (TN), and 62.4+/-1.3% total phosphorus (TP) removal. When the mixed liquor and permeate recirculation rates were varied for the same configuration, the highest TP removal was obtained for 300% mixed liquor recirculation and 100% permeate recirculation (300%/100%) with a TP removal of 88.1+/-1.3% while the highest TN removal (90.3+/-0.3%) was obtained for 200%/300% recirculation. TN and TP concentrations as low as 4.2+/-0.1 and 1.4+/-0.2mg/L respectively were obtained. Mass loading rates were generally low in the range of 0.11-0.22kgCOD/kgMLSS/d due to high biomass concentrations within the oxic reactor (approx. 8000mg/L). The BioWin model was calibrated against one set of the experimental data and was found to predict the experimental data of effluent TN, TP, and NO(3)(-)-N but over-predicted sCOD and NH(3)-N for various recirculation rates. The anoxic heterotrophic yield for the calibrated model was 0.2kg biomass COD/kg COD utilized while the maximum growth rates were found to be 0.45day(-1) for mu(max-autotroph), 3.2day(-1) for mu(max-heterotroph), and 1.5day(-1) for mu(max-PAO).     

Conducting Copolymers of 3-Methylthienyl Methacrylate and p-Vinylbenzyloxy Poly(ethyleneoxide) and Their Electrochromic Properties

Summary A random copolymer (CP) containing 3-methylthienyl methacrylate (MTM) and p-vinylbenzyloxy poly(ethyleneoxide) (PEO-VB) units was synthesized. Further graft copolymerization of CP with pyrrole (Py) and thiophene (Th) were achieved in H₂O - sodium dodecyl sulfate (SDS), H₂O - p-toluenesulphonic acid (PTSA) and acetonitrile (AN) - tetrabutylammonium tetrafluoroborate (TBAFB) solvent electrolyte couples via constant potential electrolyses. Characterization was performed by cyclic voltammetry (CV), nuclear magnetic resonance spectroscopy (NMR), and fourier transform infrared spectroscopy (FTIR). The morphologies of the films were examined by scanning electron microscopy (SEM). Conductivities of the samples were measured by using four-probe technique. Moreover, spectroelectrochemical and electrochromic properties of the copolymer obtained from thiophene were investigated by UV-Vis spectrometry and colorimetry.     

A unified solution to the singular and nonsingular linearminimum-variance estimation problem

A unified solution is derived for the transfer function matrix of the minimum-variance estimator of the state of a linear continuous-time system with noisy or noise-free measurements. For the noisy measurement case, the Kalman-Bucy filter standard equations are used to give the general format of the transfer function. The Kalman-Bucy gain, using the spectral factorization on the algebraic in the S plane, is derived and substituted in the transfer-function expression. The singular case is then shown to be a special case of the noisy measurement estimator     

Characterization of poly(N‐(hydroxymethyl)methacrylamide‐ATU) hydrogels synthesized by γ radiation

Poly(N‐(hydroxymethyl)methacrylamide‐1‐allyl‐2‐thiourea), (poly(NHMMA‐ATU)) hydrogels were synthesized by γ radiation, using ⁶⁰Co γ source at different radiation doses, to change the porosity and crosslinking density of the hydrogels. The percent of 1‐allyl‐2‐thiourea (ATU) in the monomer mixture before the irradiation was varied between 2.5% and 10.0%, to increase the content of ATU, which was involved in some different applications in the hydrogels. Fourier transform infrared spectroscopy (FTIR), thermogravimetric analysis (TGA), elemental analysis, and the swelling experiments were used to characterize the poly(NHMMA‐ATU) hydrogels synthesized in this study. Characterization results of hydrogels showed that crosslinking density of the hydrogels was increased by the increasing radiation dose and ATU content in the irradiated mixture. Swellability of these hydrogels was found to be high enough to allow the metal ions and biomolecules getting inside the hydrogels to interact with all active groups on/in the hydrogels in the adsorption applications. Equilibrium swelling ratio of the hydrogels at pH 0.5 is at least half of the equilibrium swelling ratio of the hydrogels at pH 7.0. Oscillatory swelling behavior of poly(NHMMA‐ATU) hydrogels between pH 0.5 and pH 7.0 showed that the hydrogels are quite stable at different pH conditions. © 2005 Wiley Periodicals, Inc. J Appl Polym Sci 99: 1657–1664, 2006     

A new statistical strategy for pooling: ELI

Doing exhaustive relevance judgments is one of the most challenging tasks in the construction process of an IR test collection, especially when the collection is composed of millions of documents. Pooling (or system pooling), which is basically a method for selecting documents to assess, is a solution to overcome this challenge. In this paper, to form such an assessment pool, a new, ranked-based document selection criterion, called the expected level of importance (ELI), is introduced. The results of the experiments performed, using TREC 5, 6, 7, and 8 data, showed that by using a pool in which the documents are sorted in the decreasing order of their calculated ELI scores, relevance judgments can efficiently be made by minimal human effort, while maintaining the size and the effectiveness of the resulting test collection. The criterion we propose can directly be adapted to the traditional TREC pooling practice in favor of efficiency, with no additional cost.     

Relationship Between Growth Speed and Magnetic Properties in Bi-2212/Ag Textured Composites

In this paper, the measured magnetic properties of Bi₂Sr₂CaCu₂O _x /3 wt.% Ag textured composite materials prepared by a LFZ melting technique at different growth speeds (5, 15, 30, and 60 mm/h) are presented. X-ray diffraction patterns have shown that Bi-2212 phase is the major one in all cases. The magnetization measurements have been carried out as a function of the magnetic field up to 10 kOe. J _c values, calculated using Bean’s model, indicate that the growth speeds have a significant effect on J _c . It has been found that the maximum critical current density, 4.42×10⁵ A/cm² at 10 K, has been obtained for the 15 mm/h grown sample.     

Strain gradient elasticity and modified couple stress models for buckling analysis of axially loaded micro-scaled beams

A class of higher-order continuum theories, such as modified couple stress, nonlocal elasticity, micropolar elasticity (Cosserat theory) and strain gradient elasticity has been recently employed to the mechanical modeling of micro- and nano-sized structures. In this article, however, we address stability problem of micro-sized beam based on the strain gradient elasticity and couple stress theories, firstly. Analytical solution of stability problem for axially loaded nano-sized beams based on strain gradient elasticity and modified couple stress theories are presented. Bernoulli–Euler beam theory is used for modeling. By using the variational principle, the governing equations for buckling and related boundary conditions are obtained in conjunctions with the strain gradient elasticity. Both end simply supported and cantilever boundary conditions are considered. The size effect on the critical buckling load is investigated.     

Synthesis and electrochemical,electrical and gas sensing properties of novel mononuclear metal-free,Zn(II), Ni(II), Co(II), Cu(II), Lu(III) and double-decker Lu(III) phthalocyanines substituted with 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl) phenoxy

A new mono substituted phthalonitrile derivative 3 was prepared by a nucleophilic displacement reaction of 4-nitrophthalonitrile with 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenol. Novel metallophthalocyanines 4–8 (M = Zn, Ni, Co, Cu, Lu, respectively), metal free 9 and double decker Lu(III) phthalocyanine 10 with four peripheral 2-(2H-1,2,3-benzotriazol-2-yl)-4-(1,1,3,3-tetramethylbutyl)phenoxy groups were synthesized by cyclotetramerisation of the phthalonitrile and characterized by elemental analyses, FTIR, ¹H NMR, UV–vis and MALDI-TOF MS spectral data. Cyclic voltammetry, differential pulse voltammetry and in situ spectroelectrochemistry of the phthalocyanine compounds have been studied. This allowed us to identify and compare metal- and phthalocyanine ring-based redox processes of the complexes. Impedance spectroscopy (IS) and dc conductivity measurements were performed as a function of temperature (300–430 K) and frequency (40–10⁵ Hz.). The sensing properties of the films for toluene were also investigated. The dc results showed an activated conductivity dependence on temperature for all films. While room temperature impedance spectra consist of a curved line, a transformation into a full semicircle with increasing temperature was observed. The analysis of ac conductivity data showed that the CBH model is the dominant conduction mechanism for the electron transport in the films. While exposure to toluene has no effect on the conductivity of the film of 8–10 completely reversible sensor response to toluene only were obtained for compounds 4–7. It was also observed that the operating temperature had a considerable effect on sensing characteristics of the films.     

Effects of temperature,solid content and pH on the stability of black carrot anthocyanins

Anthocyanin stability of black carrots was studied at various solid contents (11, 30, 45 and 64° Brix) and pHs (4.3 and 6.0) during both heating, at 70–90 °C, and storage at 4–37 °C. Monomeric anthocyanin degradation fitted a first-order reaction model. Degradation of monomeric anthocyanins increased with increasing solid content during heating, while it decreased during storage. For example, at pH 4.3, half-life periods for anthocyanins at 30, 45 and 64° Brix were, respectively, 8.4, 6.9 and 5.2 h during heating at 80 °C and 18.7, 30.8 and 35.9 weeks during storage at 20 °C. At 30–64° Brix, increasing pH from 4.3 to 6.0 enhanced the degradation of anthocyanins during heating. The effect of pH on thermal stability of anthocyanins was also studied at six different pHs (2.5–7.0) in citrate-phosphate buffer solutions and significant decrease in anthocyanin stability was observed at pHs above 5.0. Higher activation energies (E_a) were obtained during heating than during storage with increasing solid contents. At 30–64° Brix, E_a values ranged from 68.8 to 95.1 kJ mol⁻¹ during heating and from 62.1 to 86.2 kJ mol⁻¹ during storage. Q₁₀ values at 20–37 °C were as high as 3.1 at 45° Brix and 3.6 at 64° Brix.