Comparative Metagenomic Analysis of Electrogenic Microbial Communities in Differentially Inoculated Swine Wastewater-Fed Microbial Fuel Cells.

Bioelectrochemical systems such as microbial fuel cells (MFCs) are promising new technologies for efficient removal of organic compounds from industrial wastewaters, including that generated from swine farming. We inoculated two pairs of laboratory-scale MFCs with sludge granules from a beer wastewater-treating anaerobic digester (IGBS) or from sludge taken from the bottom of a tank receiving swine wastewater (SS). The SS-inoculated MFC outperformed the IGBS-inoculated MFC with regard to COD and VFA removal and electricity production. Using a metagenomic approach, we describe the microbial diversity of the MFC planktonic and anodic communities derived from the different inocula. Proteobacteria (mostly Deltaproteobacteria) became the predominant phylum in both MFC anodic communities with amplification of the electrogenic genus Geobacter being the most pronounced. Eight dominant and three minor species of Geobacter were found in both MFC anodic communities. The anodic communities of the SS-inoculated MFCs had a higher proportion of Clostridium and Bacteroides relative to those of the IGBS-inoculated MFCs, which were enriched with Pelobacter. The archaeal populations of the SS- and IGBS-inoculated MFCs were dominated by Methanosarcina barkeri and Methanothermobacter thermautotrophicus, respectively. Our results show a long-term influence of inoculum type on the performance and microbial community composition of swine wastewater-treating MFCs.

Diamond grinding wheels production study with the use of the finite element method.

Research results on 3D modeling of the diamond grain and its bearing layer when sintering diamond grinding wheels are provided in this paper. The influence of the main characteristics of the wheel materials and the wheel production process, namely the quantity of metallic phase within diamond grain, coefficient of thermal expansion of the metallic phase, the modulus of elasticity of bond material and sintering temperature, on the internal stresses arising in grains is investigated. The results indicate that the stresses in the grains are higher in the areas around the metallic phase. Additionally, sintering temperature has the greatest impact on the stresses of the grain-metallic phase-bond system regardless of the type of the bond. Furthermore, by employing factorial design for the carried out finite element model, a mathematical model that reflects the impact of these factors on the deflected mode of the diamond grain-metallic phase-bond material system is obtained. The results of the analysis allow for the identification of optimal conditions for the efficient production of improved diamond grinding wheels. More specifically, the smallest stresses are observed when using the metal bond with modulus of elasticity 204 GPa, the quantity of metallic phase in diamond grain of not higher than 7% and coefficient of thermal expansion of 1.32 × 10-5 1/K or lower. The results obtained from the proposed 3D model can lead to the increase in the diamond grains utilization and improve the overall efficiency of diamond grinding.

Multi-electrode microbial fuel cell with horizontal liquid flow.

A plug flow multi-electrode bioelectrochemical reactor for wastewater treatment and simultaneous generation of electricity has been developed and its efficiency investigated. It employs a horizontally located anodic zone in which the anodic electrodes comprise porous graphite plates coated with palladium. The aerated immersed cathodic electrodes contain iron(II) phthalocyanine as a catalyst. The parameters of the device were obtained using glycerol and acetate as fuels and anaerobic sludge as an inoculum. The maximal volumetric power and current densities obtained, relative to the total volume of the anodic zone, were: glycerol: 73+/-1 mA/L; 43+/-1 mW/L; acetate: 75+/-1 mA/L; 40+/-1 mW/L. It was shown that biotransformation of glycerol into volatile fatty acids does not depend on the presence of anodic electrodes in the reaction zone, while acetate degradation takes place only if the reaction zone contains anodic electrodes as a final electron acceptor.

Kinetics of anaerobic biodecolourisation of azo dyes.

Kinetics of anaerobic biodecolourisation (methanogenic environment) of four azo dyes (Acid Orange 6, Acid Orange 7, Methyl Orange and Methyl Red) was investigated with regard to their electrochemical properties as well as under variation of dye and sludge concentrations, pH and temperature. Cyclic voltammetry revealed a correlation between the potential of irreversible reduction peak of the dye and its first-order decolorisation constant. For each dye tested, this decolourisation constant was adversely proportional to dye concentration (0.086-1.7 mM) and had a saturation (hyperbolic) dependency on sludge concentration (0.04-1.1 g VSS/l), a bell-shape dependency on pH (4.0-9.0) and Arrhenius dependency on temperature (24-40 degrees C). Transfer from methanogenic to sulphate reducing environment led to an increase of decolorisation constant for all the dyes investigated due to the abundant presence of sulphide as a reducing agent in the reaction medium. Similar transfer to a denitrifying environment resulted in an almost complete decease of decolourisation because nitrate easily outcompetes azo dyes as an electron acceptor.

[Choice of renal replacement therapy in patients with complicated uremia]. / Vybor metodov zamestitel'noi pochechnoi terapii u bol'nykh s oslozhnennoi uremiei.

Fourteen patients with complicated uremia and multiple organ dysfunction syndrome were treated by renal replacement therapy (RRT), by hemodialysis and hemodiafiltration. Control group consisted of 14 age-matched convalescents without clinical and laboratory signs of uremia and systemic inflammatory response syndrome. The potentialities of Integral Diagnostic Expert Analytical System (IDEAS) based on the spectrophotokinetic (SPK) technique (ECOTEST, Russia; Thermo Labsystems, Finland) were evaluated on the basis of objective evaluation of clinical condition of end-stage renal disease patients. SPK technology proved to be a highly informative method of automated diagnosis, which allows monitoring the dialysis efficiency, detecting combined diseases and poor system's biocompatibility, which, in turn, permits correction of the treatment and realization of a differentiated approach to the choice of RRT method.

Use of hydrophobic membranes to supply hydrogen to sulphate reducing bioreactors.

This paper reports on the application of hydrophobic membranes to supply the gaseous substrates hydrogen/carbon dioxide (H2/CO2) to a sulphate reducing bioreactor. For this, two flat 0.016 m2 sheets of flouroplast microporous (0.45 microm) membranes were inserted in a 3.6 dm3 bioreactor for the supply of H2/CO2 gas as small gas bubbles. The bioreactor was operated at 30 degrees C and pH 7.0 and was also equipped with an external ultra filtration module for biomass retention. At a sulphate loading rate (SLR) of 1.32 g SO4(2-) dm(-3) day(-1) and a hydraulic retention time (HRT) of 61 h, a sulphate reduction rate (SRR) of 0.90 g SO4(2-) dm(-3) day(-1) was achieved. When the influent sulphate concentration was reduced from 3.36 to 0.75 g SO4(2-) dm(-3) by lowering the HRT to 10.3 h (SLR of 1.75 g SO4(2-) dm(-3) day(-1) the SRR dropped to 0.22 g SO4(2-) dm(-3) day(-1). The lower sulphate reduction efficiency was most probably caused by a too short biomass-substrate contact time or by irreversible sulphide inhibition. Mass transfer limitation of H2 and improper mixing of the reactor liquid were shown not to contribute to the low sulphate reduction efficiency.

[A new rapid automated photometric method in analysis of quantitative indicators of food product contamination]. / Novaia avtomatizirovannaia fotometricheskaia ékspress-metodika dlia analiza kolichestvennykh pokazatelei obsemenennosti produktov pitaniia.

Thirty-five specimens of pasteurized milk were tested for bacterial contamination by rapid autocalibration photometry for liquid, semiliquid, and homogenized hard foodstuffs, developed by the Ecotest Firm, Russia. Photometric (turbidimetric) analysis was carried out using the Labsystems (Finland) iEMS Reader plate photometer and Russian Analitika BACT software. The results of traditional analysis and the new rapid method developed by Ecotest were in good correlation, the differences did not surpass the magnitude of errors of measurements. The new method takes just 10-15 h instead of the routine 72 h and requires 300 times less nutrient media.

Mathematical modelling as a tool to study population dynamics between sulfate reducing and methanogenic bacteria.

The existing mathematical models of sulphate fed anaerobic reactors are reviewed. Special attention was put on pecularities of the description of sulphide inhibition and competition between sulphate reduction and methanogenesis in such systems. The paper also presents an integrated mathematical model of the functioning of a sulphate fed granular sludge reactor taking into account concentration gradients on substrates, intermediates, products and bacteria inside the reactor as well as multiple-reaction stoichiometry and kinetics. The developed model includes the following blocks: a) hydrodynamic block describing liquid flow as well as transport and distribution of the components along the reactor height; b) kinetic block including growth, metabolism, inhibition and competition of acidogenic, acetogenic, methanogenic and sulphate reducing bacteria in the system; c) physico-chemical block for calculation of pH in each compartment of the liquid phase; d) transfer block describing a mass transfer of gaseous components from the liquid to the gas phase. The integrated model was calibrated and validated using laboratory studies on the functioning of sulphidogenic granular sludge reactors, i.e. their start-up and the maximization of sulphide yield in these reactors. The modelling of the reactor operation is supplemented with hypothetical computer simulations to illustrate the influence of engineering parameters on the operation performance and sulphate conversion of sulphidogenic reactors.