Polymer-Ceramic Composite Membranes for Water Removal in Membrane Reactors

Methanol can be obtained through CO₂ hydrogenation in a membrane reactor with higher yield or lower pressure than in a conventional packed bed reactor. In this study, we explore a new kind of membrane with the potential suitability for such membrane reactors. Silicone–ceramic composite membranes are synthetized and characterized for their capability to selectively remove water from a mixture containing hydrogen, CO₂, and water at temperatures typical for methanol synthesis. We show that this membrane can achieve selective permeation of water under such harsh conditions, and thus is an alternative candidate for use in membrane reactors for processes where water is one of the products and the yield is limited by thermodynamic equilibrium.

Infrared sensor-based temperature control for domestic induction cooktops

In this paper, a precise real-time temperature control system based on infrared (IR) thermometry for domestic induction cooking is presented. The temperature in the vessel constitutes the control variable of the closed-loop power control system implemented in a commercial induction cooker. A proportional-integral controller is applied to establish the output power level in order to reach the target temperature. An optical system and a signal conditioning circuit have been implemented. For the signal processing a microprocessor with 12-bit ADC and a sampling rate of 1 Ksps has been used. The analysis of the contributions to the infrared radiation permits the definition of a procedure to estimate the temperature of the vessel with a maximum temperature error of 5 °C in the range between 60 and 250 °C for a known cookware emissivity. A simple and necessary calibration procedure with a black-body sample is presented.

Occurrence and levels of phages proposed as surrogate indicators of enteric viruses in different types of sludges

A method based on the treatment of sludge with beef extract recovered, with similar efficiency, the three groups of bacteriophages studied from different kinds of sludges. The three groups of bacteriophages were found in high numbers in the different sludge types, the highest value being that of somatic coliphages in primary sludge of a biological treatment plant (1.1 x 10(5) pfu g-1) and the lowest being that of Bacteroides fragilis phages (110 pfu g-1) in de-watered, anaerobically, mesophilically-digested sludge. All phages studied accumulated in the sludges. In primary and activated sludges, all three types accumulated similarly but in lime-treated sludge and de-watered, anaerobically, mesophilically-digested sludge, the relative proportion of F-specific bacteriophages decreased significantly with respect to somatic coliphages and bacteriophages infecting B. fragilis. All phages survived successfully in stored sludge, depending on the temperature, and again, F-specific bacteriophages survived less successfully than the others.

Phages of enteric bacteria in fresh water with different levels of faecal pollution

Levels of somatic and F-specific coliphages, and phages infecting Bacteroides fragilis were measured in 257 samples collected in different freshwater environments with different levels and characteristics of faecal pollution. In samples with recent pollution of domestic origin, the numbers of the three groups of phages were highly correlated, thus showing that their excretion is fairly constant. In this set of samples somatic coliphages, which were the most abundant, and F-specific coliphages outnumbered significantly Bact. fragilis phages. Normalized lines of the numbers of the three groups of phages in water samples and their sediments show that they settle similarly. The correlation between the values of the three groups of phages was not observed in waters with intermediate levels of pollution. An increase in the relative numbers of coliphages with respect to numbers of phages infecting Bact. fragilis was observed. In waters with persistent faecal pollution a dramatic change was recorded in the relative numbers of the different groups of phages. Phages infecting Bact. fragilis suffered the lowest reduction in numbers.

Effect of distance from the polluting focus on relative concentrations of Bacteroides fragilis phages and coliphages in mussels

Concentrations of fecal bacteria, somatic and F-specific coliphages, and phages infecting Bacteroides fragilis in naturally occurring black mussels (Mytilus edulis) were determined. Mussels were collected over a 7-month period at four sampling sites with different levels of fecal pollution. Concentrations of both fecal bacteria and bacteriophages in mussel meat paralleled the concentration of fecal bacteria in the overlying waters. Mussels bioaccumulated efficiently, although with different efficiencies, all of the microorganisms studied. Ratios comparing the levels of microorganisms in mussels were determined. These ratios changed in mussels collected at the different sites. They suggest that bacteriophages infecting B. fragilis and somatic coliphages have the lowest decay rates among the microorganisms studied, with the exception of Clostridium perfringens. On the contrary, concentrations of F-specific coliphages showed a greater rate of decay than the other bacteriophages at sites more distant from the focus of contamination. Additionally, levels of enteroviruses were studied in a number of samples, and in these samples, the B. fragilis bacteriophages clearly outnumbered the enteroviruses. The results of this study indicate that, under the environmental conditions studied, the fate of phages infecting B. fragilis released into the marine environment resembles that of human viruses more than any other microorganism examined.