Verification of Full-Scale Ozone Contactor Inactivation Performance Using Biodosimetry

A biodosimetric technique was used to verify the concentration-contact time (CT) values [CT10, CT integrated disinfection design framework (CT-IDDF), CT segregated flow analysis (CT-SFA)] of the ozone contactors of the DesBaillets water treatment plant (Montreal), using indigenous aerobic spore formers (ASFs) as indicators of disinfection efficiency. ASF measurement in ozonated water was performed using a large water sample concentration method. Four assays, completed over a 6-week period, involved the implementation of biodosimetric calibration curves using an ozone pilot apparatus and followed by full-scale verifications. ASF inactivation kinetics were well described by a simple Chick–Watson model. The most accurate data also indicated that the CT10 underestimates the effective CT (by 1.2–1.9-fold), whereas the CT-IDDF and CT-SFA overestimate it (by 1.0–1.7-fold and 0.9–1.5-fold, respectively). Underestimation from CT10 was more pronounced with increased ozone dose while overestimation from CT-IDDF and CT-SFA is most likely due to the difficulty in obtaining a representative ozone residual profile within the contactor. The use of segregated flow analysis provided the best estimate of disinfection performance. Biodosimetry is useful in measuring the effective CT transferred, in verifying model predictions, and in determining the influence of water quality on microbial inactivation.     

Oxide scale formation on Al containing Ni–Cr‐based high temperature alloys during application as flame tube material in recirculation oil burners

The flame tube is an important functional component of burners using the concept of the flame tube stabilised combustion. Under typical combustion conditions the material of the flame tube is exposed to high temperatures (≥900 °C) and to corrosion attack by the combustion gases. Furthermore as the burners are generally operated intermittently, the material suffers from extreme temperature and atmosphere changes. For flame tubes, a lifetime of approximately 8000 h is desired. Predominantly metallic high temperature materials are used. The scope of the present work was to test—under application conditions and for maximum material temperatures exceeding 900 °C—alternative high temperature alloys for use as tube material. The corrosion resistance of the austenitic Ni–Cr‐based alloys (601, 602 CA, 617 and 693) has been investigated in a burner rig at maximum material temperatures of 950 and 1000 °C and with exposure times from 50 to 3000 h. The chromium content of the alloys was between 20 and 30 wt% and that of aluminium between 1 and 3.4 wt%. Metallographic cross‐sections of samples of the alloys were analysed by electron microprobe yielding information about the microstructure and composition of the oxides in the surface zone and variations during exposure time. This study focuses on the observed specific effects of the alloying element aluminium on the development of the oxide scale and on the lifetime of the alloys. At the alloy surface after 500 h exposure time a chromium oxide scale had formed with aluminium oxides underneath predominantly along grain boundaries. For the alloys with the lower aluminium content, the aluminium oxides built up an open network but not a closed layer. For the alloy with the highest aluminium content (alloy 693) after 50 h two different characteristic microstructures at the surface were found. In one case, the grains at the surface were covered with chromium oxide on top and the remaining grain surface was completely enclosed by aluminium oxides. In the other case, the aluminium oxide formed a thin layer directly below the chromium oxide scale. After 500 h exposure time, a significantly thinner chromium oxide scale and massive internal chromium oxides were observed. Catastrophic corrosion, formation of internal oxides and aluminium nitrides started even after 500 h. It will be demonstrated that the early breakdown of alloy 693 is linked to the aluminium oxides which act as a barrier constricting the diffusion of chromium from the alloy matrix towards the surface. Under the conditions of extreme temperature changes given in the burner the aluminium oxide layer on its part did not provide corrosion protection.     

The inhibition by substrate analogues of gamma-aminobutyrate aminotransferase from mitochondria of different subcellular fractions of rat brain

Cytoplasmic-mitochondria-enriched and synaptosome-enriched subcellular fractions were prepared from rat brain to study certain kinetic properties of gamma-aminobutyrate: alpha-oxoglutarate aminotransferase (GABA-T) (EC 2.6.1.19) from each of the sources. From this study two differences emerged. Firstly, the cytoplasmic enzyme exhibited an eightfold greater affinity for gamma-aminobutyric acid (GABA) than did the synaptosomal GABA-T; the Km being 6.5 mM and 53 mM, respectively. Secondly, synaptosomal GABA-T is comparatively more susceptible to inhibition by the substrate analogues 2,4-diaminobutyric acid (DABA) and aminooxyacetic acid (AOAA) than is the enzyme from the cytoplasmic mitochondrial fraction. In each case the inhibition was of a competitive nature with respect to GABA. The Ki for the DABA was 13 mM for the cytoplasmic-derived enzyme and 8mM for the synaptosomal enzyme. With AOAA the Ki was 0.1 muM and 0.06 muM for the synaptosomal and cytoplasmic mitochondrial enzyme, respectively. These results provide further evidence that GABA-T from cytoplasmic mitochondria is different in several respects from the enzyme found in synaptosomes.     

From strange bedfellows to natural allies: the shifting allegiance of fire service organisations in the push for federal fire-safe cigarette legislation

Background: Cigarettes are the leading cause of fatal fires in the USA and are associated with one in four fire deaths. Although the technology needed to make fire-safe cigarettes has been available for many years, progress has been slow on legislative and regulatory fronts to require the tobacco industry to manufacture fire-safe cigarettes. Method and results: We conducted a case study, drawing on data from tobacco industry documents, archives, and key informant interviews to investigate tobacco industry strategies for thwarting fire-safe cigarette legislation in the US Congress. We apply a theoretical framework that posits that policymaking is the product of three sets of forces: interests, institutions, and ideas, to examine tobacco industry behaviour, with a special focus on their and others'' attempts to court fire service organisations, including firefighters'' unions as allies. We discuss the implications of our findings for future policy efforts related to fire-safe cigarettes and other tobacco control issues. Conclusions: Tobacco control advocates ought to: continue efforts to align key interest groups, including the firefighters unions; contest tobacco industry "diversionary" science tactics; and pursue a state based legislative strategy for fire-safe cigarettes, building towards national legislation.     

The effect of dry heat on the bioavailability of iron in soy flour

Bioavailability of iron in soy flour was investigated by the Hemoglobin Regeneration Efficiency (HRE) procedure in 50 three-month-old Sprague-Dawley rats. Rats weighing 250 ±7 g and with a mean hemoglobin level of 12.9 g/dl were randomly assigned to one of five treatment groups: baseline (BL), unheated soy flour (UH), soy flour heated at 225°F for either 10 min (H10), 30 min (H30), or 120 min (H120). The animals were fed diets (46 ppm iron) containing the soy flour for 21 days. HREs of UH, H10, H30, H120 diets were 17.6, 16.8, 17.7 and 16.8%, respectively. Apparent iron absorption from the UH, H10, H30 and H120 diets was 94.7, 94.3, 93.9 and 94.3%, respectively. Serum iron was significantly lower (p<.001) and total iron binding capacity was significantly higher (p<.001) in rats fed the H120 diet. Iron concentrations in the liver, spleen, heart and kidney were significantly lower in rats fed H30 or H120 diets. These results suggest that prolonged heating of soy flour may reduce iron bioavailability and result in depletion of iron stores.     

Impact of UV/H(2)O(2) advanced oxidation treatment on molecular weight distribution of NOM and biostability of water

The presence of natural organic matter (NOM) poses several challenges to the commercial practice of UV/H₂O₂ process for micropollutant removal. During the commercial application of UV/H₂O₂ advanced oxidation treatment, NOM is broken down into smaller species potentially affecting biostability by increasing Assimilable Organic Carbon (AOC) and Biodegradable Organic Carbon (BDOC) of water. This work investigated the potential impact of UV/H₂O₂ treatment on the molecular weight distribution of NOM and biostability of different water sources. A recently developed flow cytometric method for enumeration of bacteria was utilized to assess biological stability of the treated water at various stages through measurement of AOC. BDOC was also assessed for comparison and to better study the biostability of water. Both AOC and BDOC increased by about 3-4 times over the course of treatment, indicating the reduction of biological stability. Initial TOC and the source of NOM were found to be influencing the biostability profile of the treated water. Using high performance size exclusion chromatography, a wide range of organic molecule weights were found responsible for AOC increase; however, low molecular weight organics seemed to contribute more. Positive and meaningful correlations were observed between BDOC and AOC of different waters that underwent different treatments.