Biofilm growth and characteristics in an alternating pumped sequencing batch biofilm reactor (APSBBR)

A novel biofilm reactor-alternating pumped sequencing batch biofilm reactor (APSBBR)-was developed to treat synthetic dairy wastewater at a volumetric chemical oxygen demand (COD) loading rate of 487 g COD m(-3) d(-1) and an areal loading rate of 5.4 g COD m(-2) d(-1). This biofilm reactor comprised two tanks, Tanks 1 and 2, with two identical plastic biofilm modules in each tank. The maximum volume of bulk fluid in the two-tank reactor was the volume of one tank. The APSBBR was operated as a sequencing batch biofilm reactor with five operational phases-fill (25 min), anoxic (9 h), aerobic (9 h), settle (6 h) and draw (5 min). The fill, anoxic, settle and draw phases occurred in Tank 1. In the aerobic phase, the wastewater was circulated between the two tanks with centrifugal pumps and aeration was mainly achieved through oxygen absorption by micro-organisms in the biofilms when they were exposed to the air. In this paper, the biofilm growth and characteristics in the APSBBR were studied in a 98-day laboratory-scale experiment. During the course of the study, it was found that the biofilm thickness (delta) in Tank 1 ranged from 1.2 to 7.2 mm and that in Tank 2 from 0.5 to 2.2 mm; the biofilm growth against time (t) can be simulated as delta=0.07t0.99 (R2 = 0.97, P = 0.002) in Tank 1 and delta = 0.08t0.66 (R2 = 0.81, P = 0.04) in Tank 2. The biomass yield coefficient, Y, was 0.18 g volatile solids (VS) g(-1) COD removal. The biofilm density in both tanks, X, decreased as the biofilm thickness increased and can be correlated to the biofilm thickness, delta .     

Survey of air pollution in Cotonou, Benin--air monitoring and biomarkers

Exposure to genotoxic compounds present in ambient air has been studied in Cotonou, Benin, a city where two-stroke motorbikes are the major form of transportation and gasoline quality is poor. Personal monitoring and biomarkers were used to assess the exposure. Non-smoking taxi-moto drivers (city) and village residents were the study subjects. Benzene exposure was significantly higher in the city, as compared to the village (76.0+/-26.8 microg/m(3) versus 3.4+/-3.0, p=0.0004). Urinary excretion of benzene and S-phenylmercapturic acid (S-PMA) were also highest in subjects living in the city, whereas 1-hydroxypyrene was not different. The level of total polycyclic aromatic hydrocarbons (PAHs), associated with particles, ranged from 76.21 to 103.23 in Cotonou versus 1.55 ng/m(3) for the village. Determination of DNA damage in lymphocytes showed that subjects from the city had elevated number of lesions compared to subjects in the village in terms of bulky DNA adducts, 8-hydroxy-2'-deoxyguanosine and 5-methylcytosine, whereas DNA fragmentations analysed by alkaline gel electrophoresis was not different between the subjects. In conclusion, this study shows that air pollution is pronounced in Cotonou, Bénin and is associated with elevated levels of DNA damage in residents of the city compared to people living in a non-polluted rural village.     

Production of granola breakfast cereal by fluidised bed granulation

In the fluidised bed granulation process the effect of nozzle air pressure and binder spray rate on key aggregate quality attributes were studied. The experimental results show that a decrease in nozzle air pressure leads to larger mean granule size. The combination of lowest nozzle air pressure and lowest binder spray rate results in granules with the highest levels of hardness and crispness. The combination of low nozzle air pressure and low binder spray rate results in the least distribution span. Granola hardness was affected by nozzle air pressure. Nozzle air pressure and binder spray rate did not have significant effect on crispness.     

Raman spectroscopic evidence for the formation of silicomolybdic entities on a Mo/HY zeolite catalyst

Mo/Ze catalysts prepared by incipient wetness impregnation of a Faujasite zeolite with ammonium heptamolybdate solutions have been characterized after calcination at 500 °C and transfer in wet atmosphere. Raman spectroscopy clearly evidences the formation of [SiMo₁₂O₄₀]⁴⁻ heteropolyanions. This formation, through extraction of Si atoms, is not observed before the calcination, the Anderson [AlMo₆O₂₄H₆]³⁻ entity being the main species formed during the impregnation–maturation.     

Reactivity of Ru-based catalysts in the oxidation of propene and carbon black

The relationship between the state of Ru on different supports and catalytic activity in the oxidation of propene and carbon black was investigated for catalysts prepared by different impregnation methods. It is demonstrated that the addition of ruthenium to ceria (CeO₂), alumina (Al₂O₃) and ceria–alumina significantly improves the reactivity: the temperature of carbon black oxidation decreases by 100–140 °C. It is also shown that the addition of Ru to the different supports is very beneficial for the total oxidation of propene. Temperature programmed reduction (TPR) experiments of the catalysts showed that the oxygen species of ruthenium oxides are reduced at low temperatures which is the main reason of its high reactivity in oxidation reactions.     

Influence of Cobalt Content on the Hydrotreatment Catalytic Activity of CoMo6/γ-Al2O3 Heteropolyoxomolybdate-Based Catalyst

The influence of Co content in the catalytic activity in hydrotreatment reactions (hydrodesulfurization (HDS) of thiophene and hydrogenation (HYD) of cyclohexene) using CoMo₆/γ-Al₂O₃-type catalysts, where the precursor is Co(III) heteropolymolybdate of (NH₄)₃[CoMo₆O₂₄H₆?7H₂O formula and Anderson-type planar structure, (hereafter CoMo₆) was investigated. The preparation of catalysts was carried out by the coimpregnation of γ-alumina with CoMo₆ and (NH₄)₆[TeMo₆O₂₄]?]7H₂O (TeMo₆) in order to obtain catalysts with variable amounts of Co(III) keeping about the same Mo amount. The Anderson phase of Te(VI), (TeMo₆) was chosen because of its good solubility and because no promoting effect of the Te was observed in hydrotreatment. Five catalysts were prepared by coimpregnation of γ-Al₂O₃ by using aqueous solutions of both phases in different proportions. Catalysts with a ratio [Co]/([Co] + [Mo]) between 0 and ～0.14 and a Mo loading (wt% Mo) between 8 and 10 were obtained. The Raman and diffuse reflectance (DR) spectroscopies were used for the characterization of bulk and supported CoMo₆ phase. By analyzing the respective adsorption isotherms and parameters and according to the catalytic tests, it could be established that HDS as well as HYD activities of the catalysts increase as a function of the added Co.     

Ni based catalysts promoted with cerium used in the steam reforming of toluene for hydrogen production

Ni_xMg_6?xAl_1.8Ce_0.2 (with 0 ≤ x ≤ 6) mixed oxides catalysts were prepared by hydrotalcite route. All the oxides were calcined at 800 °C and characterized by different physico-chemical methods. The catalysts are then reduced before their use in the steam reforming of toluene. The XRD and TG/DTA confirmed the formation of the hydrotalcite structure for the non-calcined samples. The N₂ adsorption/desorption results revealed that all catalysts correspond to mesoporous materials. The study by temperature programmed reduction (H₂-TPR) showed that the reducibility of the catalysts is influenced by the nickel content. The CO₂-TPD results showed that the catalyst with high magnesium content present the highest basicity. The Ni₂Mg₄Al_1.8Ce_0.2 shows the best toluene conversion among all the catalysts and it was then compared to a non-promoted catalyst. The spent catalysts were characterized by TPO, TG/DTA and XRD and they didn't reveal any coke formation.     

Genesis of new HDS catalysts through a careful control of the sulfidation of both Co and Mo atoms: Study of their activation under gas phase

Impregnation of oxidic precursor with thioglycolic acid aqueous solution was successfully used to improve the performances of thiophene hydrodesulfurization catalysts. Raman, EXAFS and XPS studies indicate that addition of this chelating agent affects the sulfidation of the supported metals. The higher catalytic performances were attributed to an optimization of the nature and morphology of the active phase obtained by the use of this chelating agent which permits a simultaneous sulfidation of both Co and Mo atoms.