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631.
IntroductionThebrassylicacidmanufacturingwastewatercontainshighchemicaloxygendemand(COD)concentration3000—12000mg/LanditsBOD5/CODisamong04—05Meanwhilethewastewatercontainshighsulphateconcentrationabout13000mg/LanditspHvalueisonly1—2Achemicalcompanyappliedneutrali… 相似文献
632.
633.
The major issues in water and wastewater industry are to meet quality requirements, to guarantee treatment process efficiency, to contain investment and operating costs. This implies the use of powerful predictive modeling and simulation tools which are able to account for the multiple interaction between all the water quality and process design parameters. Computational Fluid Dynamics modeling tools have already been widely used in other industries but their application in water industry is quite recent. This paper presents different applications of CFD modeling to the study of the hydro-dynamic and mass transfer performance of single- or two-phase flow reactors used in water and wastewater treatment. Numerical simulations, together with experimental measurements, have been performed on laboratory and full-scale plants in order to gain a better under-standing of the physical phenomena (mixing, interfacial transfer) occurring in these systems. Numerical simulations are systematically validated by experiments. The paper shows how CFD can be helpful in order to improve the design of existing water treatment plants and the process efficiency. In this scope, CFD enables designs more reliable and cost effective water treatment processes which remain basic environmental policy issues. 相似文献
634.
Kinetic processes of alpha-naphthaleneacetic acid (NAA) photolysis were studied under different conditions. The results showed that the ultraviolet light was more effective than fluorescent light in promoting degradation, and the degradation of NAA under ultraviolet light followed the first order kinetics with the photolysis rate constant of 1.15 x 10(-2) min-1 and half-life time (t1/2) of 60 min. Further, it was proved that the photolysis rate was higher in the presence of oxygen, titanium dioxide (TiO2), and low pH (acidic solution). At last, two photolysis intermediates were identified by GC-MS and possible photolysis pathways were proposed. 相似文献
635.
636.
Growth and reproductive processes in synchronous cultures of the alga Scenedesmus armatus (isolated from Baltic phytoplankton) were followed in the presence of various concentrations of dispersant DP-105, oil, and mixtures of oil and dispersant. The inhibition of protoplast fission was the most prominent effect of oil. Nuclear division was inhibited to a lesser extent. With an increasing concentration of oil, dispersant, or a mixture of both, the inhibitory effects were expressed earlier. The presence of oil compounds did not effect the timing of DNA replication, but it did reduce the number of replication rounds in a concentration dependent manner. The inhibition of DNA synthesis was accompanied by slightly delayed cessation of RNA and protein synthesis. Starch synthesis was always inhibited to a lesser extent, and at a later time, than other macromolecular syntheses. Pigment synthesis continued almost to the end of the cell cycle. Thereafter, a rapid degradation of all pigments began and the cells became bleached. No inhibitory effect on reproductive processes was found if oil or dispersant were added to cultures transferred into darkness. Furthermore, recovery from inhibition of reproductive processes caused by oil in continuously illuminated cultures was observed in darkened cells. Chemically dispersed fuel oil was only slightly more toxic than mechanically dispersed fuel oil; an additive, rather than synergistic, effect of oil/dispersant mixture was found. 相似文献
637.
Abbas MZ Bruns RE Scarminio IS Ferreira J 《Environmental pollution (Barking, Essex : 1987)》1993,79(3):225-233
With the aim of estimating the chemical composition of bulk precipitation (wet + dry) in Cubat?o, rainwater samples were collected at several localities in the Cubat?o region from May 1984 to October 1985. The levels of some inorganic ions (Na+, Ca2+, K+, Mg2+, Cl-, SO4(2-), NH4+, PO4(3-)) were measured by atomic absorption spectrophotometry, turbidimetry and titration analysis. Correlation and Fisher discrimination indices, principal component and varimax loading and scores were determined in the multivariate statistical data treatment. The results showed that ionic concentrations in rainwater from Vila Parisi are significantly higher than those of Cubat?o Centro, Santos and Serra do Mar. The ionic compositions of the Vila Parisi rainwater seem to be mainly determined by local anthropogenic activities (industrial pollution). Besides the influence of this factor on water quality, there is also a natural oceanic contribution involving Cl- and Na+ at the other locations. 相似文献
638.
IntroductionTheBashangregionissituatedateastlongitude113°50′-118°00′andnorthlatitude40°58′-42°42′,withanareaof17371km2fromZhangjiakouofnorthernHebeitothenorthofChengde.TheregionliesinthemiddlesectionofatransitionzonefromagriculturaltopastoralregionsofnorthernChina… 相似文献
639.
The dilemma of chromosomal mosaicism in chorionic villus sampling—‘direct’ versus long-term cultures
R. Nisani Dr J. Chemke R. Voss Z. Appelman B. Caspi A. Lewin H. Dar A. Reiter 《黑龙江环境通报》1989,9(4):223-226
Chromosomal mosaicism is one of several unanswered dilemmas in first-trimester prenatal diagnosis. We report the course of a pregnancy in which a normal karyotype was detected on direct CVS preparation and fetal blood, 100 per cent trisomy 21 in one long-term CVS culture, and low-rate trisomy 21 mosaicism in a second long-term CVS culture and amniocentesis. The phenotypically normal infant had a 6 per cent mosaicism of trisomy 21. It appears that a persistent low-rate mosaicism in different tissues may be indicative of the true status of the fetus. 相似文献
640.
This study investigates the mechanism of photosensitization and the recombination of excited electron–hole pairs affected by depositing platinum (Pt) on the surface of titanium dioxide (TiO2). A new catalyst of Pt–TiO2 was prepared by a photoreduction process. Being model reactions, the photocatalytic oxidation of methylene blue (MB) and methyl orange (MO) in aqueous solutions using the Pt–TiO2 catalyst was carried out under either UV or visible light irradiation. The experimental results indicate that an optimal content of 0.75%Pt–TiO2 achieves the best photocatalytic performance of MB and MO degradation and that the Pt–TiO2 catalyst can be sensitized by visible light. The interaction of Pt and TiO2 was investigated by means of UV–Vis absorption spectra, photoluminescence emission spectra, and X-ray photoelectron emission spectroscopy. The Pt0, Pt2+ and Pt4+ species existing on the surface of Pt–TiO2, and the Ti3+ species existing in its lattice may form a defect energy level. The Pt impurities, including Pt, Pt(OH)2, and PtO2, and the defect energy level absorb visible light more efficiently in comparison with the pure TiO2 and hinder the recombination rate of excited electron–hole pairs. 相似文献