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821.
Estimation of primary drainage three-phase relative permeability for organic liquid transport in the vadose zone 总被引:4,自引:0,他引:4
The modeling of transport of organic liquid contaminants through the vadose zone often requires three-phase relative permeabilities. Since these are difficult to measure, predictive models are usually used. The objective of this study is to assess the ability of eight common models to predict the drainage relative permeability to oil in a three-phase system (water-oil-air). A comparison of the models' estimates using data set from Oak [Oak, M.J., 1990. Three-phase relative permeability of water-wet Berea. In: Seventh Symposium on Enhanced Oil Recovery, Paper SPE/Doe 20183. Tulsa, OK, April 22-25] showed that they provide very different predictions for the same system. The goodness of the models does not increase with the amount of data or computation that the models require. Also, the calculations showed how different interpretations of the models and of the terminology associated with them can significantly impact the predictions. Thus, considerable error may be introduced into the simulations of organic liquid transport in the vadose zone depending on the selection and interpretation of the three-phase relative permeability model. 相似文献
823.
824.
Semi-permeable membrane devices (SPMDs) are passive samplers that have been designed to sample the bioavailable fractions of hydrophobic organic compounds in aquatic ecosystems. This study aims at evaluating the ability for SPMD to sample polycyclic aromatic hydrocarbons (fluoranthene, pyrene and benzo[a]pyrene) that are actually bioavailable to Daphnia magna. For that purpose, the SPMD-available fraction and the bioavailable fraction to D. magna are compared in controlled media with Dissolved Organic Matters (DOMs) from various origins and at different concentrations. The presence of all but one DOM reduces the accumulation of PAHs in SPMD or in D. magna. Moreover, this comparative laboratory study shows that in 10 cases on 13, the SPMD-available fraction is close to the available fraction to D. magna. When significant differences are observed between SPMD-available and bioavailable fractions, they remain less than 50% at DOM concentrations below 10 mg/l DOC, which corresponds to a maximum DOC concentration usually found in temperate rivers. This study confirms the suitability of the SPMD technique to monitor readily bioavailable hydrophobic contaminants in aquatic environments containing DOM from various origins and characteristics. 相似文献
825.
Stepnowski P Storoniak P 《Environmental science and pollution research international》2005,12(4):199-204
- Aims and Background. Ionic liquid application in industry will offer several excellent solutions, but it also means that they
will enter the environment sooner or later. Responsible product design should always take into consideration not only technological
demands, but also the risks arising out of possible toxicity and ecotoxicity. In our strategy we are aiming to understand
the fate of these entities through their life cycle in the environment as a complimentary element of their design. This paper
presents results on the lipophilicity of selected imidazolium ionic liquids, a parameter that plays a key role in environmental
and biological distribution. Additionally, the prediction of the most stable metabolite of a 1-butyl-3-methylimidazolium (BMIM)
cation – a congener representative of this group of compounds is presented.
Materials and Methods Lipophilicity was evaluated by means of reversed phase and immobilized artificial membrane chromatography and further compared
to calculated data. Theoretical prediction of lipophilicity was undertaken using fragmental methodology combined with manual
calculations of the geometric bond factor for quaternary ammonium and the electronic bond factor due to the presence of a
charge.
Results and Discussion All the substances studied are characterized by very low partition coefficients, and lipophilicity varies linearly with elongation
of the n-alkyl chain. Prediction of metabolic routes was based solely on thermodynamic data of the radical intermediates formed
during the reaction with the cytochrome P450 system. The energetically most stable radical structure is generated by hydrogen
abstraction from the gamma position of the BMIM cation.
Conclusions and Recommendations. The experimentally measured and theoretically estimated lipophilicity coefficients obtained for all the
compounds studied generally indicate a relatively low lipophilicity and thus preferable partition to the aqueous phase. By
means of thermodynamic data, it was also confirmed that the energetically most stable radical structure is generated by hydrogen
abstraction from the gamma position on the alkyl chain in the 1-alkyl-3-methylimidazolium cation, as a result of which the
C1 atom is preferentially oxidized.
- * The basis of this peer-reviewed paper is a presentation at the 9th FECS Conference on 'Chemistry and Environment', 29 August
to 1 September 2004, Bordeaux, France. 相似文献
826.
用自组装的膜吸收器试验研究了不同操作条件下的烟气脱硫特性。实验结果表明,脱硫过程传质阻力主要集中在气相和膜上,利用螺旋管技术可以强化气相的传质。 相似文献
827.
将循环活性污泥系统(Cyclic Activated Sludge System,CASS)与膜过滤技术组合为一体式膜生物反应器(Submerged Membrane Bioreactor,SMBR),研究其用于生活污水回用处理的可行性,对该工艺的适宜运行条件进行了研究.结果表明,水力停留时间(HRT)为4 h、DO在2.0~3.5 mg/L、温度控制在常温、pH在6.5~8.0的运行条件是比较经济高效的.并考察了装置对实际生活污水的处理效果,结果表明出水水质优异,优于中水回用标准(CJ 25.1-89). 相似文献
828.
829.
采用生物膜与悬浮生长强化处理工艺,提高了高负荷生物滤池后续活性污泥的抗冲击负荷和可生化性.综合了生物滤池与活性污泥法各自的优越性,提高了处理效果. 相似文献
830.
一体式膜生物反应器处理生活污水的中试研究 总被引:1,自引:0,他引:1
采用中试规模(1.8m^3/d)的缺氧-好氧膜生物反应器(A/OMBR)对城市污水处理回用进行了试验研究。试验结果表明,该工艺处理效果优良,系统对COD、氨氮、浊度、总氮、总磷去除率较高,COD、氨氮出水浓度分别为7~39 mg/L、0~1.31mg/L。出水水质优于城市杂用水水质标准(GB/T18920-2002)。 相似文献