两段接触氧化法处理生活污水的工程实例

本污水厂设计规模 70 0 0m3 d ,进水CODCr3 0 0mg L ,BOD515 0mg L ,SS 2 0 0mg L ,采用两段接触氧化法处理工艺 ,运行结果表明 ,出水水质达到GB8978 1996污水综合排放标准中的二级标准     

Rapid prediction of disinfection by-product formation potential by fluorescence

Recent drinking water regulations have lowered the disinfection by-product standards as well as added new disinfection by-products for regulation. Natural organic matter (NOM) plays a major role in the formation of undesirable organic by-products following disinfection/oxidation of drinking water. It is suspected that most precursors to disinfection by-products are humic, although nonhumic substances are also suspected of contributing to these by-products. Many of the disinfection by-products have adverse health effects in humans (i.e., carcinogenic or mutagenic effects). The primary chlorinated disinfection by-products of concern include trihalomethanes, haloacetic acids, and haloacetonitrile. Fluorescence spectroscopy was used to study humic and fulvic acids. The two fractions of humic substances, humic and fulvic acids, were characterized by a double-peak phenomena in an overlapping fluorescing region. Disinfection by-product formation potentials of humic and fulvic acids have been correlated with total organic carbon, UV absorbance at 254 nm, specific absorbance and fluorescence. River humic and fulvic acid was found to have the highest reactivity to disinfection by-product formation as compared to soil and peat humic and fulvic acid. Fluorescence spectroscopy has shown to be a rapid and predictive tool for disinfection by-products formation potential of humic and fulvic acids.     

Biologie und Biochemie des Elements Selen

The importance of selenium as an essential trace element has progressively emerged during the last years due to the analysis of selenium deficiency diseases and to the identification and characterization of a number of selenoenzymes. Selenium is incorporated in the catalytic site of the enzymes as an integral selenocysteine residue. The pathway of selenocysteine biosynthesis and incorporation has been elucidated recently for Escherichia coli. This article presents an overview on these subjects and describes the mechanisms which confer selenocysteine specificity in the framework of protein biosynthesis. In addition, some considerations concerning the phylogeny of selenocysteine incorporation are presented and a model for the evolution of the selenocysteine pathway is proposed.     

A polyiodide with regular I 4 2− chains: Tl6PbI10

The Science of Nature -     

滇池草海蓝藻清除应急措施总体方案

我国首例大型湖泊蓝藻清除工程中，制订了由湖泊应急治理措施、水资源应急调控措施和行政管理强化措施构成的注重时空需要、突出治标应急和多专业、多技术相互配合的综合应急方案。     

Land use as a mitigation strategy for the water-quality impacts of global warming: a scenario analysis on two watersheds in the Ohio River Basin

This study uses an integrative approach to study the water-quality impacts of future global climate and land-use changes. In this study, changing land-use types was used as a mitigation strategy to reduce the adverse impacts of global climate change on water resources. The climate scenarios were based on projections made by the Intergovernmental Panel on Climate Change (IPCC) and the United Kingdom Hadley Centre's climate model (HadCM2). The Thornthwaite water-balance model was coupled with a land-use model (L-THIA) to investigate the hydrologic effects of future climate and land-use changes in the Ohio River Basin. The land-use model is based on the Soil Conservation Service's curve-number method. It uses the curve number, an index of land use and soil type, to calculate runoff volume and depth. The ArcView programming language, Avenue, was used to integrate the two models into a geographic information system (GIS). An output of the water-balance model, daily precipitation values adjusted for potential evapotranspiration, served as one of the inputs into the land-use model. Two watersheds were used in the present study: one containing the city of Cincinnati on the main stem of the Ohio River, and one containing the city of Columbus on a tributary of the Ohio River. These cities represent two major metropolitan areas in the Ohio River Basin with different land uses experiencing different rates of population growth. The projected hypothetical land-use changes were based on linear extrapolations of current population data. Results of the analyses indicate that conversion from agricultural land use to low-density residential land use may decrease the amount of surface runoff. The land-use practices which generate the least amount of runoff are forest, low-density residential, and agriculture; whereas high-density residential and commercial land-use types produce the highest runoff. The hydrologic soil type present was also an important factor in determining the amount of runoff and non-point-source pollution. A runoff-depth matrix and total nitrogen matrix were created for Cincinnati and Columbus to describe possible land-use mitigation measures in response to global climate change. The differences in Cincinnati and Columbus were due to differences in geographic location, air temperature, and total runoff. The results of this study may be useful to planners and policy makers for defining the possible impacts of future global climate and land-use changes on water resources.     

Technological system for sustainable development of Chinese agriculture

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花键轴冷挤压成形工艺及模具设计

花键轴是机械中广泛使用的重要零件之一。制造工艺复杂,外观质量、尺寸精度、综合机械性能等要求高。采用冷挤压成形,可使成本降低、提高质量、使用可靠。此文对花键轴成形工艺,模具设计作了详细探讨。