OPTIMIZATION OF INTERMITTENT PUMPING SCHEDULES FOR AQUIFER REMEDIATION USING A GENETIC ALGORITHM1

ABSTRACT: Using a genetic algorithm (GA), optimal intermittent pumping schedules were established to simulate pump‐and‐treat remediation of a contaminated aquifer with known hydraulic limitations and a water miscible contaminant, located within the Duke Forest in Durham, North Carolina. The objectives of the optimization model were to minimize total costs, minimize health risks, and maximize the amount of contaminant removed from the aquifer. Stochastic ground water and contaminant transport models were required to provide estimates of contaminant concentrations at pumping wells. Optimization model simulations defined a tradeoff curve between the pumping cost and the amount of contaminant extracted from the aquifer. For this specific aquifer/miscible contaminant combination, the model simulations indicated that pump‐and‐treat remediation using intermittent pumping schedules for each pumping well produced significant reductions in predicted contaminant concentrations and associated health risks at a reasonable cost, after a remediation time of two years.     

提供生物稳定饮用水的最佳工艺

研究由预处理、常规处理和深度处理组合而成的 7种不同工艺对饮用水源水中可生物同化有机碳 ( AOC)的去除效果 .试验表明 :生物陶粒预处理对 AOC具有较高的去除率 ,达到 45%左右 ,如果在它之前先经过预臭氧化 ,生物处理的去除率可增大到 58.4% ;常规处理对 AOC的去除非常有限 ,去除率平均在 2 0 %左右 ;新活性炭单元因其吸附作用对 AOC的去除效果稳定在30 %左右 ,如和臭氧氧化连用 ,去除效果能提高到 50 %以上 ;包括了常规处理、生物预处理、预臭氧和臭氧活性炭的组合工艺对AOC的去除效果最好 ,达到 86% .因此臭氧氧化、生物炭和生物处理是提高饮用水生物稳定性的重要手段 ,并以本试验结果为依据提出了对于不同的水源水所采用的最佳工艺 .     

基于随机有限元可靠度的RC结构抗火设计参数优化方法

本文较详细地分析了各设计参数对RC结构抗火能力的影响。在已知结构抗火功能函数的基础上利用随机有限元可靠度的计算方法分析各参数对结构抗火能力的敏感性,根据各参数敏感性的不同,在设计时有意识地对该参数作一些较小的变动,结构的可靠度会明显的增加从而提高了结构的抗火能力。为RC结构抗火设计提供了一种参数优化的方法。     

基于数字流域的水文过程模拟研究

考虑流域下垫面空间变异性,基于数字高程模型构建了数字流域,并在此基础上对描述流域水文物理过程的数学方法进行了探讨,文章认为,数字水文模型是一种有物理基础的包含大容量信息的现代模拟灌河实例研究表明,数字水文模型可以十分方便地输出水文要素和状态变量的空间分布与时间序列,这对充分利用现有观测信息进行水文信息的深层挖掘创新了条件。     

Photochemical behaviour of musk tibetene

BACKGROUND: Synthetic musk compounds are widely used as additives in personal care and household products. The photochemical degradation of musk tibetene in aqueous solutions or in acetonitrile/water mixtures under different conditions was studied in order to assess its environmental fate. METHODS: Musk tibetene dissolved (or suspended) in water and/or acetonitrile/water mixtures was irradiated at different times by UV-light and by solar light. The irradiation mixtures were analyzed by NMR and TLC. The photoproducts formed were identified by GC-MS and NMR data. RESULTS: The experimental results indicated that musk tibetene was photodegradable in water or acetonitrile/water mixtures with half-life reaction times close to 20 minutes. The irradiation mixtures were separated by chromatographic techniques yielding three photoproducts (3,3,5,6,7-pentamethyl-4-nitro-3H-indole, 3,3,5,6,7-pentamethyl-4-nitro-1H-indoline and 3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone) identified by means of spectroscopic analysis. DISCUSSION: The numerical modelling of the photodegradation concentration-time profiles gave (8.13 +/- 0.15) x 10(-2) and (1.34 +/- 0.04) x 10(-2) mol/E for the overall primary quantum yield of direct photolysis for musk tibetene and the major intermediate (3,3,5,6,7-pentamethyl-4-nitro-3H-indolinone), respectively, in the wavelength range 305-366 nm. The half-life times of photodegradation of the both substances varied from 1-1.5 hours at 20 degrees N during the summer season to 6-10 hours for highest latitudes in winter. CONCLUSIONS: Under solar light, musk tibetene was photolabile in acetonitrile and acetonitrile/water 1/1, while it was slowly degraded when suspended in water. In all media, musk tibetene was photodegraded into three photoproducts. By using a kinetic model, the overall primary quantum yields of direct photolysis of musk tibetene and its main photoproduct, in the wavelength range 305-366 nm, were estimated, indicating that the photodegradation rate for musk tibetene is faster than the photolysis rate of the major by-product. RECOMMENDATIONS AND PERSPECTIVES: The results indicate that, in order to assess the environmental impact of musk tibetene on the aquatic ecosystem, great attention should be focused on the major photoproduct which is proved to be more persistent than the parent compound under light irradiation. The predicted half-life times of direct photolysis for both substances ranged from 1-1.5 hours at 20 degrees N during the summer season to about 6-10 hours for highest latitudes in winter, indicating that, from a photochemical point of view, the environmental persistence of these substances increases by increasing the latitudes and during the cold seasons, making more realistic an intake of these xenobiotic molecules into the food chain of aquatic living organisms. Tanabe reports in his Editorial (Tanabe 2005) that "It is necessary to have knowledge of the global picture of synthetic musk pathways. So, it is conceivable that now is the time to study the transport, persistency, distribution, bioaccumulation and toxic potential of this new environmental menace on a global scale, especially in developing countries". Therefore, the future environmental analysis and investigations on the eco-toxicity of nitro musk compounds should take into account not only the presence of the parent compounds but also their photochemical intermediates or end-by-products.     

Landfill leachate treatment methods: A review

Landfilling of municipal waste is still a major issue of the waste management system in Europe. The generated leachate must be appropriately treated before being discharged into the environment. Technologies meant for leachate treatment can be classified as follows (i) biological methods, (ii) chemical and physical methods. Here we review briefly the main processes currently used for the landfill leachates treatments.     

人工甜味剂环境行为研究进展

人工甜味剂是一类人工合成或半合成的蔗糖取代物,由于人们对饮食健康的关注而被越来越广泛地应用于食品和饮料中.但是大多数人工甜味剂在人体内几乎不被代谢就随尿液和粪便直接排到生活污水中.近年,几种典型的甜味剂在水体中广泛被检出且浓度较高,同时研究发现部分甜味剂难以降解,因此人工甜味剂已被视为新型有机污染物而得到关注.本文就人工甜味剂在水处理设施中的行为及其在环境来源和分布的相关研究进行了综述,总结了水处理设施和水环境中甜味剂的污染特征规律,并对今后的研究进行了展望.     

专家系统在废水生物处理操作和控制中的应用

本文介绍了国外近二十年来专家系统在废水生物处理工艺控制领域的应用及开发的典型系统,分析了废水生物处理工艺难于控制的原因、各类系统的结构和特点及目前废水处理专家系统的不足,探讨了废水生物处理专家系统今后应深入研究的问题及方向     

WATERSHED FUNCTIONS1

ABSTRACT: Watershed functions that dominate the hydrologic environment are identified and discussed. Hydrological and ecological functions are considered in relation to the storm and annual hydrographs, and to water quality. Two integrative watershed responses to these functions are also articulated. Since most of the Earth's water is in storage, consideration of the hydrologic cycle as movement between water storage sites enhances this functional and response characterization of the watershed which, in turn, suggests guidance and direction for the restoration of watershed functions.