Drinking Water Production from Well Water with High Sulfur and Sulfur Bacteria Content

Problems with treatment of Ahaste well water (Audru Parish, P?rnu County, Estonia) were studied in field conditions. The groundwater contains a significant amount of sulfur, from which at pH = 7.5–8.0 about 70–90% is in the form of hydrogen sulfide ion and 30–10% in the form of dissolved H2S. After aeration in the summer, this water formed an unknown slimy microbial mass with a distinct sulfuric odor, which clogged the aeration tanks, catalytic filters, and even the distribution network up to the consumers. After laboratory analyses, it was established that this unknown microbial mass is obviously the filiform sulfur bacteria Thiothrix, together with particles of free sulfur. It was found that this mass formed during enrichment under warm conditions using air as the oxidizer. Under these conditions, elemental sulfur was liberated and created favorable conditions for the Thiothrix to thrive using the elemental sulfur as their food source. A new treatment technology for this well water was developed using ozone as a strong oxidant/disinfectant, followed by filtration through an Everzit-Special, a material, which besides filtration, partially behaves as an adsorbent. The capital and operation costs of the new technology were estimated.     

Quantifying Biomediated Ground Improvement by Ureolysis: Large-Scale Biogrout Experiment

Biogrouting is a biological ground improvement method, in which microorganisms are used to induce carbonate precipitation in the subsurface in order to increase the strength and stiffness of granular soils. In this paper the results of a large-scale experiment (100?m3) are presented, in which the feasibility of biogrouting as a ground improvement method is investigated using techniques and equipment similar to those used in potential applications. In situ geophysical measurements were used to monitor the biogrouting process during treatment and indicated that the stiffness had increased significantly after one day of treatment. The results of unconfined compressive strength tests on samples which were excavated after treatment were used to assess the distribution of mechanical properties throughout the cemented sand body, which correlated quite well with the results of the in situ geophysical measurements. The stiffness increase could be quantified as a function of the injected volume of grouting agents and the distance from the injection points. These results will serve as an important benchmark for future applications of biomediated ground improvement.     

Ground Water under Direct Influence of Surface Water

The Surface Water Treatment Rule and the Interim Enhanced Surface Water Treatment Rule classify some ground-water sources as “ground water under the direct influence of surface water” (GWUDI), and ground waters classified as GWUDI must follow the same treatment guidelines as surface-water sources. The microscopic particulate analysis (MPA) method is the most widely used method to identify GWUDI; however, this method has several deficiencies. An improved protocol for classifying ground-water sources as GWUDI is presented in this paper. The procedure consists of calculating the absolute risk of illness from waterborne Giardia and Cryptosporidium in the pumped water, accounting for the uncertainty in the surface-water concentrations, hydrogeology, straining characteristics, pathogen viability in ground water, and observations of Giardia and Cryptosporidium in samples of the pumped water. In cases where the risk of illness exceeds the acceptable risk, the ground water should be classified as GWUDI. Two examples are presented to illustrate the application of the proposed method.     

六氟化钨净化工艺研究

工业制备的初级六氟化钨含有大量杂质气体和金属杂质,必须进行净化,其过程首先采用化学试剂置换去除杂质气体中沸点与六氟化钨接近的氟化氢,然后将反应后的六氟化钨蒸馏至精馏釜中进行低温固化,再利用真空系统抽真空排出其他杂质气体,初步净化后的六氟化钨检测合格,可直接进行精馏去除金属杂质。经过多步净化后,成品六氟化钨的纯度可达99.999%以上。     

高纯六氟化钨制备工艺研究

介绍了利用氟气与钨粉为原料制备高纯六氟化钨的工艺方法和设备体系。其过程是利用电解槽电解氟氢化钾制取氟气,并采用氟化钠吸附配合深冷工艺纯化氟气,净化后的氟气与固定床里的钨粉在一定温度条件下反应合成初级六氟化钨,通过低温冷凝回收,收集的初级六氟化钨经过固化后抽真空排轻等方法进行初步提纯,然后将初步提纯的产品蒸馏至填料式精馏塔内进行深度提纯,经过多步提纯后的成品六氟化钨纯度可达99.999%以上。     

Laminar Surface Water Flow over Vegetated Ground

This study examines low Reynolds number flow over vegetated sloping ground. Instead of using the traditional empirical formula related to resistance or frictional roughness, a new approach is presented by considering the flow inside the vegetation layer as porous media flow governed by Biot’s poroelastic theory as well as inside the soil layer. There is a discrepancy in the velocity distributions of flow over vegetative mantle area and bare area, respectively. Due to the change of the vegetation density, the effects of vegetation porosity and vegetation blockage on surface water flow are discussed.     

常压蒸馏提取硫磺渣中的元素硫

对硫化锌精矿高压酸浸后的硫磺渣进行常压蒸馏提取元素硫的工艺研究，分析影响蒸馏过程的因素。结果表明采用常压蒸馏的方法能较好地脱除硫磺渣中的元素硫并得到硫磺，硫磺纯度达98％以上，试验残渣含硫可降为24．48％，为化合态的硫。     

水射流土锚扩孔方法的研究

介绍了土层锚杆孔扩孔的三种方法,分析了它们各自的优缺点,着重介绍了近年来出现的新方法———水射流法,通过实验论证了它的可行性和良好的扩孔效果。还提出了一种把土锚钻机改进成水射流扩孔系统的方案,钻孔扩孔一次完成,极大的提高了生产效率。     

Analytical Modeling of Nitrogen Dynamics in Soils and Ground Water

An analytical model, known as RISK-N, is developed to simulate nitrogen cycling in soils, and nitrate transport and fate in soils and ground water. The soil is separated into upper-root, lower-root, and intermediate-vadose zones, each with uniform properties. Transport in each soil zone is modeled on the basis of complete mixing. Transport in the aquifer, however, is modeled using a two-dimensional advection-dispersion transport equation. A simulation is made with a hypothetical corn plot, using meteorological, soil, hydrologic, and hydrogeological data for the South Platte River region of northeastern Colorado. Sensitivity analyses are performed on model parameters. This study shows that the RISK-N model is capable of simulating nitrate leaching rates, as well as ground-water concentrations, that are consistent with those obtained by numerical models, while requiring fewer input variables.     

Alternative Sorbents for Removing MTBE from Gasoline-Contaminated Ground Water

The objective of this work is to provide a preliminary screening of the effectiveness of alternative sorbents for treating ground water contaminated with methyl tert-butyl ether (MTBE). Sorbents studied include synthetic carbonaceous resins, porous graphitic carbon, C18 silicas, and acrylic resins. Activated carbon was also tested for comparison purposes. Bottle point isotherms show that porous graphitic carbon and two synthetic carbonaceous resins have a greater capacity for MTBE than activated carbon. However, the required addition of a wetting agent to suspend and activate the porous graphitic carbon makes this sorbent unsuitable for drinking water purposes. The synthetic carbonaceous resins tested were found to have capacities three to five times greater than activated carbon at an MTBE concentration of 1 mg∕L. The application of the Dubinin-Astakov isotherm to data for the synthetic carbonaceous resins suggests that the mechanism of adsorption is micropore filling. Additional bisolute experiments with m-xylene as a representative gasoline contaminant indicate that the m-xylene is preferentially sorbed, depleting the micropore volume available for MTBE sorption. The extent of this competitive adsorption was directly predicted from measured concentrations of the monoaromatic hydrocarbon.     

地下水生物除铁的探索性试验研究

通过试验反复验证了滤柱的生物除铁效果,结果表明,生物除铁主要是铁细菌的作用.对影响生物除铁的条件,如滤速、过滤周期、反冲洗强度等因素进行了考察,并得到相关指标,为实际生产应用提供了依据.     

转炉使用低硫铁水冶炼时熔池硫含量变化规律

分析了某厂300t转炉使用低硫铁水冶炼时熔池硫含量的变化规律及影响因素,结果表明：废钢的熔化是熔池硫含量升高的主要原因,钢渣间的脱硫反应主要发生在吹炼的后期,降低废钢比,保持吹炼后期炉渣较高的碱度及较低的氧化铁量有利于得到较低的熔池终点硫含量。     

Behavior of Large-Scale Rectangular Columns Confined with FRP Composites

This paper focuses on axially loaded, large-scale rectangular RC columns confined with fiber-reinforced polymer (FRP) wrapping. Experimental tests are conducted to obtain the stress-strain response and ultimate load for three field-size columns having different aspect ratios and/or corner radii. Effective transverse FRP failure strain and the effect of increasing confining action on the stress-strain behavior are examined. Existing strength models, the majority of which were developed for small-scale specimens, are applied to predict the structural response. Since some of them fail to adequately characterize the test data and others are complex and require significant calculation, a simple design-oriented model is developed. The new model is based on the confinement effectiveness coefficient, an aspect ratio coefficient, and a corner radius coefficient. It accurately predicts the axial ultimate strength of the large-scale columns at hand and, when applied to the small-scale columns studied by other investigators, produces reasonable results.     

基坑施工中的地下水处理以及工程实例

介绍井点降水法在基坑施工中地下水处理的应用情况以及工程实例。     

不确定离散时滞大系统的鲁棒稳定性

对于一类具有时变时滞以及非线性不确定性的离散大系统,考虑了其鲁棒稳定性问题.基于Lyapunov泛函方法及矩阵范数不等式方法,提出了这类时滞大系统的时滞无关鲁棒稳定性判据,所得判据条件由一族Lyaunov方程以及代数不等式给出,计算简单,验证方便.最后以一个数值实例表明了本文所得结论的正确性.     

Large-Scale Testing of Two Flat Roof Assemblies Insulated with Cellulose

A laboratory test using a large-scale environmental chamber has been carried out on two flat roof models fully insulated with cellulose fiber. These two models represent the most representative single-cavity flat roofs, built in Montreal between 1930 and 1970, being insulated as part of an energy conservation program. The insulating strategy consists of packing cellulose fiber in the cavity. The goal of the test program was to determine the risk of rotting of the wood structure and moisture accumulation in the roof assembly. The test was performed using real-scale huts that were exposed to 6 months of winter and summer conditions. Two roof assemblies were each divided into five roof cavities. The main variables were the mode of moisture transfer (diffusion only and diffusion combined with air exfiltration), type of vapor barrier, and air leakage paths. The construction of the huts and the monitoring plan are described. The results of the 6-month test program using seven simulated climatic conditions are presented. Wetting and drying curves for different parts of the assemblies as well as the levels of exposure to moisture are presented and analyzed.