Sorption of Heavy Metals onto Nonliving Water Hyacinth Roots

Abstract

Dried water hyacinth (Eichhornio crassipes (Mart.) Solms) roots, when suspended in water, strongly sorb Cd(II) and Pb(II) with Pb(II) more strongly sorbed than Cd(II). The sorption is dependent on factors such as reaction time, pH, concentration of metal ions, temperature, the presence of other metal ions and biomass concentration. In particular. the metal ions are bound to the root biomass in a highly pH dependent manner. Interestingly, Pb(II) is sorbed in concentrations greater than would be expected based on the relative atomic weight of the two metals. The metal ions can readily be desorbed and the roots regenerated. It appears that the roots can be, thus, recycled through at least 50 loading-elution cycles without significant loss of sorption properties. Therefore, there appears to be a considerable advantage to using such dead biomass over the living plants which can be used for only one sorption cycle.     

Effect of In-Lake Water Quality on Pollutant Removal in Two Ponds

An extensive field study examined pollutant removal in two regional wet detention ponds near High Point, N.C. Substantial differences in influent pollutant concentrations between the ponds caused significant differences in pond water quality and pollutant removal efficiency. In Davis Pond, influent fecal coliform and nutrient concentrations were high because of several large dairy farms in the watershed, resulting in hypereutrophic conditions as evidenced by high chlorophyll-a concentrations, high midday pH values and supersaturated midday oxygen concentrations. In Piedmont Pond, influent fecal coliform and nutrient concentrations were much lower, resulting in mesotrophic to slightly eutrophic conditions. Both ponds thermally stratified and developed an anaerobic hypolimnion. In Davis Pond, annual pollutant removal efficiencies for total suspended solids, volatile suspended solids, total organic carbon, total phosphorus, dissolved phosphorus, nitrate∕nitrite, total ammonia nitrogen, and total nitrogen were 56%, 32%, 15%, 41%, 54%, 16%, 2%, and 11%, respectively. In Piedmont Pond, annual pollutant removal efficiencies were 20%, 30%, 27%, 40%, 15%, 66%, ?64%, and 36%, respectively.     

Two-Dimensional SPH Simulations of Landslide-Generated Water Waves

Water waves generated by landslides have been of interest to ocean and coastal engineers, as well as to dam engineers. The present study uses a meshless and pure Lagrangian method known as smoothed particle hydrodynamics (SPH) to simulate nonlinear water waves due to landslides, with the aim of an accurate numerical prediction of the generation and propagation of such water waves. Validation is carried out by comparison between the computed prediction and experimental data of water waves generated by a two-dimensional triangular rigid body sliding into water. The calculated results show that the simulated water waves agree well with those observed in the experiment confirming the effectiveness and the accuracy of the proposed scheme.     

Storm Water Pollutant Removal by Two Wet Ponds in Bellevue, Washington

Two wet detention ponds were investigated for their ability to remove pollutants, primarily phosphorus, from storm water runoff. The two ponds lie within the Phantom Lake watershed, a subbasin of the Lake Sammamish watershed in Bellevue, Wash., which is developed as a commercial and residential area with impervious surface area as high as 57%. There are design differences between the two ponds, yet both are comparable to design recommendations set forth by local agencies. One pond was built for flow attenuation and water quality treatment; the other serves only to improve water quality. Fifteen storms and two baseflows were successfully sampled during the Northwest's wet season from October 1996 through March 1997. Pollutant removals varied between one-fifth and one-half for phosphorus, and greater than one-half for total suspended solids and most of the analyzed metals. Removal efficiencies were consistently better in the pond designed primarily for water quality.     

水葫芦对水溶液中Cu~(2+)、Zn~(2+)的吸附

研究了用水葫芦生物吸附剂从溶液中吸附Cu2+和Zn2+,考察了溶液pH、吸附剂用量、金属离子初始浓度、温度及吸附时间对Cu2+、Zn2+吸附率的影响,探讨了等温吸附、吸附热力学及动力学。结果表明:pH是影响吸附效果的重要因素,pH在2~6范围内,随pH增大,金属离子去除率升高;水葫芦对Cu2+、Zn2+的吸附速度较快,80min左右即达平衡,吸附过程符合准二级动力学模型(R20.999);利用Langmuir等温方程进行拟合,得到水葫芦对Cu2+、Zn2+的最大吸附量分别为26.39和15.11mg/g;吸附热力学参数ΔG0,表明水葫芦对Cu2+、Zn2+的吸附过程可自发进行;水葫芦经3次吸附解吸循环后,仍然保持较高的吸附性能。水葫芦价格低廉,产量大,在重金属废水处理方面有很好的应用前景。     

Three-Dimensional and Depth-Averaged Large-Eddy Simulations of Some Shallow Water Flows

Three-dimensional (3D) and two-dimensional (2D) depth-averaged (DA) large-eddy simulations (LES) are presented for three different shallow-water flows involving large-scale horizontal structures: a mixing layer, the flow around a circular cylinder, and the flow in a groyne field. The results are compared with each other and also with experiments. In the 3D-LES, most of the energy-containing turbulent motions, including the larger subdepth-scale motions, are resolved, while in the 2D-DA-LES the effect of the 3D subdepth-scale turbulence is represented by a quadratic bottom-friction model and a simple eddy-viscosity model. In the case of the mixing layer, an additional stochastic backscatter model is necessary to account for the energy transfer from the subdepth-scale turbulence to the 2D structures in order to generate the latter. The 3D-LES results are generally in good agreement with the experiments, including the evolution of the horizontal structures. The much more economic 2D-DA-LES are somewhat less realistic in detail but also produce results that are generally of sufficient accuracy for practical purposes.     

High-Temperature Rotational Transitions of Water in Sunspot and Laboratory Spectra

Assignments are presented for spectra of hot water obtained in absorption in sunspots (T approximately 3000°C and 750 相似文献   

Laboratory Study of Unidirectional Focusing Waves in Intermediate Depth Water

The results of laboratory measurements of large focusing wave groups, which were generated using the New Wave theory, are presented. The influences of both the steepness and frequency bandwidth on focused wave characteristics were examined. The influence of frequency bandwidth on focused wave groups with small and moderate steepness was very small. However, for cases with the large steepness, the nonlinearity increased with increasing bandwidth frequency and widened free-wave regimes are identified for those cases with large steepness at the focal location. The underlying nonlinear phase coupling of focused waves was examined using wavelet-based bicoherence and biphase, which can detect nonlinear phase coupling in a short time series. For wave groups with large initial steepness, as wave groups approached the focal location, the values of bicoherence between primary waves and its higher harmonics progressively increased to 1 and the corresponding biphase was gradually close to zero, suggesting that an extreme wave event can be produced by considering Stokes-like nonlinearity to very high-order. Furthermore, the fast change of bicoherence of focused wave groups indicates that the nonlinear energy transfer within focusing waves is faster than that of nonfocusing wave trains.     

Storm Water Detention Ponds: Modeling Heavy Metal Removal by Plant Species and Sediments

Laboratory and field studies were conducted to elucidate heavy metal removal by three wetland grasses and sediments in storm water detention pond. The removal of heavy metals including Cd, Cu, Pb, and Zn was mediated by fluid-flow intensity in the reactors. The growth of plants and the removal rates of contaminants were plant species dependent. All three wetland grasses removed contaminants from the spiked nutrient solutions. A first-order kinetic model adequately represented the removal of contaminants by plants. The analyses of undisturbed sediment cores in detention pond revealed strong stratification of heavy metal concentrations at the sediment–water interface. A simple model that integrates heavy metal removal by aquatic plants and sediments in storm water detention ponds is proposed. The model provides an estimate of contaminant residence time which can be related to hydraulic residence time in storm water detention ponds.     

Comparison of the Monod and Droop Methods for Dynamic Water Quality Simulations

The Monod method is widely used to model nutrient limitation and primary productivity in water bodies. It offers a straightforward approach to simulate the main processes governing eutrophication and it allows the proper representation of many aquatic systems. The Monod method is not able to represent the nutrient luxury uptake by algae, which consists of the excess nutrient uptake during times of high nutrient availability in the water column. The Droop method, which is also used to model nutrient limitation and primary productivity, takes into account the luxury uptake of nutrients. Because of the relative complexity of the Droop method, it has not been systematically adopted for the simulation of large stream networks. The Water Quality Analysis Simulation Program (WASP) version 7.1 was updated to include nutrient luxury uptake for periphyton growth. The objective of this paper is to present the new nutrient limitation processes simulated by WASP 7.1 and to compare the performance of the Droop and the Monod methods for a complex stream network where periphyton is the main organism responsible for primary productivity. Two applications of WASP 7.1 with the Droop and Monod methods were developed for the Raritan River Basin in New Jersey. Water quality parameters affecting the transport and fate of nutrients were calibrated based on observed data collected for the Raritan River total maximum daily load. The dissolved oxygen and nutrients simulated with WASP 7.1, obtained with the Droop and Monod methods, were compared at selected monitoring stations under different flows and nutrient availability conditions. The comparison of the WASP 7.1 applications showed the importance of using the Droop method when periphyton was the main organism responsible for primary productivity. The data simulated with the Droop method resulted in good agreement with the observed data for dissolved oxygen, ammonia-nitrogen, nitrate-nitrogen, and dissolved orthophosphate at the selected stations. The Monod method was not able to capture the diel dissolved oxygen variation when nutrients were scarce, and it resulted in unrealistic diel variations of nutrients at times of strong primary productivity at some locations.     

Water Quality Laboratory for Large Civil Engineering Classes

In New Zealand, civil engineering classes are getting larger every year, which means that innovative ways must be sought to enable an increasing number of students to fulfill the laboratory requirements of the degree. With respect to water quality laboratories in introductory environmental engineering courses, it is advocated that it is more important that a civil engineering student be able to interpret water quality data, rather than to be acquainted in detail with the actual mechanics of water quality tests. As such, this paper describes a water quality laboratory that allows the student to gain an appreciation of a water quality data set without necessarily becoming fully conversant with the routine water quality tests. The laboratory’s emphasis on data interpretation instructs students on the importance of examining data sets for patterns, correlations and/or potential errors, while at the same time providing a stimulating and active hands-on learning environment for both students and staff.     

Density Stratification Effects in Sand-Bed Rivers

In this paper the effects of density stratification in sand-bed rivers are studied by the application of a model of vertical velocity and concentration profiles, coupled through the use of a turbulence closure that retains the buoyancy terms. By making the governing equations dimensionless, it is revealed that the slope is the additional dimensionless parameter introduced by inclusion of the buoyancy terms. The primary new finding is that in general density stratification effects tend to be greater in large, low-slope rivers than in their smaller, steeper brethren. Under high flow conditions the total suspended load and size distribution of suspended sediment can be significantly affected by density stratification, and should be accounted for in any general theory of suspended transport.     

鞍钢给水厂虹吸滤池的改造和运行

１概述鞍钢给水厂河水净化车间老区虹吸滤池投产于１９８２年，分两组共２８格，设计能力３６００m３／h，自投产以来，在近２０年的生产运行中，一直处于低负荷运行状态，在使用中也出现了不少问题。２存在问题及原因２．１存在问题２．１．１滤料流失严重，滤层减薄，过滤效果不佳；２．１．２配水系统漏砂严重，堵塞配水廊道，致使过滤和反冲洗功能遭到严重破坏。２．１．３配水不均，反冲洗不均匀，致使滤层中积泥、板结，形成的灰黑色粘状物质难以用水漂洗，只能停池用机械搅拌设备磨洗，严重影响正常生产中的过滤水质。２．２原因分析…     

Assessment of Water Bodies of United Arab Emirates Coastal Sabkhas as Potential Sites for Natural Salinity Gradient Solar Ponds

Increasing population and growing demands from both agriculture and industry in the United Arab Emirates (UAE) necessitate the need to provide inexpensive fresh water. The only feasible source of such water is desalination. The coastal area of the United Arab Emirates especially in Abu Dhabi is formed of a series of hypersaline (47%°) lagoons surrounded by salt-encrusted flat sabkhas. Such water bodies may be used as salinity gradient solar ponds (SGSPs) to generate clean electricity that can be used in desalination plants. The geologic and climatic conditions of this region are compared with El Paso, Texas, USA where there is a well-established SGSP technology. It is concluded that the water and air temperature, solar radiation, and geologic setting support the possibility of using this technology in the UAE and especially in Abu Dhabi. Cost analyses also suggest that the generation of electricity and its use in desalination plants are economically feasible.     

2. Numerical Simulations of Water Flow and Solute Transport Applied to Acid Sulfate Soils

Field investigations of Rassam et al. in 2001 have highlighted the effects of infiltration, drainage, and evapotranspiration on the dynamics of water flow and solute transport in acid sulfate (AS) soils. In this work, HYDRUS-2D is adopted as the modeling tool to elucidate the trends observed in that field experiment. Hypothetical simulations have shown that the relative contribution of drains to lowering the water table is significant only when closely spaced drains are installed in coarse textured soils, evapotranspiration being the main driving force in all other cases. AS soils reaction products that are close to a drain are readily transportable during infiltration and early drainage, but those produced farther away from it near the midpoint between drains are only slowly transported during a prolonged drainage process. Simulating the field trial of Rassam et al. has shown that drain depth and evapotranspiration significantly affect solute fluxes exported to the ecosystem. Managing AS soils should target minimal drain depth and density. Partial or full lining of the drains should be considered as a management option for ameliorating the environmental hazards of AS soils.     

转炉浊环水粗颗粒分离池的改进

转炉污水具有高硬度、高浊度等水质特点.分析了粗颗粒分离机的故障原因,通过对粗颗粒分离池的改进,减少了粗颗粒排放,提高了机器使用寿命.     

Salinity-Induced Density Stratification in Near-Laminar Open-Channel Flows

Salt tracer experiments are a cost-effective tool widely used in studies of flow and transport in free surface flows. Whereas in a large majority of rivers and streams, fully turbulent conditions achieve rapid vertical mixing of injected tracers, this is not necessarily the case with very low Reynolds number flows as encountered e.g., in wetland ponds. There, often laminar to near-laminar transitional flow regimes prevail, and the fact that solutions of elevated salinity are distinctly heavier than water may result in the development of stable density layers, trapping part of the salt tracer and distorting the breakthrough curve recorded at the outlet. In this study, the conditions under which density stratification develops due to salt injection are analyzed, and a criterion is presented which permits an intended salt tracer experiment to be judged at the planning stage already.     

Liquefaction Mapping in Finite-Element Simulations

Recent criteria have been developed to describe the onset of static liquefaction in constitutive models. This paper expands the theory to a finite-element framework in order to predict potentially unstable regions in granular soils at the engineering scale. Example simulations are presented for two plane strain tests and a submarine slope to demonstrate the applicability of a proposed liquefaction criterion to boundary value problems. In addition, loading rate and mesh size effects on the liquefaction prediction are examined. The methodology presented herein shows promise as a means of predicting soil liquefaction based on solid mechanical theory rather than empiricism.     

社会分层视阈下的网络民主研究

所有制形式的多样化和社会分工的专业化导致社会阶层的不断分化,阶层分化的实质就是社会资源占有的不平衡,阶层关系的实质则是利益诉求的多样化,经济领域的阶层分化必然对民主政治发展提出新要求.网络民主应运而生,它规避了阶层、身份的差异,建构较全面的社会关系网络,扩充公民实现民主权利的渠道,进一步优化了民主政治结构.作为一种新兴事物,网络民主也有巨大的提升空间,只有培育理性网民,建立畅通无阻的网络民主疏导渠道,将网络政治制度化、规范化、科学化,才能发挥网络民主应有的效力.