UBF-物理化学组合工艺处理Zn5-ASA医药废水的研究

采用砂滤－UBF厌氧－絮凝沉淀工艺处理高浓度Zn5-ASA医药废水。实验结果表明，对于COD为8000－10000mg/L，色度7000－9000倍的Zn5-ASA废水，加石灰乳和H2SO4预调，经砂滤柱过滤后，COD会去除20％左右；再进以聚丙烯环为填料的厌氧UBF反应器，HRT为10.57h，COD去除率达83％－89％；出水再经化学絮凝沉淀后，无色透明，COD浓度远小于1000mg/L，符合GB8978－96三级排放标准要求，且色度小于10倍。     

Developments in Dutch coastline management: Conclusions from the second governmental coastal report

In 1990 the Dutch government decided to stop any further long-term landward retreat of the coastline. This policy choice for a ‘dynamic preservation’ is primarily aimed at safety against flooding and at sustainable preservation of the values and interests concerning the dunes and beaches. Five years later, a first overview of the benefits and bottlenecks of the new coastal defence policy could be presented, which was published in the second governmental coastal report ‘Kustbalans 1995’ (coastal balance 1995). This consists of three elements: (1) evaluation of the implementation of ‘dynamic preservation’, (2) the consequences of several natural and anthropogenic developments in the coastal zone and (3) integrated coastal zone management. The present report describes experiences of Dutch coastline management and summarizes the main conclusions of the second governmental report. The overall conclusion of the evaluation study is that the 1990 choice for ‘dynamic preservation’ was right. Sand supply is an effective method of coastline maintenance, which also serves functional uses in the beach and dune area. However, nearly a doubling of the supply volume is necessary to compensate for sand losses in the coastal zone. A more integrated management of the coastal zone is necessary to find an equilibrium between the interests of socio-economic development and the maintenance of a natural, dynamic system.     

THE FLEXIBLE TOLERANCE METHOD FOR ESTIMATING HYDROLOGIC PARAMETERS IN THE ROOT ZONE1

In this study, a constrained minimization method, the flexible tolerance method, was used to solve the optimization problems for determining hydrologic parameters in the root zone: water uptake rate, spatial root distribution, infiltration rate, and evaporation. Synthetic soil moisture data were first generated using the Richards' equation and its associated initial and boundary conditions, and these data were then used for the inverse analyses. The results of inverse simulation indicate the following. If the soil moisture data contain no noise, the rate of estimated water uptake and spatial root distribution parameters are equal to the true values without using constraints. If there is noise in the observed data, constraints must be used to improve the quality of the estimate results. In the estimation of rainfall infiltration and surface evaporation, interpolation methods should be used to reduce the number of unknowns. A fewer number of variables can improve the quality of inversely estimated parameters. Simultaneous estimation of spatial root distribution and water uptake rate or estimation of evaporation and water uptake rate is possible. The method was used to estimate the water uptake rate, spatial root distribution, infiltration rate, and evaporation using long‐term soil moisture data collected from Nebraska's Sand Hills.     

Effects of sand movement by wind on nematodes and soil-borne fungi in coastal foredunes

In stabilized dunesAmmophila arenaria (marram grass) degenerates due to a process involving soil-borne pathogens and parasites. This leads to exposure of the sand surface so that wind erosion may create blowouts.Ammophila rejuvenates on the edges of the blowouts, where the sand has accumulated. We tested the hypothesis that such rejuvenation of plants may be related to a reduction of the plant-parasitic nematodes and fungal propagules during the process of wind-driven transport. Field measurements in blowouts during storm events indicated that the drifted sand contained relatively low numbers of plant pathogenic fungi and plant-parasitic nematodes. A wind tunnel experiment showed that drifting sand may indeed reduce the numbers of fungi and nematodes. Although most fungi were attached to sand particles, they were also affected by the wind-borne sand movement. Sand that had been deposited by wind was made up of a larger proportion of large-sized particles. In our experiment the relatively small particles were lost during transport. Stirring the soil (part of the forces of natural winds) by mixing for 15 min. with a propeller mixer at 1500 rpm significantly reduced the number of nematodes and fungi. Both sand movement in the wind tunnel and intensive stirring of the sand enhanced the growth ofAmmophila test plants in a bioassay. It was concluded that in wind-blown sand the pathogen inoculum is reduced. Therefore, serious consideration should be given to allowing controlled reactivation of blowouts to rejuvenate decliningAmmophila in stabilized foredunes. Implications for dune management are briefly discussed. Nomenclature: van der Meijden (1990) for vascular plants. Nematodes were identified to the genus level according to Bongers (1988). The allocation of nematodes to feeding groups was according to Yeates et al. (1993). Nomenclature of fungi according to Domsch et al. (1980) was used throughout this study except forFusarium. Species of the latter genus were identified according to Nelson et al. (1983).     

GEOLOGICAL AND CLIMATIC CONTROLS ON STREAMFLOWS IN THE NEBRASKA SAND HILLS1

ABSTRACT: This paper presents hydrological characteristics of the streamflow of the Dismal, Middle Loup, North Loup, and Cedar Rivers in the Nebraska Sand Hills and their relation to climate and ground water variation. Time series of streamflow, precipitation, temperature, and ground water levels from 1976 to 1998 were used to analyze trends and fluctuations of streamflow and to determine relationships among streamflow, climate, and the ground water system. An increase of precipitation and a decrease of maximum temperature over the period resulted in higher ground water levels and increased streamflow in the region. The high permeability of the soil and the thick unsaturated zone enhance precipitation recharge, limit surface runoff, and prevent ground water losses through evapotranspiration. Thus, an abundance of ground water is stored, supplying more than 86 percent of streamflow in the four rivers. Streamflow is generally more constant in the Sand Hills than elsewhere in the region. The four rivers present different hydrologic characteristics because of the spatial heterogeneity in hydrogeologic conditions. Streamflow of the Dismal and Middle Rivers, which are less sensitive to climatic variation, is much steadier than that of the North Loup and Cedar Rivers.     

Vegetation succession and lichen diversity on dry coastal calcium-poor dunes and the impact of management experiments

The negative impact of grass and moss encroachment on the botanical diversity of West European coastal dunes attracted increasing attention in the 1990s. This paper focuses on moss encroachment during primary succession in the xeroseries. Until the mid-1970s, vegetation types rich in species of the lichen generaCladonia andCladina were found on the fixed,Corynephorus canescens-dominated, so-called grey dunes all over the island of Terschelling, The Netherlands. In addition, species ofHypogymnia, Parmelia andUsnea, which usually grow on trees, occurred here terrestrially on moss carpets or bare sand. These vegetation types are still present on the Noordsvaarder, a nature reserve in the western part of the island. They occur on parts of seven dune ridges parallel to the coast and form a chronosequence in which age increases with distance from the sea. Our study found the highest lichen diversity on the second and third dune ridges in a stage of primary succession that can be assigned to theViolo-Corynephoretum. The changes from lichen-rich to moss-dominated stadia were significantly related to soil development and acidification in connection with the ageing of the dune soil. The superficial cutting of sods in moss-encroached vegetation appeared to be unsuccessful as a management technique for restoring the biodiversity of cryptogams. Our findings suggest that the best option for maintaining lichen vegetation in theViolo-Corynephoretum is the blow-in of sand with a subneutral or neutral pH from reactivated and natural blowouts or from foredunes, with increasing lime content respectively.     

场地液化危害的概率分析

为使场地液化危害程度的估计建立在以概率论为基础的可靠性分析之上,本文提出二种估计场地液化危害程度的概率方法,二种方法分别采用不同的途径处理地震和岩土的不确定性,不仅分析了一点液化的概率,而且提供了估计整个土层住状液化概率的方法,文中最后通过算例简要讨论了液化概率分析结果的工程应用。     

导热性能对浸油沙层闪点、燃点的影响研究

研究了浸油沙层的导热性能对浸油沙层闪点和燃点的影响。选用柴油作为燃料液体,铜粉和沙子的混合物代表沙层,浸油沙层的导热系数由混合物中的沙子和铜粉比例控制。实验结果表明,浸油沙层的导热性能对其着火特性有重要影响。不加铜粉时,存在一个使混合物的闪点与燃点最小的沙油质量比。随着铜粉添加量的增加,闪点与燃点的最小值点逐渐消失。这可能是加入细铜粉使混合物的表面平整造成的。在最小点后,随铜粉添加量的增加,也就是随混合物的导热性能的改善,混合物的闪点与燃点增大。但当沙子与铜粉的质量比达到1：1时,闪点与燃点随沙油质量比的变化出现了一个最大值,之后闪点和燃点随沙油质量比的增加而降低。这些现象的出现可能是导热能力、毛细现象和混合物内部的空隙三者共同作用的结果。     

沙滤器回洗水薄膜过滤法

介绍了荷兰新近研究成功的适用于处理沙粒过滤器回洗水的XIGA薄膜法,及其参数、工作原理、适用条件和经济效益。     

小型砂滤池在废水处理中的应用

本文通过湿式除尘后的废水治理及工程实例,探讨了小型砂滤池在废水处 理中应用的可行性。