Biological filtration for removal of arsenic from drinking water

The main objective of the study was to find a suitable iron to arsenic ratio in water to reduce arsenic to 5 μg/L or lower through sand filtration. Experiments were conducted by varying the quantity of iron(II) while keeping the arsenic concentration at 100 μg/L. A mixture of iron (II) and arsenic at different ratios (10:1, 20:1, 30:1 and 40:1) was pumped to the sand filters in a down flow mode and effluent arsenic and iron were analyzed. It was found that a ratio of iron to arsenic of 40:1 was necessary to ensure an effluent arsenic concentration of 5 μg/L or lower. Iron in the filtrate was found to be below 0.1 mg/L at all times.     

Green sand reclamation using a fluidized bed with an attrition nozzle

The objective of this study was to determine the technical feasibility of green sand reclamation using attrition in a gas–solid fluidized bed. Reclamation of foundry sand is becoming important as it may help solve concerns related to transportation and dumping of the used sand, and reduce production costs by recycling sand. The crucial step in green sand reclamation is the removal of small clay particles that are bound to the sand particles.For this study two different types of green sand were used and supplied by two different foundries. Tests were performed in a fluidized bed equipped with an attrition nozzle operating at pressures of either 350 or 550 kPa (50 or 80 psig). Attrition experiments for one green sand were performed on either unburned or burned (calcined) green sand, to determine the effect of prior calcination of the green sand on its reclamation potential by attrition. Calcination temperatures of over 700 °C were employed, and the results suggest that calcination facilitates the removal of clay from the green sand.Green sand was analyzed for clay and organic content, acid request, and particle size before and after attrition. Attriting calcined green sand produces the best results. Also experiments conducted at the highest attrition pressure of 550 kPa gave good results. According to the mass balance, the mass lost during the attrition process may be limited to less than 14%, and this could be considered acceptable. The volume of air required for the attrition nozzle is rather high and this may adversely affect the economics of the process.     

利用浑浊度推算含沙量方法的限制性与适用性研究

通过对利用浑浊度与含沙量的相关关系来推算含沙量的方法的研究,发现此方法有两个限制因子,一是泥沙粒径,二是水中盐等其他杂质。研究结果表明,浊度法对于低含沙量、粒径小的水样测量精度高。     

Efficient management of marine resources in conflict: An empirical study of marine sand mining, Korea

This article develops a dynamic model of efficient use of exhaustible marine sand resources in the context of marine mining externalities. The classical Hotelling extraction model is applied to sand mining in Ongjin, Korea and extended to include the estimated marginal external costs that mining imposes on marine fisheries. The socially efficient sand extraction plan is compared with the extraction paths suggested by scientific research. If marginal environmental costs are correctly estimated, the developed efficient extraction plan considering the resource rent may increase the social welfare and reduce the conflicts among the marine sand resource users. The empirical results are interpreted with an emphasis on guidelines for coastal resource management policy.     

干化污泥热解制备可燃气过程中石英砂的影响

污水污泥样品经过105℃干燥处理后,在管式电阻炉和热天平上分别以15℃/min升温速率,在0～950℃温度范围进行污泥混合石英砂的热解实验研究。石英砂污泥混合热解实验发现:混合热解的产气总量得到提高,石英砂的加入不改变污泥热解生成可燃气的规律。在热解的高温段(800～950℃),由于加入了石英砂,CO浓度得到了提高。     

岩土震害影响因子权重研究——以砂土液化为例

以砂土液化影响因子的权重计算为例,探讨了一种兼顾主、客观因素的权重确定方法。首先分别使用层次分析法和粗糙集理论计算砂土液化影响因子的主、客观权重值。然后对所得到的主、客观权重值进行检验,得到各自的预测准确性,根据对其准确性进行比较得到主、客观权重值偏好系数,最终按照偏好系数对主、客观权重值进行计算得到综合权重值。并对所得到的综合权重进行验证,其预测准确率为91.7%,说明该方法具有比较高的准确性。通过研究发现,对主、客观权重通过偏好系数进行综合,可以较好的平衡两者的影响作用,能够提高权重分析的准确性;通过对砂土液化影响因子权重的分析发现地震作用对其影响要大于土体埋藏环境和土体自身性质,在所有影响因子中有效应力的影响最大,其权重达到了0.205。     

改良型慢滤池处理垃圾渗滤液

为了对慢滤池处理垃圾渗滤液工艺的基本参数进行研究,实验采用改良的小试规模的慢滤池模型,处理来自济南生活垃圾卫生填埋场中后期年龄段高浓度的垃圾渗滤液。重点考察活性炭粉末添加层的厚度、细粗滤料配比以及滤料层上部水层的高度等诸多因素对系统去除污染物效果的影响。实验结果表明,在垃圾渗滤液经过预处理进入慢滤池系统之后,此时调节细粗滤料配比例为2,水层高度为30 cm,活性炭粉末添加层厚度为1 cm,使得系统对各种污染的整体去除效果较好。此时,氨氮、总磷、浊度、色度和COD的去除率分别为75%、65%、90%、97%和81%。     

河北省沙尘暴特征及防治对策

根据河北省２０００年春季发生多次扬沙与沙尘暴的事实,分析了本省沙尘暴的时空分布特征及成因,论术字本省土地沙化及沙尘暴的危害程度。提出了防沙尘暴的对策与建议。     

军用装备砂尘环境试验技术

介绍了进行砂尘环境试验的目的、适用范围及环境影响因素,并说明应根据产品使用环境、本身特点及其产品技术条件来选择试验程序和确定各试验参数.同时指出了确定试验持续时间的方法,最后对砂尘试验箱(室)提出6点设计要求,为我国自行研制军用砂尘环境试验设备提供了依据,从而提高了我国军用武器装备对环境的适应性及可靠性.     

Cd2+与环丙沙星共存时在石英砂中的吸附特征及作用机理

为探讨重金属与兽药抗生素共存时在土壤及地下水砂层中的吸附行为及机理,以重金属镉（Cd）和环丙沙星（Ciprfloxacin,CIP）为研究对象,石英砂为介质,通过批平衡实验法,研究不同Cd²⁺浓度、pH及离子强度等因素下Cd²⁺与环丙沙星共存时在石英砂上的吸附行为及其交互影响.结果表明：①环丙沙星在石英砂上的吸附可分为两个阶段,6 h内为快速吸附,6~24 h为慢速吸附,24 h后达到吸附平衡;Cd²⁺在石英砂上的吸附表现为瞬时吸附,且吸附行为不受环丙沙星浓度的影响;环丙沙星在石英砂上的吸附动力学过程用伪二级动力学模型拟合效果最优,其次是伪一级动力学方程,颗粒内扩散方程拟合效果最差.②不同Cd²⁺浓度对环丙沙星吸附的影响不同,当Cd²⁺浓度较低（5、20 mg·L^-1）时,Cd²⁺的存在对吸附起促进作用;当Cd²⁺浓度为100 mg·L^-1时,Cd²⁺的存在对吸附起抑制作用;pH越高,离子强度越大,石英砂对环丙沙星的吸附量越低,而石英砂对Cd²⁺的吸附则表现为pH越高,吸附量越大,离子强度越高,吸附量越小;不同Cd²⁺浓度、pH及离子强度对CIP吸附的影响程度与CIP浓度有关,CIP浓度越低,影响越显著;除了pH为7的条件外,CIP对Cd²⁺在石英砂上的吸附基本没有影响.③Freundlich方程能较好地拟合不同条件下CIP在石英砂中的吸附曲线,R²均大于0.949,且大部分n值在0.326~0.651之间,说明石英砂对CIP的吸附是非线性的.④Cd可与CIP中的羧基（—COOH）和羰基（C=O）发生络合作用形成络合物而被石英砂所吸附.