Elimination of COD, microorganisms and pharmaceuticals from sewage by trickling through sandy soil below leaking sewers

To simulate the filtration and/or degradation of trickling sewage from leaky sewers through the non-water-saturated underground, sewage was trickled through sand of 0.4-2mm from the Rhine valley in glass columns of 125 cm length. For the same sewage the chemical oxygen demand (COD) removal was almost independent of low or high trickling rates. The COD removal efficiency varied, however, from 67% to 79%, for sewage from rain and dry weather periods, respectively. The water content of the moist sand increased from initially 80 ml kg(-1) with increasing sewage trickling rates to 108 ml kg(-1) sand. It remained at 108 ml kg(-1) at higher trickling rates higher than 600 ml d(-1). Analyses of effluent of five consecutive 25-cm soil columns revealed that about 50% of the initial COD were filtrated off on top of the sand or degraded in the uppermost 25 cm at varying trickling rates. Another 6-12% of the COD were removed in the following 25-50 cm of sand, whereas almost no further COD removal was seen in the subsequent two or three 25-cm columns. The COD elimination during trickling of sewage through the segmented column (interrupted random flow) was slightly better than that in the non-segmented column. Total and faecal coliform bacteria decreased faster with increasing trickling depth than that of total aerobic or anaerobic bacteria. After a filter/degradation stretch of 125 cm elimination of all bacteria reached 96.2-99.9%. The sewage contained low concentrations of at least 10 different pharmaceuticals or X-ray media. During trickling of sewage through sand, elimination of these compounds by adsorption onto sand and/or biodegradation varied from a complete removal, e.g. Ibuprofen or Naproxen, to almost no removal for several X-ray contrast media. Some of the medicals were removed as effectively as during conventional sewage treatment.     

推进剂剩余量的均匀设计建模

本文主要运用均匀设计［１］的均匀分散布点方法，设计了模拟推进剂剩余量的试验方案，建立了推进剂剩余量的线性模型，并与传统的模拟打靶试验相比较，取得良好效果。均匀设计的最大优点是，以很少的试验次数，获取一般规律性的东西，这对战略导弹的研制、试验、评定具有很好的使用价值。     

电液比例流量压力联合控制的恒功率变量泵的理论分析

本文通过对一种新结构的恒功率变量泵的理论分析,探讨了结构参数和工况参数对控制系统特性的影响。     

城市住区的生态规划设计研究

城市生态住区是住区建设可持续发展的战略要求。城市住区要实现生态化,要从合理的区位、城市交通环境的良好连接、生态化的住区景观环境设计等方面来进行规划和建设。     

交通高峰时段“人车互等-公交车进站停靠低效问题”的调查研究——以西安市钟楼公交车停靠站为例

针对大城市中心城区交通高峰时段公交车排队进站停靠过程中存在人车相互等待、双向耗时的普遍现象,以西安市钟楼公交车停靠站为调研对象,通过实地调查,对其影响因素进行梳理解析,从系统整合层面,实用可行视角,提出疏散整合现有公交线路站点,实施划分停靠站组、改进站台设计、创新完善公交车进站停靠模式等构想和措施,以期促进问题的解决。     

荷载效应组合时的失效概率

本文讨论了构件在荷载效应组合时的失效概率计算问题,荷载的组合采用the Ferry Borges——Castanheta荷载模型及Turkstra规则,用Rackwitz Fiessler的概率积分方法(单称F-R法),计算安全指标β,求得失效概率;以数值例子说明上述分析的有效性.     

MWCNTs as Conductive Network for Monodispersed Fe3O4 Nanoparticles to Enhance the Wave Absorption Performances

Magnetic oxides are widely used as electromagnetic (EM) wave absorbers. To promote the absorption efficiency, tremendous efforts have been contributed to adjusting the composite, structure, and size of magnetic loss materials. Employing carbon materials (CNTs, CF, graphene, PANI) is an efficient way to improve the dielectric loss of the matrix. Anchoring the tiny‐monodispersed Fe₃O₄ nanoparticles (NPs) onto the lightweight multi ? walled carbon nanotubes (MWCNTs) leads to improve dielectric loss and impedance matching characteristic. Magnetic Fe₃O₄ NPs along the one‐dimensional nanotubes direction play a good synergetic role with MWCNTs due to the interfacial strong chemical and structure bonding. The as‐synthesized Fe₃O₄/MWCNTs nanocomposites exhibit efficient EM wave absorption characteristics (R_L av?10 dB) with a maximum reflection loss of ?63.64 dB at 12.08 GHz and a diminutive thickness of only 1.6 mm. The magnetic Fe₃O₄ NPs show strong chemical and structure bonding with the one‐dimensional MWCNTs. This work may show a way to broaden the application of such kinds of lightweight high‐performance absorbing materials frameworks.

     

Post combustion CO2 capture by carbon fibre monolithic adsorbents

As generation of carbon dioxide (CO₂) greenhouse gas is inherent in the combustion of fossil fuels, effective capture of CO₂ from industrial and commercial operations is viewed as an important strategy which has the potential to achieve a significant reduction in atmospheric CO₂ levels. At present, there are three basic capture methods, i.e. post combustion capture, pre-combustion capture and oxy-fuel combustion. In pre-combustion, the fossil fuel is reacted with air or oxygen and is partially oxidized to form CO and H₂. Then it is reacted with steam to produce a mixture of CO₂ and more H₂. The H₂ can be used as fuel and the carbon dioxide is removed before combustion takes place. Oxy-combustion is when oxygen is used for combustion instead of air, which results in a flue gas that consists mainly of pure CO₂ and is potentially suitable for storage. In post combustion capture, CO₂ is captured from the flue gas obtained after the combustion of fossil fuel. The post combustion capture (PCC) method eliminates the need for substantial modifications to existing combustion processes and facilities; hence, it provides a means for near-term CO₂ capture for new and existing stationary fossil fuel-fired power plants.This paper briefly reviews CO₂ capture methods, classifies existing and emerging post combustion CO₂ capture technologies and compares their features. The paper goes on to investigate relevant studies on carbon fibre composite adsorbents for CO₂ capture, and discusses fabrication parameters of the adsorbents and their CO₂ adsorption performance in detail. The paper then addresses possible future system configurations of this process for commercial applications.Finally, while there are many inherent attractive features of flow-through channelled carbon fibre monolithic adsorbents with very high CO₂ adsorption capabilities, further work is required for them to be fully evaluated for their potential for large scale CO₂ capture from fossil fuel-fired power stations.