Wastewater treatment by radial freezing with stirring effects

Radial freezing experiments on wastewater models were conducted in the presence of imposed stirring in order to remove impurities. The studied samples (dilute Na-montmorillonite suspensions charged with nitrates and with zinc or lead) were placed inside a cylindrical annulus, cooled at a controlled temperature around -7 degrees C at its inner wall which rotated around a vertical axis. The freezing front propagated toward the still outer wall which was maintained at a constant temperature around +1 degrees C. Thanks to stirring, considerable purification rates up to 99.97% were attained. It was also demonstrated that combining radial freezing and stirring ended in residual concentrations which agreed with drinking water standards.     

Environmental Implications of Treatment of Coastal Sewage Discharges

The environmental implications of implementing the requirement for treatment of coastal sewage prior to discharge, which were put forward in an EC draft Directive on municipal waste-water treatment, are examined. In order to establish the current situation, the results of a national survey of coastal and estuarine sewage discharges are presented. A review of the impact of sewage discharges on the marine environment is presented in conjunction with an assessment of the impact of sewage-treatment processes on the land and in the air. These aspects are integrated into overall conclusions about net environmental impact. Finally, a decision-tree approach to the assignment of priority to additional action required at individual locations is developed.     

Enhanced adsorption of Cd (II) on a hydrous Al (III) floc in the presence of a modified form of polyethylenimine

A polymer modified with succinic anhydride has been investigated for the adsorption of cadmium (II) on a freshly precipitated aluminium (III) hydroxide floc. The proportion of chelate attached to the polymer is varied to determine the relationship between carboxyl and amino groups on the polyelectrolyte, in terms of enhanced adsorption of cadmium (II) on a hydrous aluminium floc. The presence of polyelectrolyte enhanced the adsorption of 3.3 ppm Cd (II) on a 333 ppm Al (III) floc at every concentration of polyelectrolyte investigated. The proportion of succinic anhydride attached to the polymer had an impact on the increased adsorption of Cd (II) on an Al (III) floc observed. A decreasing proportion of succinic anhydride to polymer resulted in a decrease in the amount of cadmium adsorbed on the floc. Above pH 8, a decrease in the % Cd (II) adsorbed on the floc and % Al (III) retained within the floc decreases with the presence of polyelectrolyte as a result of the formation of soluble Cd-Polyethylenimine-succinic acid (PEISA) complexes. When the Al-PEISA combination was applied to a complex matrix where Cd (II), Cu (II) and Ni (II) ions competed for adsorption, enhanced adsorption was observed for Cd (II) and Ni (II). At pH 7, dissolution of the floc observed with the addition of discrete chelates was not observed with the addition of polyelectrolytes.     

项目中的冲突管理

讨论了项目管理中常见的冲突问题,分析了冲突产生的原因,阐述了缓和、退让、折衷、强制等处理冲突的几种明确办法,并提出了涉及两方冲突的典型管理策略,以保证项目管理的顺利进行。     

夹层土中砼预制桩基事故分析及处理

对夹层上中砼预制桩基发生持力层冲剪破坏事故进行分析,并对事故的处理及其工程设计谈了几点体会,可供参考.     

曝气生物滤池设计与施工的若干问题

曝气生物滤池是一种新型的水处理工艺,兼具生物膜法和活性污泥法的许多优点。结合工程实践,从主要参数、池型选择、滤板滤梁、滤头与开孔率、承托层、空气压缩系统、滤头防堵、土建质量、空气管道吹扫以及调试等方面讨论了污水处理上向流曝气生物滤池(UBAF)设计与施工过程应注意的问题。     

喷汽式电熨斗火灾痕迹物证鉴定技术的研究

以一起火灾案例为线索，阐述了喷汽式电熨斗的工作原理和结构特点，分析和总结了喷汽式电熨斗残骸所呈现的痕迹特征，并通过金相分析方法和热分析方法对电熨斗的金属底板进行了技术鉴定，确定出各部位的受温程度，以及通过模拟试验的方法进一步验证了该电熨斗火前通电过热引起火灾的结论。     

对污水深度处理滤池工艺设计的探讨

首先介绍和分析了重力式滤池两种流向 (上向流式和下向流式 )的过滤机理 ,并从多方面阐明了污水深度处理宜采用上向流式滤池的观点 .其次 ,对上向流滤池的运行特性进行了分析 ,从而得出冲洗工序对滤后水质有影响的结论 .最后还介绍了上向流滤池的应用实例及其工艺设计参数 .     

Application of GaN-based ultraviolet-C light emitting diodes--UV LEDs--for water disinfection

GaN-based ultraviolet-C (UV-C) light emitting diodes (LEDs) are of great interest for water disinfection. They offer significant advantages compared to conventional mercury lamps due to their compact form factor, low power requirements, high efficiency, non-toxicity, and overall robustness. However, despite the significant progress in the performance of semiconductor based UV LEDs that has been achieved in recent years, these devices still suffer from low emission power and relatively short lifetimes. Even the best UV LEDs exhibit external quantum efficiencies of only 1-2%.The objective of this study was to investigate the suitability of GaN-based UV LEDs for water disinfection. The investigation included the evaluation of the performance characteristics of UV LEDs at different operating conditions as well as the design of a UV LED module in view of the requirements for water treatment applications. Bioanalytical testing was conducted using Bacillus subtilis spores as test organism and UV LED modules with emission wavelengths of 269 nm and 282 nm.The results demonstrate the functionality of the developed UV LED disinfection modules. GaN-based UV LEDs effectively inactivated B. subtilis spores during static and flow-through tests applying varying water qualities. The 269 nm LEDs reached a higher level of inactivation than the 282 nm LEDs for the same applied fluence. The lower inactivation achieved by the 282 nm LEDs was compensated by their higher photon flux. First flow-through tests indicate a linear correlation between inactivation and fluence, demonstrating a well designed flow-through reactor. With improved light output and reduced costs, GaN-based UV LEDs can provide a promising alternative for decentralised and mobile water disinfection systems.