Studies in Radiation Chemistry: Application to Ozonation and Other Advanced Oxidation Processes

Advanced oxidation/reduction processes (AORPs) are an alternative water treatment that is becoming more widely utilized. Our radiation-chemistry based studies are being used to develop a fundamental understanding of AOP treatment options, and are divided into three complementary types of contaminants; disinfection by-products (DBPs), emerging pollutants of concern (EPoCs), and natural organic matter (NOM). More than 600 DBPs have been identified, and one class that appears to have severe potential adverse health effects is the halonitromethanes (HNMs). Of the nine HNMs, trichloronitromethane (chloropicrin) is the most common, with levels up to 180 nM in US drinking waters. EPoCs are of interest because of their biological activity at low concentrations in water and while the initial focus was on endocrine disruptor chemicals (EDCs) this class has now been expanded to include many other recalcitrant chemicals such as hormones, antibiotics, industrial contaminants, and health care products. Natural organic matter is one of the most common radical scavengers in natural waters and therefore may adversely affect AOPs. Our approach is to study NOM both directly and using model compounds thought to be representative of structural components of this complex material.     

Thermal inactivation of water-borne pathogenic and indicator bacteria at sub-boiling temperatures

The use of harvested rainwater in domestic hot water systems can result in optimised environmental and economic benefits to urban water cycle management, however, the water quality and health risks of such a scenario have not been adequately investigated. Thermal inactivation analyses were carried out on eight species of non-spore-forming bacteria in a water medium at temperatures relevant to domestic hot water systems (55-65 degrees C), and susceptibilities to heat stress were compared using D-values. The D-value was defined as the time required to reduce a bacterial population by 90% or 1 log reduction. The results found that both tested strains of Enterococcus faecalis were the most heat resistant of the bacteria studied, followed by the pathogens Shigella sonnei biotype A and Escherichia coli O157:H7, and the non-pathogenic E. coli O3:H6. Pseudomonas aeruginosa was found to be less resistant to heat, while Salmonella typhimurium, Serratia marcescens, Klebsiella pneumoniae and Aeromonas hydrophila displayed minimal heat resistance capacities. At 65 degrees C, little thermal resistance was demonstrated by any species, with log reductions in concentration occurring within seconds. The results of this study suggested that the temperature range from 55 to 65 degrees C was critical for effective elimination of enteric/pathogenic bacterial components and supported the thesis that hot water systems should operate at a minimum of 60 degrees C.     

范式沉浮——百年来西方城市规划理论体系的建构

本文在总结前人研究的基础上,从范式的角度对近百年来西方城市规划的思想演变进行了归纳和总结,认为:(1)当代西方的规划思想深深根植于“现代性”的启蒙传统中,理性始终是西方规划理论演变背后的“内核”和“原动力”;(2)近百年来西方规划理论范式围绕“理性”大体经历了四次重大的转变,笔者分别将其命名为“经验理性范式”、“工具理性范式”、“价值理性范式”和“沟通理性范式”;(3)规划理论范式的演变是革命性与连续性、稳定性与“创造性破坏”的辩证统一.规划具有深刻的时代背景和思想基础,也具有多种创新的可能性;具有跨越性质变,也有渐进性的“连结谱”和跨期的思想“再现”.最后笔者试图基于上述结论对西方未来的城市规划理论发展方向加以展望,并对中国目前的城市规划理论发展提出了一点看法.     

图底城市

随着对新柏林所缺失的城市记忆的热烈讨论，柏林中心城区地图成为众多柏林相关出版物中的类。1945,1953，1980，2000和2010年的图底平面图将柏林中心城区的命运清晰地展示在大众眼前，它们不仅记录了柏林城市在二战后各种破坏与重建的情况，从中还可以读出在各个历史阶段影响柏林城市建设与发展的种种事件与力量。     

Use Of Static Mixer For Oxidation And Disinfection By Ozone

Ozone is used in drinking water treatment as a biocide, as an oxidant and as a pretreatment in order to improve the performance of subsequent processes. Increasing concern over the quality of drinking water has led to a number of new stringent regulations in the control of chemical and microbiological contaminants. Disinfection deals with the concept of “CT”, which is the need to maintain a certain minimum concentration for a given time. Under ideal laboratory conditions, it is 0.4 mg O₃/L for 4 min. In practice, since the method for the CT determination has not been finalized by the EPA, “T” can be the minimum detention time of 90% of total flow, and “C” can be a measured ozone residual at the outlet of cells of the contactor. New standards for micropollutants in drinking water imply an optimization of the ozonation step, by improving the ozone transfer from gas to water, and the control of the detention time as well as ozone residual within the contactor.

All these considerations have led us to use static mixers to transfer ozone into water. This process enables us to control the ozone concentration in water and detention time. It is a very simple system, with very low maintenance requirements due to the lack of moving parts. Civil engineering is minimized. A pilot scale study is presented here. It took place at the Méry-sur-Oise water treatment plant, on a pilot plant working at 8-12 m³/h. It is composed of a static mixer for the transfer of ozone from gas to liquid, linked to an air lift to separate gas from liquid, providing ozonated water.

The optimization of transfer was achieved by studying the impact of water flow, gas flow and ozone concentration in the gas. It is possible to reach 90% of transfer in less than 15 s. Headloss (ΔP) across the mixer is a function of gas and water flows and remains economically very acceptable as 0.15 bar for 12 m³/h.

Atrazine removal was studied using a static mixer, an air lift and a contact pipe 80-m long, providing an optimum contact time phase, working as a plug flow reactor. Ozone and H₂O₂/O₃ treatments were compared. The maximum reduction of atrazine concentrations (e.g., for an infinite contact time) is a function of the amount of transferred ozone, but H₂O₂ influences the kinetics of the reaction. In the presence of H₂O₂ with a ratio of H₂O₂ to O₃ of 0.4 w/w, maximum elimination is reached in 2 min 30 s.

The effect of such treatments on environmental bacteria also was followed. A counting of total germs at 20°C showed a decrease of 1- to 3-logs 10 after 1 min 30 s of contact time for about 2 mg/L of transferred ozone. No significant difference between treatments with or without H₂O₂ was shown. The same conclusions were obtained from heterotrophic plate counts (37°C) and epifluorescence countings.     

马兰庄铁矿开采最终边坡角稳定性分析

在马兰庄铁矿工程地质调查的基础上,完成了矿山边坡工程地质岩组的划分及各岩组的工程地质性质的调查,并借助岩石力学性质试验分析、楔型体等传统方法、极限平衡分析法优化确定马兰庄铁矿露天境界最终边坡角,力求能够准确合理的评价边坡稳定情况.分析结果表明马兰庄铁矿白马山和沙河山两采场最终边坡角都有提高的潜力.     

Compaction of Fullerite Films after High Fluence Ion and Electron Bombardment

Thin fullerite layers are irradiated with 0.1 to 16 MeV electrons and 250 to 500 keV light ions at high fluence, and GeV heavy ions at low fluence. The subsequent analysis by Rutherford backscattering spectrometry revealed that in all cases the energy loss of the analyzing particles in the irradiated samples is enhanced, in comparison to the corresponding pristine samples. This is interpreted as resulting from a compactation of the fullerite films, and indicates an irradiation-induced phase transition towards amorphous, or even diamond-like carbon.     

Lithium Implantation into Fullerite

The depth profiles of lithium, implanted into fullerene at different fluences and temperatures are reported. They deviate considerably from the simple ballistic predictions. They can be understood in terms of depth dependent Li mobility immediately after the ion implantation. This mobility depends considerably on the temperature and on the degree of fullerene damage. It appears that the fullerene destruction products which act as traps for the mobile lithium are somewhat mobile themselves, essentially at high temperatures, and at low damage levels.     

露天矿边坡局部破坏形式分类及破坏机理分析

针对露天矿开采过程中高陡边坡破坏形式的分类及损伤机理进行研究。以金川集团露天石英矿边坡监测预警项目为研究背景,运用Matlab软件对位移监测数据进行分析,将边坡的位移场与边坡的破坏形态相结合,对边坡破坏形态进行分类,可分为下滑式、张拉式、侵蚀式、复合式。其中下滑式、侵蚀式破坏发展迅速、破坏程度大,张拉式破坏发展缓慢、破坏程度小。又进一步研究了边坡各破坏形式发生的内部机理,并针对边坡的破坏形式提出了具体的加固措施。     

大型露天矿山边坡岩体结构与破坏模式分析

以水厂铁矿矿区地质环境、构造、地层、岩性与水文地质条件为基础，进行了边坡岩体工程地质岩组的划分与边坡岩体的结构分析。根据岩体的结构特征、结构面的产状与采场边坡方位的空间组合关系，确定了边坡岩体的结构类型和边坡潜在的破坏模式，为边坡工程的稳定性分析与治理提供了必要的依据。