Disinfectant efficacy of chlorite and chlorine dioxide in drinking water biofilms

The drinking water industry is closely examining options to maintain disinfection in distribution systems. In particular this research compared the relative efficiency of the chlorite ion (ClO2-) to chlorine dioxide (ClO2) for biofilm control. Chlorite levels were selected for monitoring since they are typically observed in the distribution system as a by-product whenever chlorine dioxide is applied for primary or secondary disinfection. Previous research has reported the chlorite ion to be effective in mitigating nitrification in distribution systems. Annular reactors (ARs) containing polycarbonate and cast iron coupons were used to simulate water quality conditions in a distribution system. Following a 4 week acclimation period, individual ARs operated in parallel were dosed with high (0.25mg/l) and low (0.1mg/l) chlorite concentrations and with high (0.5 mg/l) and low (0.25mg/l) chlorine dioxide concentrations, as measured in the effluent of the AR. Another set of ARs that contained cast iron and polycarbonate coupons served as controls and did not receive any disinfection. The data presented herein show that the presence of chlorite at low concentration levels was not effective at reducing heterotrophic bacteria. Log reductions of attached heterotrophic bacteria for low and high chlorite ranged between 0.20 and 0.34. Chlorine dioxide had greater log reductions for attached heterotrophic bacteria ranging from 0.52 to 1.36 at the higher dose. The greatest log reduction in suspended heterotrophic bacteria was for high dose of ClO2 on either cast iron or polycarbonate coupons (1.77 and 1.55). These data indicate that it would be necessary to maintain a chlorine dioxide residual concentration in distribution systems for control of microbiological regrowth.     

Evaluation of chlorite and chlorate genotoxicity using plant bioassays and in vitro DNA damage tests

In the last few years chlorine dioxide has been increasingly used for disinfecting drinking water in many countries. Although it does not react with humic substances, chlorine dioxide added to water is reduced primarily to chlorite and chlorate ions, compounds that are under investigation for their potential adverse effects on human health. The aim of this research was to study the genotoxicity of chlorite and chlorate and their mixtures. The end-points included two plant tests (chromosomal aberration test in Allium cepa and micronucleus assay in Tradescantia, carried out at different times of exposure) and two genotoxicity tests in human HepG2 cells (comet assay and cytokinesis-blocked micronucleus test). Preliminary toxicity tests were carried out for both plant and HepG2 assays. The results showed that chlorite and chlorate are able to induce chromosomal damage to plant systems, particularly chromosomal aberrations in A. cepa root tip cells, even at concentrations lower than the limit established by Italian normative law and WHO guidelines. In HepG2 cells increased DNA damage was only observed for chlorate at the lowest concentration. No increase in micronuclei frequency was detected in any of the samples tested in human HepG2 cells.     

Relation of chlorine, copper and sulphur to dioxin emission factors

Dioxin emission factors for different combustion categories range over five orders of magnitude. Both chlorine (Cl(2)) and transition metals, including copper (Cu) have been suggested to promote the formation of dioxin in incinerators, and sulphur (S) has been suggested to inhibit dioxin formation. We show that dioxin (PCDD and PCDF) emission factors from 17 different combustion categories are approximately linearly correlated with the average copper or chlorine content of the combusted material, and inverse linearly correlated with the average sulphur content of the material. Copper and chlorine are correlated and, thus cannot be distinguished. The analysis suggests that the wide range of dioxin emission factors could be explained by the content of sulphur and transition metals or chlorine in combusted materials.     

Entwicklung von Diffusionsschichten auf Nickelbasiswerkstoffen für den Einsatz in chlorhaltigen Hochtemperaturprozessen

Development of diffusion coatings on nickel base alloys for the use in chlorine‐containing high temperature processes To open up the possibility of using sewage sludge ashes as fertilizers the removal of their heavy metal contents is obligatory. A process newly developed at the BAM Berlin executes this separation in highly chlorine‐containing atmospheres at temperatures of up to 1000 °C [1]. Unfortunately there are no materials available which can withstand such conditions over longer periods of time. This project deals with the development of materials that allow the operation in highly corrosive environments. The corrosion resistance of nickel base alloys against chlorine‐induced high‐temperature corrosion will be optimized by application of aluminum‐ and/or silicon‐containing diffusion coatings. As coating method the pack cementation process was selected. In this process, the metal to be coated is embedded in a powder, consisting of the coating metal, a halogen‐distributor (e.g. ammonium chloride) and aluminum oxide as filler material. During an annealing process of several hours at temperatures of 800 to 1000 °C, gaseous metal halides form. They diffuse through the powder pack and decompose at the substrate surface, thereby depositing the coating metal. Subsequent solid phase diffusion results in the formation of a protective diffusion layer. From the thermodynamic point of view, materials with a high content of aluminum and silicon show best prerequisites to build up slow‐growing, stable oxide layers with a high potential to protect the material against corrosive attacks. The actual performance of the materials will be examined in long‐time tests under simulated field conditions (high temperatures and chlorine‐containing atmospheres).     

10万吨／年F2型离子膜法烧碱装置

阐述了本套引进装置Ｆ２型单极式离子膜电解槽等设备的结构特点与优点。展示了隔膜法相对于离子膜法以及Ｆ２型电解槽相对于Ｆ１型电解槽的优越性。本装置不仅可产出高纯烧碱,还可向３０万吨／年氧氯化法生产氯乙烯装置提供配套的优质氯气。     

二氧化氯在油田增产增注中的应用

本文介绍了二氧化氯的基本性质及工业生产原理,ＭｃＣａｆｆｅｒｔｙ 的岩心解堵实验,用二氧化氯解除油井铁硫化物堵塞、注水井微生物堵塞及注聚合物井堵塞的现场结果。     

Non‐asbestos Diaphragms in Chlor‐Alkali Electrolysis

For decades in diaphragm electrolysis, asbestos containing diaphragms have been utilized to separate the anode and cathode compartments. Due to the harmful characteristics of asbestos, its world‐wide prohibition in diaphragm manufacturing is expected. The objective of this work was focussed on the development of a diaphragm with sufficient mechanical and chemical stability to substitute the modified asbestos diaphragm currently used. Suitable materials for the manufacture of non‐asbestos diaphragms were identified and a deposition technology was developed which fulfils the requirements of industrial production plants.     

A study on the Fe–Cl thermochemical water splitting cycle for hydrogen production

Thermochemical water splitting cycles are recognized as one of the promising pathways for sustainable hydrogen production. In the present study, Iron-chlorine (Fe–Cl) cycle as one of the chlorine family thermochemical cycles where iron chloride is consumed for hydrogen production from water, is considered for a study. This four-step cycle is modelled by Aspen Plus software package and analyzed for performance investigation of each reaction step and system's components. The parametric studies are also performed to assess the effect of operation conditions such as temperature, pressure and steam to feed ratio on the reaction products and conversion rates. Results indicated that although the effect of pressure is not significant on reaction's production rates, an increase in temperature favors oxygen production in reverse deacon reaction and magnetite production in hydrolysis and lowers hydrogen production in the hydrolysis step. On the other hand, steam to chlorine (Cl₂) ratio is directly correlated with hydrochloric acid (HCl) and oxygen production in reverse deacon reaction and hydrogen production in hydrolysis.     

Chloride contamination effects on proton exchange membrane fuel cell performance and durability

Chlorine is a major fuel contaminant when by-product hydrogen from the chlor-alkali industry is used as the fuel for proton exchange membrane (PEM) fuel cells. Understanding the effects of chlorine contamination on fuel cell performance and durability is essential to address fuel cell applications for the automotive and stationary markets. This paper reports our findings of chloride contamination effects on PEM fuel cell performance and durability, as our first step in understanding the effects of chlorine contamination.Fuel cell contamination tests were conducted by injecting ppm levels of contaminant into the fuel cell from either the fuel stream or the air stream. In situ and ex situ diagnosis were performed to investigate the contamination mechanisms. The results show that cell voltage during chloride contamination is characterized by an initial sudden drop followed by a plateau, regardless of which side the contaminant is introduced into the fuel cell. The drop in cell performance is predominantly due to increased cathode charge transfer resistance as a result of electrochemical catalyst surface area (ECSA) loss attributable to the blocking of active sites by Cl⁻ and enhanced Pt dissolution.     

利用Excel对离子色谱法测定氯离子进行不确定度评定

目的求离子色谱法测定水样中氯离子含量的不确定度。方法根据国家质量技术监督局发布的国家计量技术规范《测量不确定度的评定与表示,按生活饮用水标准检验方法“进行操作,分析了离子色谱法测定生活饮用水中氯离子的测量不确定度,阐述测定过程中各不确定度分量的来源、各不确定度分量的定量方法以及最终的合成与表示。并利用Excel软件中的函数功能对不确定度进行计算。结果当水样中氯离子含量为88．3mg／L时其相对标准不确定度为1．2％,扩展不确定度为1．1mg／L。结论提出的方法可适用于离子色谱法测定水样中氯离子含量的不确定度评定。