共查询到20条相似文献,搜索用时 15 毫秒
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To the best of our knowledge, this study is the first investigation to be performed into the potential benefits of mechanically mixed disinfectants in controlling bacterial inactivation. The purpose of this study was to evaluate the disinfection efficiency of mechanically mixed oxidants with identical oxidant concentrations, which were made by adding small amounts of subsidiary oxidants, namely ozone (O3), chlorine dioxide (ClO2), hydrogen peroxide (H2O2) and chlorite (ClO2(-)), to free available chlorine (Cl2), using Bacillus subtilis spores as the indicator microorganisms. The mechanically mixed oxidants containing Cl2/O3, Cl2/ClO2 and Cl2/ClO2(-) showed enhanced efficiencies (of up to 52%) in comparison with Cl2 alone, whereas no significant difference was observed between the mixed oxidant, Cl2/H2O2, and Cl2 alone. This enhanced disinfection efficiency can be explained by the synergistic effect of the mixed oxidant itself and the effect of intermediates such as ClO2(-)/ClO2, which are generated from the reaction between an excess of Cl2 and a small amount of O3/ClO2(-). Overall, this study suggests that mechanically mixed oxidants incorporating excess chlorine can constitute a new and moderately efficient method of disinfection. 相似文献
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通过试验研究了不同水质因素对二氧化氯消毒的影响,着重考虑好氧量(CODMn)的作用,研究结果表明,CODMn值的变化对二氧化氯消毒有较大影响,二氧化氯对CODMn的去除率随着CODMn的减少而减小,当CODMn<4 mg/L时,几乎没有去除效果。 相似文献
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Chlorine disinfection experiments were conducted to investigate the die-off patterns of the fecal coliforms when present in waste stabilization pond effluents containing from 100 to 400 mg l−1 algae. The fecal coliform inactivation was observed to occur at two rates, i.e. an initial rapid kill followed by a slower kill. The magnitude of inactivation was found to be proportional to the initial chlorine dose and contact time and inversely proportional to the algal concentration. A mathematical model was developed to predict the fecal coliform survival ratio during the chlorination of the pond effluent. When compared with the experimental data, the predicted results had a correlation coefficient of 0.981. 相似文献
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In an effort to validate previous research suggesting remarkable resistance of norovirus to free chlorine disinfection, we characterized the disinfection response of purified and dispersed Norwalk virus (NV) by bench-scale free chlorine disinfection using RT-PCR for virus assays. The inactivation of NV by two doses of free chlorine (1 and 5 mg/L) at pH 6 and 5 °C based on two RT-PCR assays was similar to that of coliphage MS2, but much faster than that of poliovirus 1. Despite the underestimation of virus inactivation by RT-PCR assays, the predicted CT values for NV based on RT-PCR assays are lower than the ones for most other important waterborne viruses and the CT guidelines for chlorine disinfection of viruses under the Surface Water Treatment Rule by the United States Environmental Protection Agency. Overall, the results of this study indicate that NV is not highly resistant to free chlorine disinfection as suggested by previous research and it is likely that NV contamination of drinking water can be controlled by adequate free chlorine disinfection practices with provision of proper pre-treatment processes before chlorination. 相似文献
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Effect of cavitation on chemical disinfection efficiency 总被引:7,自引:0,他引:7
This study brings out the potential efficacy of hybrid techniques for water disinfection. The techniques studied include hydrodynamic cavitation, acoustic cavitation and treatment with chemicals like hydrogen peroxide and ozone. The hybrid techniques which combine hydrodynamic cavitation, acoustic cavitation and hydrogen peroxide appear to be an attractive alternative to any one technique on its own for the reduction in the heterotropic plate count bacteria as well as indicator microorganisms like the total coliforms, fecal coliforms and fecal streptococci. 相似文献
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To elucidate the mechanism of disinfection by chlorine, its effects on some vital properties associated with cell membrane of Escherchia coli were studied. There was no significant change in Zeta potential at bactericidal doses of chlorine. Treatment with chlorine induced the leakage of macromolecules from the cells indicating the permeability changes of the membrane. Proteins and RNA were detected in the supernatant when the cells were treated with chlorine dose of 1.5 mg 1−1 (100 μg Cl mg−1 N). The presence of DNA was observed only at high chlorine doses. The studies on oxidative phosphorylation of cell free extract indicated the complete cessation of phosphate uptake at a dose of 0.4 mg 1−1 (30 μg Cl mg−1 N). There was about 70% decrease in the oxygen uptake corresponding to chlorine dose of 0.8 mg 1−1. 相似文献
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Comparison of disinfection byproduct formation from chlorine and alternative disinfectants 总被引:4,自引:0,他引:4
Seven diverse natural waters were collected and treated in the laboratory under five oxidation scenarios (chlorine, chloramine, both with and without preozonation, and chlorine dioxide). The impact of these disinfectants on the formation of disinfection byproducts was investigated. Results showed that preozonation decreased the formation of trihalomethanes (THMs), haloacetic acids (HAAs) and total organic halogen (TOX) for most waters during postchlorination. A net increase in THMs, HAAs and TOX was observed for a water of low humic content. Either decreases or increases were observed in dihaloacetic acids and unknown TOX (UTOX) as a result of preozonation when used with chloramination. Chloramines and chlorine dioxide produced a higher percentage of UTOX than free chlorine. They also formed more iodoform and total organic iodine (TOI) than free chlorine in the presence of iodide. Free chlorine produced a much higher level of total organic chlorine (TOCl) and bromine (TOBr) than chloramines and chlorine dioxide in the presence of bromide. 相似文献
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Modeling can play a particularly useful role in ultraviolet (u.v.) disinfection because of difficulties in measuring u.v. dose and the immediate results of disinfection. This model predicts bacterial survival in flow-through systems. The calculation takes into account the complex intensity patterns, non-ideal flow patterns, and non-linear curves of log survival vs u.v. dose. Based on the organismal dose-response, the number of survivors in each fraction of the residence time distribution is calculated separately and summed to calculate the average survival. The model uses as input data: the average u.v. intensity within the system, the residence time distribution, and an experimentally determined dose-survival curve in a simplified system where dose can be directly measured. The predictions of the model corresponded well with measured survival in a u.v. pilot plant study. The model was used to show the effects of flow dispersion on average survival by varying residence time distribution. Measures of capacity and efficiency of u.v. systems were derived and illustrated experimentally in simple cylindrical batch units and in two multiple lamp units. 相似文献
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Chlorine dioxide when used as an effective disinfectant forms undesirable disinfection by-products, i.e. chlorite and chlorate ions. The aim of this research was to study the removal of these ions by ferrous ions in the presence or absence of oxygen. The efficiency of Fe+2 for ClO2- and ClO3- removal was followed by a determination of their initial and final concentrations, pH and delta Fe+2 consumed/delta ClO2- removed ratios. The optimal weight ratio of delta Fe+2 consumed/delta ClO2- removed for complete ClO2 removal was found to be close to the theoretical calculated value of 3.31. It was proved that ferrous salts can reduce chlorite ions to harmless Cl- ions. This method can be recommended as a part of ClO2 disinfection to ensure safe drinking water, with no harm to water consumers and to the environment. 相似文献
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The effect of boiling water on disinfection by-product exposure 总被引:1,自引:0,他引:1
Chloraminated and chlorinated waters containing bromide were used to determine the impact of boiling on disinfection by-product (DBP) concentrations. No significant changes were detected in the concentrations of the dihalogenated haloacetic acids (DXAAs) (i.e., dichloro-, bromochloro-, dibromoacetic acid) upon boiling of chloraminated water, whereas the levels of the trihalogenated haloacetic acids (TXAAs) (i.e., trichloro- (TCAA), bromodichloro- (BDCAA), dibromochloroacetic acid (DBCAA)) decreased over time (e.g., 9-37% for TCAA). Increased DXAA concentrations (58-68%) were detected in the boiled chlorinated sample, which likely resulted from residual chlorine reacting with DXAA precursors. TCAA concentration was unchanged after boiling chlorinated water for 1 min, but a 30% reduction was observed after 5 min of boiling. BDCAA concentrations decreased 57% upon boiling for 1 min and were completely removed after 2 min of boiling, whereas DBCAA was removed after boiling chlorinated water for 1 min. Trihalomethane concentrations were reduced in both chloraminated (74-98%) and chlorinated (64-98%) water upon boiling. Boiling chloraminated water for 1 min reduced chloroform concentration by 75%. Chloroform was reduced by only 34% in chlorinated water after a 1 min boil, which indicates that simultaneous formation and volatilization of chloroform was occurring. Most of the remaining DBPs (e.g. haloketones, chloral hydrate, haloacetonitriles) were removed by at least 90% after 1 min of boiling in both samples. These data suggest that other mechanisms (e.g., hydrolysis) may have been responsible for removal of the non-volatile DBPs and further highlight the importance of examining individual species when estimating thermal effects on DBP concentrations. 相似文献
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Trihalomethanes formation in point of use surface water disinfection with chlorine or chlorine dioxide tablets 下载免费PDF全文
David Werner Maria Valdivia‐Garcia Paul Weir Mark Haffey 《Water and Environment Journal》2016,30(3-4):271-277
In remote or underdeveloped areas, natural disaster emergencies and armed conflict zones, point‐of‐use surface water disinfection with chlorine tablets provides microbiologically safe water, but disinfection by‐products such as trihalomethanes (THMs) are formed. While the health risks from THMs are much less than the risks from consuming microbiologically unsafe water, it is nonetheless desirable to understand and minimise THM formation. We show that THM concentrations in surface water samples from the Northern British Isles disinfected with chlorine tablets increased with contact time, in some cases to significantly exceed EU, US EPA and WHO drinking water guidance values after more than an hour. More stagnant water from ponds and lochs had higher THM formation than river water. Doubling the chlorine tablet dose slightly enhanced THM formation, and passing water through coffee filter paper reduced it. Chlorine dioxide tablets produced minimal amounts of THMs. 相似文献
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C. N. Haas B. F. Severin D. Roy R. S. Engelbrecht A. Lalchandani S. Farooq 《Water research》1985,19(3):323-329
This paper summarizes studies on the presence of acid-fast and yeast organisms in wastewater and water treatment plants and in surface water. These organisms were found to satisfy three of Bonde's criteria for indicator organisms: presence whenever pathogens are likely to be present; resistance at least equal to that of pathogens; and lack of regrowth in the post-treatment environment. This, plus prior data, indicates that these organisms are at least as acceptable as indicators of disinfection efficiency than the coliform group. 相似文献
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概述了ClO_2消毒技术的特点及消毒副产物对人体健康存在的隐患,介绍了离子色谱仪测饮用水中消毒副产物的检测方法和检测条件,并对某水厂近半年的出厂水中的ClO_2消毒副产物进行检测,结果表明该水厂的出厂水中的消毒副产物符合卫生标准。 相似文献
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Ozone and chlorine dioxide present definite advantages and disadvantages over chlorination. Chlroination, particularly for the removal of ammonia and the maintenance of a disinfectant residual in the distribution system has decisive advantages and will be difficult to replace. Ozone and chlorine dioxide seem to produce fewer carcinogenic by-products but the risk fur acute toxicity, especially from the chlorites which follow chlorine dioxide, is higher than with chlorine.Chlorine dioxide and more particularly ozone should be considered as usefulcomplements to chlorination, but no strong oxidative treatment should be applied before most of the organic matter has-been removed. 相似文献