溴酸根在紫外和氯消毒联用工艺中的形成

以H2O-Br--Cl2/NH2Cl/ClO2为研究对象,考查UV作用下BrO3-产生的情况。结果表明：原水和去离子水背景下,Cl2/UVC联用可以氧化部分的Br-生成BrO3-;NH3可以有效的抑制BrO3-生成,并且NH2Cl/UVC作用时不生成BrO3-;ClO2/UV体系产生溴酸根能力明显弱于Cl2/UV;ClO2/UVC产生BrO3-的量高于ClO2/UVA。酸性条件同时促进BrO3-的产生和ClO2的分解,碱性条件正好相反。     

Formation of organic chloramines during water disinfection - chlorination versus chloramination

Many of the available studies on formation of organic chloramines during chlorination or chloramination have involved model organic nitrogen compounds (e.g., amino acids), but not naturally occurring organic nitrogen in water. This study assessed organic chloramine formation during chlorination and chloramination of 16 natural organic matter (NOM) solutions and 16 surface waters which contained dissolved organic nitrogen (DON). Chlorination rapidly formed organic chloramines within 10 min, whereas chloramination formed organic chloramination much more slowly, reaching the maximum concentration between 2 and 120 h after the addition of monochloramine into the solutions containing DON. The average organic chloramine formation upon addition of free chlorine and monochloramine into the NOM solutions were 0.78 mg-Cl₂/mg-DON at 10 min and 0.16 mg-Cl₂/mg-DON at 24 h, respectively. Organic chloramine formation upon chlorination and chloramination increased as the dissolved organic carbon/dissolved organic nitrogen (DOC/DON) ratio decreased (i.e., DON contents increased). Chlorination of molecular weight (10,000 Da) fractionated water showed that molecular weight of DON would not impact the amount of organic chloramines produced. Comparison of three different disinfection schemes at water treatment plants (free chlorine, preformed monochloramine, and chlorine/ammonia additions) indicated organic chloramine formation could lead to a possible overestimation of disinfection capacity in many chloraminated water systems that add chlorine followed by an ammonia addition to form monochloramine.     

污水氯消毒过程中有机氯胺的生成及其影响

消毒是保证污水再生利用水质安全的必要措施，氯消毒是最常用的消毒方法。在氯消毒过程中，污水中的含氮有机物与氯反应会生成有毒有害的有机氯胺。国外很早就开始了对有机氯胺的研究，而国内对有机氯胺的关注较少。有机氯胺在一定条件下可以在自然水体中长时间稳定存在，部分有机氯胺在脱氯时不易被亚硫酸钠脱除。有机氯胺一般具有一定的生物毒性，而且一些有机氯胺也是致癌消毒副产物的前体物质，对水中的生物以及人体健康会产生毒害作用。消毒过程中有机氯胺的生成不仅会降低消毒效果，而且也会影响水体中余氯的测定。     

给水管网硝化作用控制方法研究进展

介绍了氯胺消毒管网中的硝化作用及其控制方法,并对控制方法进行了总结和展望。在采用氯胺消毒的给水管网中,存在着硝化反应发生的可能性。硝化作用会造成出水亚硝酸盐含量升高、消毒剂含量降低、异养菌繁殖等危害。国内外对氯胺消毒管网中硝化作用控制方法的研究主要集中在改变出厂水水质条件-pH、提高消毒剂的浓度、优化氯胺投加方式、管道冲洗、硝化潜能曲线及投加亚氯酸根控制硝化作用。目前以上的控制方法对硝化作用起到了一定的抑制作用,但是存在控制效果不确定、不具有长期性或者增加生成消毒副产物的风险。因此,对硝化作用的控制方法有待深入研究。笔者提出了氯胺、二氧化氯联合消毒控制硝化作用的方法。     

高锰酸钾与氯胺联用预处理控制三卤甲烷生成

考察了高锰酸钾与氯胺联用预处理工艺对三卤甲烷（THMs）形成的控制作用．结果表明,在通常给水处理的高锰酸钾投量范围内（〈2mg／L）,高锰酸钾与氯胺协同预处理可以有效降低THMs的生成量,高锰酸钾对三卤甲烷形成的控制作用是由多种作用机制共同作用的结果．与投药总量相同的单独氯胺工艺相比,采用高锰酸钾与氯胺联用预处理工艺,可以在提高消毒效果的前提下,进一步减少THMs的生成量．因此,采用该技术可以使预处理后水质的化学安全性和微生物安全性均得到提高．     

The kinetics and products of the chlorination of caffeine in aqueous solution

The kinetics and products of the reaction between aqueous hypochlorous acid and caffeine have been evaluated. The reaction was found to be dependent on pH only to the extent that it influences the fraction of FAC which is in the form of HOCl. The kinetics were found to be well represented by the expression: The rate constant had a value of 162 ± 32 M⁻² s⁻¹. For each mol of caffeine consumed, 6.3 mol of FAC were consumed. The chlorination reaction proceeded primarily by ring cleavage and rearrangement forming nonoaromatic nitrogen heterocycles. 8-Chlorocaffeine was unequivocally identified as an aqueous chlorination product but was found to be formed only to a small extent and under rather limited conditions. No stable organic chloramines were formed.     

A spectrophotometric study of the formation of an unidentified monochloramine decomposition product

This paper reports on a study of the formation of an unidentified product(s) of the slow decomposition of monochloramine in organic free aqueous solutions at pH values and Cl/N ratios of importance in the chloramination disinfection of drinking water. Chloramine and total oxidant concentrations determined spectrophotometrically in these solutions became significantly greater with time than those determined by a titrimetric method due to the absorbance of the unidentified product(s). The u.v. spectra of the product(s) was calculated from the difference between measured and predicted spectra and was similar to that obtained in a chloramine free solution resulting from the rapid decomposition of dichloramine at high pH. No spectrophotometric evidence could be found for the formation of significant concentrations of nitrite and/or nitrate.Relative concentration changes of the unidentified product(s) as measured by its calculated absorbance at 243 nm showed that the product(s) accumulates with time and therefore is not likely to be an intermediate in the formation of nitrogen gas. Both increased pH and phosphate buffer increased its formation rate. A formation mechanism involving the decomposition of dichloramine is suggested. Findings suggest that the age/history of chloramine solutions could be an important variable in toxicological studies of chloramines and their reaction products depending on the health effects of the unidentified product(s).     

The kinetics and primary products of uracil chlorination

The reaction between free available chlorine (FAC) and the pyrinidine base uracil, was studied over a pH range of 5–9 and at a range of FAC to uracil ratios between 0.5 and 5 mol mol⁻¹. Rate constants for the reaction were obtained and the primary uracil chlorination products identified.The reaction was found to adhere very well to mixed second order kinetics at FAC to uracil molar ratios 1.0. At a ratio of 5 mol mol⁻¹, the reaction demonstrated a reasonable empirical fit to the same kinetic model. The rate constant was markedly pH dependent increasing from approx. 0.3 M⁻¹ s⁻¹ at pH = 5 to 5 M⁻¹ s⁻¹ above pH = 7 at low molar ratios while the respective values at high molar ratios were approx. 7 and 90 M⁻¹ s⁻¹.At low FAC uracil ratios the chlorination reaction yielded exclusively 5-chlorouracil while at the higher ratios, a dichlorouracil was isolated in a pure form and characterized spectrometrically. This material was the only organic chloramine detected in any of the systems. While evidence was obtained for breakdown of the uracil ring, little evidence for formation of secondary chloramines was found. The characteristic odor of nitrogen trichloride was noted at the higher FAC/uracil ratios. FAC consumption increased from 1 mol of FAC per mol of uracil consumed at the low molar ratios to 3 mol mol⁻¹ at initial ratios of ≈ 5 mol FAC per mol uracil.     

The fate of chlorine in recirculating cooling towers Field results

Chlorine and chloramines are volatile compounds which are stripped (“flashed off”) from recirculating cooling water systems by the large volumes of air which flow through the water in the cooling tower. The fraction of a volatile gas, such as hypochlorous acid (HOCl), which is removed by stripping is determined by Henry's constant H for that gas: H = X_G/X_L, where X_G is the mole fraction of the gas in the air and X_L is the mole fraction of the gas in the water. We have measured H for HOCl, OCl⁻, NH₃, NH₂Cl, NHCl₂ and NCl₃ at 20 and 40°C. We found H = 0.076 for HOCl, compared to 0.71 for NH₃, at 20°C. At 40°C, H was about 2.5-fold larger for HOCl. This means that 10–15% of the HOCl is stripped from cooling water on each passage through a typical cooling tower. The measured flashoff of free available chlorine (HOCl + OCl⁻) was markedly pH-sensitive with a pK of 7.5, exactly as expected if HOCl is volatile but OCl⁻ is not. The data permit a quantitative understanding of the fate of chlorine in cooling systems. The values of H at 40°C for NH₂Cl, NHCl₂ and NCl₃ were 1.28, 3.76 and 1067. This means that all of the chloramines are quickly stripped in a cooling tower.     

Inactivation of heterotrophic bacterial populations in finished drinking water by chlorine and chloramines

The die-off of heterotrophic bacteria from a finished drinking water reservoir, located in southern California, was evaluated using chloramines and free chlorine. Understanding the inactivation of hetertrophic populations is valuable because it reflects the response to disinfection of naturally occurring organisms in their native state and environments. Disinfection studies with the heterotrophic bacterial group were performed during summer and winter months using different chloramine application techniques at pH 6 and 8. In addition, bacteria surviving exposure to chloramines and free chlorine was influenced predominantly by the presence of highly chlorine tolerant, red-pigmented bacteria, identified as Flavobacterium spp. Inactivation by chloramines, though, was chiefly dependent upon the method of application and pH. Viable bacteria recovered from the indigenous population after 60 min of exposure to chloramines (1.0 mg l⁻¹, pH 8) included members of Pseudomonas, Acinetobacter and Flavobacterium. In general, with contact times of 1 h or more, free chlorine and chloramine solutions (1.0–1.6 mg l⁻¹, pH 8) reduced total count levels below 50 colony forming units ml⁻¹.