强化消毒法对水中粪肠球菌灭活效果研究

在实验室条件下,研究了自由氯、氯胺和二氧化氯在不同剂量下对水中粪肠球菌的灭活效果.结果表明,自由氯、氯胺和二氧化氯对水中粪肠球菌具有较好的灭活效果,当消毒剂投加量为1 ～4 mg/L,接触时间为30 min时,粪肠球菌的灭活率基本在99％以上;自由氯的消毒反应速率最快,其次是二氧化氯,氯胺的反应速率最慢.     

自由氯、氯胺和顺序氯化对饮用水消毒效果的试验研究

研究了自由氯、氯胺和顺序氯化三种消毒方式对大肠埃希氏菌和粪肠球菌的灭活效果.结果表明,自由氯浓度越高,对细菌的灭活速率和最终灭活率越大;氯胺浓度越高,对细菌的灭活速率和最终灭活率越大;顺序氯化消毒效果优于单独使用自由氯或氯胺时的消毒效果.同时,还探讨了pH和温度对三种消毒方式的影响.     

生长环境对消毒剂灭活粪肠球菌影响效果的试验研究

通过改变培养基稀释度和培养温度以及添加无机生长元素（氯化钾、硫酸镁、三氯化铁）研究了自由氯、氯胺和二氧化氯对不同生长环境下所培养的粪肠球菌的灭活情况。结果表明，当粪肠球菌在100倍稀释的肉汤培养基上生长时，达到3log去除率氯和二氧化氯所需的0值分别增加了2．1和5．5倍，而氯胺所需的D值变化很小；将粪肠球菌的生长温度从22℃调整至44．5℃时，达到3log去除率氯胺所需的C≠值下降了2倍，自由氯和二氧化氯所需的C￡值则变化不大；在营养肉汤培养基中投加K＋（4mmol／L）、Mg2＋（0．4mmol／L）和Fe3＋（0．08mmol／L）后，粪肠球菌对自由氯和二氧化氯的抗性提高了，对氯胺的抗性则变化不大，达到3log去除率自由氯和二氧化氯所需的C￡值最大分别增加了约2．3和19倍。     

常规水处理工艺预氧化去除剑水蚤试验研究

对比了次氯酸钠、氯胺和二氧化氯对剑水蚤的杀灭效果,并确定了最佳投加比例、投加顺序和投加量。结果表明:有效氯浓度为3. 0 mg/L,接触时间为1. 5 h时,在先氯后氨、氯氨比4∶1、投加间隔时间30 s的试验条件下投加氯胺,以及单独投加二氧化氯可完全去除剑水蚤,灭活效果优于单独投加次氯酸钠、其他氯氨比和先氨后氯的投加方式。     

二氧化氯、氯胺顺序投加联合消毒工艺的研究

以天津市某自来水厂的滤后水为研究对象,采用二氧化氯、氯胺顺序投加联合消毒工艺对其进行消毒处理。运用化学分析和生物学试验的方法,考察了经不同投量的组合消毒后消毒剂残余量的变化,以及联合工艺的消毒效果和持续消毒能力。试验结果表明,经不同投量组合的二氧化氯、氯胺顺序投加联合消毒后,出水中的细菌总数及总大肠菌群均达到《生活饮用水卫生标准》的要求。氯胺投量对总余氯和二氧化氯残余量的影响显著,而二氧化氯的投加量对其残余量的影响不大。二氧化氯、氯胺顺序投加联合消毒工艺在低投量组合下就能达到良好的消毒效果,且持续消毒能力强。     

二氧化氯消毒效果影响因素试验研究

通过对比实验,考察了二氧化氯、液氯和氯胺三种常用消毒剂对肠道菌的灭活效果,以及pH、温度、培养基稀释倍数等因素对二氧化氯消毒效果的影响.试验结果表明,二氧化氯消毒剂具有高效性和广谱性;pH值在6.0～9.0内变化,二氧化氯的消毒效果几乎不受影响;温度的升高会加强二氧化氯的灭菌效果;随着培养基稀释倍数的增加,粪肠球菌对二...     

硫代硫酸钠脱氯特性及其动力学分析

考察了二级生物处理出水经氯消毒后采用硫代硫酸钠脱氯的效果。结果表明，在氯消毒后初始余氯为10mgCl2／L的条件下，当反应时间为60min、硫代硫酸钠投量由理论投加量的100％增加至500％时，余氯去除率由41．2％增加到95．5％。硫代硫酸钠脱氯过程为分步反应：在最初的1min内，余氯脱除速率最快；反应1min后，自由氯脱除呈现零级反应，一氯胺、有机氯胺为一级反应；自由氯脱除速度快于一氯胺和有机氯胺，无机氯胺和有机氯胺是硫代硫酸钠脱氯反应速率的限制因素。当以硫代硫酸钠作为脱氯剂时，采用普通活性污泥法的污水处理厂需通过提高硫代硫酸钠投加量来实现快速脱氯，而采用生物脱氮工艺且硝化效果良好的污水处理厂只要保证足够的脱氯反应时间即可实现很好的脱氯效果。     

应用灰色关联分析研究饮用水二氧化氯消毒

以粪肠球菌为例,应用灰色关联分析方法,研究了影响二氧化氯消毒各因素的主次顺序。结果表明,影响二氧化氯消毒效果各因素的主次顺序为:接触时间>二氧化氯浓度>CT值>细菌浓度>温度>pH,该研究方法可为实际生产提供理论依据。     

饮用水中绿麦隆的氯胺化降解探究

系统研究了广泛应用的脲类除草剂绿麦隆在饮用水氯胺化消毒过程中的降解特性,考察了不同的氯胺投加量、pH值、溴离子浓度、水源等条件下绿麦隆的氯胺化降解规律。结果表明,绿麦隆的氯胺化降解速率较慢,由于氯胺自降解反应的存在,其反应机理也较为复杂。随着氯胺初始投加量逐渐增大,绿麦隆降解速率明显加快;不同pH值下绿麦隆的氯胺化降解速率变化明显,当pH值为6~7.5时降解速率较快,尤其在pH值为6时降解最快,在pH值为4.5时降解最慢;不同的溴离子背景浓度下,绿麦隆的氯胺化降解速率没有明显差异;在不同水质背景条件下,当pH值为6时,绿麦隆的氯胺化降解速率具有明显的差异性,而当pH值为7时绿麦隆的氯胺化降解速率变化不显著。     

二氧化氯和氯联合消毒耦合机制试验研究

分析了铸铁管、钢管和PVC管中不同消毒剂投加量下二氧化氯和氯联合消毒时二者的衰减规律.结果表明,不同管材中二氧化氯和氯联合消毒时二者的衰减速率各不相同,且联合消毒时二氧化氯的衰减速率低于单独采用二氧化氯消毒时的.     

Free chlorine demand and cell survival of microbial suspensions

The utility of chlorine residual and chlorine demand as a surrogate for microbial contamination in the water distribution system was evaluated. The chlorine demanded by and cell survival of pure culture suspensions of Escherichia coli, Staphylococcus epidermidis, and Mycobacterium aurum were quantified in solutions with initial free chlorine concentrations of 0.20, 0.40, and 0.80 mg/L. The chlorine demand increased with initial concentration of cells and free chlorine for all species. At equivalent initial cell concentrations, chlorine demand was greatest for M. aurum, followed by S. epidermidis and E. coli. The chlorine contact time required for a 3-log inactivation of E. coli, S. epidermidis, and M. aurum was calculated as 0.032+/-0.009, 0.221+/-0.080, and 42.9+/-2.71 mg min/L, respectively. The ultimate chlorine demand and cell survival were directly proportional. No chlorine demand was observed at cell concentrations less than 10(5)CFU/mL for E. coli or 10(4)CFU/mL for S. epidermidis. M. aurum demanded chlorine at all initial cell concentrations including 10(3)CFU/mL, which was the detection limit of the cell quantification assay. Chlorine demand was determined to be a suitable surrogate indicator of the organisms studied and its utility may be enhanced in locations of the water distribution system that maintain a higher free chlorine residual.     

Chlorination of pure bacterial cultures in aqueous solution

The fate and distribution of chlorine in aqueous solutions containing four pure bacterial cultures was studied. Solutions were subjected to chlorination at different initial free chlorine concentrations. Resulting concentrations of residual chlorine were determined by both DPD/FAS titration and membrane introduction mass spectrometry (MIMS). In all cases, false-positive breakpoint chlorination curves, probably attributable to the formation of chloroorganic-N compounds, were observed by DPD/FAS titration, while little or no inorganic residual chloramine was found by MIMS. Free chlorine was observed in similar quantities by both methods after chlorine demand by bacterial cellular materials in solution was satisfied. These results indicated the residual chloramines existed in the form of organic chloramines; these compounds are generally recognized as being poor antimicrobial agents. Further investigation confirmed that the bacterial cells were the source of organic-N compounds. The kinetics of chlorination of pure bacterial suspensions was also studied. The pattern of residual chlorine decay following chlorination of the bacterial suspensions indicated rapid initial free chlorine consumption, followed by slow free chlorine consumption, with trace quantities of inorganic chloramine being formed.     

Combined toxicity of free chlorine, chloramine and temperature to stage I larvae of the American lobster Homarus americanus

The differential effects of free chlorine and chloramine on stage I larvae of the American lobster Homarus americanus have been investigated in continuous flow bioassay units. Applied chloramine was more toxic than corresponding concentrations of applied free chlorine to lobster larvae with estimated lc₅₀ values at 25° of 16.30 mg/l applied free chlorine and 2.02 mg/l applied chloramine. The synergistic effect of temperature on the toxicity of both free chlorine and chloramine has also been demonstrated. Exposure to applied free chlorine at 20° resulted in no significant mortality of test organisms, whereas exposure at 30° resulted in an estimated lc₅₀ value of 2.50 mg/l. Applied chloramine was considerably more toxic with an estimated lc₅₀ value at 20° of 4.08 mg/l and at 30° of 0.56 mg/l.The action of each toxicant appeared to be an alteration of standard metabolic activity as revealed by changes in respiration rates during and after exposure to applied free chlorine and chloramine. Initial respiratory stress was detected during exposure to 0.05 mg/l applied chloramine and 5.00 mg/l applied free chlorine. Reductions in respiration rates 48 h after exposure were observed with exposure to all concentrations tested, similar results being obtained following exposure to 0.05 mg/l applied chloramine and 0.10 mg/l applied free chlorine. These results are indicative of the need for information in addition to that obtained in standard bioassays for an adequate assessment of chlorine toxicity.The apparent chlorine demand of the seawater used in this study was determined after removal of particulate and dissolved organics and ammonia. Approximately 18% of the applied level of free chlorine and chloramine was recovered as residuals, measured by amperometric titration; however, no reason for this low recovery has been determined. Until it has been established that undetected chlorine and chloramine in seawater do not result in the production of toxic compounds, both applied and residual levels should be reported in toxicity studies.     

Continuous monitoring of residual chlorine concentrations in response to controlled microbial intrusions in a laboratory-scale distribution system

The objective of this work was to evaluate the efficacy of deploying free chlorine sensors as surrogate monitors for bacterial contamination events in drinking water distribution systems. An on-line sensor integral with a laboratory-scale distribution system (LDS) was shown to respond rapidly to changes in residual free chlorine concentrations induced by injected loads of Escherichia coli suspended in a chlorine demand free buffer. The magnitude of the residual response was proportional to the injected cell concentration, the background free chlorine concentration in the LDS, and the contact time between the chlorine residual and the injected suspension, consistent with previous results in batch reactors. The magnitude of the residual response was predicted when kinetic models developed from reaction kinetics between free chlorine and E. coli determined in batch systems were evaluated at contact times determined from LDS hydraulics. This result highlights the suitability of using batch kinetics when modeling contaminant-induced chlorine decay in the distribution system. Modeling the propagation of chlorine demand signals generated by specific pathogens could aid in the assessment of distribution system vulnerability.     

Comparison of disinfection byproduct formation from chlorine and alternative disinfectants

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.