次氯酸钠消毒剂对绕线虫的灭活动力学研究

绕线虫是饮用水中检出率较高的一种线虫。次氯酸钠消毒剂对绕线虫的灭活试验结果表明:当次氯酸钠浓度为80 mg/L、接触时间为180 min时绕线虫的灭活率仅达87%,显示了绕线虫对氯消毒剂有很强的抵抗力。次氯酸钠消毒剂对绕线虫的灭活过程表现为两个阶段:不能使绕线虫致死的延迟作用阶段和一级反应阶段。延迟作用时间与次氯酸钠浓度有相关关系;一级反应可用Hom模型反映次氯酸钠浓度和接触时间与绕线虫灭活率之间的关系。     

过氧化氢对绕线虫的灭活效果和动力学

以分离自饮用水的绕线虫为研究对象,探讨了过氧化氢对绕线虫的灭活效果和动力学.结果表明,绕线虫对过氧化氢灭活的抵抗力很强,在过氧化氢质量浓度201 mg·L-1和接触时间120 min的条件下绕线虫的灭活率仅达67%;在过氧化氢质量浓度201mg·L-1和接触时间120min范围内,过氧化氢对绕线虫的灭活动力学为1级反应;此外,过氧化氢质量浓度与绕线虫灭活反应速率常数之间存在正的线性相关关系.     

紫外/氯消毒在饮用水处理中的应用

饮用水处理中常用的消毒方式是氯消毒。氯消毒在控制微生物量的同时势必会增加消毒副产物产生的风险。为了降低这种风险,将紫外/氯消毒方式应用到饮用水处理过程中。本试验以炭池出水及紫外消毒系统出水为研究对象,考察了紫外线对炭池出水微生物的灭活效果和添加不同浓度消毒剂(次氯酸钠)后的微生物灭活效果,以及消毒副产物的生成情况。研究结果表明:在饮用水消毒处理过程中,采用紫外/氯消毒方式,在较低的氯消毒剂投加量下,可以更有效地控制水中的微生物数量,进而控制消毒副产物的生成量。     

紫外线相关消毒工艺在饮用水处理中的应用

叙述了国内外紫外线消毒技术在给水处理中的最新研究进展.介绍了紫外线的消毒效果、反应动力学及缺点,对紫外线与其它化学消毒剂联用消毒工艺,以及近年来发展的光催化消毒技术,UV/H2O2工艺用于消毒的可行性进行了分析.对紫外线相关消毒技术的研究趋势进行了展望,认为饮用水消毒方面,应特别针对隐孢子虫,贾第虫以及藻类等的灭活效果及影响因素进行探讨,深入研究紫外线与其它消毒剂的联用技术,加强中压汞灯的光催化消毒效果,机理的研究;藻类控制方面,应系统研究紫外线对不同藻类的灭活剂量以及预处理中对藻毒素、消毒副产物的控制,并加与其它工艺联用除藻工艺的研究.     

饮用水中隐孢子虫与贾第虫的危害及其去除灭活研究

本文在介绍"两虫"即贾第虫和隐孢子虫的生态、危害及传播的基础上,综述了常规水处理工艺、膜法及组合工艺对"两虫"去除效果;分析了各种消毒剂和消毒方法灭活的优缺点,提出多种方法协同灭活将成为水消毒技术研究和开发的一个发展方向。预处理、絮凝、沉淀、澄清和过滤等常规水处理单元不能有效去除两虫,难以保证饮用水安全;膜过滤法两虫去除效率高,但大规模应用困难较大。而常规的氯消毒剂灭活两虫的效果不佳,臭氧对两虫的灭活效果优于氯和二氧化氯;UV能有效灭活两虫,但穿透力弱,UV灯管寿命短,运行费用高;US灭活两虫,能耗比较高。单一的消毒剂灭活两虫效果欠佳,采用多种消毒剂(方法)联合使用,通过协同作用,可达到较高的灭活率。     

氯灭活水中枯草芽孢杆菌的效果

以枯草芽孢杆菌(ATCC6633)作为难灭活微生物的代表,研究了氯对水体中芽孢的灭活效果,考察了氯浓度、作用时间、反应体系pH值、温度以及芽孢初始浓度等因素的影响。结果表明,氯对芽孢的灭活过程可分为延滞期和灭活期;初始氯浓度在2.06~10.30 mg·L^-1,反应时间0~166 min,pH值6~9,温度1~30℃,初始芽孢浓度10²~10¹² cfu·ml^-1范围内,消毒剂浓度和反应时间共同影响着氯对芽孢的灭活效果,提高消毒剂投量或延长消毒反应时间,均可提高灭活率;酸性条件下氯灭活芽孢的能力强于碱性条件下;随着温度的上升,氯对芽孢的灭活能力增强;芽孢的初始浓度对氯灭活芽孢的效能影响不大。初始氯投量为8.30 mg·L^-1,pH=7,芽孢初始浓度10⁶ cfu·ml^-1,温度分别为5℃和25℃下,枯草芽孢杆菌对氯消毒剂的抗性强于炭疽芽孢杆菌。     

二氧化氯作为消毒剂在饮用水处理中的应用

二氧化氯作为饮用水消毒剂受到广泛关注.二氧化氯具有强氧化性,在饮用水消毒中对杀菌,灭活病毒和原生动物具有良好的效果.二氧化氯-液氯/二氧化氯-氯胺等联合消毒工艺也具有优良的消毒特性,研究结果表明,其处理效果优于单一二氧化氯消毒.     

沈阳地区大型真菌对不同种类线虫的毒力

从沈阳市东部山区及沈阳农业大学周边环境采集到94种野生大型真菌,并将采集到的大型真菌制成浸提液,以胞囊线虫、根结线虫、腐烂茎线虫、水稻干尖线虫和小杆线虫为靶标,初步测定了大型野生真菌对5种不同种类线虫的活性作用.研究结果表明,不同菌株对不同种类线虫毒力作用具有选择性差异.对其中一种线虫的校正死亡率达到70%以上的有12种大型野生真菌,有7株菌对两种以上线虫校正死亡率达到70%.菌株F70对南方根结线虫毒杀作用最高为84.13%,菌株F92对大豆胞囊线虫毒杀作用最高为95.84%,具有选择毒性,菌株F25对腐烂茎线虫毒杀作用最高为75.91%,菌株F81对小杆线虫毒杀作用最高为75.77%,而对其他植物线虫活性差,菌株F6对水稻干尖线虫毒杀作用最高为81.82%.初步鉴定有效菌株F92为鬼伞属,F70为香菇属,F6为伞菌属,F25为伞菌属和F81为侧耳属.     

生防细菌J352对不同种类线虫的毒力差异

从黄瓜根际分离获得一株对多种病原真菌有较强抑制作用的细菌，用该细菌不同浓度的发酵液测定了对4种线虫的作用。结果表明，该发酵液呈微碱性，不同浓度发酵液对各种线虫均有较好的防治作用，并且毒力作用具有明显差异，对4种线虫的毒力大小顺序分别为小杆线虫、大豆胞囊线虫、根结线虫和腐烂茎线虫。     

次氯酸钠氧化消除水中双氯芬酸的动力学及影响因素

探索氯消毒剂氧化去除污水处理厂中药物与个人护理品(PPCPs)的可行性,以水体中被频繁检出的双氯芬酸(DCF)为目标污染物,以NaClO为消毒剂,考察DCF在氯化消毒过程中的反应动力学以及水体中氮素、有机物对DCF去除效果的影响规律。结果表明,NaClO氧化降解DCF过程符合2级动力学;p H5时氧化反应速率显著增高;温度对该氧化反应的影响明显且符合Van't Hoff规律,k_(app)随着温度的升高而增大。反应体系中的无机盐离子NO_2-、NH_4+以及有机物HA、十二烷基苯磺酸钠(SDBS)和Tween-80,会抑制DCF氯氧化降解,抑制效果随含量升高而加强。可为氯消毒工艺处理含PPCPs尤其是非甾体抗炎药物的生活污水提供科学基础。     

Inactivation of Enterococcus sp. by Conventional and Advanced Oxidation Processes in Synthetic Treated Urban Wastewater

The aim of this research work was to evaluate the disinfection efficiency of several techniques on the inactivation of the bacteria Enterococcus sp. inoculated in synthetic treated urban wastewater. Different types and doses of reagents and times of exposure were studied. The compared treatments include chlorination, ozone-based treatments in the absence and presence of H₂O₂ and UVA-visible irradiation-based processes with TiO₂ and H₂O₂. Different combinations of chlorine doses and times of contact inactivated all the bacteria (-7.5 log units). Ozone and O₃/H₂O₂ also achieved high disinfection levels (-6 log units), showing similar inactivation curves. However, the studied phototreatments were less efficient.     

A kinetic model for glycerol chlorination in the presence of acetic acid catalyst

A kinetic model for the chlorination of glycerol with hydrochloric acid in the use of acetic acid as catalyst is presented in this study. The model is based on a comprehensive chlorination mechanism, taking the formation of 1,3-dichloro-2-propanol and 2,3-dichloro-1-propanol into account while ignoring the formation of any intermediate in the chlorination system. Simulations were carried out under different chlorination conditions to calculate the concentrations of the main chemical species in the reaction system. The validity of the model was examined via a comparison of the calculated data with the experimental data on the chlorination of glycerol with hydrochloric acid at 363–393 K. The results show the model is capable of describing the chlorination performance with good agreement with experimental data.     

物理修饰对淀粉抗消化性能和分子结构的影响

淀粉颗粒通过物理修饰,调节不同的水质量分数、温度、压力和处理时间,可以改变淀粉的抗消化性能。实验结果表明,压力和水质量分数对淀粉抗消化性能的影响显著(P<0.05),温度和时间这两个因素对淀粉的抗消化性能影响较小(P<0.05)。由正交实验结果可知,获得高抗消化淀粉质量分数的最佳处理条件为:温度120℃,压力9×105Pa,水质量分数为20%,处理时间1.5 h。经核磁共振、X射线衍射和差示扫描量热法对物理修饰后的淀粉分子结晶结构和热性能的分析发现,随着淀粉抗消化性能的提高,分子的有序化程度提高,但这些有序化的结构发生了由B型向V型的晶型转变。     

乙酸光氯化反应制备氯乙酸工艺的研究

设计了一种新型实验室氯化反应器－－光照内环流气液反应器，应用于乙酸光氯化制氯乙酸的反应。该反应器具有光照效果好、易环流、密封性能好等。大环流反应器中考察了光照下不同反应温度对乙酸氯反应的影响，实测了不同温度下，乙酸、氯乙酸和二氯乙酸的浓度随反应时间的变化关系。将乙酸在环流反应器中的光氯伦反应结果与乙酐为催化剂的氯化反应结果进行了比较，发现光氯反应速率与乙酐为催化剂时的氯化速度时相当，但二氯乙酸生成量明显偏高，为了抑制二氯乙酸的生成，在光照的同时加入乙酐作为抑制剂，考察了不同的乙酐用量和加入方式对二氯乙酸生成的影响。     

Electrochemical inactivation of coliforms by in-situ generated hydroxyl radicals

Electrochemical disinfection is quite attractive as a promising alternative technology to chlorination. It is still debated whether conventional electrochemical disinfection, which electrolyzes the solution with very high chloride concentration to produce excess amounts of chlorine species, will generate toxic disinfection byproducts (DBPs) and have the same health risks as chlorination. To resolve this critical issue, we explored the possibility of electrochemical disinfection based on electrogenerated free radicals but not on active chlorine. The germicidal efficiency of 99.99% was achieved with a contact time of 5 min and current density of 7 mA cm⁻² for a chloride-free model wastewater contaminated by coliforms. Electron spin resonance detection clearly confirmed that hydroxyl radicals were the major germicidal species responsible for efficient electrochemical disinfection. This process would not generate poisonous DBPs due to the avoidance of dangerous chlorine species. pH in the range of 5–9 has little effect on the bacteria inactivation. Formation mechanism of hydroxyl radicals was discussed.     

Identifying the Minimal Enzymes for Unusual Carbon–Sulfur Bond Formation in Thienodolin Biosynthesis

Thienodolin (THN) features a tricyclic indole‐S‐hetero scaffold that encompasses two unique carbon–sulfur bonds. Although its biosynthetic gene cluster has been recently identified in Streptomyces albogriseolus, the essential enzymes for the formation of C?S bonds have been relatively unexplored. Here, we isolated and characterized a new biosynthetic gene cluster from Streptomyces sp. FXJ1.172. Heterologous expression, systematic gene inactivation, and in vitro biochemical characterization enable us to determine the minimum set of genes for THN synthesis, and an aminotransferase (ThnJ) for catalyzing the downstream conversion of tryptophan chlorination. In addition, we evaluated (and mainly excluded) a previously assumed pivotal intermediate by feeding experiments. With these results, we narrowed down four enzymes (ThnC–F) that are responsible for the two unprecedented C?S bond formations. Our study provides a solid basis for further unraveling of the unique C?S mechanisms.     

Allergen inactivation with colloidal silica

We evaluated the allergen inactivating effect of colloidal silica by performing enzyme-liked immunosorbent assay (ELISA) whose wells were coated with 150 ng/mL of Japanese cedar pollen allergen (Cry j 1) or mite allergen (Der f 2). The allergens were almost 100% inactivated by 100 microg/mL of colloidal silica having a particle size 5 nm, and the inactivating effect was increased by aluminum binding to the surface of the colloidal silica. The results show that colloidal silica is a promising material for allergen inactivation. Since colloidal silica forms an insoluble nondispersive solid when dried, it is expected that airborne allergens can be reduced by binding them to colloidal silica.     

Soybean Drying by Two-Dimensional Spouted Bed

Urease activity, cracking, and breakage are important factors in considering the quality of raw soybean for feed meal industries. A two-dimensional spouted bed dryer was investigated to determine its capability for thermally inactivating the urease enzyme and maintaining its other qualities. The experimental results have shown that the drying kinetics of soybean in a two-dimensional spouted bed dryer are of the form described in the thin layer drying. The expression for the model parameter in Newton's law of cooling equation accounting for the moisture contents and inlet air temperatures was developed. The initial moisture content and inlet air temperature conditions cause cracks in the kernels. The strong collision between kernels and deflector because of high superficial velocity leads to high percentage of broken soybeans in the spout region. However, the velocity of 15.9 m/s can reduce the breakage below 5%. The inactivation of urease at low-to-moderate moisture content is suitably described by the first order kinetics. The modified Monod equation is applied when the moisture content is higher than 26% dry basis due to the inhibitory effect of water content on the inactivation rate. To complete urease inactivation and maintain protein quality, the temperatures of 150°C should be used.     

Ozone for Inactivation of Aerosolized Bacteriophages

Because of increasing incidence of virus-containing aerosols, ozone was potentially considered to be a promising method to inactivate airborne viruses. In this investigation, bacteriophages MS2, phi X174, phi 6, and T7 are under evaluation. The effects of ozone concentration, contact time, different capsid architecture of virus and relative humidity (RH) on inactivating airborne viruses by ozone were evaluated in a laboratory test chamber. It was observed that the survival fraction of airborne virus decreased exponentially with increasing ozone dose. Airborne viruses required ozone doses of 0.34 to 1.98 and 0.80 to 4.19 min-mg/m ³ for 90% and 99% inactivation, respectively. For all four tested, the ozone dose for 99% inactivation was 2 times higher than that for 90% inactivation. At airborne phase with a short contact time, viruses with more complex capsid architectures were observed to be less susceptible to ozone inactivation than those with simple ones. For all tested viruses at the same inactivation, the required ozone concentration at 85% RH was lower than that at 55% RH, possibly because the generation of more radicals from ozone reacting with water vapor at the higher RH. In summary, it was concluded that ozone is highly effective for the inactivation of airborne virus.