【作者】 陆钢；

【导师】 李朝林；

【作者基本信息】 哈尔滨工业大学 ， 环境科学与工程， 2011， 博士

【摘要】 紫外消毒不产生消毒副产物,易于自动化控制,具备很大的应用空间。但是,现在的紫外消毒系统均为浸没式,普遍存在下列问题:更换灯管困难;石英管壁需要经常维护清洗;紫外线利用效率低、能耗高;紫外灯直接浸没水中,紫外灯中的汞对环境和人体健康存在潜在威胁;对液态食品的消毒存在困难,而且紫外灯管的直接加热作用会引起食品变质。本文针对以上不足,提出了一种高效、可靠的光纤传导紫外光消毒技术。该技术利用光学聚焦系统将光源产生的紫外光汇聚于一点,然后再通过石英光纤导入水中,并在光纤散光点处均匀透射,从而灭活水中微生物。水消毒研究:(1)本论文分别对新方法中的光源、聚焦系统、光纤和消毒室内光纤分布密度、流态和多级串联应用做了详细研究和优化,通过对实验室配水、实际自来水和污水的消毒试验证实了新方法具有突出的杀菌能力;(2)在间歇式消毒配水试验中,经过光纤分布优化的光纤头发光光纤装置对大肠杆菌的消毒效率高于侧发光光纤装置,明显高于传统低压紫外灯,而且其应用的紫外剂量明显低于传统低压紫外灯。以上结果表明,石英光纤的灵活布置消除了紫外光的消毒盲区,有效地提高了消毒效率;(3)在对未加氯消毒的实际自来水样消毒试验中,本装置可以将水中的细菌总数和总大肠菌群数杀灭到未检出水平,满足饮用水卫生标准;(4)杀菌动力学研究结果表明,本装置对大肠杆菌的杀灭很好的符合Chick-Watson杀菌动力学模型,因此,在本装置中,紫外光剂量是导致大肠杆菌致死的直接原因;(5)在连续流消毒配水试验中,考察了浊度、铁盐和腐殖质酸等水质影响因素对本装置杀菌率的影响,其中腐殖质酸影响最明显;(6)芽孢作为很多类致病微生物在特殊情况下的一种生命存在形式,具有一定的抗高温和抗氯消毒特性。而本装置对其杀灭效果明显。浊度、铁盐和腐殖质酸等水质参数对芽孢的紫外杀灭率有一定影响,但明显低于对大肠杆菌杀灭率的影响;(7)针对实际污水消毒,选择了更高光纤密度的消毒室。现场消毒试验中,经本装置处理后的一级B市政污水或更差水质的污水均可以达标排放;(8)为了指导本装置在实际水消毒中的应用,本文给出了理想纯水中的紫外穿透率(UVT)对光纤装置应用紫外剂量影响的关系式,而且还给出了不同水质情况下本装置的应用紫外剂量。啤酒消毒研究:石英光纤技术可以很好实现对啤酒的薄膜流消毒。本文优化了光纤密度、啤酒薄膜厚度和啤酒处理量。本装置对瓶装啤酒中接种的大肠杆菌和扎啤中污染的大肠杆菌的杀灭效果可以达到美国食品药监局标准和啤酒微生物国家标准。而且本装置可以实现对导致啤酒变质的微生物(乳酸菌)有较高的杀灭率。因此,啤酒的保质期可以得到延长。在相同紫外剂量下,瓶装啤酒和扎啤中酿酒酵母的杀灭率远远小于大肠杆菌和乳酸菌的杀灭率。在扎啤中存在一定的活啤酒酵母被认为可以改善啤酒口味,使啤酒口感更好、营养更丰富。苹果汁消毒研究:新技术对市面上销售的澄清苹果汁和鲜榨苹果汁中导致苹果汁变质的微生物和致病微生物具有突出的杀灭能力。瓶装苹果汁中的大肠杆菌和乳酸菌的杀灭率可以达到6个对数级水平,然而酵母菌的杀灭率只有4个对数级水平。在被污染的鲜榨果汁中,天然生长的大肠菌群、乳酸杆菌和霉菌酵母菌可以被杀灭到低于10CFU/mL水平。以上结论是对本项新技术可以应用于给水、污水、液态食品紫外消毒领域的一种肯定。同时,也指出了新技术对啤酒、苹果汁等液态食品安全的保障和保质期的提升方向上具有广阔的应用前景。更多还原

【Abstract】 Ultraviolet (UV) disinfection does not produce DBPs. It is easy for auto-control and widespread use. As there are several problems in traditional ultraviolet (UV) disinfection techniques, a highly efficient, reliable and economical technology, named silica optical fiber transferring UV disinfection technique, was firstly given. The working principle is that UV light is gathered by the lamp reflector to converge to a light point. UV light can be transferred into the water through the side-glowing optical fibers, to ensure the uniformity of the UV intensity in the water, so the bacteria will be well inactivated. The new technique has a number of advantages: (i) it is easy to replace the UV lamp due to the separation of UV lamp and mercury leakage is avoided; (ii) the flexible placement of optical fibers make UV intensity well-distributed everywhere in the UV reactor; (iii) it is easy to regulate the thin-film thickness for ensuring enough UV radiation on bactaria; (iiii) the UV lamp can prevent beer from heating, which is thermally unstable.Water disinfection: To complete the UV apparatus, we have investigated and selected the best modules. The suitability of the UV apparatus for application could be shown in experiments with Escherichia coli (E. coli), spores, total bacterial count, total coliform and fecal coliform as risk groups. We had got the optimized distribution for both the side-glowing optical fibers and head-glowing optical fibers in the water in batch reactor study. The latter had a better germicidal efficiency than the former. After treated with head-glowing fiber apparatus, the E. coli (103~105 CFU/mL) could be reduced by 3 log orders at the irradiation time of 45s, fulfilling the Chinese standard of disinfection apparatus. After 1-min treatment, the total bacteria and total coliforms could be reduced to undetectable, fulfilling the standard. Flow pattern of the disinfection room and application in series were optimized. The UV inactivation results accorded with Chick-Watson model, in which, k was from 0.385 to 0.456. In the continuous disinfection experiments, aluminum coating reactor had higher disinfection efficiency than non-aluminum reactor and initial reactor. Two reactors in series were better for practical use. The factors of turbidity, ferric salt and humic acid were investigated and humic acid was the most significant factor. The killing of spores with heating to 80oC and chlorination was inefficient. When the time was 21 s, 4.4 log reduction of spores could be achieved. The turbidity, ferric salt and humic acid had effect on UV inactivation of spores, but they had more obvious effect on the E. coli inactivation. The apparatus could reduce spores by 3 log under the following conditions: (i) turbidity<8.8, (ii) ferric ion<0.9, and (iii) humic acid<2.5 mg/L. In the first-order B wastewater treatment, a higer optical-fiber density reactor (3.8cm×3.8cm×11.4cm) was chosen. When the wastewater flowrate was lower than 37.1 L/h, the fecal coliform could be reduced to lower than 10 CFU/mL, fulfilling wastewater discharging standard. When processing the lower-quality wastewater, 21.2 L/h would be used as the flowrate choice for fulfilling the standard.Effecting factors and applied UV doses: In order to provide a guideline for the practical use, we concluded: (i) when UVT±98% and SS 1mg/L, 4.3 mJ/mL was recommended to be used, (ii) when UVT was beteen 41% and 60% and SS 25mg/L, 11~21 mJ/mL was recommended to be used, (iii) If the wastewater contained a lot of coherent substances, like humic aicd, or cogulation effect metal ion, like ferric ion, only control of UVT and SS was not enough to achive the wastewater discharging standard. Therefore, the related disinfection experiment was needed to determine the UV dose. Beer disinfection: silica-fiber technique can realize beer thin-film disinfection well. We have optimized the fiber distribution, beer film thickness and treatment capacity. The apparatus could reduce the E. coli in the bottled beer and the draft beer to lower than 10 cFU/mL or undetectable, completely fulfilling USFDA standard and Chinese standard for beer. It could also have a better inactivation of spoilage microorganisms, such as lactic bacteria. Therefore, the shelf-life of beer would be extended. With the same UV dose, inactivation of S. cerevisae was lower than that of E. coli or lactic bacteria. However, a number of S. cerevisae still active in draft beer is one of the reasons why draft beers taste better and contain more nutrients than bottled beer.Apple-juice disinfection: the new technique could reduce the spoilage microorganisms and pathogenic microorganisms in bottled apple-juice and freshly extracted apple-juice by 6 log orders. However, only 4 log reduction of S. cerevisae could be achieved. In the UV processing of freshly extracted apple-juice, indigenous E. coli, lactic bacteria and yeasts and moulds were reduced to lower than 10 CFU/mL.The conclusions above are the approval of the new technique applying in the drinking water, wastewater and liquid foods. Meanwhile, it provides a promising approach to improving microbial safety and extending shelf-life of liquid foods, such as beer, apple-juice, etc.更多还原