Research On Silica Fiber Transmitting Uv Disinfection Technology And Its Efficiency

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.