Lagrangian actinometry (LA) has shown advantages as a tool for validation of UV reactors, such as ability to measure dose distribution. However, several problems involving dyed microspheres (DMS) used in LA have been identified. First, ambient particles present in some water sources could have similar sizes and fluorescence intensity (FI) with the DMS, and could interfere in flow cytometry analysis. Second, the wavelength-dependent dose responses of DMS need to be examined for validation of polychromatic UV reactors. Third, LA applications of high dose range (more than 200 mJ/cm2) for inactivation of UV-resistant microorganisms have not been studied. The primary goal of this research is to develop DMS method for validation of “high dose” reactors.
A collimated medium-pressure (MP) UV source and bandpass optical filters were used to conduct wavelength-dependent dose-response experiments for three different types of DMS (nominally 6, 10 and 15 µm) over the entire germicidal UV spectrum for a UV dose range of 0–450 mJ/cm2. Internal (microsphere) standards were implemented and applied for wavelength-dependent dose-response samples to calibrate the measurements in flow cytometry. In applying this approach, variations of the instrument optical responses were reduced. Action spectra of three different types of DMS were established. The action spectra of 6 and 10 µm DMS were similar to several microorganisms within the most effective range of wavelengths for a MP UV disinfection system, which supports the ability of prediction of microbial disinfection performance using LA. A 3-LPHO-lamp reactor and an 18-LPHO-lamp reactor were validated by LA and biodosimetry using three different sizes of DMS, 6, 10 and 15 µm and environmental isolates of Bacillus pumilus spores. Four flow rates were applied for validation of each reactor. There were some significant variations between replicate samples at lower flow rates for the 3-lamp reactor, possibly due to instabilities of the reactor at low flow rates. The ability to capture these variations is also beneficial to understand the limitation of the reactor. LA and biodosimetry results did not agree with each other for the 18-lamp-reactor test, possibly due to extrapolation of DMS dose responses, uncertainty in spore dose-response relationship, and sample contamination.
|Advisor:||Blatchley, Ernest R., III|
|Commitee:||Bergstrom, Donald E., Nies, Loring F., Robinson, J. P.|
|School Location:||United States -- Indiana|
|Source:||DAI-B 72/06, Dissertation Abstracts International|
|Keywords:||Dose distribution, Dyed microspheres, Lagrangian actinometry, UV resistance, Ultraviolet disinfection, Validation|
Copyright in each Dissertation and Thesis is retained by the author. All Rights Reserved
The supplemental file or files you are about to download were provided to ProQuest by the author as part of a
dissertation or thesis. The supplemental files are provided "AS IS" without warranty. ProQuest is not responsible for the
content, format or impact on the supplemental file(s) on our system. in some cases, the file type may be unknown or
may be a .exe file. We recommend caution as you open such files.
Copyright of the original materials contained in the supplemental file is retained by the author and your access to the
supplemental files is subject to the ProQuest Terms and Conditions of use.
Depending on the size of the file(s) you are downloading, the system may take some time to download them. Please be