Browsing by Author "Dr. Detlef R.U. Knappe, Committee Member"

Filter results by typing the first few letters
Now showing 1 - 2 of 2
  • No Thumbnail Available
    Analysis of a Low Pressure UV reactor under Multiple Upstream Elbow Configurations using UV Sensitive Fluorescent Microspheres
    (2008-08-20) Zhao, Xi; Dr. Joel Ducoste, Committee Chair; Dr. Detlef R.U. Knappe, Committee Member; Dr. Francis de los Reyes, Committee Member
    Upstream piping configuration has been known to impact the UV reactor validation using biodosimetry tests. However, the influence of upstream configuration on the UV dose distribution has not been experimentally investigated. This research was performed to evaluate the UV reactor dose distribution under multiple upstream configurations using UV sensitive fluorescent microspheres. The upstream hydraulics configurations included two kinds of 90- degree bends and one straight pipe configuration. Experimental tests were performed at 51 gpm flow rate, 91% UV transmittance (UVT) on a single lamp low-pressure high-output (LPHO) UV reactor. The UV irradiation kinetics of the photo-chemically active fluorescent microspheres was performed with bench-scale collimated beam experiments. The correlation with microspheres fluorescence intensity distribution to UV fluence distribution was achieved by a statistical process involving Bayesian and Markov chain Monte Carlo integration technique. The results of this study showed that the straight pipe configuration produced a shift in UV fluence distribution to a higher UV fluence range compared to the two elbow configurations. No significant difference was formed between the two elbow configurations. The fluorescent microspheres Bayesian method can serve as an additional test to the traditional biodosimetry for UV reactor validation by providing sensitivity in detecting design parameter change and added confidence in the results by providing unbiased UV dose behavior.
  • No Thumbnail Available
    Using Fluorescent Microspheres as a Non-Biological Surrogate Indicator for Sequential Disinfection Performance.
    (2003-07-11) Baeza, Ana Carolina; Dr. Francis de los Reyes, Committee Member; Dr. Joel Ducoste, Committee Chair; Dr. Detlef R.U. Knappe, Committee Member
    Fluorescent YG-microspheres (Polysciences Inc.) were evaluated to simulate Cryptosporidium inactivation in treatment systems that utilize multiple disinfectants. Experiments were performed in batch reactors including an ozone primary stage at pH 7 and a secondary free chlorine treatment at pH 6. The impact of exposure to the chemical disinfectants was accomplished by tracking the changes in fluorescence distribution using a flow cytometer. Microsphere survival ratios (N/No) were calibrated to replicate the inactivation of different Cryptosporidium strains by selecting an appropriate threshold in a histogram analysis. The threshold value corresponds to a boundary between the beads representing the viable and non-viable Cryptosporidium cysts. The results suggest that YG-fluorescent microspheres are adequate non-biological surrogate indicators for the evaluation of sequential disinfection performance. In addition, it was found that microspheres had collateral reactions with sodium sulfite, affecting the physical integrity of the particle, a phenomenon that does not occur with the organism cyst. Analysis of the data showed that dot/density plot, which display the bead morphology characteristics, should be performed along with the histogram analysis to ensure the correct microsphere survival ratio outcome. Lastly, microsphere structural tests showed that the sequential disinfection mechanism consists of a polystyrene surface damage caused by ozone. This polystyrene damage enhances the diffusion of the secondary disinfectant into the microsphere, where it degrades the dye available in the opened polymer layer.