Towards identification of floc compounds in water using multi-frequency fluorescence lifetime analysis
Abstract
UV disinfection is commonly used in water treatment to inactivate pathogens such as Cryptosporidium and viruses to prevent diseases such as cryptosporidiosis and norovirus in communities. Disinfection typically follows water treatment steps, such as coagulation, flocculation, clarification, and filtration. However, particles in water, for example, flocs 0.1 to 100 μm in diameter, made from humic and inorganic substances present in the water, surrounding a Cryptosporidium oocyst or virus, can protect the pathogens from UV exposure. Although water treatment steps prior to disinfection remove 99% of the particulates, particles can still be present in the 1000s to 10,000’s per litre after filtration. While the chances of a floc particle carrying a virus or oocyst are typically low, in some regions, particularly during calving in the dairy industry, oocyst concentrations in the water might be high due to cryptosporidiosis in calves. Therefore, it is useful to test the properties of the floc compound for UV penetration to determine whether the disinfection method is appropriate. In this thesis, a technique that uses multi-frequency analysis to measure the fluorescence lifetime of a fluorophore to provide information on particle composition is presented. Frequency-domain fluorescence fluorometry was used to determine the fluorescence lifetime. This was achieved using an experimental setup that used a laser diode operating at 100 mW and modulated at 10–60 MHz to excite the…
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