Solar UV Disinfection of Drinking Water

According to the United Nations, nearly 800 million people (or 11% of the worldâ??s population) lack access to an improved drinking water source. Water from unimproved sources can contain harmful pathogens, and over 2,000 children die every day due to lack of clean water, mainly in developing countries. An increasingly popular approach to solving this problem is to use solar ultraviolet light (which is abundant in many of the areas that lack clean water) to deactivate the pathogens. The purpose of this research project has been to better understand solar UV disinfection by developing effectiveness spectra for several key microorganisms. With the completed spectra, we know how much each wavelength of light contributes to disinfection, and are able to design more efficient disinfection processes. Samples of the strains Salmonella typhi LT2, Vibrio harveyi, and Cryptosporidium parvum were exposed to wavelengths of light ranging from 254 nm to 330 nm using a polychromatic, medium-pressure Lamp, and deactivation was tracked as a function of dose. It is well-documented that as wavelength increases above 254 nm, the disinfection becomes exponentially less effective, and the data from this project has maintained this trend. When the results were paired with data on how much UV radiation reaches earth from the sun, it was found that wavelengths between 310 and 320 nm are the largest contributors to disinfection for S. typhi LT2 and V. harveyi, whereas 330 nm contributes the most to deactivation of C. parvum.