Solar water disinfection

Water quality is a severe problem throughout the world. Much available water is contaminated by pathogenic microbes. This project reviews the traditional process of solar water disinfection in bottles (SODIS), discusses experiments conducted with SODIS bottles modified to thermally enhance the process, analyzes experimental data for modified SODIS containers, and suggests ways that by which the traditional process can be improved. Traditional SODIS is currently used in many rural parts of developing countries to disinfect water. The process uses ultraviolet rays and thermal effects to inactivate microorganisms that tend to cause diarrheal disease. If a sufficiently high temperature is attained to reach a synergistic UV-thermal effect range, the process of SODIS is about three times faster. However, many factors can inhibit attainment of sufficient heating of water in SODIS bottles in practice. By modifying the bottles to enhance effectiveness of sunlight in increasing the temperature of the water, SODIS can be more effective. In this research, a series of experiments were conducted over a period of four months and15 days at Arizona State University Polytechnic campus in Mesa, Arizona, U.S.A. Four different types of inexpensive materials (black paint, white paint, foam insulation, and aluminized mylar) were used individually or in combination in seven different modified configurations to assess the potential of the modifications to increase the temperatures of water inside 2-liter PET bottles. Experiments were run in triplicate. Temperatures inside the bottles, along with yard temperature, were recorded over time. Graphs were plotted for each set of experiments. The results of these experiment show that several types of modifications increased water temperature during exposure to sunlight. Water in bottles with black paint and foam insulation on the back side attained the highest temperatures, approximately 8-10 degrees Celsius above temperatures attained in plain bottles. The results of these experiments show how several inexpensive, easily obtained materials can significantly enhance the SODIS process.