Effectiveness of SODIS (Solar Disinfection) in Urban and Rural Areas of Bangladesh

Abstract

Most of the people in the developing countries have less access to the safe drinking water. Bangladesh is one of the developing countries. Most of the health problems in Bangladesh are water borne. The financial condition of the people, living in the rural and semi urban areas of Bangladesh is very poor. Most of them don’t have the budget for drinking water treatment. Keeping that in mind, solar disinfection system (SODIS) can be effective in reducing level of water contamination in Bangladesh. At present More than 5 million people Worldwide clean their drinking water with the SODIS method. Presently SODIS projects have been conducted in 15 countries of Africa, Asia and Latin America. In SODIS solar energy is used in the form of ultra violate radiation and to a lesser extend infrared heat to disinfect or destroy pathogenic microorganisms in the water. This process is carried out with several steps like collecting PET (2-L Poly Ethylene Terephthalate) bottles, filling with contaminated water, shake and close, placing bottles in the full sun for at least 6 hours. The concentrated sunlight radiation and synergistic effect of thermal energy reduce the fecal contamination in water. To study the effects of solar radiation and heating on the inactivation of Total Coliform (T.C), Fecal Coliform (F.C), Escherichia Coli (E.Coli), and Heterotrophic Plate Count (HPC) experiments were conducted. Water samples were exposed to sunlight in plastic bottles. Plastic bottles were used because they are common, inexpensive containers that can be found worldwide. Different types of media are used to test different parameters. For each experiment, the test bottles were prepared. The initial temperature of each test bottle was recorded and samples were taken to enumerate the starting concentration of bacteria. The test bottles were then exposed to sunlight and samples were collected at predetermined intervals to determine the Total Coliform (T.C), Fecal Coliform (F.C), Escherichia Coli (E.Coli), Heterotrophic Plate Count (HPC) concentration. During each sampling time, air temperature, water temperature and solar irradiance were measured. To quantify the inactivation effects of heating only, laboratory experiments were conducted. So From All our Experiments, We have seen significant reduction of bacteria so SODIS is applicable in our atmosphere. PET bottle with Foil Backing surface may be the best among variations. SODIS is cheaper and Helpful for the Poor people. iv SODIS requires sufficient solar radiation. Therefore it depends on the weather and climatic conditions. SODIS requires clear water. SODIS does not change the chemical water quality. SODIS is not useful to treat large volumes of water. In case of Laboratory testing we are not counting vibrio Cholera, Salmonella and Shigella bacteria. Also not testing the amount of turbidity.