The principle of SODIS is based on Ultraviolet water treatment . It uses two components of the sunlight for the water disinfection process :Ultraviolet radiationand infrared radiation. UV-A radiation(wavelength 320-400 nm) interacts with the DNA, nucleic acids and enzymes of the organic cell, destroys the cell molecular structures which leads to cell deaths. UV-A radiation also reacts with oxygen dissolved in the water producing highly reactive forms of oxygen (oxygen free radicals and Hydrogen peroxide], that can help the germicidal process. Infrared radiation is a long-wave form of sun radiation, it can be felt as heat, as it is responsible for raising the fluid temperature. Studies had proven that 99.9% of microorganisms in the water are eliminated if the water is heated to 50-60°C for one hour. In order to disinfect contaminated water for drinking effectively, it is recommended to expose the contaminated water to full sunlight using clear PET bottles for 6 hours.If water temperatures exceed 50°C, one hour of exposure is sufficient to obtain safe drinking water.When the weather is cloudy for more than 50% , the contaminated water need to be exposed for 2 consecutive days. The treatment efficiency can be improved by raising the fluid temperature and exposing the contaminated water to additional reflecting surfaces such as aluminium or corrugated iron sheets.