At present, one out of every six people in the Earth does not have access to safe drinking water. For many poor people, drinking “safe water” is not an easy task. The "plastic bottle + sunshine" method used for water disinfection by the World Health Organization has been expected to meet the basic survival needs of many people.

The new method is simple. You only need a few empty plastic bottles, plenty of sunlight and a black background. The process was to expose the clear plastic bottle filled with water to a flat place for five hours. The ultraviolet rays in the sun and the heat they cause will kill most of the pathogenic microorganisms in the water. Unlike boiling water heating, this sterilization method does not require any fuel. In addition, if you have the conditions to paint the bottom of the plastic bottle black, or put the bottle on a black corrugated iron or plastic cloth, the disinfection effect will be more significant, because the black corrugated iron or plastic cloth can absorb more heat, In order to eliminate bacteria in the water more cleanly and completely.

The World Health Organization named this method of relieving waste as "Solar Water Disinfection Method" (SODIS). Rickard Helmer, head of the organization’s health and environment department, said: “Every 2.5 million people die every year because they drink unclean water. If they can use this method to get safe and pure water, they don’t need to The cost of losing lives. The safety and reliability of the SODIS method has been proven in practice."

However, this method of nearly zero cost is limited to "adoption". The inventor of this method, Martin Wegellin, a researcher at the Swiss Academy of Environmental Sciences and Technology, said that although this method is simple and easy, it does not kill all microorganisms in the water. However, for many countries that are sunny and short of funds, the "plastic bottle + sunlight" method has largely solved their immediate needs.

At the same time, the World Health Organization calls on developing countries to pay attention to chlorine disinfection technology. This technique is equally simple and effective.

According to a survey recently released by the World Health Organization, 80%-90% of diseases and more than one-third of deaths in developing countries are related to water that is infected by bacteria or chemically contaminated. In Uganda, for example, only 65% ​​of urban residents can use safe drinking water. In rural areas, this proportion is only 40%. Every year, 3.4 million people die from drinking unclean water or swimming in contaminated water. The common diseases are malaria, dysentery and dracunculiasis.