A Swimming Pool without Chlorine

Stefan Maibücher, Alexander Solms

project report

We learned from an article in the newspaper "Zeit" that a chlorine-free water disinfection method based on UV light had been discovered. As we had suffered from chlorine in swimming pools in the past and as we had heard a lot about the problems of others (irritated eyes due to trihalomethanes), we decided to design "a swimming pool without chlorine".

In order to prove that UV light kills microorganisms, we illuminated unicellular organisms with black light. However, we could not find any dead or damaged microorganisms after the experiement. Therefore we called the "Zeit" and asked for the original article. From the original article, which was in English and had been published in "Business Week", we learned that we had to use normal fluorescent tubes without coating. We found such a lamp in our school's biology lab.

We did take appropriate safety measures to ensure that we would not be exposed to UV light. All bacteria of our sample had died after 1.5 hours of illumination with our small 254 nm UV lamp. We discussed our results with a waterworks director only to discover that this method had been known for years. This disappointing news made us wonder why this method is not being used in swimming pools. Prof. Lopez from the German Federal Environmental Agency was able to give us a satisfactory answer: "People continuously add germs to the water and chlorine acts locally. The use of UV light would require pumping of the water through a machine and someone else could be infected before this happens." Despite this challenge, we designed "a swimming pool without chlorine" including UV-disinfecting suction pipes and UV-disinfecting pool walls.

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