Contamination of sand filters (Biological contamination of the filters) is a growing problem, particularly through the use of activated carbon. The newspaper article offers solutions and ideas. Disinfection against Filterverkeimung. With a water treatment and disinfection after the letters of DIN everything is done? No! Where does the air from your air flushing? If you do not know it or you can smell during the flushing, then you should urgently and carefully read to the end.
Again, this post assumes, that flocculation and filtering are set optimally and work. The hints, which the Federal Environmental Agency in the notice: "Hygiene requirements for pools and monitoring" 2014 is about the quality of filtering given, we had in a previous text in the October 2016 implemented.