Cleartec® BioCurlz used as a completely submerged fixed bed in the biological stage of a wastewater Treatment Plant. The 3-dimensional lace structure provides a growth surface for the active microorganisms without flow restrictions. By using fine bubble aeration for supplying oxygen to the microorganisms a vertical flow be obtained. The thickness of biofilm will be regulated by the velocity of the airstream by removing the old microorganism and forms new active biofilm surfaces. The amount of active microorganisms is comparing with the 47g suspended biomass perm BioCurlz under optimum operating conditions.The activity of microorganisms depends on the sludge age and differs according to the operating conditions of the WWTP. The basis for the installation of Cleartec® BioCurlz is the discharge of domestic water or compared to that at temperatures in the range of +5°C to +36°C (+41°F to + 97°F). The discharge of industrial wastewater has been separately regulated. This also applies to other installations and fields of applications.