Due to their high nitrogen content, fertilizers and liquid slurry produced in agriculture pose a major challenge in terms of handling in wastewater treatment systems. As part of the VerMiKlär research project (Z.I.M, FKZ: 16KN103924), the treatment process for cleaning heavily polluted agricultural wastewater is being optimized with regard to the degradation of nitrogen compounds (oxidation of nitrite to nitrate). To achieve this, biocomposite fibers are being developed that consist of a core filled with microorganisms (nitrifiers) and a polymer shell. The nitrifiers therefore have a protected, low-flow habitat within the fiber, which gives them a growth advantage compared to the habitat outside the fiber due to their low growth rate compared with other microorganisms. A suspension is being developed for the core component, in which which the microorganisms can grow. The core component therefore provides an environment in which the microorganisms can survive, break down nitrogen compounds and can be processable in the melt spinning process. The developed bioactive fibers are further processed into textiles by embroidering the fibers onto a carrier material using the Tailored Fiber Placement process. The result is a module for wastewater treatment that is optimized with regard to the second step of nitrification process and whose degradation performance is tested and optimized on a laboratory scale and in a pilot treatment system.