A mobile root-zone wastewater treatment system with a reaction zone consisting solely of reed roots as the growth surface for microorganisms was tested for temporary applications in the treatment of municipal wastewater. Pretreated municipal wastewater from a large-scale wastewater treatment plant was fed to this system during the 2016 vegetation period. The outlet limit values for chemical oxygen demand and biochemical oxygen demand were adhered to reliably at an inlet volumetric flow rate of 1200Ld(-1). Short-term loading peaks of up to 1800Ld(-1) did not lead to overloading of the system.