Single-channel pump is a type of centrifugal pump that is frequently utilized for wastewater treatment around the world, but they often operate at low flow rates with low efficiency and loud noise because the wastewater contains many impurities. In this study, an adjustable tongue vane was developed that controls the internal flow direction in the volute to increase the energy performance of a single-channel pump. Numerical simulations were conducted by using Reynolds-averaged Navier-Stokes equations and shear stress transport turbulence model to evaluate the energy loss inside the volute. In the experiment, the single-channel pump demonstrated stable operation in the waste environment. In the numerical simulation, the