In this work, a dynamical Sliding Mode Control (SMC) is computed for a wastewater treatment bioprocess taking place inside a Sequencing Batch Reactor (SBR). The controller is obtained using generalized observability canonical forms and SMC stabilization. More precisely, the control law design is done by means of combination between exactly linearization ideas and SMC. The control goal is to keep a low level of pollutant concentration. Numerical simulations are included to test the performances of the proposed control strategy.