For certain applications, a biological treatment known as SBR (Sequencing Batch Reactor) may be proposed. it consists in a variant of the standard activated sludge system.

In this configuration, the biological activation and the liquid/solid separation take place in the same basin. This function in a cycle alternated with periods when it is aerated and serves as a biological reactor, and other periods during which the aeration is halted, thereby permitting decantation.