Particle size reduction by breakage in biological wastewater treatment.

Floc breakup in biological wastewater treatment occurs in response to hydrodynamic stresses imposed by aeration, recirculation, and mixing. This size reduction is of particular concern because it leads to solids carry-over and adversely affects process controllability. A laboratory study of floc size reduction has shown how the hydrodynamic environment causes breakup and the extent to which it proceeds at particular levels of dissipation. The structure of jet flows was found to be well-suited for the reduction of floc size.