Stability of nitrifying granules exposed to water flux through a coarse pore mesh.

The study of the strength and stability of aerobic granules is essential for the application of aerobic granular sludge membrane bioreactors (AGMBR). In this study, a coarse pore nylon mesh membrane was used to study the differences in compressibility and breakage of 78 aerobic granules submitted to different water fluxes. Confocal laser scanning microscopy was employed to investigate the distribution of extracellular polymeric substances of cryosectioned granules. The tested granules were able to withstand fluxes much higher than those typically applied in MBRs, with pressures ranging from 0.2 to 4.5 kN m-2 before breakage. Cells, β-polysaccharides and proteins were present in higher abundance in the outer layers, while calcium ions were abundant in the outer- as well as the inner layers of the granule. The results shows that the use of coarse pore meshes operated at very high flux is a feasible technique for biomass separation in AGMBR.