Previous studies indicate that advective flow is important and that there is a significant flow through pores. However, some studies indicate that there is a significant bound water component that is an integral part of the floc structure. The EPS is thought to have a high water binding capacity in both flocs and fixed biofilms. Resistance within the floc owing to the complex EPS matrix may affect the flux of water in and out of the floc. Diffusional gradients may also be important in the transport of nutrients, and they may affect the microenvironment.
Recent studies suggest that anoxic microenvironments exist within aerobic activated sludge.
It is likely that both advective flow and diffusion account for transport through the floc as they do in biofilms. The objective of this project is to examine the contribution of diffusion to transport processes within the floc. The work will contribute to increased understanding of microbial floc structure and function. S.N. Liss, I.G. Droppo, D.T. Flannigan, and G.G. Leppard. I.G. Droppo, G.G. Leppard, D.T. Flannigan, and S.N. Liss.