Floc structure and the role of cations.
ABSTRACT Cations have been found to influence the settling and dewatering characteristics of biological sludges. This research was directed at investigating the role of iron in floc stability of sensitivity to shear and in the response to anaerobic and aerobic digestion. Our data shows that iron may contribute to floc strength and it appears that the deterioration in sludge dewatering during anaerobic digestion is associated with the reduction and solubilization of iron. Further, it is the presence of proteins in solution that contributes to poor dewatering and to the demand for conditioning chemicals. The addition of iron for improving dewatering shows that iron may selectively coagulate solution proteins.