Rheological examination of domestic sewage sludge

Abstract

The flow parameters involved in the transportation of sludge from the place of origin to the place of disposal has long been a problem to the sanitary engineer. To obtain the greatest efficiency in the design of pumps and pipelines the properties of sludge need to be thoroughly understood.

This investigation examined the flow characteristic of raw and digested sludge from the Blacksburg Treatment Plant using a rheological approach. A Brookfield viscosimeter was used in the investigation and formulas developed by Krieger and Maron (1) were used to determine the shear stress and velocity gradient. A series of graphs involving shear stress vs velocity gradient were plotted. These graphs were compared to the Standard Newtonian and Non-Newtonian curves, in order to determine the flow behavior of the sludges.

The results showed the method of analysis was satisfactory for determining the flow behavior of sewage sludges. The curves obtained showed that the raw and digested sludge examined was pseudoplastic in behavior and shear stress values for the domestic sludge showed it to be more viscous than the raw sludge.