Filtration characterisation and specific surface area measurement of activated sludge by Rhodamine B adsorption

Rhodamine B adsorption was used to measure the specific surface area of activated sludge. The surface area occupied by the Rhodamine B molecule was calibrated by measuring its adsorption onto polyvinyl chloride (PVC) granules. The area occupied was found to be dependent on pH and conductivity of the solution. To verify the measurements other uniform materials were used. The surface area of wood flour and an activated carbon were measured with satisfactory results. Micropores (<2 nm) are excluded from the determination. As a representation of a uniform biological suspension yeast was used. The surface area measured by Rhodamine B was compared with a surface area calculated from a number based size distribution. The results showed that it was possible to measure the specific surface area of a biological material with the method described. The specific surface area of activated sludge and specific resistance to filtration was measured as a function of anaerobic storage time, and were found to increase during anaerobic storage. Visual observations attributed the increase of specific resistance to the development of the sludge flocs into smaller structures.