Stroboscopic determination of settling velocity, size and porosity of activated sludge flocs

Abstract

A multi-exposure photographic method was developed for the combined measurement of the settling velocity and size of activated sludge flocs. The proposed method mainly differs from the previous stroboscopic tests by introducing a new experimental arrangement which ensures sharp images of flocs on photographs. The relationships between individual floc-settling velocity and the floc size were found to be linear or fractional power functions. All these relationships were well correlated. Based on a simplified floc structure assumption and results of experimental measurements of floc-settling velocity and size, the floc porosity was determined. The porosity increased at two distinct rates as the floc size increased.