Influence of floc size on activated sludge volume index

Floc size (AFS) variations in relation to sludge volume index (SVI) were investigated at different intensities of bidirectional changes in organic loading of activated sludge. In the case of rapid increase and subsequent decrease of organic loading, SVI directly depended on AFS. Under the circumstances of relatively slow but long-lasting changes in organic loading, the correlation between AFS and SVI was less distinct. It has been concluded that floc size distribution is one of the most important factors influencing sludge volume index of non-filamentous activated sludge. Considerable, dynamic changes in floc size distribution can disturb the relationship between AFS and SVI.