Abstract
The physical characteristics of activated sludge flocs cultured under various operational conditions were investigated using the structure model previously proposed.
Experimental results are summarized as follows :
1) Nitrogen deficiency in fill and draw culture resulted in the increase of loosely microorganisms-occupied flocs and the increase of Sludge Volume Index (SVI). However, the continuance of the fill and draw culture changed the floc structure into densely microorganisms-occupied one and lowered SVI.
2) Phosphorus deficiency in fill and draw culture resulted in the decrease of floc size and floc density, but the remarkable increase of SVI was not observed. The flocs had loosely microorganisms-occupied structure.
3) As substrate loading was increased in fed batch culture, floc size increased by the extreme growth of filamentous microorganisms. The SVI value exceeded 300.
4) As substrate loading was increased in fill and draw culture, flocs were disrupted into small particles. Although the SVI value increased, filamentous microorganisms were not observed.
