EXPRESSION DEWATERING OF MIXED SLUDGES

Filtration followed by expression characteristics of mixtures of clay and activated sludge are first reported in this study. Experimental re sults indicate that the average specific resistance of the mixed sludg e exhibits an ideal-solution like behavior, that is, a linear combinat ion of pure clay and activated sludges with the weight percentage as a parameter. In expression stage, nevertheless, the influence is highly nonlinear. The presence of a little amount of activated sludge can si gnificantly increase both the expression creep effect and the portion of secondary consolidation. The consolidation stage data are interpret ed by the Terzaghi-Voigt combined model, from which the model paramete rs are evaluated accordingly. As the activated sludge is added, both t he difficulty of creeping of constituting particles within the sludge cake and the fraction of moisture attributed to the secondary consolid ation increases rapidly, revealing a highly nonlinear characteristics. The dewatering efficiency of mixed sludge is discussed.