Impacts of flocculation conditioning on dewaterability and physicochemical properties of anaerobic digested sludge(ADS) flocs
Menglong Yang · Acta Scientiae Circumstantiae · 2011
The effect of different doses of cationic polyacrylamide(CPAM) on anaerobic digested sludge(ADS) conditioning was studied.The results showed that flocculation conditioning could highly improve the dewaterability of the ADS.The capillary suction time(CST) values decreased from(193.6±0.00) s for original ADS to(5.75±0.21) s for conditioned ADS at the optimal dosage,and the corresponding supernatant viscosity after centrifugation also decreased from(1.47±0.00) mPa · s to(1.14±0.00) mPa · s.In addition,both the zeta potential and surface charge density for colloids in the centrifugal supernatant reached about zero value at the optimum polymer dosage.With the increase of polymer dosage,the ADS flocs became larger,and both their median diameter and volume average diameter were 1.17 mm and 1.99 mm at the optimal dosage.The corresponding average sizes for the original ADS biosolids were 0.13 mm and 0.25 mm,respectively.The one-dimensional fractal dimension(D1) and two-dimensional fractal dimension(D2) for ADS biosolids fluctuated as the polymer dose increased,but both of them arrived at maximum values,D1=1.19,D2=1.41,at the optimal polymer dosage which meant that the flocs formed at this dosage had the coarsest surface and most compact structure.In addition,the flocs with high strength and erosion-resistance were also observed in the optimum polymer dose range.And TG-DSC analysis for these biosolids indicated the bound water evaporated in the range of 30~150℃.