An Investigation for the Key Role of Surfactants in Activated Sludge Dewatering

摘要

In this research, compared with common chemical extractants, the efficacies of extractingextracellular polymeric substances (EPS) from activated sludge using cetyltrimethyl ammoniumbromide (CTAB) and sodium dodecyl sulfate (SDS) were studied. The results indicated that bothCTAB and SDS had good extraction ability, and at the dosage of 0.2 g/g DS (dry solid), the amounts ofthe extracted EPS were 154.7 mg/g VSS and 77.6 mg/g VSS, respectively. SDS extracted EPS by itssolubilization property, while CTAB extracted EPS by the synergistic effect of solubilization property,replacement of metal cation from activated sludge and release of intracellular materials. Thedewatering performances of activated sludge conditioned with CTAB and SDS were also investigated.Capillary suction time (CST), water content in sludge cake and bound water were used to evaluate thesludge dewatering behaviours. The results showed that, compared with commercial cationicpolyelectrolyte, CPAM, CTAB and SDS could significantly reduce the water content in sludge cakeand bound water. However, SDS did not help in improving the filtration performance in the wholedosage range. For CTAB, only when the dosage was above 0.1 g/g DS, the filtration rate increased dueto the reaggregation of dispersed sludge flocs. The dewatering performances of activated sludgeconditioned with CTAB and SDS were dependent on detaching and dissolving of EPS from activatedsludge, which resulted in the changes in sludge floc structure.