| Summary: | 碩士 === 逢甲大學 === 環境工程與科學所 === 90 === This work mainly focused on the study of the effects of the sludge floc strength (FS) on the expression dewatering process. The anaerobic-digested sludge was used as the test sludge and dewatered by the expression process with the pressure of 150, 350, 550 and 800 psi individually. Couette Flocculator was applied as the mixer for sludge conditioned with polymer and then performed the breaking test for measuring the floc strength (FS) of conditioned sludge. The experimental results showed that FS of test sludge increased with the addition of polymer. For the filtration stage of expression, both the SRF (Specific Resistance to Filtration) and FT（Filtration Time）of the conditioned sludge apparently decreased with the increase of FS. Increasing the expression pressure did not enhance any improvement on FT and SRF when FS was increased to 3.85. As the FS further up to 4.25, the lowest SRF was all produced within the four expression pressures used. To the consolidation stage of expression, the particle creeping factor (η) and the dewatering efficiency of consolidation both increased with the FS and both reached the maximum value while FS increased to 4.25. Further, the fraction of moisture removed by the secondary consolidation (B) decreased with the increase of FS when the FS under 3.57 and then presented an insignificant variation while FS up to 3.57. The creeping behavior degree of particles is thought to be the dominant mechanism of secondary consolidation according to the determination of maximumηvalue but not lowest B value, which result in the occurrence of the optimal dewatering efficiency. By the way, for the over-all parameters, the increasing FS can promote the whole-stage dewatering efficiency and reduce the moisture content of filtered cake, consolidated cake and the bound water content. However, there were tiny advance on these three parameters while the FS reached up to 3.85. Furthermore, for the effect of expression pressure, 550 psi can greatly improve the whole-stage dewatering efficiency for any condition of FS. Further pressure did not provide improvement anymore.
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