| In this thesis, five kinds of sludge collected from different sources were conditioned chemically by dosing polyaluminium chloride (PAC), polymeric ferric sulfate (PFS), chitosan (CTS) and rectorite. The optimal dosages of those materials were obtained based on the measurement of specific resistance to filtration (SRF). A composite coagulant was developed and its optimal ratio of components was also determined. The effects of the bound water and Zeta potential(ZP) of sludge on SRF were discussed and the relation between the polysaccharide and protein contents in extra-cellular polymeric substance (EPS) of sludge and the bound water content and ZP of sludge was also investigated. The results showed that the higher the bound water and the great ZP (absolute value) of sludge, the better the correlation with SRF. The increasing of bound water content and ZP of sludge was unfavorable to the lowering of SRF. However, the bound water content and ZP were also closely correlated with the contents of polysaccharide and protein in EPS of sludge. The increasing of contents of polysaccharide and protein in EPS of sludge would lead to the raising of bound water content and ZP in sludge, which caused the increasing of PAC, PFS and CTS dosages. Compared with protein, the effects of PAC and PFS addition on the variation of polysaccharide content were more remarkable. Nevertheless, compared with polysaccharide, the effect of CTS addition on the variation of protein content was more remarkable. Rectorit has less effect on the bound water and ZP. The variation of SRF was attributed to the structure variation of filter cake after adding the rectorite. The optimal dosage of rectorit was closely correlated with sludge concentration. Finally the components of the composite coagulant were determined as PAC0.044g/gDTs, PFS0.029g/gDTs, CTS0.013g/gDTS, Rectorit0.06g/gDTs, and the variation of sludge properties after adding the composite coagulant was also investigated. |
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