The effect of the different forms of titanium salt coagulant conditioning on sludge dewatering performance was studied. The result showed that the sludge dewaterability was the best and the specific resistance to filtration (SRF), the compressibility and the content of organic content in EPS were the lowest when B=0.5 compared with others. The optimal dosage of polymeric titanium chloride (PTC) was 0.005 g·g-1, which was far less than those of the traditional iron salts and aluminum coagulants. When the dosage of PTC with different B values was 0.005 g·g-1, the order of dewaterability was:PTC 0.5> PTC1.5> TiCl4> PTC2.5. In addition, the variations of characteristics such as particle size (d0.5) and fractal dimension(DF) of sludge during conditioning were analyzed. The effect of titanium salt coagulant conditioning on the distribution and composition of the sludge extracellular polymeric substance(EPS) was characterized by Three-dimensional Excitation Emission Matrix Fluorescence (3DEEM) and High Performance Size Exclusion Chromatography(HPSEC).The decrease of fluorescent intensity and molecular weight of peak distribution and intensity of organics in EPS was highly correlated to the improvement of the dewatering performance and change of sludge properties.
Keywords: 3D-EEM; dewaterability; polymeric titanium chloride; sludge; titanium tetrachloride.