Effects Of Titanium Salt/Titanium Salt Comband Chemical Conditioning On The Physical And Chemical Properties Of Activated Sludge Flocs

With the rapid development of economy, the remaining amount of sludge in the rapid growth during the process of the wastewater treatment.In addition, moisture content and volume of sludge is very high, so reducing the moisture content and volume of sludge has become an urgent problem now. Development of high-performance dewatering process is becoming a hot issue in the field of environmental engineering in China.In this paper, the effect of prepared different forms coagulants chemical conditioning on sludge dewatering performance has been studied. The physical and chemical properties of activated fludge flocs during conditioning have been analyzed. The distribution and composition of the sludge extracellular polymeric substance（EPS） have been characterized by Three-dimensional Excitation Emission Matrix Fluorescence（3DEEM） and High Performance Size Exclusion Chromatography（HPSEC）. Main contents and results of this dissertation are as follows:1. Peracetic acid（PAA） and Fe²⁺ have been used to improve the filtration dewatering and drying efficiency of activated sludge. The specific resistance to filtration（SRF）, cake moisture content and particle size distribution were determined for understanding the underlying mechanism of combined conditioning process. The results showed that sludge p H was reduced to 2.5⁴ after addition of peracetic acid. A further addition of Fe²⁺ resulted in the formation of formed Fenton oxidation system. Thus, sludge was effectively solubilized and protein and polysaccharide of EPS were significantly destroyed under combined the conditioning process, consequently leading to release of bound water. Sludge dewaterability reached the maximum when the molar ratio of Fe²⁺ and H₂O₂ in PAA and PAA dosage were 2:1 and 0.1g/g TSS. Finally, when the sludge system was readjusted to neutral, the further improvement of sludge dewatering performance was observed due coagulation process of in-situ production ferric ions.2. The effect of prepared different forms titanium salt coagulant conditioning on sludge dewatering performance has been studied. The result showed that the sludge dewaterability was the best and the specific resistance to filtration（SRF）, compressibility and the content of organic content in EPS was the lowest when PTC0.5compared with others. The optimum dosage of polymeric titanium chloride（PTC） was 0.005g/g TSS, which was far less than the traditional iron salts and aluminum coagulants. When the dosage of PTC with different B value were 0.005 g/g TSS,theorder of dewaterability was:PTC0.5>PTC1.5>Ti Cl4> PTC2.5. In addition, the variation of characteristics such as particle size（d0.5μm）and fractal dimension（DF） of sludg during conditioning have been analyzed. The effect of titanium salt coagulant conditioning on the distribution and composition of the sludge extracellular polymeric substance（EPS） has been characterized by 3D-EEM and HPSEC.3. The influence of nano Fe₂O₃+PTC and PTC+PAM combined conditioning on the sludge dewatering performance has been investigated. The variation characteristics of particle size of sludge（d0.5μm） and fractal dimension（DF） during conditioning have been analyzed. In addition,the effect of nano Fe₂O₃+PTC combined conditioning on composition and distribution of the sludge EPS has been characterized by by 3D-EEM and HPSEC. The results showed that when the dosage of Fe₂O₃ and PAM was 0.03g/g TSS and 0.005（V/V） respectively,sludge dewaterability reached the maximum.