低温低浊水混凝特性及强化混凝技术市政工程专业论文.docxVIP

哈尔滨工业大学工学硕士学位论文 哈尔滨工业大学工学硕士学位论文 - - PAGE VIII - Abstract Coagulation characteristic in the condition of low temperature and low- turbidity is investigated by means of photometric dispersion analysis (PDA), ferron-Al timed spectrophotometry, and turbidity measurement at different flocculation period. For the low temperature conditions (2oC, 5oC, and 8oC), a linear relationship between aggregation rate of coagulation and particle number concentration within certain limit is observed. Increasing initial turbidity within certain limit (from 3.30 ntu to 9.30 ntu) would increase the aggregation rate linearly. While aggregation rate remains roughly constant when particle number concentration surpasses the limit or initial turbidity increases from 9.30 ntu to 16.50 ntu. However, for the higher temperature condition (ambient temperature: 17-21oC), aggregation rate remains increase in the whole turbidity range (from 3.30 ntu to 16.50 ntu). Furthermore aggregation rate obtained from PDA curves could predict the optimum alum dosage. In addition, mechanism of coagulation under conditions of low temperatures (2℃, 5℃, and 8℃), low turbidities (3.30 ntu, 5.30 ntu, and 9.30 ntu), and a normal pH value of 8.0 is investigated. Result of ferron-Al timed spectrophotometry shows that Al-hydrolyzed species present similar fraction after fast-mixing period in experimental conditions. Concentration of polymeric metal hydrolyzed species of high charge is very similar in different circumstances. Such results indicate that the approach from hydration of ion-based coagulant to polymerization is not significantly affected by temperature and turbidity. However, measured by photometric dispersion analysis (PDA), either higher temperature or larger initial turbidity is able to increase the aggregation rate. Result of PDA indicates that the approach from polymerization of hydrolyzed species of ion-based coagulant to nucleation and crystal growth is greatly influenced by temperature and turbidity an