Abstract: Flocculation-settling property is an important research subject to be improved in the treatment of river and lake dredging silt. The effects of particle size distribution, initial sediment concentration, and high-molecular polymer on flocculation and settling property of dredging silt were examined through settling experiments with the settling velocity of interface between clear and turbid liquid and turbidity of supernatant as indexes. The dredging silts from the Shahu Lake, Nanhu Lake, and Guanqiao Lake in Wuhan were taken as research object. Besides, the influence of settling column size on experiment result was also investigated. Results reveal that the smaller the particle size is, the slower the silt flocculates and settles, and the clearer the supernatant fluid is. The settling velocity decreases with the increase of initial sediment concentration; but the influence of initial sediment concentration weakens when it reaches a threshold value. High-molecular polymer promotes the flocculation-settling property of dredging silt. In addition, the size of settling column has little impact.

Key words: silt in river and lake, flocculation and settling, settling experiment, settling velocity of interface between clear and turbid liquid, turbidity of supernatant