Abstract: The efficiency of mud flocculation settling is an important factor affecting the dredging progress in lakes or reservoirs. To explore the effect of different flocculants (organic and inorganic) on the settling efficiency of dredged mud, we compared the flocculation settling efficiency and supernate quality of dredged mud treated by organic flocculant (PAM) and five inorganic flocculants(PAC,FeCl₃,Na₂CO₃,Na₂SiO₃·9H₂O, and KAl(SO₄)₂·12H₂O), respectively. Furthermore we conducted optimization test on the combination of flocculants to achieve an optimum settling efficiency and supernate water quality. Through the indoor tests we conclude that PAM could effectively promote the flocculation settling of dredged mud soil particles, but the efficiency of reducing turbidity is low; CO₃^2- could also improve the efficiency of flocculation settling by gathering fine particles into large particles; Fe³⁺ and Al³⁺could reduce the turbidity of supernate, but has limited effect in enhancing flocculation settling. The optimum combination of flocculants is 10 ml PAM+2gPAC+2gNa₂CO₃ in every 1 000 ml dredged mud, which could both accelerate the settling of dredged mud and reduce the turbidity of supernate effectively.

Key words: dredged sediment, chemical flocculant, flocculation-settling, supernate, moisture content, turbidity-reducing rate