Study On The Method Of Floc Strength Evaluation And Characteristics Of Al-Humic Floc Strength

Floc strength which was one of physical characteristics of floc,was an important parameter in water treatment solid-liquid separation.It was very important for the enhancement of solid-liquid separation effect and the alleviation of subsequent treatment process load.This paper based on the theoretical analysis and calculation which was finaced by State Natural Science Foundation(Granted Number:50708088) established the analysis method of floc strength and studied on floc strength of humic under different chemical conditions in shearing force field systemically by means of iconology morphological analysis of floc,dynamic distribution characteristic of floc diameter,optical on-line monitoring of formation and fragmentation of floc.The results showed that,the binding force of floc was constant under special chemical reaction.If enternal force which floc beared was more than the binding force, floc would brake.The experimental analysis system of floc strength was established. Formed floc was introduced into flow field in which shearing force could be changed, the critical condition of flow breakage was determined by means of the change of flow velocity and on-line monitoring of floc in flow field by optical monitoring system.So floc strength was calculated under special chemical condition.Theoretically,the binding force of a floc can be expressed as B=k₁d^2D_f/3,where k₁ is a coefficient of floc binding force,d is average floc diameter of floc,D_f is the fractal dimension of the floc,d and D_f could be measured by image analysis,k₁ could be measured by the critical condition of floc breakage.Floc strength characteristic of humic was studied by means of the establishment of floc strength analysis method,that was proved to be feasible and practical.The results showed that,structure of floc which had high anti-shearing force was compacting based on the mechanism of adsorption and charge neutralization and complexing coordination.However,the structure of floc which had low strength was loose based on the mechanism of sweep coagulation.The results also showed that,the structure and strength of floe based on the mechanism of adsorption and charge neutralization and complexing coordination had little change by means of coagulation aid of PAM,which made the structure and strength of floc based on the mechanism of sweep coagulation have large change.