Abstract:The properties of flocs were analysed by microphotography and auto image analysis technique, and the sedimentation of flocculated or coagulated suspension and water osmosis in sediment were studied. It was found that, the flocs size is related to the average diameter of fine solid particles, the locus of the compressive points of the sedimentation curves of flocculated suspensions is a straight line approximately, the water permeating of sediment is unsteady and water osmosis rate reduces with extension of sedimentation time, the sediment resistance to fluid flow is the main factor that affects the average sedimental concentration.

Key words: flocculation　coagulation　floc　sedimentation of suspension