Experimental Study On The Effect Of Organic Matter On The Flocculation Of Cohesive Sediment And Interaction Force Between Particles

A large amount of organic matter is contained in the water environment of the estuarine and coasts.Most of the cohesive sediment covered by the organic coating composed of humic acid substances and biofilms which can change the surface physical and chemical characteristics of the sediment particles.Therefore,the influence of organic matter on the flocculation process cannot be ignored.This article carried out two part experiments which focus on the impact of organic matter on the flocculation and settling velocity of cohesive sediments and the interaction force between particles covered by the organic coating.The main conclusions are as follows:(1)The settling experiment of Kaolinite in the quiescent water under the various salinity and organic matter conditions were conducted in the settling column.It can be concluded that the settling velocity decreased with the increase of organic matter content when at the fresh water or the saline water with the relative high(5 ppt)salinity.When at the low salinity(1 ppt),the settling velocity increased first and then decreased,and the settling velocity reached the peak value when the organic matter content was 30 mg/L.An empirical formula of settling velocity considering organic matter and salinity is proposed by fitting the experimental results.(2)An experiment on the cultivation of organic coating on the polystyrene latex particles in water with different organic matter contents was carried out.With increasing of organic matter content in water,the latex particle size first increased and then decreased.(3)The interaction force between the latex particle and organism-covered particle was measured by the atomic force microscopy(AFM).Compared with the XDLVO theory,the repulsive force between particles considering the effects of organic matter is larger than that of the XDLVO force.With the increase of the organic matter content,the Van der waals attraction force between the latex particle and organism-covered particle gradually decreased and the repulsive force increased.(4)According to the experimental results of the interaction force between particles,the regression analysis based on the XDLVO theoretical formula for salinities of 200 mmol/L and 300 mmol/L was carried out.Considering the effects of organic matter,a formula of the inter-particle forces is obtained.