Quantification of Floc Growth for Sediment with Mixing Intensity

Abstract

Pollutants related to water quality often exist in rivers and form clusters. These pollutants adversely affect river environments and ecosystems. In Korea, the public’s interest in water quality has been increasing for decades. Many studies on water quality and pollutants in sewage treatment plants have been conducted; however, studies on the formation of flocs based on the flow characteristics of rivers are insufficient. In general, it is known that floc formation is influenced by hydraulic characteristics, such as velocity and turbulence, and that it combines them with contaminants in the river. However, studies that quantitatively analyze this topic are also insufficient. An analysis of floc formation between sediments must be conducted to understand the formation process of sediments and contaminants. Therefore, in this study, kaolin, which is a cohesive sediment, was used to quantify the floc formation process according to the mixing intensity. Turbidity was analyzed to observe the amount of floc formation, and samples were collected to confirm the concentration. Additionally, the turbidity concentration relationship according to the mixing intensity was quantified using an optical microscope. Regarding the mixing intensity, when the rotation speed was 200 rpm or more, the separation of the flocs was dominant. In contrast, when the rotation speed was 100 rpm or less, turbidity changes due to sedimentation and floc formation were dominant. Analyzing mixing intensities and their association with the flow characteristics of rivers may be useful for the management of contaminants in rivers.