Comparative sedimentation characteristics of suspended solids and phosphorus particles in discrete and flocculent sedimentation to treat influent of lake

In order to understand the phosphorus (P) removal characteristics, which is the main controlling factor of eutrophication and algal blooms in a lake, the particle size distribution (PSD) and behavior were investigated in the inflow water and trapped sediments of Lake Saemangeum. A series of settling column tests (SCT) was carried out on the raw water taken from two influents of the lake to evaluate the sedimentation efficiency and P removal using two types of settling tests, discrete particle sedimentation (DPS) and flocculent particle sedimentation (FPS). In particular, the variation in the PSD and the P removal efficiency was traced to determine the impact of rain on the P treatment characteristics for three periods: the summer rainy period and before and after the rainy season. The PSD of the trapped sediments had increased in the rainy season, with a decrease after the rainy season. Based on the SCT results of the suspended solids, a longer sedimentation time for the DPS in the dry season was required than in the rainy season, whereas the sedimentation times for the FPS were not much different for the three periods. However, the clarifying velocity of the total phosphorus concentration was slower than the suspended solid concentration for both DPS and FPS, which suggest the particles containing phosphorus settled much more slowly than typical particles in both tests. The findings of this study will be important information in determining whether to add a coagulation process in the design of a sedimentation basin for the removal of phosphorus to be constructed for eutrophication and removal of lakes.