Dissolved Air Flotation to Control Phosphorus Release of Benthic Sediment in a Coastal Brackish Lake

When applying the flotation process for phosphorus (P) removal in a lake, it is important to separate as much P as possible from water bodies and sediments using microbubbles. Furthermore, for removing P from the sediment, it is crucial to effectively remove readily releasable P that affects the growth of phytoplankton among various P forms. To find out the characteristics and behavior of various P forms in flotation, a series of experiments was carried out to classify and analyze various P types. This article explores how effectively the readily released P forms are separated from other P forms among various P forms in controlling P release from benthic sediment using the flotation separation process. Laboratory-scale dissolved air flotation (DAF) experiments were conducted to remove P from the water body and sediments collected from four brackish Saemangeum Lake sites. DAF could be applied owing to the improved P species composition (mobile P decrease), despite insufficient P removal efficiency in some areas. Moreover, to the best of our knowledge, this study is the first to apply DAF for the treatment of mobile P in sediments; further, the applicability of this process based on the P fractionation method is demonstrated. The findings of this study suggest that DAF removes mobile P contained in sediments more efficiently than immobile P and decreases the content of readily releasable P contained in some of the sediment particles that did not float and settle at the bottom.