Measurement of bubble bed depth in dissolved air flotation using a particle counter

In the development of dissolved air flotation (DAF) technology, it is noteworthy that higher hydraulic loading rates are achieved while the reactors become deeper resulting in a smaller footprint. One of the reasons for the increased efficiency is claimed to be the deeper bubble bed depth in the flotation separation zone; however, there has been limited research on the characterization of the bubble bed. In this research, a method for locating the bubble bed interface using a commercially available particle counter is presented. The results compared remarkably well with observations by the naked eye at a pilot plant with a transparent acrylic wall. The method is then applied to locate the bubble bed interface at an operating DAF plant in Wonju, Korea. We can observe that the bubble bed profile changes according to the operational conditions and that higher effluent water quality is obtained with a deeper bubble bed. Based on these results, optimization of DAF process might be possible by monitoring the bubble bed profile in the reactor.