A demonstration scaling-up of the dissolved air flotation

Abstract

Dissolved air flotation (DAF) is currently being received in much attention as an effective process for solid-liquid separation in water technology. In this study, we scaled-up the DAF plant from a pilot-scale (72 m3/day) to a full-scale (6000 m3/day) plant and the sand-float type DAF was used. The concept of maintaining equal surface loading rate into scaling-up of DAF was a proper practice and strategy. In order to optimize the DAF plant, it was needed to determine the surface loading rate and air dissolving tube pressure. The optimum conditions of surface loading rate and air dissolving tube pressure were indicated in 7.5 m3/m2 day and 440 kPa from the pilot plant, respectively. The removal efficiency for TOC and UV254 from the full-scale plant was as satisfactory as those from the pilot plant for the same surface loading rates. However, especially in flotation zone, the full-scale plant performed a little bit poorer than the pilot-scale plant in turbidity and chlorophyll-a reduction: because full-scale plant had long retention time and turbulent mixing condition during backwashing time which might be brought about the breakage of fragile flocs. Performance comparisons between the full-scale DAF plant and the conventional plant located at the city of Nam-Yang Ju in Korea are presented. DAF process showed higher efficiency than the conventional settling system improving the water quality in general, namely, turbidity, TOC, UV254, Fe and Mn. We, therefore, conclude that DAF system should have substantial advantages over the conventional settling process in drinking water treatment.