Dissolved air flotation: progress and prospects for drinking water treatment

The development of dissolved air flotation (DAF) for drinking water treatment has come a long way. After its pioneering application to water treatment in the 1920s, it was seemingly forgotten until renewed interest in the 1960s in Sweden, Finland, southern Africa and the United Kingdom brought it to attention once more. These advances converged at the first DAF conference in 1976 to unify the international DAF agenda. Subsequent meetings in 1991 (Antwerp), 1994 (Orlando), 1997 (London) and 2000 (Helsinki) provided important milestones for benchmarking the evolution and acceptance of DAF as a viable drinking water treatment process. The versatility of the process spawned a wide range of innovations to increase its efficiency, to optimise its energy use, to reduce its footprint and capital cost, to integrate it with filtration, sedimentation and ozonation, and more recently to use it in conjunction with membrane treatment. Although DAF innovation continues unabated, for example to improve hydraulic flow patterns and to produce bubble suspensions with more precise size and charge distribution, the process has now clearly crossed the chasm between the experimental (the “early adopters” phase) and maturity (the “early majority” phase).