High-rate air flotation

Wang, L.K. and Wang, M.H.S., Decontamination of groundwater and hazardous industrial effluents by high-rate air flotation process, Proc. Great Lakes 1990 Conference, Hazardous Materials Control Research Institute, Silver Springs, MD, September 1990. 

Several high-rate air flotation clarifiers (both DAF and dispersed air flotation) with less than 15 min of detention times have been developed for groundwater decontamination, industrial effluent treatment, resources recovery, and water reclamation. Both insoluble and soluble impurities such as... 

A description is given of a unique solution for the problems of overloaded conventional activated sludge systems. A high-rate dissolved air flotation (DAF) clarifier is applied in series between the... 

A relatively new design of a high-rate DAF unit uses a shallow bed system (Supracell) with only 3 minutes of retention time and operated at an overflow rate of 140Lpm/sqm (3.5 gpm/sq ft) [42]. This unit has been used for industrial and municipal wastewater treatment and offers lower capital cost and headroom requirements. It was installed at a petrochemical complex in Texas as a secondary clarifier to improve the operation and the capacity of an existing activated sludge system [43]. In recent years, nitrogen has replaced air in covered DAF systems because of the potential for explosion. These systems are called dissolved nitrogen flotation (DNF) systems. The operations of DAF and DNF are similar. 

H. J. Kiuru, Development of dissolved air flotation technology from the 1st generation to the newest or 3rd one (very thick microbubbles) with high flow-rates (DAF in turbulent flow conditions). Water Sci. Technol. 8, 1-8 (2001). 

Most commercial designs of dissolved air flotation plants for use on aqueous systems are based on an empirical approach by Bratby and Marais [1974 1977], Then-experiments used a pressure saturator in v 4iidi a high air pressure is maintained in a cylindrical pressure vessel by means of a conq>ressor Mst air is continuous recycled through the water by a circulating pump. Water is fed continuoush and the rate controlled to ke a constant level in the vessel. No air is lost firom the systenr... 

Edzwald, J.K., 2007. Developments of high rate dissolved air flotation for drinking water treatment. J. Water Supply Res. Technol. — AQUA 56 (6), 399—409. 

Since a reduction in the bubble spectrum is connected to additional difficulties and polydispersity of bubbles in electroflotation and air-dissolved flotation cannot be therefore avoided, it is important to know the effect of polydispersity. This effect should not be too high since the process of particle capture should be ahead of the process of coalescence. It should also not be too low so large bubbles can capture small bubbles in a moderate time. Unfortunately, such a scheme which appears convincing at a first glance means a slow rate of coalescence of small bubbles. The coalescence can proceed faster than particle capture, so that the intensification of capture becomes very important. Hence it is necessary to combine introduction of small bubbles with aggregation of particles. 

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