Removal of Particles from Water Using Dissolved Air Flotation

A new high-rate dissolved air flotation (DAF) tank was developed and the efficiency was studied through pilot experiments. The turbidity of effluent water was improved 30% at hydraulic loading rate of 18 m/h when the perforated pipe was replaced by perforated plate for the collection of effluent water. A separation system made by a series of lamella plates was installed at the middle part of separation zone to change the flow structure to be laminar at high hydraulic loading rate. In comparison to pure perforated plate DAF tank, the turbidity of effluent water was further improved 15%. It was found that the thickness of bubble layer was reduced with the addition of lamella plates, while the three-dimensional disturbances and vortexes were greatly mitigated and the hydraulic form was turned into a steady laminar flow. The experimental results showed that the high-rate DAF tank with perforated plate collection system and lamella plates separation system was able to operate stably at a high-rate of 18 m/h, and the turbidity removal rate was about 95%.