EVALUATION OF AN EJECTOR-BASED AIR SATURATION SYSTEM FOR DISSOLVED AIR FLOTATION
The saturator system is the most cost consuming part in DAF operation and optimization of the used methods is of great economical interest. An ejector-based system for use in a pilot plant was evaluated with novel air collecting methods. Three ejectors with increasing size were examined and a relation between ejector water velocity and a maximum air content was found. It was shown that a velocity of 13 m/s in the ejector was necessary for reaching a maximum air content, measured to be 62 ml/1 for the specific system. An indication of a surplus concentration above saturation of dissolved air in the effluent was discovered, implying that all air was not precipitated when depressurized over the air-injection device. Macro-bubbles were measured as escaped air and it was speculated that the mixing condition inside the contact zone probably was the most significant parameter determining the existence of macro-bubbles.