Dissolved Air Flotation (DAF) – Technology
Flotation technology is the best practice for separating specific light weight substances (e.g., oils and fats, turbid and suspended matter, algae) from aqueous solutions. The process in a flotation plant can essentially be subdivided into the following three sections:
Chemical pretreatment by coagulation and flocculation
In the first process step, the medium is pretreated, with the substances to be separated forming into larger aggregates. As a result, the deposition of fine air bubbles is made possible or improved. The selection and dosage of suitable chemicals depends on the process and is, according to the application, crucial for the removal rates of the DAF.
Whitewater production
KWI’s patented technology (Air Dissolving Reactor, ADR), a specially designed reactor, saturates some of the clearwater with air under pressure and then depressurizes it across a valve. Fine air bubbles, so called micro bubbles with a diameter of 40 to 90 micrometers, are formed.
Mixing zone and flotation tank
In the third section, a specific mixing of the whitewater with the medium proceeds, followed by the separation in the flotation tank. The microbubbles dispersed in the whitewater deposit on the particles to be separated. It creates bubble-particle compounds whose resulting density is lower than that of the surrounding medium. As a result, these compounds rise to the surface and form flotation sludge, which is skimmed off via a clearing mechanism. The clearwater leaves the flotation tank through appropriate outlets and is purified for subsequent processes.
