Sometimes the traditional settlement clarification after the bioreactors can be quite difficult and unstable. The reason for this varies and could be due to the particularly ‘light’ biomass, de-nitrification in the secondary clarifiers, sludge bulking or a host of other reasons. Dissolved air flotation is a good alternative to sedimentation in these cases. It allows the use of significantly higher biomass concentration in the bioreactors saving construction costs, area and, therefore, space. Excess biomass is also removed in the form of sludge in the biological treatment stage to allow further biomass growth. The thickening of this sludge before de-watering is another common application for DAF technology. KWI has several types of DAF clarifiers used successfully for biological sludge clarification and thickening applications.