Since conventional technologies (sedimentation) are no longer sufficient to increase the biomass concentration, mikro- or ultrafiltration is used. In this way not only the volume of the biological stage decreases by increasing the biomass in the reactor, but also the total capacity of the plant is reduced. In addition, the membrane forms a safe barrier against virus and bacteria. Thus the membrane serves to improve the effluent quality.

The settling tank in traditional WWT plants is designed for an overflow rate of 1-2 m/h. This may, however, be considerably increased by the use of polymers as flocculants. Flocculants are expensive and toxic. Therefore the use should be minimized. Low pressure DAF are designed for much higher overflow rates (5-15 m/h) hence the footprint is very small. Flotations give a better separation result because since smaller particles can be removed. The flotate concentration is 30 to 60 g/l and so the sludge thickening system is already included. There is a very positive impact on the aquatic environment because the effluent of DAF systems is saturated with air. Many Low Pressure DAF systems work with good results over years without any flocculants. The energy demand is between 0,2 to 0,4 kW per m^3 treated water.