4. Installation et montage - Kessel

2. General4. Sedimentation phaseThe treatment phase is followed by a 2-hoursedimentation phase. Any solids containedin the sewage as well as the activated sludgesettle on the bottom of the tank and aclear water layer thus forms in the upperarea, while a sludge layer made up ofmicroorganisms forms on the bottom.5. Extracting the clear water(clear water extraction)Clear water now remains above this sludgelayer and is fed via the air syphon for theclear water extraction into the preclarifier orinfiltration plant.6. Repumping the activated sludge(sludge extraction)Excess activated sludge is pumped backinto the preliminary sedimentation.104