Sludge loss occurs when activated sludge is discharged along with the effluent from the secondary clarifiers. The reason is always insufficient sedimentation in the secondary clarifier. Amongst other things, the cause can be attributed to bulking sludge, scum, poor floc structure, or hydraulic loading. In other words, if the sludge is too light, i.e. settles too slowly, the distance for sedimentation in the final clarification is not sufficient to prevent the sludge from being discharged over the effluent weir. A too high of a hydraulic load has a similar effect, the sludge passes the distance for sedimentation faster than it is settling.
In both cases, an improvement in the sludge structure helps to increase the specific gravity of the sludge and thus provides good settling properties. The aerobic granular activated sludge of S::Select® has a significantly higher specific gravity than normal activated sludge (approx. 1.05 kg/l), therefore sludge loss from the S::Select® process is practically impossible due to the very good settling properties.


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