In the S::Select®-process, the activated sludge is selectively enriched, i.e. Fast-growing bacteria are preferentially reduced while slow-growing bacteria (e.g., nitrifying bacteria) are preferentially enriched. The selection is performed on the basis of density differences by means of a selector, in which a number of hydro-cyclones are combined.
The results are
• A significantly higher specific gravity of the sludge
• An aerobic granular activated sludge
• Much better sludge settling properties
• A significantly higher proportion of nitrifying bacteria
• High process stability


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