METHOD FOR THE TREATMENT OF WASTEWATER CONTAINING AMMONIA

1 - 4 . (canceled)

5 . A method for treating wastewater containing ammonium in a de-ammonifying activated-sludge system, the method comprising:

converting a portion of the ammonium into nitrite using aerobically oxidizing bacteria;

converting another portion of the ammonium and the nitrite into elementary nitrogen using anaerobically oxidizing bacteria so as to generate a surplus sludge;

removing the surplus sludge from the waste water; and

separating the surplus sludge into a heavy phase including primarily anaerobic ammonium-oxidizing bacteria and a light phase, wherein the heavy phase is at least one of collected and returned to the system.

6 . The method recited in claim 5 , wherein the anaerobically oxidizing bacteria includes Planctomycetes.

7 . The method as recited in claim 5 , wherein the separating the surplus sludge into the heavy phase and the light phase is performed using a hydrocyclone.

8 . The method as recited in claim 5 , wherein the separating the surplus sludge into the heavy phase and the light phase is performed using a centrifuge

9 . The method as recited in claim 5 , wherein the separating the surplus sludge into the heavy phase and the light phase occurs by sedimentation.

10 . The method as recited in claim 6 , wherein the separating the surplus sludge into the heavy phase and the light phase is performed using a hydrocyclone.

11 . The method as recited in claim 6 , wherein the separating the surplus sludge into the heavy phase and the light phase is performed using a centrifuge

12 . The method as recited in claim 6 , wherein the separating the surplus sludge into the heavy phase and the light phase occurs by sedimentation.