Method and installation for treating wastewater containing ammonia

1. A method for treating wastewater containing ammonia in a deammonifying installation including at least one aeration tank, the method comprising:

converting ammonia into nitrite using aerobic oxidizing bacteria (AOB);

converting ammonia and nitrite into elementary nitrogen using anaerobic ammonium-oxidizing bacteria (anammox);

feeding activated sludge, at least at times, from the at least one aeration tank into a hydrocyclone;

separating the sludge in the hydrocyclone into a specifically heavy fraction containing mostly the anaerobic ammonia-oxidizing bacteria (anammox) and a specifically light fraction containing mostly aerobic ammonia-oxidizing bacteria (AOB), wherein during the separating of the activated sludge, the anaerobic ammonium-oxidizing bacteria (anammox), which has a greater density than the aerobic ammonia-oxidizing bacteria (AOB), are deposited onto a roughened inner wall surface of the hydrocyclone as a result of centrifugal and flow forces in the hydrocyclone and exposed to abrasive forces generated due to a relative movement between the anaerobic ammonium-oxidizing bacteria (anammox) and the roughened inner wall surface of the hydrocyclone;

at least partially removing an organic or inorganic cover layer disposed on the anaerobic ammonium-oxidizing bacteria (anammox) as a result of the abrasive forces; and returning the specifically heavy fraction and the specifically light fraction to the at least one aeration tank.

2. The method according to claim 1 , wherein the ammonium-oxidizing bacteria (anammox) includes Planctomycetes granules and the abrasive forces remove the organic or inorganic cover layer from the Planctomycete granules.

3. The method according to claim 1 , wherein the specifically heavy fraction separated in the hydrocyclone and the specifically light fraction of the activated sludge are both returned in their entirety to the at least one aeration tank.

4. The method according to claim 1 , wherein the hydrocyclone includes a conical segment comprising the roughened inner wall surface, wherein, during the separation of the activated sludge in the hydrocyclone, the specifically heavy fraction containing mostly the anaerobic ammonia-oxidizing bacteria makes contact with the roughened inner wall surface and is subsequently discharged from the hydrocyclone through an underflow of the hydrocyclone, while the specifically light fraction containing mostly the aerobic ammonia-oxidizing bacteria (AOB) makes contact with a smooth inner wall surface in a cylindrical segment of the hydrocyclone and is subsequently discharged from the hydrocyclone through an overflow of the hydrocyclone.

5. The method according to claim 1 , wherein, after a first predetermined time period during which activated sludge is fed into the hydrocyclone and separated into a specifically heavy fraction and into a specifically light fraction and during which the heavy fraction as well as the light fraction are returned to the at least one aeration tank, instead of activated sludge, surplus sludge that has been withdrawn from the at least one aeration tank is fed into the hydrocyclone during a second predetermined time period, whereby the surplus sludge is separated in the hydrocyclone into a specifically heavy fraction and into a specifically light fraction, and exclusively the specifically heavy fraction is returned to the at least one aeration tank or else collected and fed into an aeration tank of a second installation, whereas the specifically light fraction is disposed of.

6. The method according to claim 5 , wherein the length of the first predetermined time period is greater than the length of the second predetermined time period.

7. The method according to claim 5 , wherein the length of the first predetermined time period is about 1.5 to 4 times greater than the length of the second predetermined time period.

8. The method according to claim 1 , wherein activated sludge is fed into the hydrocyclone, alternatingly and continuously, during a first predetermined time period, and that surplus sludge is fed in during a second predetermined time period.