1. (a) Duplicate gravity thickeners shall be provided to allow the thickening process to continue without disruption with one unit out of service.
2. (b) Mechanical picket arms shall be provided.

3. (c) The drive mechanism shall have:

   1. (1) Sufficient torque capacity to handle the maximum sludge concentration and blanket thickness anticipated; and
   2. (2) A high torque alarm and overload device.
4. (d) An odor control system shall be provided. Elutriation water may be used for this purpose only in conjunction with additional odor control measures.
5. (e) Metallic components of gravity thickeners shall be corrosion resistant.

6. (f) Gravity thickeners shall be designed on the basis of the following:

   1. (1) Primary sludge solids loading of 20 to 30 pounds/day/square foot; and
   2. (2) Combined primary and waste activated sludge loading of 5 to 14 pounds/day/square foot.

Source. (See Revision Note at chapter heading for Env-Wq 700) #8590, eff 3-25-06; ss by #10693, eff 10-15-14; ss by #14258, eff 7-1-25, EXPIRES: 7-1-35