| US 7,481,933 B2 | ||
| Process to improve the efficiency of a membrane filter activated sludge system | ||
| Dennis J. Barnes, Oconomowoc, Wis. (US) | ||
| Assigned to Siemens Water Technologies Corporation, Lowell, Mass. (US) | ||
| Filed on Apr. 11, 2006, as Appl. No. 11/279,354. | ||
| Prior Publication US 2007/0235386 A1, Oct. 11, 2007 | ||
| Int. Cl. C02F 3/30 (2006.01) | ||
| U.S. Cl. 210—605 [210/610; 210/623; 210/903; 210/906] | 20 Claims |
| 1. A process for treating BOD, nitrogen and phosphorus containing wastewater, the process comprising:
providing wastewater influent into an anaerobic zone having activated sludge;
mixing the wastewater influent with the activated sludge in the anaerobic zone to form a first mixed liquor;
providing the first mixed liquor into an oxygen-deficit aeration zone;
mixing the first mixed liquor with activated sludge in the oxygen-deficit aeration zone to form a denitrified mixed liquor;
recycling a portion of the denitrified mixed liquor from the oxygen-deficit aeration zone to the anaerobic zone for mixing
therein with the wastewater influent;
transferring the denitrified mixed liquor from the oxygen-deficit aeration zone to an oxygen-surplus aeration zone;
mixing the denitrified mixed liquor with activated sludge in the oxygen-surplus aeration zone to form a third mixed liquor;
transferring a portion of the third mixed liquor from the oxygen-surplus aeration zone to a membrane bioreactor wherein a
filtrate is separated from a sludge;
providing oxygen to the membrane bioreactor;
introducing oxygen provided to the membrane bioreactor into the sludge to form an activated sludge with a dissolved oxygen
level of between about 4 mg/L and about 8 mg/L; and
recycling at least a portion of the activated sludge to the oxygen-deficit aeration zone.
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