The patent badge is an abbreviated version of the USPTO patent document. The patent badge does contain a link to the full patent document.
The patent badge is an abbreviated version of the USPTO patent document. The patent badge covers the following: Patent number, Date patent was issued, Date patent was filed, Title of the patent, Applicant, Inventor, Assignee, Attorney firm, Primary examiner, Assistant examiner, CPCs, and Abstract. The patent badge does contain a link to the full patent document (in Adobe Acrobat format, aka pdf). To download or print any patent click here.
Patent No.:
Date of Patent:
Sep. 11, 1990
Filed:
Jul. 21, 1989
Gilbert V Levin, Annapolis, MD (US);
Ronald R Wright, Parkville, MD (US);
Biospherics Incorporated, Beltsville, MD (US);
Abstract
There is disclosed an activated sludge wastewater treatment process which comprises aerating a mixed liquor comprising phosphate-containing influent wastewater and activated sludge in an aeration or high-purity oxygen zone to reduce the BOD/COD content of the wastewater and to cause the microorganisms present to take up phosphate. A phosphate-enriched sludge in which the phosphorus is present primarily in the sludge solids is separated from the mixed liquor to provide a substantially phosphate-free effluent. At least a portion of said phosphate-enriched sludge is passed to a phosphate pre-stripping zone, either in a separate tank or within the phosphate stripper tank itself, where BOD/COD-containing water, or feedwater, containing at least 50 mg/L of BOD, is added to poise the sludge organisms to begin enhanced rapid release of dissolved phosphate by pre-stripping it from the sludge or poising the sludge for rapid, enhanced release of phosphate. Then, the sludge is passed to a phosphate stripping zone. In the phosphate stripping zone, the sludge settles to form a supernatant liquor in the stripping zone upper section and settled sludge in the stripping zone lower section. The settled sludge is maintained under anaerobic conditions for a time sufficient to complete the release of the desired amount of phosphate from the sludge solids to the liquid phase of said settled sludge. At least a portion of the anaerobic sludge from the phosphate stripping zone is recycled to the aeration or high-purity oxygen zone as activatd sludge. The phosphate-rich supernatant from the phosphate stripping zone may be applied directly to land, or treated with a chemical precipitating agent to precipitate the phosphate therefrom and the precipitated phosphate may then be removed through the use of a reactor/clarifier, primary or secondary clarifier or other tankage, thus preparing the phosphate for final disposal directly or as fresh, digested or otherwise treated sludge.