Method for treatment of digester supernatant and other streams in wastewater treatment facilities

• US 4,076,515 A
• Filed: 07/09/1975
• Issued: 02/28/1978
• Est. Priority Date: 07/09/1975
• Status: Expired due to Term

• Current Assignee: Rickard M. David
• Original Assignee: Rickard M. David
• Inventors: Rickard, M. David
• Primary Examiner(s): Bascomb, Jr., Wilbur L.
• Assistant Examiner(s): Therkorn, Ernest G.
• Application Number:
  US05/594,541
• Time in Patent Office: 965 Days
• Field of Search: 71/8-10, 71/12, 71/54, 71/57, 210/10, 210/16, 210/26, 210/28, 210/45, 210/48, 210/9, 210/8, 210/18, 55/70, 423/357
• US Class Current: 71/10
• CPC Class Codes: C02F 1/586 by removing ammoniacal nitrogen for biological methods C02F3/00
• CPC Class Codes: C02F 11/12 by de-watering, drying or thickening
• CPC Class Codes: C05F 7/00 Fertilisers from waste water, sewage sludge, sea slime, ooze or similar masses
• CPC Class Codes: Y02A 40/20 Fertilizers of biological origin, e.g. guano or fertilizers made from animal corpses
• CPC Class Codes: Y02E 50/30 Fuel from waste, e.g. synthetic alcohol or diesel
• CPC Class Codes: Y02W 30/40 Bio-organic fraction processing; Production of fertilisers from the organic fraction of waste or refuse
• CPC Class Codes: Y10S 210/918 Miscellaneous specific techniques

Abstract

Digester supernatants and/or liquors from sludge dewatering are reacted with an excess of an alkaline reagent having a stronger cation than the ammonium ion and the reaction product is separated into a solution containing aqueous ammonia and solids. The aqueous ammonia derived from the separation stage is heated by free steam under a lowered pressure to free ammonia in gaseous form. The ammonia as a gas, or adsorbed in water, or adsorbed in an acid, or as an acid salt is then mixed with conventionally dried sludge to increase the nitrogen content of the sludge from approximately 1-2 percent to as high as 10 percent.

Claims

1. A method of treating waste water in a sewage treatment plant to remove ammonia comprising the sequential steps of:

A. reducing said waste water to sludge;

B. placing said sludge in an anaerobic digester;

(1) converting a substantial quantity of the putrescible organic material found in said sludge to methane and carbon dioxide, and,

(2) converting a substantial quantity of nitrogen found in said sludge to ammonia;

C. removing the digester supernatant;

D. dewatering said digested sludge to separate from the sludge, dewatering liquor being substantially composed of water and water soluble ammonia;

E. combining said supernatant with said dewatering liquor;

F. reacting with said supernatant and dewatering liquor, to form a reaction product, a stoichiometric excess of lime thus converting ammonia salts found in the supernatant and dewatering liquor to free or aqueous ammonia;

G. rendering the ammonia less soluble in the reaction product by applying to said product, live steam under reduced pressure.

2. The method of treating waste water as recited in claim 1 further comprising the steps of

A. drying the sludge;

B. reacting the ammonia recovered from the waste water with acid to form an ammonium salt; and

C. mixing the ammonium salt with the dried sludge to form a nitrogen enriched fertilizer.