Pathogen inactivation in biosolids with cavitation

• US 6,635,178 B2
• Filed: 12/11/2001
• Issued: 10/21/2003
• Est. Priority Date: 12/19/2000
• Status: Expired due to Fees

• Current Assignee: Dwight D. Bowman, Elizabeth A. Fogarty
• Original Assignee: Dwight D. Bowman, Elizabeth A. Fogarty
• Inventors: Bowman, Dwight D., Fogarty, Elizabeth A.
• Primary Examiner(s): Barry, Chester T.
• Application Number:
  US10/015,028
• Publication Number:
  US 20020158010A1
• Time in Patent Office: 679 Days
• Field of Search: 210/609, 210/613, 210/764, 210/173
• US Class Current: 210/609
• CPC Class Codes: A61L 2/0011 using physical methods
• CPC Class Codes: A61L 2/0023 Heat
• CPC Class Codes: A61L 2/0082 using chemical substances
• CPC Class Codes: C02F 11/18 by thermal conditioning by pyrolysis C02F11/10
• CPC Class Codes: C02F 11/185 by pasteurisation
• CPC Class Codes: C02F 2303/04 Disinfection
• CPC Class Codes: C02F 2303/06 Sludge reduction, e.g. by lysis

Abstract

A process for destroying pathogens in sludges/biosolids using rotor-stator technology to produce cavitation for pathogen destruction, combined with the feeding of lime or other alkaline material to induce heat and ammonia gas release. The combination of the rotor-stator with the lime produces higher temperatures than the addition of lime alone with a very high mixing efficiency giving maximum pH shift and ammonia release to all portions of the matrix. Overall, the process destroys the resistant stages of helminths or protozoan pathogens through a combination of cavitation with the increased heat caused by the rotor-stator/lime process, along with the locally released ammonia induced by the pH shift.

Claims

1. A method of pathogen inactivation in biosolids comprising the steps of:

a) digesting the biosolids producing digested biosolids; and

b) mixing an alkaline agent with the digested biosolids in at least one high-speed rotor/stator mixer at a speed sufficient to produce cavitation, producing treated sludge.

2. The method of claim 1, further comprising the step, before step (a), of processing the biosolids in at least one high-speed rotor/stator mixer at a speed sufficient to produce cavitation.

3. The method of claim 2, in which the biosolids comprise a mixture of activated sludge and a process stream from a primary clarifier.

4. The method of claim 2, in which the processing step is performed in a plurality of high speed rotor/stator mixers, connected in series.

5. The method of claim 1, further comprising the step of containing the treated sludge in a vessel for at least 12 hours.

6. The method of claim 1, further comprising the step of dewatering the treated sludge.

7. The method of claim 1, in which the mixing step (b) is performed in a plurality of high speed rotor/stator mixers, connected in series.

8. The method of claim 1, wherein the alkaline agent added in step (b) is selected from a group consisting of lime, fly ash, and kiln dust.