Sewage treatment process with phosphorus removal

• US 6,712,970 B1
• Filed: 12/30/2002
• Issued: 03/30/2004
• Est. Priority Date: 01/11/2002
• Status: Expired due to Term

• Current Assignee: Ovivo Inc. (Susanne Klatten, MBA)
• Original Assignee: Enviroquip, Inc. (Groupe LaPerriere & Verreault Inc.)
• Inventors: Trivedi, Hiren K.
• Primary Examiner(s): Prince, Fred G.
• Application Number:
  US10/331,270
• Time in Patent Office: 456 Days
• Field of Search: 210/605, 210/614, 210/620, 210/621, 210/623, 210/626, 210/630, 210/903, 210/906
• US Class Current: 210/605
• CPC Class Codes: C02F 2209/04 Oxidation reduction potential [ORP]
• CPC Class Codes: C02F 2209/06 pH
• CPC Class Codes: C02F 2209/07 Alkalinity
• CPC Class Codes: C02F 2209/12 Volatile Fatty Acids (VFAs)
• CPC Class Codes: C02F 2209/14 NH3-N
• CPC Class Codes: C02F 2209/15 N03-N
• CPC Class Codes: C02F 2209/18 PO4-P
• CPC Class Codes: C02F 2209/36 Biological material, e.g. enzymes or ATP
• CPC Class Codes: C02F 3/006 Regulation methods for biological treatment
• CPC Class Codes: C02F 3/308 Biological phosphorus removal
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage
• CPC Class Codes: Y10S 210/903 Nitrogenous
• CPC Class Codes: Y10S 210/906 Phosphorus containing

Abstract

In the liquid side of sewage treatment process, a combination aerobic/anoxic stage is closely monitored such that phosphorus can be removed as well as nitrogen. As in a known process, the aerobic/anoxic stage is monitored as to a coenzyme of the active bacteria. When the bacteria of flocs within this stage show a switch to anaerobic condition via such coenzyme, the low dissolved oxygen level in the stage is maintained for a preselected period of time or to a preselected extent of the anaerobic condition, before oxygen is added. This somewhat brief anaerobic condition within the flocs is sufficient to release significant amounts of phosphorus into the liquid. When aeration then is increased, enhanced biological phosphorus uptake is effected. A small aerobic stage is included after the aerobic/anoxic stage to ensure maximum phosphorus uptake, and in one embodiment this stage includes a membrane separator, allowing downstream secondary clarification to be eliminated.

Claims

1. In a sewage treatment plant and process having a liquid side in which nitrogen removal is effected, a method of operating the liquid side of the treatment process so as additionally to remove phosphorus, comprising:

(a) maintaining an aerobic/anoxic zone receiving plant influent wastewater,

(b) maintaining dissolved oxygen concentration in the aerobic/anoxic zone in a fluctuating range,

(c) with dissolved oxygen concentration toward the lower end of said range and tending to promote denitrification, monitoring the status of bacteria in the aerobic/anoxic zone and detecting when bacteria near the centers of flocs turn anaerobic,

(d) allowing the anaerobic condition to develop in the flocs to a preselected extent and thereby causing phosphorus to be released into the liquid, then adding dissolved oxygen to the aerobic/anoxic zone to effect recovery of at least some of the bacteria from the anaerobic condition and causing uptake of phosphorus, as well as effecting nitrification,

(e) then limiting dissolved oxygen to the aerobic/anoxic zone to an extent to allow the bacteria to consume the dissolved oxygen,

(f) repeating steps (c) through (e), and

(g) moving effluent from the aerobic/anoxic zone to an aerobic zone in which dissolved oxygen concentration is maintained in a higher range sufficient to enhance biological phosphorus uptake,

whereby nitrification, denitrification, phosphorus release and some biological phosphorus uptake occur in the aerobic/anoxic zone, and further nitrification and biological phosphorus uptake are enhanced in the aerobic zone.

2. The method of claim 1, wherein the anaerobic condition is allowed to develop in the flocs for a preselected period of time, said preselected period being at least about one minute.

3. The method of claim 2, wherein the preselected period of time is in the range of about one minute to about thirty minutes.

4. The method of claim 2, wherein the preselected period of time is about one minute to about five minutes.

5. The method of claim 1, wherein the range of dissolved oxygen concentration in the aerobic zone is about 0.5 to 5.0 ppm.

6. The method of claim 1, wherein the dissolved oxygen concentration maintained in the anoxic/aerobic zone is less than about 1.0 ppm.

7. The method of claim 1, wherein the range of dissolved oxygen concentration maintained in the anoxic/aerobic zone is about 0.01 to about 0.99 ppm.

8. The method of claim 1, wherein the aerobic/anoxic zone receives plant influent in a continuous flow, and wastewater flows from the aerobic/anoxic zone to the aerobic zone in a continuous flow.

9. The method of claim 1, wherein the aerobic/anoxic zone receives plant influent in a continuous flow, and wastewater flows from the aerobic/anoxic zone and from the aerobic zone to a secondary clarification zone in a continuous zone.

10. The method of claim 1, wherein the development of anaerobic condition is detected by chemical measurements of any of the following:

ammonium, phosphate, nitrates and volatile fatty acid concentration, measurement of redox potential, pH, alkalinity short-term measurements of BOD, COD, measurement of CO₂ concentration or with measurement of fluorescence emission from at least one characteristic biogenic fluorophore selected from the group consisting of NADH, NAD(P)H, tryptophan—

and tyrosine-containing proteins, tryptophan—

and tyrosine-containing peptides, tryptophan—

and tyrosine-containing derivatives of amino acids, purines, pyrimidines, nucleosides, nucleotides, nucleic acids, steroids and vitamins, and combination thereof.

11. The method of claim 1, further including using a membrane separator within the aerobic zone to separate out liquid from the wastewater, thus concentrating wastewater sludge within the aerobic zone.

12. The method of claim 11, further including recycling a portion of sludge leaving the aerobic zone, back to the aerobic/anoxic zone.

13. The method of claim 11, without secondary clarification downstream of the aerobic zone.

14. The method of claim 1, further including secondary clarification of wastewater sludge downstream of the aerobic zone, and recycling of a portion of sludge resulting from secondary clarification back to the aerobic/anoxic zone.

15. The method of claim 1, wherein in step (d) the anaerobic condition is allowed to develop until a coenzyme concentration characteristic of an anaerobic condition is detected as reaching a preselected percent change.