Process for biological purification of waste water under sludge retention

• US 6,325,933 B1
• Filed: 05/09/2000
• Issued: 12/04/2001
• Est. Priority Date: 09/16/1997
• Status: Expired due to Term

• Current Assignee: Kruger Off-Shore A/S
• Original Assignee: Kruger (Veolia Environnement SA)
• Inventors: Dahl, Claus Poulsen, Nielsen, Marinus
• Primary Examiner(s): Simmons, David A.
• Assistant Examiner(s): PRINCE JR, FREDDIE GARY
• Application Number:
  US09/508,637
• Time in Patent Office: 574 Days
• Field of Search: 210/605, 210/608, 210/623, 210/624, 210/626, 210/628, 210/629, 210/630, 210/195.1, 210/195.3, 210/201, 210/202, 210/205, 210/219, 210/220, 210/906, 210/926
• US Class Current: 210/605
• CPC Class Codes: C02F 3/12 Activated sludge processes
• CPC Class Codes: C02F 3/30 Aerobic and anaerobic processes
• CPC Class Codes: C02F 3/302 Nitrification and denitrification treatment C02F3/308 takes precedence
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A process for biological purification of waste water by the activated sludge method wherein the waste water is continuously passed through one or more treatment zones and a clarification zone, wherein the waste water treated in the last treatment zone at the outlet from the zone under suitable control of aeration and stirring is continuously divided into a predominantly aqueous fraction and a sludge-containing fraction, and wherein a portion of the sludge fraction is recirculated and mixed with non-treated waste water, of which the former is subjected to clarification, and the latter is recirculated to the same or a preceding treatment zone.

Claims

1. A process for biological purification of waste water comprising the steps of:

(a) providing a mixture of non-treated waste water and sludge and continuously supplying said mixture into an inlet end of an aerobic treatment zone which has an inlet end and an outlet end,

(b) aerating and stirring said mixture in said aerobic treatment zone so as to provide a water-rich fraction and a sludge-rich fraction as said mixture moves toward said outlet end,

(c) passing said water-rich fraction from said aerobic treatment zone to a clarification zone wherein said water-rich fraction is separated into a water fraction and a sludge fraction,

(d) recirculating a portion of said sludge fraction from step (c) to form the mixture in step (a),

(e) recovering said water fraction from step (c), and

(f) recirculating a portion of said sludge-rich fraction at said outlet end of said aerobic treatment zone to said inlet end.

2. A process for biological purification of waste water comprising the steps of:

(a) providing a mixture of non-treated waste water and sludge and continuously supplying said mixture to at least one anoxic treatment zone wherein said mixture is denitrified,

(b) passing said denitrified mixture to an inlet end of an aerobic treatment zone which has an inlet end and an outlet end,

(c) aerating and stirring said denitrified mixture in said aerobic treatment zone so as to provide a water-rich fraction and a sludge-rich fraction as said mixture moves toward said outlet end,

(d) passing said water-rich fraction from said aerobic treatment zone to a clarification zone wherein said water-rich fraction is separated into a water fraction and a sludge fraction,

(e) recirculating a portion of said sludge fraction from step (d) to form said mixture in step (a),

(f) recovering said water fraction from step (d), and

(g) recirculating a portion of said sludge-rich fraction at said outlet end of said aerobic treatment zone to said at least one anoxic treatment zone.

3. A process for biological purification of waste water comprising the steps of:

(a) providing a mixture of non-treated waste water and sludge and continuously supplying said mixture to at least one anaerobic treatment zone so as to remove phosphorus from said mixture and improve precipitation of said sludge,

(b) passing said mixture from step (a) to at least one anoxic treatment zone wherein said mixture is denitrified,

(c) passing said denitrified mixture to an inlet end of an aerobic treatment zone which has an inlet end and an outlet end,

(d) aerating and stirring said denitrified mixture in said aerobic treatment zone so as to provide a water-rich fraction and a sludge-rich fraction as said mixture moves toward said outlet end,

(e) passing said water-rich fraction from said aerobic treatment zone to a clarification zone wherein said water-rich fraction is separated into a water fraction and a sludge fraction,

(f) recirculating a portion of said sludge fraction from step (e) to form the mixture in step (a),

(g) recovering said water fraction from step (e), and

(h) recirculating a portion of said sludge-rich fraction at said outlet end of said aerobic treatment zone to said at least one anoxic treatment zone.

4. A process according to claim 3, including a step (i) of recirculating a portion of said sludge-rich fraction at said outlet end of said aerobic treatment zone to said anaerobic treatment zone.

5. An apparatus for biological purification of waste water which comprises:

an elongated annular channel treatment tank which defines an inlet end and an outlet end and in which a mixture of waste water and sludge can be aerated and stirred as said mixture moves from said inlet end to said outlet end, said treatment tank including a horizontal guide plate at said outlet end for dividing said aerated and stirred mixture into an upper water-rich fraction and a lower sludge-rich fraction,

a first flow line for supplying a mixture of waste water and sludge to said inlet end of said treatment tank,

a clarifier device for clarifying said water-rich fraction into a water fraction and a sludge fraction,

a second flow line for delivering said water-rich fraction from said treatment tank to said clarifier device,

a third flow line for recirculating a portion of said sludge fraction to said first flow line, and

a fourth flow line for removing said water fraction from said clarifier device.

6. An apparatus according to claim 5, including a stirrer in said elongated annular-channel treatment tank at said inlet end thereof.