Process for the purification of polluted water

• US 5,667,688 A
• Filed: 04/10/1996
• Issued: 09/16/1997
• Est. Priority Date: 12/23/1991
• Status: Expired due to Fees

• Current Assignee: T Kruger Systems As
• Original Assignee: T Kruger Systems As
• Inventors: Henze, Mogens, Kerrn-Jespersen, Jens Peter
• Primary Examiner(s): Upton, Christopher
• Application Number:
  US08/632,343
• Time in Patent Office: 524 Days
• Field of Search: 210/605, 210/615, 210/617, 210/618, 210/622, 210/624, 210/626, 210/630, 210/195.1, 210/195.3, 210/259, 210/903, 210/906
• US Class Current: 210/605
• CPC Class Codes: C02F 3/06 using submerged filters
• CPC Class Codes: C02F 3/2806 Anaerobic processes using solid supports for microorganisms
• 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

Process and plant for biological purification of polluted water wherein the polluted water is successively subjected to an anaerobic, anoxic and aerobic treatment in the presence of microorganisms, and wherein the anaerobic and the anoxic treatment are carried out in the presence of one or more microorganism cultures which are different from the microorganism culture used in the aerobic treatment. Hereby better exploitation of organic matter in the water is obtained thus improving the removal of nitrogen, and an increased reaction rate per unit mass of biomass is obtained thereby allowing the amount of biomass to be reduced or the total reaction rate of the plant to be increased.

Claims

1. A process for the biological purification of polluted water comprising the steps of subjecting the polluted water to successive anaerobic, anoxic and aerobic treatments in the presence of first and second separate cultures of microorganisms, the treatment in the presence of the first culture of microorganisms being carried out solely under anaerobic and anoxic conditions and the treatment in the presence of the second culture of microorganisms being carried out under aerobic conditions.

2. A process according to claim 1, comprising the steps of successively subjecting a mixture of polluted water and a suspended microorganism culture to an anaerobic and an anoxic treatment in one or more treatment zones, separating the microorganisms from the water, adding another micro-organism culture to the water, subjecting the mixture thus formed to treatment in one or more aerobic treatment zones, separating the micro-organism culture from the water thus treated, and recycling a part of the separated water to the anoxic treatment zone.

3. A process according to claim 2, including the step of recycling at least part of the suspended micro-organism culture separated after treatment in the anoxic treatment zone to the anaerobic treatment zone.

4. A process according to claims 2, including the step of recycling at least part of the micro-organism culture separated from the aerobically treated water to the aerobic treatment zone.

5. A process according to claim 2, wherein the anaerobic and anoxic treatments occur in two separate treatment zones, and including the steps of alternatively maintaining anaerobic and anoxic conditions in said separate treatment zones, and feeding polluted water to the zone where anaerobic conditions are maintained.

6. A process according to claim 1, including the steps of using at least two immobilised micro-organism cultures which are kept in anaerobic or anoxic and aerobic conditions, respectively, and recycling a part of the water which leaves the micro-organism culture kept in aerobic conditions to the micro-organism culture which is kept in anoxic conditions.

7. A process according to claim 6, including the steps of using three immobilised micro-organism cultures and keeping the two first micro-organism cultures of the three in alternatingly anaerobic and anoxil conditions, and conducting polluted water alternatingly to the first and the second of the two first immobilised micro-organism cultures, wherein polluted water is always fed to the micro-organism culture which is kept in anaerobic conditions whereas the discharge from the immobilised micro-organism culture which is kept in anaerobic conditions is conducted to the second of the two first immobilised micro-organism cultures together with nitrate-containing water recycled from the immobilised micro-organism culture which is kept in anaerobic conditions.

8. A process according to claim 1, including the steps of successively subjecting the polluted water to an anaerobic and an anoxic treatment in two zones using a suspended micro-organism culture, separating the micro-organism culture from the water thus treated, said micro-organism culture being recycled to the anaerobic treatment zone, and subjecting the water relieved of the micro-organism culture to an aerobic treatment with an immobilised micro-organism culture following which a part of the aerobically treated water is recycled to the anoxic treatment step.

9. An apparatus for the biological treatment of polluted water which comprises means for successively subjecting polluted water to an anaerobic and an anoxic treatment solely under anaerobic and anoxic conditions using a first micro-organism culture, means for subjecting the anaerobically and anoxically treated water to an aerobic treatment using a second micro-organism culture which is different and separate from the first micro-organism culture, and means for recycling aerobically treated water to the means for treating the water in anoxic conditions.

10. An apparatus according to claim 9, wherein the means for anaerobic and anoxic treatment of the water using the first micro-organism culture comprise an anaerobic and an anoxic tank, means for separating off sludge from the anoxically treated water and means for recycling the sludge thus separated to the anaerobic tank.

11. An apparatus according to claim 9, wherein the means for anaerobic and anoxic treatment of the water using the first micro-organism culture comprise at least one biological filter comprising a carrier material to which the micro-organism culture is attached.

12. An apparatus according to claim 11, including further means for periodical backwashing of the filters for removal of excess micro-organism containing material from the filters.

13. An apparatus according to claim 9 wherein the means for aerobic treatment of the anaerobically and anoxically treated water using the second microorganism culture comprise an aerobic tank, means for separating sludge from the aerobically treated water and means for recycling the sludge thus separated to the aerobic tank.

14. An apparatus claim 9, wherein the means for aerobic treatment of the anaerobically and anoxically treated water using the second micro-organism culture comprise a biological filter comprising a carrier material to which the micro-organism culture is attached.

15. An apparatus according to claim 9, including three biological filters connected in series wherein anaerobic, anoxic and aerobic conditions, respectively, can be maintained, and means for alternatingly feeding polluted water to the two first filters and for alternatingly changing the treatment conditions in said filters from anaerobic to anoxic treatment and vice versa.