Process for biological treatment of organic wastewater and apparatus therefor

• US 20060249448A1
• Filed: 07/13/2006
• Published: 11/09/2006
• Est. Priority Date: 02/02/2004
• Status: Active Grant

• Current Assignee: Kurita Water Industries Limited
• Original Assignee: Kurita Water Industries Limited
• Inventors: Fujishima, Shigeki, Yoda, Motoyuki
• Granted Patent: US 7,332,084 B2
• Time in Patent Office: Days
• US Class Current: 210/602
• CPC Class Codes: C02F 2209/40 Liquid flow rate
• CPC Class Codes: C02F 2303/06 Sludge reduction, e.g. by lysis
• CPC Class Codes: C02F 3/121 Multistep treatment
• CPC Class Codes: C02F 3/1221 comprising treatment of the recirculated sludge
• CPC Class Codes: C02F 3/1273 Submerged membrane bioreactors
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A multistage activated sludge process involving a predation effect caused by microorganisms realizes further improvement in treatment efficiency and further decrease in the amount of excess sludge generated while a stable quality of the treated water is maintained. This process includes a first biological treatment process for treating BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria, and a second biological treatment process for forming the converted dispersed bacteria into a floc and allowing microorganisms to coexist. The second biological treatment process is performed under a condition of pH 5 to 6. Alternatively, an excess sludge treatment process for decomposing at least a part of sludge in the second biological treatment process and/or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment process under aerobic conditions, and returning the treated sludge to the first biological treatment process and/or the second biological treatment process is performed under a condition of pH 5 to 6.

Claims

1. A process for biological treatment of organic wastewater, comprising:

a first biological treatment process for treating BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria; and

a second biological treatment process for forming the converted dispersed bacteria into a floc and allowing microorganisms to coexist,

wherein the second biological treatment process is performed under a condition of pH 5 to 6.

2. The process for biological treatment of organic wastewater according to claim 1, wherein the second biological treatment process is a multistage treatment including two or more stages, and the second biological treatment process includes a biological treatment performed at a pH in the range of 5 to 6 and a subsequent biological treatment performed at a pH 6 or more.

3. The process for biological treatment of organic wastewater according to claim 1, wherein the second biological treatment process is a sludge return-type biological treatment process in which solid-liquid separating means is provided at the latter stage of a biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, a fluidized-bed-type biological treatment process in which a carrier is added to a biological treatment tank, or a membrane-separation-type biological treatment process.

4. The process for biological treatment of organic wastewater according to claim 1, wherein the first biological treatment process is a fluidized-bed-type biological treatment process in which a carrier is added to a biological treatment tank, or a multistage treatment process including two or more stages.

5. A process for biological treatment of organic wastewater, comprising:

a first biological treatment process for treating BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria; and

a second biological treatment process for forming the converted dispersed bacteria into a floc and allowing microorganisms to coexist; and

an excess sludge treatment process for decomposing at least a part of sludge in the second biological treatment process and/or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment process under aerobic conditions,

wherein the sludge treated in the excess sludge treatment process is returned to the first biological treatment process and/or the second biological treatment process, and

the excess sludge treatment process is performed under a condition of pH 5 to 6.

6. The process for biological treatment of organic wastewater according to claim 5, wherein the excess sludge treatment process is a sludge return-type biological treatment process in which solid-liquid separating means is provided at the latter stage of a biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, or a fluidized-bed-type biological treatment process in which a carrier is added to a biological treatment tank.

7. The process for biological treatment of organic wastewater according to claim 5, wherein the second biological treatment process is a sludge return-type biological treatment process in which solid-liquid separating means is provided at the latter stage of a biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, a fluidized-bed-type biological treatment process in which a carrier is added to a biological treatment tank, or a membrane-separation-type biological treatment process.

8. The process for biological treatment of organic wastewater according to claim 5, wherein the first biological treatment process is a fluidized-bed-type biological treatment process in which a carrier is added to a biological treatment tank, or a multistage treatment process including two or more stages.

9. An apparatus for biological treatment of organic wastewater, comprising:

a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria; and

a second biological treatment tank that forms the converted dispersed bacteria into a floc and allows microorganisms to coexist,

wherein a process in the second biological treatment tank is performed under a condition of pH 5 to 6.

10. The apparatus for biological treatment of organic wastewater according to claim 9, wherein the process in the second biological treatment tank is a multistage treatment process including two or more stages, and the process in the second biological treatment tank includes a biological treatment performed at a pH in the range of 5 to 6 and a subsequent biological treatment performed at a pH 6 or more.

11. The apparatus for biological treatment of organic wastewater according to claim 9, wherein the process in the second biological treatment tank is a sludge return-type biological treatment process in which solid-liquid separating means is provided at the latter stage of the biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, a fluidized-bed-type biological treatment process in which a carrier is added to the biological treatment tank, or a membrane-separation-type biological treatment process.

12. The apparatus for biological treatment of organic wastewater according to claim 9, wherein a process in the first-biological treatment tank is a fluidized-bed-type biological treatment process in which a carrier is added to the biological treatment tank, or a multistage treatment process including two or more stages.

13. An apparatus for biological treatment of organic wastewater, comprising:

a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the BOD to dispersed bacteria; and

a second biological treatment tank that forms the converted dispersed bacteria into a floc and allows microorganisms to coexist; and

excess sludge treatment means that decomposes at least a part of sludge in the second biological treatment tank and/or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank under aerobic conditions,

wherein the sludge treated in the excess sludge treatment means is returned to the first biological treatment tank and/or the second biological treatment tank, and

the process in the excess sludge treatment means is performed under a condition of pH 5 to 6.

14. The apparatus for biological treatment of organic wastewater according to claim 13, wherein the excess sludge treatment means is sludge return-type biological treatment means in which solid-liquid separating means is provided at the latter stage of the biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, or fluidized-bed-type biological treatment means in which a carrier is added to the biological treatment tank.

15. The apparatus for biological treatment of organic wastewater according to claim 13, wherein the process in the second biological treatment tank is a sludge return-type biological treatment process in which solid-liquid separating means is provided at the latter stage of the biological treatment tank and sludge subjected to the solid-liquid separation is returned to the biological treatment tank, a fluidized-bed-type biological treatment process in which a carrier is added to the biological treatment tank, or a membrane-separation-type biological treatment process.

16. The apparatus for biological treatment of organic wastewater according to claim 13, wherein the process in the first biological treatment tank is a fluidized-bed-type biological treatment process in which a carrier is added to the biological treatment tank, or a multistage treatment process including two or more stages.

17. A process for biological treatment of organic wastewater, comprising introducing organic wastewater into a first biological treatment tank to perform a biological treatment using non-flocculating bacteria, and introducing the treated water containing the non-flocculating bacteria from the first biological treatment tank into a second biological treatment tank to perform an activated sludge treatment,

wherein at least a part of sludge in the second biological treatment tank or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is introduced into an anaerobic treatment process to perform an anaerobic treatment, and the product treated in the anaerobic treatment process is returned to the first biological treatment tank and/or the second biological treatment tank.

18. The process for biological treatment of organic wastewater according to claim 17, wherein the pH of the second biological treatment tank is 6 or less.

19. The process for biological treatment of organic wastewater according to claim 17, wherein the process in the second biological treatment tank is a multistage treatment process including two or more stages, and the process includes a biological treatment performed at a pH 6 or less and a subsequent biological treatment performed at a pH 6 or more.

20. The process for biological treatment of organic wastewater according to claim 17, wherein the product treated in the anaerobic treatment process is subjected to solid-liquid separation, the separated liquid is returned to the first biological treatment tank, and the separated sludge is returned to the second biological treatment tank.

21. A process for biological treatment of organic wastewater, comprising introducing organic wastewater into a first biological treatment tank to perform a biological treatment using non-flocculating bacteria, and introducing the treated water containing the non-flocculating bacteria from the first biological treatment tank into a second biological treatment tank to perform an activated sludge treatment,

wherein at least a part of sludge in the second biological treatment tank or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is introduced into an aerobic treatment process to oxidize it under aerobic conditions, at least a part of the product treated in the aerobic treatment process is introduced into an anaerobic treatment process to perform an anaerobic treatment, and the product treated in the anaerobic treatment process is returned to at least one of the first biological treatment tank, the second biological treatment tank, and the aerobic treatment process.

22. The process for biological treatment of organic wastewater according to claim 21, wherein the product treated in the anaerobic treatment process is subjected to solid-liquid separation, the separated liquid is returned to the first biological treatment tank, and the separated sludge is returned to at least one of the second biological treatment tank, the anaerobic treatment process, and the aerobic treatment process.

23. An apparatus for biological treatment of organic wastewater in which organic wastewater is introduced into a first biological treatment tank to perform a biological treatment using non-flocculating bacteria, and the treated water containing the non-flocculating bacteria from the first biological treatment tank is introduced into a second biological treatment tank to perform an activated sludge treatment,

wherein at least a part of sludge in the second biological treatment tank or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is introduced into anaerobic treatment means to perform an anaerobic treatment, and the product treated in the anaerobic treatment means is returned to the first biological treatment tank and/or the second biological treatment tank.

24. The apparatus for biological treatment of organic wastewater according to claim 23, wherein the pH of the second biological treatment tank is 6 or less.

25. The apparatus for biological treatment of organic wastewater according to claim 23, wherein the process in the second biological treatment tank is a multistage treatment including two or more stages, and the process includes a biological treatment performed at a pH 6 or less and a subsequent biological treatment performed at a pH 6 or more.

26. The apparatus for biological treatment of organic wastewater according to claim 23, wherein the product treated in the anaerobic treatment means is subjected to solid-liquid separation, the separated liquid is returned to the first biological treatment tank, and the separated sludge is returned to the second biological treatment tank.

27. An apparatus for biological treatment of organic wastewater in which organic wastewater is introduced into a first biological treatment tank to perform a biological treatment using non-flocculating bacteria, and the treated water containing the non-flocculating bacteria from the first biological treatment tank is introduced into a second biological treatment tank to perform an activated sludge treatment,

wherein at least a part of sludge in the second biological treatment tank or sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is introduced into aerobic treatment means to oxidize it under aerobic conditions, at least a part of the product treated in the aerobic treatment means is introduced into anaerobic treatment means to perform an anaerobic treatment, and the product treated in the anaerobic treatment means is returned to at least one of the first biological treatment tank, the second biological treatment tank, and the aerobic treatment means.

28. The apparatus for biological treatment of organic wastewater according to claim 27, wherein the product treated in the anaerobic treatment means is subjected to solid-liquid separation, the separated liquid is returned to the first biological treatment tank, and the separated sludge is returned to at least one of the second biological treatment tank, the anaerobic treatment means, and the aerobic treatment means.

29. A process for biological treatment of organic wastewater, comprising introducing organic wastewater into a first biological treatment tank to perform a biological treatment using bacteria, introducing the treated liquid containing the bacteria from the first biological treatment tank into a second biological treatment tank to perform an activated sludge treatment, performing solid-liquid separation of the treated liquid from the second biological treatment tank to separate the treated liquid into sludge and treated water, and returning a part of the sludge to the second biological treatment tank,

wherein a part of the sludge in the second biological treatment tank and/or the rest of the sludge obtained after the solid-liquid separation is introduced into a third biological treatment tank to perform an aerobic treatment, a part of or all of the sludge subjected to the aerobic treatment is dehydrated to separate into solid content and water, the solid content is drained as excess sludge, and the water is returned to the first biological treatment tank and/or the second biological treatment tank.

30. The process for biological treatment of organic wastewater according to claim 29, wherein the pH of the third biological treatment tank is 6 or less.

31. The process for biological treatment of organic wastewater according to claim 29, wherein the sludge retention time (SRT) of each of the second biological treatment tank and the third biological treatment tank is controlled to 40 days or less.

32. An apparatus for biological treatment of organic wastewater in which organic wastewater is introduced into a first biological treatment tank to perform a biological treatment using bacteria, the treated liquid containing the bacteria from the first biological treatment tank is introduced into a second biological treatment tank to perform an activated sludge treatment, solid-liquid separation of the treated liquid from the second biological treatment tank is performed to separate the treated liquid into sludge and treated water, and a part of the sludge is returned to the second biological treatment tank,

wherein a part of the sludge in the second biological treatment tank and/or the rest of the sludge obtained after the solid-liquid separation is introduced into a third biological treatment tank to perform an aerobic treatment, a part of or all of the sludge subjected to the aerobic treatment is dehydrated to separate into solid content and water, the solid content is drained as excess sludge, and the water is returned to the first biological treatment tank and/or the second biological treatment tank.

33. The apparatus for biological treatment of organic wastewater according to claim 32, wherein the pH of the third biological treatment tank is 6 or less.

34. The apparatus for biological treatment of organic wastewater according to claim 32, wherein the sludge retention time (SRT) of each of the second biological treatment tank and the third biological treatment tank is controlled to 40 days or less.

35. A process for biological treatment of organic wastewater, comprising introducing organic wastewater into a first biological treatment tank to perform a biological treatment using bacteria, introducing the treated liquid containing the bacteria from the first biological treatment tank into a second biological treatment tank to perform an activated sludge treatment,

wherein the sludge retention time of the second biological treatment tank is controlled to 5 to 40 days.

36. The process for biological treatment of organic wastewater according to claim 35, wherein sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is solubilized, and is then returned to the second biological treatment tank.

37. A process for biological treatment of organic wastewater, comprising introducing organic wastewater into a first biological treatment tank to perform a biological treatment using bacteria, introducing the treated liquid containing the bacteria from the first biological treatment tank into a second biological treatment tank to perform an activated sludge treatment, introducing sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank into a third biological treatment tank to oxidize it under aerobic conditions, and returning a part of or all of the product treated in the third biological treatment tank to the second biological treatment tank,

wherein the sludge retention time of each of the second biological treatment tank and the third biological treatment tank is controlled to 5 to 40 days.

38. An apparatus for biological treatment of organic wastewater in which organic wastewater is introduced into a first biological treatment tank to perform a biological treatment using bacteria, the treated liquid containing the bacteria from the first biological treatment tank is introduced into a second biological treatment tank to perform an activated sludge treatment,

wherein the sludge retention time of the second biological treatment tank is controlled to 5 to 40 days.

39. The apparatus for biological treatment of organic wastewater according to claim 38, wherein sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is solubilized, and is then returned to the second biological treatment tank.

40. An apparatus for biological treatment of organic wastewater, in which organic wastewater is introduced into a first biological treatment tank to perform a biological treatment using bacteria, the treated liquid containing the bacteria from the first biological treatment tank is introduced into a second biological treatment tank to perform an activated sludge treatment, sludge obtained by performing solid-liquid separation of sludge in the second biological treatment tank is introduced into a third biological treatment tank to oxidize it under aerobic conditions, and a part of or all of the product treated in the third biological treatment tank is returned to the second biological treatment tank,

wherein the sludge retention time of each of the second biological treatment tank and the third biological treatment tank is controlled to 5 to 40 days.

41. A process for biological treatment of organic wastewater in which a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the BOD to bacteria, and a second biological treatment tank in which the converted bacteria coexist with animalcules that prey upon the bacteria are provided,

wherein a hydraulic retention time (HRT) in the first biological treatment tank required for converting 70% or more and less than 100% of the BOD in standard organic wastewater to bacteria is determined to be defined as a standard HRT, and

a liquid is added to the organic wastewater introduced into the first biological treatment tank such that the HRT in the first biological treatment tank is controlled to be in the range of 0.75 to 1.5 times the standard HRT.

42. The process for biological treatment of organic wastewater according to claim 41, wherein the liquid is treated water passed through the second biological treatment tank.

43. The process for biological treatment of organic wastewater according to claim 41, wherein the first biological treatment tank is a fluidized-bed-type biological treatment tank in which a carrier is added.

44. A process for biological treatment of organic wastewater in which a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the BOD to bacteria, and a second biological treatment tank in which the converted bacteria coexist with animalcules that prey upon the bacteria are provided,

wherein a hydraulic retention time (HRT) in the first biological treatment tank required for converting 70% or more and less than 100% of the BOD in standard organic wastewater to bacteria is determined to be defined as a standard HRT, and

means that varies the amount of water in the first biological treatment tank such that the HRT in the first biological treatment tank is controlled to be in the range of 0.75 to 1.5 times the standard HRT is provided.

45. The process for biological treatment of organic wastewater according to claim 44, wherein the first biological treatment tank is a fluidized-bed-type biological treatment tank in which a carrier is added.

46. An apparatus for biological treatment of organic wastewater, comprising:

a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the,BOD to bacteria; and

a second biological treatment tank in which the converted bacteria coexist with animalcules that prey upon the bacteria,

wherein a hydraulic retention time (HRT) in the first biological treatment tank required for converting 70% or more and less than 100% of the BOD in standard organic wastewater to bacteria is determined to be defined as a standard HRT, and

the apparatus includes means that adds a liquid to the organic wastewater introduced into the first biological treatment tank such that the HRT in the first biological treatment tank is controlled to be in the range of 0.75 to 1.5 times the standard HRT.

47. The apparatus for biological treatment of organic wastewater according to claim 46, wherein the liquid is treated water passed through the second biological treatment tank.

48. The apparatus for biological treatment of organic wastewater according to claim 46, wherein the first biological treatment tank is a fluidized-bed-type biological treatment tank in which a carrier is added.

49. An apparatus for biological treatment of organic wastewater comprising:

a first biological treatment tank that treats BOD in organic wastewater at a high load to convert the BOD to bacteria; and

a second biological treatment tank in which the converted bacteria coexist with animalcules that prey upon the bacteria,

wherein a hydraulic retention time (HRT) in the first biological treatment tank required for converting 70% or more and less than 100% of the BOD in standard organic wastewater to bacteria is determined to be defined as a standard HRT, and

the apparatus includes means that varies the amount of water in the first biological treatment tank such that the HRT in the first biological treatment tank is controlled to be in the range of 0.75 to 1.5 times the standard HRT.

50. The apparatus for biological treatment of organic wastewater according to claim 49, wherein the first biological treatment tank is a fluidized-bed-type biological treatment tank in which a carrier is added.