Wastewater treatment system

• US 5,364,529 A
• Filed: 12/18/1992
• Issued: 11/15/1994
• Est. Priority Date: 05/01/1991
• Status: Expired due to Fees

• Current Assignee: Water Recovery, PLC
• Original Assignee: Level Valley Dairy Co.
• Inventors: Weir, Michael J., Morin, Raymond N.
• Primary Examiner(s): Upton, Christopher
• Application Number:
  US07/993,714
• Time in Patent Office: 697 Days
• Field of Search: 210/608, 210/611, 210/615, 210/617, 210/623, 210/624, 210/626, 210/629, 210/704, 210/195.1, 210/195.3, 210/197, 210/202, 210/220, 210/221.2, 210/259, 210/257.1 , 210/631, 210/705, 210/209
• US Class Current: 210/608
• CPC Class Codes: C02F 3/04 using trickle filters
• CPC Class Codes: C02F 3/121 Multistep treatment
• CPC Class Codes: C02F 3/1215 Combinations of activated sludge treatment with precipitation, flocculation, coagulation and separation of phosphates
• CPC Class Codes: C02F 3/34 characterised by the microorganisms used
• CPC Class Codes: Y02W 10/10 Biological treatment of water, waste water, or sewage

Abstract

A wastewater treatment system is provided which includes (a) two chambers in which microbiological cultures grow aerobically, a first chamber which receives wastewater to be treated and a second chamber which produces activated sludge; (b) a float sludge separator for removing from the system float sludge made with the aerobic culture from the first chamber; and (c) an activated sludge separator for separating activated sludge, which is settleable, and treated wastewater from the aerobic culture in the second chamber. In the system, one portion of the activated sludge from the activated sludge separator is fed to the first chamber, to seed culture growth there, and another portion of the activated sludge is recycled to the second chamber, to seed culture growth there.

Claims

1. A wastewater treatment apparatus, comprising:

a first chamber, a float-sludge-separating means, a float-sludge-removing means, a second chamber, an activated-sludge-separating means, a first activated-sludge-return means;

a second activated-sludge-return means; and

a fluid discharging means;

said first chamber (i) wherein wastewater from a wastewater source is received, (ii) and wherein fluid that enters said first chamber for a first detention period is detained, (iii) comprising a first aerating means for aerating fluid in said first chamber, and (iv) holding a first aerobic culture of a first biological oxidizing means, said first culture employing constituents of wastewater received into said first chamber as nutrients and receiving as seed microorganisms in activated sludge returned to said first chamber via said first activated-sludge-return means from said activated-sludge-separating means;

said float-sludge-separating means receiving said first aerobic culture from said first chamber and comprising (i) means for combining a flocculating polymer with first aerobic culture received into said float-sludge-separating means, and (ii) a second aerating means for aerating fluid in said float-sludge-separating means and for providing air bubbles for separation of a float sludge from said combination of first aerobic culture and said flocculating polymer in said float-sludge-separating means, with the production of said float sludge from said combination, leaving a first effluent;

said float-sludge-removing means being a means for removing said float sludge from said float-sludge-separating means to outside the apparatus;

said second chamber (i) wherein said first effluent from said float-sludge-separating means is received, (ii) and wherein fluid that enters said second chamber for a second detention period is detained, (iii) comprising a third aerating means for aerating fluid in said second chamber, and (iv) holding a second aerobic culture of a second biological oxidizing means, said second culture employing constituents of said first effluent received into said second chamber as nutrients and receiving as seed microorganisms in activated sludge returned to said second chamber via said second activated-sludge-return means from said activated-sludge-separating means;

said activated-sludge-separating means receiving said second aerobic culture from said second chamber, said activated sludge formed from separation in said activated-sludge-separating means by settling from said second aerobic culture in said activated-sludge-separating means, leaving a second effluent;

said first return means being a means for returning a first portion of the activated sludge from said activated-sludge-separating means to said first chamber to provide microorganisms as seed for said first aerobic culture in said first chamber;

said second return means being a means for returning a second portion of the activated sludge from said activated-sludge-separating means to said second chamber to provide microorganisms as seed for said second aerobic culture in said second chamber; and

said fluid discharging means being a means for discharging at least a portion of said second effluent from said activated-sludge-separating means to outside the apparatus.

2. The apparatus of claim 1, wherein said first and second portions of said activated sludge are together substantially all of the activated sludge formed in said activated-sludge-separating means;

wherein at least about 90% of second effluent from said activated-sludge-separating means is discharged to outside the apparatus; and

wherein, in said discharged second effluent, the concentration of suspended solids is less than about 20% of the concentration of suspended solids in said first aerobic culture and the BOD is less than about 20% of the BOD of said first aerobic culture.

3. The apparatus of claim 1 which comprises additionally a float-sludge-storing means, for receiving float sludge via the float-sludge-removing means from the float-sludge-separating means and holding until removed from the apparatus said float sludge so received, said float-sludge-storing means comprising a fourth aerating means for aerating float sludge held in said float-sludge-storing means to maintain said float sludge so held as aerobic sludge until removal from the apparatus.

4. The apparatus of claim 3 which comprises additionally a grease-trapping means for receiving wastewater from the wastewater source and removing fat-based substances from the wastewater prior to entry of the wastewater into said first chamber.

5. The apparatus of claim 4 wherein the first return means delivers the activated sludge returned from said activated-sludge-separating means into wastewater in said grease-trapping means, whereupon a combination of said activated sludge and wastewater passes from said grease-trapping means into said first chamber.

6. The apparatus of claim 4 which comprises additionally (i) a means for aerating said first effluent prior to receipt of said first effluent into said second chamber and (ii) means for filtering said second effluent prior to discharge of said second effluent to outside the apparatus.

7. The apparatus of claim 6 wherein (i) said second chamber is an extended aeration chamber;

(ii) said activated-sludge-separating means is a clarifier;

(iii) said means for aerating said first effluent prior to receipt of said first effluent into said second chamber is a trickling filter tower; and

(iv) said means for filtering said second effluent prior to discharge to outside the apparatus is a sand filter.

8. The apparatus of claim 4 wherein the wastewater source is a food-processing plant.

9. The apparatus of claim 8 wherein the wastewater source is a milk-processing plant.

10. The apparatus of claim 9 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

11. The apparatus of claim 10 wherein the pH of said first aerobic culture is from about 8 to about 9.

12. The apparatus of claim 11 wherein, in the first aerobic culture, the amount of suspended solids is from about 1200 mg/l to about 2400 mg/l and the BOD₅ is from about 2500 mg/l to about 6000 mg/l;

in the second aerobic culture, the amount of suspended solids is from about 2500 mg/l to about 4000 mg/l and the BOD₅ is from about 1200 mg/l to about 3600 mg/l; and

in the activated sludge, the amount of suspended solids is between about 2500 mg/l and about 5000 mg/l and the BOD₅ is between about 2000 mg/l and about 4000 mg/l.

13. The apparatus of claim 8 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

14. The apparatus of claim 4 wherein the wastewater source is a food-processing plant.

15. The apparatus of claim 14 wherein the wastewater source is a milk-processing plant.

16. The apparatus of claim 15 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

17. The apparatus of claim 16 wherein the pH of said first aerobic culture is from about 8 to about 9.

18. The apparatus of claim 14 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

19. The apparatus of claim 1 wherein said first and second biological oxidizing means comprise filamentous microorganisms.

20. The apparatus of claim 1 wherein, in the first aerobic culture, the amount of suspended solids is from about 1200 mg/l to about 2400 mg/l and the BOD₅ is from about 2500 mg/l to about 6000 mg/l;

in the second aerobic culture, the amount of suspended solids is from about 2500 mg/l to about 4000 mg/l and the BOD₅ is from about 1200 mg/l to about 3600 mg/l; and

in the activated sludge, the amount of suspended solids is between about 2500 mg/l and about 5000 mg/l and the BOD₅ is between about 2000 mg/l and about 4000 mg/l.

21. The apparatus according to any one of claims 1-20 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l.

22. The apparatus according to any one of claims 1-20 wherein the float-sludge-separating means comprises a means for combining an aqueous solution of a ferric salt with first aerobic culture received into said float-sludge-separating means.

23. The apparatus according to claim 22 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l and the concentration of phosphate in said first aerobic culture is from about 50 mg/l to about 100 mg/l.

24. The apparatus of claim 1, further comprising:

a first conveying means for inputing wastewater into said first chamber from the wastewater source;

a second conveying means for passing first aerobic culture from said first chamber to said float- sludge-separating means; and

a third conveying means for passing said first effluent to said second chamber.

25. The apparatus of claim 1, wherein the first chamber comprises a tank which is substantially cylindrical, has a top end substantially completely open to the atmosphere, and has a ratio of radius to maximum depth of wastewater detained in the tank that is greater than 1.

26. The apparatus of claim 25, wherein said first aerating means comprises an array of diffusers substantially covering the bottom cross-sectional area of said tank.

27. The apparatus of claim 26, wherein said diffusers have a pressure delivery capacity of about 2 p.s.i.g to about 7 p.s.i.g.

28. The apparatus according to any one of claims 24-27 wherein the float-sludge-separating means comprises a means for combining an aqueous solution of a ferric salt with first aerobic culture received into said float-sludge-separating means.

29. A method of treating a contaminated wastewater to provide a treated wastewater, which has a substantially lower concentration of suspended solids and substantially lower BOD than the contaminated wastewater, said method comprising passing the contaminated wastewater into a wastewater treatment apparatus, said apparatus comprising:

a first chamber, a float-sludge-separating means, a float-sludge-removing means, a second chamber, an activated-sludge-separating means, a first activated-sludge-return means;

a second activated-sludge-return means; and

a fluid discharging means;

said first chamber (i) wherein wastewater from a wastewater source is received, (ii) and wherein fluid that enters said first chamber for a first detention period is detained, (iii) comprising a first aerating means for aerating fluid in said first chamber, and (iv) holding a first aerobic culture of a first biological oxidizing means, said first culture employing constituents of wastewater received into said first chamber as nutrients and receiving as seed microorganisms in activated sludge returned to said first chamber via said first activated-sludge-return means from said activated-sludge-separating means;

said float-sludge-separating means receiving said first aerobic culture from said first chamber and comprising (i) means for combining a flocculating polymer with first aerobic culture received into said float-sludge-separating means, and (ii) a second aerating means for aerating fluid in said float-sludge-separating means and for providing air bubbles for separation of a float sludge from said combination of first aerobic culture and said flocculating polymer in said float-sludge-separating means, with the production of said float sludge from said combination, leaving a first effluent;

said float-sludge-removing means being a means for removing said float sludge from said float-sludge-separating means to outside the apparatus;

said second chamber (i) wherein said first effluent from said float-sludge-separating means is received, (ii) and wherein fluid that enters said second chamber for a second detention period is detained, (iii) comprising a third aerating means for aerating fluid in said second chamber, and (iv) holding a second aerobic culture of a second biological oxidizing means, said second culture employing constituents of said first effluent received into said second chamber as nutrients and receiving as seed microorganisms in activated sludge returned to said second chamber via said second activated-sludge-return means from said activated-sludge-separating means;

said activated-sludge-separating means receiving said second aerobic culture from said second chamber, said activated sludge formed from separation in said activated-sludge-separating means by settling from said second aerobic culture in said activated-sludge-separating means, leaving a second effluent;

said first return means being a means for returning a first portion of the activated sludge from said activated-sludge-separating means to said first chamber to provide microorganisms as seed for said first aerobic culture in said first chamber;

said second return means being a means for returning a second portion of the activated sludge from said activated-sludge-separating means to said second chamber to provide microorganisms as seed for said second aerobic culture in said second chamber; and

said fluid discharging means being a means for discharging at least a portion of said second effluent from said activated-sludge-separating means to outside the apparatus, said second effluent so discharged to outside the apparatus being the treated wastewater.

30. The method of claim 29, wherein said first and second portions of said activated sludge are together substantially all of the activated sludge formed in said activated-sludge-separating means;

wherein at least about 90% of second effluent from said activated-sludge-separating means is treated water; and

wherein, in said treated water, the concentration of suspended solids is less than about 20% of the concentration of suspended solids in said first aerobic culture and the BOD is less than about 20% of the BOD of said first aerobic culture.

31. The method of claim 30, wherein the rate of return of activated sludge from said activated-sludge-separating means to said first and second chambers is substantially the same as the rate of production of activated sludge by settling from second aerobic culture in said activated-sludge-separating means.

32. The method of claim 31 wherein between about 3% and about 7% of the activated sludge from the activated-sludge-separating means is returned to said first chamber.

33. The method of claim 29 wherein the treatment apparatus comprises additionally a float-sludge-storing means, for receiving float sludge via the float-sludge-removing means from the float-sludge-separating means and holding until removed from the apparatus said float sludge so received, said float-sludge-storing means comprising a fourth aerating means for aerating float sludge held in said float-sludge-storing means to maintain said float sludge so held as aerobic sludge until removal from the apparatus.

34. The method of claim 33 wherein the apparatus comprises additionally a grease-trapping means for receiving the contaminated wastewater from the contaminated wastewater source and removing fat-based substances from the contaminated wastewater prior to entry of the contaminated wastewater into said first chamber.

35. The method of claim 34 wherein the first return means delivers the activated sludge returned from said activated-sludge-separating means into contaminated wastewater in said grease-trapping means, whereupon a combination of said activated sludge and contaminated wastewater passes from said grease-trapping means into said first chamber.

36. The method of claim 34 wherein the apparatus comprises additionally (i) a means for aerating said first effluent prior to receipt of said first effluent into said second chamber and (ii) means for filtering said second effluent prior to discharge of said second effluent as the treated wastewater to outside the apparatus.

37. The method of claim 36 wherein, in the apparatus, (i) said second chamber is an extended aeration chamber;

(ii) said activated-sludge-separating means is a clarifier;

(iii) said means for aerating said first effluent prior to receipt of said first effluent into said second chamber is a trickling filter tower; and

(iv) said means for filtering said second effluent prior to discharge to outside the apparatus is a sand filter, said method yielding treated wastewater with a concentration of suspended solids of less than 1% of said concentration in said first aerobic culture and a BOD of less than 1% of the BOD of said first aerobic culture.

38. The method of claim 34 wherein the contaminated wastewater source is a food-processing plant.

39. The method of claim 38 wherein the contaminated wastewater source is a milk-processing plant.

40. The method of claim 39 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

41. The method of claim 40 wherein the pH of said first aerobic culture is from about 8 to about 9.

42. The method of claim 41 wherein, in the first aerobic culture, the amount of suspended solids is from about 1200 mg/l to about 2400 mg/l and the BOD₅ is from about 2500 mg/l to about 6000 mg/l;

in the second aerobic culture, the amount of suspended solids is from about 2500 mg/l to about 4000 mg/l and the BOD₅ is from about 1200 mg/l to about 3600 mg/l; and

in the activated sludge, the amount of suspended solids is between about 2500 mg/l and about 5000 mg/l and the BOD₅ is between about 2000 mg/l and about 4000 mg/l.

43. The method of claim 42, wherein said first detention period is from about 12 hours to about 24 hours and said second detention period is from about 24 hours to about 96 hours.

44. The method of claim 38 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

45. The method of claim 29 wherein the contaminated wastewater source is a food-processing plant.

46. The method of claim 45 wherein the contaminated wastewater source is a milk-processing plant.

47. The method of claim 46 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

48. The method of claim 47 wherein the pH of said first aerobic culture is from about 8 to about 9.

49. The method of claim 45 wherein said first and second biological oxidizing means comprise filamentous bacteria of species selected from the Sphaerotilus-Leptothrix group.

50. The method of claim 29 wherein, in the apparatus, said first and second biological oxidizing means comprise filamentous microorganisms.

51. The method of claim 29 wherein, in the first aerobic culture, the amount of suspended solids is from about 1200 mg/l to about 2400 mg/l and the BOD₅ is from about 2500 mg/l to about 6000 mg/l;

in the second aerobic culture, the amount of suspended solids is from about 2500 mg/l to about 4000 mg/l and the BOD₅ is from about 1200 mg/l to about 3600 mg/l; and

in the activated sludge, the amount of suspended solids is between about 2500 mg/l and about 5000 mg/l and the BOD₅ is between about 2000 mg/l and about 4000 mg/l.

52. The method of claim 29 wherein said first detention period is from about 12 hours to about 24 hours and said second detention period is from about 24 hours to about 96 hours.

53. The method according to any of claims 29-43 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l.

54. The method of any of claims 29-43 wherein, in the wastewater treatment apparatus, the float-sludge-separating means comprises a means for combining an aqueous solution of a ferric salt with first aerobic culture received into said float-sludge-separating means and wherein an aqueous solution of a ferric salt is combined with first aerobic culture received into the float-sludge separating means.

55. The method of claim 54 wherein the ferric salt is selected from the group consisting of ferric sulfate, a ferric alum and ferric chloride.

56. The method of claim 55 wherein the ferric salt is ferric sulfate.

57. The method according to claim 56 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l and the concentration of phosphate in said first aerobic culture is from about 50 mg/l to about 100 mg/l.

58. The method according to claim 55 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l and the concentration of phosphate in said first aerobic culture is from about 50 mg/l to about 100 mg/l.

59. The method according to claim 54 wherein the concentration of dissolved oxygen in said first aerobic culture is from greater than 2 mg/l to about 8 mg/l and the concentration of phosphate in said first aerobic culture is from about 50 mg/l to about 100 mg/l.