Amendment-free sludge composting

Patent metadata

Field	Value
Publication number	US-9663392-B2
Application number	US-68858910-A
Country	US
Kind code	B2
Filing date	Jan 15, 2010
Priority date	Jan 16, 2009
Publication date	May 30, 2017
Grant date	May 30, 2017

Abstract

A composting system for promoting aerobic microbial activity in a composting bed. The system includes at least one composting bay for receiving composting material and an agitator for aerating and displacing composting material as it travels through the composting bay. Compost produced by the system is used in place of traditional woody amendment material for mixing with incoming material to be composted.

First claim

What is claimed is:

1. A method of sludge biodrying comprising:
providing a non-cellulosic first material consisting of one of finished compost, dried non-composted undigested sewage sludge having a dry solids content of between about 50% and about 95%, and a combination thereof;
providing a compostable sludge consisting essentially of undigested sewage sludge;
forming a mixed sludge consisting essentially of the first material and the compostable sludge mixed in a ratio of between about 2:1 and about 1:2 by weight when the first material consists of finished compost and in a ratio of between about 1:1 and about 1:2 by weight when the first material consists of dried non-composted undigested sewage sludge, the mixed sludge having a C:N ratio of less than about 15:1 by weight;
introducing the mixed sludge into a composting bay;
aerating the mixed sludge in the composting bay;
providing conditions for the mixed sludge to be maintained aerobically in the composting bay;
mechanically agitating the mixed sludge in the composting bay;
biodrying the mixed sludge with heat produced by a digestive action of microorganisms within the composting bay for a period of time sufficient to form a compost having a dry solids content of between about 50% and about 100% and a C:N ratio less than that of the mixed sludge introduced into the composting bay;
maintaining pH, temperature, and moisture content of the mixed sludge within ranges which suppress the formation of volatile ammonia from ammonium in the mixed sludge throughout the biodrying of the mixed sludge;
removing the compost from the composting bay; and
recycling a portion of the compost as the finished compost.

2. The method of claim 1 , further comprising removing particles below a predetermined size from the first material prior to forming the mixed sludge.

3. The method of claim 1 , wherein providing a source of a compostable sludge consists of providing a source of dewatered sewage sludge.

4. The method of claim 1 , further comprising removing moisture from the mixed sludge.

5. The method of claim 1 , wherein heating the mixed sludge comprises heating the mixed sludge to a temperature for a time sufficient to achieve destruction of pathogens within the mixed sludge.

6. The method of claim 5 , wherein heating the mixed sludge comprises maintaining a temperature of the mixed sludge of at least about 55° C. for a period of at least 72 hours.

7. The method of claim 5 , wherein the time and temperature at which the mixed sludge is treated satisfies the equation D=131,700,000/10 0.14t where, D=time in days; and t=temperature in degrees Celsius.

8. The method of claim 1 , wherein heating the mixed sludge comprises heating the mixed sludge to a temperature for a time sufficient to deactivate pathogens within the mixed sludge.

9. The method of claim 1 , wherein heating the mixed sludge comprises heating the mixed sludge to a temperature sufficient for Vector Attraction Reduction.

10. The method of claim 9 , wherein heating the mixed sludge further comprises heating the mixed sludge for a time sufficient for Vector Attraction Reduction.

11. The method of claim 10 , wherein heating the mixed sludge comprises heating the mixed sludge to a temperature of at least about 40° C. for at least 14 days.

12. The method of claim 1 , wherein a pH of the mixed sludge introduced into the composting bay is less than about 7.0.

13. The method of claim 12 , wherein the pH of the mixed sludge introduced into the composting bay is less than about 6.0.

14. The method of claim 1 , further comprising providing a portion of the compost removed from the composting bay as a combustible fuel.

15. The method of claim 1 , further comprising forming the compostable sludge from pre-screened wastewater.

16. The method of claim 1 , wherein agitating the mixed sludge comprises displacing the mixed sludge in the composting bay in a direction from a first end of the composting bay to a second end of the composting bay.

17. The method of claim 1 , further comprising sensing a temperature of the mixed sludge at at least one position in the composting bay.

18. The method of claim 17 , further comprising generating a signal in response to said temperature.

19. The method of claim 18 , further comprising receiving said signal at a controller.

20. The method of claim 19 , further comprising actuating a ventilation system to conduct air into the mixed sludge when the temperature thereof rises above a preset value.

21. The method of claim 19 , further comprising initiating an agitation of the mixed sludge when the temperature thereof falls below a preset value.

22. The method of claim 1 , further comprising sensing a moisture level of the mixed sludge at at least one position in the composting bay.

23. The method of claim 22 , further comprising generating a signal in response to the moisture level.

24. The method of claim 23 , further comprising receiving the signal at a controller.

25. The method of claim 24 , further comprising adding moisture to the mixed sludge when the moisture level thereof falls below a preset value.

26. The method of claim 24 , further comprising actuating a ventilation system to conduct air into the mixed sludge when the moisture level thereof rises above a preset value.

27. A method of sludge biodrying comprising:
providing a carbon containing first material;
providing a nitrogen containing compostable sludge;
forming a mixed sludge consisting essentially of the first material and the compostable sludge and having a C:N ratio of less than about 15:1 by weight;
introducing the mixed sludge into a composting bay;
maintaining an average C:N ratio of at least about 8:1 by weight in the mixed sludge in the composting bay;
providing conditions to facilitate the formation of compost from the mixed sludge;
removing the compost from the composting bay; and
recycling a portion of the compost as the first material.

28. The method of claim 27 , wherein the first material consists of heat dried undigested sewage sludge.

29. The method of claim 27 , wherein the nitrogen containing compostable sludge consists of dewatered sewage sludge.

30. The method of claim 27 , wherein the first material consists essentially of a non-cellulosic material.

31. The method of claim 27 , wherein the first material consists of compost removed from the composting bay.

32. The method of claim 27 , wherein forming the compost comprises:
aerating the mixed sludge in the composting bay;
mechanically agitating the mixed sludge in the composting bay;
providing conditions to facilitate a heating of the mixed sludge within the composting bay; and
reducing a moisture content of the mixed sludge within the composting bay.

33. The method of claim 27 , wherein the mixed sludge has a C:N ratio of less than about 15:1 when introduced into the composting bay.

34. The method of claim 27 , wherein the pH of the mixed sludge introduced into the composting bay is less than about 7.0.

35. The method of claim 34 , wherein the pH of the mixed sludge introduced into the composting bay is less than about 6.0.

36. A composting facility comprising:
a composting bay configured to receive organic waste mate

Assignees

• Nicoletti Richard M
• Naylor Lewis
• Evoqua Water Tech Llc

Inventors

• Nicoletti Richard M
• Naylor Lewis

Classifications

• C05F17/60

  Heating or cooling during the treatment · CPC title

• C05F17/20

  using specific microorganisms or substances, e.g. enzymes, for activating or stimulating the treatment (use of invertebrates C05F17/05) · CPC title

• C05F17/70

  Controlling the treatment in response to process parameters · CPC title

• C05F17/40

  Treatment of liquids or slurries · CPC title

• C05F17/90

  Apparatus therefor · CPC title