Waste collection system and method for separating liquid waste from solid waste

Abstract

A waste separation system and a method of separating liquid waste from solid waste employ an animal waste conveyor comprising an endless conveyor belt extending around upper and lower conveyor rollers and having an upwardly concave longitudinally inclined upper run which, in transverse cross-section, has a lowermost portion forming a liquid drainage channel extending longitudinally of the upper run and lateral portions diverging laterally and upwardly from the liquid drainage channel. The solid and liquid waste is discharged onto the upper run, so that the liquid waste flows under gravity into and along the liquid drainage channel to be discharged and collected in the vicinity of the lower end of the conveyor, and the conveyor is intermittently driven to discharge the solid waste material from the conveyor to be separately collected.

Description

CROSS-REFERENCE TO RELATED APPLICATION

This application is a continuation of U.S. patent application Ser. No. 11/201,094, filed Aug. 11, 2005.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to a waste collection system and a method for separating liquid waste from solid waste.

2. Description of the Related Art

In modern agricultural production, it has become usual to employ an agricultural establishment as an intensive feeding operation for raising hundreds or even thousands of animals, e.g. hogs, dairy, poultry and beef animals, at a single location. Consequently, large amounts of animal waste matter are produced at such locations, and the disposal of this waste matter in a hygienic and inoffensive manner can be problematic.

It has, for example, been planned to initiate a hog farm containing 2,000,000 hogs, which will produce an amount of waste equivalent to that produced by the city of Los Angeles. The current pig population of North Carolina is four times that number. Recent accidents in North Carolina, in which millions of gallons of pig excreta were released into the countryside, have drawn attention to the problems involved in the disposal of such waste. Applications for permits to construct large piggeries have been denied because of concerns about odours and waste disposal.

Animal waste, including hog manure, has traditionally been disposed of by spreading it over agricultural land as a liquid fertilizer and, for sufficiently large cropped land bases, this method of disposal can be performed safely. However, in areas of high population density or where multiple farms are closely clustered, and the land base is therefore relatively small, problems arise. For example, excess nutrients cannot be absorbed by crops and leach into ground water and surface water.

When land application is prevented, e.g. because the ground is frozen or saturated with water and/or nutrients, the waste must be stored, usually in large pits, with consequential costs and environmental risk.

As an alternative to land disposal, it is also common practice to compost the waste. For this purpose, the waste is separated into solid and liquid by the use of inclined screens, sometimes followed by the use of belt or filter presses. These methods produce an output containing about 45% solid material at best, and this is then mixed with a bulking material to facilitate aeration and an appropriate C:N ratio, and deposited in windows for stabilization, over a period of about 45 to 60 days, by composting. This process does not ensure that pathogens in the waste are killed and the windows are often odorous and may attract birds, rodents and vermin. The liquid still has to be dealt with through land application. As such, composting does not reduce the need for land application or land area.

The challenges involved in the treatment of animal waste include the destruction of pathogens, the controlled extraction of ammonium and plant nutrients, and the disposal of organic matter.

It is known to collect waste from animal barns by discharging the waste through openings in the barn floor onto a conveyor belt located in a gutter below the barn floor. The conveyor belt carries the waste to a collection point, and the waste may then be taken to a waste processing facility or the waste may be processed on site.

However, the liquid waste and solid waste are not separated and over time the mixing of liquid waste and solid waste impedes the processing of the waste. Furthermore, the mixing of the liquid waste and solid waste may cause the release of gases which are harmful to humans, animals and the environment.

In U.S. Pat. No. 6,916,426, the disclosure of which is herein incorporated by reference, there was disclosed an invention based on an appreciation of the fact that the extraction of nitrogen, potassium and phosphorous from animal waste material is substantially enhanced if the treatment is performed promptly after the production of the waste material by the animals. More particularly, the aforesaid U.S. Pat. No. 6,916,426 disclosed a method of processing animal waste in which liquid waste and solid waste are separated, preferably within 12 hours following the production of the waste by the animals, and the liquid waste is processed preferably within 24 hours of the production of waste by the animals.

Potassium is present in animal waste material in the form of an insoluble potassium urate, and it was found that a substantial amount of the potassium in animal waste material can be extracted in a solid form, as potassium urate, before microbial action breaks down the potassium urate to leave potassium and ammonium in solution. Extracted urates are then available for inclusion in a fertilizer. When the fertilizer is used on land, the microbes in the soil break down these urates, releasing the potassium and ammonia, but at a rate less than that at which these nutrients would be released in the soil if dissolved in water.

Consequently, by extracting ammonium-nitrogen and potassium in the form of urates and/or other compounds from the waste material while they remain in solid, e.g. crystalline form, i.e. before they break down to release these substances, a substantially improved extraction of these substances can be achieved. Therefore, the solids and liquids should be separated as soon as possible after their production by the animals.

BRIEF SUMMARY OF THE INVENTION

It is therefore an object of the present invention to provide a waste collection system in which liquid waste may be rapidly separated from solid waste and collected, following the production of liquid and solid waste by the animals.

According to one aspect of the invention, there is provided a waste collection system for separating liquid and solid waste, including an endless imperforate conveyor belt supported by upper and lower rollers, the conveyor belt having an upper run longitudinally downwardly inclined from the upper roller to the lower roller, and a support underlying the upper run and defining the cross-sectional shape of the upper run as an upwardly concave shape in the transverse direction of the upper run. The concave shape has first and second laterally inclined portions connected by a lowermost portion and the lowermost portion forms a longitudinally inclined liquid drainage channel extending longitudinally of the upper run. A liquid waste collector is located beneath the conveyor belt in the vicinity of the lower conveyor roller, and a solid waste collector is located beneath one of the conveyor rollers, a conveyor drive being connected to one of the conveyor rollers.

In operation of the present waste collection system, animal waste is discharged onto the lateral portions of the upper run. Liquid waste, i.e. animal urine, from the animal waste flows into the liquid drainage channel, while solid waste remains distributed along the lateral portions. The liquid waste flows along the liquid drainage channel of the longitudinally inclined upper run of the conveyor to the lower end of the conveyor, where it is collected in the liquid waste collector.

The solid waste remains on the lateral portions of the conveyor belt surface until the conveyor drive is actuated and the solid waste is then carried to an end of the conveyor where it is collected in the solid waste collector. An air current may also be drawn along the upper run to help dry the solid waste.

Also according to the present invention, there is provided a method of separating liquid waste from solid waste comprising the steps of providing an animal waste conveyor having a lower end, an upper end and an endless conveyor belt with an upwardly concave longitudinally inclined upper run, forming the upper run into an upwardly open cross-sectional shape having, in transverse cross-section, a lowermost portion forming a longitudinally inclined liquid drainage channel and lateral portions diverging laterally and upwardly from the lowermost portion, discharging waste onto the upper run, allowing the liquid waste material to flow under gravity into the liquid drainage channel and along the liquid drainage channel from the upper run of the conveyor belt, collecting liquid waste in the vicinity of the lower end of the conveyor, driving the conveyor to discharge the solid waste material from the conveyor; and collecting the solid waste material discharged from the conveyor separately from the collected liquid waste.

BRIEF DESCRIPTION OF THE DRAWINGS

The invention will be more readily understood from the following description of embodiments thereof given, by way of example only, with reference to the accompanying drawings, in which:

FIG. 1 is a diagrammatic longitudinal view showing a waste collection system according to an embodiment of the invention;

FIG. 2 is a diagrammatic longitudinal view showing a waste collection system according to another embodiment of the invention;

FIG. 3 is an enlarged diagrammatic side view, partly in cross-section, showing the lower end of the conveyor of the waste collection system of FIG. 2;

FIG. 4 is a diagrammatic view taken in transverse cross-section through the waste collection system of FIG. 1; and

FIG. 5 is a fragmentary diagrammatic view taken in transverse cross-section through a waste collection system according to yet another embodiment of the invention.

DESCRIPTION OF THE PREFERRED EMBODIMENT

Referring to FIG. 1, there is shown a waste collection system indicated generally by reference numeral 10. In this embodiment of the invention the waste collection system 10 includes an animal waste conveyor indicated generally by reference numeral 12. The conveyor 12 comprises a lower roller 14, an upper roller 16 and an endless conveyor belt 13 extending around the rollers 14 and 16. The conveyor belt 13 has a upwardly concave upper run 18 which is longitudinally downwardly inclined to the lower roller 14. A liquid waste collector 20 is located beneath a lower end 27 of the conveyor, in the vicinity of the lower roller 14. A solid waste collector 22 is located beneath an upper end 29 of the conveyor 12, in the vicinity of the upper roller 16. In this embodiment of the invention, the solid waste collector 22 is an upwardly open container or bin. However, in other embodiments of the invention, the solid waste collector may alternatively be a second conveyor.

As best shown in FIG. 4, in this embodiment of the invention, the conveyor 12 is located in a gutter 30 underneath an animal barn floor indicated generally by 70. The upper run 18 spans the width W of the gutter 30 and divides the gutter 30 into an upper portion indicated generally by reference numeral 38, and a lower portion indicated generally by reference numeral 39. A first sealing member 40 extends the length of a first gutter wall 35, and a second sealing member 45 extends the length of a second gutter wall 37 which is opposite to the first gutter wall 35. The sealing members 40 and 45 have upper lips 42 and 47, lower lips 43 and 48, and grooves 44 and 49 between the upper lips 42 and 47 and the lower lips 43 and 48, respectively. Opposite longitudinal edges 26 and 28 of the upper run 18 are received by the grooves 44 and 49, respectively, thereby substantially sealing the upper run 18 against the gutter walls 35 and 37 and substantially preventing fluid and air flow between the upper portion 38 and lower portion 39 of the gutter 30.

The underside of the upper run 18 rests upon a support in the form of a mesh formed by transversely extending support members 50 and support rods 51 extending longitudinally of the upper run 18. The support rods 51 are spaced apart in a manner such that the upper run 18 rests in an upwardly concave configuration that is Vee-shaped in transverse cross-section. The upper run 18 consequently has first and second lateral portions, indicated generally by reference numerals 60 and 62, which are angularly spaced apart and extend upwardly. The lateral portions 60 and 62 are divergently inclined in opposite lateral directions from a lowermost portion 64 of the upper run 18. The lowermost portion 64 forms a longitudinally inclined liquid drainage channel extending longitudinally of the upper run 18. An elongate member 52, in the form of a cable, rests on the lowermost portion 64 of the upper run 18 and extends longitudinal along the lowermost portion 64 of the upper run 18. The elongate member 52 guides the flow of liquid waste along the lowermost portion 64.

An air extraction ductwork 80 communicates with the upper run 18 and has an extractor fan 81 which draws an air current over the conveyor belt and out of the gutter 30, as indicated generally by arrows 82 and 84.

The barn floor 70 has a plurality of animal waste discharge openings in the form of slots 71 separated by solid flooring portions 73 and 74. The slots 71 directly expose areas of the upper run 18 to the barn environment. The solid portions 73 and 74 cover areas of the upper run 18 from direct exposure to the barn environment.

This embodiment of the waste collection system functions as follows:

Referring to FIG. 4, waste is discharged from the barn through the slots 71 in the barn floor 70 and onto the upper run 18 as indicated generally by arrow 75. However, the flooring portion 74, which is wider than the flooring portion 73, forms a waste deflector which extends longitudinally of the upper run 18 above and along the lowermost portion 64. The flooring portion 74 covers the lowermost portion 64 of the upper run 18, and deflects the waste from falling through the floor 70 onto the lowermost portion 64 of the upper run. The waste is therefore discharged solely onto the lateral portions 60 and 62 of the upper run 18.

In this embodiment of the invention, the upper lips 42 and 47 of the sealing members 40 and 45 substantially prevent waste from being discharged downwardly past the edges 26 and 28 of the upper run 18. As will be apparent to those skilled in the art, it is alternatively possible to employ, in other embodiments of the invention, flashings such as flashing 61 shown in FIG. 5, to prevent waste from being discharged downwardly past the longitudinal edges of the upper run 18. In FIG. 5, parts corresponding to those of FIGS. 1 and 4 have been given like reference numerals with the additional numerical designation “.2”.

Referring back to FIG. 4, the lateral portions 60 and 62 of the upper run 18 are laterally upwardly inclined relative to the lowermost portion 18, with a slope of between 2% and 6%, and preferably 4%. This slope causes the liquid waste to flow under gravity across the lateral portions 60 and 62 into the lowermost portion 64 as indicated by arrows 77. The solid waste remains distributed along the lateral portions 60 and 62 of the upper run 18. As a result, this embodiment of the invention offers the advantage of rapid separation of the liquid waste from the solid waste.

Referring now to FIG. 1, because the upper run 18 of the conveyor 12 is longitudinally inclined, preferably with a longitudinal slope of between 0.1% to 2.0%, the liquid waste flows under gravity along the liquid drainage channel formed by the lowermost portion 64 of the upper run 18 to the lowermost end 27 of the conveyor 12 as indicated generally by arrow 91. At the lowermost end 27 of the conveyor 12, the liquid waste is discharged from the conveyor 12 as indicated by arrow 93 and collected in the liquid waste collector 20. As a result, this embodiment of the invention ensures rapid and substantially immediate separation of the liquid waste from the solid waste and continuous collection of the liquid waste.

The conveyor 12 generally remains stationary as the liquid waste is collected, thereby allowing the solid waste to dry in a fixed position for a desired period of time. In this embodiment of the invention, an air current drawn across the upper run 18 by the extraction fan 81 accelerates this drying process. After the solid waste has been allowed to dry for a desired period of time, the conveyor 12 is driven by a drive motor 100 connected by a belt and pulley connection 101 to the upper roller 16 at the uppermost end 29 of the conveyor 12 for driving the conveyor 12 in the direction generally indicated by arrow 110. The solid waste is thus carried along the conveyor 12 to the uppermost end 29 of the conveyor 12 where it is discharged from the conveyor 12 into the solid waste collector 22. Movement of the solid waste along and from the conveyor 12 is indicated generally by arrows 95 and 97.

Now referring to FIG. 2, wherein parts corresponding to those of FIGS. 1 and 4 have been given like reference numerals with the additional numerical designation “.1”, a waste collection system is shown according to another embodiment of the invention. The waste collection system is indicated generally by reference numeral 10.1, which includes a conveyor 12.1 having a lowermost end 27.1 and an uppermost end 29.1 and an endless belt 13.1 having an upper run 18.1 which is longitudinally downwardly inclined from an upper roller 16.1 at the uppermost end 29.1 to a lower roller 14.1 at the lowermost end 27.1.

As shown best in FIG. 3, in this embodiment of the invention, a liquid waste collector 20.1 and a solid waste materials collector 22.1 are located beneath the lowermost end 27.1 of the conveyor 12.1. The liquid waste collector 20.1 is within the solid waste collector 22.1. A scraper 15 acts on the lowermost end 27.1 of the conveyor belt 12.1. A drive motor 100.1 is connected by a belt and pulley connection 101 to the lower roller 14.1 at the lowermost end 27.1 of the conveyor 12.1 for driving the conveyor 12.1 in the direction generally indicated by arrow 109.

In this embodiment of the invention, both liquid waste 25 and solid waste 23 are conveyed to the lowermost end 27.1 of the conveyor 12.1. The liquid waste 25 flows around the lowermost end 27.1 of the conveyor 12.1, as indicated generally by arrow 107, and is deflected into the liquid waste collector 20.1 by the scraper 15. When the conveyor 12.1 is intermittently driven by drive motor 100.1 solid waste from the lowermost end 27.1 of the conveyor 12.1 falls, as indicated generally by arrow 105, into the solid waste collector 22.1.

As will be apparent to those skilled in the art, various modifications may be made in the above-described embodiment of the present invention within the scope of the appended claims.

Claims

1. A waste collection system for separating liquid and solid waste, comprising:

an animal waste conveyor;

the animal waste conveyor comprising an upper conveyor roller, a lower conveyor roller and an endless conveyor belt extending around the upper conveyor roller and the lower conveyor rollers;

the conveyor belt having an upwardly concave upper run which is longitudinally inclined from the upper conveyor roller to the lower conveyor roller;

the upper run having, in cross-section, a lowermost portion forming a longitudinally inclined drainage channel extending along the upper run and lateral portions diverging laterally and upwardly from the liquid drainage channel;

a liquid waste collector located beneath the lower conveyor roller;

a solid waste collector located beneath one of the upper and lower conveyor rollers; and

a conveyor drive connected to the animal waste conveyor.

2. A waste collection system as claimed in claim 1, including a support underlying the upper run and defining the cross-sectional shape of the upper run.

3. A waste collection system as claimed in claim 2, wherein the support comprises support members extending longitudinally of the upper run.

4. A waste collection system as claimed in claim 2, wherein the support has a Vee-shaped cross-section.

5. A waste collection system as claimed in claim 1, wherein the upper run of the conveyor belt has a longitudinal slope of 0.1% to 2.0%.

6. A waste collection system as claimed in claim 1, wherein the lateral portions of the upper run of the conveyor belt each have a slope, transversely of the upper run, of 2.0% to 6.0%.

7. A waste collection system as claimed in claim 1, wherein the lateral portions of the upper run of the conveyor belt each have a slope, transversely of the upper run, of 4.0%.

8. A waste collection system as claimed in claim 1, wherein the drive is intermittently operable to drive the upper run of the animal waste conveyor towards the upper conveyor roller.

9. A waste collection system as claimed in claim 1, including a floor extending above the animal waste conveyor, the floor having openings extending downwardly and through the floor to allow the liquid and solid waste to fall through the floor onto the upper run of the animal waste conveyor, and a portion of the floor being uninterrupted by the openings to form a waste deflector extending along and above the liquid drainage channel.

10. A waste collection system as claimed in claim 1, wherein the solid waste collector is located in the vicinity of the upper conveyor roller.

11. A waste collection system as claimed in claim 1, wherein the liquid and solid waste collectors are both located in the vicinity of the lower conveyor roller.

12. A waste collection system as claimed in claim 1, including a gutter containing the animal waste conveyor, the gutter having opposed walls and the animal waste conveyor being located between the opposed walls, and a sealing means for sealing opposite edges of the upper run against the opposed walls.

13. A waste collection system as claimed in claim 1, including a flashing preventing the liquid and solid waste from being discharged downwardly past longitudinal edges of the upper run.

14. A method of separating liquid waste from solid waste comprising the steps of:

forming an upper run of an animal waste conveyor into a longitudinally inclined liquid drainage channel extending along the upper run and lateral portions diverging laterally and upwardly from the liquid drainage channel;

discharging the liquid and solid animal waste onto the upper run so that the liquid waste is drained under gravity into and along the liquid drainage channel and discharged from the animal waste conveyor;

collecting liquid waste discharged from animal waste conveyor;

driving the animal waste conveyor to discharge the solid waste material from the animal waste conveyor; and

discharging and collecting the solid waste material from the animal waste conveyor separately from the liquid waste.

15. A method as claimed in claim 14, which further includes the step of deflecting the solid waste from being discharged into the liquid drainage channel of the upper run.

16. A method as claimed in claim 14, which further includes the step of supporting the underside of the upper run so as to define the cross-sectional shape of said upper run.

17. A method as claimed in claim 16, in which the step of supporting the underside of the upper run comprises slidingly supporting the upper run.

18. A method as claimed in claim 16, in which the step of supporting of the underside of the upper run includes providing the upper run of the conveyor belt with a longitudinal slope of 0.1% to 2.0%.

19. A method as claimed in claim 16, in which the step of supporting of the underside of the upper run includes providing the lateral portions of the upper run of the conveyor belt with a slope, transversely of the upper run, of 2.0% to 6.0%.

20. A method as claimed in claim 16, in which the step of supporting of the underside of the upper run includes providing the lateral portions of the upper run of the conveyor belt with a slope, transversely of the upper run, of 4.0%.

21. A method as claimed in claim 14, in which the step of the driving of the animal waste conveyor is effected intermittently.

22. A method as claimed in claim 21, further including the step of drying the solid material on the upper run while the animal waste conveyor is stationary.

23. The method as claimed in claim 14, in which the step of collecting the solid waste comprises collecting the solid waste in the vicinity of a lower end of the animal waste conveyor.

24. The method as claimed in claim 14, in which the step of collecting the solid waste comprises collecting the solid waste in the vicinity of an upper end of the animal waste conveyor.

25. The method as claimed in claim 14, further including the step of drawing an air current along the upper run of the animal waste conveyor.