CA1103590A - Conversion of animal waste - Google Patents

Abstract

ABSTRACT OF THE DISCLOSURE
Dry and liquid feed supplements are recovered from treating animal wastes collected from a confinement feeding area for livestock and the like by a closed loop type of collection system including a primary liquid storage tank. Solids and liquids are separated from the collected wastes by dynamic liquid filtering apparatus including a unique compression filter. Liquid is withdrawn near the surface of the primary tank, passed through a second solid/liquid separating filter and transferred to a secondary tank. Preferably rarified oxygen is forced into both tanks so as to aerate the liquids. After appropriate aerobic digestion or oxidation, the secondary tank liquids are used to supplement feed water and the solids are used to supplement dry feed ration.

Description

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This application is divided out of copending Canadi~n application No. 260,809, filed September 9, 1976.
This invention relates to methods and apparatus for recovering livestock feed supplements from animal wastes. More particularly, the present ;
invention relates to methods and apparatus for separating the solids and liquids from animal wastes from a flush-type facility and the treatment of these separated materials in a manner suitable for recycling as animal feed supplements. The present invention is particularly use~ul for confinement ~eeding facilities such as for feeding of livestock.
As evidenced in recent years the world demand or feedstuffs, usually considered to be livestock feed ingredients, has outs~ripped supply at least at historic price levels. As the world population continues to in-crease, and the living standards of these populations also increases, upward price exertions will remain on those feed ingredients for which livestock and people dlrectly compete. All phases of the cattle producing industry have been continually cost-price sensitive. The cost of energy, roughage and protein sources available to the cattle industry have significantly increased and the value of the finished product has been drastically reduced.
It is imperativ~ that production costs be reduced by lower ingredient costs or improving efficiencies.
The concentration of production and availability of feed grain and cellulose in certain geographical areas such as the so-called Corn Belt of the United States indicates an economic advantage in raising and feeding livestock in those areas. For various reasons such as protection from climatic hazards, it is particularly attractive to feed such livestock in confinement. Wherever there is proximity to more densely populated areas, the control of air and water pollution relative ~o such confinement feeding ' -: , , , , ,, , ,: , .: ': ~ i : ' ~ : : : ' ' : :

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systems is further important particularly relative to the waste handling and treatment. Thus, it is attractive to provide systems which permit recycling of the wastes as animal feed supplements.
Certain classes of livestock are much more ineficient users of feedstuffs than others. For instance, beef cattle on a fattening ration require a~ least seven pounds of ration (10% moisture) to produce one pound of gain. According to the National Academy of Science investig~tions on nutrient requirements of beef cattle, beef cattle require an equal amount of energy for production and body maintenance if they are performing at a near optimal level. Tllerefore, only 28 1/2% of all of the eed consumed by beef cattle on a fattening ration is actually utilized. The remainder is passed through in the form of animal excrement.
Livestock waste continues to represent a major problem to society and to the livestock feeding industry. To comply with pollution regulations, many livestock operators have improved their facilities to meet these re-quirements, but their produc~ion costs have also increased. The most practi-cal solution to the problems of pollution and increased ration costs is to reclalm, process and recycle the waste from cattle that are being fed in confinement feed lot facilities. Accordingly, various efforts have been directed towards waste recycling in the agricultural industry. For many years cattle feeders have allowed swine to follow cattle in the feed lot. The purpose of this practi.ce was to allow swine to recover a portion of the un-digested sollds from the cattle waste and convert ~hem into pork. Consider-able research, and practical application, has been conducted in the area of recycling poultry waste litter through other classes of livestock. Further, one system ~or producing feed supplements from poultry is shown in United States Patent No. 3,831,288 by Stribling et al.

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During recent years many research projects have been conducted to measure the performance of beef cattle that were fed a ration that con-tains processed beef cattle waste as a portion of their ration. The pre-mise behind these research tests was to substitute not only energy, but all or a portion of the protein in the ration with protein derived from beef cattle waste. It would appear that feedlot cattle waste when properly collected and processed can be included to make up a part of cattle rations and the performance of cattle on feed is not adversely affected.
Numerous chemical tests have been conducted on feedlot cattle waste to determine levels of protein, ~ry matter digestibility, calcium, etc.
Such research has determined that the amount of protein in fresh feedlot cat~le excrement was 6.01%. When converted to a dry matter basis this excre-ment contained 30.74~ protein.
Assuming that an 850 pound steer consumes 21.50 pounds of air dry ration ~10% moisture) per day, along with a 28 1/2% utilization factor, only 5.50 pounds of a typical "hot feedlot ration" is utilized by the animal.
The remainder of the ration, 13.85 pounds, is passed through in the excrement.
`As shown in certain "in-vitro" tests, about 70% of the dry matter in this portion of the ration passed through the animal undigested. On a dry matter analysis the digestibility of cattle excrement compares favorably to typical corn silage.
Recent research conducted at Iowa State University has shown that cattle performance when fed ensiled waste excrement is equal to the per-formance of cattle that were fed whole-plant corn silage. Thus, there is a tremendous economic potential to the confinement cattle feeding industry if the undigested solid portion of the ration is reclaimed.
Summarizing, various efforts have been applied to recover the ,, , ,, . . . .. , ~, ~ ",,.; ":/", " :: , ",: ,, 35~

food value from the ~nimal wastes as supplements. For confinement cattle feeding barns~ there are further a variety of flushable flume configurations for recovering wastes such as are shown iTI United States Patent Nos.

2,233,766 by Bogert, 3,137,270 by Rigertin~ et al and 3,530,831 by Conover.
Further, oxidation of these wastes such as through intensive aeration in storage reservoirs has been pursued. Various methods of inducing air into such collected wastes have also been used. Some research has indicated that Up to 50% of the animal wastes from feedlot cattle can be recycled as food supplements except for the final month or two before marketing. Various processes of treatment and silage storage have been suggested, and the re-covered silage ration indicates weight gains comparable to cattle fed on whole corn silage ration supplemented with various other additives. Some examples of treatment and separation systems can be found in United States Patent Nos. 2,270,869 by Ditto et al, 3,462,275 by Bellamy and 3,633,547 by Stevens et al. The Stevens et al patent shows a closed loop type confine-ment feed mg system wherein fermented and sterilized solids are automatically added to the feed slurry.
Accordingly, it is a primary object of the present inVeTltiOn to provide a method and apparatus for recovering animal feed value from animal wastes.
According to one aspect of the present invention there is provid-ed apparatus for separating solids and liquids rom a mixture thereof compris-ing:
screen means having an upper substantially flat surface oriented at an angle for permitting gravitational flow of said mixture over said surface, means for introducing said mixture to the upper portion of said _ ~ _ ., ~

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screen means surface, said flat surface of said screen means being formed by a plurality of parallel bars arranged in a spaced relation for defining a plurality of transverse slots, the width of said slots being arranged to ac- ;
commodate passage of the liquid from said mixture therethrough while blocking passage of the solids from said mixture, liquid filter meansJ
means receiving said mixture from the lower portion of said screen meanS for compressing said mixture against said liquid filter, and means for receiving the liquids passing through said screen means and said liquid filter means whereby the mixture after passing over said screen means as a result of the gravitatlonal flow and after being compressed against said liquid filter means will have a reduced liqui.d content.
According to another aspect of the invention there is provided apparatus for separating solids and liquids from a mixture comprising:
a cylindrical drum means, means for imparting rotary motion to said drum means, filter means arrayed around the lower peripheral area of said drum means, said filter means including a plurality of spaced bars arranged for forming an arcuate surface in surrounding relation relative to the lower peripheral area of said drum means, porous endless belt means arranged to move against said spaced bars and said drum means for compressing said mixture against said drum me~ns, means introducing said mixture between said drum means and said filter means at the point the peripheral edge of said drum means is rotation~
ally moving downward for compressing said mixture between said drum means and said filter means, and means for collecting the liquid passing through said endless belt i ~3~
and the spaces between said spaced bars, whereby the liquid fTom said mix-ture will pass through said filter means while solids will pass between said drum and the endless belt means and will be discharged at the peripheral edge of said drum when said drum is moving upward.
Further objects, advantages and features of the present invention will be more readily apparent in view of the following detailed description of a preferred embodiment.
Figure 1 illustrates an arrangement for livestock feed supple-mentation recovery in accordance with the present invention relative to a con-finment feeding facility.
Figure 2 is a partially cross-sectional view of the press roll separator shown in Figure 1.
Figure 3 is a front view of the press roll separator of Figure 2.
Figure 4 shows a partially sectioned view o the apparatus of Figure 2 taken along section line 4-4.
Figure 5 shows the detail of the interrelationship of the drum, belt and wedge wire basket of Figures 2, 3 and 4.
Figure 6, on the same sheet as Figures 2 and 3, is a section view ~ of a typical wedge wire section taken along line 6-6 of Figure 3; and Figure 7 shows the detail of an aerator system.
The present invention is preferably useful in conjunction with flush type livestock confinement barns and will be described in detail rela-tive to a typical such barn 28 but it is to be recognized that the invention is not limited to the confinement barn configuration as shown. Fresh water is introduced at pipe 10 and the system is initialized by filling primary aeration tank 11 therefrom. Tank valve 12 is provided for allowing water iTito tank 11, which will eventualIy become the liquid portion of the wastes ., , ;,. . ~ : : : . - . -: . :,: . : . : :: : .. .

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recycling system. Further) ~he content of tank 11 flows by gravity through underground pipe 13 to the upper end of the confinemen~ feeding barn. The effluent from tank 11 enters the bottom o~ the splitter box 14 to be divided into as many parts as there are flumes or surge tanks 15. Flumes 15 can be continuously or periodically flushed clean by flooding either sequentially or all at once as desired.
The liquid from flumes 15 flows to the lower end of the barn by gravity feed and carries the wastes to the sump 16. Sump pump 17 pumps the wastes through pipe 18 to the wedge wire filter appara~us 19 where much of the liquid is removed. The solids gravitate down the screen to the rotary press 20. Press 2~ extracts more liquid from the solid portion of the wastes and discharges the solids at approximately 6S% moisture into the solids hold-ing bin 21. The liquid portion of the wastes flows through pipe 22 back into primary aeration tank 11 for aerobic treatment. Overflow from tank 11 flows over the additional wedge wire screen filter 23. Wedge wire screen filter 23 typically is a screen with approximately .005 inch openings between solid wedge shaped bars. The small opening slots of such a screen remove most of the liquid from the remaining solids from the overflow of tank 11 and these solids will be primarily inert since they have been aerobically digest-ed in tank 11. These solids are likewise discharged into holding bin 21.
The liquid flows from screen filter 23 through pipe 2~ into a final aeration tank 2~5. Fresh water from source 10 can also be piped into tank 25 through fresh water line 26 and a level maintained constantly in tank 25 by a conven-tional float valve 27.
Sloped wedge wire screens for liquid separation by gravity feed have been applied in several industries. A variety of such screens are com-mercially available. As applied in conjunction with this invention, the '~L~35~
screen size may vary depending upon such factors as the type of animal involv-ecl, the type of ration being fed to the animals, etc. For a typical cat~le feeding environment, the screen for filter 19 typically will have .010 inch spacings between bars with the flat surface of such bars being approximately

3/16 inch and the thickness of the bars in the top screen being approximately 1/4 inch.
In a typical configuration such as for supporting abou~ five hu~dred s~eers, tank 11 and tank 25 extend approximately 11' and 9', respec-tively, above the surface of the confinement area. This allows enough head pressure to flush the barn by gravity flow from tank 11 and also provides enough head pressure from tank 25 to force the aerobic treated waste liquids mixed with fresh water to the automatic livestock waterers in the barn (not shown~ .
As shown in Figure 7, the aerators installed in tanks 11 and 25 utilize high volume, low pressure pumps 30 with the impeller mounted horizon-tally. The power shaft 31 runs vertically from the bottom of each tank ~o the surface or top of the aeration tanks 11 and 25 where electric motors 32 are mounted for belt driving pulleys such as 33 and thus drive power shaft 31. The llquid is received into the pump from the center of both top and bottom of the housing of pump 30 which is positioned slightly above the bot-tom of the tank. The liquid is forced through the pump discharge 34, the flow is split and forced through two venturi units 35 and 36, air is supplied to these venturis through a plastic pipe 38 that extends from the bottom of a tank to above the liquid surface as shown in Figure 7. Air pump 40 drives the air into plenu~ chamber 41 where it is appropriately split and introduced to pipes 38 and 42, the latter terminating in a similar venturi assembly in tank 25. The air is broken up and dispersed into the liquid by means of ~3~

diffusers ~5 and 46. Due to the depth of the pump and baffles in the tank (not shown), the air is retained in the liquid to transfer a high percent of the oxygen into the liquid. It has been found that 10 cubic feet of air per minute per horsepower can be put ~hrough the venturis with nearly 75% of the oxygen transferring into the liquid of this type of application.
It should be noted that the air intake into air pump 40 of Figure 7 is advantageously supplied by an Aran generator 39 which is somewhat similar to an ozone generator. The main difference is that Aran is composed of four and five oxygen atoms per molecule instead of three oxygen atoms as ~ -in Ozone. The advantage of using Aran generator 39 is that the efficiency of transfer of o~ygen into the liquid in the storage tank is significantly enhanced since Aran and Ozone which are actually both produced by generator 39 are highly unstable. A still further advantage of using Aran is that it provides a sterili~ation effect as it is introduced into the tanks via the ventllris. This can be further controlled by the plenum 41 which splits the flow from blower 40 and Aran generator 39. Note that air duct pipes 38 and 42 which extend from~above the surface of the tanks to the venturis (35 and 36) on the pumps can under some circumstances be all that is needed to supply the air flow to satisfy the reduced pressure created in the venturi. However, blower 40 between generator 39 and plenum chamber 41 can be arranged to main-tain positive static air pressure such as by pumping ~15 cubic feet per minute .md maintaining a static pressure of 3 inches. Thus the system not only satisfies the venturi vacuum but, by the positive pressure, potentially doubles the amount of air induced into the liquid. This could result in re-ducing the horsepower demand on pumps 30% by 50% since the purpose of pumps 30 is to induce air and oxygen into tanks 11 and 25.
In the system thus descrlbed, every precaution is taken to conserve _ g _ -. ., ~ ,: , ;: , " :: . ;: :, . : :

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the wastes being removed from the confinement feeding facility. The waste is flushed from the flumes with aerobic material from the primary aerator tank 11 on a continuous basis. The solids are separated and removed in a matter of minutes and made available to be put into a silo for fermentation from storage bin 21. After the solids portion of the waste has been placed in a silo and allowed to ferment for typically twenty-one to twenty-eight days, the pro-pionic, acetic an~ lactic acids which evolve in the ensiling or fermentation process of such materials tends to enhance the digestibility and palatability for potential recycling or feeding.
The unique filter and rotary press combination shown generally in Figure 1 is particularly advantageous for separating solids from liquids and illustrated in greater detail in Figures 2-6. This rotary press is particular-ly advantageous for this application since it is relatively simple but still economical and efficient in operation. As seen in Figure 2, the discharge from pipe 18 from sump pump 17 is introduced to chamber S0 until it reaches the apex of solid back wall 51 and overflows down wedge wire screen 19. ~s can be seen in Figures 2~ 3, and 6, wedge wire screen 19 is composed of a series of wedge-shaped horizontal bars such as 47 and 48 with a small lateral gap 49 therebetween. Typically, bars 47 and 48 have an upper surface of 3/16 inches which are separated by 0.010 inches of open space, e.g. gap 49.
Thus, as reservoir 50 overflows so that waste material 43 flows down the face of screen 19~ the liquids will be permitted to enter collection chamber 52 and eventually escape from pipe 22 back into ae~rator tank 11 (note Figure 1).
Eventually the materials sliding down the surface of screen 19 will reach rotary spreader wheel 53 which rotates as indicated against the Elow of the materials and prevents jamming against the drum 54.
Drum 54 is arranged in proximity to an endless belt 55 which ~35~

typically is a nylon material. By applying rotary power to drum 54~ ma~erials which reach the bottom o screen 19 are squeezed between ~elt 55 and drum 54, thereby removing further moisture for collection in chamber 52. By making belt 55 somewhat porous such as by a woven configuration, the liquid escape from between nylon belt 55 and drum 54 into collection chamber 52 will be augment-ed. Typically, belt 55 would be o a net configuration with up to 3/16 inch spacings but any ~luidically porous arrangement can be used. The primary purpose of belt 55 is to support liquid flow therethrough while allowing positive feed of solids 66 into the roller press. Belt 55 also reduces friction between dr~l 54 and filter basket 75 (note Figure 5). ~:
Belt 55 is retained in position relative to drum 54 by an idler roller 56, a slotted tube 57, and an additional idler roller 58, the latter being vertically adjustable to maintain appropriate tension in belt 55. The endless ioop of belt 55 is completed via rollers 59 and 60. The solids which have been thus compressed are removed by rotating brush 61 so as to drop over the front surface 62 of collection chamber 52 and thence into storage bin 21.
Figure 4 shows the interrelationship of the drum and belt and represents a section along line 4-4 of Figure 2. More particularly, drum 54 has a rubber coating 65 for interfacing with nylon belt 55 with the compress-ed waste material being shown therebetween at 66. The edge o~ belt 55 is guided by slotted tube 57 which extends for approximately one-half of the circumference oE drum S~ as is shown in Figure 2 and is attached to sidewall 68 of the rotary press. The opposite sidewall 69 shown in Figure 2 has a slotted guide tube attached thereto similar to 57. The idler rollers such as 60 as can be seen in Figure ~ have slotted grooves (70) around the peri-phery at each end thereof which receives the edge bead 71 of belt 55 and ~3~i90 further provides guidance therefor.
The interrelationship of the slotted guide tube 57 and edge bead 71 is more clearly seen in Figure 5. In addition, Figure 5 illustrates the relationship of a wedge wire basket 75 which extends around the circumference of drum 54 in substantially the same manner as guide slot 57 shown in Figure 2. The particular cross-section of the arcuate bars forming basket 75 as shown in Figure 5 is advantageous in that it provides a generally rigid means for retaining endless belt 55 in proximity to drum 54 while still providing relatively free flow of liquid therethrough. In a typical example, screen filter 75 has approximately ~010 inch spacings with a screen thickness of about 1/2 inch.
For a typical cattle confinement feecling application, drum 54 has a diameter of 31.5 inches and is driven at 1 rpm of rotation, spreader 53 has a 6.5 inches diameter and 30 rpm of rotation, and scraper brush 61 is of a 4 inch diameter with 40 rpm of rotation. More particularly, drum 54 is composed of a 30 inch diameter steel cylinder with a 3/4 inch thick forty durometer rubber coating 65 molded on the outside with a 31.5 inch outside diameter finish. Wedge wire 19 is of the dimensions mentioned with a 6 foot width and 5 foot slope at 50 to the horizontal. The use of a stainless ~steel wedge wire screen 19 and the relatively low rotating speed ~one to two rpm) of dr~m 54, minimum energy is required and friction and wear are also minimized while obtaining maximum separation. The efficiency of the system can be improved and operating costs reduced by including a fan 40 pressuriz-ed plenum 41 from which air ducts 38 and ~2 are run to the vent pipes 38 and ~2 leading to the venturis in the bottom of the aeration tanks 11 and 25.
By way of example, assume the present invention is being adapted to accommodate confinement feeding of two thousand steers which average 40 , . .. , .. . :

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pounds of waste per day. This waste is 85% moisture containing 1.5 pounds Biological Oxygen Demand. If 60% of the 40 pounds were removed as liquid containing 6% solids~ there would be 24 pounds of liquid that would contain 1.58 pound of solids. In the 40 pounds of waste there was 6 pounds of dry matter and they contained 1 1/2 pounds Biological Oxygen Demand; then 1.58 pound of dry mat~er in liquid portion would contain .2531 pounds Biological Oxygen Demand per steer per day times twQ thousand steers equals 506.2 pounds ;~
Biological Oxygen Demand daily. A 5 horsepower pump would add 50 cubic foot of air per minute or 72,000 cubic foot of air per day and would equal 65 cubic eet per 1 pound of oxygen or 1108 pounds dissolved oxygen. With 50%
oxygen transfer, a 5 horsepower motor 40 in Figure 7 on a pump would furnish enough oxygen for two thousand cattle.
A 21 foot diameter by 21 foot deep tank 11, allowing 1 foot freeboard provides a capacity of 6927 cubic feet, OT 51,954 gallons. This amount of storage will allow 9.2 days retention time for the liquid por*ion of the waste from two thousand cattle, assuming no loss through aeration, and disregarding the volume of liquid that would be in the flushing system of the barn (1,000 feet long) continuously.
With a 5 horsepower motor 40 being used on a Parma pump 30 with a double venturi, 10 cubic feet of air per minute per horsepower can be put , - into the liquid at a~depth of approximately 18 feet below the surface. At this rate, 72,000 cubic feet of air would be induced every twenty-four hours.
If we assume 1 pound of oxygen in each 65 cubic feet of air, there would be 10,191 pounds of oxygen induced for each daily production of Biological Oxygen Demand with the calculated Biological Oxygen Demand being 506.2 pounds per day. Thus, aeration treatment will be completed in the 9.2 days retention time.

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In converting the Dissolved Oxygen requirements to pounds o Dissolved Oxygen per horsepower hour in thi5 particular application: 5 horsepower times twenty four hours times 9.2 days retent;on equalsllO4 horsepower hours. 506.2 pounds of Biological Oxygen Demand times 2 pounds of Dissolved Oxygen required equals 1012.4 pounds of Dissolved Oxygen. 1012.4 pounds of Dissolved 0xygen required per 1104 horsepower hours equals .317 pounds Dissolved Oxygen per horsepower hour which would be required to fur-nish 2 pounds Dissolved Oxygen per 1 pound Biological Oxygen Demand.
Since the industry has accepted the rate of Oxygen Transfer per horsepower hour to be 2 pounds per horsepower hour~ when working a mechanical aerator in a 2% solids liquid, containing a constant 1 P.P.M. - Dissolved Oxygen - a safe and general margin is projected. Instead of mechanical type aerators such as surface aerators of paddle wheel types prevalent in the prior art, the present invention via the venturi configuration assures that the air is broken up into minute portions and mixed well into the liquid well below the surface. The solids involved in this liquid are typically of 10/lOOQ of an inch or less. Surface area per pound of Biological Oxygen Demand in the solids involved are much greater than the average waste material.

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Claims (10)

THE EMBODIMENTS OF THE INVENTION IN WHICH AN EXCLUSIVE
PROPERTY OR PRIVILEGE IS CLAIMED ARE DEFINED AS FOLLOWS:

1. Apparatus for separating solids and liquids from a mixture thereof comprising:
screen means having an upper substantially flat surface oriented at an angle for permitting gravitational flow of said mixture over said sur-face, means for introducing said mixture to the upper portion of said screen means surface, said flat surface of said screen means being formed by a plurality of parallel bars arranged in a spaced relation for defining a plurality of transverse slots, the width of said slots being arranged to accommodate passage of the liquid from said mixture therethrough while block-ing passage of the solids from said mixture, liquid filter means, means receiving said mixture from the lower portion of said screen means for compressing said mixture against said liquid filter, and means for receiving the liquids passing through said screen means and said liquid filter means whereby the mixture after passing over said screen means as a result of the gravitational flow and after being compress-ed against said liquid filter means will have a reduced liquid content.

2. Apparatus in accordance with claim 1 wherein each of said parallel bars has a first surface forming part of the said flat plane and sidewalls extending thereform in converging relation so that the said transverse slot defined between adjacent said parallel bars increases in width below said flat surface.

3. Apparatus in accordance with claim 2 wherein said parallel bars are each oriented substantially horizontal.

4. Apparatus in accordance with claim 1 wherein said means receiving said mixture from said screen means includes cylindrical drum means having the axis thereof parallel to the plane of said flat surface, means for im-parting rotary motion to said drum, said liquid filter means including end-less belt means for following the circumferential motion of said drum means and for compressing said mixture received from said screen means against said drum means, said endless belt means being sufficiently porous to permit passage of liquid therethrough.

5. Apparatus in accordance with claim 4 wherein said liquid filter means further includes a fixed liquid filter having an arcuate configuration for retaining a substantially constant spacing between said endless belt and said drum.

6. Apparatus in accordance with claim 5 wherein said fixed filter and said endless belt are arrayed around the lower circumferential portion of said drum, said fixed filter including a plurality of arcuate spaced bars for permitting the liquid passing through said endless belt to pass through the spacing between said bars.

7. Apparatus in accordance with claim 6 wherein said means for receiv-ing liquids from said screen means is further arranged for receiving liquids from said fixed filter, said apparatus further including means for removing compressed material from said drum means after said material has passed between said drum means and said endless belt means.

8. Apparatus for separating solids and liquids from a mixture compris-ing:

a cylindrical drum means, means for imparting rotary motion to said drum means, filter means arrayed around the lower peripheral area of said drum means, said filter means including a plurality of spaced bars arranged for forming an arcuate surface in surrounding relation relative to the lower peripheral area of said drum means, porous endless belt means arranged to move against said spaced bars and said drum means for compressing said mixture against said drum means, means introducing said mixture between said drum means and said filter means at the point the peripheral edge of said drum means is rotation-ally moving downward for compressing said mixture between said drum means and said filter means, and means for collecting the liquid passing through said endless belt and the spaces between said spaced bars, whereby the liquid from said mixture will pass through said filter means while solids will pass between said drum and the endless belt means and will be discharged at the peripheral edge of said drum when said drum is moving upward.

9. Apparatus in accordance with claim 8 wherein said spaced bars are arcuate and arrayed for providing arcuate fluid passing slots therebetween, each said bar having convergent sidewalls so that said fluid passing slots are relatively narrow at the area closest to the peripheral surface of said drum means and diverge away from said drum surface to a relatively wider area.

10. Apparatus in accordance with claim 9 wherein said endless belt means has a bead along each edge thereof, said apparatus further including grooved guide means along the outer peripheral edges relative to said drum means for slidably retaining said belt across the lower peripheral surface of said drum means.