. ————————————— — - - _ w h ‘,.- , _ Vo~.~--—— ~-—--. -.-.-~ -é‘-Q.-..‘ o,-4.,-,- .-.-,A-----_,-.-r ---.----.._-.-.- .‘ ‘Vv.§“‘\.\‘q‘~-q . '_ “ " . b . o. O ”I..- . "On“.- 0-. cuflvfiqfid‘fi‘w‘mmffiwb‘wm - ‘ ' . . ' 5“ 'L_ DEWATERING A swme MANURE SLURRY: ‘; 4 f}: ‘ f EXPRESSION “ “ ’ f " . - Thesis for the Degree of .M. S. ‘ '1 9‘ MICHIGAN STATE UNIVERSITY 5 . JAMES FREEMAN STEFFE 4_ z o . v . . 1936 I I - c s n . - ~ - ' ‘ - . .. - . - ‘. . .. .- - - . . . . v . .. . . . . < . . - . - . _. - . . , . . . ,.. --' .-. -. - -~ . . - . . _ . . - ' - . . . _ ' - _ . ... > . .-- o - - -- ‘ ’ e - . . . I . . - .,.,.-_ ‘ , - o . , .... . _ . . .-._ - - - '- , . I , on! A ‘ ' . - _. .- - - - > - -, . _ ,_ , . . . _ . . - ,-._ ,.. . - ‘ . . .- o . .- . . . .. — , r . . . 1 . - . .t ' ‘ ' A , ._. P . - . . . - . . . _ . r. , - . _ 4 r..- .r . . .. _ .. ..., at. ' _ .. r r ,.. . ' . f’. o . ', V .. ‘n‘r .' . __ .. . E ..,. c . ’ . a . - . . .- . . . . ' ’ ' ._ ,.- o‘. . \ . a-. o -' . _ U. . , ...--. ' ‘ . ~- . E A - . ' " ' ‘ - . v . e.. -...o .. ' ' . . . r " ’ ' . n \c - ' c ' ‘ .. , , - -. . -.aott . ‘ - . . .-.o-. - . . . . a ' _ ‘ - . ' ' . ,... 0v '- - - - , . ... ! _ . v . . , - , .--v o ' o . ' r . .. ‘ no - ‘ ‘ 3 1293 00853 6405 11mmmmnmnwnmm Wu & ABSTRACT DEWATERING A SWINE MANURE SLURRY BY EXPRESSION BY James Freeman Steffe Expression is a special case of filtration in which a two phase liquid--solid mixture is placed under compres- sion by the movement of retaining walls. The liquid is allowed to escape through perforations in the retaining wall while the solids are held back. Basic information concerning the expression of a swine manure slurry is presented. Swine feces are found to consist of large fibrous solids and fine solids. The fine material may be separated from the fibrous solids by the addition of a dilutant (such as water) and subsequent mixing. Final removal is accomplished by allowing the fibrous solids to settle and conveying the excess liquid (with fines in suspension) away from the settled material. Liquid is easily expressed from the fibrous solids once the fine material has been removed. Expression is a viable method of dewatering swine manure if the fine solids are properly managed. James Freeman Steffe A pilot scale model expression device was con- structed to test a design concept for use in a full scale waste system. Model construction was based on the initial expression data and the experience gained in that phase of the work. The pilot scale device received an influent slurry from which the fine solids had been previously removed. Performance of the pilot expression model was promising and the design concept could be used for a full scale expression device. If such a device were added to an existing f1ush--lagoon system a 58-81 reduction in the quantity of volatile solids going to the lagoon could 6M aJor Professor epartment Cgairperson reasonably be expected. Approved Approved DEWATERING A SWINE MANURE SLURRY BY EXPRESSION By James Freeman Steffe A THESIS Submitted to Michigan State University in partial fulfillment of the requirements for the degree of MASTER OF SCIENCE Department of Agricultural Engineering 1976 ACKNOWLEDGMENTS I would like to thank my committee members--Dr. G. E. Merva, Dr. T. L. Loudon and Dr. M. Yokoyama—-for their guidance and advice during the project. Special thanks go to my major professor, Dr. J. B. Gerrish, who has been both mentor and devil's advocate. Susan Steffe cannot be thanked enough. Without her patience, understanding and assistance this study would never have been completed. ii TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES DEFINITIONS Chapter I. INTRODUCTION . II. THE THESIS PROBLEM . Formulation of Objectives Approach to the Problem III. LITERATURE REVIEW IV. SWINE MANURE EXPRESSION VARIABLES Experimental Equipment . Sample Preparation Experimental Procedure Testing Results . Discussion of Test Results Design Criteria for a Scale Model Expression Device V. THE PILOT SCALE EXPRESSION DEVICE . Purpose . Physical Description System Operation . . Results and Discussion . Considerations for a Full Scale Expression Device VI. HYPOTHBTICAL EXAMPLE Solids Removal Capability . . The Scaled Up Expression Device . iii Page vi .viii 01be \l TABLE OF CONTENTS LIST OF TABLES LIST OF FIGURES DEFINITIONS Chapter I. INTRODUCTION . II. THE THESIS PROBLEM . Formulation of Objectives Approach to the Problem III. LITERATURE REVIEW IV. SWINE MANURE EXPRESSION VARIABLES Experimental Equipment . Sample Preparation Experimental Procedure Testing Results Discussion of Test Results Design Criteria for a Scale Model Expression Device V. THE PILOT SCALE EXPRESSION DEVICE . Purpose . Physical Description System Operation . . Results and Discussion . Considerations for a Full Scale Expression Device VI. HYPOTHETICAL EXAMPLE Solids Removal Capability . The Scaled Up Expression Device iii Page vi .viii U154?- \l Chapter Page VII. SUMMARY AND CONCLUSIONS . . . . . . . . 69 APPENDIX . . . . . . . . . . . . . . . 72 BIBLIOGRAPHY . . . . . . . . . . . . . . 74 GENERAL REFERENCES . . . . . . . . . . . . 76 iv Table LIST OF TABLES Basic Information on Studies Dealing with the Liquid - Solid Separation of Swine Manure Slurries Volumetric Reduction and Moisture Content Data for Various Compression Tests Statistical Information and Values of the Constants used in the Deer Equation for Various Test Conditions Chemical Composition of Fresh Feces, Fibrous Solids and Fine Solids on an Air Dry Basis Page 20 25 73 Figure l. 2. 10. 11. 12. LIST OF FIGURES Expression Chamber Volume of Solid Material Plus Unexpressed Liquid at Different Pressures for Pressure Plates with Different Hole sizes . Volume of Solid Material Plus Unexpressed Liquid at Different Pressures for a Mixed and Unmixed Sample of 300g Feces and 1000ml Water Volume of Solid Material Plus Unexpressed Liquid at Different Pressures for a Mixed Sample of 300g Feces and Various Amounts of Dilution Water . Volume of Solid Material Plus Unexpressed Liquid and Force Plotted Against Time for Mixed and Unmixed Samples of 300g Feces and lOOOml Water Volume of Solid Material Plus Unexpressed Liquid and Force Plotted Against Time for Mixed and Unmixed Samples of 300g Feces and 1000m1 Water Pilot Model Expression Device Expression Chamber with an Initially Formed Cake Fresh Fecal Material, without Fine Removal, After Expression and Attempted Cake Formation . . . . . . Fresh Fecal Material after Fine Removal, Expression and Cake Formation . Accumulated Drainage from a Buchner Funnel Versus Time for a Feces Sample with Fines Removed and a Feces Sample without Fine Removal . . . . Accumulated Drainage from a Modified Buchner Funnel Versus Time for a Feces Sample Mixed with Various Dilutants vi Page 13 19 22 23 27 28 38 42 49 51 S4 55 Figure Page 13. Moisture Content of Feces Having Undergone Various Types of Treatment . . . . . . . 57 vii DEFINITIONS Expression: The separation of liquid from a two phase solid—liquid system by compression under condi- tions that permit the liquid to escape while the solid is retained between the compressing surfaces. Expression is distinguished from filtration in that pressure is applied by move- ment of retaining walls instead of by pumping the material into a fixed space (Perry and Chilton, 1973). Raw Manure: Feces plus urine with no bedding. The feces Units: would be the raw manure less urine. 1 Pascal (pa) = 1 Newton per square meter N/m2 1 Newton (N) = 1 Kg - m/s 1 pound force (lbf) = 4.44 Newtons 1 pound force/inch (psi) = 6.894 X 103 Pascals (pa) 1 pound mass (lbm) = .453 Kg viii I. INTRODUCTION People are becoming more and more aware of soil, air and water pollution problems. Increasing demands will be placed on swine producers to properly manage the waste generated from their businesses. The United States Depart- ment of Agriculture (1975) reports an average U.S. market hog inventory of 40.7 million for the June 1, 1974 to June 1, 1975 period. This is down 19 percent from the preceeding year, but is currently rising back to a higher level. On the average, a market hog will have a mass of 67 Kg. Assumingahog produces a quantity of manure equal to 6.5% of its weight per day, then 40.7 million market hogs produce 177 million Kg of manure per day. This figure does not include the waste produced from breeding stock. The physical characteristics of manure are strongly influenced by the diet of the particular animal in question. Miller (1975) estimates that 80% of U.S. hogs produced are fed a corn-soy diet, 10% are fed a milo - soy diet and 10% are raised on barley and other assorted grains. The waste used in the research presented here was taken from hogs on a corn - soy diet. Therefore, the results are applicable to a large percentage of the hogs produced in 1 the United States. Very few hogs raised for foreign markets are fed corn - soy diets. Slotted floor confinement housing with flush type manure handling systems are becoming increasingly popular in the swine industry because of the low labor input required for operation. In these systems manure is hy- draulically transported from the animal building to a temporary storage facility, where it is held for land application, or the waste is sent to an anaerobic lagoon for biological treatment. The partially treated waste- water is often recycled for flushing. Efficient liquid-solid separation of swine waste slurries offers a significant improvement to the flush- 1agoon system mentioned above. A few of the possibilities include: . 1. Improving the treatment kinetics of the anaerobic lagoon. Sixty to seventy percent of the total solids in swine manure are slowly biodegradable and their presence will reduce the effectiveness of any biological treatment process (Ngoddy et al., 1971). The absence of solids would reduce lagoon loading and thus reduce the size requirement of the treatment pond. 2. The removal of large solid particles would avoid plugging problems sometimes found in irrigation equipment during lagoon pump - out. In addition to the above, there may be valuable uses for the separated manure fractions. These would include refeeding the solid material to livestock and digesting the liquid effluent for methane gas production. Also, liquid - solid separation may aid in controlling odor problems associated with anaerobic lagoons. Reduced lagoon loading, due to solids removal, would decrease the total quantity of odorous gas produced from such facili- ties. II. THE THESIS PROBLEM Formulation of ObjectiveS‘ The motivating force behind the research presented here was the desire to develop a practical method of separating the liquid and solid parts of a swine manure slurry. Many farmers are adopting hydraulic waste trans- port because of the low labor input required to operate such systems. With the future in mind, the most desirable type of liquid - solid separation device to develop would be one which could be integrated into a flushing system. This basic thought was incorporated into the thesis objectives and it strongly influenced the experimental methods. A significant portion of the solid material in a swine manure slurry can be retained behind a perforated plate. The quantity of liquid which flows through the plate will depend on the amount of pressure applied to the slurry, the size of the perforations and the pretreatment given to the slurry. This process of liquid — solid separation is a special case of filtration called expres- sion. Preliminary studies showed that expression had excellent potential as a swine waste liquid - solid separation concept. Based on these findings the following objectives were formulated: 1. Identify the variables which significantly affect the expression of a swine manure slurry. 2. Evaluate the liquid - solid separation potential of expression when used in conjunction with a swine barn flushing system. 3. Design and evaluate an expression system for swine farm use. Approach to the Problem Initially, a literature search was conducted which produced no published information dealing with the expres- sion of liquid from a swine manure slurry. Other swine slurry liquid - solid separation schemes which have been investigated are presented in the literature review. With no guidelines to follow it was necessary to start the study by collecting basic expression data. A solid vertical cylinder, sealed at one end, was constructed and a porous piston was used to express water from a slurry contained by the cylinder walls. The slurry was made from fresh swine feces and tap water. A number of parameters such as quantity of water and degree of mixing were con- sidered during sample preparation. The amount of pressure required to express liquid from the slurry and the piston pore size were also considered as variables. Design criteria for a pilot model expression device were generated from the basic expression data col- lected during the first phase of the research. This design incorporated a number of unique and unproven ideas. These ideas included (1) the use of an influent slurry which had undergone prior physical treatment to remove fine material and (2) the formation of solid cakes utilizing previously dewatered solids for partial slurry containment. The pilot model expression device was constructed and tested to determine the usefulness of these concepts. From the identification of swine manure expression variables and the operation of a pilot expression device, sufficient information was made available to permit con- struction of a full scale expression system. Speculations on the testing and development of an on farm expression system are presented for the benefit of anyone who may accept the task. The study concludes with a hypothetical example of a swine manure handling system which includes flushing, an anerobic lagoon, and an expression type liquid - solid separation device. The potential reduction in total and volatile solids due to liquid - solid sepa— ration are discussed and dimensions for a large expression chamber (scaled-up version of the pilot scale model) are suggested. III. LITERATURE REVIEW When dealing with animal manure the following factors, which affect the physical characteristics of the waste, are important: 1. Livestock species. 2. Diet fed to a particular specie. 3 Animal environment. 4. Manure collection and handling practices. Most existing literature fails to consider all the above parameters (see Table 1). Without this information it is difficult to compare the results obtained from different researchers. The salient aspects of the studies presented in Table l are discussed in the remaining part of this literature review. Verley and Miner (1975) used a rotating flighted cylinder to concentrate the solids in a swine waste slurry. This device is described as "an inclined tube fitted with a helically wound fin attached to the inner surface". As the tube is rotated the solids are concentrated between the fins and finally discharged from the upper end of the device. The cylinder is capable of removing all settlable particles which would be retained by a screen with 1.19 mm Openings. A solids stream of 4.3% was obtained from a feed :oouom kamQOMHmum Hmuawm Essom> om:mahucou nonsmooa m>flomfippcoo :oouom mcwumunw> coohom mcwumunw> O mmsmwgu:ou :ooyom mafiumnnw> ocoHoxo wfiscwq :omuum zumcofiumum _Hmc:waxo wougmfiamvemompom whoopsm Eoym uosmsam emamfiumam poz mama Emflaonmuoe aw woumaomw mmoa Hmaew>fieaH eunuxwz nupua aofiomemxo mumpunw Eoum woamsam whooam wouuoam Howe: Ham eoHWSUOQm ooz emHmMumam “oz mm>wuueem an + Ham: amonsom *m.HH on o.mH + :noo coaaonm ucsouu wm.mm ow o.mn eoumauoam uoz emflmuuoam uoz eoamuumgm “oz mmumav mugs: w movflcmmwme flfiamflv mecca masflx .Espofio mflnmav .Hm um xuwowz fifiamfiv ummmomm w xma .moEo: ammofiv .2“ so spasm flmamfiv “on“: w xmauo> woumoa mmow>om :oflumnmmom eflfiom-ufiscug mu. mm; who OUH30m Home mo: whonus< .moAHHSHm ouscms mafizm mo :ofiumnmmom vfiaom - wwscfia on» new: mcwamow mowwsum no cowumahomcfl uwmmm .H m4m.moomm HmfiuHcH moaoz mumam mHmEmm cu umou CH mooww ucmaammm mxmu mssao> mxmo HmCHm mo HmumEmwn mo owuwon vmcpm kumB mo zufiucmso .mummu coflmmwumEoo msofinm> pom mumv ucoucoo musumwoe paw :ofiuonpou ownu¢Egflo>nu.N mam ZOO-L. ”i —E 100 ‘— 1 . 1L 1 1r 4' Is 30 215 60 75 PRESSURE (PA x 10'3) Figure 3. Volume of solid material plus unexpressed liquid at differ- ent pressures for a mixed and unmixed sample of 300g feces and 10001111 water. The pressure plate holes for each test were 4.76mm in diameter. 23 800T ® 70dt 1_{}_. i (D 600 ml water test B 600.”, 300 ml water A 50m. 3 4 n 600 ml water test A Eg a c) 1000 ml water test A m400" D g 0 1000 ml water test B S A 2100 ml water 300., <~—€¥ 200.. £L ___ 100+ e + + e .L 15 30 45 60 75 PRESSURE (PA x 10‘3) Figure 4. Volume of solid material plus unexpressed liquid at different pressures for a mixed sample of 300g feces and various ammounts of dilu- tion water. The pressure plate holes fbr each test were 2.38mm diameter. 24 which is not represented by total solids analyses. The cake resulting from the non-mixed sample was sticky in texture and appeared less dry and fibrous than the other cakes. When the cakes from the mixed and unmixed samples were allowed to air dry for 24 hours (under room condi- tions) they both formed a crust on their exterior surface. When the crusts were cut open the cake from the unmixed sample appeared lighter in color (light brown) and had the least pleasant odor of the two cakes. Most of the lines presented in Figures 2, 3 and 4 can be approximated using the Deerr equation (2). No attempt was made to model the two B tests (Figure 4) with this equation. All the constant force data sets presented, with the exception of two (Table 3) have high correlation coefficients. The least acceptable cakes were formed in the cases where the ratio (percent) of the final cake volume to the initial feces volume is greater than 100 (Table 2). For these situations the values of 1/n (Table 3) from the Deerr equation (2) are very large (48.3 and 49.9) indicating that a large increase in pressure will only yield a small reduction in volume. The variable force tests were performed on the Instron Testing machine. In all four tests the downward piston movement was stopped and held fixed when a force peak of 400 N (90 lbf) was reached. This force peak corresponds to an internal pressure of approximately 25 ucw565wwmoo COHumHmuuoo A U 1 I. l' Elli-‘5 0 00. 0.0 0005. 5.500 00.0 05050500 0005 000 0 50. 0.00 0550. 0.550 05.0 0002 0005 000 0 00. 0.05 0000. 0.550 05.0 00055500 0005 000 0 50. 0.55 0550. 0.000 00.5 00050500 0055 000 0 00. 0.5 0505. 5.0055 00.5 00050500 , 0005 000 0 50. 0.0 5005. 0.5500 00.5 00050500 000 000 0 50. 0.00 0050. 0.500 00.5 00050500 000 000 05:5om muma AEEV 555v mmomm va 6555mm mo 5 c c o mmao: mumam wC5x52 mHQEmm ou umwu CH mwomm Monasm * M mo umuoEmHQ mo common pmcwm umumz mo zuHucmso . wGOHUMUCOU umwu m5055m> Mow co5umsvm Home mcu Cw pom: mucmumcoo msu mo mosam> can COHumEHowSH Hmofiumfiumumun.m mqm magmw5m> may mo macaw may .cfie\Eowom. we pcmeo>oe acumwm vhmzczou m mucmmwummh c0053 :HE\0005.mN ww .Hopmz HEOOOH mam wwowm woom mo wmeEmm wmxwecs cam wmxfle 50m mafia uwc5000 coupoam oohom paw vwsvwa cmmwwnmchs mafia Hmflsmwma nwaom mo mesao> .m muswfim 5555555255. N5 05 w 0 v m 5 p p L P b 0051 1005 wmxwe I 06505 m 5035505553....00505 M m 1005 00. mm qa ) l / @0005le55 I 605:5..0»... ,.. W O I, /I\ “W _I I oomlToc.ooouonaoo-noogoo noo'Oooo.o.c/ ooh-o vmxHEImESHOn/UJ ‘ I, I . . -000 / / ... I .. I o. I .. 000 II ’ I I [I 000. 28 mafia oEDHo> oapmwmm> may mo wmoam one (00) EIND'IOA .CHE\EoO5N.5 mo pcmem>oe cogmfim vsmzazow m wvcmmmummu £6553 cHE\oo5o.5m 00 .Hmpmz HEQOOH was mmoom woom mo memEmw wmxflec: wcm vwxfle How 6555 wmcwmwm vmwpoam wosom cam vflsvwa wmmmwsmxmc: mafia Hmwsmpme nfiaom we mesao> .0 msswfim €505 525.5. N5 05 w o v _ ,5 5 rII L wmxfiacs I 00505 005 1005 wwxwe I 00505 0051 m. IIIIIIIIIIII IIIIIIIII 005% m ./ oomn / Ioom GQXMHE: II ®E3H0> O O O O ’o/o. 1 A5. I /.. 0050 @9525 I 90555655 '1 /.. I. 1000 29 particles will flocculate and settle to form a fluffy mass. This fine matter seems to give fresh swine feces its paste-like character. The fibrous material, when removed from the fines, appears as a granular, coarse, crumbly and nonpaste-like product. The interaction of the fibrous solids, fines and dilution water will greatly affect the success of a swine waste expression process (Table 2). Mixing acts to sepa- rate the fines from the fibrous material. If sufficient dilution water is added (with mixing) a large quantity of fine material will be removed from the fibrous solids. The fines in this fluid will easily go through the piston plate as it falls under its own weight. This can be very beneficial in dewatering the solids because the fine material causes plugging problems in the cake by increasing the cake resistance to water movement. Shortly after the expression process starts, a layer of solid material builds up at the lower surface of the piston face. This layer acts as a filtration medium and becomes thicker as the piston moves downward. The fluid flowing through the piston must also flow through this mass of differentially sized particles. The fines act to fill void spaces and plug water movement channels. Plugging problems, such as these, are apparent when reviewing the constant pressure data. If the amount of dilution water added (e.g., Figure 4-- 300 ml water) 30 was equal to the quantity of feces present the slurry would not dewater. The most likely reason for this is that there was inadequate removal of the fines from the fibrous solids. A number of comments can be made concerning the 600 m1 dilution curves presented in Figure 4. In the 600 ml test B plugging occurred immediately after the start of the attempted expression. The data from the 600 ml test A (curve not drawn) shows an entirely dif- ferent pattern. The data point found between 15,000 pa (2.2 psi) and 30,000 (4.4 psi) obviously deviates from the trend found in the other curves. This deviation was caused by plugging problems. When additional dead weight was added to obtain the next data point (from the one mentioned above) the piston dropped very rapidly and a surge of fluid came through the porous plate. No surges were observed while collecting data for the other curves. An important point can be made in reviewing the curves in Figure 4. The two 600 ml tests show that there is unpredictability associated with this dilution ratio (2 parts water/l part feces). However, there is good agreement between the results of the two 1000 ml tests. This dilution ratio (10 parts water to 3 parts feces) can be considered as a lower limit for acceptable expres- sion. Let me emphasize that this is not an absolute limit. The 2:1 ratio is certainly too low and the 10:3 ratio 31 worked in two cases. On particular occasions lower ratios may result in acceptable cakes. Fortunately, the feces used in an expression device incorporated into a flushing operation would be diluted in excess of 10 parts water to one part feces (10:1). In a practical application the dilution ratios involved are far above the range where plugging may occur. In looking at Figure 3, a number of points can be made concerning the use of mixed and unmixed samples. The unmixed sample yielded the least acceptable cake because of its sticky character and poor keeping quality (as previously mentioned). The final volume of the un- mixed sample is greater than the mixed sample which, in this case, is indicative of the fact that more water was retained after expressing the unmixed sample. Also, the slope of the curve for the unmixed sample approaches zero at a low pressure because plugging occurred early in the test. It was evident early in this study that a pressure plate with 2.38 mm diameter holes was well suited for the expression of a swine slurry. Data collected using this plate are represented in Figure 4. Acceptable cakes were formed in cases where the final volume was less than 300 cc. For these tests I got very little volumetric reduction when applying pressures in excess of 45,000 pa (6.5 psi). This is indicative of the low pressures which would be required for a pilot scale expression operation. 32 Information concerning the rate of expression can be taken from the Instron data. In all tests represented in Figures 5 and 6 the downward piston movement was stopped when a force peak of 400 N (approximately 90 lbf) was reached. With a piston movement of .508 cm/minute (Figure 5) less volumetric reduction was achieved with the unmixed sample. The cake obtained from the unmixed sample could be handled as a solid but it was sticky and paste-like, being very similar to the cake obtained from the unmixed sample in the constant pressure test. The most important point to be made here is that a downward piston movement of .508 cm/minute proved to be a workable rate which suffi- ciently dewatered the manure slurry.‘ The extreme variation in force in the mixed sample in Figure 6 can be accounted for by alternate plugging and unplugging across the face of the pressure plate. During the piston movement, I could see periodic surges (geyser like) coming through various holes in the plate. Unpredictable plugging, such as this, would be undesirable in a large scale expression operation because of the small dewatering gain associated with a high energy input. The rapid increases in force required to obtain small decreases in volume could be considered as a dashpot effect. Slower piston movement would allow the water to "ooze" from the slurry. Similar instability did not occur in the other constant pressure tests. 33 The variation in shape of the force - time curves for the unmixed samples in Figures 5 and 6 can be also explained with reference to plugging. With the faster piston movement (Figure 6) the force peak is reached at a higher final volume (over 300 cc) and when piston move- ment is stopped the force drops off much more quickly. The rapid piston movement caused plugging to occur after a shorter distance of piston movement. The rapid relax- ation of the force - time curve of the unmixed sample may have been due to the lack of volumetric reduction obtained. The cake still contained a lot of water which may have aided in unplugging. Design Criteria for a SCale Model Expression Device The expression process as a method of liquid - solid separation of a swine manure slurry is physically feasible. In designing such a system for incorporation into a swine manure flushing operation the relationship between slurry mixing and relative proportions of dilution water and feces must be carefully considered. If the amount of feces is approximately equal to the amount of water in a well mixed slurry, attempts to express liquid from the mixture will fail. Liquid may be expressed from a similar quantity of material which had not been mixed. However, solids separated in this manner are less desirable than those from which the fines have been removed. 34 Practically speaking, it is unlikely that a system to express liquid from swine waste would operate with an unmixed influent. The hydraulic transport of waste is itself a mixing operation. It is difficult to estimate the degree of mixing which takes place during flushing. Certainly, the solids near the end of the flush channel ’would be inadequately mixed. To insure proper management of the flocculated solids supplemental mixing equipment should be included in the pilot system. In summary, the following factors should be con- sidered in an expression system design: 1. The fine material should be separated from the fibrous solids. To ensure good separation the ratio of dilution water to feces should be at least 10/3 and mixing should be suffi- cient to disperse the feces lumps into their aggregate particles. 2. In an expression device 2.38 mm diameter holes will retain most of the fibrous solids. 3. An upper limit of 45,000 pa (6.5 psi) in the expression chamber will yield an acceptable cake. Chamber pressure, hole size and rate of expression are interrelated variables. At high rates of expression (for a particular hole size) high chamber pressures will develOp and more power will be required for dewatering. This 35 problem occurs because of the large quantity of incom- pressable fluid (tap water) contained in the mixture under compression. This phenomenon could be considered a dash- pot effect. The upper pressure limit stated above (45,000 pa) was determined from dead weight tests. In these cases chamber pressure was maintained at a constant level and the rate of expression (characterized by downward piston speed) was allowed to vary. Pressures exceeding 45,000 pa could easily be created (as seen from the Instron data) in an expression chamber before sufficient dewatering had taken place if high rates of expression were maintained. V. THE PILOT SCALE EXPRESSION DEVICE Purpose The purpose of building the pilot model expres- sion device was to bridge the gap between the basic information collected using a vertical expression chamber and the farm expression system. I propose a total waste handling system incorporating flushing and liquid - solid separation via expression. Briefly, this system involves the following ideas: 1. Hogs would be housed over slats and manure flushed to a central location (flush pool). 2. The separation of fines from the solid material would be accomplished by mixing in the flush pool. 3. After mixing, the fibrous solids would settle and the liquid (with fines in suspension) above the large solids would be pumped to an anaerobic lagoon. 4. The fibrous solids would be pumped to the expression system. 5. The liquid separated during expression would drain to the anaerobic lagoon. The dewatered solids could be used directly or stored in an appropriate location. 36 37 The scale model expression device was designed as a part of the above mentioned waste handling system. The design incorporated a number of unproven methods which needed testing before they could be used in a full scale system. These methods included the use of concentrated fibrous solids (with fines removed) as the influent to the expression chamber, and a start-up procedure involving an initial cake formation and subsequent solids dewatering using the cake (previously dewatered solids) as a contain- ment wall for the influent slurry. These methods will be further discussed in the remaining portions of this chapter. Physical Description Figure 7 is a photograph of the expression device. The discussion in this section will refer to that figure. The expression chamber (A) was constructed from a 7.62 cm inside diameter plexiglass cylinder with a .64 cm thick wall. The overall length of the cylinder was 61 cm and 2.38 mm diameter holes were drilled in the center section of the chamber located above the drip pan (C). There were 8 rows of holes uniformly spaced around the cylinder with 15 holes per row. The holes in any particular row were spaced 1.3 cm apart. The center of the hopper (B) was located approximately 45 cm from the left end of the chamber. The hopper inlet to the chamber was a square with sides 6 cm in length. The piston rod (D) was made from a 1.9 cm diame- ter wooden dowel. The piston head was 7.6 cm in diameter 38 Figure 7. Pilot Scale Expression Device II 0:00,. \\ ecowhmwc: wsw>mz wmomm we #005000 waspmwoz .05 mhswwm wmomm 20mm mewmmmxm QHQOHA #05500 0025000 2000005 0250000 02 5I, 0252000 0005 5, 0250000 02 .5 20550550 555 _ 20550550 550 _ “HHHHM\\\\\T HHHHV\\\\\ HHHH“\\\\\ o 1d 3 O 3 Qu \ \ \ II 05 w I S u m 3 3 O p N \\\\\\\\ I00 m N L k\\\\ mm M a 1... \\\\\\ a. 0 1105 w T_. kw 00>0200 002 00250 00>0200 00250 I..005 58 differences do not appear to be large, but they are very meaningful. The screen drained sample and the sample with fines removed would aptly be called a semi-solid. They would act fluid-like in solids handling equipment. Considerations for a Full Scale Expression Device This study has demonstrated the possibility of expression as a swine manure liquid - solid separation process. The true test of utility, however, will be to build a full scale system and operate it in a farm situ- ation. It must be subjected to continual usage under a variety of conditions. The system must be developed to meet the needs found in practical operation. This type of study would be the logical continuation of my research. In constructing a full scale expression device for developmental studies there are a number of factors which should be considered. Here are some of them: 1. The holes are the most vulnerable feature of the expression chamber. Plugging due to slime and particle build up may be a problem. A solution to the particle accumulation problem may be to drill the expression chamber holes at an angle oblique to the direction of solids travel. 2. It will be difficult to determine the optimum physical size of the expression chamber. The 59 length of the chamber should provide enough resistance to solids movement for good de— watering. However, if pressure is too high in the chamber, solid material may be extruded through the holes. Besides chamber length, other factors such as surface roughness and chamber orientation will effect resistance to solids movement. The number and distribu- tion of holes will also be an important parameter to consider. It was demonstrated in the pilot model that liquid - solid separation via expression was best achieved when the system influent was fresh feces with fines removed. There will be some handling problems involved in getting this material from the mixing location to the expression chamber. When this type of influent was placed in the hopper of the pilot expression device (with the piston in the forward position) the water in the slurry drained out around the sleeve edges. This created a bridging problem and it was necessary to dislodge the solids from the hopper. For a full scale system, the expression piston (as opposed to the secondary piston) should be constructed without perforations. These 6O perforations were plugged after the piston had cycled two or three times and acted to loosen particles from the solid cake. A particularly important parameter for the developer to determine will be the optimum rate of expression. A rate of piston movement of 2.1 cm/min was acceptable in the pilot model. From experience with this device it appears that faster piston movement would have been acceptable. There may be scale-up problems encountered in going from pilot scale to full scale device. This can be determined from development and testing. VI. HYPOTHETICAL EXAMPLE There are two purposes for presenting this hypo- thetical example. One is to get an idea of what size expression device could handle a large hog production operation. The other is to demonstrate the potential usefulness (solids removal capability) of liquid-solid separation by expression. Solids Removal Capability Consider a finishing hog barn with 3 average of 300 hogs (average mass equals approximately 67 kg) at any particular time during the year. These hogs would be housed over slats and the manure would be flushed to a mixing basin. Solid material would be pumped from the mixing basin to an expression device for dewatering. Liquid separated during expression and excess liquid from the mixing basin would go to an anaerobic lagoon for treatment. Lagoon water would be recycled for flushing. Assume (Data from Midwest Plan Service, 1975a): 1. Raw manure production = 6.5% of live body weight 2. Feces = 55% of the raw manure produced 3. Raw manure = 9.2% total solids 4. Volatile solids = 80% of the total solids 61 62 S. The quantity of total solids contributed from the urine is small and can be neglected. Total quantity of feces produced per day = .065 X .55 X 300 hogs X 67 kg/hog = 718.5 kg feces Total quantity of total solids (T.S.) produced per day = .065 X .092 X 300 hogs X 67 kg/hog = 120.1 kg T.S. Total quantity of volatile solids (V.S.) produced per day = 120.1 kg T.S. X .80 V.S./T.S. = 96.0 kg V.S. An estimate of the total solids retained by expres- sion can be obtained by looking at the data presented in Table 2. Consider the case where there was complete mixing and liquid was expressed through the 4.76 mm holes. In this test, values of 74.7 and 95.6 percent are given for the moisture content of the cake and effluent respec— tively. Selecting these values for estimating the percent retention of T.S. and V.S. should yield conservative figures because 2.38 mm holes are recommended for a full scale expression device. Less solid material is retained when using the 4.76 mm holes. Using the data for the above-mentioned case, the following estimates can be made: 300 g X .675 X (1 - .747) = 51.2 g T.S. in cake The value 67.5% used above is a volume ratio. However, it is assumed that the density of the cake is approximately equal to that of water. The same assumption is made in computing the quantity of total solids in the effluent. 63 1300 ml slurry - (300 X .675) ml cake = 1097.5 m1 effluent 1097.5 ml effluent X (l .956) = 48.2 grams T.S. in effluent 51.2 % T.S. retained in cake = X 100 = 51.5% via expreSSIon 51.2 + 43,2 ' V.S. (51.2 + 48.2) g T.S. X .8 ———— = 79.5 g of V.S. in T.S. feces The quantity of volatile solids contained in washed swine fecal material is found in Ngoody et al. (1971). These researchers found that dried solids taken from a vibrating screen separator were 91.5% volatile. The influent material was a feces - urine slurry which had been diluted with 10 parts tap water and well mixed before separation. This product would be similar to that obtained from an expression process. Taking this into consideration,' the percent V.S. retained in the solid cake can be calcu- lated. V.S. 51.2 glflS.2h1cake X.915 ———— = 46.8 g V.S. retained T.S. in cake 46.8 % V.S. retained in = ———— X 100 = 58.8% cake via expression 79.5 64 Going back to the 300 hog finishing barn, the quantities of total solid and volatile solid material entering the lagoon can be calculated. Quantity of T.S. entering the anaerobic lagoon per day 120.1 Kg T.S. X .515 = 61.8 Kg T.S. Quantity of V.S. entering the anaerobic lagoon per day 96.0 Kg V.S. X .588 = 56.4 Kg V.S. It would be reasonable to expect a 58.8% reduction in the quantity of volatile solids going to an anaerobic lagoon when the solids are separated from the manure slurry be expression. Consequently, 41.2% of the normally required lagoon (no solids separation) would be adequate. The fibrous solids left after expression could be stored or immediately spread on farm land. Solids taken from the expression device formed a surface crust when allowed to air dry overnight. Ngoddy et al. (1971) found that fibrous solids taken from a vibrating screen were odor free, relatively stable, and did not attract flies. The Scaled Up Expression Device In this section the pilot expression model dis- cussed in Chapter V (Figure 7) will be scaled up to handle the waste generated from a hog farming operation. A number of assumptions will be made and an example for the general case will be worked through. Power requirements for a particular expression device will be estimated. 65 Physical Size Assume: 1. There are no scale up problems involved in going from the pilot to the full size expres- sion device. Raw manure production equals 6.5% of the live body weight. The expression chamber is circular and the length of the piston stroke is equal to 1.5 times the cylinder diameter. The length of the hopper opening to the chamber, in the direction of piston movement, is 1/2 the chamber diameter. The total amount of material to be processed by expression will be equal to the feces produced plus 1/3 of that volume. The addi— tional volume would enter the system while transporting the feces to the expression device. The effective expression stroke (slurry contained on all sides) is one chamber diame- ter in length. Variables: D density of feed material (Kg/cms), approximately equal to water chamber diameter (cm) 66 s = forward piston Speed (cm/min) r = fraction of raw manure which is feces h = number of 67 kg hogs in the system t = processing time allowed for a 24 hr waste load (hr) s'= backward piston speed (cm/min) Time required for piston to cycle = l l s+s' —— X 1.5d + — X 1.5d = 1.5d ( min 5' 5 55' Amount of material processed per piston cycle = volume swept by the effective piston stroke = d A II (—) 2d = — d3 cm} 2 4 Volume of material the expression device must process = volume of feces produced + 1/3 that volume = rh 4 rh —— (67) (.065) — = —— (5.80) cm D 3 D 3 Volume of waste to be processed = Expression system capacity Allowed processing time (i) I?) (3.?) — At.) = Ndz ss' 4 x 1.5(s+s') 67 Solving for d (required chamber diameter) yields: rh % s+s' % d = 13.6 (-—{) ) cm t 55' 3 where D = 10-3 Kg/cm With 300 hogs, a 10 hr processing time, r equal to .55, aforward speed of 2.1 cm/min, and a backward speed of 30 cm/min a chamber diameter of 39.4 cm is required. From experience gained in this research a chamber length, measured from the forward edge of the hopper, of 3d is recommended. If the hopper opening is l/Zd in the direction of piston movement, and a length of chamber l/Zd is provided at the back of the hopper, then the overall chamber length would be 4d or 158 cm (5.2 ft). Power Requirements From the basic expression data I found that ac- ceptable cakes could be formed using 45000 pa (6.5 psi) as an upper pressure limit in the expression chamber. Taking the above mentioned chamber (32.5 cm diameter), an estimate of the power required to drive the expression device can be calculated. Assume: 1. A pressure of 45000 pa is maintained in the chamber during expression. 68 2. Power required for the action of the expression device other than actual expression (backward piston movement, etc.) equals the power required for expression. Work done during expression = .323 2 (45000) (n) (————) (.323) = 1190.9 N m 2 Time required for expression = 32.2 —— 2.1 = 15.33 min = 919.9 sec. Power required for expression = 1190.9 N m -3 ______ ——— = 1.29 watts (1.72 X 10 hp) 919.9 sec Total power required = (1.29)2 = 2.58 watts (3.45 x 10’3hp) Power requirements are small. If the chamber resistance to cake movement was very high and the power estimate were off by a factor of 100, then 258 watts (.34 hp) would be required to drive the expression device. VII. SUMMARY AND CONCLUSIONS Basic variables affecting the expression of a swine manure slurry were identified using a vertical expression chamber. The chamber consisted of a plexiglass cylinder sealed at one end with a porous piston used as the third retaining wall. Degree of mixing and quantity of dilution water added to the fresh feces were significant influent treatment variables. Variables considered when operating the expression chamber were the piston plate hole size and the force used to move the piston into the slurry. Constant and variable forces were applied and the rate of expression was considered. The basic expression studies demonstrated that swine feces consist of large fibrous solids and fine solids. The fine solids give fresh feces their paste- like character and cause plugging problems when expressing liquid from swine manure slurry. The fibrous solids, when separated from the fine material, form a relatively stable, odor free product which dries rapidly when exposed to air. Expression is a viable method of separating the liquid and solid parts of a swine manure slurry if the fine material contained in the feces is properly managed. 69 70 The fine solids should be removed from the fibrous solids before expression is attempted. Fines removal can be accomplished by mixing fresh feces with water and removing excess liquid after settling of the fibrous solids. The fine matter is contained as a suspended solid material, in the liquid above the settled solids. In less than 30 minutes after the fibrous solids settle, the fine solids will flocculate and fall forming a fluffyrmuuson the t0p of the larger particles. When a swine manure handling system includes flushing, sufficient water is always available for fines removal. A pilot model expression device was constructed to test a particular design concept. The design incorpo- rated two unique operating methods. These were (1) the use of concentrated fibrous solids (fines removed) as the influent to the expression chamber, and (2) an operating procedure involving the use of previously dewatered solids for slurry containment. These methods proved successful and suggestions were made for the design and development of a full scale expression system. A hypothetical example is presented to demonstrate the potential usefulness of liquid — solid separation by expression and to project the size of an expression device (scaled up pilot model) which might be required to handle a particular hog operation. The solids removal capability of expression is promising. If expression was 71 used to separate solids from a swine slurry (after flush- ing) before the waste was sent to an anaerobic lagoon for treatment a 58.8% volatile Solids removal could reasonably be expected. In other words, if an expression system was incorporated as an add on to a flush - lagoon system, only 41.2% of the existing lagoon would be required to effec- tively treat the waste. The size of an expression system required to effectively treat the waste from a normally sized hog operation is quite reasonable. Based on data found in this study, a 39.4 cm diameter expression cylinder 158 cm in length could effectively treat the daily waste from 300 market hogs in 10 hours. Testing and development of a full scale expression device may show that this perform~ ance can be improved due to higher rates of expression. APPENDIX 72 TABLE 4. 0-Chemical com solids and fine $011 osition of fresh feces, s on an a1r dry basis. preformed by Animal Husbandry Dept., Michigan State University) fibrous (Analysis Fresh Feces Fine Solids Fibrous Solids DM% 97.99 96.16 98.91 CP% 19.59 24.93 17.99 Fe ppm 1433. 1928 1405 Zn ppm 565.8 947.5 494.9 Cu ppm 82.55 126.5 63.26 Ca% 2.21 4.59 2.40 Mg% .84 1.28 .70 Na ppm 6370 5338 3236 K ppm 4213 5614 2755 73 BIBLIOGRAPHY Baskerville, W. H., J. A. Glass, and A. H. Morgan, 1947. Report of Progress of a Study of Factors Affecting the Pressure Extraction of Cottonseed Oil. Oil Mill Gazette: May, 56-63. Carter, C. L., 1952. A Preliminary Study of Some Factors Affecting the Hydraulic Pressing of Cottonseed. Oil Mill Gazette: March, 40-44. Deerr, Noel, 1912. The Milling of Cane Considered in Relation to the Volume Occupied by the Fiber, Hawaiian Sugar Planters' Association Experiment Station. Agricultural and Chemical Series. Bulletin No. 38. 61 pp. Glerum, J. C., G. Klomp, and H. R. Podma, 1971. The Separation of Solid and Liquid Parts of a Pig Slurry. Chapter XVIII, pp. 345-347, in Livestock Waste Management and Pollution Abatement. ASAE, St. Joseph, Mi. 49085. 360 p. Gurnham, C. F. and H. J. Masson, 1946. Expression of Liquids From Fibrous Materials. Industrial and Engineering Chemistry 38: 1309-1315. Hickox, G. H., 1953. Some Factors Effecting Hydraulic Extraction of Cottonseed Oil. Journal of the American Oil Chemists' Society 30: p481 - 486, Nov. 1953. Homes, L. W. J., D. L. Day, and J. T. Pfeffer, 1971. Concentration of Proteinaceous Solids from Oxida- tion Ditch Mixed 0 Liquor Chapter XVII, pp. 351- 354, in Livestock Waste Management and Pollution Abatement, ASAE, St. Joseph, Mi. 49085. 360 p. Koo, Eugene C., 1942. Expression of Vegetable Oils. Industrial and Engineering Chemistry 34, 3: 342- 345. Miller, E. R., 1976. Professor of Animal Husbandry, Michigan State University, East Lansing, Michigan. Personal Communication, May 10. 74 75 Ngoddy, Patrick 0., J. P. Harper, R. K. Collins, G. D. Wells, and F. A. Heidarg, 1971. Closed System Waste Management For Livestock. U.S. Government Printing Office, Washington, D.C. 110 p. Perry, R. H. and C. H. Chilton, 1973. Chemical Engineer's Handbook. McGraw-Hill, Inc., New York. Sec. 19, 5th Ed. Shutt, J. W., R. K. White, B. P. Taiganides, and C. R. Mote, 1975. Evaluation of Solids Separation Devices. Chapter 21, pp. 463-467, in Managing Livestock Wastes. ASAE, St. Joseph, Mi. 49085. 631 p. Taiganides, E. P. and W. K. White, 1972. Automated Treatment and Handling of Swine Wastes. pp. 331- 339, in Waste Management Research (Proceedings of the 1972 Cornell Agricultural Waste Management Conference). Graphics Management Corporation, Washington, D.C. 580 p. United States Department of Agriculture, 1975. Hogs and Pigs, NtAn 4 (6 - 75). Statistical Reporting Service, United States Department of Agriculture. Statistical Reporting Service, Washington, D.C., 20250. Verley, W. E. and J. R. Miner, 1975. Application of Rotating Flighted Cylinder to Livestock Waste Management. Chapter 21, pp. 452-455, in Managing Livestock Wastes. ASAE, St. Joseph, Mi. 49085. 631 p. GENERAL REFERENCES Backhurst, J. R. and J. H. Harker, 1974. Evaluation of the Physical Properties of Pig Manure. Journal of Agricultural Engineering Research, 19: 199-207. Bartlett, H. D., R. E. B05, and E. C. Wunz, 1974. De- watering Bovine Animal Manure. Transactions of the American Society of Agricultural Engineers, 17: 968-972. Fairbank, W. C. and E. L. Bramhill, 1968. Dairy Manure Liquid - Solid Separation. Agricultural Extension Service, University of California, AXT 271, June. 3 pages. Loehr, Raymond C., 1974. Agricultural Waste Management. Academic Press, New York. 576 p. Mattil, K. F., F. A. Norris, A. J. Stirton, and D. Swern, 1957. Baileyfs Industrial Oil and Fat Products. Interscience Publishers, New York, New York. 1103 p. Midwest Plan Service, 1975a. Livestock Waste Facilities Handbook. Midwest Plan Service MWPS - 18. Iowa State University, Ames, Iowa. Midwest Plan Service, 1975b. Livestock Waste Management With Pollution Control. Midwest Plan Service MWPS - 19. Iowa State University, Ames, Iowa. Miller, E. C. and C. M. Hanson, 1975. Flushing, Extension Bulletin E - 777. Cooperative Extension Service, Michigan State University, East Lansing, Michigan. Taiganides, E- P., 1963. Characteristics and Treatment - of Wastes from a Confinement Hog Production Unit. Unpublished Ph.D. Thesis, Department of Agricultural Engineering, Iowa State University, Ames, Iowa. Taiganides, E. Paul and R. K. White, 1971. Automated Handling, Treatment and Recycling of Waste Water From an Animal Confinement Production Unit. Chapter VIII, pp. 146-148, in Livestock Waste 76 77 Management and Pollution Abatement. American Society of Agricultural Engineers, St. Joseph, Mi. 49085, 360 p. HICHIGRN STQTE UNIV. LIBRQRIES II! III III llllHlllllll Ill 31293008536405