Solid/Liquid Separation of Hog Manure Utilizing a Settling Tank Presented To Manitoba Rural Adaptation Council Inc. By Larry Slevinsky, PAg Gary Plohman, PEng Dr. Geza Racz, PhD February 2009.
ACKNOWLEDGEMENTS The authors express their gratitude to the Manitoba Rural Adaptation Council Inc. (MRAC) for the funding provided for the study. We are grateful to Puratone Corporation, particularly Roland Harder and Dean Gurney for their co-operation and assistance in construction of the settling tank, composting of the manure solids, and use of the facilities at the grower\finisher barn.. 2
TABLE OF CONTENTS ACKNOWLEGEMENTS.. 2 EXECUTIVE SUMMARY... 4 INTRODUCTION. 6 PROJECT OBJECTIVE 8 METHODOLOGY 9 Barn Location and Description 9 Description of Settling Tank 9 Pig Size, Feed and Manure Types...9 Experimental Procedures.10 Manure Analyses.11 Composting of Manure Solids..12 RESULTS AND DISCUSSION 13 Temperature 13 Potassium and NH 4 -N Contents.13 Settling of Manure Constituents 14 (A) Total Phosphorus (P)...14 (B) N to P Ratios Trial 1 to 3...16 (C) Percent Solids...16 Compost...17 SUMMARY, CONCLUSIONS AND RECOMMENDATIONS.19 LITERATURE CITED.21 APPENDIX A - TABLES OF MANURE ANALYSES...22 3
EXECUTIVE SUMMARY Some livestock producers, particularly in South Eastern Manitoba, do not have a large enough land base to utilize the P in manures if current regulations for soil P levels and P loadings are to be met. Removal of some or all of the P from the manure prior to land application is one means of reducing loadings of P to soils treated with manures. Separation of the P along with some manure solids from the liquid and soluble constituents would provide two types of manure. One manure fraction, the liquid fraction, would be low in P and could be used as a nitrogen fertilizer without elevating P levels in soils. The second fraction, the solids containing most of the P from the manure, could be efficiently used elsewhere as a P fertilizer. A study was conducted to evaluate the effectiveness of a settling tank (or gravity) in reducing phosphorus levels in manure. The settling tank was filled with hog manure and the rate of settling of solids and P determined. The manure solids which accumulated at the bottom of the tank were removed, mixed with a bulking agent and composted. Liquid hog manure was pumped into a settling tank (40ft x8 ft x4 ft in depth) and the rate of settling of P and solids investigated. Both P and solids settled out from liquid hog manure quite rapidly and completely when % solids in the manure was about 5.0% or less. Removal of P was about 75% whereas removal of solids was about 50 to 70% in the top 3 feet of manure within 24 hours. The N to P ratio of manures, initially about 5 to 6 to 1, was increased about 15 to 1 in about 48 hr and to 30 to 1 at termination of the trials. The rates of settling were rapid enough to warrant more study and development of settling tanks or similar systems to remove P and/or solids from liquid manures. The settling of both P and solids was slow in a trial in which the manure contained a high percent of solids (6.6%). Both the rate of settling and completeness of separation were poor. Studies are warranted to elucidate the reason(s) for the lack of separation in these instances. The handling and use of the manure solids requires further study. The volume of manure solids was about 15% of the total manure volume when both the solids and P 4
settled out reasonably well. In this study the manure solids were composted. The study contained herein showed this to be feasible. However, in some instances this may not be possible (economic and/ or environmentally), and thus other uses for the solids needs to be investigated. Both the systems for handling of the manure solids as well end uses (markets) for the manure solids have to be studied. In the studies contained herein the settling of phosphorus and solids was studied in a batch system, (ie) the settling tank was filled with manure and the settling of phosphorus and solids observed without any inflow or out flow of manure. Adoption and use of a settling system by producers would be much greater if the system could be operated as a flow through or continuous flow system even particularly if it operated satisfactorily for short periods of three to six months. The system would have to remove at least 50 % of the phosphorus from the liquid manure. Thus, it is recommended that the settling efficacy of systems, such as used in this study, be studied as a continuous flow system. A study of the use of the settling tank used in this study as a flow through system has been completed. A report will be available in May 2009. Results obtained indicate that the settling tank operated satisfactorily as a flow through system for about one month with the addition of about 1000 imperial gallons per day. 5
INTRODUCTION Manure applications or loadings have generally been based on nitrogen (N) requirements of crops. This results in a build up of soluble and total phosphorus (P) in soils since more P is usually applied then that used by crops. A build up of soluble P to high levels posses a risk of transfer of P from soil to surface and / or ground waters causing deleterious effects on water quality and restrictions to its use. The Province of Manitoba enacted regulations with respect to P levels in soils and loadings of P. Some producers (particularly in South Eastern Manitoba) do not have sufficient land to utilize the P produced in manures if regulations are to be met and hence producers need methods of reducing P in manures and loadings to soils. Removal of some or all the P from the manure prior to land application is one means of reducing P loadings to a limited land base. Separation of the P along with some manure solids from the liquid and soluble constituents would provide two types of manure. One manure fraction, the liquid fraction, would be low in P and could be used as a nitrogen fertilizer without elevating P levels in soils. The second fraction, the solids containing most of the P from the manure, could be efficiently used elsewhere as a P fertilizer (e.g. on P deficient soils prior to seeding to alfalfa or composted for other uses). A secondary issue resulting from the application of manures to land is the variability of nutrient application and resulting variability in soil nutrient levels and variations in crop growth. At present, the majority of hog producers in Manitoba use two-cell lagoons for storage of manure prior to land application. During manure removal, the manure in the first cell is mixed and a portion applied to land. Liquids from the second cell are then mixed with the manure in the first cell and applied to land. High solids and correspondingly high phosphorus content usually characterizes the manure contained in the first cell whereas the manure in the second cell is low in solids and P. Even with rigorous and continuous mixing, the manure withdrawn from the storages tends to vary in both solids and nutrient composition during emptying of the storage (Dick et al., 2003). In studies conducted by Slevinsky et al. (2001, 2002), nutrients in manure treated soils varied much more spatially than in soils treated with synthetic fertilizers. 6
There is limited information on gravity solid/liquid separation of hog manure and the subsequent handling of the two manure streams. Thus, a study was conducted to evaluate the effectiveness of a settling tank (or gravity) in reducing phosphorus levels in manure. The settling tank was filled with hog manure and the rate of settling of solids and P determined. The manure solids, which accumulated at the bottom of the tank were removed, mixed with a bulking agent and composted.. 7
PROJECT OBJECTIVE The objective of this investigation was: To investigate the potential for removal of P from hog manure by the use of a gravity settling tank. Liquid hog manure was pumped into a tank and the rate of settling of P and solids determined. 8
METHODOLOGY BARN LOCATION AND DESCRIPTION The study was conducted at the Puratone Corporation grower\finisher hog barn located on the N W ¼ 10 7 3E (Figure 1). The barn has a capacity of 6,800 pigs (Figure 2). Manure from the barn is initially stored in the barn, drained to a concrete pump out pit adjacent to the barn and then pumped to two earthen manure storage cells. DESCRIPTION OF SETTLING TANK Puratone staff in Niverville, Manitoba, constructed the settling tank. The tank was constructed using 18-gauge steel and was 40 ft long, 8 ft wide and 4 ft deep (Figure 3). The tank had a sampling compartment (4x8 ft) at one end of the tank to house sampling ports and to provide a means of emptying the tank at termination of each trial. Sampling ports consisted of a valve attached to a plastic tube that extended 4 ft into the tank to ensure that samples were representative of the manure in the tank (Figure 4). Valves were installed at sampling depths of 41.5, 37.5, 33.0, 29.0, 24.5, 20.0, 18.5, 8.5 and 3.0 inches from the bottom of the tank (Figure 5). The tank had no rigid cover, but was covered with a plastic tarpaulin to prevent rain water from entry and to reduce odors. PIG SIZE, FEED AND MANURE TYPES The hogs were about 17 to 18 weeks old at the start of trial 1 and weighed about 150 lb. The hogs were about 21 to 22 weeks old and weighed about 175 lb for trial 2 and were about 24 to 25 weeks old and weighed about 190 lb for trial 3. Phytase was used in all rations that consisted of corn, wheat, barley soybean meal, canola meal, corn distillers grains and wheat middling. Proportion of grains in the ration 9
Figure 1. Barn Location
Figure 2. Grower/Finisher Barn
Figure 3. View of Exterior of Settling Tank
Figure 4. Location of Sampling Tubes in the Settling Tank
Figure 5. Sampling Compartment and Sampling Valves
was varied with age of hog. Total P in the feed ranged from 0.50 % at hog size of 60 lb to 0.47 % at hog size of 190 lb. The manure used in the studies was pumped from the pump - out into the settling tank was from the upper portion of the manure collection pit for trial 1and trial 3 and from the bottom of the pit for trial 2. Nutrient contents and % solids were higher in the manure used for trial 2 than that of the manures used in trials 1 and 3. EXPERIMENTAL PROCEDURES In general, settling of solids and liquids was determined by filling the tank with liquid manure and measuring the manure constituents (e.g. solids and phosphorus) at various depths in the tank at various times after filling of the tank. Three trials were conducted. Trial 1 Approximately 1150 cubic feet (7120 imperial gallons) of liquid hog manure was pumped from the pump - out pit into the settling tank. Samples of manure were taken at 0 hours (tank filling) and at 5.5, 24, 53, 74, 169, 337, 529, 672, and 744 hours after filling at depths of 8.5, 18.5, 29.0 and 41.5 inches from the bottom of the tank. At 672 hours, samples were also taken at 37.5, 33.0, 24.5 and 20.0 inches. A sample of the manure at the surface in the tank and a sample of manure solids at the bottom of the tank were also taken at 672 hours. A sample of the manure solids at the bottom of the settling tank was also taken at 744 hours. Trial 1 was initiated on August 11, 2008 and terminated on September 11, 2008. Sampling protocols were as follows: About one-half liter of manure was purged from the sampling port and then a 1-liter sample was taken for analysis. The temperature of the manure was measured and samples stored in a cooler during transport to the laboratory. Samples were delivered to ALS Laboratory Group (Winnipeg, MB.) as soon as feasible after sampling. Samples were delivered to the laboratory within hours after sampling in all instances. 10
Trial 2 Trial 2 was initiated on September16, 2008 and terminated on September 29, 2008. Procedures for tank filling, sampling and sample handling were as described above. Sampling times were altered since data from trial 1 indicated that manure constituents were settling much more rapidly than anticipated. Manure samples were taken at 0, 1, 2, 4, 8, 24, 72, 168, and 336 hours after filling of the tank. Depths sampled were as noted for trial 1, except for samples taken at 48 hours when a sample was taken at a depth of 14 in since the sampling port at 8.5 in was plugged with manure solids. At 168 hours, in addition to the regular sampling depths, samples of manure at 37.5, 33.0, 24.5 and 20.0 inches from the bottom of the tank were taken. A sample of manure from the surface of the manure in the tank was also obtained. Two composite samples of manure were obtained during filling of the tank. Samples of manure solids were obtained at 72 and 168 hours at the 8.5 inch depth. Trial 3 Trial 3 started on September 30, 2008 and ended on October 14, 2008. Procedures were as outlined for the trials above. Samples were taken at 0, 1, 2, 4, 8, 24, 48, 72, 192, and 336 hours after tank filling at depths of 8.5, 18.5, 29, and 41.5 in. MANURE ANALYSES All manure samples were analyzed for total phosphorus (TP), total nitrogen (TN), ammonia nitrogen (NH 4 N), potassium (K), % solids and moisture content. In addition to the above parameters all samples of manure solids were analyzed for carbon (C) content. 11
COMPOSTING OF MANURE SOLIDS The liquid portion of manure in the tank was decanted after each trial by opening the sampling port valves in sequence from the top to the bottom of the tank. Each port was allowed to drain prior to opening of a lower valve. The depth of manure solids in the tank after trial 1 and 2 were measured. Depths of manure solids for trials 1 and 2 were about 7 and 11 in, respectively. The manure solids were mixed with wood chips as a bulking agent in the tank (Figure 6). The manure solids from trial 1 (168 cu ft) was mixed with about 830 lb (180 cu ft) of wood chips resulting in a ratio of about 1:1.1 manure to wood chips ratio. The manure solids from trial 2 (264 cu ft) was mixed with about 920 lb (200 cu ft) of wood chips. The manure-wood chip mixture was then placed in a shelter (10 x10 ft) (Figure 7). Manure solids from trials 1 and 2 were placed into a covered compost bin on September 11and September 30, respectively and moisture content and temperature recorded. The compost from trial 1 was sampled on September 11, 16, and 30, 2008. The compost from trial 2 was sampled on September 30 and October 14, 2008. Samples were analyzed for total P, total N, NH 4 -N, potassium, % moisture and % solids. The carbon content of the composts and the wood chips were also determined. 12
Figure 6. Addition of Wood Chips to Manure Solids in the Settling Tank
Figure 7. Manure Solids/Wood Chip Compost in Storage
RESULTS AND DISCUSSION TEMPERATURE The temperature of the manure samples from trials 1 and 2 varied from about 22 to14 C with the higher temperatures occurring at the start of the trial and the lower temperatures occurring at the end of the trial (Appendix A). The manure temperatures were about 18 C at the start and about 4 to 5 C at the termination of trial 3.Thus, the manures cooled considerably during each trial. POTASSIUM AND NH 4 -N CONTENTS The potassium and NH 4 -N contents of the manure remained relatively constant with time and depth (Appendix A). This was expected since these nutrients are highly water soluble and usually are distributed rather uniformly in both liquid and solid phases of manures. Total N also remained relatively constant with depth except for the depths at which manure solids accumulated. Total N in the manure solids was much higher than in the liquid portion due to the accumulation of organic nitrogen (solids). The data show that if the phosphorus settles in the tank, the decanted liquid would make an excellent nitrogen and potassium fertilizer of uniform composition and low in phosphorus. The potassium contents of the decanted liquids were the same as for whole manures (solids and liquids). The nutrient content of the manure in trial 2 was higher than that of manures used in trials 1 and 3. The % solids of manures in trial 2 were about two times that of manures used in trial 1 (6.6 versus 3.5%). 13
SETTLING OF MANURE CONSTITUENTS For the purposes of clarity the data for each trial and constituent is presented in two figures. The first figure shows data for the 0 to 169 hour sampling period whereas the second figure shows the data for the entire sampling period. (A) Total Phosphorus (P) Trial 1 Concentration of P declined rapidly with time except for the 8.5 inch depth (Figures 8a and b). P was depleted to low levels in the top two feet of manure in about 24 hours and was depleted to low levels to about 3 feet in 50 hours. P continued to slowly settle out of the manure during the first few hundred hours, but very large amounts of P settled out of the liquids during 0 to 24 or 0 to 48 hours. It is interesting to note that the P concentration at 169 hrs and 337 hrs declined to values of 2 to 3 and 1 to 2 lb/1000 gal and remained low thereafter. The C/Co values (measured concentration of P/ original concentration) for most sampling depths were about 0.25 after 24 hours indicating that P levels decreased to about 25% of original values (Table 1). C/Co values declined to 0.13 for all depths after 600 hours indicating that gravity separation of P from the manure can be very effective in removal of P. The settling of a large portion (~85% reduction in concentration) of P indicates that a large portion of the P in the liquid manure is present as a solid, most likely a precipitate with calcium and /or magnesium. C/Co values greater than 1.0 were encountered occasionally at manure depths near the bottom of the tank. This is to be expected and is a result of the settling out of P from the manure and accumulation at the bottom of the tank. About 1150 cubic feet of liquid manure was added to the tank for trial 1. After the tank was drained approximately 168 cubic feet of manure solids remained in the tank. Thus, the total volume of manure solids high in P that would need to be composted or transported off farm would be about 15% of that without separation. 14
Figure 8a. Total P Concentration at Various Depths With Time - Trial 1 (0 to 200 hr) Total P (lb/1000 Imp gal) 10 9 8 7 6 5 4 3 2 1 0 0 50 100 150 200 Time (hrs) 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom
Figure 8b. Total P Concentration at Various Depths With Time - Trial 1 (0 to 800 hr) Total P (lb/1000 Imp gal) 10 9 8 7 6 5 4 3 2 1 0 0 200 400 600 800 Time (hr) 8.5"from bottom 18.5" from bottom 29" from bottom 41.5" from bottom
Table 1. C/Co Values for Total P - Trial 1 Sampling Time (hr) Depth (in. from 5.5 24.5 53 74 169 337 529 672 bottom) 8.5 0.63 1.0 1.13 1.13 0.38 0.25 0.13 0.13 18.5 0.75 0.63 0.25 0.25 0.25 0.13 0.13 0.13 29.0 0.5 0.38 0.25 0.25 0.25 0.25 0.25 <0.13 41.5 0.25 0.38 0.25 0.25 0.25 0.25 0.13 0.13 Table 2. C/Co Values for Total P - Trial 2 Sampling Time (hr) Depth (in. from 1 2 4 8 24 48 72 168 336 bottom) 8.5 1.00 1.00 0.92 1.00 0.58 0.58 1.42 1.58 _ 18.5 1.08 1.00 1.00 1.00 0.58 0.50 0.92 0.92 0.75 29.0 1.00 0.75 0.92 0.92 0.58 0.83 0.75 0.92 0.67 41.5 1.00 0.83 0.75 0.75 0.58 0.83 0.75 0.92 0.58 Table 3. C/Co Values for Total P - Trial 3 Sampling Time (hr) Depth (in. from 1 2 4 8 24 48 72 192 336 bottom) 8.5 1.25 1.25 1.5 1.63 2.13 1.63 1.50 0.38 0.13 18.5 0.75 0.75 0.75 0.88 0.38 0.25 0.25 0.25 0.13 29.0 0.83 0.63 0.38 0.38 0.38 0.25 0.25 0.25 0.25 41.5 0.38 0.25 0.25 0.25 25.0 0.25 0.25 0.25 0.25
Trial 2 In trial 2, the depletion of P from the top few feet of manure was slow and relatively incomplete (Figures 9a and 9b)). Concentrations of P in the upper portion of the manure were still about 7 to11 lb/1000 gal and C/Co values varied from about 0.6 to0.9 even after 168 hours (Table 2). The results for trial 2 are very much in contrast to the results obtained in trial 1 in which the P settled out relatively rapidly and more completely. The reason(s) for the different behavior in rate of settling of P between the two trials is unknown at present. A major difference in manures used for the two separate trials was the solids content. The solids content of the manure in trial 1 was about 3.5% whereas the solids content of the manure used in trial 2 was 6.6 %. Worley and Das (2000) and Funk (2003) also observed that settling of P in liquid manures was impeded when % solids were high. The effects of solids on rate and amount of P precipitation and flocculation (settling) of P is unknown at present, but elucidation of the reactions responsible would be of great benefit in assessing the merits of using settling tanks (or gravity) for separation of P from liquid manures. About 1150 cubic feet of liquid manure was required to fill the settling tank for trial 2.The amount of manure solids after the liquid was decanted was 264 cubic feet resulting in a liquid to manure solids ratio of 4.36 to 1. Trial 3 The results obtained in trial 3 were very similar to the results obtained in trial 1 (Figures 10a and 10b). C/Co values of 0.25 were obtained in the top 3 feet on manure in 48 hours and C/Co values declined to 0.13 to 0.25 for all depths sampled at 336 hours. P concentration declined to 2 to 3 and 1 to 2 lb/1000 gal at 192 and 336 hours, respectively. The P concentration at 0 hours was 8 lb/1000 Imp gal. The removal (settling) of P was approximately 75%. The settling tank was not drained after trial 3 in order to accommodate other studies. 15
Total P (lb/1000 Imp gal) 20 18 16 14 12 10 8 6 4 2 0 Figure 9a. Total P Concentration at Various Depths With Time - Trial 2 (0 to 200 hr) 0 50 100 150 200 Time (hrs) 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom
Figure 9b. Total P Concentration at Various Depths With Time - Trial 2 (0 to 400 hr) Total P (lb/1000 Imp gal) 20 18 16 14 12 10 8 6 4 2 0 0 100 200 300 400 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom Time (hrs)
18 Figure 10a. Total P Concentration at Various Depths With Time - Trial 3 (0 to 200 hr) 16 14 Total P (lb/1000 Imp gal) 12 10 8 6 4 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 2 0 0 50 100 150 200 250 Time (hr)
Total P (lb/1000 Imp gal) 18 16 14 12 10 8 6 4 2 0 Figure 10b. Total P Concentration at Various Depths With Time - Trial 3 (0 to 400 hr) 0 100 200 300 400 Time (hr) 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom
(B) N to P Ratios Trials 1 to 3 The N to P ratio of manures in the top layers of the settling tank changed very markedly during settling of the manure constituents. The N to P ratio of the manures placed into the settling tank varied from about 5 to 1 to 6 to 1 (values calculated from values in Appendix A). In trial 1 and 3, trials in which the manure constituents settled out quite rapidly and completely, the N to P ratios in the upper layers of manures increased to values of about 15 to 1 in 48 hr and to values of about 30 to 1 at termination of the trials. In trial 2, N to P ratios increased to about 7:10:1 after at about 48 hours and remained at these values until termination of the trial. Applying manures with N to P ratios such as those encountered above in the upper layers of manure will not result In high levels of soil phosphorus even when the manures are applied based on nitrogen requirements of crops. (C) Percent Solids Trial 1 Percent solids was 3.5% in the manure when placed into the settling tank. Percent solids decreased rapidly in the top 3 feet of manure to about 2.0 % in 24 to 48 hours (Figures11a and 11b). Percent solids in the liquids continued to slowly decline after 48 hours to about 1.5 to 1.6% after several hundred hours. Percent solids in the manure at the bottom of the tank increased as expected. The C/Co values for total solids were higher than the C/Co values for P for the top layers of manure at all sampling times (Table 4). The lowest value for C/Co for solids was 0.43 whereas the lowest value of C/Co for P was 0.13. The settling of solids other than P was not as rapid and not as great as for P alone. Approximately 50 percent of the solids settled out of the top layers within 24 hr and then remained relatively constant 16
Figure 11a. % Solids at Various Depths With Time - Trial 1 (0 to 200 hr) % Solids 6 5 4 3 2 1 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 0 0 50 100 150 200 Time (hrs)
Figure 11b. % Solids at Various Depths With Time - Trial 1 (0 to 800 hr) 6 5 4 % Solids 3 2 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 1 0 0 100 200 300 400 500 600 700 800 Time (hr)
Table 4. C/Co Values for % Solids - Trial 1 Sampling Time (hr) Depth (in. from 5.5 24.5 53 74 169 337 529 672 bottom) 8.5 0.74 0.97 1.37 1.23 0.63 0.51 0.46 0.43 18.5 0.74 0.74 0.54 0.51 0.60 0.43 0.46 0.43 29.0 0.66 0.57 0.51 0.49 0.60 0.46 0.46 0.46 41.5 0.49 0.49 0.54 0.57 0.66 0.46 0.46 0.43 Table 5. C/Co Values for % Solids Trial 2 Sampling Time (hr) Depth (in. from 1 2 4 8 24 48 72 168 336 bottom) 8.5 1.03 1.05 1.02 1.09 0.98 0.76 1.76 1.91 _ 18.5 0.95 1.00 0.94 1.08 0.83 0.76 0.76 0.97 0.91 29.0 0.95 1.09 0.89 0.94 0.83 0.77 0.82 0.89 0.83 41.5 0.79 0.85 0.74 0.68 0.79 0.77 0.77 0.76 0.82 Table 6. C/Co Values for % Solids - Trial 3 Sampling Time (hr) Depth (in. from 1 2 4 8 24 48 72 168 336 bottom) 8.5 1.02 0.91 0.85 1.47 1.90 1.05 0.87 0.38 0.33 18.5 0.55 0.55 0.60 0.55 0.42 0.31 0.31 0.38 0.33 29.0 0.45 0.56 0.38 0.36 0.38 0.33 0.31 0.36 0.29 41.5 0.43 0.38 0.29 0.31 0.36 0.31 0.29 0.31 0.31
with time. About 43 percent of the solids were in the liquid portion of the manure even at 672 hr. Trial 2 Percent solids in the top layers of manure (~top 3 feet) declined to about 5.0% from 6.6% in 48 hours, but then increased to about 6.0% at 168 and 336 hours (Figures 12a and b). C/Co values at 336 hours (termination of the trial) were about 0.9 indicating that 90% of solids remained in the liquid phase of the manure in this study (Table 5). The lack of settling of solids was somewhat unexpected but mirrored the results obtained for the settling of P. As noted for P, additional studies to elucidate the reason(s) for the lack of settling of solids are warranted. Trial 3 The settling of solids in trial 3 followed patterns outlined for trial 1 (Figures 13a and b). There was significant depletion of solids in the top layers of manure even during the first one hour after filling the tank and about 60% of the solids settled out of the top 3 feet in 24 hours..about 65 to 70 % of solids settled out of the liquid when the trial was terminated (336 hr). The C/Co values for solids for the top 3 feet of manure were only somewhat higher than C/Co values for P and declined to values of about 0.3 in 72 hours. Both solids and P settled out quite rapidly and completely in trial 3 (Table 6). COMPOST The purpose for composting the solids was to determine whether or not composting of the manure solids would be feasible. The goal was to achieve a carbon to nitrogen ratio of 20 to 30:1, a moisture content of 50 to 60 percent and a temperature of 55 to 65 0 C. The manure solids from the two trials had percent solids content of 16 to 17 percent (Table 7). Total N, total P and other nutrient constituents were much higher for manure solids than for whole manures (liquid and manure solids) as expected. Thus, 17
Figure 12a. % Solids at Various Depths With Time - Trial 2 (0 to 200 hr) 14 12 10 % Solids 8 6 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 4 2 0 0 20 40 60 80 100 120 140 160 180 Time (hr)
Figure 12b. % Solids at Various Depths With Time - Trial 2 (0 to 400 hr) % Solids 14 12 10 8 6 4 2 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 0 0 100 200 300 400 Time (hrs)
Figure 13a. % Solids at Various Depths With Time - Trial 3 (0 to 200 hr) 12 10 % Solids 8 6 4 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 2 0 0 50 100 150 200 250 Time (hr)
Figure 13b. % Solids at Various Depths With Time - Trial 3 (0 to 400 hr) % Solids 12 10 8 6 4 2 8.5" from bottom 18.5" from bottom 29" from bottom 41.5" from bottom 0 0 100 200 300 400 Time (hr)
considerable concentration of nutrients from the liquid phase to the manure solids occurred, particularly for total P and total N. The concentration of all nutrients decreased, as expected, when the bulking agent was added. Total N decreased by about five fold. Compost 1 was allowed to stand for 19 days and compost 2 for 14 days prior to removal from the compost bin. Percent moisture for compost 1 declined from about 80 to 60 % during 19 days of composting. Moisture content for compost 2 declined from about 75 to 70 % in 14 days. Water from a severe rainfall event entered the compost bin and is the most likely reason for the high moisture content. Temperature for compost 1 increased to 66 0 C whereas temperature for compost 2 increased to 36 0 C. Composting of compost 2 occurred in late fall when air temperatures were about zero 0 C in the morning. The C to N ratio for the manure solids prior to composting was 12.0:1 and 15.6:1 for compost 1 and compost 2, respectively (Table 7). The C to N ratio for compost 1 was about 20 to 1 and after 19 days of composting was about 34 to 1. The C to N ratio for compost 2 and the manure solids used for compost 2 were very similar and varied from 16 to 17 to 1. The C to N ratios for the composts were in the range normally encountered for manure composts. 18
Table 7. Some Characteristics of Manure Solids and Compost Trial 1 - Compost 1 TP TN NH4 - N K Total Solids % Total C Temp C/N (%) Moisture C. Ratio Manure Solids 32* 57 39 14 15.8 84.2 689 18.9 12.0 : 1 Compost (Initial) 1.2** 9.3 7.0 0.6 18.8 81.2 155 _ Compost at 5 days 1.4 12.3 4.3 < 0.3 30.3 69.7 245 66 19.9 : 1 Compost at 19 days 1.7 9.8 5.0 0.8 37.2 62.8 334 34.0 : 1 Trial 2 - Compost 2 Manure Solids 21 53 49 31 17.4 82.6 828 _ 15.6 : 1 Compost (Initial) 0.8 11.5 8.1 1.1 24.2 75.8 195 12 17.0 : 1 Compost at 14 days 4.4 12.8 9.5 5.1 29.4 70.6 224 36 17.5 : 1 * Manure Solids Values expressed in lb/1000 gal ** Compost Values expressed in lb/ton
SUMMARY, CONCLUSIONS AND RECOMMENDATIONS Liquid hog manure was pumped into a settling tank (40ft x8 ft x4 ft in depth) and the rate of settling of P and solids investigated. Both P and solids settled out from liquid hog manure quite rapidly and completely when % solids in the manure was about 5.0% or less. Removal of P was about 75% whereas removal of solids was about 50 to 70% in the top 3 feet of manure within 24 hours. The N to P ratio of manures, initially about 5 to 6 to 1, was increased to about 15 to 1 in about 48 hr and to 30 to 1 at termination of the trials. The rates of settling were rapid enough to warrant more study and development of settling tanks or similar systems to remove P and/or solids from liquid manures. The settling of both P and solids was slow in a trial in which the manure contained a high percentage of solids (6.6%). Both the rate of settling and completeness of separation were poor. Studies are warranted to elucidate the reason(s) for the lack of separation in these instances. The use of precipitants and/ or flocculants in increasing rate and completeness of separation should be one factor examined. It should be noted, however, that liquid hog manures average about 3.5% solids and hence both P and solids would settle out by gravity in a settling tank or similar structures reasonably well. The handling and use of the manure solids requires further study. The volume of manure solids was about 15% of the total manure volume when both the solids and P settled out reasonably well. In this study the manure solids were composted. The study contained herein showed this to be feasible. However, in some instances this may not be possible (economic and/ or environmentally), and thus other uses for the solids needs to be investigated. Both the systems for handling of the manure solids as well end uses (markets) for the manure solids have to be studied. The manure solids were reasonably rich in nutrients and organic matter and hence would be a good soil amendment fertilizer. In the studies contained herein the settling of phosphorus and solids was studied in a batch system, (ie) the settling tank was filled with manure and the settling of phosphorus 19
and solids observed without any inflow or out flow of manure. Adoption and use of a settling system by producers would be much greater if the system could be operated as a flow through or continuous flow system even particularly if it operated satisfactorily for short periods of three to six months. The system would have to remove at least 50 % of the phosphorus from the liquid manure. Thus, it is recommended that the settling efficacy of systems, such as used in this study, be studied as a continuous flow system. A study of the use of the settling tank used in this study as a flow through system has been completed. A report will be available in May 2009. Results obtained indicate that the settling tank operated satisfactorily as a flow through system for about one month with the addition of about 1000 imperial gallons per day. 20
LITERATURE CITED Dick, S. et al, 2003. A Detailed Analysis of Ammonia, Total Kjeldahl Nitrogen, Phosphorus, Potassium and Moisture Content Profile Every 5 % Increment Throughout the Pump Out of a Circular, Single Cell and Two Cell Manure Storage System. A report presented to the Manitoba Livestock Management Initiative Inc. Funk, T. 2003. Gravity Tank Low Cost Way to Separate Manure, Control Odor. The Pig Site. College of Agricultural, Consumer and Environmental Sciences. University of Illinois Slevinsky L F. et al, 2001. Soil Sampling of Manured an Non-Manured Fields. A report presented to the Manitoba Livestock Management Initiative Inc. Slevinsky L F. et al, 2002. Soil Sampling of Manured and Non-Manured Fields in Grass Forage Production. A report presented to the Manitoba Livestock Management Initiative Inc. Worley, J. W. and K. C. Das. 2000. Swine Manure Solids Separation and Composting Using Alum. Appl. Eng. Agric. 16:555-561. 21
APPENDIX A Tables of Manure Analyses for Trial 1, 2 and 3 22
TABLE 1 - TRIAL1 MANURE ANALYSES OF SAMPLES TAKEN FROM SETTLING TANK - Aug. 11 to Sept. 11/08 TIME DEPTH DATE TP TN NH4 - N K TOTAL % TOTAL MANURE (hours) (inches) LB/1000 LB/1000 LB/1000 LB/1000 SOLIDS MOISTURE CARBON TEMP. O C GAL GAL GAL GAL % LB/TON 0 (filling) 11-Aug 8 40 27 16 3.5 96.5 21.1 5.5 8.5 11-Aug 5 35 26 16 2.6 97.4 21.1 18.5 11-Aug 6 35 27 16 2.6 97.4 21.6 29.0 11-Aug 4 33 26 16 2.3 97.7 22.9 41.5 11-Aug 2 29 25 16 1.7 98.3 21.9 24.5 8.5 12-Aug 8 38 26 16 3.4 96.6 21.6 18.5 12-Aug 5 34 27 16 2.6 97.4 21.6 29.0 12-Aug 3 29 25 16 2.0 98.0 21.1 41.5 12-Aug 3 29 25 16 1.7 98.3 21.0 53.25 8.5 13-Aug 9 42 29 15 4.8 95.2 21.9 18.5 13-Aug 2 31 25 15 1.9 98.1 22.4 29.0 13-Aug 2 30 25 15 1.8 96.2 22.7 41.5 13-Aug 2 31 25 15 1.9 98.1 22.9 73.75 8.5 14-Aug 9 44 29 14 4.3 95.7 22.4 18.5 14-Aug 2 30 24 15 1.8 98.2 22.3 29.0 14-Aug 2 31 25 15 1.7 98.3 22.1 41.5 14-Aug 2 31 25 15 1.8 98.2 22.3 169 8.5 18-Aug 3 31 26 15 2.2 97.8 24.7 18.5 18-Aug 2 29 25 15 2.1 97.9 24.5 29.0 18-Aug 2 30 25 15 2.1 97.9 24.5 41.5 18-Aug 2 30 25 15 2.3 97.7 25.1 337 8.5 25-Aug 2 31 26 16 1.8 98.2 18.1 18.5 25-Aug 1 31 26 15 1.5 98.5 18.0 29.0 25-Aug 2 31 27 16 1.6 98.4 18.3 41.5 25-Aug 2 32 27 16 1.6 98.4 18.5 529 8.5 02-Sep 1 31 27 14 1.6 98.4 18.7 18.5 02-Sep 1 32 28 15 1.6 98.4 19.0 29.0 02-Sep 2 30 27 14 1.6 98.4 19.3 41.5 02-Sep 2 31 27 15 1.6 98.4 19.4 672 3.0 08-Sep 6 36 29 16 3.2 96.8 25.3 12.2 8.5 08-Sep 1 31 27 17 1.6 98.4 12.3 18.5 08-Sep 1 31 27 17 1.5 98.5 12.8 29.0 08-Sep <1 31 28 16 1.6 98.4 13.0 41.5 08-Sep 1 31 27 16 1.6 98.4 13.1 672 8.5 08-Sep 1 31 28 17 1.5 98.5 15.4 18.5 08-Sep 1 31 27 17 1.5 98.5 15.6 20.0 08-Sep 1 31 28 17 1.5 98.5 14.1 24.5 08-Sep 1 31 27 16 1.5 98.5 14.4 29.0 08-Sep 1 32 27 17 1.6 98.4 14.1 33.0 08-Sep 1 31 27 16 1.5 98.5 14.1 37.5 08-Sep 1 31 27 17 1.5 98.5 13.8 41.5 08-Sep 1 31 27 16 1.5 98.5 15.6 surface 08-Sep 1 31 26 17 1.6 98.4 13.0 744 sludge 11-Sep 32 57 39 14 15.8 84.2 689 (lb/ 18.9 1000 gal) compost 1 11-Sep 1.2 (lb/ton) 9.3 (lb/ton) 7.0 (lb/ton) 0.6 (lb/ton) 18.8 81.2 155 wood shavings 11-Sep 47 in % 1200 compost 1 30-Sep 1.7 (lb/ton) 9.8 (lb/ton) 5.0 (lb/ton) 0.80 (lb/ton) 37.2 62.8 334
TABLE 2 - TRIAL 2 MANURE ANALYSES OF SAMPLES TAKEN FROM SETTLING TANK Sept.16 to Sept. 29/08 TIME DEPTH DATE TP TN NH4 - N K TOTAL % TOTAL MANURE (hours) (inches) LB/1000 LB/1000 LB/1000 LB/1000 SOLIDS MOISTURE CARBON TEMP. O C GAL GAL GAL GAL % LB/TON 0 (filling) 16-Sep 12 72 47 26 7.1 92.9 19.6 0 (filling) 16-Sep 11 71 50 27 6.1 93.9 19.5 1 8.5 16-Sep 12 72 50 27 6.8 93.2 21.6 18.5 16-Sep 13 73 50 28 6.3 93.7 21.1 29.0 16-Sep 13 72 49 29 6.3 93.7 21.0 41.5 16-Sep 12 70 50 30 5.2 94.6 19.6 compost 1 16-Sep 1.7 (lb/ton) 9.8 (lb/ton) 4.9 (lb/ton) 1.4 (lb/ton) 33.0 67.0 282 45.0 2 8.5 16-Sep 12 70 50 26 6.9 93.1 22.3 18.5 16-Sep 12 72 49 25 6.6 93.4 21.9 29.0 16-Sep 9 66 51 19 7.2 92.8 22.1 41.5 16-Sep 10 67 50 23 5.6 94.4 21.9 4 8.5 16-Sep 11 69 49 26 6.7 93.3 21.4 18.5 16-Sep 12 73 49 27 6.2 93.8 21.3 29.0 16-Sep 11 71 50 27 5.9 94.1 21.1 41.5 16-Sep 9 67 48 27 4.9 95.1 21.1 8 8.5 16-Sep 12 73 50 27 7.2 92.8 21.8 18.5 16-Sep 12 72 47 27 7.1 92.9 20.7 29.0 16-Sep 11 72 50 27 6.2 93.8 21.1 41.5 16-Sep 9 67 48 26 4.5 95.5 21.4 24 8.5 17-Sep 7 75 48 26 6.5 93.5 19.3 18.5 17-Sep 7 70 50 25 5.5 94.5 19.5 29.0 17-Sep 7 70 50 25 5.5 94.5 18.9 41.5 17-Sep 7 69 50 28 5.2 94.8 18.2 48 14.0 18-Sep 7 69 49 26 5.0 95.0 19.3 18.5 18-Sep 6 69 50 24 5.0 95.0 19.2 29.0 18-Sep 10 69 49 25 5.1 94.9 18.4 41.5 18-Sep 10 69 51 26 5.1 94.9 18.7 Note: sample taken at 14 as value at 8.5 was plugged Compost 65.0 Temp. 72 8.5 - sludge 19-Sep 17 79 51 24 11.6 88.4 17.4 18.5 19-Sep 11 66 50 27 5.0 95.0 18.7 29.0 19-Sep 9 59 49 24 5.4 94.6 18.5 41.5 19-Sep 9 68 50 23 5.1 94.9 18.3 168 8.5 - sludge 22-Sep 19 79 53 29 12.6 87.4 19.4 18.5 22-Sep 11 68 51 29 6.4 93.6 19.1 29.0 22-Sep 11 68 51 30 5.9 94.1 19.0 41.5 22-Sep 11 69 52 30 5.0 95.0 19.5 336 8.5 29-Sep 24 5.4 94.6 11.9 18.5 29-Sep 9 68 54 28 6.2 93.8 13.0 20.0 29-Sep 9 68 52 27 6.0 94.0 12.8 24.5 29-Sep 8 67 52 24 5.9 94.1 13.5 29.0 29-Sep 8 68 53 23 5.5 94.5 13.1 24.5 29-Sep 8 67 52 24 5.9 94.1 13.5 33.0 29-Sep 7 67 52 22 5.4 94.6 12.6 37.5 29-Sep 7 67 52 23 5.2 94.8 12.4 41.5 29-Sep 7 67 52 24 5.4 94.6 10.9 surface 29-Sep 7 69 51 24 5.4 94.6 11.9 compost 1 29-Sep 1.4 (lb/ton) 12.3 (lb/ton) 4.3 (lb/ton) <0.3 (lb/ton) 30.3 69.7 245 66 0 C Note: sludge samples at 8.5 and 3.0 depths were not taken as valves were plugged with solids Note: a sludge and compost sample were taken on Sept 30/08
TABLE 3 - TRIAL 3 MANURE ANALYSES OF SAMPLES TAKEN FROM SETTLING TANK Sept. 30 to Oct. 14/08 TIME DEPTH DATE TP TN NH4 - N K TOTAL % TOTAL MANURE (hours) (inches) LB/1000 LB/1000 LB/1000 LB/1000 SOLIDS MOISTURE CARBON TEMP. O C GAL GAL GAL GAL % LB/TON 0 30-Sep 8 45 33 18 5.5 94.5 18.0 1 8.5 30-Sep 10 43 30 14 5.6 94.4 16.9 18.5 30-Sep 6 36 28 14 3 97.0 17.2 29.0 30-Sep 5 35 28 14 2.5 97.5 17.1 41.5 30-Sep 3 32 26 14 2.4 97.6 17.6 sludge 30-Sep 21 53 49 31 17.4 82.6 828 (lb/ 1000/gal) 12.0 compost 2 30-Sep 0.80 (lb/ton) 11.5 (lb/ton) 8.1 (lb/ton) 1.1 (lb/ton) 24.2 75.8 195 2 8.5 30-Sep 10 44 30 13 5.0 95.0 16.8 18.5 30-Sep 6 35 28 14 3.0 97.0 16.6 29.0 30-Sep 5 35 27 14 3.1 96.9 16.4 41.5 30-Sep 2 30 25 14 2.1 97.9 16.3 4 8.5 30-Sep 12 45 31 14 4.7 95.3 16.7 18.5 30-Sep 6 37 28 14 3.3 96.7 17.7 29.0 30-Sep 3 33 26 14 2.1 97.9 17.6 41.5 30-Sep 2 30 25 14 1.6 98.4 18.2 8 8.5 30-Sep 13 50 31 14 8.1 91.9 13.3 18.5 30-Sep 7 38 28 15 3.0 97.0 16.1 29.0 30-Sep 3 31 26 14 2.0 98.0 16.4 41.5 30-Sep 2 31 26 14 1.7 98.3 16.5 24 8.5 01-Oct 17 55 34 16 10.5 89.5 15.3 18.5 01-Oct 3 33 27 14 2.3 97.7 14.8 29.0 01-Oct 3 31 26 14 2.1 97.9 13.7 41.5 01-Oct 2 31 26 15 2.0 98.0 14.3 48 8.5 02-Oct 13 49 32 15 5.8 94.2 13.3 18.5 02-Oct 2 31 26 14 1.7 98.3 14.0 29.0 02-Oct 2 31 26 14 1.8 98.2 14.1 41.5 02-Oct 2 31 26 15 1.7 98.3 13.4 compost - temp. 20.0 72 8.5 03-Oct 12 45 31 15 4.8 95.2 10.5 18.5 03-Oct 2 30 27 16 1.7 98.3 11.6 29.0 07-Oct 2 31 27 13 2.0 98.0 10.8 41.5 03-Oct 2 30 27 15 1.6 98.4 11.5 compost - temp. 30.0 192 8.5 07-Oct 3 33 27 13 2.1 97.9 11.8 18.5 07-Oct 2 31 27 12 1.8 98.2 11.2 29.0 07-Oct 2 31 27 13 2.0 98.0 10.8 41.5 07-Oct 2 31 27 13 1.7 98.3 10.5 compost - temp. 40.0 336 surface 14-Oct 1 29 25 14 1.6 98.4 2.6 8.5 14-Oct 1 31 27 15 1.8 98.2 4.2 18.5 14-Oct 1 31 27 13 1.8 98.2 4.6 29.0 14-Oct 2 31 27 14 1.6 98.4 4.8 41.5 14-Oct 2 31 27 15 1.7 98.3 5.7 3.0 14-Oct bottom 3 inches (no sample was taken as valve was plugged - the manure at this depth was watery with solids present) compost 2 14-Oct 4.4 (lb/ton) 12.8 (lb/ton) 9.5 (lb/ton) 5.1 (lb/ton) 29.4 70.6 224 36.0