397 12 CAFO Component Design * And if you think the lagoons and exhaust fans make a stink, wait until you get a whiff of a eld fresh spread with hog poop. The ammonia will burn your eyes out of your head. Your hair will fall out. They could make the stink better by coverin over the waste ponds or aeratin, but that costs money. Cheaper just to let it sit there. And the state don’t care. (Proulx, 2002, p. 113) 12.1 INTRODUCTION (USDA, 1996) A CAFO can function for any one or all of the following purposes: production, collection, storage, treatment, transfer, and ultilization. Production is the function of the amount and nature of agri- cultural waste generated by an agricultural enterprise. Collection refers to the initial capture and gathering of waste from the point of origin or deposition to a collection point. Storage is the tem- porary containment of the waste. Treatment is any function designed to reduce the pollution poten- tial of waste, including physical, biological, and chemical treatment. It includes activities that are sometimes considered pretreatment, such as the separation of solids. Transfer refers to the move- ment and transportation of waste throughout the system and includes the transfer of waste from the collection point to the storage facility, to the treatment facility, and to the utilization site. Utiliza- tion includes recycling reusable waste products and reintroducing nonreusable waste products into the environment. These functions are carried out by planning, applying, and operating individual components. A component can be a piece of equipment, such as a pump; a structure, such as a waste storage tank; or an operation, such as composting. The combination of the components should allow the exibility needed to efciently handle all forms of waste generated for a given enterprise. In addi - tion, the components must be compatible and integrated with each other. All components should be designed to be simple, manageable, and durable, and they should require low maintenance. In this chapter, we discuss these components under section headings that describe the function that they are to accomplish. 12.2 PRODUCTION The production function includes components that affect the volume and consistency of the agri- cultural waste produced. Roof gutters and downspouts and diversion to exclude clean water from areas of waste are examples of components that reduce the volume of waste material that needs management. Fences and walls that facilitate collection of waste conne the cattle, thus increasing the volume of waste collected. 12.2.1 roof runoff ManageMenT Roof runoff should be diverted from feedlots and manure storage areas unless it is needed for some use, such as dilution water for waste storage ponds or treatment lagoons. As illustrated in * This chapter is a modied version of NRCS/USDA (1992), National Engineering Handbook, Part 651. Agricultural Waste Management Field Handbook, chap. 10. 7098.indb 397 4/25/07 5:32:26 PM © 2007 by Taylor & Francis Group, LLC 398 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Figure 12.1, roof gutters and downspouts with underground connections to open channel outlets can accomplish this. Gutters and downspouts may not be needed if the roof drainage does not come into contact with areas accessible to livestock. The area of a roof that can be served by a gutter and downspout system is controlled by either the ow capacity of the gutter (channel ow) or by the capacity of the downspout (orice ow). The gutter’s capacity may be computed using Manning’s equation. Design of a gutter and downspout system is based on the runoff from a 10-year frequency, 5-minute rainfall, except that a 25-year fre - quency, 5-minute rainfall is used for exclusion of roof runoff from waste treatment lagoons, waste storage ponds, or similar practices. Important point: The common design equation for uid ow in open channels (of any conguration) is Manning’s formula. A procedure for the design of roof gutters and downspouts follows: Step 1—Compute the capacity of the selected gutter size. This may be computed using Man- ning’s equation. Using the recommended gutter gradient of ¹/₁₆ in./ft and a Manning’s roughness coefcient of 0.012, this equation can be expressed as: q A r g g = × ×0.01184 0 67. (12.1) where: q g = Capacity of gutter, ft 3 /sec. A g = Cross sectional area of gutter, in. 2 . r = A g /wp, inches. wp = Wetted perimeter of gutter, inches. • Waterway Downspout Transport pipe Gutter Concrete channel to waste storage pond Fe e dlot ru noff Underground outlet FIGURE 12.1 Roof gutter and downspout. (Source: NRCS/USDA, 1992, p. 10-1.) 7098.indb 398 4/25/07 5:32:27 PM © 2007 by Taylor & Francis Group, LLC CAFO Component Design 399 Step 2—Compute capacity of downspout. Using an orice discharge coefcient of 0.65, the ori- ce equation may be expressed as: q A h d d = × ×0.010457 0.5 (12.2) where: q d = Capacity of downspout, ft 3 /sec. A d = Cross sectional area of downspout, in. 2 . h = Head, inches (generally the depth of the gutter minus 0.5 in.). Step 3—Determine whether the system is controlled by the gutter capacity or downspout capacity and adjust number of downspouts if desired. Nd qg qd= (12.3) where: N d = Number of downspouts. If N d is less than 1, the system is gutter-capacity controlled. If it is equal to or greater than 1, the system is downspout capacity controlled unless the number of downspouts is equal to or exceeds N d . Step 4—Determine the roof area that can be served, based on the following equation: Ar q P= × 3 600, (12.4) where: A r = Area of roof served, ft 2 . q = Capacity of system, either q g or q d whichever is smallest, ft 3 /sec. P = 5-minute precipitation for appropriate storm event, inches. Important point: The above procedure is a trial and error process. Different sizes of gutters and downspouts should be evaluated, as well as multiple downspouts, to determine the best gutter and downspout system to serve the roof area involved. 12.2.2 runoff ConTrol All livestock facilities in which the animals are housed in open lots or the manure is stored in the open must deal with runoff. As illustrated in Figure 12.2, “clean” runoff from land surrounding livestock facilities should be diverted from barns, open animal concentration areas, and waste stor - age or treatment facilities. Important point: Diversions are to be designed according to National Resource Conserva- tion Service (NRCS) Conservation Practice Standard, Diversion, Code 362 (USDA 1985). Diversion channels must be maintained to remain effective. If vegetation is allowed to grow tall, the roughness increases and the channel velocity decreases, causing possible channel overow. Therefore, vegetation should be periodically mowed. Earth removed by erosion from earthen channels should be replaced. Unvegetated, earthen channels should not be used in regions of high precipitation because of potential erosion. • • 7098.indb 399 4/25/07 5:32:29 PM © 2007 by Taylor & Francis Group, LLC 400 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) 12.3 COLLECTION Livestock and poultry manure collection often depends on the degree of freedom that is allowed the animal. If animals are allowed freedom of movement within a given space, the manure produced will be deposited randomly. Components that provide efcient collection of animal waste include paved alleys, gutters, and slatted oors with associated mechanical and hydraulic equipment as described in the sections below. 12.3.1 alleyS Alleys are paved areas where animals walk. They generally are arranged in straight lines between animal feeding and bedding areas. On slatted oors, animal hoofs work the manure through the slats into the alleys below, and the manure is collected by ushing or scraping the alleys. 12.3.1.1 Scrape Alleys and Open Areas Figure 12.3 illustrates a scrape alley used in dairy barns. Two kinds of manure scrapers are used to clean alleys: mechanical and tractor scrapers. A mechanical scraper is dedicated to a given alley Collection gutter Waste storage pond Slope Diversion FIGURE 12.2 Diversion of “clean” water around feedlot. Free stalls Cross conveyor to storage Clean Return FIGURE 12.3 Scrape alley used in dairy barns. (Source: NRCS/USDA, 1992, p. 10-4.) 7098.indb 400 4/25/07 5:32:30 PM © 2007 by Taylor & Francis Group, LLC CAFO Component Design 401 and propelled using electrical drives attached by cables or chains. The drive units are often used to power two mechanical scrapers that are traveling in opposite directions in parallel alleys in an oscillating manner. Some mechanical scrapers are in alleys under slatted oors. A tractor scraper can be used in irregularly shaped alleys and open areas where mechanical scrapers cannot function properly. It can be a blade attached to either the front or rear of a tractor or a skid-steer tractor with a front mounted bucket. The width of the alleys depends on the desires of the producer and the width of available equip - ment. Scrape alley widths typically vary from 8 to 14 ft for dairy and beef cattle and from 3 to 8 ft for swine and poultry. 12.3.1.2 Flush Alley Flushing is also used to clean alleys. Grade is critical and can vary between 1.25% and 5%. It may change for long ush alleys. The alley should be level perpendicular to the centerline. The amount of water used for ushing is also critical. An initial ow depth of 3 in for underslat gutters and 4 to 6 in for open alleys is necessary. The length and width of the ush alley are also factors. Most ush alleys should be less than 200 ft long. The width generally varies from 3 to 10 ft, depending on animal type. For underslat gutters and alleys, channel width should not exceed 4 ft. The width of open ush alleys for cattle is frequently 8 to 10 ft. Important point: Flush alleys and gutters should be cleaned at least twice per day. For pump ushing, each ushing event should have a minimum duration of 3 to 5 minutes. Table 12.1 and Table 12.2 indicate general recommendations for the amount of ush volume. Table 12.3 gives the minimum slope required for ush alleys and gutters. Figure 12.4 and Figure 12.5 illustrate ush alleys. Several mechanisms are used for ushing alleys. The most common rapidly empties large tanks of water or uses high-volume pumps. Several kinds of ush tanks are used (Figure 12.6). One known as a tipping tank pivots on a shaft as the water level increases. At a certain design volume, the tank tips, emptying the entire amount in a few seconds, which causes a wave that runs the length of the alley. Some ush tanks have manually opened gates. These tanks are emptied by opening a valve, a standpipe, a pipe plug, or a ush gate. Float switches can be used to control ushing devices. • TABLE 12.1 Recommended Total Daily Flush Volumes Animal type gal/head Swine Sow and litter 35 Prenursery pig 2 Nursery pig 4 Growing pig 10 Finishing pig 15 Gestating sow 25 Dairy cow 100 Beef feeder 100 Source: MWPS (1985). 7098.indb 401 4/25/07 5:32:30 PM © 2007 by Taylor & Francis Group, LLC 402 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) TABLE 12.2 Flush Tank Volumes and Discharge Rates Initial flow depth, in Tank volume, gal/ft of gutter width Tank discharge rate, gpm/ft of gutter width Pump discharge gpm/ft of gutter width 1.5 30 112 55 2.0 40 150 75 2.5 45 195 95 3.0 55 255 110 4.0 75 615 150 5.0 100 985 175 6.0 120 1,440 200 Source: MWPS (1985). TABLE 12.3 Minimum Slope for Flush Alleys Underslat alley Open alley narrow width (< 4 ft) Open alley wide width (> 4 ft) Initial ow depth, in 3.0 1.5 2.0 2.5 4.0 5.0 6.0 Slope, % 1.25 2.0 1.5 1.25 5.0 4.0 3.0 Source: MWPS (1985). To storage or treatment Reception pit Gated flush tank FIGURE 12.4 Dairy ush alley. (Source: NRCS/USDA, 1992, p. 10-6.) 7098.indb 402 4/25/07 5:32:30 PM © 2007 by Taylor & Francis Group, LLC CAFO Component Design 403 To treatment or storage Pen partition Flush tank Flush alley Reception pit FIGURE 12.5 Swine ush alley. (Source: NRCS/USDA, 1992, p. 10-6.) Manually activiated gate opening mechanism Concrete or steel tank Gate is tire mounted on solid rim Hole Tank Bell Intrusion Trap Tank 3" Downpipe Tipping tank Gal/ft of tank length Tank dimensions in. X 18 18 18 Y 36 33 30 L 30 24 20 C 15 1/2 12 1/2 10 1/2 D 14 1/2 13 12 40 30 24 L Y 2"x2"x1/8" Angle X D C 1 3/4" Shaft 2"x2"x1/4" Angle bracing around top Slatted floor 8" min. Flushed floor Sandfill Tank with circular flush gate Automatic siphon tank 16 Gauge steel metal FIGURE 12.6 Flush tanks. (Source: NRCS/USDA, 1992, p. 10-7.) 7098.indb 403 4/25/07 5:32:32 PM © 2007 by Taylor & Francis Group, LLC 404 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Another kind of ush tank uses the principle of a siphon. In this tank, the water level increases to a given point where the head pressure of the liquid overcomes the pressure of the air trapped in the siphon mechanism. At this point, the tank rapidly empties, causing the desired ushing effect. Most ush systems use pumps to recharge the ush tanks or to supply the necessary ow if the pump ush technique is used. Centrifugal pumps typically are used. The pumps should be designed for the work that they will be doing. Low volume pumps (10 to 150 gpm) may be used for ush tanks, but high volume pumps (200 to 1,000 gpm) are needed for alley ushing. Pumps should be the proper size to produce the desired ow rate. Flush systems may rely on recycled lagoon water for the ushing liquid. In some parts of the country where wastewater is recycled from lagoons for ush water, salt crystals (struvite) may form inside pipes and pumps and cause decreased ow. Use of plastic pipes and ttings and pumps that have plastic impellers can reduce the frequency between cleaning or replacing pipes and pumps. If struvite formation is anticipated, recycle systems should be designed for periodic cleanout of pumps and pipes. A mild acid, such as dilute hydrochloric acid (1 part 20 mole hydrochloric acid to 12 parts water), can be used. A separate pipe may be needed to accom - plish acid recycling. The acid solution should be circulated throughout the pumping system until normal ow rates are restored. The acid solution should then be removed. Caution! Spent acid solution must be disposed in accordance with applicable environmental and safety regulations. 12.3.2 guTTerS Gutters are narrow trenches used to collect animal waste. They are often employed in conned stall or stanchion dairy barns and in some swine facilities. 12.3.2.1 Gravity Drain Gutters Deep, narrow gutters can be used in swine nishing buildings (Figure 12.7). These gutters are at the lowest elevation of the pen. The animal trafc moves the waste to the gutter. The gutter lls and is periodically emptied. Gutters with Y, U, V, or rectangular cross-sectional shapes are used in farrow - ing and nursery swine facilities. These gutters can be gravity drained periodically. 12.3.2.2 Step-Dam Gutters Step-dam gutters (i.e., gravity gutters or gravity ow channels) provide a simple alternative for col - lecting dairy manure (Figure 12.8). A 6-in. high dam holds back a lubricating layer of manure in a level, at-bottomed channel. Manure drops through a oor grate or slats and ows down the gutter under its own weight. The gutter is about 30 in wide and steps down to a deeper cross channel below the dam. 12.3.2.3 Scrape Gutters Scrape gutters are frequently used in conned stall dairy barns. The gutters are 16 to 24 in. wide, 12 to 16 in. deep, and generally do not have any bottom slope. They are cleaned using either shuttle-stroke or chain and ight gutter cleaners (Figure 12.9 and Figure 12.10). Electric motor drive shuttle stroke gutter cleaners have paddles that pivot on a drive rod. The drive rod travels alternately forward for a short distance and then backward for the same distance. The paddles are designed to move manure forward on the forward stroke and to collapse on the drive rod on the return stroke. This action forces the manure down the gutter. Shuttle stroke gutters can only be used on straight gutters. Chain and ight scrapers are powered by electric motors and are used in continuous loops to service one or more rows of stalls. 7098.indb 404 4/25/07 5:32:32 PM © 2007 by Taylor & Francis Group, LLC CAFO Component Design 405 Slope gutter bottom Bottom slope max manure depth Pen floor Treated timber cover over pit, with hole for valve handle Optional emergency overflow (use only if outlet is gas trapped) Alley Step Pen length Alley Step Pen length Gutter Gutter Insulation (where needed) To storage FIGURE 12.7 Flush and gravity ow gutters for swine manure. (Source: NRCS/USDA, 1992, p. 10-8.) Grate 2 ft min. Overflow dam Surface slopes 1-3% Manure incline plus dam height (6 in. typical + 3 in. grates) Channel Dam Cow mat Liquid layer retained by dam Cross section AACross section along stalls A A 30 in. recommended FIGURE 12.8 Gravity gutter for dairy manure. (Source: NRCS/USDA, 1992, p. 10-9.) Chain Chain FIGURE 12.9 Shuttle-stroke gutter cleaner. (Source: NRCS/USDA, 1992, p. 10-9.) 7098.indb 405 4/25/07 5:32:34 PM © 2007 by Taylor & Francis Group, LLC 406 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) 12.3.2.4 Flush Gutters Narrow gutters can also be cleaned by ushing. Flush gutters are usually a minimum of 2 ft deep on the shallow end. The depth may be constant or increase as the length of the gutter increases. The bottom grade can vary from 0% to 5% depending on storage requirements and cleanout technique. Flushing tanks or high volume pumps may be used to clean ush gutters. 12.3.3 SlaTTeD floorS Waste materials are worked through the slats by the animal trafc into a storage tank or alley below. As shown in Figure 12.11, most slats are constructed of reinforced concrete; however, some are FIGURE 12.10 Chain and ight gutter cleaner. (Source: NRCS/USDA, 1992, p. 10-10.) Isometric section A A A A FIGURE 12.11 Concrete gang slats. (Source: NRCS/USDA, 1992, p. 10-10.) 7098.indb 406 4/25/07 5:32:35 PM © 2007 by Taylor & Francis Group, LLC [...]... Group, LLC 7098.indb 413 4/25/07 5:32:42 PM 414 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) are designed to include outside runoff from watersheds For these, the runoff volume of the 25-year, 24-hour storm must be included in the storage volume 12. 4.2.2 Design of Sidewalls and Floors The information on the design of sidewalls and floors discussed earlier on solid manure storage... 12. 18, and 12. 19 represent various kinds of storage ponds and tanks Liquid manure can be stored in aboveground (Figure 12. 18) or belowground (Figure 12. 19) tanks Liquid manure storage tanks can be constructed of metal, concrete, or wood Belowground tanks © 2007 by Taylor & Francis Group, LLC 7098.indb 411 4/25/07 5:32:40 PM 412 Environmental Management of Concentrated Animal Feeding Operations (CAFOs). .. 5:32:38 PM 410 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Freeboard (1.0 minimum) Depth of 25-year, 24-hour storm event on pond surface Depth of normal precipitation less evaporation on the pond surface accumulated during the storage period Volume of manure (TVM), clean water (CW) and wastewater accumulated (TWW) during the storage period Required volume Crest of spillway... Figure 12. 21 Anaerobic lagoon loading rate (Source: NRCS/USDA, 1992, p 1 0-2 9.) © 2007 by Taylor & Francis Group, LLC 200 400 7 120 87 600 Mi REVISED JUNE 1995, 1005008 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) 3 5 5 12 416 5 3.5 7098.indb 416 NATURAL RESOURCES CONSERVATION SERVICE U.S DEPARTMENT OF AGRICULTURE 417 CAFO Component Design MTV = TVM + TWW + CW (12. 10)... series of dry years, the lagoon should be partly drawn down and refilled to dilute excess concentrations of nutrients, minerals, and toxics © 2007 by Taylor & Francis Group, LLC 7098.indb 419 4/25/07 5:32:47 PM 420 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Freeboard (1.0 minimum) Depth of 25-year, 24-hour storm event on lagoon surface Max operating level Volume of manure,... in the design of storage facilities for solids include type, number and size of animals, number of days storage desired, and the amount of bedding that will be added to the manure Equation 12. 5 can be used to calculate the manure storage volume: VMD = AU × DVM × D (12. 5) where: VMD = Volume of manure production for animal type for storage, ft3 AU = Number of 1,000-pound animal units by animal type DVM... Equation 12. 11) WV = Waste volume for treatment period, ft3 (see Equation 12. 10) Table 12. 4 Sludge Accumulation Ratios Animal Type SAR Poultry Layers Pullets Swine Dairy cattle 0.0295 0.0455 0.0483 0.0729 Source: Adaptation from Barth (1985) © 2007 by Taylor & Francis Group, LLC 7098.indb 417 4/25/07 5:32:46 PM 418 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Table 12. 5... 7098.indb 407 4/25/07 5:32:35 PM 408 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Slope Slop Timber or concrete bucking wall e Runoff to storage Runoff to storage Barn cleaner to spreader or tractor stacking To storage and/or spreader from elevator stacker Figure 12. 12 Solid manure stacking facilities (Source: NRCS/USDA, 1992, p 1 0-1 2.) Engineered roof trusses Timber walls Stored... 5:32:52 PM 426 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Concave to collect moisture (if needed) Normal curvature 4' - 6' Adjust for size 6' 6' - 1 0' Figure 12. 29 Windrow schematic (Source: NRCS/USDA, 1992, p 1 0-4 2.) Advantages: • • • • • Rapid drying with elevated temperatures Drier product, resulting in easier product handling Ability to handle high volumes of material... 5:32:55 PM 432 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) Step 1 Begin Is the addition of a bulking agent necessary Step 2 No Step 3 Determine the percent moisture of the compost mix Determine the C:N ratio of the compost mix Yes Determine by field trial the amount of bulking agent to add Is the percent moisture between 40 and 60 percent No Determine the amount of amendment . Environmental Management of Concentrated Animal Feeding Operations (CAFOs) are designed to include outside runoff from watersheds. For these, the runoff volume of the 25-year, 24-hour storm must. by Taylor & Francis Group, LLC 412 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) can be loaded using slatted oors, push-off ramps, gravity pipes or gutters,. NRCS/USDA, 1992, p. 1 0-2 8.) 7098.indb 415 4/25/07 5:32:43 PM © 2007 by Taylor & Francis Group, LLC 416 Environmental Management of Concentrated Animal Feeding Operations (CAFOs) 120 33 120 87 25001 26083 CT DE FL U.S.