8 Waste Collection Treatment

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8. Waste Collection

& Treatment

Section Contents:

Purpose Housing Systems Manure Collection and Transfer Methods Treatment of Collected Manure Energy Utilization Indices (EUIs) Manure Storage Handling & Utilization of Stored Manure Energy Conservation Measures (ECMs) Glossary Web Page References

DISCLAIMER

Neither SCE nor any entity performing the work pursuant to SCEs authority make any warranty orrepresentation, expressed or implied, with regard to this guide, the merchantability or fitness for a particularpurpose of the results of the work, or any analyses, or conclusions contained in this guide. The resultsreflected in the guide are generally representative of operating conditions; however, the results in any othersituation may vary depending upon particular operating conditions. Photographs and diagrams providedwithin this guide by specific manufacturers are used for illustrative and educational purposes only and are notmeant to endorse or promote a specific product or manufacturer.

Purpose Waste Collection & Treatment

All dairy farms produce and then must dispose of waste products from two major sources;the wastewater from their milking centers and the waste products from digestion and otherbodily processes of dairy cows. A significant amount of energy is used on California dairyfarms for a variety of treatment processes and disposal of waste products.

Milking center wastewater is generated from the following sources:

1. Washing of milking equipment.2. Cow prep wash pens.3. Back flush of milking equipment4. Parlor and holding area flushing.

There are four major types of manure collection systems employed on dairy farms.

1. Flush systems utilizing water to dilute and transport manure2. Automatic alley scrapers3. Vacuum operated collection equipment4. Tractor or skid steer manure scraper

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The flush system is used on the majority of California dairies, with small numbers utilizingautomatic alley scrapers. Flush cleaning of dairy manure offers a labor efficient method forremoving wastes from large dairy operations. The advantages of labor saving, frequentcomplete cleaning, drier alleys and cleaner cows offset the disadvantages of large volumewater requirements and possible need to separate solids to provide recycling water.Energy used in flush systems centers on pumping. Pumps are used to supply additional

water for dilution, pumping recycled water from storage to elevated holding tanks, tip-tanks,or other flush storage facilities. High volume pumps can also be used in pump-flushsystems to deliver flushing water directly.

Design parameters that must be addressed to achieve adequate flush system performanceinclude water volume per flush, flow rate, sufficient alley slope, length of flush period andinterval between flushes, water velocity and depth

Gravity flow channels are usually employed to move flushed wastes to storagelagoons/ponds. Individual site limitations may require additional pumping to storage.

Additional energy inputs can be required for the separation process to provide recycledwater for reuse in the next flush cycle. Finally electrically operated irrigation pumps may beused to land apply the liquid portion of separated waste.

Return to top of section: Waste Collection & Treatment

Housing Systems

Manure handling systems on dairy farms are normally designed around the type of housingsystem(s) on the farm. The housing system determines the type of manure produced(solid, semi-solid or liquid). The type of manure then dictates the appropriate handling

system.

Type of Housing

Tiestall or stanchion barn

Tiestall or stanchion barns are typically used on smaller dairy farms (100 cows or less).Cows are secured in resting stalls where they are also fed and milked. Straw, sawdust orpaper sludge bedding is used on the cow platform to enhance cow comfort. Manure iscollected in gutters, usually with significant amounts of bedding (chopped straw, sawdust,etc.) adding to the solids content. Manure is often collected and spread daily during spring,

summer and fall months, but may be stored during the winter months. Handling equipmentconsists of a gutter cleaner, manure spreader and a loader to transfer manure from a short-term storage to the spreader. Manure may be moved to the storage by a gutter cleanerextension, an elevator, a solid piston pump, or a tractor/bucket loader system.

Some tiestall barns are built with a gravity gutter system. The gutters are sloped towardone end of the barn and manure urine and added water will flow by gravity to a collectionpit at the end of the barn. The manure can then be pumped from the collection pit to a

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spreader or to a long term storage facility. The primary energy use in such systems is forthe periodic pumping of the collection pit. Figure 8-1 shows a tiestall barn with bedding.

Figure 8-1. Tiestall barn with bedding

Bedded pack (loose) housing systems

Loose housing systems had become less prevalent in recent years, but are gaining inpopularity in some areas. Cows are housed on a composting bedded pack in open floorplan resting barns. Fresh bedding is spread on the bedded pack every twoto six weeks. The bedded pack is tilled or stirred daily with a tractor mounted rotary tiller orcultivator to blend in oxygen to produce a compost process that breaks down organic

matter. Daily stirring generally takes just a few minutes. The resting area is cleaned outtotally once a year with a bucket loader and applied to fields with a manure spreader.These systems are best suited to smaller dairies (under 200 cows, and offer excellent laborand energy efficiency. Cow comfort and general herd health can be well managed with acomposting bedded pack system.

Corral with or without sunshade

Corral confinement systems are generally used in warm, dry climates. Dairy cows roamfreely within the confines of a large open area surrounded by fencing. Manure is collected

on the earthen surface of the corral where the sun dries it and cow traffic breaks it up.Often, the manure and surface soil will be mixed with a tractor pulled drag to facilitatedrying. The manure may be scraped periodically into piles for further drying and thenspread on the land. Sunshades, if used, may have an earthen floor or a concrete floor.The feeding area will almost always have a concrete surface. These concrete areas maybe cleaned by tractor scraper or by a flush system. Flushed manure will be transferred to asettling pond for some solids separation and then to a storage lagoon which will be pumpedout periodically by irrigation pumps and spread on cropland. Generally, about 40% of themanure produced by the dairy cows will be deposited on the open lot surface, while about

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60% will be deposited in the feeding area. Figure 8-3 shows a corral with sunshade and aflushed feed alley in lower left corner.

Figure 8-3. Corral with sunshade and flushed feed alley

Freestall barn

Freestall housing barns generally have three or more rows of individual cow stallsseparated by concrete alleyways. Cows use the freestalls for resting, but can move aroundthe facility at will. A feed alley located in the center of the barn or on one side allows the

cows free access to feed, which is usually provided as a total mix ration (TMR). Manurefrom a freestall barn is usually handled as a liquid unless excess bedding materials aremixed in to create a more solid consistency. In such cases, the manure is handled as asemi-solid and can be scraped into a storage that allows some solid/liquid separation. Thesolid portion can be transferred by bucket loader to a spreader, while the liquid portion canbe pumped. Manure in a freestall barn is removed from the structure by

scraping with a tractor scraper or skid steer or automatic alley scrapers or vacuum truck flushing.

Flushing systems add a considerable amount of water to the manure, further reducing thesolids content. Flushed manure is often transferred to settling basins, where more solidssettle out and then on to a long term storage. The manure is generally stored in earthenponds or above ground storage tanks. In the storage facility solids will separate and settle.The liquid portion can be pumped into tank spreaders or directly irrigated on the land. Thesolids are periodically removed by bucket loader and land spread. Figure 8-4 shows afreestall barn in Vermont and Figure 8-5 show freestall barn in California.

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Figure 8-4. A Vermont 4-row freestall barn with scraped alleys

Figure 8-5. 4-row freestall barn in California

There are also combined freestall and corral systems where the cows spend much of theirtime in the freestall barn (resting and feeding), but also have access to a corral. About 80%of the manure is deposited in the freestall barn for such systems. During inclementweather the cows may be confined to the freestall. The freestall barn may be flushed orscraped to transfer the manure to the storage system. A vacuum truck may also be used toremove the manure from the freestall barn. During winter months, the freestall facility willprovide primary shelter for the dairy cows.

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Manure from small freestall facilities is often scraped directly into a spreader and spreaddaily on the land, except in the winter months when spreading may not be possible. Duringthat time, the manure is transferred to a short-term storage for later spreading.

Other wastewater

Equipment wash water, cow wash or prep water and manure waste from milking centerwashdown add a significant volume to the manure stream from a dairy facility. Thehandling and disposal of this liquid manure/wash water combination requires significantenergy in addition to the energy used to handle manure from the cow resting/housingareas. In small, tiestall or small freestall systems, milkhouse wastes are generallytransferred to a separate storage, which is occasionally pumped out and spread on theland. Some small farms have a septic tank and leach field for milkhouse washwater waste.However, such systems often plug up because milk in the wastewater is difficult to breakdown. In larger systems, the milking center wash water is generally transferred to themanure storage on the farm.

This manure handling energy guide will assess the energy requirements of the numerousmanure handling systems that are used on dairy farms. The guide will also determine whatenergy efficiency improvements can be applied to the various handling systems.

Figure 8-6 shows a decision tree for the manure handling and treatment options to considerbased on the housing system used on the farm. The manure collection, treatment, storage,and utilization decision tree designate the many alternative paths that are available formanaging the flow of manure as produced to their ultimate methods of utilization. Torepresent the use of electric energy anywhere within the tree, an underline is used on thatentry. This indicates that some form of electric energy is being used accomplish that task.

The tree begins in the appropriate housing type with the available methods for collectionand transfer. From there a wide variety of initial treatment option can then be selected.These can be as simple as piling and drying of scraped corral/feedlot solids. To multiplestages of separation into liquid (L) and solid (Sd) fractions and anaerobic digestion incovered ponds (ADCP) for flushed wastes from freestall barns and feed lanes.

The treatment options produce a combination of materials Liquid (L) Solids (Sd) Sludge (Sl)

These materials can either be sent to medium or long term storage or undergo furthertreatment and processing before reaching their final end utilization. As an example solidsand sludge produced from any of the initial treatment processes can be dried and/orcomposted and used as an animal bedding material, marketed off the farm as acompost/soil amendment or be directly field applied.

Many options exist within the decision tree to highlight the complexity, interaction andthorough planning that must be employed when evaluating a waste collection andtreatment system.

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Stanchion BarnCorral/Feedlot

CorralSurface

FeedLanes

Housing

Collection

and Transfer

Treatment

Storage

Utilization

Freestall Barn

Alley Ways Gutters

ScrapeContinuous

Tractor

FlushFlush CleanerScrapeTractor

Piled &Dried

ProcessPit

SeparatorStatic

Bdg - BeddingFAS - Field Application (solids or semi-solid)

Dredge

Irr - Irrigation

FAS

Dried

Composted

AeratedPonds

Ponds

ConcretePad

Bdg IrrFAS FAS SaleBdgFASIrr

SeparatorScrew

WeepingWall

ADCP

AD

Sale

SettlingBasin

Excavator

L Sd

SlL

Sl

SlL

SlL

L Sd

(Liquid)L

(Solids)Sd

(Sludge)Sl

SlL

SeparatorStatic

L Sd

SeparatorStatic

L Sd SlL

Ponds

Irr

GrinderPump

AD

Sl

ADCP - Anaerobic Digester Covered PondAD - Anaerobic Digester

Underline = electric energy use

Figure 8-6. Manure collection, handling, and treatment decision tree


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Manure Production

The manure produced by a lactating dairy cow, wet weight and dry matter (total solids) is afunction of the milk produced and the dry matter intake. The relationship with milkproduction is not as good as with dry matter intake but milk production may be easier to

determine and is probably accurate enough for this purpose. For dry cows and heifers, themanure production is related to body weight. These relationships were developed byASABE [American Society of Agricultural and Biological Engineers], ASAE StandardD384.1, Manure Production and Characteristics.

A calculator to determine the manure (wet weight, total solids and percent total solids)produced by lactating cows, dry cows and young stock is attached. [for Web Site] Theamount of manure to be treated at a dairy farm must be determined in order to estimate theenergy needed. This will depend on the number of animals, their productivity and weight,and the type of housing. 1) For lactating cows, the RHA (rolling herd average) in terms ofpounds of milk produced per year is needed along with the number of animals. 2) For dry

cows and young stock the number and average body weight for each group is needed.

For following tables and graph presents the calculated manure production for lactatingcows (Table 8-1 and Figure 8-7), dry cows (Table 8-2) and young stock (Table 8-3) usingthe ASABE equations.

Table 8-1.Calculated manure production for lactating cows

lb/cow-day Gal/cow-day* lb/cow-day Moisture lb/cow-day Gal/cow-day* lb/cow-day MoistureRHA** Wet Weight Total Solids Content, % RHA** Wet Weight Total Solids Content, %16,000 123.1 14.7 15.4 12.47 25,600 140.1 16.7 17.9 12.7616,600 124.2 14.8 15.5 12.49 26,200 141.1 16.8 18.0 12.7717,200 125.2 14.9 15.7 12.51 26,800 142.2 16.9 18.2 12.7917,800 126.3 15.0 15.8 12.53 27,400 143.3 17.1 18.3 12.8018,400 127.4 15.2 16.0 12.55 28,000 144.3 17.2 18.5 12.8219,000 128.4 15.3 16.1 12.57 28,600 145.4 17.3 18.7 12.8319,600 129.5 15.4 16.3 12.59 29,200 146.4 17.4 18.8 12.8520,200 130.5 15.5 16.5 12.60 29,800 147.5 17.6 19.0 12.8620,800 131.6 15.7 16.6 12.62 30,400 148.6 17.7 19.1 12.8821,400 132.7 15.8 16.8 12.64 31,000 149.6 17.8 19.3 12.8922,000 133.7 15.9 16.9 12.66 31,600 150.7 17.9 19.4 12.9022,600 134.8 16.0 17.1 12.68 32,200 151.7 18.1 19.6 12.9223,200 135.8 16.2 17.2 12.6923,800 136.9 16.3 17.4 12.71 * Assumes density of manure at 8.4 lb/gal24,400 138.0 16.4 17.6 12.72 ** Rolling Herd Average, lb milk/yr25,000 139.0 16.6 17.7 12.74 Source: ASAE Standard D384.1

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Manure Production, Lactating Dairy Cow

120124128132136

140144148152156

16,000

17,000

18,000

19,000

20,000

21,000

22,000

23,000

24,000

25,000

26,000

27,000

28,000

29,000

30,000

31,000

32,000

33,000

34,000

RHA, lb of Milk/yr

WetWeight,lb/cow-day

From ASAE Standard D384.1

Figure 8-7. Manure production, lactating dairy cow

Table 8-2. Calculated manure production for dry cows

Avg Body Wt lb/cow-day Gal/cow-day* lb/cow-day Moisturelbs Wet Weight Total Solids Content, %

1,200 74.4 8.85 8.88 11.91,250 75.5 8.98 9.08 12.01,300 76.6 9.11 9.28 12.11,350 77.7 9.24 9.48 12.21,400 78.8 9.38 9.68 12.31,450 79.8 9.51 9.88 12.41,500 80.9 9.64 10.08 12.51,550 82.0 9.77 10.28 12.51,600 83.1 9.90 10.48 12.6

* Assumes the density of manure at 8.4 lb/galSource: ASAE Standard D384.1

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Table 8-3. Calculated manure production for young stock

Manure Production, Young StockAvg Body Wt lb/cow-day Gal/cow-day* lb/cow-day**

lbs Wet Weight Total Solids500 48.2 5.73 6.26550 49.1 5.84 6.38600 50.0 5.95 6.49

650 50.9 6.05 6.61700 51.8 6.16 6.73750 52.7 6.27 6.84

800 53.5 6.37 6.96850 54.4 6.48 7.08900 55.3 6.59 7.19950 56.2 6.70 7.31

1,000 57.1 6.80 7.43

* Assumes the density of manure at 8.4 lb/gal** Assumes moisture content at 87 percentSource: ASAE Standard D384.1

The type of housing determines whether the manure will be handled and treated as a liquidor a solid and the amount of manure in each. Table 8-4 lists an estimated percent of thetotal manure solids that will be handled as a liquid and as a solid for four different housingsystems using the flush or mechanical handling system.

Table 8-4. Estimated percentages of manure handling

Percent of Total Solids

Handling System Flush Mechanical/ScrapedHousing System Liquid Solid Semi-SolidCorral with feed lanes 60 40Freestall & Corrals 80 20Freestall 100 100Stanchion or Tiestall 100 100

For example, a corral with feed lanes, 60 percent of the manure would be collected by theflush system and 40 percent would be deposited in the corral. The dry solids scraped froma corral are differentiated from the semi-solid manure coming from a tiestall barn where

bedding is used.

The difference between solid and semi-solid is related to the inches of slump when usingthe slump test used in characterizing the stiffness of concrete. A metal form is shaped asa frustum of a cone. The form is 12-inch high with a base diameter of 8 in, a top diameterof 4 in. Work by Sobel and Ludington established the following guide; solid slump 0 to 2in, semi-solid slump 5 to 9 in. A semi-liquid would have a slump greater than 9 inches.


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Manure Collection and Transfer Methods

The method of collecting manure from the dairy barn or resting area is dictated by the typeof housing system. There are four basic manure collection systems used on dairy farms:

Gutter cleaners

Gutter cleaners are the most common manure collection and transfer method for stanchionor tie stall dairy barns. Cow manure and urine are deposited into a gutter directly behindthe stall. The manure is then collected and transferred out of the gutter by a mechanicalgutter cleaning system. Most gutter cleaner systems are the chain and paddle variety. Thegutters are connected at either end of the barn by a cross gutter, which provides acomplete loop for the chain and paddle system to travel around the barn gutter and up thedischarge chute. The discharge chute may empty directly into a manure spreader or it maybe extended to empty onto a manure storage pad. The chain drive unit is generallypowered by a 3 to 5 HP electric motor.

A second type of gutter cleaner is the shuttle-stroke system. These systems include adrive unit attached to a rod that runs the length of the gutter. Attached to the rod at regularintervals are hinged paddles. The drive unit forces the rod and paddles forward, with thepaddles open across the width of the gutter. The paddle position causes the paddles topush the manure the length of the drive unit forward stroke (usually 2 3 feet). At the endof the forward stroke, the drive unit reverses the rod and paddle direction, causing thepaddles to fold against the rod. At the end of the reverse travel, the drive moves the rodand paddles forward again, causing the paddles to open and push another section ofmanure forward. The process continues until the gutter contents are moved out of the barnto a spreader or storage.

Typically, gutter cleaner systems operate less than one hour per day.

Tractor or skid steer ally scraping

Freestall barns have multiple alleyways on which manure and urine is deposited by cowsroaming freely. Many smaller freestall barns are cleaned using a small tractor with a frontor rear mounted blade. See Figure 8-8. The manure is pushed to a loading ramp anddirectly into a spreader or into a cross gutter or reception pit from which it can flow bygravity or be pumped to storage. Skid steer loaders with specially designed scraper bladesare often preferred for this work because of their exceptional maneuverability. Cows must

be partitioned out of the section of the freestall barn being cleaned. Tractor or skid steerscraping systems can be quite labor intensive, and are not practical in very large freestallfacilities.

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Figure 8-8. Small tractor with rear-mounted blade

Electric-powered alley scrapers

Electric powered automatic alley scrapers are very common in large freestall barn systems.A cable drive system pulls a hinged paddle the length of the freestall alley. Upon reachingthe end of the freestall alley, the system reverses and pulls the paddle back to the oppositeend. See Figure 8-9.The hinged paddle opens to the full width of the alley in the forwardmotion and pushes the manure/urine mix to a collection pit or gutter at the end of thefreestall barn or in the middle of very long barns. When the motion is reversed, the paddlecloses while it travels back to the opposite end. Alley scraper systems are very energyefficient, with drive units seldom having an electric motor larger than 3 HP. The alleyscrapers can be set up to operate continuously or several times per day, depending onconditions. In cold climates, during severely cold weather, continuous operation helpsavoid manure freezing on the floor. The alley scrapers travel very slowly and do not disturbcows loitering in the alley. An advantage of electric alley scrapers is that cows do not haveto be partitioned out of the area being cleaned. They are excellent labor saving devices.

Figure 8-9. Alley scraper in a freestall alley with wings open

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When manure is deposited into the collection pit or gutter, it may be transferred by gravityor pump to a larger storage facility.

Vacuum manure collection

Vacuum tankers (sometimes referred to as honey vac) collect manure as excreted fromanimal confinement areas using a powerful vacuum force that transports manure from analley scraper mounted on the front of the truck to a tank, where manure can then betransported to processing, storage or off the farm for direct land application. Tractor towedunits are also available. One model of vacuum tanker is shown in Figure 8-10.

Vacuum collection of manure in the barn or corral offers the following benefits; Eliminate the need for flushing and requirements for large volumes of flush water Adaptable to barns with different size alley configurations Can improve air quality by eliminating release of volatile compounds from flush

water

Can handle high solid content material Provide a higher total solid content material that can be transported more

economically to a central digester or other value added processor. Vacuum collection users report less odor, flies, lower water use and cleaner

cowsPotential drawbacks include:

High capital and operating cost Relatively slow labor intensive process versus flush systems

Figure 8-10. Vacuum collection tanker truck

Flush Systems

Manure flush systems are very prevalent on large farms in warmer climates. Flushsystems use large quantities of water to dilute and flush manure from alleyways in dairy

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resting and feeding facilities. Flushed barns are built with sloped floors that facilitate themovement of flush water the length of the alleys. There are two types of flush systems.

Head pressure systems, gravity, reservoir flush

These systems consist of above ground water storage tanks for dilution/flush water andflush valves to direct the water flow where it is needed. Figure 8-11 shows a head pressuresystem. Head pressure systems use less water, but require higher pressures to movemanure out of the alleyways. The high rate of flow of the flush water creates a wave actionthat moves manure rapidly. Alley slopes from 1% to 6% are acceptable. The water supplyfor the flush tanks may include milking center wash water as well as water recycled fromstorage ponds. Flush volumes for head pressure systems range from 3500 to 6000 gpm indurations of 20 to 60 seconds.

Head pressure systems use less energy because the storage tanks can be refilled slowlyby low horsepower pumps. Gravity provides the pressure for the flushing process.

Figure 8-11. Head pressure system

Erosion flush systems

These systems use low pressure water pumps and flush valves combined with alley slopesof 1% or less to erode manure out of the alleyways. Large, 30 50 HP irrigation pumpsare used to achieve water flow rates of 2000 gpm. A typical flush may last 5 to 10 minutes.The flush water is generally recycled from manure storage ponds after solids have settledout. Erosion systems produce a higher energy demand because large horsepower pumpsmust be used to rapidly pump large quantities of water to provide adequate cleaning of thealley surfaces. Figure 8-12 shows a flush pump in a storage pond for an erosion flushsystem. Figure 8-13 shows the flush water entering an alleyway through a flush valve. A

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Figure 8-12. Flush pump for an erosion flush system

flush valve is shown in Figure 8-14. Flush systems are generally operated up to four times

daily to ensure proper cleaning of alleyways. The flushed manure generally flows bygravity to a reception pond or processing pit from which it can be pumped for furthertreatment. Flush water can also be pumped directly from the process pit which reduces theamount of fresh water needed and provides a higher solid content in the wastewatershould a separator be used. Flush systems require from 60 to 125 gallons of water percow per day. If fresh water was used for flushing, consideration must be made for muchlarger manure storage to contain the extra water.

Figure 8-13. Flush in progress

Flush systems are easily automated, provide cleaner alley floors which dry faster, and areusually less labor intensive than other collection methods. Flush systems are mostadvantageous when used in large facilities with large cow numbers.

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Proper alley slope and flush system design are critical factors. The pumps, piping andflush valve systems can be complicated and expensive.

Figure 8-14. Automatic flush valve

Process pits are often used to receive the flush water from the alleyways.Sometimes the flush water is re-circulated back through the alleyways from this pit beforethe wastewater is pumped to the separator. Two different processing pit designs areshown in Figures 8-15 and 8-16.

Figure 8-15. Concrete processing pit with sand chamber at right

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Figure 8-16. Earthen processing pit


Treatment of Manure Collections

Separators

Liquid / Solid Separation Options

The separation of dairy manure into liquid and solid fractions can be achieved by manydifferent methods and allows further treatment options for each component. Some of thebeneficial advantages that can be attained with liquid/solid separation are:

Reduce the amount of solids accumulation in liquid storage faculties to expandcapacity and extend life.

Reduce solids in stored liquids to enable land application through use of irrigationsystem to deliver liquids to field in place of specialized manure pumping andhandling equipment (tankers, spreaders, etc.)

Reduce solids in stored liquids to allow recycling of separated liquids for use asflush water for freestall cleaning. Reduction in amount of fresh water needed forthis task

Separated solids can be stored which offers many options for utilization (i.e. saleas value-added product to market off the farm, fertilizer, compost, bedding,transport nutrients off farm)

Remove solids from liquids to allow further treatment processes to be applied oneach waste stream

Reduce pumping horsepower needed to move liquid waste or allow increase inpumping distances

Reduction in run-off from stacked solids

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Partitioning of nutrients in liquid and solid streams to allow superior disposal

options Improve or protect air quality Improve or protect water quality

Separation technologies currently available are divided into passive, gravity systems such

as settling basins, or active, mechanical systems or presses that use energy to split wasteinto liquid and solid components. The amount of total solids that can be captured by thesesystems varies widely and is presented in Table 8-5 below.

Table 8-5. Percent capture of total solids

Solid / Liquid Separator Technology Total SolidsCapture Efficiency

Static Inclined Screen 10-20%Inclined Screen with Drag Chain 10-30%Vibratory Screen 15-30%

Rotating Screen (Drum) 20-40%Centrifuge 20-45%Screw Press 30-50%Settling Basin 40-65%Weeping Wall 50-85%Scrape and Dry 50-90%

*NRCS Code 632, Solid/Liquid Waste Separation Facility

Active mechanical systems require greater amounts of energy to increase captureefficiency, while gravity based systems need longer retention time and greater physical size(greater footprint) to increase their total solid capture efficiency. Greater amount of solids

captured, with less moisture content will require larger amounts of energy to be consumedby the mechanical separation system. The pie chart in Figure 8-17 shows the disposition oftotal solids in a flushing system on a California dairy farm. This farm did not have a

Separator*

28%

Settling

Basin*40%

Ponds*

10%

Remaining*

22%

*based on a study at a California dairy

Figure 8-17. Removal of total solids

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processing pit. Sixty eight percent of the total solids were removed by the separator and asettling basin or pond. Only 10% were removed in two treatment ponds and 22%, mostlydissolved solids, remained in the water in the storage pond.

Gravity Separation Options

Settling Basin

Settling basins, ponds or tanks, reduce the velocity of waste material and allow solidsentrained time to settle by gravity. A wide array of designs has been used, constructed ofearth, concrete or steel tanks. One current design, see Figure 8-18, employs settlingbasins installed in pairs. This allows one basin to function as the active receptor of waste,while removal of settled solids takes place from the second basin. Some characteristicsexhibited by settling basins include:

Use of common earthen or concrete construction material Separation achieved by natural force (gravity) no energy added. Unless

elevations on farm require additional pumping to settling basin

First stage separation, removes large amount of solid Large footprint on the farm can impact siting. Additional land required and

appropriate slopes to make settling basin work Requires additional labor and equipment costs (operator and loader) for

scheduled cleanings Can be adapted to existing systems

Figure 8-18. Dual concrete settling basins

Weeping Wall

The weeping wall is an adaptation of long-term manure storage. They can be applied inconjunction with other technologies or stand-alone. Systems consists of a medium to longterm manure storage with a continuous screened area positioned along one wall that

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permits the liquid portion to pass through and retains the solid components. Separatedliquids are collected through a drainage system and transported to long-term storage.Separation takes places through the weeping wall due to the hydrostatic pressures exertedby the depth of the manure in the structure. See Figure 8-19. Considerations of weepingwall systems:

Passive system, no additional energy required to make work High capital costs than conventional storage Large footprint on the farm can impact siting Requires secondary separated liquid collection system and storage Requires scheduled mechanical cleaning (loader) Concerns with plugging of filter material and discharge of material if filter material

fails Maintenance of filter media and useful life. Little control of moisture content of separated solid. Wide variation in consistency

of separated solids within structure can present unloading problems and limitoptions for end use.

Figure 8-19. Weeping wall at California dairy

Settling Ponds

Settling Ponds are designed to reduce the incoming velocity of the waste stream and allowentrapped solids to settle out. The liquid portion may then be pumped off for furtherseparation or into storage. The settled solids will be mechanically removed from thebottom of the pond periodically.

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Evaporation Ponds

Evaporation ponds are designed to remove water from waste stream through evaporationby solar and environmental conditions, leaving dried separated solids for disposal. They aresuited to arid and semi-arid regions where much more water is removed by evaporationthan is added by precipitation. Figure 8-20 shows a pond that had been drained and the

Figure 8-20. Dried solids in bottom of a pond

the solids allowed to dry. Their use is limited by climatic conditions, large size and designrequirements.

Mechanical Separation Options

Static or Sloped screen (Sidehill screens)

Static screens work well with manure slurries of 4% total solids or less, making them well-adapted to dairies with flush manure handling. They have simple operating principal andrelatively low energy inputs. Principal energy use by a screen is from pumping combinedwaste to the top of the screen, removal of liquid at the bottom to storage and removal ofsolids from the bottom of the screen. Cyclical rinsing, vibration or brushing can aid solidsremoval and increase energy use. Screens utilize few moving parts and have very low

maintenance requirements. See Figures 8-21 and 8-22.

Static screens employ a sloped screen with weir box at top to control flow of manurethrough unit. Manure is pumped into the weir box at the top of the unit and gravity flowsdown the screen. The liquid component and smaller solids go through the screen and thesolids fall off at the bottom of the screen.

Screens are generally constructed from stainless steel and can be configured in a variety ofdesigns and slot opening sizes. Typical configurations include single screens, dual screens

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placed over each other to achieve greater degree of separation and screens placed inseries. The shape and size of openings in the screen determines the size of particlesseparated. Openings in the screens range from approximately 0.010 to 0.060. Manuremust be relatively dilute to flow and pass through and across screen openings.

Reclaimed solids may fall off directly into a pile for storage, or transported by a stacker into

a pile for storage. The bottom surface of the stacker frame may also perforated allowing forfurther dewatering of solids as they travel to final disposition in a stack.

Solids come off as wet sludge. Moisture content of 75 80 % is typical for solids that comeoff the screen(s). Solids may too wet to compost directly after separation. Depending onthe climate, additional sources of dry matter may be required to compost. A wash-downsystem may be needed to prevent solids from drying and plugging the screen(s) followinguse. Solids may be further processed with a roller or screw press.

Figure 8-21. Static screen separator, single

Figure 8-22. Twin static separator

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Drum screens

Drum screens utilize a rotating perforated metal drum with compression rollers to separateliquid and solid components of manure. Manure slurries of up to 10% total solids can beprocessed in a drum screen, offering another separation option to dairies that do not useflush systems. See Figure 8-23.

Manure slurry is pumped up into a flow control weir box, where it is metered out onto theperforated surface of a rotating drum. Adjustable compression rollers on the drum force theliquid portion thru the openings in the rotating drum. A collection system inside the drumaccumulates the separated liquid and transports to storage. The separated solids arescraped from the drum surface and can be gravity or mechanically stacked.

Drum screens can produce drier solids than a static screen, but not as dry as a screwpress. Throughput capacities are generally lower than the static screen, but greater than ascrew or centrifugal press. Drum screens in general have low power needs. Energy isused to pump manure up to unit and produce rotational force on drum.

Maintenance can be frequent to service moving parts (drum, rollers, compressionmechanisms). Screens can be damaged by large trapped solid material.

Figure 8-23. Drum screen

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Inclined Screen with Drag chain conveyor

Single or double pass, the lower end is submerged in a manure pit; solids are dragged upover perforated or wedge wire screens. Solids may then be piled or they may fall into small

roller or screw squeezer for further liquid removal. Many moving parts, leakage and largesize may be objectionable. However, the system can produce drier solids than staticscreen. See Figure 8-24.

Figure 8-24. Inclined screen with drag chainconveyor

Roller and/or belt presses

Utilize a rotating roller or belt arrangement to remove liquid portion. A belt press employstwo concentric running belts that are used to squeeze the manure as it is depositedbetween the belts. The belts pass over a series of spring-loaded rollers where liquids aresqueezed out or through the belt and remaining solids are scraped off at a belt separationpoint. See Figure 8-25.

Belt presses are fairly complex and have many more moving parts than a screw press.Maintenance requirements and energy costs can be high. May be used as secondarytreatment after static screen or other form of separation. Dry matter content of solids mayrange from 11-28 %, with belt presses producing driest solids.

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Sludgepolymermixer

Chemicalconditioning Gravity

drainage

Shear &compressiondewatering

Sludge

Polymersolution

Conditionedsludge Wash spray

Stage 1 Stage 2 Stage 3

Wash spray

Wash water

Dewateredsludge cake

Filtrate

Figure 8-25. Belt-filter presses for separating animal manure

Screw press

The screw press uses a screw of progressively reducing pitch rotating inside a cylindrical,perforated screen to gradually separate liquid and solids. Screw presses contain fewmoving parts. They provide another method of separation for facilities that rely on scrapecleaning or can further process the solids form a static screen to remove additional liquid.Screw presses can process manure with a higher percentage of solids (up to 15%) thanstatic screens. Energy inputs are fairly high to produce drier end product.

Manure entering the screw press is gradually subjected to increasing pressure as it moves

toward the exit end of the press, forcing the liquid portion of the manure slurry through thescreen. Liquids are collected from the perforated screen and pumped or gravity flow tostorage. See Figure 8-26.

Solids are forced out the end of the separator housing by rotating action of the screw. Thescrew turns at a fairly low speed (10-30 rpm). Regulation of solids moisture content iscontrolled by adjustment of a discharge door at the end of the screw. A graduated screwpitch and interrupted flight screw prevent jamming of material within the screw press.

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Figure 8-26. Typical screw press separators

Centrifugal press

These units use centrifugal to separate solids from liquids. Centrifugal presses can offer thedriest solid production; however they also have high energy and operating costs.Centrifugal presses can also serve as second stage of separation after initial processingwith another separator to remove additional solids from liquid portion.

The centrifugal press is comprised of a motor, a tapered hollow cylinder with a rotor inside,the inlet and outlet. The rotor turns at a high speed compared to a screw press. Centrifugalforce spins the solids, such as sand and minerals to the outside of the water column. Therethe solids drop to the bottom of the machine and exit. The remaining liquid is sent tostorage. See Figure 8-27.

Figure 8-27. Centrifugal press separators

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Aerated Ponds

Aeration of ponds holding dairy manure is becoming more common. The impact of aerationmay be four fold; reduction in the emission of volatile organic compounds (VOCs) andodorous compounds, and a reduction in 5-day BOD and the concentration of total solids.The level of aeration required to achieve each of the above benefits is unknown plus the

level of control needed for the emission of VOC, for instance, is also unknown.

The spectrum from anaerobic to aerobic conditions is wide. An aerobic environment is saidto exist when the level of dissolved oxygen is equal to or exceeds 2 mg per liter [2 mgDO/l]. This insures adequate oxygen for all aerobic bacteria. To achieve this level ofdissolved oxygen in a manure pond would require a very large input of energy and a dilutesolution of the dairy manure.

The range from a 2 mg DO/l state to a fully anaerobic state can be monitored in terms ofoxidation-reduction potential (ORP) as measured with a platinum electrode. In a completeanaerobic condition, deprived of O2 (anoxic), the ORP could be 400 mV, a biological

reduction state. With aerobic conditions, the ORP would be positive, a biological oxidationstate. The relationship between ORP and the production and release of VOC, for instance,has yet to be determined. An ORP of 300 mV in poultry manure produced by a low levelof aeration will inhibit the production of hydrogen sulfide.

At present there are several types of aerators. These include impeller (see Figure 8-28),micro-bubble (see Figure 8-29) and venturi (see Figure 8-30). The impeller type floats onsupporting pontoons with a vertical shaft from the motor to the impeller. There are variousimpeller designs and positions with respect to the surface. These factors determine thedepth of mixing and oxygen transfer. The micro-bubble aerators use a patented design toform small bubbles that remain in suspension longer to permit greater oxygen transfer. Theventuri design pumps waste water through a venturi drawing air into the water that is thendischarged back into the pond. The foam shown in Figures 8-28 and 8-29 is evidence ofbubbles rising to the surface. Very few aerators have been tested to determine the oxygentransfer rate (OTR) in terms of lb O2/hr. There is also the need to know the relationshipbetween OTR measured with clean water in a standard test and real OTR in dairywastewater ponds. The efficiency of aerators given in terms of lbs of oxygen transfer perkWh is also an issue. Without real OTR and efficiency, preparing an engineering design fora system is impossible. In the mean time, dairy farmers will buy and install aerators withoutknowing the facts.

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Figure 8-28. Impeller type aerators

Figure 8-29. Micro-bubble aerator

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Figure 8-30. Venturi type aerators

There is a need to determine the minimum aeration needed to achieve the objectives forwaste treatment or storage. What is the relationship between ORP and the release ofVOCs, between BOD5 or COD reduction and VOCs?

Anaerobic Digesters

Anaerobic digestion is a process recognized for centuries as a way to break down manureand other organic materials, while reducing the odor of those materials in storage. There isevidence that biogas from the breakdown of organic substances was used to heat bathwater in Assyria in the 10th century BC. The first anaerobic digester plant was built in Indiain 1859. The technology is advancing rapidly as anaerobic digestion and the resultantproduction of biogas is recognized as an alternative fuel source. Many dairy farms aroundthe nation are now using or considering the use of anaerobic digesters as a manuretreatment option. There are energy use and energy production implications involved in anyanaerobic digestion system on a dairy farm.

Anaerobic digesters have a two directional energy component. Most anaerobic digesters

require energy input in the form of pumping material to the digester. Heat energy is oftenrequired to maintain a desirable temperature within the digester to continue the bacterialaction that causes the organic material to break down. On the other hand, the digester alsoproduces energy in the form of methane gas (biogas). This gas can be used for thermalenergy needs on the farm, such as water and space heating. The gas can also be used ina boiler to maintain digester temperatures of about 100 F. Another common use for thebiogas is to fuel an engine-generator set and produce electricity. Large scale digestersystems can often produce enough electricity to meet most or all the farm needs plus havesome excess to sell into the grid.

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Types of Digesters

There are four types of digesters typically used on dairy farms:

Covered manure storage ponds

There is continuous biological activity in manure storage ponds that breaks down theorganic matter contained in the pond. That biological activity produces measurablequantities of methane gas which is given off into the atmosphere. Covering the storagepond with a flexible cover enables the collection of the gas for use on the farm. Coveredponds work best in warm climates, since very cold weather will cause normal biologicalactivity to cease. The biogas trapped under the cover can be piped for use in a boiler or inan engine-generator. See Figures 8-34 and 8-35. Covered ponds represent the lowestcost anaerobic digester system, but they are also least efficient in overall biogasproduction. They are most commonly used on large farms with flush type manure handlingsystems. Covered storage pond type digesters cost an average of $65 to $90 per cow.

Figure 8-34. Covered storage pond in Wisconsin

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Figure 8-35. Partially-covered anaerobic digester pond in California

Plug-flow digesters

Plug flow digesters are typically rectangular shaped concrete boxes built in ground witheither a hard concrete top or a flexible top under which biogas collects as it is produced.The manure and other organic matter is introduced at one end of the digester. The manureflows through the digester for a period of days determined by the volume of the digester(usually about 15 20 days), during which time bacterial action breaks down the organicmatter and produces biogas. The biogas is collected under the cover and is piped to apoint of use. The cover of the digester can be either flexible, see Figure 8-36, or solid, seeFigure 8-37. Horizontal plug flow digesters will handle manure that has a higherconcentration of solids (up to 12% solids). Plug flow digesters can also be designed as

vertical tanks, see Figure 8-38, but solids concentration must be reduced and morepumping energy is required to move manure through the digester. Depending on size andcomplexity of moving material to and from the digester, plug flow digesters can cost from$200 to $1,000 per cow. Plug flow digesters for herds under 400 cows are not economical.

Figure 8-36. Plug flow digester with flexible cover, Princeton, MN

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Figure 8-37. Hard top plug flow digester in Whatcom County, Washington

Figure 8-38. Vertical plug flow digester

Complete mix digesters

Complete mix digesters are the most expensive systems, but can handle manure and otherorganic matter with a solids content anywhere from 3% to 10%. Complete mix digesterscan utilize horizontal, in ground concrete tanks or vertical concrete or steel tanks. SeeFigure 8-39. Bacteria within the digester breaks down the organic matter in the samemanner as in plug flow digesters. Retention time in complete mix digesters in generallyshorter than plug flow digesters. Complete mix digesters require more pumping of themanure slurry, thus there is more equipment and energy required to feed the digester.Generally, complete mix digesters produce more biogas per unit of organic matter treated.

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Complete mix digesters are the most expensive and can cost from $500 to $1,800 per cow.Complete mix digesters are also too expensive for smaller dairies.

Figure 8-39. Complete mix digester in Wisconsin

Fixed film digesters

Fixed film digesters are suitable for applications where manure odor control is the primaryreason for installing a digester and gas production is not a priority. The term fixed filmrefers to a material installed inside the digester vessel on which bacteria can attach

themselves. The material could be bundles of plastic drainage pipe or other material thatprovides a large surface area for bacteria. The vessel is then filled with manure and thebacteria begin to break down the organic matter. Because there is a very large surfacearea of bacteria, relative to the amount of manure in the vessel, breakdown occurs morerapidly than in other types of digesters. Thus, retention time in fixed film digesters can beas little as 2 7 days. Although gas production may be less than digesters with longerretention time, odor reduction is excellent. Fixed film digesters, because of the shortretention time, are much smaller than other types, and thus may be appropriate wherespace is a problem. Small, fixed film digesters may be most appropriate in smaller dairieswhere odor control is very important. Fixed film digesters generally cost less than plug flowdigesters because of the greatly reduced size of the vessel. Dairies from 100 cows and

larger can likely justify the cost of a fixed film digester. See Figure 8-40.

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Figure 8-40. Fixed-film vertical anaerobic digester for a 100 cow dairy in New York

Energy flows of anaerobic digesters

There are usually some increased input energy requirements for anaerobic digestersystems. In cool climates, heat energy must be added in the digester vessel to maintainproper operating temperatures. This is usually accomplished be circulating heated waterthrough pipes mounted inside the digester. The boiler producing the heated water may befueled by the biogas produced by the digester or by purchased fuels such as natural gas,propane, or fuel oil. Extra pumps may be required to transfer manure to and away from thedigester. In addition, complete mix digesters employ some type of electric powered mixingdevice such as a propeller type mixer or a circulator pump. These energy inputs arerelatively small compared to the overall energy requirement of handling manure, but must

be considered as plans for a digester are developed.

Generally, anaerobic digesters are a net energy producer. The energy represented in thebiogas produced by the digester exceeds the energy inputs required to operate thedigester. On large farms (400 cows and up), energy produced by the digester per cow peryear can be the equivalent of 72 gallons of propane or 48 gallons of fuel oil. Table 8-6below indicates estimated biogas production from a dairy anaerobic digester. Figure 8-41below shows an engine generator fueled with biogas.

Table 8-6. Estimated net biogas production and fuel equivalent from a dairy anaerobic

digester

Biogas Yield( ft/cow-

day))

Natural GasEquivalent

(Mcf)

PropaneEquivalent(gallons)

#2 Fuel OilEquivalent(gallons)

ElectricityEquivalent

(kWh)46 6.60 72 48 385

Based on: Barker, James C. 2001 Methane Fuel Gas from Livestock Wastes: A Summary. NorthCarolina University Cooperative Extension Service, Publication #EBAE 071-80.

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Figure 8-41. Electric generator fueled with biogas


Energy Utilization Indices (EUIs)

The electrical energy consumed in the collection and treatment of dairy manure can be

summarized in terms of EUIs (energy utilization indices). Table 8- presents the EUIs forthe tasks involved with flush collection at five California dairy farms studied. The energyused by the flush pump is given in terms of the energy used for each flush. The EUIs forthe flush pump are plotted on the graph in Figure 8-42. A trend line was drawn through the5 data points so that values for EUIs can be estimated for a given size dairy farm.

Table 8-7. Energy utilization indices for flush systems

Cows FlushPump*

PrimaryMixer(s)**

PrimarySeparatorPump**

SecondaryMixer &

Separator**

4,000 7.43,400 11.4 45.53,000 7.3 27.3 41.92,300 8.7 27.8 36.52,150 12 24.6 45.8800 18.5 26.7 53.3 95.4

* kWh/cow-yr-[flushes/day]** kWh/cow-yr

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0

2

4

6

8

1012

14

16

18

20

0 1,000 2,000 3,000 4,000 5,000

Lactating Cows

kWh/cow-yr

-flush

Figure 8-42. EUI for the flush pump

The line drawn at 2,500 lactating cows will be used in an example.

The primary mixer is locatedin the process pit and may run while the flushing andseparation pumps are operating. The average EUI for the primary mixer was 26.6kWh/cow-yr.

The separators are designated as primary and secondary when there are two separatorswith different screen openings. This does not apply where there is a double screen or

where there are two different size screen openings, upper and lower, in the same staticscreen. The EUI for the primary separator pump [the elevator motor is included] are plottedin Figure 8-43. A trend line was added to assist in estimating energy use. The EUI for thesecond screen is higher because the unit operates longer due to lower the flow (gpm) overthe screen.

25

30

35

40

45

50

55

0 500 1,000 1,500 2,000 2,500 3,000 3,500

Lactating Cows

kWh/cow-yr

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Figure 8-43. EUIs for primary separator pumpsThe following example will illustrate how to predict the annual energy use for a flush pumpand primary mixer and separator for a dairy farm with 2,500 lactating cows where the alleyswill be flushed 4 times per day.

Annual energy use = 2,500 [(10 x 4) + 26.6 + 41] = 269,000 kWh/yr

The EUI for mechanical alley scrapers operating continually averaged 24.7 kWh/cow-yr.The range for 17 dairy farms in NY was 10.2 to 77.2. There was not enough informationavailable to give an explanation for this wide range.


Manure Storage

The fundamental reason for manure storage is to allow land application to occur at a timethat is compatible with crop nutrient requirements and environmental conditions. Regulatoryconsiderations have also become an important issue affecting manure storagerequirements. Primary energy use is for loading and emptying the storage. Pumpingenergy supplied by electric motors or diesel engines is the most common energy source forthis purpose. Solid materials are generally handled by fossil fueled tractors or loaders.

The long-term manure storage system selected contributes to the total waste collection andtreatment system goals of:

Maintenance of animal health by means of providing sanitary facilities Prevention of air, soil and water pollution

Compliance with all federal, state, and local environmental regulations Recovery and use nutrients as part of proper nutrient management practices

Selection of appropriate long-term storage is influenced by the housing, collection, transfer,treatment and utilization components employed on the farm. Manure storage types arelinked to the moisture content of waste they hold (solid >16%, semi-solid 12-16%, slurry 5-12% or liquid


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Figure 8-44. Lined earthen storage on New York dairy

Figure 8-45. Unlined anaerobic manure pond on California Dairy

Other considerations influencing the type of manure storage selected are; Method and equipment need for delivery and application to the field. Need for nutrient conservation may impact the type of storage selected. Table 8-

8 represents nitrogen retention or loss in common systems Need for treatment for odor control or to accelerate solids breakdown Site specific space limitations

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Figure 8-46. Separated solids storage on California dairy

Table 8-8. Manure storage nitrogen retention and loss

System Nitrogen Lost, % Nitrogen Retained, %Daily scrap and haul 20-23 65-80

Manure pack 20-40 60-80Open lot 40-55 45-60Aboveground tank 10-30 70-90Holding pond 20-40 60-80Anaerobic lagoon 70-85 15-30

Adapted from MWPS-18, Livestock Waste Facilities Handbook 1993

Determining the appropriate size of a manure storage facility must take into account a largenumber of factors that will contribute to the final design and capacity. These can include;

Length of storage period desired or required by regulation Manure and bedding volume produced based on present and future animal

numbers Climatic Considerations Rainfall, evaporation, runoff, 25 year-24 hour storm

that require additional storage capacity Freeboard to ensure extra volume as a safety factor

Washwater and other waste waters (silo effluent) added. Sludge accumulation within the storage over time Energy and equipment requirements for filling and unloading storage Treatment options for odor control Allow incorporation for energy production or recovery thru anaerobic digestion

Sizing and construction must meet all federal, state and local codes and regulationsCurrent regulations require that a holding pond for long-term manure storage must be sizedto contain all wastewater and stormwater generated for approximately 120 days during the

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rainy season plus the stormwater from a 25-year 24-hour storm. The large size andcomplex regulatory requirements for manure storages, dictate that a qualifieddesigner/engineer be retained to ensure compliance all applicable codes.


Handling and Utilization of Stored Manure

Stored dairy manure is generally in one of four forms: Solid with considerable extra organic matter such as bedding material bringing the

solids content up to 16% or more. Semi-solid with a solid content of 12 16% Slurry with a solid content of 5 12% Liquid with a solids content of less than 5%

Handling of Stored Manure

On most farms, stored manure is handled either as a solid or a liquid, and this guide willdiscuss the process in those terms.

Solid manure, stored on a concrete pad, with or without containment walls, is usuallyhandled with tractor or skid steer bucket loaders. Sometimes the storage pad has a roof tokeep rainwater out of the pile. The manure is scooped up and loaded into a manurespreader for field application. Box, flail, or side discharge spreaders are usually used to

transport and spread the manure on the field. Care must be taken to avoid spilling manureon public roadways. The manure is removed from storage at convenient times of the yearwhen cropland is accessible (usually in the spring and fall). There are no electric operatedequipment components in these manure handling systems. Figure 8-47 illustrates typicalfield application of solid manure.

Figure 8-47. Box spreader used to spread solid manure on cropland

Liquid manure is usually stored in storage ponds, which may require a combination ofhandling systems when the pond is to be emptied. Manure storage ponds may be unlined,

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depending on soil permeability, or lined with clay or heavy plastic so that the liquid doesntleach into the soil and groundwater. The most common handling systems to remove storedmanure from ponds include:

Excavators to remove accumulated settled solids from the pond Dredge systems to chop and mix settled solids with the liquid portion so that

the resultant slurry can be pumped out

Irrigation pumps to pump manure with 5% solids or less directly to the field Tractor pulled or truck mounted tankers to transport and spread liquid manure

from ponds onto cropland

The process of emptying manure storage ponds is dependent on the total solids contentand the amount of sludge that has settled to the bottom. Since organic solids in the manuresettle to the bottom of the pond, forming a thick layer of sludge, the liquid faction on top canbe pumped to the field using an irrigation pump or pumped into a tank spreader andtransported to the field (Figure 8-48). When most of the liquid is removed, the sludge canbe handled with a long-reach excavator (Figure 8-49). The sludge can be loaded into a flailtype spreader to be applied on cropland.

Figure 8-48 , A tank type spreader used to spread manure slurry on cropland

Figure 8-49. A long reach excavator used to remove sludge from the bottom of a storagepond

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Sometimes, large floating dredges are used to empty manure ponds. The dredge floats onthe surface of the pond and uses a cutter type pump system to break up the solids in thepond and mix them with the liquid portion. The resultant liquefied mixture can then bepumped to cropland through a flood irrigation system. Floating dredges are often employedto empty storage ponds on large western dairies (Figure 8-50).

Figure 8-50. A Floating Dredge used to mix manure solids and liquids in a manure storagepond and pump the slurry to irrigate cropland

Manure ponds can also be emptied by irrigation pumps if the solids content is not too great(under 5% solids). The pond is usually agitated and mixed with a propeller type mixer or amixing pump. Then an irrigation pump can be used to transfer the mixture and spray it ontocropland. If the manure slurry is greater than 5% solids, very aggressive manure chopper

units are installed ahead of the pump to reduce solid particle sizes and to facilitate longdistance pumping. Irrigation pumps may be diesel engine driven or electric motor driven.Electric irrigation pumps range in size from 30 to 100 HP or larger.

On some dairies, the manure slurry in the storage pond is pumped into a larger over-the-road tanker and transported to remote cropland where a tractor driven drag hose irrigationsystem incorporates the slurry directly into the soil (Figure 8-51).

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Figure 8-51. A drag hose system used to incorporate manure slurry directly into soilAt other farms, the slurry may be pumped to a remote storage, centrally located nearcropland. The slurry is then irrigated from the remote storage or spread by tank spreadersat appropriate times. Often, tank spreaders are equipped with knife type injectors toincorporate the manure slurry into the soil. See Figure 8-52. This reduces nitrogen lossesto the air and also reduces offensive odors caused by spreading liquid manure on the soil

surface.

Figure 8-52. Liquid manure applied by tank spreader with direct soil injection

On smaller dairies, manure storage ponds are agitated and mixed and the resultant slurryis pumped into a tank type spreader which is used to transport and spread the manure ontocropland. Usually the pumps are tractor driven (Figure 8-53), but in some cases they can

be electrically driven (Figure 8-54).

Figure 8-53. Tractor PTO operated centrifugal manure agitator pump

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Figure 8-54. Floating electric propeller-type manure agitator

Utilization of Manure

Dairy manure is an excellent source of plant nutrients. Table 8-9 shows the averageamount of N, P and K in various types of stored manure. Dairy manure is almost alwaysspread, irrigated or otherwise incorporated into cropland soils to provide plant nutrients andto reduce purchased chemical fertilizer costs.

Table 8-9. Characteristics of various types of stored dairy manure

Type of StoredManure

Amount ofNitrogen per unit

Amount ofPhosphorus perunit

Amount ofPotassium perunit

Scrapped manure

solids

9.9 pounds per

ton

6.2 pounds per

ton

8.7 pounds per

tonLiquid manureslurry

22.5 pounds per1000 gallons



Manure irrigatedfrom storage pond

137 pounds peracre-inch



Source: Advantages of Manure Solid-Liquid Separation, ANR-1025, Ted W. Tyson, Extension AgriculturalEngineer , Alabama Cooperative Extension System

Manure storage systems allow optimal timing for spreading manure on the land. Manurethat is spread and incorporated directly into the soil preserves a large portion of theavailable plant nutrients, and is most environmentally acceptable to regulators and non-farm neighbors.

In some cases, because of CAFO Nutrient Management requirements, a portion of thenutrients in stored manure must be exported off the farm to avoid excess nutrient build-upin the cropland on the farm. In these cases, the solid component of stored manure that hasbeen separated into solid and liquid components can be utilized in the following ways:

Exported to neighboring farms that dont have excessive nutrient buildup Composted and sold as an organic mulch Composted and dried to use on the farm as bedding

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Manure solids are relatively easy to transport in truck mounted spreaders or large tractorpulled box spreaders. Thus, it is not difficult to export manure solids to neighboring farmsthat can use the nutrients on cropland.

Composted manure solids have become popular as an organic mulch. Often local

nurseries will purchase bulk composted manure solids to add to other mulch materials toenhance the value for consumers. Some dairymen compost manure solids and sell themdirectly to consumers.

There is increased interest in using composted, dried manure solids as dairy livestockbedding material in freestall barns. Since the annual cost of purchased bedding forfreestalls is often very high, and suitable bedding materials are not always available, usingcomposted manure solids can significantly reduce production costs on the farm.


Waste Collection & Treatment Energy Conservation Measures (ECMs)

1. Motor Efficiency When purchasing a replacement or a new motor always considerpremium high efficiency motors. See Energy Efficient Electric Motors section inChapter 9, General Information.

2. Minimize the run time of major motors.

a. Operating time for flush pumpi. number of flushes per day

ii. time per alley flush

b. Operating time for separator pumpi. reduce the volume of flush water pumped over separator

1. reduce overall volume of flush water and wastewater frommilking center, holding area and wash pen

2. increase solids content by recycling flush waterii. Maintain the separator screen so that flow rate (gpm) across screen

can be maintained.

c. Operating time for mixer(s) does the mixer run with the flush pump and/or

with the separator pump?

d. Maintain control systems such as float switches, liquid level probes, timeclocks & timers

3. Select efficient pumps: See Understanding Pump Curves section in Chapter 9,General Information. Do not substitute a larger electric motor for an efficient pump.


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Glossary of Waste Collection & Treatment Terms

Aerobic decomposition: Reduction of the net energy level of organic matter by aerobicmicroorganisms or bacteria that require free elemental oxygen for their growth.

Aerators: A device that brings about aeration of liquid manure for the

purpose of agitation and/or acceleration aerobic decomposition. A surface aerator ismounted on floats in the storage structure and may be powered by electric, hydraulic orwind-assisted motor.

Anaerobic digestion: Conversion of organic matter in the absence of oxygen undercontrolled conditions to gases such as methane and carbon dioxide.

Centrifugal manuretransfer pump: Pump that moves manure by pressure generatedthrough a rotary centrifugal impeller and housing. Pumps are classified by their mechanicalconfiguration (vertical, horizontal, submersible) and power source (commonly electric ortractor PTO).

Flush: Hydraulic removal of liquid, semi-solid or solid material with the addition of dilutionwater.

Flush Alleys: Flush alleys with 2-5% slopes and 10" curbs are typical.

Flush Tanks: Flush tank types include tip/rollover tanks, siphon tanks and cylindricalwater tower tanks (typically 20 to 25 ft. tall to provide pressure and storage volume).

Flush valves: Pipeline/valve systems typically use water towers with large pipes (12"diameter typical) and fast opening valves (butterfly, pop-up, pneumatic, etc.) to release

water in the flush alley.

Lagoon: Pond for processing liquid waste involving some degree of biological treatmentor degradation.

Liquid Manure: Livestock manure with liquid content high enough that the mixture willflow and pump relatively easily. Solid content is usually less than about 13%.

Manure Separators: A device or structure that brings about partial separation of solidmaterial from a liquid or slurry. The objective is to separate manure into solid and liquidfractions. Description of common types follows:

Belt Press: A roller and belt device whereby two concentric running belts are used tosqueeze the manure as it is deposited between the belts. The belts pass over a seriesof spring-loaded rollers where liquids are squeezed out or through the belt andremaining solids are scraped off at a belt separation point.

Centrifugal Separator: A rotating device that uses centrifugal force to remove manureliquids from solids.

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Roller Press: One or more sets of parallel rollers between which manure passes. Theupper roller is solid and may be of a compressible material. It acts to press liquidsthrough openings in the lower perforated roller.

Screw Press: A straight or tapered screw of fixed or varying pitch contained in aperforated or slotted cylinder. Liquids pass through the screen as the manure is

conveyed along the cylinder, while solids are retained with the cylinder and aredischarged out the end.

Static inclined screen: A screen, mounted on an incline, over which manure passes asit off the end of the screen.

Milking center wastes: The wastewater containing milk residues, detergents,disinfectants and in some cases manure that is generated in a milking center.May include wastes from milking equipment washing, milk house and milking parlor.

Pipes: Polyethylene or PVC pipe is recommended for recycling lagoon water. Fewer

crystallization problems seem to occur with plastic than metal components.

Receiving gutters: Collect flush water/manure at the end of the flushed surface (alley,holding area, etc.) Open channel receiving gutters may transport flush to reception pond forseparation. Gutters should be designed with capacity to receive and transport flush waterwith sufficient velocity to prevent settling (deposition).

Recycle Pumps: Pumps commonly used include submersible, wet and dry wellcentrifugal sewage pumps, recirculators and floating pumps.

Settling Basin: (Pond): An earthen storage structure that allows heavier particles to settleto the bottom while allowing the liquid fraction to be removed mechanically or by gravity.

Water supply: The usual flush water supply/storage is an anaerobic lagoon. The farm-water system provides for freshwater flushing in the parlor and wash pen water, whichcan then be used for flushing.


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Waste Collection & Treatment Web Page References

Waste Handling Equipment Manufacturers

Agpro Inc. www.agprousa.com

Albers Dairy Equipment www.albersdairyequipment.com

Accent Manufacturing Inc - www.accentmanufacturing.com

Bauer Slurry Technology www.bauer-at.com

FAN Engineering manure separator www.fan-separator.de

Fisher Pumps manure pumps and mixers www.fisherpumps.com

Flygt manure pumps www.flygtus.com

Global EnviroSystems manure separator www.grn.com/equip Houle manure equipment - www.jhoule.com

Integrity System - separator, aerator, land applicator - http://www.nutrientcontrol.com/

Mclanahan Corp. Sand Laden Manure separator www.mclanahan.com

Loewen Welding Vacuum scrape www.loewenwelding.com

Patz Sales pumps, separator, aerator, land applicator - http://www.patzsales.com/

Press Technology manure separators www.presstechnology.com

US Farm Systems - www.usfarmsystems.com

Vincent Corp manure separator www.vincentcorp.com

Vaughan Co., Inc. (Manure pumps) http://www.chopperpumps.com/

Other References

Flushing Systems for Dairies, Charles D Fulhage and Donald L. Pfost

Department of Agricultural Engineering, University of Missouri-ColumbiaWQ0308 fact sheet http://muextension.missouri.edu/explore/envqual/wq0308.htm
http://www.agprousa.com/http://www.albersdairyequipment.com/http://www.accentmanufacturing.com/http://www.bauer-at.com/http://www.fan-separator.de/http://www.fisherpumps.com/http://www.flygtus.com/http://www.grn.com/equiphttp://www.jhoule.com/http://www.nutrientcontrol.com/http://www.mclanahan.com/http://www.loewenwelding.com/http://www.patzsales.com/http://www.presstechnology.com/http://www.usfarmsystems.com/http://www.vincentcorp.com/http://www.chopperpumps.com/http://muextension.missouri.edu/explore/envqual/wq0308.htmhttp://muextension.missouri.edu/explore/envqual/wq0308.htmhttp://muextension.missouri.edu/explore/envqual/wq0308.htmhttp://www.chopperpumps.com/http://www.vincentcorp.com/http://www.usfarmsystems.com/http://www.presstechnology.com/http://www.patzsales.com/http://www.loewenwelding.com/http://www.mclanahan.com/http://www.nutrientcontrol.com/http://www.jhoule.com/http://www.grn.com/equiphttp://www.flygtus.com/http://www.fisherpumps.com/http://www.fan-separator.de/http://www.bauer-at.com/http://www.accentmanufacturing.com/http://www.albersdairyequipment.com/http://www.agprousa.com/

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8 Waste Collection Treatment