Dairy Day 1997 FLUSHING MANURE SYSTEMS FOR DAIRY FACILITIES

Flushing systems that collect and transport Daily water requirements for flushing vary manure are utilized in dairy operations. The depending on the width, length, and slope of the sanitation attainable and reduced labor requirearea to be flushed. Computer simulations show ments can make flushing a desirable option. that slope of the building and flush water velocDesigned flush systems utilize a flush device to ity have the greatest impact on cleaning effirelease the correct volume of water at the approciency. Buildings with alleys sloping 2 to 4% priate discharge rate and length of time. This will use significantly less water per day for achieves the designed flow velocity, contact flushing as compared to alleys at a 1% slope (Tatime, and depth of water in the gutter to obtain bles 1, 2, 3). At an optimal slope of 3%, a miniadequate cleaning. mum flush volume is 100 gal per ft of gutter


Introduction
ments ranging from 240 to 620 gal per cow per Flushing dairy manure is an alternative to the larger of two volumes -either 52 gal per cow blade scraping of freestalls or holding pens.It per flush or 1.35 gal per sq ft of alley per flush.offers the advantages of labor reduction with Normally, recycled water from the lagoon is automated systems, limited scraping require-used for flushing the freestalls, and fresh water ments, lower operating cost, drier floors, poten-is used for flushing the milk parlor and holding tial reduction in odor and cleaner facilities.
pen.However, an optional method of handling the manure is necessary in colder weather, and The cleaning efficiency of a flush system scraping may be required.Other disadvantages depends on the energy of flush water to remove include the water requirements per cow and the the manure away from the alleys or pens.Most initial fixed cost.A flush system consist of three data available are from observation of installed areas: a high volume flush mechanism, a channel systems rather than optimized design through for directional control of the flush water, and the computer simulations.Present design procecollection of flush water for separation of the dures suggest that the flushing wave needs to be liquid and solid.Flushing does not eliminate the 150 ft in length and 3 in deep and moving at a need to apply the manure and effluent to land in velocity of 5 fps.Buildings longer than 450 ft amounts based on crop utilization.
require the flush wave to be at least 1/3 of the width for flushing lengths of less than 150 ft.
study of six dairies found flush water requireday.Another design procedure suggests selecting total length.If the length is less than 150 ft, then the design procedures are based on a 10 sec rather than "en masse" as with the storage struccontact time.The amount of time flush water ture system.moves past a given selection of the alley is known as contact time.Observation indicates The channel for controlling the flushing that a contact time of at least 10 sec improves water is normally the freestall alley or holding cleaning efficiency.Minimum design values are pen.Flushing dairy facilities is different than a flush velocity of 3 fps and a contact time of 5 flushing swine facilities.Flushing channels in sec.
swine buildings range in width from 8 to 12 ft System Components on center.These secondary channels provide Selection of how flush water is released at the length of the building.Swine facilities can the upper end is critical.The two basic methods be flushed year round, because the buildings are for flushing use storage structures and pumps.
warmer.Channels for dairy facilities range from Storage structures have the flush water stored in 8 ft to 14 ft in a freestall and up to 40 ft wide in a tank or tower at the upper end of the area being a holding pen.Secondary channel dividers are flushed.A low hp pump is used to transfer water not used because of vehicle and animal traffic.from the lagoon to the storage tank.Flushing The flush is dependent on the uniformity of the tanks have larger discharge openings and a floor surface.The alley may need scraping in typical depth of 8 to 12 ft.Towers discharge cold weather.Some scraping or manual cleaning through 12-to 24-in diameter pipe and have along the freestall curb also may be needed, depths of 20 ft or more.Types of flush-water because much of the manure is deposited there.storage structures include siphon tanks and Some try to avoid this cleaning by placing a pipe gravity flow tanks or towers.These tanks may along the top of the curb to prevent the manure be either round or square, and towers generally from being deposited against it.Others place a are round.Flushing pumps utilize the lagoon for 3/4 to 1 in crown in the alley to direct more flush storing the flush water.A large hp pump then water along the curbs, if freestalls are along both pumps the water to the upper end when flushing sides.The crown will interfere with scraping is desired.and, generally, the use of level alleys or pens Tables 1, 2, and 3 provide summaries of height is suggested to prevent flush water from volume of water and discharge (release) rate entering the freestall.Holding pens and milk required to meet the recommended design re-parlors may require multiple release valves or quirements for buildings with different slopes, more frequent flushing to obtain adequate cleanlengths, and alley widths of 10, 12, and 14 ft, ing.respectively.The time a valve is open is determined by dividing the volume of water required Water is released into the channels using by the release rate.With storage units, the re-several different methods.The most common lease rate varies from a minimum of 10 sec to method is use of 12-in-diameter "pop-up" or more than 60 sec for longer buildings.Release recessed valves, which open manually or autorates can vary from 1,000 gpm to over 15,000 matically.The valves release the water at the gpm if properly designed.Flush-water pumping center of the alley.The upper 10 to 20 ft of the systems often are limited by the pump capacity, channel may not clean as well as the remainder and the water release rate is 60 sec or longer.
of the channel.Automated valves are pneumati-Most of the pumping systems are limited to a cally operated and require a source of comrelease rate of less than 2,000 gpm.Higher pressed air.Discharge rate from a valve is release volumes require larger hp pumps and influenced by the hydraulic characteristics of the transfer pipes.Flush storage structures use less pipeline feeding the valve.Common design water and depend upon the velocity to move the procedures use multiple tanks to feed the valve material the length of the gutter.Flush pumps from two sides and increase the discharge rate.use higher volumes of water at lower velocities.
Other release methods include a hinged plate, an The material is moved in smaller quantities open pipe, and a gated pipe.The hinged plate is with secondary channel dividers located 3 to 4 ft directional control of the flush water as it moves across the width is recommended.A 10 in curb trough.Water is released into the trough, and the drying area prior to transporting to a field.Table water pressure raises the hinged plate with the 4 shows the weight of manure that has to be flush water being distributed uniformly across hauled to a field at different moisture contents the channel.The hinged plate works well with and herd size.We assumed that the cows prosiphon tanks or other high discharge methods duce 120 lb of manure per day at an initial and with wider channels such as the holding pen.moisture content of 87.3%.The solids portion of An open pipe may be a section of pipe extending the manure will have a moisture content of 60 to out of a tank or an entrance ramp.Normally, 80% upon exiting a mechanical separator.The these are operated manually using a butterfly moisture content of material exiting a gravity value.The flush water is directed toward the settling structure can be above 90%, with the alley, and distribution of the full width is poor at moisture reduction on the dry slab being dependthe upper end.This type of system may require ent on the weather.a steep entrance ramp, which hinders animal and vehicle traffic.The gated pipe developed in Dairies using sand-bedded freestalls need to Missouri has a diameter of 12 to 14 in and noz-have a sand trap located above the mechanical zles or gates projecting from it to provide separator.The abrasive action of the sand on the directional control of the flush water being pumps and screens in mechanical separators released.The pipe is recessed into the floor so decreases the equipment life and increases the that protrusion is limited to 3 to 4 in above the maintenance costs.These increased costs have floor.Vehicle and animal traffic can easily cross resulted in many dairies using gravity settling the gated pipe design.
basins with sand-bedded manure.However, the The flush water is collected at the lower end separator has to be compared to the increased of the building in a gutter and directed towards a cost of transporting higher volumes of material mechanical separator or gravity settling basin.
to the fields.Design parameters for the sand trap The flushed material is separated to allow the have not been determined.Some data suggest solids to accumulate in a structure or basin and that flush water has to be slowed from 5 fps to the liquid to drain to a lagoon.Generally, the 1.5 fps to allow the sand to settle out and the freestall buildings are flushed with recycled effluent and manure to be transferred to the water from the lagoon, and the holding pens and mechanical or gravity separators.milking parlor are flushed with fresh water.The mechanical separator may be a screen, press Conclusions roller, or screw press.A screen allows the liquid to pass through it, but the solids remain on the Flushing can be a viable alternative to scrapsurface and are transferred to a storage area.
ing of dairy manure.Existing facilities can be With a press roller, the flushed material passes constructed for the addition of flushing systems through a pair of rollers and the water drains at a later date, even if scraping is planned for in away.The pressing action is designed to pro-the immediate future.This requires placing the duce a drier material.The third mechanical buildings at a 2 to 3 percent slope.A 6 to 8 ft separator is the screw press, which uses more difference in elevation between the lower end of pressure to separate liquids and solids.Gravity the flushed areas and the lagoon freeboard will type systems use a settling basin to settle out the be necessary for inclusion of separation equipsolids and drain off the liquids.The solids are ment and transfer collection gutters.Inclusion of generally moved to a flushing systems in existing buildings has to be increased operating cost of the mechanical determined on an individual basis.An adequate water supply for fresh water flushing of the milking parlor and holding pen also must be available.

Table 4 . Tons of Manure Produced per Day Based on Different Herd Sizes and the Moisture Content of the Solids*
Assume 120 lb of manure per cow per day at 87.3% moisture. *